Software Engineering for Students A Programming Approach
Software Engineering for Students A Programming Approach Software Engineering for Students A Programming Approach
22.4 ● Discussion Exercises 301 Along with other process models, the spiral model does not say how each step (for example design) is carried out. But it is common to use another process model, prototyping, during one or more cycles in order to resolve uncertainty. This might be either to clarify requirements or to establish the technical feasibility of some course of action. The spiral model attempts to solve some of the problems of the waterfall model, while incorporating its best features – planning, phases, intermediate products. The spiral model therefore offers greater flexibility than the waterfall model. SELF-TEST QUESTION 22.1 Identify one advantage and one disadvantage of the spiral model. Summary The spiral model consists of a series of cycles. Each cycle consists of a series of steps. At every cycle, any risks to the successful progress of the project are assessed. Then an appropriate method is selected in order to minimize that risk. Thus the spiral model is essentially a cautious and robust approach to development. The spiral model consists of a repeated cycle of small steps designed to assess and deal with risks at every cycle. Thus the spiral model is termed an iterative approach. • Exercises 22.1 You are preparing a meal for special guests. What risks can you anticipate? How could you use the ideas of the spiral model to cope with problems as they unexpectedly arise? (Suggestions for possible disruptions are: power failure, late guests, missing ingredients and burnt food. But make plans for other contingencies.) 22.2 Using the spiral model, plan how to carry out the development of the user interface part of the ATM system (Appendix A). 22.3 Assess the spiral model for software development. To do this, formulate a list of criteria and then use them.
302 Chapter 22 ■ The spiral model Answer to self-test question 22.1 Advantage: flexibility in the face of risks. Disadvantage: absence of an early fixed plan. • Further reading For the definitive explanation of the spiral model see: Barry W. Boehm, A spiral model of software development and enhancement, IEEE Computer, 21 (5) (May 1988), pp. 61–72.
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302 Chapter 22 ■ The spiral model<br />
Answer to self-test question<br />
22.1 Advantage: flexibility in the face of risks.<br />
Disadvantage: absence of an early fixed plan.<br />
•<br />
Further reading<br />
For the definitive explanation of the spiral model see: Barry W. Boehm, A spiral model<br />
of software development and enhancement, IEEE Computer, 21 (5) (May 1988),<br />
pp. 61–72.
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