The PMBOK defines WBS as “a deliverable-oriented hierarchical decomposition of the work to be executed by the team”.
A common mistake in producing a WBS, at least in the IT domain in which I operate, is to construct the WBS in accordance with the Software Development Life Cycle (SDLC), such that the key WBS building blocks are defined as ‘Analysis’, ‘Design’, ‘Build’, ‘Test’, etc. The obvious mistake in this approach is that none of these is a deliverable of the project and are rather various stages in the life-cycle of the deliverables. More specifically, constructing the WBS in that way makes it difficult if not impossible to confirm ALL aspects of the project’s scope have been catered for. Clearly the SDLC will have been adhered to but with high likelihood that some of the deliverables will have been missed out al-together.
Another mistake, easy to fall into, is to start constructing the WBS in the project scheduling tool. Although easy to do and rather tempting, the best method to construct a WBS is on a white-board or using a software that allows constructing hierarchies (functional, organisational and alike). A visual representation of the WBS in a hierarchical view, especially when done in a brainstorming environment, can foster discussion and allow better understanding of the various deliverables and the best way in which they can be decomposed, such that the need to cater for the WHOLE scope is being maintained.
Thinking ‘deliverables’ and not ‘tasks / activities’ requires some getting used to. The tendency to start decomposing the activities is a result of asking the wrong question up-front. The wrong question to ask is ‘what do we need to do first?’. The correct question that needs asking is ‘what deliverables have we been contracted to deliver to the customer?’. This is then followed by a progressive elaboration of the deliverables into sub-deliverables, the collection of which will guarantee a happy customer at the end of the process.
Even if you are not yet used to producing a WBS in the manner discussed above it is not too late to start and slowly build your confidence and proficiency in doing it the right way.
Think about it!