Spiral model

Spiral Model 

This is a combination of waterfall and iterative model. Each phase starts with a design goal and ends with the client reviewing the system.

Spiral model is one of the most important Software Development Life Cycle models, which provides support for Risk Handling. In its diagrammatic representation, it looks like a spiral with many loops. The exact number of loops of the spiral is unknown and can vary from project to project. Each loop of the spiral is called a Phase of the software development process.

Phase of Spiral model:

1)  Planning:

Requirements are gathered from the customers and the objectives are identified, elaborated and analyzed at the start of every phase. Then alternative solutions possible for the phase are proposed in this quadrant.

2)  Risk analysis : 

During the second quadrant all the possible solutions are evaluated to select the best possible solution. Then the risks associated with that solution is identified and the risks are resolved using the best possible strategy. At the end of this quadrant, Prototype is built for the best possible solution.

Potential Risk are identified in this phase and risk mitigation(the action of reducing the severity) strategy is planned and finalized.

3)  Engineering :

 Actual development and testing of the software is done in this phase.

4)   Evaluation : 

Customer evaluate the software and provides the feedback and approval.