Spiral Model

The spiral model was defined in 1988 by Barry Boehm. It is often used for large projects. Following are the steps for spiral model:

- Define requirements in details
- Create preliminary design
- Create prototype from design
- Evaluate prototype
- Define requirements for next prototype
- Create design for second prototype
- Create second prototype
- And so on...

One can define spiral model in four phases as below
1. Determine objectives
2. Identify and resolve issues/risks
3. Development and test
4. Plan next iteration