In 1968, the DoD issued "Work Breakdown Structures for Defense Materiel Items" (MIL-STD-881), a military standard requiring the use of work breakdown structures across the DoD. This guide was endorsed by the Secretary of Defense for adoption by all services. īy June 1962, DoD, NASA, and the aerospace industry published a document for the PERT/COST system, which described the WBS approach. While the term "work breakdown structure" was not used, this first implementation of PERT did organize the tasks into product-oriented categories. Navy in 1957 to support the development of its Polaris missile program. The concept of work breakdown structure was developed with the Program Evaluation and Review Technique (PERT) by the United States Department of Defense (DoD). The development of the WBS normally occurs at the start of a project and precedes detailed project and task planning. The WBS may be displayed horizontally in outline form or vertically as a tree structure (like an organization chart). In addition to its function in cost accounting, the WBS also helps map requirements from one level of system specification to another, for example, a cross-reference matrix mapping functional requirements to high level or low-level design documents. A well-designed WBS makes it easy to assign each project activity to one and only one terminal element of the WBS. Since the planned outcomes are the desired ends of the project, they form a relatively stable set of categories in which the costs of the planned actions needed to achieve them can be collected. The WBS is organized around the primary products of the project (or planned outcomes) instead of the work needed to produce the products (planned actions). This technique (sometimes called a system breakdown structure ) is used to define and organize the total scope of a project. For each element of the work breakdown structure, a description of the task to be performed is generated. Ī work breakdown structure permits the summing of subordinate costs for tasks, materials, etc., into their successively higher level "parent" tasks, materials, etc. ![]() ![]() The work breakdown structure provides a common framework for the natural development of the overall planning and control of a contract and is the basis for dividing work into definable increments from which the statement of work can be developed and technical, schedule, cost, and labor hour reporting can be established. In a project or contract, the WBS is developed by starting with the end objective and successively subdividing it into manageable components in terms of size, duration, and responsibility (e.g., systems, subsystems, components, tasks, subtasks, and work packages) which include all steps necessary to achieve the objective.Įxample of work breakdown structure applied in a NASA reporting structure : 145 It is a tree structure, which shows a subdivision of effort required to achieve an objective, for example, a program, project, and contract. WBS is a hierarchical and incremental decomposition of the project into phases, deliverables, and work packages. A WBS also provides the necessary framework for detailed cost estimation and control while providing guidance for schedule development and control. : 434 : 116 The Project Management Body of Knowledge (PMBOK 5) defines the work-breakdown structure as a "hierarchical decomposition of the total scope of work to be carried out by the project team to accomplish the project objectives and create the required deliverables." : 434Ī work-breakdown structure element may be a product, data, service, or any combination of these. : 650 A work breakdown structure is a key project deliverable that organizes the team's work into manageable sections. A deliverable-orientated breakdown of a project into smaller components.Ī work-breakdown structure ( WBS) in project management and systems engineering is a deliverable-oriented breakdown of a project into smaller components.
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