Spiral Model

Spiral model is the combination of waterfall and iterative model. In this model each phases starts with requirements and ends with customer evaluation. This model is old but useful for larger projects, where high risk involved.

Different phases of Spiral model:

• Planning
• Risk analysis
• Engineering
• Evaluation

Spiral Model

Planning Phase: In planning phase requirements (Software Requirement Specification) are collected and documented.

Risk Analysis Phase: In risk analysis phase, a process is undertaken to identify risk and different solutions.  A prototype is produced at the end of the risk analysis phase and if any risk is found during the risk analysis then alternate solutions are suggested and implemented.

Engineering Phase: In this phase software is developed and tested as per requirements.

Evaluation phase: In this phase the customer evaluates the functionality of the project before the project continues to the next spiral.

Advantages of Spiral model:

• High amount of risk analysis is done; hence avoidance of Risk is enhanced.
• Better option to use spiral model for large or long term projects and critical projects.
• Strong approval and documentation control.
• Additional Functionality can be added easily.

Disadvantages of Spiral model:

• Risk analysis requires highly experienced and specific expertise.
• Costly Model to use.
• Project’s success is highly dependent on the risk analysis phase.
• Not suitable for smaller projects.