Spiral Model

This is extension of Waterfall methodology with Prototype. In this model software is developed in incremental increases. Each phase starts with a design goal and ends with the user. In each phase progress is reviewed. You can revisit each phase. Analysis and engineering efforts are applied at each phase of the project, keeping in mind the end goal of the project. This model also addresses the risk management. Credit goes Dr. Barry Boehm for developing this methodology.