During the inception phase, the purpose, business rationale, and scope of the project is determined. This is similar to the feasibility analysis that is done in other life cycles.

During the elaboration phase, more detailed requirements are collected, high level analysis is performed, and a general architecture is determined. This phase divides the requirements into increments that can be built separately. As we will see, each increment consists of a subset of high level use cases that capture the user's requirements.

The construction phase builds increments of the system. Each increment is developed using a waterfall approach. This includes detailed analysis and design for the use cases in the increment and coding and testing of the event processors that implement the sequence of events defined by the use cases. The result is production quality software that satisfies a subset of the requirements and is delivered to the end users. Work on different increments may be done in parallel.