How to Develop Work Breakdown Structures Michael D. Taylor
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P a g e | 3 WORK BREAKDOWN STRUCTURES “A Work Breakdown Structure 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.”1A Work Breakdown Structure (WBS) is a fundamental project management technique for defining and organizing the total scope of a project, using a hierarchical tree structure. The first two levels of the WBS (the root node and Level 2) define a set of planned outcomesthat collectively and exclusively represent 100% of the project scope. At each subsequent level, the children of a parent node collectively and exclusively represent 100% of the scope of their parent node. A well-designed WBS describes planned outcomes instead of planned actions. Outcomes are the desired ends of the project, such as a product, result, or service, and can be predicted accurately. Actions, on the other hand, may be difficult to predict accurately. A well-designed WBS makes it easy to assign any project activity to one and only one terminal element of the WBS. TYPES OF WORK BREAKDOWN STRUCTURES Even though the term “Work Breakdown Structure” has been used as a label for all project scope hierarchical diagrams, there are, in practice, many types other than “deliverable” oriented structures.1A Guide to the Project Management Body of Knowledge, (Newton Square, PA: Project Management Institute, 2004).
P a g e | 4 Verb-oriented WBS: a task-oriented WBS defines the deliverable of project work in terms of the actions that must be done to produce the deliverable. The first word in a given WBS element usually is a verb, such as, design, develop, optimize, transfer, test, etc. Noun-oriented WBS: a deliverable-oriented WBS defines project work in terms of the components (physical or functional) that make up the deliverable. In this case, the first word in a given WBS element is a noun, such as, Module A, Subsystem A, Automobile Engine, Antenna, etc. Since the nouns are usually parts of a product, this WBS type is sometimes called a “Product Breakdown Structure (PBS). Deliverable-oriented WBS structures are the preferred type according to PMI’s definition.Time-phased WBS: a “time-phased”WBS is one that is used on very long projects. It breaks the project into major phases instead of tasks. In this type, a “rolling wave”approach is adopted and only the near-term phase is planned in detail.