What is Spiral Model?

This model follows a process in which the requirements all the phase activity is performed iteratively till all the requirements are met. This enables the product to be demonstrated at any point of time during the development cycle. It allows the progress to be tracked and the customer approvals to be obtained at regular intervals, thereby reducing the risk of finding major defects at a later point of time.The spiral model is favored for large, expensive, and complicated projects.

This model allows for incremental releases of the product, or incremental refinement through each time around the spiral. This model also explicitly includes risk management within software development. Identifying major risks, both technical and managerial, and determining how to lessen the risk helps keep the software development process under control.

Advantages

• Changing requirements can be accommodated.
• Allows for extensive use of prototypes
• Requirements can be captured more accurately.
• Users see the system early.
• Development can be divided in to smaller parts and more risky parts can be developed earlier which helps better risk management.

Disadvantages

• Management is more complex.
• End of project may not be known early.
• Not suitable for small or low risk projects (expensive for small projects).
• Process is complex
• Spiral may go indefinitely.
• Large number of intermediate stages require excessive documentation.