Work breakdown structure

A work breakdown structure (WBS) is an elaboration of the project activities required to achieve the project's objectives. A WBS defines the total work scope of the project. Each descending level represents an increasingly detailed definition of the project work.

A WBS:

WBS elements

A WBS has a tree structure and can include the following elements:
  • Iteration: Iterations are specific to Agile projects, and refer to time-boxed phases of the project lifecycle.
  • Summary task: A summary task comprises a series of tasks. It is usually used to denote a project phase or iteration.
  • Milestone: A milestone is the end of a stage that marks the completion of a work package or phase, typically marked by a high level event such as completion, endorsement or signing of a deliverable, document or a high level review meeting. A milestone is a zero duration event. It is usually used as a control check point or phase gate, and for scheduling methodologies such as Critical Path Method (CPM).
  • Task: A task is a single project activity and represents the lowest-level of work breakdown for a project deliverable.
  • Change requests: Used to track requests for change during the course of a project's execution. You can add tasks to a change request.
  • Issues: Created during the execution phase of a project to communicate the nature of impending or actual problems for which no concrete solution has been proposed. You can add tasks to an issue.
  • Defects: Used to record and track bugs and bug fixes. You can add tasks to a defect.

Each WBS element has attributes such as start and finish dates, duration, and so on. The attributes for the WBS elements are defined during WBS creation. Default values are supplied for each attribute when you create the WBS tree. You can modify the default attributes. For a list of attributes for each WBS element, see WBS element attributes.

A typical project looks like this:
Table 1. Simple WBS
- My Project
  • First summary task
    • Task one
    • Task two
  • Second Summary Task
    • Task three
    • Task four
    • Change Request
      • Change Request task 'a'
      • Change Request task 'b'
  • Milestone
  • Third Summary Task
    • Task five
    • Task six
  • Defect 20
    • Defect task 201
    • Defect task 202
  • Defect 22
    • Defect task 220
    • Defect task 222

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