Work Breakdown Structure
A work breakdown structure (WBS) is “a deliverable-oriented grouping of project elements that organizes and defines the total work scope of the project” [1]: the whole project at the top, each level a finer cut of the level above.
Two rules make the hierarchy useful. The first is NASA’s cardinal rule: “Work scope not contained in the project WBS should not be considered part of the project” [2]. The second is that the WBS has no time axis. “The WBS is NOT a schedule, and is developed before the project team develops a timeline for the project” [3]. A network of tasks says how and when; the WBS says what, and whose. Without it, “it is almost impossible to generate a proper activity network” [4].
The shape is a choice. Globerson calls the WBS “the taxonomy of a project”: the same work can be grouped several valid ways, and each grouping implies a different organisation to run it.
1. The same idea in agile projects
Scrum teams build the hierarchy with size labels [5]. An epic (months, bigger than a release) splits into features (weeks), features into stories (days, small enough for a sprint), and stories into tasks (hours). A theme is not a level: “Some teams also use the term theme to refer to a collection of related stories.” The task layer specifies how to build rather than what, so the scope hierarchy ends at the story.
A theme groups related stories; it is not a level of the tree.
2. The pages
| Page | The question it answers | Main sources |
|---|---|---|
| Orientation | Split the top by deliverable, phase or discipline, and who does each serve? | Globerson, PMI, Wysocki |
| Building a WBS | What goes in, how does the 100% rule hold, and when do you stop? | PMI, NASA, Wysocki |
| Planning waves | How do you plan work you cannot yet define? | Githens, NASA |
| NASA | How does a product tree carry integration and absorb change? | NASA handbooks |
| PMI | What does the PMI standard require, and what do its own examples show? | PMI 2001 |
| WBS tools | Which software draws and maintains a WBS? | vendor list |
How solid is this?
- Where it comes from. Practice standards, agency handbooks and textbooks. None tests whether projects with a WBS do better; the WBS is consensus practice, not a measured result.
- What is framing. Rubin never uses the word “WBS”. Reading his epic-to-task hierarchy as an agile WBS is Miranda’s framing [6], and a useful one.
Acknowledgments
This page adapts material from lectures by Eduardo Miranda and David Root [7] on software project management.
References
- Project Management Institute,Project Management Institute Practice Standard for Work Breakdown Structures, 1st ed. Project Management Institute, 2001.
- National Aeronautics and Space Administration,“NASA Work Breakdown Structure (WBS) Handbook,” National Aeronautics and Space Administration, NASA Special Publication NASA/SP-3404, Nov. 2019. [Online]. Available: https://ntrs.nasa.gov/citations/20200000300
- G. D. Githens,“Rolling Wave Project Planning,” in Proceedings of the 29th Annual Project Management Institute 1998 Seminars & Symposium, Project Management Institute, Oct. 1998. [Online]. Available: https://www.wcu.edu/pmi/1998/NP02.PDF
- S. Globerson,“Impact of various work-breakdown structures on project conceptualization,” International Journal of Project Management, vol. 12, no. 3, pp. 165–171, Aug. 1994, doi: 10.1016/0263-7863(94)90032-9.
- K. S. Rubin,Essential Scrum: A Practical Guide to the Most Popular Agile Process. in Addison-Wesley Signature Series (Cohn). Addison-Wesley Professional, 2012. [Online]. Available: https://innolution.com/essential-scrum
- E. Miranda,“Managing Software Development.” 2014.
- D. Root,Managing Software Development. Carnegie Mellon University / Innopolis University lecture series, 2014.
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