The spiral model is a software development process that combines elements of both design and prototyping in an risk-driven iterative process. It consists of four phases - planning, risk analysis, engineering, and customer evaluation - that are repeated until the product is completed. The spiral model is well-suited for medium to high-risk projects where requirements are uncertain or likely to change. It allows for user feedback at each cycle to refine requirements and manage risks.

2. IntroductionMalik KhurramBS (telecom) Section 4th (B)Topic spiral modelSoftware Engineering-I

3. HistoryThe spiral model was defined by Barry Boehm in his 1988 article

4. This model was not the first model to discuss iterative development, but it was the first model to explain why the iteration matters.Software Engineering-I

5. Spiral Model Spiral Lifecycle model

6. System Development lifecycle (SDLC)

7. Combines features of prototyping and waterfall model Software Engineering-I

8. When to use Spiral ModelWhen costs and risk evaluation is important

9. For medium to high-risk projects

10. Users are unsure of their needs

11. Requirements are complex

12. New product line

13. Significant changes are expected Software Engineering-I

14. Four Fold ProcedureEvaluating the first prototype in terms of its strengths, weaknesses, and risks.Defining the requirements of the second prototype Planning and designing the second prototypeConstructing and testing the second prototypeSoftware Engineering-I

15. Phase in spiral modelThere are four phases in the “SPIRAL MODEL” which are: Plan Risk analysis Engineering Customer evaluation Software Engineering-I

16. PlanThe objectives, alternatives and constraints of the project are determined and are documented. Software Engineering-I

17. Risk Analysis All possible alternatives, which can help in developing a cost effective project are analyzed

18. This phase identify and resolve all the possible risks in the project developmentSoftware Engineering-I

19. EngineeringThe actual development of the project is carried out

20. The output of this phase is passed through all the phases iteratively in order to obtain improvements in the same. Software Engineering-I

21. Customer evaluationDeveloped product is passed on to the customer in order to receive customer’s comments and suggestions.

22. This phase is very much similar to TESTING phase. Software Engineering-I

23. ApplicationsThe spiral model is used most often in large projects

24. For smaller projects, the concept of agile software development is becoming a viable alternativeSoftware Engineering-I

25. Advantages Users see the system early because of rapid prototyping tools

26. Critical high-risk functions are developed first

27. The design does not have to be perfect

28. Users can be closely tied to all lifecycle steps

29. Early and frequent feedback from usersSoftware Engineering-IUsers see the system early because of rapid prototyping tools

30. Critical high-risk functions are developed first

31. The design does not have to be perfect

32. Users can be closely tied to all lifecycle steps

33. Early and frequent feedback from usersSoftware Engineering-I

34. DisadvantagesTime spent planning, resetting objectives, doing risk analysis and prototyping may be excessive

35. The model is complex

36. Risk assessment expertise is required Software Engineering-I

37. Referenceshttp://www.google.com

38. http://wikipedia.org/wiki/Spiral_model

39. http://scitec.uwichill.edu/spiralmodel.htm

40. http://images.google.com.pk