A Work Breakdown Structure (WBS) provides a hierarchical or a breakdown structure that decomposes the project scope into more discrete and manageable work components [1]. The process of breaking down the scope into a WBS should continue until the entire project scope is decomposed in adequate details matching the level of control that the project team wants to exercise.
WBS breaks down the entire project scope into meaningful components. WBS is a key project artifact that provides a basis for project planning, performance measurement, and project control. It also creates common language among the project team members and stakeholders to ensure everyone is using the same terms in referring to specific parts of the project scope.
Contrary to the popular belief that only one WBS should be developed for each project, it is suggested that two WBSs be produced to define a project scope: a deliverable-oriented WBS and a process-oriented WBS [2,3]. These two work breakdown structures are different but they are not produced independently of each other. Developing and using these two key types of WBS has certain benefits that justify the efforts to produce these two artifacts and use them in tandem.
A deliverable-oriented WBS (also known as product-oriented WBS) decomposes the project scope into smaller and more manageable deliverables. Deliverable are tangible components that need to be delivered to complete the project. They are typically a physical component or an item that needs to be produced, obtained, or supplied as a result of executing project activities. These deliverables are either interim or ultimate deliverables that are delivered to satisfy project requirements. In construction projects, preliminary plans and specifications, bid documents, and pre-construction mockups are example interim project deliverables. Example of ultimate project deliverables in a construction project may include concrete structures, structural steels, building facade, and a building’s mechanical system.
WBS elements in a deliverable-oriented WBS are typically in the form of a noun because WBS elements identify tangible components that are typically a physical item that needs to be produced, obtained, or supplied. A verity of breakdown criteria can be used to develop a deliverable-oriented WBS to meets the specific needs of projects. For example, a construction contractor may breakdown its scope of work based primarily on physical locations of different project components; whereas, a mechanical contractor may use a system-wise approach to identify systems, sub-systems, and lower level components in each subsystem to decomposes its scope of work. The following figure provides an example deliverable-oriented WBS for a residential project.
A process-oriented WBS, on the other hand, defines the project scope of work in terms of process steps (i.e., work phases, or functions)[5]. A process-oriented WBS defines what process steps need to be taken to deliver each of the project deliverables. WBS elements in a process-oriented WBS are typically in the form of a verb. They may also identify different work disciplines that are involved to work on various project deliverables. Example WBS elements in a process-oriented WBS include engineering, detailed design, procure, install, and construct. These WBS elements are provided in a hierarchical structure to breakdown the project scope into different functions or process steps. For example, a WBS element such as install may need to be broken down into mechanical and electrical installation depending on a particular project’s scope of work and the scope of responsibilities of the party that is developing the WBS. The following figure provides an example process-oriented WBS for a piping project.
It is important to properly develop project work breakdown structures by choosing proper breakdown criteria, selecting meaningful WBS elements, and using proper level of breakdown to ensure a) project deliverables are properly identified and organized in a hierarchical structure b) work processes are identified in an appropriate fashion to ensure project team members have the same understanding of what needs to be done from a work process or functional perspective to deliver each project deliverable. Developing both deliverable-oriented and a process-oriented WBSs also helps project teams to better identify project activities.
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References:
[1]. Project Management Institute. (2013). A guide to the project management body of knowledge (PMBOK guide). Newtown Square, PA: Project Management Institute. ISBN: 9781935589679
[2]. Golpayegani, S. A. H., & Emamizadeh, B. (2007). Designing work breakdown structures using modular neural networks. Decision Support Systems, 44(1), 202-222.
[3]. AACE International®. RP 33R-15 Developing the Project Work Breakdown Structure, AACE International®, Morgantown, WV, USA
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