A work breakdown structure (WBS) is a chart in which the critical work elements, called tasks, of a project are illustrated to portray their relationships to each other and to the project as a whole. The graphical nature of the WBS can help a project manager predict outcomes based on various scenarios, which can ensure that optimum decisions are made about whether or not to adopt suggested procedures or changes.
When creating a WBS, the project manager defines the key objectives first and then identifies the tasks required to reach those goals. A WBS takes the form of a tree diagram with the "trunk" at the top and the "branches" below. The primary requirement or objective is shown at the top, with increasingly specific details shown as the observer reads down.
When completed, a well-structured WBS resembles a flowchart in which all elements are logically connected, redundancy is avoided and no critical elements are left out. Elements can be rendered as plain text or as text within boxes. The elements at the bottom of the diagram represent tasks small enough to be easily understood and carried out. Interactions are shown as lines connecting the elements. A change in one of the critical elements may affect one or more of the others. If necessary, these lines can include arrowheads to indicate time progression or cause-and-effect.
A well-organized, detailed WBS can assist key personnel in the effective allocation of resources, project budgeting, procurement management, scheduling, quality assurance, quality control, risk management, product delivery and service oriented management.