Progressive Elaboration vs Rolling Wave Planning

Some PMP aspirants get confused with the difference between Progressive Elaboration and Rolling Wave Planning. The concepts are so similar that the confusion is legitimate. So, let's understand these concepts and look at the differences (or similarities).

Planning is an iterative process. Often times, it's difficult to do detailed planning of a project in the beginning. As the project evolves, and more specific and accurate details are available, the planning gets more detailed. With each successive iteration of the planning process, the project plan becomes more elaborate and complete. This approach to planning is known as Progressive Elaboration. The PMBOK Guide Fourth Edition mentions two forms of Progressive Elaboration:

1. Rolling Wave Planning: It is one of the techniques in the 'Define Activities' process under Project Time Management. In this technique, detailed planning is done for activities in near term and high-level planning for activities to be performed far away in the future. As the project progresses, and requirements become more clear, more detailed planning is done for the work packages at lower levels of the WBS.
   
   What better way to understand a concept than looking at an example. Let's say you want to visit India on vacation and your objective is to have fun and explore the country. However, you've never been there before. You do however know some places of interest like The Taj Mahal. Initially, you decide that you'll leave on Dec 20 and return on Jan 04. You book your flight tickets and hotel room in New Delhi (one of the cities with an International Airports). Once you reach New Delhi, you talk to the locals and figure out all the places of interest. Then you plan your days, like when you want to visit each place, how you are going to get there, where you'll stay, what you'll do there, etc. Your plans become more detailed as days progress. This is an example of Rolling Wave Planning.
   
   


2. Prototypes: Prototypes are a technique in the 'Collect Requirements' process under Project Scope Management. Prototyping is a method of obtaining early feedback on requirements by providing a "tangible" working model or a mock-up of the expected product before actually building it. It gives stakeholders an opportunity to test and experiment with a model of their final product and give them a way to 'visualize' their end product. Prototypes help to identify problems early in the project and reduce project risks.
   
   Let's take an example again. Your company wants to build a commercially viable model of a Hydrogen-powered car. Initially, your researchers build several working models (prototypes) of the car, maybe of a smaller size, to conduct experiments and check the feasibility of the project. Based upon the results of the feasibility studies, your company decides whether to move forward with or kill the project.
   
   

In summary, Rolling Wave Planning and Prototyping are forms of Progressive Elaboration.