The project scope definition, priorities, and breakdown structure are the keys to nearly every aspect of managing the project. The scope definition provides focus and emphasis on the end item(s) of the project. Establishing project priorities allows managers to make appropriate trade-off decisions. The structure helps ensure all tasks of the project are identified and provides two views of the project–one on deliverables and one on organization responsibility. The WBS avoids having the project driven by organization function or by a finance system. The structure forces attention to realistic requirements of personnel, hardware, and budgets. Use of the structure provides a powerful framework for project control that identifies deviations from plan, identifies responsibility, and spots areas for improved performance. No well-developed project plan or control system is possible without a disciplined, structured approach. The WBS, OBS, and cost account codes provide this discipline. The WBS will serve as the database for developing the project network which establishes the timing of work, people, equipment, and costs.

PBS is often used for process-based projects with ill-defined deliverables. In small projects responsibility matrices may be used to clarify individual responsibility.