The Work Breakdown Structure defines and communicates “what” is to be done in a project. The scope of the project. The best WBS follows three rules:
- Break the overall work into logical pieces and construct a hierarchical structure with those pieces;
- Express the work in nouns, no verbs in the WBS. The WBS contains the things(products and services) that are to be delivered and breaks those things into pieces (still things);
- No dependencies, no durations. WBS can point to, but not contain the dependencies, resource needs or durations of activities. These qualities are needed in successful planning, but should be separable from the WBS. How we accomplish the delivery of the things represented in the WBS is outside the WBS proper. As you develop the WBS you can note and document the “How do we do it”, but that information needs to be kept separate for the WBS. Some of this information is communicated in the WBS Dictionary. (More on that later)
If you conceptually and literally keep the “How” separate from the “What”, you will plan projects that can be more successful. What many project managers and others do in the planning of efforts is to combine the WBS with the Activities Breakdown Structure or ABS. The function of the ABS is to take the lowest level of the WBS (the work package or work unit) and document the planned activities needed to accomplish this work package.
There is value in separating these two planning devices. Anyone who has asked the question, “What are we trying to accomplish?”, when you are in the middle of executing a project can attest; we can get lost in the doing and lose sight of what is to be done. Even the most intuitive project manager needs to be able to unbundle the “what” from the “how” to be able to communicate clearly to other stakeholders.
Another way of looking at the WBS and ABS is to relate it to “a Means to an End.” The WBS defines the “End” and the pieces that make up the “End”. The ABS shows the means or what do we have to do to get the “End” desired.