The Work Breakdown Structure (WBS) is one of the most important documents in all of project management. It is a deliverable-oriented breakdown of the tasks to be done for the execution of the project. The project team works from the WBS and uses it as a guiding document throughout the project. As the WBS is broken down, each lower level gives detail to the task it is breaking down. The inputs, which have been previously discussed, are the organizational process assets, project Scope Statement, project Scope Statement plan, and approved changes requests.
The breaking down of the WBS is called decomposition. The verb used to describe this process is "to decompose." The purpose of WBS decomposition is to make the tasks listed manageable. For instance, if a listed task takes eight weeks, you do not have enough control over the task to make it happen on time. You need to decompose the task into smaller units. Generally, the largest unit you can actually manage is considered 40 hours or five days. So any task that is longer than that in your WBS should be broken down to give you control of the sub-tasks as you go through the project.
Identifying major deliverables of the project is another factor that comes from decomposing the WBS. If you are running the project with each major life cycle shown in your WBS, each phase of the life cycle will have deliverables against which you can measure your success. Give yourself clear deliverables that are manageable, and you will be able to control your project.