It is an Iterative model that uses the systematic and formal approaches of the linear model. The idea of minimizing risks by the use of prototype and other means is the concept underlying the spiral model. After each iteration, the different aspects like risk and the number of iterations to be completed are adjusted.

A spiral model is divided into a number of framework activities also called as Task Regions. Typically there are between three to six task regions – Customer Communication, Planning, Risk Analysis, Engineering, Construction and Release, Customer Evaluation. Each of the regions is populated by a set of work tasks called a task set that is adapted to the characteristics of the project. As the evolutionary process begins the team moves around the spiral in a clockwise direction beginning at the center. The first circuit around the spiral might result in the development of specifications; subsequent passes around the spiral might be used to develop a prototype and then progressively more sophisticated versions of the software. Each pass through the planning region results in adjustments to the project plan

This model can be applied to small and large projects with more complex comprehensive and numerous tasks. It may be difficult to convince the customers that the development process is controllable. Also its success relies heavily on the success of the risk analysis expertise used. This model is particularly well suited to the development of object-oriented system.