Object-Oriented and Classical Software Engineering Fifth Edition, WCB/McGraw-Hill, 2002 Stephen R. Schach [email protected] 3OverviewSoftware Life-Cycle ModelsBuild and Fix ModelWaterfall Model (contd)Rapid Prototyping ModelThree Key PointsWaterfall and Rapid Prototyping ModelsIncremental ModelIncremental Model (contd)Slide 12Slide 13Extreme ProgrammingUnusual Features of XPEvaluating XPSynchronize-and Stabilize ModelSynchronize-and Stabilize Model (contd)Spiral ModelSimplified Spiral ModelFull Spiral ModelFull Spiral Model (contd)Analysis of Spiral ModelObject-Oriented Life-Cycle ModelsFountain ModelConclusionsSlide 3.1© The McGraw-Hill Companies, 2002Object-Oriented and Classical Software Engineering Fifth Edition, WCB/McGraw-Hill, 2002Stephen R. [email protected] 3.2© The McGraw-Hill Companies, 2002CHAPTER 3SOFTWARE LIFE-CYCLE MODELSSlide 3.3© The McGraw-Hill Companies, 2002OverviewBuild-and-fix modelWaterfall modelRapid prototyping modelIncremental modelExtreme programmingSynchronize-and-stabilize modelSpiral modelObject-oriented life-cycle modelsComparison of life-cycle modelsSlide 3.4© The McGraw-Hill Companies, 2002Software Life-Cycle ModelsLife-cycle model (formerly, process model)The steps through which the product progresses–Requirements phase–Specification phase–Design phase–Implementation phase–Integration phase–Maintenance phase–RetirementSlide 3.5© The McGraw-Hill Companies, 2002Build and Fix ModelProblems–No specifications–No designTotally unsatisfactoryNeed life-cycle model–“Game plan” –Phases–MilestonesSlide 3.6© The McGraw-Hill Companies, 2002Waterfall Model (contd)Characterized by–Feedback loops–Documentation-drivenAdvantages –Documentation–Maintenance easier Disadvantages–Specifications»Joe and Jane Johnson»Mark MarberrySlide 3.7© The McGraw-Hill Companies, 2002Rapid Prototyping ModelLinear model“Rapid”Slide 3.8© The McGraw-Hill Companies, 2002Three Key Points Do not turn into productRapid prototyping may replace specification phase—never the design phaseComparison:–Waterfall model—try to get it right first time–Rapid prototyping—frequent change, then discardSlide 3.9© The McGraw-Hill Companies, 2002Waterfall and Rapid Prototyping ModelsWaterfall model–Many successes–Client needsRapid prototyping model–Not proved –Has own problemsSolution–Rapid prototyping for requirements phase–Waterfall for rest of life cycleSlide 3.10© The McGraw-Hill Companies, 2002Incremental ModelDivide project into buildsSlide 3.11© The McGraw-Hill Companies, 2002Incremental Model (contd)Waterfall, rapid prototyping models–Operational quality complete product at endIncremental model–Operational quality portion of product within weeksLess traumaticSmaller capital outlay, rapid return on investmentNeed open architecture—maintenance implicationsVariations used in object-oriented life cycleSlide 3.12© The McGraw-Hill Companies, 2002Incremental Model (contd)Problems–Build-and-fix danger–Contradiction in termsSlide 3.13© The McGraw-Hill Companies, 2002Incremental Model (contd)More risky version—pieces may not fit–CABTAB and its dangersSlide 3.14© The McGraw-Hill Companies, 2002Extreme ProgrammingSomewhat controversial new approachStories (features client wants)Estimate duration and cost of each storySelect stories for next buildEach build is divided into tasksTest cases for task are drawn up firstPair programmingContinuous integration of tasksSlide 3.15© The McGraw-Hill Companies, 2002Unusual Features of XPComputers are put in center of large room lined with cubiclesClient representative is always presentCannot work overtime for 2 successive weeksNo specializationRefactoringSlide 3.16© The McGraw-Hill Companies, 2002Evaluating XPXP has had some successesGood when requirements are vague or changingToo soon to evaluate XPSlide 3.17© The McGraw-Hill Companies, 2002Synchronize-and Stabilize ModelMicrosoft’s life-cycle modelRequirements analysis—interview potential customersDraw up specificationsDivide project into 3 or 4 buildsEach build is carried out by small teams working in parallelSlide 3.18© The McGraw-Hill Companies, 2002Synchronize-and Stabilize Model (contd)At the end of the day—synchronize (test and debug)At the end of the build—stabilize (freeze build)Components always work together–Get early insights into operation of productSlide 3.19© The McGraw-Hill Companies, 2002Spiral ModelSimplified form–Waterfall model plus risk analysisPrecede each phase by–Alternatives–Risk analysisFollow each phase by–Evaluation–Planning of next phaseSlide 3.20© The McGraw-Hill Companies, 2002Simplified Spiral ModelIf risks cannot be resolved, project is immediately terminatedSlide 3.21© The McGraw-Hill Companies, 2002Full Spiral ModelRadial dimension: cumulative cost to dateAngular dimension: progress through the spiralSlide 3.22© The McGraw-Hill Companies, 2002Full Spiral Model (contd)Slide 3.23© The McGraw-Hill Companies, 2002Analysis of Spiral ModelStrengths–Easy to judge how much to test–No distinction between development, maintenanceWeaknesses–For large-scale software only –For internal (in-house) software onlySlide 3.24© The McGraw-Hill Companies, 2002Object-Oriented Life-Cycle ModelsNeed for iteration within and between phases–Fountain model–Recursive/parallel life cycle–Round-trip gestalt–Unified software development processAll incorporate some form of–Iteration–Parallelism–Incremental developmentDanger–CABTABSlide 3.25© The McGraw-Hill Companies, 2002Fountain ModelFeaturesOverlap (parallelism)Arrows (iteration)Smaller maintenance circleSlide 3.26© The McGraw-Hill Companies, 2002ConclusionsDifferent life-cycle modelsEach with own strengthsEach with own weaknessesCriteria for deciding on a model include–The organization–Its management–Skills of the employees–The nature of the productBest suggestion–“Mix-and-match” life-cycle