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Progressive elaboration is the principle of steadily adding detail to the project plan as more information becomes available.
When to use
Project with high levels of uncertainty on some aspect of the project should progressively elaborate that aspect. The uncertainty could be due to many aspects of the project requirements or plans. Examples include increased insight with respect to resources availability, the selection and use of technology, or reaction to customer and stakeholder input.
Progressive elaboration is not the same as scope creep –which is the addition of fundamentally new requirements. Rather it is the refinement of general requirements, making them more specific as the project progresses. This is sometimes referred to as spiral management or rolling wave management.
- Begin the project with general requirements and a general plan for the areas of the project that will be progressively elaborated. Note: You do not need to progressively elaborate everything. If a portion of the project can be planned in detail, do so.
- Establish points in the project when you will reassess the project plan and refine it based upon the availability of new information. This often occurs at the completion of a major milestone or phase.
- At the refining points, use the new information to add detail and clarity to project requirements and plans
Progressive elaboration of requirements documents
Often a challenge on projects is to get clear and precise requirements. The requirements documents can be progressively elaborated. The example below is based upon a reliability requirement.
- Start with the category of requirement and provide either an upper or lower bound based upon a worst case scenario with a target of the desired level. For instance, our reliability requirement is at least 2,000 hours of use, but our target is 5,000 hours. The project team is not willing to sign up for 5,000 hours because they do not know if the technology can support that level. The previous product was at only 2,000 hours.
- As the project progresses, more information about the technology or approach is learned and we can now refine the requirement based upon what is achievable. The reliability requirement is now a minimum of 4,000 hours plus or minus 500 hours.
- With further design and testing, we now know what our solution is capable of and we are able to set the requirement at 4,200 hours.
Notice that at each step of progressive elaboration we stayed within the bounds that were set at the previous step. If you want to go outside the bounds of the previous step, it would force a requirements change which may be a project change. Notice the final target, while below 5,000 hours is still far above 2,000 hours.
Progressive Elaboration: “The iterative process of increasing the level of detail in a project management plan as greater amounts of information and more accurate estimates become available.” PMBOK® Guide
This definition is taken from the Glossary of the Project Management Institute, A Guide to the Project Management Body of Knowledge, (PMBOK® Guide) – Sixth Edition, Project Management Institute, Inc., 2017.
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