The Work Breakdown Structure (WBS)

After the Gantt chart and the network diagram, there is perhaps no other project management tool that is more ubiquitously discussed than the WBS. 

As the Gantt chart is the primary tool for documenting the project schedule, so is the WBS the primary tool for documenting the project scope.

What is a WBS?

The PMBOK Guide describes the WBS as “a deliverable-oriented hierarchical decomposition of the work required to be executed by the project team to accomplish the project objectives and create the required deliverables.” 

That is, the WBS, “defines the total scope of the project.”

According to this definition, the WBS is a “decomposition of the work required”. 

But work required to do what? There are two kinds of work:

1. Work required to accomplish the project objectives
2. Work required to create the required deliverables

Together, these two kinds of work define the sum total of all kinds of work required: all project work falls into at least one of these two.  We say at least, because it is possible that some piece of work can be properly thought of as belonging to one or the other – that is not a matter of great concern.

The first kind of work is about work that need to be done in order to successfully complete the project objectives, even though they are not the purpose of the project.  An example of this type of work is developing the project schedule (which is needed to help attain project completion date objectives).  Other examples include developing a WBS,  supervising the work-force, and conducting project communications.

The second kind of work is covers what’s needed to deliver what the project needs.  Examples include designing a piece of software, integrating components, reviewing the quality of sub-components, and testing the components.

Note that the WBS is “deliverable-oriented”, but it is not a compilation of the deliverables.  It is a compilation of the work required, hierarchically organised around the deliverables.  The star of the show is the work, not the deliverables.

A software development project with the goal of delivering a commercial software product (and nothing else, not even documentation), the list of deliverables will not change, whether you use an Agile approach or a waterfall approach.

However, the WBS for the Agile approach will be different from the WBS of a waterfall approach.  Examples of the differences include:

• The Agile WBS will include such work as ‘Write User Stories’
• The Waterfall WBS will include such work as ‘Develop Design Document’

The deliverable is the outcome, the work is the effort and activities required to produce the outcome. 

Given that there are many different ways to produce the outcome, the WBS is a reflection of the plan chosen to produce the outcome.  Change the strategy, the WBS can potentially change.