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WBS/OBS/CBS

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  1. The Work Breakdown Structure (WBS) with its associated WBS dictionary is the key element for organizing any project. Its purpose is to divide the project into manageable segments of work to facilitate planning and control of the scope, schedule, and cost.

    A well designed WBS will ensure all required work is incorporated into the project and that no unnecessary work is included. (100% rule) This Rule states that the WBS includes 100% of the work defined by the project scope and captures all deliverables – internal, external, interim – in terms of the work to be completed, including project management. 
    Early and accurate WBS planning is essential to getting a project off to a good start. If project requirements change, the WBS will evolve with the project. Revisions to the WBS may be required due to the expansion or contraction of project scope and/or the movement of a project through its various stages (i.e., design, engineering, development, production/installation, and operation). Modifications to the WBS are implemented by means of the Change Control process. 

    A sample WBS could be laid out in the following format:

    Phase (A) – Area (BB) – Sub Area (CC) – CWP (DD) – EWP/MR (EE) – Cost Code (FFFFFF)

  2. Organizational Breakdown Structure (OBS). The basis for project control planning includes not only defining what the work is but establishing the general approaches for how the work will be performed. A complementary arrangement to the WBS is the organizational breakdown structure (OBS) that will provide the resources required to perform the project work activities.
    Integrating an organization with the WBS ensures that all project work is accounted for and that each element of work is assigned to the level of responsibility necessary for planning, tracking progress, accumulating costs, and reporting. 
  3. Cost Breakdown Structure (CBS) will typically mimic the WBS structure decided upon above. The most important item is the cost code, (the lowest level shown above) this should be derived once, and kept standard across all your organization's projects.

    An example could be similar as shown below:

    Management (A) – Discipline (BB) – Specialty (C) – Activity (DD)

    Once a structure is agreed upon, a cost & schedule plan can be formed.
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