Work Breakdown Structure in Scope Management
In earlier articles I have gone through the steps to define the project scope using a Scope Statement. The Project Scope Statement contains the definition of the scope in detail and for IT projects this is typically in the form of an Enterprise Design Document (EDD).
So we have a detailed description of the scope (the design of the software); where do we go from here? We need to break down the project deliverables into progressively smaller components so they are easier to estimate for time and cost. This is also called decomposition and the resulting structure is called Work Breakdown Structure or simply WBS.
In the WBS, the top layer is of general nature and each subsequent layer gets more and more specific until we are left with small units (or packages) that easily can be estimated for time and cost and at the same time provides enough information to proceed with subsequent activities.
At the bottom of the Work Breakdown Structure are nodes or so-called WBS packages (work packages). So when does a node become a work package? Here are some pointers:
- The work package can’t be decomposed any further
- The work package is small enough to be estimated for time and cost
- The work package can be assigned to a single person
The resulting WBS is a graphical, hierarchical chart where each node has a number to uniquely identify it. If you are using Microsoft Project or other project tools, the WBS is also often shown as a so-called Gantt chart where each indention is a step down in the hierarchy until we reach the final work package.
Once the WBS chart has been established, we need to document the content of each package. For that purpose we must create the WBS Dictionary. The dictionary includes a detailed description of each node and can also include whom it is assigned to, dates, cost, etc.
So what makes a good Work Breakdown Structure? Here are some pointers:
- The work package should be very detailed since they all define every deliverable on the project
- It is hierarchical like a pyramid (or Gantt chart)
- Each node should have a unique number and the numbering system should be logical to allow anyone to find the nodes easily
- It is thorough and complete. If something is not on the WBS, it does not get delivered
- The project team builds the WBS, not just the Project Manager