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Comprehensive Overview of Software Life-Cycle Models

This document explores various software life-cycle models, including build-and-fix, waterfall, rapid prototyping, incremental, extreme programming, synchronize-and-stabilize, spiral, and object-oriented models. It discusses the phases of software development such as requirements, specification, design, implementation, integration, maintenance, and retirement. Each model's strengths and weaknesses are analyzed, along with key principles for effective software engineering. The discussion aims to provide a framework for selecting the most appropriate life-cycle model based on organizational needs and project characteristics.

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Comprehensive Overview of Software Life-Cycle Models

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  1. Object-Oriented and Classical Software EngineeringFifth Edition, WCB/McGraw-Hill, 2002Stephen R. Schachsrs@vuse.vanderbilt.edu

  2. CHAPTER 3 SOFTWARE LIFE-CYCLE MODELS

  3. Overview • 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 models

  4. Software 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 • Retirement

  5. Build and Fix Model • Problems • No specifications • No design • Totally unsatisfactory • Need life-cycle model • “Game plan” • Phases • Milestones

  6. Waterfall Model (contd) • Characterized by • Feedback loops • Documentation-driven • Advantages • Documentation • Maintenance easier • Disadvantages • Specifications • Joe and Jane Johnson • Mark Marberry

  7. Rapid Prototyping Model • Linear model • “Rapid”

  8. Three 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 discard

  9. Waterfall 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 cycle

  10. Incremental Model • Divide project into builds

  11. Incremental 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 cycle

  12. Incremental Model (contd) • Problems • Build-and-fix danger • Contradiction in terms

  13. Incremental Model (contd) • More risky version—pieces may not fit • CABTAB and its dangers

  14. Extreme 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 tasks

  15. Unusual 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 • Refactoring

  16. Evaluating XP • XP has had some successes • Good when requirements are vague or changing • Too soon to evaluate XP

  17. Synchronize-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 parallel

  18. Synchronize-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 product

  19. Spiral Model • Simplified form • Waterfall model plus risk analysis • Precede each phase by • Alternatives • Risk analysis • Follow each phase by • Evaluation • Planning of next phase

  20. Simplified Spiral Model • If risks cannot be resolved, project is immediately terminated

  21. Full Spiral Model • Radial dimension: cumulative cost to date • Angular dimension: progress through the spiral

  22. Full Spiral Model (contd)

  23. Analysis 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 only

  24. Object-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 • CABTAB

  25. Fountain Model • Features • Overlap (parallelism) • Arrows (iteration) • Smaller maintenance circle

  26. Conclusions • 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 model

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