SUMMARY

The sequential, or waterfall, process is fine for small projects that have few risks and use a well-known technology and domain, but it cannot be stretched to fit projects that are long or involve a high degree of novelty or risk.
An iterative process breaks a development cycle into a succession of iterations. Each iteration looks like a miniwaterfall and involves the activities of requirements, design, implementation, and assessment.
To control the project and to give the appropriate focus to each iteration, a development cycle is divided into a sequence of four phases that partition the sequence of iterations. The phases are inception, elaboration, construction, and transition.
The iterative approach accommodates changes in requirements and in implementation strategy. It confronts and mitigates risks as early as possible. It allows the development organization to grow, to learn, and to improve. It focuses on real, tangible objectives.