A Work Breakdown Structure (WBS) defines the objectives of a project at all levels of detail. All levels contain the measurable components that must be produced or achieved in order to reach the overall objective, the completion and delivery of the product. The work breakdown structure is hierarchical, as the top objective (Level 1) represents the entire project, while lower levels break down the project into increasingly detailed component outcomes or parts.
The most important consideration in making a work breakdown structure is to avoid mirroring either an organizational structure or a functional structure, since these structures are not outcome-oriented. The defined objectives at all levels must be measurable outcomes and deliverables, the parts and the entirety of what the customer will receive at project completion.
The work breakdown structure must be strictly built to define products and sub-products, as well as services that are directly tied to those concrete outcomes.
Project Management's first step is creating the work breakdown structure, a step that then enables subsequent planning of the work processes and schedule for accomplishing the project. When the work breakdown structure is in place, thoroughly reviewed and finalized, the structure can then be evaluated to determine the processes needed and the scheduled time and costs for achieving each of the goals.
The work breakdown structure, though created at the very beginning of the planning process, needs to be constant during project accomplishment. Work activity schedules will change, budgeted costs and actual costs will change, but objectives remain constant, barring a complete revision to the objective and final deliverable.
The determination of project objectives lends itself to a top-down approach, since the primary objective or end product is the first thing known. Building of the work breakdown structure starts with Level 1, the top objective, continuing with Levels 2 and below requiring managers and planners to carefully consider the outcomes that are required at increasingly more distinct levels of detail to achieve the ultimate objective. Level 2 of the work breakdown structure is necessarily created before moving down to Level 3, and the thought process should follow in that manner until the entire work breakdown structure is in place and ready for review.
Project complexity, expected dollar value, and customer expectations for visibility are among the factors that are considered in determining the number of levels to build into a work breakdown structure. In turn, the project is managed by different levels of managers, at higher or lower levels of the work breakdown structure.
After the start of the project, the performance plan framed by the work breakdown structure moves into project execution. During the execution phase, a Level 3 view provides top managers with sufficient detail for identifying problem areas. This promotes focusing on the project at an appropriate level of detail, while avoiding micromanagement tendencies.
Project managers will generally need the work breakdown structure to be broken down below Level 3, especially on a complex project. Doing so allows leaders at all levels to closely monitor efforts within their respective spans of control. The bottom level of the work breakdown structure consists of "work packages", which represent the efforts and objectives of a small team of individuals who are working on a very specific outcome.
The work packages at the lowest level of detail in the work breakdown structure roll up to elements that are definable outcomes or completed sub-products, which in turn comprise a larger part of the final products, which is defined at the top of the work breakdown structure.
Every element of the work breakdown structure will be assigned a schedule and dollar budget for accomplishment, progress against the objective can be evaluated throughout its period of performance. Problem areas can be identified and process changes or additional resources can be applied to correct problems as they are encountered.
Careful consideration of objectives and the building of the work breakdown structure to identify those objectives during project initiation are essential in the planning and management process.