DTU ProjectLab - User contributions [en-gb]

Critical Chain Project Management

2014-12-01T22:58:43Z

Cruijff: /* Discussion */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1 - Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory of Constraints is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

A constraint in the system is a part that constrains the overall objetive of that system. A typical example is bottlenecks commonly found in production systems.<ref name=GKRand/>

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

{|style="margin: 0 auto;"
| [[File:CritChain_Industry_Increase.png|300px|upright|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]]
| [[File:CritChain_Industry_Decrease.png|300px|upright|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]
|}

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref> Others have found that CCPM offers discipline to the project management role and is well fitting for individual projects, but fail to add substantial value to portfolios of projects.<ref name=Steyn1/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:58:19Z

Cruijff: /* Discussion */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1 - Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory of Constraints is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

A constraint in the system is a part that constrains the overall objetive of that system. A typical example is bottlenecks commonly found in production systems.<ref name=GKRand/>

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

{|style="margin: 0 auto;"
| [[File:CritChain_Industry_Increase.png|300px|upright|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]]
| [[File:CritChain_Industry_Decrease.png|300px|upright|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]
|}

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref> Others have found that CCPM offers discipline to project management role and is well fitting for individual projects, but fail to add substantial value to portfolios of projects.<ref name=Steyn1/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:52:41Z

Cruijff: /* Theory of Constraints */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1 - Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory of Constraints is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

A constraint in the system is a part that constrains the overall objetive of that system. A typical example is bottlenecks commonly found in production systems.<ref name=GKRand/>

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

{|style="margin: 0 auto;"
| [[File:CritChain_Industry_Increase.png|300px|upright|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]]
| [[File:CritChain_Industry_Decrease.png|300px|upright|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]
|}

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:38:06Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1 - Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory of Constraints is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

{|style="margin: 0 auto;"
| [[File:CritChain_Industry_Increase.png|300px|upright|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]]
| [[File:CritChain_Industry_Decrease.png|300px|upright|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]
|}

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:33:14Z

Cruijff: /* History */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1 - Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory of Constraints is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

{|style="margin: 0 auto;"
| [[File:CritChain_Industry_Increase.png|300px|upright|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]]
| [[File:CritChain_Industry_Decrease.png|300px|upright|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]
|}

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:32:36Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1 - Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

{|style="margin: 0 auto;"
| [[File:CritChain_Industry_Increase.png|300px|upright|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]]
| [[File:CritChain_Industry_Decrease.png|300px|upright|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]
|}

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

File:CritChain Industry Increase.png

2014-12-01T22:31:34Z

Cruijff: Cruijff uploaded a new version of "File:CritChain Industry Increase.png"

File:CritChain Industry Decrease.png

2014-12-01T22:31:18Z

Cruijff: Cruijff uploaded a new version of "File:CritChain Industry Decrease.png"

Critical Chain Project Management

2014-12-01T22:28:31Z

Cruijff: /* Theory of Constraints */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

{|style="margin: 0 auto;"
| [[File:CritChain_Industry_Increase.png|300px|upright|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]]
| [[File:CritChain_Industry_Decrease.png|300px|upright|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]
|}

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:26:20Z

Cruijff: /* Theory of Constraints */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

[[File:CritChain_Industry_Increase.png|300px|left|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]] [[File:CritChain_Industry_Decrease.png|300px|right|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:24:19Z

Cruijff: /* Theory of Constraints */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

[[File:CritChain_Industry_Increase.png|300px|center|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]] [[File:CritChain_Industry_Decrease.png|300px|center|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:24:08Z

Cruijff: /* Theory of Constraints */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

[[File:CritChain_Industry_Increase.png|300px|center|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]]
[[File:CritChain_Industry_Decrease.png|300px|center|thumb| Figure 3 - Reported changes in operational and financial performance, resulting from the application of TOC. (Less is better) <ref name=Hallmark/>]]

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:23:37Z

Cruijff: /* Theory of Constraints */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

[[File:CritChain_Industry_Increase.png|300px|center|thumb| Figure 2 - Reported changes in operational and financial performance, resulting from the application of TOC. (More is better) <ref name=Hallmark/>]]

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T22:21:37Z

Cruijff: /* Theory of Constraints */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

[[File:CritChain_Industry_Increase.png|400px|thumb| Figure 2 - Hej <ref name=Hallmark/>]]

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

File:CritChain Industry Increase.png

2014-12-01T22:19:52Z

Cruijff:

File:CritChain Industry Decrease.png

2014-12-01T22:19:38Z

Cruijff:

Critical Chain Project Management

2014-12-01T22:17:47Z

Cruijff: /* History */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

The benefits of applying TOC varies from project to project. A review of the use in the industry show a clear positive effect for the companies involved. The results of 82 companies, ranging in size and industry, were aggregated and analysed. The results are shown in figure 2 and 3. Lead-Times, Cycle-Times and Inventory Levels were reduced by respectively 70%, 65% and 49%. Meanwhile were Due-Date-Performance, Revenue/Throughput and the Combined Financial Variable increased by respectively 44%, 63% and 76%.<ref name=Hallmark> ''Mabin, Victoria, J., and Steven J. Balderstone. The World of the Theory of Constraints: A Review of the International Literature. Boca Raton, FL: St. Lucie Press, 2000.'' </ref> The conclusion in this review was clear recommendation of TOC principles even applied to various degrees. Over 100 cases showed no failures or disappointing results.<ref name=Hallmark/>

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T21:47:27Z

Cruijff: /* Discussion */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other arguments, the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T21:43:45Z

Cruijff: /* Discussion */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/> A direct critical review of the main critical article pointed out amongst other points the statistics mentioned earlier from the "hallmark of TOC literature"<ref name=Hallmark/>.<ref name=Review> “http://public.wsu.edu/~engrmgmt/holt/em530/ButtonEM540ResearchPaper.pdf”. </ref>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T21:38:35Z

Cruijff: /* Discussion */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

The criticism, published in the Project Management Journal<ref name=CriticalLook/>, entered the sphere along with other articles pointing out the same flaws/concerns about CCPM. Other articles focused on a balanced discussion of merits and pitfalls<ref name=Merits/>, while some focused on the proposed novelty of the methodology.<ref name=Paradigm’> ''Lechler, Thomas G., Boaz Ronen, and Edward A. Stohr. "Critical chain: a new project management paradigm or old wine in new bottles?." Engineering Management Journal 17.4 (2005): 45.’’ </ref> <ref name=Steyn1/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T21:15:30Z

Cruijff: /* Theory of Constraints */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

=== Theory of Constraints ===
Theory of Constraints, noted TOC in the article, is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T21:15:01Z

Cruijff: /* Monitoring */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

=== Theory of Constraints ===
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.<ref name=Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T21:14:24Z

Cruijff: /* Execution */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

=== Theory of Constraints ===
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by having a physical baton to signal critical chain work is currently being performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T21:13:12Z

Cruijff: /* Concept */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

=== Theory of Constraints ===
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is a default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T21:12:46Z

Cruijff: /* Concept */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

=== Theory of Constraints ===
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal (shortest) critical path/chain. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.<ref name=CriticalLook/>
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T21:09:31Z

Cruijff: /* History */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand /> The theory is outlined in the following segment.

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

=== Theory of Constraints ===
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T20:36:36Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Figure 1: Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T20:36:24Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule. A simplified comparison between traditional project management planning and Critical Chain Project Management is shown in figure 1.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T19:35:03Z

Cruijff: /* Monitoring */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand/> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T19:34:45Z

Cruijff: /* Monitoring */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook/>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook/>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits/> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook/>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook/> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook/>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T19:34:10Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers. <ref name=Merits/>

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.<ref name=Goldratt/>

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.<ref name=Merits/>

An alternative method for estimating duration over the project is by using probability-based quantification using for example Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.<ref name=Monte> ''Robert, Christian P., and George Casella. Monte Carlo statistical methods. Springer, 1999. '' </ref>

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.<ref name=Goldratt/>

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline. Planning task duration at 50% probability gives an intrinsic pressure on resources to finish critical chain tasks as quickly as possible. <ref name=Goldratt/><ref name=Steyn1/>

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course.<ref name=GKRand> Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.Goldratt/>

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management.<ref name=Steyn1/> At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.<ref name=CriticalLook>

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.<ref name=CriticalLook>

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project.<ref name=Merits> This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.<ref name=CriticalLook>

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned.<ref name=CriticalLook> This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.<ref name=CriticalLook>

= References =

<References/>

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T19:25:42Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule.<ref name=CriticalLook> ''Raz, Tzvi, R. Barnes, and D. Dvir. "A Critical Look At Critical Chain Project Management.” Project Management Journal 34.4 (2004): 24-32. '' </ref>]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T19:23:27Z

Cruijff: /* Concept */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1/>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T19:23:14Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

When the critical chain methodology is applied in project management, the critical chain is the sequence of both resource-dependent and pre-exisitent elements that prevents a project from being completed in a shorter time under the condition of finite resources. If resources are accessable in infinite quantities at any given time, the project’s critical chain is identical to its critical path.<ref name=Steyn1>

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:<ref name=Merits> ''Herroelen, Willy, and Roel Leus. "On the merits and pitfalls of critical chain scheduling." Journal of operations management 19.5 (2001): 559-577.'' </ref>

# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management creates a flexible plan by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.<ref name=Merits/>

Critical Chain Project Management make use of buffer management instead of for example earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (the critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.<ref name=Event> ‘’Virine, Lev, and Trumper, Michael. “Event Chain Methodology In Details.” Project Decisions.'' </ref>

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T18:56:58Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. The critical chain technique is the realizing component to the theoretical TOC.<ref name=‘Steyn1> ''Steyn, Herman. "An investigation into the fundamentals of critical chain project scheduling." International Journal of Project Management 19.6 (2001): 363-369.'' </ref> The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.<ref name=Harvey> ''Maylor, Harvey. "Beyond the Gantt chart:: Project management moving on." European Management Journal 19.1 (2001): 92-100.'' </ref>

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T18:44:57Z

Cruijff: /* History */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods based on the principles of the Theory of Constraints.<ref name=GKRand />

Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

?????
It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is an outline for project management based on the same principles. The Theory of Constraints is typically applied through five steps:<ref name=GKRand/>

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T18:39:09Z

Cruijff: /* History */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods obtained from the Theory of Constraints.<ref name=GKRand />

The use of Critical Chain Project Management has been acknowledged with making projects 10 to 50 % faster and/or cheaper than traditional methods such as GANTT, CPM, PERT etc., which were developed and popularised from 1910 to around 1950. Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods.<ref name=GKRand/>

According to studies of traditional project management methods by Standish Group and others, only 44% of projects typically finish on time. Projects are on average completed in 2.2 times the duration that was planned originally and 1.9 times of the budgeted cost. In general 70 % of projects are incapable of meeting the planned scope i.e. technical content delivered. 30 % are even cancelled before completion. It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is a outline for project management based in the same principles. The Theory of Constraints is typically applied through five steps: [3]

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T18:38:23Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=GKRand> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=Goldratt> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods obtained from the Theory of Constraints.<ref name=GKRand />

The use of Critical Chain Project Management has been acknowledged with making projects 10 to 50 % faster and/or cheaper than traditional methods such as GANTT, CPM, PERT etc., which were developed and popularised from 1910 to around 1950. Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods. [3]

According to studies of traditional project management methods by Standish Group and others, only 44% of projects typically finish on time. Projects are on average completed in 2.2 times the duration that was planned originally and 1.9 times of the budgeted cost. In general 70 % of projects are incapable of meeting the planned scope i.e. technical content delivered. 30 % are even cancelled before completion. It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is a outline for project management based in the same principles. The Theory of Constraints is typically applied through five steps: [3]

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T18:37:41Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=''GKRand''> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=‘’Goldratt’’> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods obtained from the Theory of Constraints.<ref name=GKRand />

The use of Critical Chain Project Management has been acknowledged with making projects 10 to 50 % faster and/or cheaper than traditional methods such as GANTT, CPM, PERT etc., which were developed and popularised from 1910 to around 1950. Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods. [3]

According to studies of traditional project management methods by Standish Group and others, only 44% of projects typically finish on time. Projects are on average completed in 2.2 times the duration that was planned originally and 1.9 times of the budgeted cost. In general 70 % of projects are incapable of meeting the planned scope i.e. technical content delivered. 30 % are even cancelled before completion. It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is a outline for project management based in the same principles. The Theory of Constraints is typically applied through five steps: [3]

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T18:35:51Z

Cruijff: /* History */

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=''GKRand''> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain.<ref name=‘’Goldratt’’> ''Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.'' </ref> Critical Chain Project Management is facilitated through algorithms and methods obtained from the Theory of Constraints.<ref name=''GKRand'' />

The use of Critical Chain Project Management has been acknowledged with making projects 10 to 50 % faster and/or cheaper than traditional methods such as GANTT, CPM, PERT etc., which were developed and popularised from 1910 to around 1950. Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods. [3]

According to studies of traditional project management methods by Standish Group and others, only 44% of projects typically finish on time. Projects are on average completed in 2.2 times the duration that was planned originally and 1.9 times of the budgeted cost. In general 70 % of projects are incapable of meeting the planned scope i.e. technical content delivered. 30 % are even cancelled before completion. It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is a outline for project management based in the same principles. The Theory of Constraints is typically applied through five steps: [3]

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T18:30:40Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. <ref name=''GKRand''> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref> The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain. Critical Chain Project Management is founded in algorithms and methods obtained from the Theory of Constraints.

The use of Critical Chain Project Management has been acknowledged with making projects 10 to 50 % faster and/or cheaper than traditional methods such as GANTT, CPM, PERT etc., which were developed and popularised from 1910 to around 1950. Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods. [3]

According to studies of traditional project management methods by Standish Group and others, only 44% of projects typically finish on time. Projects are on average completed in 2.2 times the duration that was planned originally and 1.9 times of the budgeted cost. In general 70 % of projects are incapable of meeting the planned scope i.e. technical content delivered. 30 % are even cancelled before completion. It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is a outline for project management based in the same principles. The Theory of Constraints is typically applied through five steps: [3]

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T18:29:11Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

<ref name=''GKRand''> ''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.'' </ref>

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain. Critical Chain Project Management is founded in algorithms and methods obtained from the Theory of Constraints.

The use of Critical Chain Project Management has been acknowledged with making projects 10 to 50 % faster and/or cheaper than traditional methods such as GANTT, CPM, PERT etc., which were developed and popularised from 1910 to around 1950. Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods. [3]

According to studies of traditional project management methods by Standish Group and others, only 44% of projects typically finish on time. Projects are on average completed in 2.2 times the duration that was planned originally and 1.9 times of the budgeted cost. In general 70 % of projects are incapable of meeting the planned scope i.e. technical content delivered. 30 % are even cancelled before completion. It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is a outline for project management based in the same principles. The Theory of Constraints is typically applied through five steps: [3]

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-12-01T18:24:07Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

<ref name=''Rand, Graham K. "Critical chain: the theory of constraints applied to project management." International Journal of Project Management 18.3 (2000): 173-177.''> ''https://www.kth.se/polopoly_fs/1.222013!/Menu/general/column-content/attachment/Article3-Rand.pdf'' </ref>

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain. Critical Chain Project Management is founded in algorithms and methods obtained from the Theory of Constraints.

The use of Critical Chain Project Management has been acknowledged with making projects 10 to 50 % faster and/or cheaper than traditional methods such as GANTT, CPM, PERT etc., which were developed and popularised from 1910 to around 1950. Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods. [3]

According to studies of traditional project management methods by Standish Group and others, only 44% of projects typically finish on time. Projects are on average completed in 2.2 times the duration that was planned originally and 1.9 times of the budgeted cost. In general 70 % of projects are incapable of meeting the planned scope i.e. technical content delivered. 30 % are even cancelled before completion. It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is a outline for project management based in the same principles. The Theory of Constraints is typically applied through five steps: [3]

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =

<References/>



[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-11-30T21:16:36Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain. Critical Chain Project Management is founded in algorithms and methods obtained from the Theory of Constraints.

The use of Critical Chain Project Management has been acknowledged with making projects 10 to 50 % faster and/or cheaper than traditional methods such as GANTT, CPM, PERT etc., which were developed and popularised from 1910 to around 1950. Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods. [3]

According to studies of traditional project management methods by Standish Group and others, only 44% of projects typically finish on time. Projects are on average completed in 2.2 times the duration that was planned originally and 1.9 times of the budgeted cost. In general 70 % of projects are incapable of meeting the planned scope i.e. technical content delivered. 30 % are even cancelled before completion. It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is a outline for project management based in the same principles. The Theory of Constraints is typically applied through five steps: [3]

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Industry experience =

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =



[1] Willy Herroelen, Roel Leus (2001), "On the merits and pitfalls of critical chain scheduling".

[2] Tzvi Raz, Robert Barnes, Dov Dvir (2003) "A Critical Look at Critical Chain Project Management".

[3] Graham K. Rand (2000) "Critical chain: the theory of constraints applied to project management".

[4] Shanlin Yang, Lei Fu (2014) "Critical chain and evidence reasoning applied to multi-project re-schedule in automobile R&D process".

[5] Herman Steyn (2000) "An investigation into the fundamentals of critical chain project scheduling".

[6] Herman Steyn (2002) "Project management applications of theory of constraints beyond critical chain scheduling".

[7] Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Critical Chain Project Management

2014-11-30T16:50:39Z

Cruijff:

[[File:CCPM_figure1.png|thumb|alt=Example alt text|Comparison of conventional Schedule and CCPM Schedule [2]]]
Critical Chain Project Management (CCPM) is a method of managing projects, where the attention is focused on the resources needed to execute various project tasks. In comparison to traditional project management methods that have its origins in critical path and PERT algorithms, where the emphasis is put on the order of tasks and strict schedules. The typical critical chain project network attempt to keep resources levelly loaded, but requires that they are flexible in start times. Additionally a quick switch between tasks and task chains is desirable to make sure the project is on schedule.

= History =
CCPM was developed by Eliyahu M. Goldratt and introduced in 1997 in his book, Critical Chain. Critical Chain Project Management is founded in algorithms and methods obtained from the Theory of Constraints.

The use of Critical Chain Project Management has been acknowledged with making projects 10 to 50 % faster and/or cheaper than traditional methods such as GANTT, CPM, PERT etc., which were developed and popularised from 1910 to around 1950. Proponents of CCPM have attested that the benefits over PERT and/or CRM is that application of the Theory of Constraints focuses on how upper management are handling human behavior while envisioning the project network and in managing it afterwards, in constrast to dealing solely with specific technical aspects as the before mentioned methods. [3]

According to studies of traditional project management methods by Standish Group and others, only 44% of projects typically finish on time. Projects are on average completed in 2.2 times the duration that was planned originally and 1.9 times of the budgeted cost. In general 70 % of projects are incapable of meeting the planned scope i.e. technical content delivered. 30 % are even cancelled before completion. It is against these statistics that CCPM looks to improve the circumstances of project management.

== Theory of Constraints ==
Theory of Constraints is a description of how repetitive production systems, with the factor that every system exhibits a certain constraint and overall system performance can only be enhanced by improving the performance of the particular resource constraining the system. CCPM is a outline for project management based in the same principles. The Theory of Constraints is typically applied through five steps: [3]

# Identify the system's constraint(s).
# Decide how to exploit the system's constraint(s).
# Subordinate everything else to the above decision.
# Elevate the system's constraint(s).
# If, in the previous steps, a constraint has been broken, go back to step 1, and do not allow inertia to cause a system's constraint.

= Concept =
Using traditional project management methods, around 30% of the lost time and/or resources are typically used in wasteful techniques such as bad multitasking, student syndrome, in-box delays and/lack of prioritization.

In project management, the critical chain is the sequence of both precedence- and resource-dependent terminal elements that prevents a project from being completed in a shorter time, given finite resources. If resources are available in unlimited quantities at all times, in that case the project’s critical chain is identical to its critical path.

Critical chain are used as an alternative to critical path analysis. There are four dominant features that differentiate critical chain from critical path. Those four are:

# The use of (implicit) dependencies between resources. These dependencies can often be found by checking the resource requirements, yet they are not included in the project network.
# The inherent lack of quest for an optimal solution. Typically a sufficient solution is the goal. This comes down to firstly, that there is no analytical method that computes the absolute optimal (shortest) critical chain. Secondly, there is an default uncertainty in effect, where estimates are by nature more volatile than the eventual difference between a optimal and near-optimal solution.
# Identification and insertion of buffers; project buffer, feeding buffers and resource buffers.
# The critical chain method monitors project progress and overall status by looking at the consumption rate of buffers rather than single task performance across from the schedule.

Critical Chain Project Management does planning by aggregating the amount of safety time included in separate tasks within the project to buffers. This is done to keep up the due-date performance and avoid wasting the given safety time to circumstances like Parkinson’s Law and inefficiently synchronized integration.

Critical Chain Project Management make use of buffer management instead of earned value management, EVM, to measure the performance of a given project. This is done on the basis that earned value management can give a false picture of the status, because a clear distinction isn’t made between progress on the project constraint (critical chain) and progress on non-constraining factors. In order to determine the size of project or resource buffers, the Event Chain Methodology can be utilized.

== Planning ==
Similarly to the critical path method, the planning phase is initiated by the creation of a project plan or work breakdown structure. The plan is typically designed working backwards from a requested completion date with each task starting as late as possible.

Each task is given a duration. In the implementation of CCPM, through software or other solutions, it is common to designate a best guess duration and a safe guess duration, which is deemed to be highly probable. Another way to implement it is by assigning a fixed percentage to be removed and aggregated into the buffers.

Resources are then given to each task. The plan is resource leveled, i.e. start and finish dates are adjusted based on resource constraints to achieve balance, by utilizing the durations set. The longest sequence of tasks that lead from beginning to the end of the project is identified as the critical chain.

Critical chain project management then applies buffers to monitor project schedule and financial performance. The variance duration between safe and best guess estimates are buffered at the end of the project. In a similar fashion, buffers are collected at the end of each sequence of tasks that feed into the critical chain. Typically the date at the end of the project buffer is used as the delivery date to external stakeholders.

An alternative method for estimating duration over the project is by using probability-based quantification using fx Monte Carlo simulation. In can give a more broaden or in-depth perspective on certain areas of interest depending on the use case.

== Execution ==
Entering the execution phase is possible after the plan is complete. The project network is fixed and the size of the buffers are locked down and used to monitor the project schedule and overall performance and should therefore not be changed during the project.

With little to no slack in the duration of individual tasks, resources are motivated to spend time on the task at hand in order to complete it and then hand it off to the next person. The goal is to mitigate poor multitasking. One initiative is to provide prioritized information to all resources. A relay race works as an analogy. While each component in the project is encouraged to proceed as fast as possible, they should be focused on the current task and finishing it as fast as possible without distractions. The analogy is even realized in some cases by have physical baton being used to signal critical chain work is performed and shouldn’t be interrupted. The result is minimizing the tendency to delay work. This is in contrast to traditional project management where tasks are mainly monitored against deadlines. In Critical Chain Project Management, it is encouraged to proceed as fast as possible, without attention to a given deadline.

Planning task duration at 50% probability, there is an intrinsic pressure on resources to finish critical chain tasks as quickly as possible.

== Monitoring ==
Proponents of Critical Chain Project Management typically deem monitoring as the greatest advantage of using the method. Tasks will inevitably vary in duration from the opening 50% estimate, which in turn removes the reason to force tasks to complete “on time”. Monitoring the buffers created during the planning stage will give a more useful result by utilizing chart or graphs that shows how much the buffer has been used as a function of the project completion. If buffer usage is little to none, the project must be on target. If buffer usage is exceeding the pace of the project, leaving insufficient amounts at the end, corrective actions must be taken to recover or stear the project on right course. Similarly if buffer usage are surely done faster than project progress, ultimately resulting in late completion, relevant measures must be taken.

= Discussion =
Since the introduction of Critical Chain Project Management it has gained in popularity as a novel approach to project management. At the same time it has been met with various degrees of criticism dismissing the approach as hype and proposing that the novelty of CCPM to be in terms of terminology rather than substance.

One of the criticisms is of one of the underlining theories behind CCPM. In the designation of CCPM it is said that task owners will overestimate the duration of the tasks and the eventual actual duration is simply the outcome of the deadline itself. This assumption is said to be unfounded in scientific evidence by the methods opponents. They give the example of a study from 2000 actually showing the opposite patterns, where upwards of 60% of task’s duration were actually less than the estimation. The second point in this criticism is the expectation given to project managers estimation of the safety factor. The point the critics are making is that since no absolute task duration estimation effort exist and if such a method existing it would naturally superseed the effect and be used as its own solution.

Another criticism is about CCPM’s use of buffer in the planning and monitoring phase. Again it is questioned where CCPM is sufficiently based in evidence as no scientific or objective tool for determining the buffer size is provided. One key aspect here is circling around the feeding chain concept. The concept is assuming that the project network consists of parallel paths starting at somewhat the same time and proceeds to merge into each other and eventually leading to the final resolution and outcome of the project. This is presumably well fitting for assembly, construction and integration tasks, where tasks are narrowing towards the final task. A lot of other project however will exhibit a bell curve shape, starting initially with a few main activities, which then divides into multiple streams of tasks, before again merging as the project has intermediate deliverables. These complex flow are not optimally compatible with deriving a feeding chain with accompanying buffer. It will typically result in a schedule which is more or less indistinguishable from a traditional critical path.

The TOC terminology is presenting the constraining resource as the key element to tackle appropriately. However at any given point in time, ideally there could be a multitude of constraining resources which each leads to a different schedule. In addition at different points in time, it will be various resources exhibiting constraining behavior. This would mean conflicting schedule and an overall conflict with the steady state view. It is proposed that steady state isn’t realistic in most project environments, which means that the applicability of CCPM can be questioned. This is also a factor when looking at the approach to multitasking. CCPM is trying to achieve improved performance by limiting each resource to one task. How plausible this is in modern organisations is still undecided and other studies have shown a positive effect of the matrix organisation with up to 3 tasks given to a single resource. There is value in alerting resources to important opportunities for early-start of tasks in the critical chain activities, but the benefits of CCPM are seen more as a supplement rather than a substitute for traditional methods.

= References =



[1] Willy Herroelen, Roel Leus (2001), "On the merits and pitfalls of critical chain scheduling".

[2] Tzvi Raz, Robert Barnes, Dov Dvir (2003) "A Critical Look at Critical Chain Project Management".

[3] Graham K. Rand (2000) "Critical chain: the theory of constraints applied to project management".

[4] Shanlin Yang, Lei Fu (2014) "Critical chain and evidence reasoning applied to multi-project re-schedule in automobile R&D process".

[5] Herman Steyn (2000) "An investigation into the fundamentals of critical chain project scheduling".

[6] Herman Steyn (2002) "Project management applications of theory of constraints beyond critical chain scheduling".

[7] Goldratt, Eliyahu M. Critical chain. Great Barrington, MA: North River Press, 1997.

[[Category: Project Management]] [[Category: Uncertainty]] [[Category: Human Behaviour]]

Talk:Project Portfolio Management Vs. Programme Management

2014-11-25T23:12:03Z

Cruijff:

= Feedback for "Project Portfolio Management Vs. Programme Management" by Dbdhl =

Overall it’s an interesting topic and article. The flow and read thread is great and meaningful. It’s a nice appetizer for going deeper into the subject.

== Formal aspects ==

*In general the language is fine with small spelling errors. I suggest to do (another)
*proof-reading. Decide how you want to spell “program”/”programme”. Both spellings are correct; “program” is American English and “programme” is British English.
*The figures are nice, easy to understand and free of formal errors. I am however concerned about the “Cross-Company Portfolio Management Process Relationships, PMI” figure. Did you create the figure yourself? I suggest to follow-up on this.
*I suggest putting numbers on the figures (in the figure text) so it is easier to refer to them in the text.
*References to the figures should be made in the text.
*References to readings are Wiki-features are used correctly.
*Some parts of the text which are not quotes are written with italic letters and I don’t understand why.
*The article is assumed to be interesting for a practitioner since it lays out the differences between Programme Management and (Project) Portfolio Management.
*It is not clear which one of the four “content categories” the article is written in.
*The article is a bit short. As described above it would be great with a discussion section, summary and a more detailed introduction.
*Links to topics (categories) are missing.
*“Own opinion” is differentiated from statements from literature by the use of references.
*The article seems free of plagiarism.

== Section wise ==

=== Summary ===
*It would be great with a short summary in the beginning of the article to let the reader know what the article is about - including findings.

=== Introduction ===
*The 2,5 lines of text in the beginning of the article are great. Could you write a little more about why it can be difficult to distinct between programme and portfolio management?
*I suggest giving the section the headline “introduction”.
*You write that “Both Project Portfolio Management and Programme Management are mentioned as two common extensions of today´s project management practice." I’m wondering who mentions this? Can you insert a reference or maybe just reformulate it, if it is common knowledge?

=== “Program Management” ===
*I find it a bit difficult to understand the following text: “The distinction between a Project and a Program is given by the benefits which a Program provides over and above those that projects can archive on their own, such as exposure, prioritisation, more efficient use of resources and better alignment with other projects”. I think the idea of describing the difference between a project and a programme is great, so if you could just
*I think it should be explained where the key factors come from e.g. a simple reference.

=== “Project Portfolio Management” ===
*I think it should be explained where the key factors come from e.g. a simple reference.

=== “Interface” ===
*I think the “Interface” section is great because it describes how Programme Management and (Project) Portfolio Management relate to each other. It would be nice with a softer link between the two sections describing Programme Management and (Project) Portfolio Management and the “Interface” section meaning that a discussion of the differences would be great. This could be supported by e.g. a table listing the differences in on certain topics. I suggest making a “discussion” section where you discuss the differences and then have the “interface” section as a sub-section.

=== “Perspective” ===
*I find it difficult to understand the purpose of this section.
*The quote is quite dominating in the section and I think it would be better to make a reference instead. Also, the quote is about “General Project Management approach” which is not the main topic of the article as I understand it.

= Feedback by Cruijff =

tl;dr: A very solid article, encompassing clear relevant information in a structured manner. The core is there. If extra fluff and material engaging the reader is included it would take it up a level.

===Review of content===
* The content of the article is very well structured with a clear tone of voice throughout.

* A discussion of use cases and/or existing examples would be interesting as a reader and would ground the concepts further.

* A final concluding segment, where perhaps methods of portfolio and programme management are compared, could strengthen the overall storytelling of the article.

* The length of the article seems appropriate for the subjects mentioned. The text is sufficiently dense without any unneeded extra material. I imagine though that there are a lot of related subjects that could be relevant to present and/or familiarize the reader with along the way. Methods, tools, theories etc.

* I miss referencing to the figures in the text, linking specific areas of interest to the accompanying figure.

===Review of formal aspects===
* Good choice of figures for each section. Illustrates the concepts precisely and in an easy to understand manner. They look skillfully made, but could be provided in a higher resolution making that evident to the viewer.

* Figure numbers and references would be make the already excellent figures more available for the viewer.

* The article is very well referenced throughout. Relies a bit heavily on direct citations of paragraphs. Could be interesting to have the author reflect on the meaning of these citations, compare them etc. in order to hold the reader's hand along the way.

* I find the written style structured and very informative, which gives the impression of a solid scientific approach. At various points in the article it could be advised to simplify the style, making it easier to read and less "clunky"/"stiff". Engage the reader a bit more, without losing the content delivery out of sight.

* Generel: Programme or Program?
* Intro: Wrap up -> outline
* In section Program Management; Definition: splittet -> split
* In section Program Management; Definition: achive -> achieve
* In section Portfolio Management; Definition: truest? options: best, optimal, most correct
* In section Perspective: perspectivate? option: "put into perspective"

Talk:Project Portfolio Management Vs. Programme Management

2014-11-25T23:11:47Z

Cruijff: /* Feedback by Cruijff */ new section

= Feedback for "Project Portfolio Management Vs. Programme Management" by Dbdhl =

Overall it’s an interesting topic and article. The flow and read thread is great and meaningful. It’s a nice appetizer for going deeper into the subject.

== Formal aspects ==

*In general the language is fine with small spelling errors. I suggest to do (another)
*proof-reading. Decide how you want to spell “program”/”programme”. Both spellings are correct; “program” is American English and “programme” is British English.
*The figures are nice, easy to understand and free of formal errors. I am however concerned about the “Cross-Company Portfolio Management Process Relationships, PMI” figure. Did you create the figure yourself? I suggest to follow-up on this.
*I suggest putting numbers on the figures (in the figure text) so it is easier to refer to them in the text.
*References to the figures should be made in the text.
*References to readings are Wiki-features are used correctly.
*Some parts of the text which are not quotes are written with italic letters and I don’t understand why.
*The article is assumed to be interesting for a practitioner since it lays out the differences between Programme Management and (Project) Portfolio Management.
*It is not clear which one of the four “content categories” the article is written in.
*The article is a bit short. As described above it would be great with a discussion section, summary and a more detailed introduction.
*Links to topics (categories) are missing.
*“Own opinion” is differentiated from statements from literature by the use of references.
*The article seems free of plagiarism.

== Section wise ==

=== Summary ===
*It would be great with a short summary in the beginning of the article to let the reader know what the article is about - including findings.

=== Introduction ===
*The 2,5 lines of text in the beginning of the article are great. Could you write a little more about why it can be difficult to distinct between programme and portfolio management?
*I suggest giving the section the headline “introduction”.
*You write that “Both Project Portfolio Management and Programme Management are mentioned as two common extensions of today´s project management practice." I’m wondering who mentions this? Can you insert a reference or maybe just reformulate it, if it is common knowledge?

=== “Program Management” ===
*I find it a bit difficult to understand the following text: “The distinction between a Project and a Program is given by the benefits which a Program provides over and above those that projects can archive on their own, such as exposure, prioritisation, more efficient use of resources and better alignment with other projects”. I think the idea of describing the difference between a project and a programme is great, so if you could just
*I think it should be explained where the key factors come from e.g. a simple reference.

=== “Project Portfolio Management” ===
*I think it should be explained where the key factors come from e.g. a simple reference.

=== “Interface” ===
*I think the “Interface” section is great because it describes how Programme Management and (Project) Portfolio Management relate to each other. It would be nice with a softer link between the two sections describing Programme Management and (Project) Portfolio Management and the “Interface” section meaning that a discussion of the differences would be great. This could be supported by e.g. a table listing the differences in on certain topics. I suggest making a “discussion” section where you discuss the differences and then have the “interface” section as a sub-section.

=== “Perspective” ===
*I find it difficult to understand the purpose of this section.
*The quote is quite dominating in the section and I think it would be better to make a reference instead. Also, the quote is about “General Project Management approach” which is not the main topic of the article as I understand it.

== Feedback by Cruijff ==

tl;dr: A very solid article, encompassing clear relevant information in a structured manner. The core is there. If extra fluff and material engaging the reader is included it would take it up a level.

===Review of content===
* The content of the article is very well structured with a clear tone of voice throughout.

* A discussion of use cases and/or existing examples would be interesting as a reader and would ground the concepts further.

* A final concluding segment, where perhaps methods of portfolio and programme management are compared, could strengthen the overall storytelling of the article.

* The length of the article seems appropriate for the subjects mentioned. The text is sufficiently dense without any unneeded extra material. I imagine though that there are a lot of related subjects that could be relevant to present and/or familiarize the reader with along the way. Methods, tools, theories etc.

* I miss referencing to the figures in the text, linking specific areas of interest to the accompanying figure.

===Review of formal aspects===
* Good choice of figures for each section. Illustrates the concepts precisely and in an easy to understand manner. They look skillfully made, but could be provided in a higher resolution making that evident to the viewer.

* Figure numbers and references would be make the already excellent figures more available for the viewer.

* The article is very well referenced throughout. Relies a bit heavily on direct citations of paragraphs. Could be interesting to have the author reflect on the meaning of these citations, compare them etc. in order to hold the reader's hand along the way.

* I find the written style structured and very informative, which gives the impression of a solid scientific approach. At various points in the article it could be advised to simplify the style, making it easier to read and less "clunky"/"stiff". Engage the reader a bit more, without losing the content delivery out of sight.

* Generel: Programme or Program?
* Intro: Wrap up -> outline
* In section Program Management; Definition: splittet -> split
* In section Program Management; Definition: achive -> achieve
* In section Portfolio Management; Definition: truest? options: best, optimal, most correct
* In section Perspective: perspectivate? option: "put into perspective"

Talk:Project Portfolio Management Vs. Programme Management

2014-11-25T23:10:01Z

Cruijff:

Talk:Project Portfolio Management Vs. Programme Management

2014-11-25T23:09:08Z

Cruijff: /* Feedback by Cruijff - (Fixed DbDhl :-) ) */ new section

= Feedback for "Project Portfolio Management Vs. Programme Management" by Dbdhl =

Overall it’s an interesting topic and article. The flow and read thread is great and meaningful. It’s a nice appetizer for going deeper into the subject.

== Formal aspects ==

*Decide how you want to spell “program”/”programme”. Both spellings are correct; “program” is American English and “programme” is British English.
*The figures are nice, easy to understand and free of formal errors. I am however concerned about the “Cross-Company Portfolio Management Process Relationships, PMI” figure. Did you create the figure yourself? I suggest to follow-up on this.
*I suggest putting numbers on the figures (in the figure text) so it is easier to refer to them in the text.
*References to the figures should be made in the text.
*References to readings are Wiki-features are used correctly.
*Some parts of the text which are not quotes are written with italic letters and I don’t understand why.
*The article is assumed to be interesting for a practitioner since it lays out the differences between Programme Management and (Project) Portfolio Management.
*It is not clear which one of the four “content categories” the article is written in.
*The article is a bit short. As described above it would be great with a discussion section, summary and a more detailed introduction.
*Links to topics (categories) are missing.
*“Own opinion” is differentiated from statements from literature by the use of references.
*The article seems free of plagiarism.

== Section wise ==

=== Summary ===
*It would be great with a short summary in the beginning of the article to let the reader know what the article is about - including findings.

=== Introduction ===
*The 2,5 lines of text in the beginning of the article are great. Could you write a little more about why it can be difficult to distinct between programme and portfolio management?
*I suggest giving the section the headline “introduction”.
*You write that “Both Project Portfolio Management and Programme Management are mentioned as two common extensions of today´s project management practice." I’m wondering who mentions this? Can you insert a reference or maybe just reformulate it, if it is common knowledge?

=== “Program Management” ===
*I find it a bit difficult to understand the following text: “The distinction between a Project and a Program is given by the benefits which a Program provides over and above those that projects can archive on their own, such as exposure, prioritisation, more efficient use of resources and better alignment with other projects”. I think the idea of describing the difference between a project and a programme is great, so if you could just
*I think it should be explained where the key factors come from e.g. a simple reference.

=== “Project Portfolio Management” ===
*I think it should be explained where the key factors come from e.g. a simple reference.

=== “Interface” ===
*I think the “Interface” section is great because it describes how Programme Management and (Project) Portfolio Management relate to each other. It would be nice with a softer link between the two sections describing Programme Management and (Project) Portfolio Management and the “Interface” section meaning that a discussion of the differences would be great. This could be supported by e.g. a table listing the differences in on certain topics. I suggest making a “discussion” section where you discuss the differences and then have the “interface” section as a sub-section.

=== “Perspective” ===
*I find it difficult to understand the purpose of this section.
*The quote is quite dominating in the section and I think it would be better to make a reference instead. Also, the quote is about “General Project Management approach” which is not the main topic of the article as I understand it.

== Feedback by Cruijff - (Fixed DbDhl :-) ) ==

tl;dr: A very solid article, encompassing clear relevant information in a structured manner. The core is there. If extra fluff and material engaging the reader is included it would take it up a level.

===Review of content===
* The content of the article is very well structured with a clear tone of voice throughout.

* A discussion of use cases and/or existing examples would be interesting as a reader and would ground the concepts further.

* A final concluding segment, where perhaps methods of portfolio and programme management are compared, could strengthen the overall storytelling of the article.

* The length of the article seems appropriate for the subjects mentioned. The text is sufficiently dense without any unneeded extra material. I imagine though that there are a lot of related subjects that could be relevant to present and/or familiarize the reader with along the way. Methods, tools, theories etc.

* I miss referencing to the figures in the text, linking specific areas of interest to the accompanying figure.

===Review of formal aspects===
* Good choice of figures for each section. Illustrates the concepts precisely and in an easy to understand manner. They look skillfully made, but could be provided in a higher resolution making that evident to the viewer.

* Figure numbers and references would be make the already excellent figures more available for the viewer.

* The article is very well referenced throughout. Relies a bit heavily on direct citations of paragraphs. Could be interesting to have the author reflect on the meaning of these citations, compare them etc. in order to hold the reader's hand along the way.

* I find the written style structured and very informative, which gives the impression of a solid scientific approach. At various points in the article it could be advised to simplify the style, making it easier to read and less "clunky"/"stiff". Engage the reader a bit more, without losing the content delivery out of sight.

* Generel: Programme or Program?
* Intro: Wrap up -> outline
* In section Program Management; Definition: splittet -> split
* In section Program Management; Definition: achive -> achieve
* In section Portfolio Management; Definition: truest? options: best, optimal, most correct
* In section Perspective: perspectivate? option: "put into perspective"

Talk:Project Portfolio Management Vs. Programme Management

2014-11-25T23:08:28Z

Cruijff: