Work Breakdown Structure (WBS)
A work breakdown structure (WBS) is a hierarchical decomposition of the total scope of work to be carried out by the project team to accomplish the project objectives and create the required deliverables.
Explanation
The WBS is one of the most fundamental project management tools. It organizes the full scope of the project into a tree structure, with the project itself at the top, major deliverables or phases at the next level, and progressively smaller components at each descending level. The lowest level elements are called work packages.
The WBS is deliverable-oriented, not activity-oriented. Each element represents a product, service, or result rather than an action. This distinction is important because activities are derived from work packages during the Define Activities process in Schedule Management. The WBS provides a structured vision of what is to be delivered.
A well-constructed WBS follows the 100% rule: each level must represent 100% of the work in the parent element, and no work should be counted twice. The WBS, together with the project scope statement and WBS dictionary, forms the scope baseline. It serves as a key input to many processes across knowledge areas, including cost estimating, resource planning, risk identification, and procurement planning.
Key Points
- •Hierarchical decomposition of total project scope
- •Deliverable-oriented, not activity-oriented
- •Follows the 100% rule at every level
- •Part of the scope baseline along with the scope statement and WBS dictionary
Exam Tip
The 100% rule is a favorite PMI exam topic. Every level of the WBS must account for 100% of the work in the level above it. No work is omitted and no work is duplicated.
Frequently Asked Questions
Related Topics
Create WBS
Create WBS is the process of subdividing project deliverables and project work into smaller, more manageable components.
WBS Dictionary
The WBS dictionary is a document that provides detailed deliverable, activity, and scheduling information about each component in the work breakdown structure.
Work Package
A work package is the lowest level of the work breakdown structure, representing a deliverable or project work component that can be estimated, scheduled, monitored, and controlled.
Control Account
A control account is a management control point where scope, budget, actual cost, and schedule are integrated and compared to earned value for performance measurement.
Decomposition
Decomposition is a technique used to divide and subdivide the project scope and deliverables into smaller, more manageable parts until the work is defined at the work package level.
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