PMI defines “Progressive Elaboration” in PMBOK 3^rd Ed as:

“Progressive elaboration means developing in steps, and continuing by increments. For example, the project scope will be broadly described early in the project and made more explicit and detailed as the project team develops a better and more complete understanding of the objectives and deliverables. Progressive elaboration should not be confused with the scope creep.”

Any EPM project is not perfect from start to finish. Four key elements for any new system introduction to an environment.

1.       Availability

2.       Reliability

3.       Security

4.       Performance

One can either go through all these in one-go, provided you get the required resources or iterate through these one after another over time. With any new system, availability should come first. This makes the system visible to your community. You also get chance of incorporating their feedback (progressively elaborate). Then you progress with other options. Again you make decisions based on resources availability (not MSPS resources availability) & business demands in your organization. In such situations your best bet is to go with “Progressive Elaboration” of your project. You start with something based on the availability of the resources. Then as the project progresses you keep on elucidating the intricacies of the system. That said you refine it over time.