WBS DICTIONARY

A WBS dictionary is a document that defines and describes the work to be performed in each WBS element. The information provided need not be lengthy but should be sufficiently descriptive that the reader understands what the work is that is to be accomplished. Some organizations have found it useful to use a form to facilitate gathering WBS dictionary information. A typical form is presented in Figure 2-12.

FIGURE 2-12 Sample WBS Dictionary Form

The data on the form are all that is needed for the minimum dictionary. In some organizations, however, more data are gathered when applicable, such as budget, schedule, deliverables, earned value management data, and the like, that may be part of a specific WBS element. Such data are useful for work packages but may not be applicable for summary, higher-level elements. A typical WBS dictionary description for a WBS element named “Training,” which might occur at Level 2, follows:

WBS 1.4 Training. This element contains deliverable training services, manuals, accessories and training aids, and equipment used to facilitate instruction through which customer personnel will learn to operate and maintain the system with maximum efficiency. The element includes all effort associated with the design, development, and production of deliverable training equipment and instructor and student guides as defined in the list of deliverables as well as the delivery of training services.

One advantage of a WBS dictionary is the discipline of describing the work in each element in words. Frequently, the brief, summary descriptions of WBS elements are vague or misunderstood, and the dictionary can dispel any miscommunication that might result.

Some planners have found it useful to describe the WBS elements in terms of the activities performed in the element. This has an advantage of clarifying the work in the element without the need for a WBS dictionary. However, the use of activity nomenclature can be confusing and may tend to lose some of the discipline required for a noun-product-based WBS. Another of the drawbacks of using activity-based WBS element descriptors is the difficulty of evaluating whether the 100 percent rule has been violated and differentiating WBS elements from work activities.

A WBS dictionary describing the work in each element can readily be converted into a comprehensive SOW for a project or subproject, and the author can be confident it addresses all the work to be performed. The total project scope is thereby clearly and comprehensively defined.