View source for Work Break-down Structure

== Big ideas ==
=== Definition ===
Work breakdown structure (WBS) is an effective tool in project management and systems engineering which considers deliverables as the key elements of a structure. The structure decomposes the project into different levels and each lower level defines a more detailed project work.  The department and staff are divided into groups according to the work packages in WBS.<ref name="three"> ''Glossary of Defense Acquisition Acronyms and Terms: Contract Work Breakdown Structure (CWBS). Defense Acquisition University. Retrieved 19 September 2017.'' </ref>

WBS consist of three key elements. Work is the task that can produce tangible results; breakdown is the hierarchical structure of gradual subdivision and classification; the structure is to organize each part according to a certain pattern.

=== History ===
In 1957, the U.S. Navy’s Fleet Ballistic Missile Program occurred a heavy schedule delay. The team tried to solve the problem and developed a form to define tasks and organize activities needed for a project on the basis of deliverables, which became known as PERT (program evaluation and review technique).

Subsequently, the Department of Defense (DOD) and NASA published the first definition of the work breakdown structure process in 1962, then the first official reference in 1968. The Work Breakdown Structures for Defense Materiel Items (MIL-STD-881) became a standard across the DOD, with templates released for specific military applications.

In 1987, the Project Management Institute introduced the work breakdown structures as standard practice to non-military applications. Then the term “work breakdown structure” was officially documented in 1993 for applications in business firms and other organizational projects.

In June 1999, the PMI Standards Program developed the Work Breakdown Structure (WBS) Practice Standard which summarizes the planning process into three critical steps, scope planning, scope definition, and work breakdown structure development.

=== Content of WBS ===
WBS should include project products, project organization, and division of project schedule. The structure focus on the work packages of the project which is the deliverables. The accomplishment of the project is based on the coordination and arrangement of all work packages. Therefore, the work packages that are not included in the WBS do not belong to the scope of the project. 

==== WBS dictionary ====
For WBS, it is necessary to establish a WBS dictionary to describe each work part. WBS dictionary usually includes information such as work package description, schedule date, cost budget, and personnel allocation. The main application of the WBS dictionary is to define the work in detail to help create the product that will be obtained with the execution of the project. Work Packages represent the list of tasks in order to produce the particular unit of work. When WBS and OBS are used together, a coding system should be established. The coding scheme is the coding system used to uniquely determine each unit of the project work breakdown structure. Costs and resources are allocated to this coding structure. Used correctly, the WBS Dictionary becomes much more than a document that describes the work. It becomes a project kaleidoscope that allows you to look at your project data in an infinite number of ways.

[[File:WBS_dictionary.PNG‎ |thumb|center|400px|Figure 1: A example of WBS dictionary <ref name="one"></ref>]]

==== WBS elements ====
In fact, WBS elements are "nodes" in WBS structure. From the form of expression, they are "boxes" in "organizational chart". These boxes represent independent deliverables with the subordinate or superior relationship. After decades of development, most organizations prefer that the WBS structure be necessarily related to the project objectives and must be oriented to the final product or deliverables, so the WBS element is more suitable to describe the composition of the output product.<ref name="four"> ''Effective Work Breakdown Structures. Gregory T. Haugan. Management Concepts Press 2001.'' </ref>
It is obvious that different organizations and cultures use different methods, procedures and resources to complete the same structure work, but their destination must be the same and meet the specified requirements. On the one hand, by considering every WBS element as a unique deliverable can we control and manage the project most effectively. On the other hand, only by identifying the deliverables can we clarify the methods, procedures and resources used by internal or external organizations to complete the work. The lowest level of element in WBS is called work packages.

==== Work packages ====
Work package is a unit of work required to fulfill a specific request. Work packages explicitly express the activity that need to be performed corresponding to the specific work, as well as the start and finish dates of the activity.
It is the basis of all project work, and also suitable for a status report. The formats include work package assignment table and work package description report. The basic requirement of establishing work package is to provide sufficient and appropriate management information for project control.
Work package is the lowest level project deliverable of WBS, which has the following characteristics:

*Work packages can be assigned to another project manager for planning and execution.
*The work package can be further decomposed into the WBS elements of the subprojects.
*Work package can be further decomposed into activities when making project schedule.
*The work package may be the responsibility of a single department or contractor. When used for subcontracting outside the organization, it is called the commitment package.
*The definition of work package should consider an 80-hour rule or two-week rule which means the completion time of any work package should not exceed 80 hours. At the end of each 80 hours or less, only the accomplishment of the work package is reported. Through this method of regular inspection, the adjustment of the project could be controlled. 


=== Structure type ===
*Summary WBS

The outline work breakdown structure is a guiding and strategic work breakdown structure. There are only three levels in the decomposition structure

Level 1: the whole system refers to defense equipment projects, such as aircraft system, electronic system, missile system, ordnance system, space system and ground vehicle system.

Level 2: major units of defense equipment projects, such as aircraft, ships, system experiments and data.

Level 3: units subordinate to level 2, such as airframe, propulsion plant, information, service and technical publications.

*Contract WBS
Contract work breakdown structure is a work breakdown structure applicable to specific contract or procurement activities. CWBS summarizes the tasks of the project, determines the relationship among these tasks, the organizational structure and the technical status of the project. It also clarifies the logical constraint framework for the relationship between the performance, technical objectives, progress and cost of the project. The work breakdown structure of the contract shall be consistent with the levels specified in the contract. The contract should indicate at which level of the contract the cost is accumulated. Then the contractor shall have the ability to trace the accumulated cost by extending the level of contract WBS.
[[File:WBS_template.PNG‎ |thumb|center|650px|Figure 2: A template of WBS <ref name="two"></ref>]]

=== Main uses ===
WBS has four main uses: 
#WBS is a planning and design tool to describe ideas. It helps project managers and project teams to identify and effectively manage project work.
#WBS is a structure design tool that can clearly show the relationship between the work of each project.
#WBS is a planning tool that shows the whole picture of the project and specifies the work that must be done to complete the project.
#WBS defines milestone events, which can report project completion status to senior management and customers as a reporting tool for project status.

WBS is a group of project elements oriented to project deliverables. These elements define and organize the overall scope of work of the project, and the work not included in WBS does not belong to the scope of the project. Each subordinate of WBS represents a more detailed definition and description of project work.

Prevent missing project deliverables. Help project managers focus on project objectives and clarify responsibilities. Establish visual project deliverables to estimate workload and allocate work. Help improve the accuracy of time, cost and resource estimates. Help build a project team and get a commitment from project staff. Define a benchmark for performance measurement and project control. Clear responsibilities to assist communication. Establish a framework for other project planning. Help analyze the initial risks of the project.