A work breakdown structure is a simple and methodical means of organizing and understanding project scope. The approach enables businesses to take a top-down look at a project and break it into smaller tasks and subtasks that will assist in project completion. It also guides time and cost estimates and schedule development and control. A work breakdown structure (WBS) is a component of project management and systems engineering that breaks a project down into a hierarchy of tasks and deliverables.
Understanding a work breakdown structure
The work breakdown structure diagram illustrates the components of a project vital to its overall success. The final project deliverable is placed at the top of the diagram, with multiple levels below that denoting the systems, sub-systems, components, tasks, subtasks, and work packages critical to project completion. Work packages describe the work required to complete a specific job or process and occupy the lowest level of the WBS diagram.
The number of levels required depends on project complexity. For moderately complex projects, practitioners suggest using three or four levels. More complex projects may require the full complement of six levels. This process of breaking down the project into progressively smaller parts is called decomposition.
Developing a system for the construction of a new aircraft is one example of a complex project with many moving parts. Using a work breakdown structure, the manufacturer may assign one system to aircraft construction and another to pilot training. Within the system tasked with aircraft construction, there may be sub-elements for the airframe, navigation system, and landing gear. Similarly, the airframe construction sub-system itself can be further divided into wings, tail, and fuselage components, and so on.
Creating a work breakdown structure
Following is a very general overview of the steps involved in creating a robust project estimate.
1 – List high-level deliverables
The process starts with defining the project scope. What will the team need to deliver to meet the project end goal?
For example, deliverables for a new company website may include blog content, page design, a sitemap, and front and back end code. Discussing project deliverables as a team is vital because it allows expectations to be set around individual task responsibility.
2 – Segment each deliverable into tasks
These tasks define how the deliverable will be met. In other words, what needs to be done to create the deliverable? What are the task requirements? Are there other project tasks that will assist in its creation? Indeed, are there task interdependencies?
The elements in each level must be mutually exclusive. To avoid duplication and reduce miscommunication, there must be no overlap in deliverables.
3 – Decompose with subtasks
To make the work breakdown structure as detailed as possible, every task must be defined in terms of subtasks. Every level of decomposition must comprise 100% of the level above it and incorporate at least two “child” subtasks.
The process of meticulously ensuring 100% of the scope is captured can be exhaustive, but investing in the approach now means a reduced likelihood of budget blowouts and missed deadlines later.
The company developing a new website may test its navigation menu with ten users. This task can be broken down into subtasks including recruit users, schedule sessions, conduct sessions, compensate users for their time, and write up findings and subsequent recommendations.
The decomposition process should continue until each element can be managed by a single individual or organization.
4 – Format the work breakdown structure and estimate the work
Formatting is usually achieved through Gantt charts because they provide a convenient task hierarchy and are easily referenced. However, a whiteboard or spreadsheet is just as effective.
Once formatted, the team must discuss each task together and estimate a completion time. Summing the estimated completion time for each task will then let the team know whether the project is in or out of the scope defined at the outset.
- A work breakdown structure is a component of project management and systems engineering that breaks a project down into a hierarchy of tasks and deliverables
- A work breakdown structure is particularly useful in complex projects requiring diligent and detailed planning. In a process called decomposition, the project is broken down into progressively smaller levels of deliverables and associated tasks.
- The work breakdown structure process can be performed in four steps. The team starts by defining high-level deliverables and then segments them into tasks and sub-tasks. During the final step, the team assigns a time to completion estimate for each task and uses this information to determine whether the project can be delivered within scope.
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