Poor definition of project scope is the primary cause of cost over‐runs.
The U.S. Business Round Table
A project can be too big to comprehend in one chunk. Consequently, it should be broken down into smaller manageable pieces. The mechanisms used to help define the deliverables, the product to be supplied and the scope of work to be performed, are: the product breakdown structure (PBS) and the work breakdown structure (WBS). These are the fundamental building blocks of any project.
A PBS is a hierarchical breakdown of the project into its end items as a means of defining the What of a project. The process of developing a PBS helps to identify missing scope items and items that you hadn't thought about. The graphical presentation is a subdivision of the final project, product, or item to be produced, and it:
- Displays and defines the product to be created or produced
- Relates elements of work to each other and to the end product
- Enables responsibilities to be defined and allocated
- Forms a logical, structured, and organized base from which to combine the work to be done, the organization structure, and development of the planning and control systems.
The PBS is developed by exploding the end product into its component parts and the services required. Each package of work must be clearly distinct from all other work packages. Packages are broken down further into lower‐level elements representing units of work at a level where the work is to be performed. ...