This process model look like a spiral with many loops. The number of loops in the spiral model is not fixed or limited, we can add as many as required.
Each of the loop is a phase in spiral model.
eg., A loop can be feasibility study , another loop could be Requirement Analysis, etc.
Each of these phases is divided into 4 Quadrants.
-Source : Software Engineering – IIT Kharagpur [M02L04]
Phases of Spiral Model
(A) First Quadrant (Goal or Objective Settings)
- First Quadrant, Objective of phase is set.
- Then all the Risk associated with the objective is identified.
(B) Second Quadrant ( Risk Assessment and Reduction)
- Risks are analyzed for each project.
- Appropriate steps to resolve those risk is taken.
- If risks are unclear a prototype is build to get clarity on the technical or functional issues.
(C) Third Quadrant (Development and Validation)
- After removing all risks, develop the product and validate the next level of the product.
(D) Fourth Quadrant (Review and Planning)
- Review results with customer and plan the next iteration.
- In this way a more complete version of software is built.
When to use the SPIRAL Process Model ?
- Risk analysis is built into the model.
- Software product that complex in nature or carry more risk, then this process model is suitable.
- Project with high risk can also use this model.
- This process model not good for ordinary software projects.