Evolutionary Development Models

 

It is an iterative enhancement model. They allow developers to develop more complete versions of the software. The approach used is similar to the approach used in the waterfall model. This model differs from iterative enhancement model in the sense that this does not require a usable product at the end of each cycle. In evolutionary development, requirements are implemented by category rather than by priority. 

Utility:

This model is useful for projects using new technology that is not well understood. This is also used for complex projects where all functionality must be delivered at one time, but the requirements are unstable or not well understood at the beginning.