Work breakdown structure (WBS)

A Work Breakdown Structure (WBS) is a deliverable-oriented hierarchical decomposition of the work to be executed by the project team to accomplish the project objectives and create the required deliverables. Each lower level gives a more detailed definition of the work. The lowest level is a work package. The WBS organises and defines the total scope; work not in the WBS is outside the project.

Features

• Deliverable-oriented, not activity-oriented, using nouns.
• Follows the 100% rule: the WBS includes all work, and children add to 100% of the parent.
• Forms the scope baseline with the scope statement and WBS dictionary.
• Basis for estimating cost and time, assigning responsibility, scheduling and risk identification.

Example (website project)

Website project
|-- 1 Management
|     1.1 Plan   1.2 Reports
|-- 2 Design
|     2.1 UI mockups   2.2 Database
|-- 3 Development
|     3.1 Front end   3.2 Back end
|-- 4 Testing
|-- 5 Deployment and training

Approaches to build a WBS

1. Using guidelines and templates.
2. Analogy (reuse similar WBS).
3. Top-down (start from major deliverables).
4. Bottom-up (list all tasks, then group).
5. Mind mapping.

WBS dictionary

A document describing each element: description, responsible person, schedule milestones, cost, quality requirement, acceptance criteria.

Benefits

• Prevents work being forgotten.
• Gives clear picture of scope to all stakeholders.
• Allows accurate estimates of small work packages.
• Helps with responsibility assignment (RAM) and risk identification.
• Provides progress tracking basis.

Forms

Hierarchical chart (tree) and indented outline list; can be organised by phase or by deliverable.

A good WBS has 3 to 6 levels, and each work package is typically 8 to 80 hours of work.