Each cycle involves the same sequence of steps as the waterfall process model.
 |
| Spiral Model |
- Create a design
- Review design
- Develop code
- Inspect code
- Test product
Spiral Model Strengths:
- Provides early indication of insurmountable risks, without much cost.
- Users see the system early because of rapid prototyping tools.
- Critical high-risk functions are developed first.
- The design does not have to be perfect.
- Users can be closely tied to all life-cycle steps.
- Early and frequent feedback from users.
- Cumulative costs assessed frequently.
Spiral Model Drawbacks:
- Time spent for evaluating risks too large for small or low-risk projects.
- Time spent planning, resetting objectives, doing risk analysis and prototyping may be excessive.
- The model is complex.
- Risk assessment expertise is required.
- Spiral may continue indefinitely.
- Developers must be reassigned during non-development phase activities.
- May be hard to define objective, verifiable milestones that indicate readiness to proceed through the next iteration.
When to use Spiral Model:
- When creation of a prototype is appropriate.
- When costs and risk evaluation is important.
- For medium to high-risk projects.
- Long-term project commitment unwise because of potential changes to economic priorities.
- Users are unsure of their needs.
- Requirements are complex.
- New product line.
- Significant changes are expected.
