Testing_107 : SDLC Model:Spiral Model

5) Spiral Model :

• In a spiral Model, Software is developed in a series of 'incremental' releases.
• The spiral model is divided into a number of framework activities or task regions.
• Suitable for large projects with Multi-Location implementation.
• Each spiral consists of  deliverable product.
• Feedback of each spiral is incorporated in the next spiral.
• Customer can start using the system after every spiral.
• Each spiral consists of a waterfall Model.

The spiral model has four phases :

• Planning, Risk Analysis, Engineering and Evaluation.
• The baseline spiral, starting in the planning phase, requirements are gathered and risk is evaluated. Requirements are gathered during the planning phase. In the risk analysis phase, a process is undertaken to identity risk and alternate solutions. A prototype is produced at the end of the risk analysis phase.

Software is produced in Engineering phase, along with testing at the end of the phase. The evaluation phase allows the customer to evaluate the output of the project to date before the project continues to the next spiral.
When to use Spiral model :

• When cost and risk evaluation is important.
• For medium to high-risk projects.
• Requirements are complex.
• New product line.
• Significant changes are expected.

Advantages :

• High amount of risk analysis hence, avoidance of risk in enhanced.
• Additional functionality can be added at a later date.
• Software is produced early in the software life cycle.

Disadvantages :

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