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SOFTWARE LIFE-CYCLES

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  1. SOFTWARE LIFE-CYCLES Beyond the Waterfall

  2. Milestones The WATERFALL LIFE-CYCLE Requirements System Design Standards Detailed Design Implementation Installation & Testing Documents Maintenance

  3. Problems with the Waterfall Model • sequentiality • late testing paradigm • late feedback to customer and engineer • minimal risk management for customer and engineer

  4. The “V” LIFE-CYCLE Requirements Acceptance Test System Design Integration Test Detailed Design Module Test Implementation

  5. Analysis of the V-Shaped Life-Cycle • Improves the testing paradigm ==> Quality Assurance • Does NOT really improve: • sequentiality • feedback • risk management (during development)

  6. INCREMENTAL DEVELOPMENT Requirements Global System Design Detailed D. Detailed D. Detailed D. Implem. Implem. Implem. Testing Testing Testing Maintenance

  7. Analysis of Incremental Development • Assumes independent subsystems! • Improves (by delivering smaller units): • feedback: stepwise • testing • Avoids monolithic product • Does not really improve: • risk management during development • sequentiality: subsystems

  8. (Rapid) Prototyping • Goals: • break away from sequentiality • speed up feedback • minimize risks for customer and engineer • incomplete but executable • cheap and fast

  9. Prototyping • Definition (A. Davis): A prototype is a partial implementation of a system, constructed primarily to enable customer, user, or developer to learn about the problem or its solution. • Types: • evolutionary / throw-away • horizontal / vertical

  10. Horizontal Prototyping f1 fn user hardware

  11. Vertical Prototyping f1 fn user hardware

  12. Analysis of Pure Prototyping • Improvements: • breaks sequentiality • supports fast feedback • opportunity for risk management • Problems: • missing organisational structure ==> combine with a life-cycle

  13. The Spiral Model • Goals: • risk management • compatible mix between clear structure (life-cycle) & flexible prototyping • supports fast feedback & quality assurance

  14. evaluate alternatives, identify & resolve risks determine objectives, alternatives, constraints risk analysis p r o t o t y p e s principles req. plan require- system ments dev. detailed design design plan integ. plan implement plan the next phase test & install develop & verify product

  15. End of Section 1c coming up: methodologies for analysis & design