The Process of Project Decomposition

In most instances, it is much easier to solve a problem once it has been broken down into smaller, more manageable parts. How do project managers do this? The answer lies in decomposition.

Decomposition involves subdividing the major project deliverables into smaller, more manageable components until the deliverables are defined in sufficient detail to support development of the project activities involved in planning, executing, controlling, and closing the project. These smaller constituent components then become the basis for creating a project's Work Breakdown Structure (WBS).

The process of project decomposition entails three major steps. These steps will enable you to divide all work, regardless of complexity, into manageable elements. Once you have completed these steps, you will have a workable WBS.

1. Identify the phases and deliverables of the project.
The names of the phases are usually such things as project management, design, development, testing, and integration. The project phases form the basic outline for how the project will unfold. They become the first level of the project's WBS.

A deliverable is any measurable, tangible, verifiable outcome, result, or item that must be produced to complete a phase. You should divide each project phase into its deliverables. These deliverables become the second level of the project's WBS.

2. Determine if deliverables require further decomposition.
A deliverable requires further decomposition if cost and duration estimates cannot be developed at this level of detail. How do you determine whether you can develop adequate estimates of cost and duration? Project managers must answer two questions to determine if they can develop adequate cost and duration estimates for each deliverable.

• First, can the project manager state the approximation of the cost of the resources needed to complete the deliverable?

• Second, can the project manager define the number of work periods required to complete the deliverable? A work period is usually expressed in workdays or workweeks, not including holidays or other nonworking periods.

If the project manager can answer "yes" to both questions, the decomposition process is complete for that deliverable. If the answer is "no" to either question, the project manager will have to proceed to the third step to further decompose the deliverable. Remember, this step is repeated for each deliverable.

3. Identify constituent components of deliverables.
The third step in the decomposition process is identifying the constituent components of the deliverables. The constituent components are referred to as activities. They become the third level of the WBS. As with deliverables, you should define the activities in terms of how the project work will be organized and accomplished.

• Activities should be results-based. You should describe activities in terms of tangible, verifiable results to facilitate performance measurement.

• Activities can be products or services. Activities can include services as well as products. For example, "weekly status reporting" is a service, while "writing software code" is a product.

Once you've identified the activities, you need to do more cost and duration estimating, just as you did for the deliverables. If the component is too broad to develop an accurate estimate, continue to break the constituent components down further.
Constituent components of activities are referred to as tasks or work packages. These components become the fourth level of the WBS. Once you can determine cost and duration estimates, you have finished the decomposing process for that task.

If you apply the three steps of the decomposition process, you can create a WBS that will make your project more manageable and increase the chance of its success.