A WORK BREAKDOWN STRUCTURE (WBS) IS A DECOMPOSITION OF ALL THE WORK NECESSARY TO COMPLETE A PROJECT. A WBS IS ARRANGED IN A HIERARCHY AND CONSTRUCTED TO ALLOW FOR CLEAR AND LOGICAL GROUPINGS, EITHER BY ACTIVITIES OR DELIVERABLES. THE WBS SHOULD REPRESENT THE WORK IDENTIFIED IN THE APPROVED PROJECT SCOPE STATEMENT AND SERVES AS AN EARLY FOUNDATION FOR EFFECTIVE SCHEDULE DEVELOPMENT AND COST ESTIMATING. PROJECT MANAGERS TYPICALLY WILL DEVELOP A WBS AS A PRECURSOR TO A DETAILED PROJECT SCHEDULE. THE WBS SHOULD BE ACCOMPANIED BY A WBS DICTIONARY, WHICH LISTS AND DEFINES WBS ELEMENTS.
The goals of developing a WBS and WBS Dictionary are 1) for the project team to proactively and logically plan out the project to completion, 2) to collect the information about work that needs to be done for a project, and 3) to organize activities into manageable components that will achieve project objectives. The WBS and WBS Dictionary are not the schedule, but rather the building blocks to it. The progression of WBS and WBS Dictionary development is as follows:
The WBS and WBS Dictionary should not be static documents. WBS construction is subject to project management progressive elaboration, and as new information becomes known, the WBS should be revised to reflect that information. A Project Team that has substantial changes to its WBS should reference the project’s Change Management Plan for guidance on management of changes to project scope.
Below is a simplified WBS example with a limited number of organizing levels. The following list describes key characteristics of the sample WBS: • Hierarchical Levels – contains three levels of work
• Numbering Sequence – uses outline numbering as a unique identifier for all levels • Level one is 1.0, which illustrates the project level.
• Level two is 1.X (1.1, 1.2, 1.3, etc.), which is the summary level, and often the level at which reporting is done. • Level three is 1.X.X (1.1.1, 1.1.2, etc.), which illustrates the work package level. The work package is the lowest level of the WBS where both the cost and schedule can be reliably estimated. • Lowest Level Descriptions – expressed using verbs and objects, such as “make menu.”
In a WBS, every level item has a unique assigned number so that work can be identified and tracked over time. A WBS may have varying numbers of decomposition levels, but there is a general scheme for how to number each level so that tasks are uniquely numbered and correctly summarized. Below is the general convention for how tasks are decomposed: • Level 1 – Designated by 1.0. This level is the top level of the WBS and is usually the project name. All other levels are subordinate to this level. • Level 2 – Designated by 1.X (e.g., 1.1, 1.2). This level is the summary level. • Level 3 – Designated by 1.X.X (e.g., 1.1.1, 1.1.2). This third level comprises the subcomponents to each level 2 summary element. This effort continues down until progressively subordinate levels are assigned for all work required for the entire project.
If tasks are properly subordinated, most project scheduling tools will automatically number tasks using the above convention.
WBS Construction Methods
Although there are different methods of decomposing project work and creating a WBS, the most straightforward and effective way is to use some form of visual display of the deliverables, phases, or activities. Ideally, all Project Team members will convene and brainstorm all work required to complete project deliverables successfully. Involvement of all team members in this process increases the likelihood that the resulting WBS will be comprehensive. Typically, team members start by identifying all project deliverables or milestones and then decompose them one at a time into a detailed and sequential list of the detailed activities required to complete the deliverable or milestone....