The work breakdown structure (WBS) is a key output from project scope management because it determines what work must be completed to deliver the objectives of the project. Breaking the work down in a systematic way, and using the project team, reduces the chance of missing anything.
The WBS is a hierarchical decomposition of the work to be completed in order to achieve the project's deliverables, although it should not be confused with an organizational breakdown chart. The WBS defines and structures the total scope of the project because it starts from the deliverables as stated for the project. Once the deliverables are listed, the next stage is to decompose the work into smaller sections. Action to break down the work packages further to specific schedule activities can be done, although the number of levels will be determined by the project's size or complexity. The output of this work produces a graphical representation of the work specified in the project scope statement. The WBS is a unique decomposition of the work generated for each project, but a previous WBS could be used as a template for a comparable project because the required deliverables are likely to be similar.
The reason for breaking down the project to more manageable and defined sections is to enable the project team to estimate the time and costs for each activity or work package. The review and assessment of smaller work packages by project members will provide a better estimate for the overall cost of the project. The same process can be followed to generate the expected time estimates to complete the work; this will also produce a more accurate schedule from which to plan the project. The reasons for creating a WBS for a project are that it:
There are some basic rules to consider when producing a WBS because the resultant diagram achieves a clear indication of the work involved, together with an improved level of buy-in from team members due to their involvement with the work and estimation process. The first rule is to ensure that team members assist the drafting of the WBS in a systematic manner. The next rule to comply with is to make sure that only the work required to meet the project's deliverables is included, and each level should be established before breaking it down further. A key element from this statement indicates that any work not included in the WBS must fall outside the scope of the project. The last rule is to continue breaking down the work until an appropriate level for the project to be managed is reached; the project manager is the only one able to decide this level.
Much work is needed to produce a complete and thorough WBS, but the benefits of using this approach mean there is less chance of work being missed. The project team will also have a better understanding of the project work, together with the knowledge of where their element fits in to the overall scheme. The wide dissemination of the WBS to all stakeholders will maintain the cooperation and communication link with all those involved, which in turn may help manage the project and expectations. Another vital benefit is the team's buy-in to the document, and the opportunity to ensure everyone remains focused on the outputs of the project.
Once the WBS has been completed, it then becomes a valuable tool for the overall management of the project. The WBS is of particular use when you need to evaluate the impact of a requested change in scope as part of the integrated change control, and also when reassessing the scope of the project due to an approved change. Events can move so quickly when managing a project, so there is a chance that your eye can be taken off the ball. A WBS is therefore a useful reference document to indicate what is and is not included in the project, so control on scope creep is easier to achieve. The layout and structure of the WBS also provides an effective tool to maintain the flow of information to all stakeholders, as well as being used to brief new staff on the status and progress of a project. One element to be finalized by the end of the planning process group is to establish the project's scope baseline, because it will be used to measure the level of success in meeting the project's requirements. The key documents for the scope baseline consist of the project's scope statement, WBS and WBS dictionary.
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