Microsoft project allows users to group project activities into what is known as summary task. By following simple steps any task can be converted into a summary task. In order to create a summary task, all you need to do is to indent a task just below it. It is a useful tool that can be used to organize project activities. However, there are some do’s and don’ts associated with the use of summary tasks like duration and resources are not assigned to a summary tasks but this post is not about how to create summary task in MS Project but intends to highlight differences between summary task and WBS. I have come across a number of situations where in I have heard people refer to summary task as project work breakdown structure (WBS), which is incorrect.
What is a Work Breakdown Structure (WBS)?
The PMBOK defines WBS as:
The WBS is a hierarchical decomposition of the total scope of work to be carried out by the project team to accomplish the project objectives and create the required deliverable.
The important characteristics of WBS are as follows
- Hierarchical: The WBS is organised in an hierarchical structure with a parent-child relationship. The most commonly used methodology to arrange WBS is the top-down approach. This hierarchical structure can be represented in a tree like format or in a tabular format.
- Decomposition: It is a planning technique to divide the project work into more manageable components. It is also a used to define WBS.
- Deliverable: It is a unique and verifiable product or a service that must be produced to complete the process, phase or a project.
- Work: Work in context of WBS is the product or deliverable as a result of an activity and not the activity in itself.
Work breakdown structure is also used as an input to determine project risk, resources, schedule and costs. If a WBS is created using the 100% rule it provides a confidence that all work and project management process deliverable have been accounted for. WBS establishes a framework for future communication of the project status.
How is a summary task different from WBS?
In MS Project when you indent a task it becomes a sub-task and the task above it becomes a summary task. A summary task displays combined information of all the sub-tasks associated with it. The best use of summary task is for grouping of project activities either for ease of sequencing or understanding the various phases of the project. Summary task can best be used to represent project phases like engineering, procurement, construction and commissioning. In MS Project summary task can be filtered to generate an abridged project progress report.
Summary task as the name signifies are project activities used for structuring the project schedule. Summary tasks are not assigned any predecessor and successor and are also not assigned any duration or resources. MS Project automatically calculates the duration, start, finish dates and the cost associated with the summary task based on the information of the associated sub task.
The best way to avoid confusion between the two is to remember WBS as “deliverable” breakdown structure. Summary task do not communicate attributes associated with WBS and hence should not be confused with work breakdown structure. Hope this post clarifies the differences between summary task and work breakdown structure (WBS).