Work Breakdown Structure (WBS)

Work breakdown structure (WBS) is a technique to decompose the project for the purpose of management and control. It provides the framework for organizing and managing the work. A project may be divided into subprojects. Subprojects are further divided into smaller, more manageable work components (work packages) at the lowest level. The WBS is commonly used at the beginning of a project for defining project scope, organizing Gantt schedules, and estimating costs. It is a functional decomposition of the tasks of the project.

WBS is a definition of a project in terms of its work or a deliverable-oriented grouping of project elements that organizes and defines the total scope of the project. Each descending level represents an increasingly detailed definition of the project's work. The WBS is produced following the development of the scope statement, before the schedule. It is a "bridging" document between the Scope and Schedule. 

Simply, we can say that a Work Breakdown Structure (WBS) is a decomposition of all the work necessary to complete a project. A WBS is arranged in a hierarchy and constructed to allow for clear and logical groupings, either by activities or deliverables. 

Project managers typically will develop a WBS as a precursor to a detailed project schedule.  The WBS should be accompanied by a WBS Dictionary, which lists and defines WBS elements.

WBS Types

Deliverable-oriented WBS: A deliverable-oriented WBS is built around the project’s desired outcomes or deliverables.  This type of WBS would likely include the following characteristics:

-        Level 2 items are the names of all vendor project deliverables that are expected to be required as part of a contract.  Level 2 should also include any agency deliverables tasks. 

-        Level 3 items are key activities required to produce the Level 2 deliverables.

-        Additional levels are used depending upon the magnitude of the deliverables and the level of detail required to reliably estimate cost and schedule.

 

Process-centered WBS: A process-centered WBS is similar to a deliverable-oriented WBS except that it is organized, at the highest level, by phases or steps in a process rather than by deliverables.  A process-centered WBS typically includes the following: 

-        Level 2 activities are phases or schedule checkpoints/milestones.  These activities could be SDLC phases such as Initiation, Planning, etc. 

-        Level 3 activities are those activities required to complete Level 2 phases or milestones.  Multiple tasks are included for any work that needs to be done in multiple phases.

Additional levels are used depending on the duration of the phase or schedule and the level of detail required to reliably estimate cost and schedule.