The Spiral Model is illustrated in the Figure 2. The radial
dimension represents the updated cost and the angular dimension
represents the progress through the Spiral. Each section of the
Spiral corresponds to one Stage of the development.
The Spiral Model is one the most practical approach for the
development of software and systems in large scale. It uses an
evolutionary approach, qualifying system analysts and customers
to understand and react to risks.
evaluate new risks and re-plan the project, following an
Evolutionary model.