Spiral Model

When the requirements are clear and enhancing regularly, organizations can follow spiral
model to release the software version by version.

1. From the above diagram requirement gathering will be done at first and later design
   this will be continued till the maintenance stage.
2. If customer will need any enhancements, those enhancements will be gathered by them
   and again with the new requirements, analysis will be done. This cycle will be repeated
   for every new version of the software.

Advantages of Spiral model:

1. High amount of risk analysis and hence avoidance of risk is enhanced.
2. Good for large and mission-critical projects.
3. Strong approval and documentation control.
4. Additional functionality can be added at a later date.
5. Software is produced early in the software life cycle.

Disadvantages of Spiral model:

1. Can be a costly model to use.
2. Risk analysis requires highly specific expertise.
3. Project’s success is highly dependent on the risk analysis phase.
4. Doesn’t work well for smaller projects.