Editing Work breakdown structure (section)

== Overview ==
WBS is a hierarchical and incremental decomposition of the project into deliverables (from major ones such as phases to the smallest ones, sometimes known as work packages). It is a [[tree structure]], which shows a subdivision of effort required to achieve an objective, for example, a [[Program management|program]], [[project]], and [[contract]].<ref name="NASA01"/> 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, [[Task (project management)|tasks]], subtasks, and work packages) which include all steps necessary to achieve the objective.

[[Image:NASA NF 533 reporting structure.jpg|thumb|left|300px|Example of work breakdown structure applied in a NASA reporting structure<ref name="NASA01">NASA (2001). NASA NPR 9501.2D. May 23, 2001.</ref>]]

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.<ref name="NASA01"/>

A work breakdown structure permits the summing of subordinate costs for tasks, materials, etc., into their successively higher level "parent" tasks, materials, etc. For each element of the work breakdown structure, a description of the task to be performed is generated.<ref>Electronic Industries Alliance Standard ''Systems Engineering Capability Model'' EIA-731.1</ref> This technique (sometimes called a ''system breakdown structure''<ref>Institute of Electrical and Electronics Engineers ''Standard for Application and Management of the Systems Engineering Process'' IEEE Std 1220-2005</ref>) is used to define and organize the total [[Scope (project management)|scope]] of a [[project]].

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). 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. A well-designed WBS makes it easy to assign each project activity to one and only one terminal element of the WBS. 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.
The WBS may be displayed horizontally in [[Outline (list)|outline]] form or vertically as a tree structure (like an organization chart).<ref>{{Cite web |title=How To Use Work Breakdown Structure As A Project Management Tool |url=https://www.nasdaq.com/articles/how-to-use-work-breakdown-structure-as-a-project-management-tool}}</ref>

The development of the WBS normally occurs at the start of a project and precedes detailed project and task planning. Through {{vanchor|Progressive elaboration}}, an iterative  process in [[project management]] knowledge, the details of [[project management plan]] and amount of information will increase,<ref>{{cite book |title=A guide to project management body of knowledge |date=2017 |publisher=Project Management Institute, Inc. |isbn=978-1-62825-184-5 |pages=715 |edition=Sixth}}</ref> and initial estimates of items such as project scope description, planning, budget, etc. will become more accurate.<ref>{{cite book |last1=Rita |first1=Mulcahy |title=PMP Exam prep |date=2018 |publisher=RMC publications |isbn=978-1-943704-04-0 |page=88 |edition=Ninth}}</ref> It also helps the [[project team]] to make the project plan with more details.<ref>{{cite web |title=Community Guide of the PMI-ACP Adaptive Planning |url=https://www.projectmanagement.com/wikis/295452/Progressive-Elaboration}}</ref>

===Types===
PMI's Practice Standard for Work Breakdown Structures identifies two major types of work breakdown structures.

====[[Deliverable]]-oriented WBS====

Deliverable-oriented WBS, also known as [[Product breakdown structure]] uses key deliverables to group each work in the project.

====Phase-oriented WBS====
Phase-oriented WBS groups the work under key phases or stages of project lifecycle.