Dependency in project management

Developed by Behzad Sanie

Abstract

Dependency in project management means that one activity is depended to another. The purpose of dependency determination is indicating the type of dependency that makes a logical relationships between predecessor and successor activities. Four types of dependency defined as: Finish-to-start (FS), Finish-to-finish (FF), Start-to-start (SS), Start-to-finish (SF). The precedence diagramming method (PDM), as an example of the application of dependency, includes the four types of independencies or logical relationships.

Introduction

In project time managing, defining the sequence of the activities is necessary for documenting and recognising the relationship between each activities. The point is defining a logical sequence between tasks to do and increase efficiency during the project limitations. The sequence activity process includes inputs, tools and techniques, and output. The input will be plan of scheduling management, list of activity, attribution of activity, milestone, scope and definition, environmental factors and organisation assets. The application tools and techniques are precedence diagramming method (PDM), dependency determination and leads & lags. The expected outputs are diagram of project schedule network and update of project documents.

Sequence Activities

Figure 1: Sequence of activities in project time management.

The relationships between the activities of a project can be detected and documented in a process known as Sequence Activities, which are capable of considering the rational sequence of work and all project limitations to achieve the highest efficiency. Minimum a predecessor having a logical relationship of finish-to-start or start-to-start as well as minimum a successor having a logical relationship of finish-to-start or finish-to- finish are required to link every activity and milestone, except for the first and last ones. A realistic and achievable project schedule should be considered in the design of logical relationships, which might be essentially supported using lead or lag time between the activities. In this context, project management software or manual or automated approaches can be beneficial in sequencing.

Inputs required in sequence activities

1. Schedule Management Plan (SMP): The SMP is a pre-project preventive thinking to identify several points, including the scheduling process involved in the project, thus helping the sequence activities.

2. Activity List : The activity list contains a critical pathway and basically a detailed documentation of all schedule activities required and sequenced for a particular project. The sequence activities can be affected by the dependencies and limitations that exist on the path to these activities.

3. Activity Attributes : Activity attributes generally refers to active components associated with an activity, which may be pivotal for sequencing for details like events, predecessors or successor.

4. Milestone List : The milestone list as a project management document may schedule all specific project milestones influencing sequence activities.

5. Project Scope Statement: The project scope statement is a good means to describe the key deliverables of a project, including product properties involved in sequence activities like physical lineament of a project being implemented or the nature of a software project. Other scope statements of project can detail constraints and assumptions associated with sequence activities. Although, these are mostly recorded in the activity list, their accuracy is explored as product scope description.

6. Enterprise Environmental Factors: The success of sequence activities can be depended on either internal or external enterprise environmental factors (EEFs), including government regulations, industry conditions, 
project management information system (PMIS), scheduling tool, or work authorisation system (WAS).

7. Organizational Process Assets : Another factor contributing to the sequence activities is the organizational process assets (OPAs), including project plans of the corporate, formal or informal policies, procedures, processes, scheduling methods to developing logical relationships, and templates required for providing networks of project activities. Sequence activities can benefit from additional descriptive data provided by information related to activity characteristics in templates.

1. Precedence diagramming Method (PDM)

The PDM is a common visual tool to draw a diagram of project schedule network, which depicts graphical rectangles, known as nodes, connected by one or more logical relationships to represent activities in these boxes. A precedence diagram is shown with the aid of activity-on-node (AON) strategy that is applied frequently within project management software. There are four logical relationships or dependencies in the package of PDM, including finish-to-start (FS), finish-to-finish (FF), start-to-start (SS), and start-to-finish (SF), containing a predecessor activity depicted logically prior to a dependent activity of a schedule, and a successor activity as a dependent activity depicted logically after another activity of a schedule.

• In a logical relationship of FS, a successor activity can be advanced when the predecessor activity has finished; for instance, the ceremony of awards (the successor activity) can be advanced when the competition (the predecessor activity) has elapsed.
• In a logical relationship of FF, a successor activity can finish when a predecessor activity has finished; for instance, a document editing (the successor activity) can end when a document writing (the predecessor activity) has finished.
• In a logical relationship of SS, a successor activity can be advanced when a predecessor activity has advanced; for instance, Level concrete (the successor activity) can be advanced when a pour foundation (the predecessor activity) has advanced.
• In a logical relationship of SF, a successor activity can be ended when a predecessor activity begins; for instance, the first shift of security guard (the successor activity) can be ended when the second shift of security guard (the predecessor activity) begins.

The most and the least commonly used logical relationships in the PDM are FS and SF, respectively. However, all of these logical relationships are present in a complete list of the PDM.

2. Dependency determination

The characterizations considered in determining the dependencies included mandatory or discretionary and internal or external properties. Four dual attributes have been defined for the dependencies, consisting of a) mandatory external dependencies, b) mandatory internal dependencies, c) discretionary external dependencies, and d) discretionary internal dependencies.

• Mandatory dependency refers to legal or contractual activities that must be happen inherently in the tasks, mostly including physical limitations. For example, it is mandatory to build a foundation in a construction project to continue to erect the superstructure; or a prototype in an electronics project cannot be tested until it must be produced. Another classification for the mandatory dependencies is hard logic or dependencies. Technical activities may not be placed in mandatory dependencies. Determination of mandatory dependencies in the process of sequence activities is undertaken by the project management team. The program's limitations in the scheduling tool should not be mistaken with mandatory dependencies.
• Discretionary dependencies may be known as preferred logic, preferential logic, or soft logic. The behind principle of discretionary dependency is to understand the best strategies in certain or unusual domains of a project to reach targeted sequence in spite of other satisfactory sequences. It is essential to document all aspects of discretionary dependencies due to the presence of any total float value and limited later scheduling options. The modification or deletion of the discretionary dependencies should be taken while using fast tracking strategies. Determination of discretionary dependencies in the process of sequence activities is undertaken by the project management team.
• External dependencies that are typically out of the control of the project team refer to a relationship between activities of project and out of project. For instance, an external source is required to deliver hardware to test a software project or the initiation of preparing a site in a construction project depends on governmental environmental hearings. Determination of external dependencies in the process of sequence activities is undertaken by the project management team.
• Internal dependencies that are typically under the control of the project team refer to a precedence relationship between project activities. For instance, an internal mandatory dependency can be mentioned to inability of team to test a machine until assembling. Determination of internal dependencies in the process of sequence activities is undertaken by the project management team.

3. Leads and Lags

The time required for starting a successor activity regarding a predecessor activity is called as a lead. For example, scheduling a landscaping in a construction project of office building can begin two weeks before the completion of the scheduled punch list. Lead is often planned as a negative amount for lag in scheduling. The time required for delaying a successor activity regarding a predecessor activity is called as lag. For instance, a technical writing team has a 15-day delay time to edit a draft of a large document after writing, meaning a 15-day lag plus SS relationship (SS+10). Lag can be appeared in diagrams of project schedule network plotted for the relationship between H and I activities in spite of unclear offset relative to a timescale. Determination of the need for a lead or a lag in the dependencies is undertaken by the project management team in the exact process of defining the logical relationship. The schedule logic should not be changed following the use of leads and lags. it is essential to document the activities and corresponding assumptions.

Outputs of sequence activities

1. Project Schedule network diagrams: The logical relationships are graphically drawn called as project schedule network diagram, also referred to as dependencies among the project schedule activities, which is prepared by manual manner or project management software. The diagram can represent full details or summarized activities of the project. A summary narrative can be illustrated with a diagram, can exhibit the used fundamental strategy in sequencing the activities, and can describe any abnormal sequence of activity on the network.

2. Updates of project documents: There are needs to update the project documents, such as activity lists, activity attributes, milestone list and risk register. 


• Only, the project product description should be prepared for a small project.
• Careful thinking is necessary to achieve quality criteria in order to distinguish whether a product is acceptable or not. A way to test quality criteria is to scrutinise the distinction between completed or stopped working on this product.

Product-based planning

Product-based planning is a method for identifying first a product requirements and second all activities, dependencies and necessary resources to deliver that product. (ref) This method has different application such as Project planning, Stage planning and Team planning. The sequence involved in the development of products of the plan will be developed and the identification of their dependencies should be detected and defined, which is possible using a product flow diagram (PFD). The dependencies on any non-project products can be detected through this diagram, thereby providing the required activities and data for other planning approaches like estimating and scheduling.

Some essential items should be considered to draw the PFD:

• The PFD is generated by the Project or Team Manager. However, the people responsible for developing or helping the plan products can be involved rationally.
• When the product breakdown structure (PBS) has been drawn, some planners will decide to generate the PFD along with the PBS.
• There is need for very few symbols in drawing the PFD. It is essential to detect any developed product (for instance, enclosure in a rectangle), and to exhibit any required sequence (for instance, interconnection of rectangles by arrows) in the plan. Moreover, the external products should be clear as any existing or non-project ongoing products (for instance, enclosure in a different shape like ellipse).
• The PFD may be added with a starting point attached from all entry points. Although an exit is always available in the PFD, when many entrances exist, this position indicator prevents any of them from being ignored. The symbol of predecessor is there for all points of entry and is the only symbol in PFD not in PBS.

Detection of activities and dependencies

1. Activities: It is inadequate to merely identify products for scheduling and controlling the objectives. To completely illustrate the workload of a plan, it is necessary to detect all the activities needed to establish or modify any of the planned products. The identification of activities can be achieved through multiple approaches, as follows:

• A separate list of the activities can be provided in spite the use of PFD as the information source
• The required activities can be detected by using the products from the PBS or the work breakdown structure (WBS).

The activities involve management and quality-checking activities, and those required for developing the specialist products or for interacting with external parties like those that a product obtained from an outside source or for transforming external products into targeted ones. It is needed to shield the spread of activities unnecessary for the plan. Things should be kept simple if there is any doubt.

2. Dependencies: It is necessary to identify any internal and external dependencies of activities and products. For example, Activity C cannot start unless activities A and B are completed (as an internal dependency). Dependency of a delivery of a product needed for a project by another project, suggestion of a purchase order by the user and decision-making by the program manager are examples of the external dependencies.

The precedence diagramming method (PDM)

PDM is a tool for programming activities in planning a project. It is a method of constructing a network diagram of the project schedule that uses boxes, called nodes, to represent the activities and connects them with arrows that show the dependencies. PDM, In a network technology project, focuses on the precedence of activities and logical relationships. It is also known as the activity-on-node or AON and used by many project management software packages.

Types of dependencies

Figure 2: Four types of dependency in PDM.

Four types of dependencies or logical relationship are linking predecessor activity and successor activity together in PDM. Predecessor activity comes before successor activity which is logically a depended activity in a schedule planning. Example: collecting data in a software project management is a predecessor activity and analysing the data is a successor activity. An activity must be time bound with a start and end time. This time bounding acquires the four types of dependencies between predecessor and successor which defined below:

• Finish-to-start (FS): A successor activity can start when a predecessor activity has finished. Example: building the walls (successor) in a house cannot start before finish the foundation (predecessor).

• Finish-to-finish (FF): A successor activity can finish when a predecessor activity has finished. Example: Wall construction (predecessor) is required to finish before electrical wiring (successor) inside the walls can finish.

• Start-to-start (SS): A successor activity cannot start if a predecessor activity has not begun. Example:

• Start-to-finish (SF): A successor activity cannot finish if a predecessor activity has not begun. Example:

Dependency determination

Dependencies identify by the following attributes:

• Mandatory dependencies
• Discretionary dependencies
• Internal dependencies
• External dependencies