Purpose

The work breakdown structure is considered by many to be the key tool of project management. It is a decomposition of the project into its component elements and is used to define the project as a whole. The WBS provides clarification of the project deliverables or tasks (depending on organizational approach or practice). At its various levels, it is used as a work definition tool, a reporting tool, or a project summarization tool.

Application

The applications for the WBS are as varied as the approaches to using it. In some organizations it is used strictly for work definition, which is accomplished by decomposing work elements (deliverables or tasks) into their parts and subparts. Because the WBS is broken down into different levels, its applications at those levels may vary. And because different organizations break down the WBS in different ways (primarily task- or product-oriented categories), those approaches may lead to different applications as well.

The WBS may be applied in requirements definition by defining the deliverables from the macro to the micro level, until the individual components of the deliverable are clearly delineated. It may be applied in work definition by defining the tasks from the macro level (phase or major task area) to the micro level (individual discrete work elements performed by a given individual or function). It can be applied in cost definition as the smallest component elements are priced out and rolled up to create aggregate cost reports. In the task orientation, the individual discrete work elements can provide a critical input to network diagrams.

Content

The WBS consists of a variety of levels, each defining the project in greater detail. At the top, summary or highest level, it is normally labeled 1.0 or X.0 (where X is a specific project identifying code), and identifies the project in its entirety. The next level, the 1.1 (or X.1) level, breaks down the deliverable into major components or the project effort into its major tasks. Beyond the X.1 level, there can be a virtually infinite number of further decompositions (X.1.1, X.1.1.1, X.1.1.1.1, and so on), as the project is broken out into more and more finite detail. At the lowest level, however, should be a discrete deliverable or level of effort about which the project manager needs to be aware. The WBS should be defined down to the project manager’s level of control.

In some organizations, that lowest level will be predetermined by policy or practice. In others, each project manager must discern the appropriate level of depth for his or her project(s). In any instance, the lowest level of the WBS is referred to as a work package.

One level above the work package is the control account or cost account level. The control account or cost account is used primarily for reporting to management, accounting, or the customer.

Approaches

Given the variety of approaches that are possible with a WBS, the key to any successful approach is consistency. If one section of the WBS is broken out by deliverables, then the entire WBS should be deliverables oriented (e.g., if the 1.2.3 section is a subcomponent, then 1.2.4 should not be a task or task area). For a deliverablesoriented WBS, the breakdown may be defined as follows:

The lowest level of that WBS would be a discrete part that is a distinct and separate deliverable. It may be noted that in some major projects, the work package of one organization being supported by major vendors may be the project of the vendor organization.

For a task-oriented WBS, the breakdown may be defined as follows:

The approach is largely driven by either organizational practice or project manager preference, although the U.S. military takes a firm position that the WBS should be a deliverables-oriented document.

Considerations

The WBS evokes passion among some of its users, in that they are ardent that it should be either task or product oriented. As such, when beginning work with a new client or establishing a WBS with a support organization, it is prudent to explore their perspectives and applications regarding the WBS. If they are flexible, existing organizational practice can prevail. If, however, a customer prefers or demands a product orientation and the supporting organization has a history of task-oriented WBSs, some conflict in work definition may ensue.

These actual costs normally include a percentage to acknowledge the organization’s investment and expense in administering a project. This burden rate may be different for human and material resources, depending upon the organization’s accounting practices. Normally, budget costs are broken out by resources and materials so that the burden for each can be easily incorporated and so that management can discern between human resource costs and material resource costs.