SOFTWARE LIFE_CYCLE MODEL

1. SOFTWARE LIFE_CYCLE MODEL BY NAMUNA GAUTAM Kathford International College Balkumari,Lalitpur

2. DIFFERENT SOFTWARE MODELS • Build and fix model • Water fall model • Prototyping model • Spiral model

3. Build and Fix Model • Problems • No specifications • No design

4. Waterfall Model • Advantages • Documentation • Maintenance easier • Disadvantages • Specifications not easily understood by clients

5. Rapid Prototyping Model • Determine what the client needs • When developed, the client and users try using it • When they are satisfied, the process moves to the next phase

6. Three Key Points • Do not turn a rapid prototype 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 changes until the client is satisfied, then discard

7. Integrating Waterfall and Rapid Prototyping Models • Waterfall model • Many successes • Client needs may not be met • Rapid prototyping model • Some success but not really proven • Has own problems • Solution • Rapid prototyping for requirements phase • Waterfall for rest of life cycle

8. Incremental Model • The product is designed, implemented, integrated and tested as a series of builds • A build consists of code pieces from various modules interacting to provide a specific functionality • Too few builds can lead to build-and-fix model • Too many builds can lead to inefficient development

9. 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 • Needs open architecture—maintenance implications

10. Synchronize and Stabilize Model • Microsoft’s life-cycle model • Also based on the incremental 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

11. Synchronize and Stabilize Model (contd) • At the end of the day—synchronize (test and debug) • At the end of each build—stabilize (freeze build) • Components always work together • Get early insights into operation of product

12. Spiral Model • Simplified Waterfall model plus risk analysis • Uses rapid prototypes • Precede each phase by • Alternatives • Risk analysis • Follow each phase by • Evaluation • Planning of next phase

13. Simplified Spiral Model • If risks cannot be resolved, project is immediately terminated • Potential risks • Timing constraints • Lack of personnel • Competence of team • Dependency on hardware delivery

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

15. Analysis of Spiral Model • Strengths • Easy to judge how much to test • No distinction between development, maintenance • Weaknesses • For large-scale software only

16. 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

17. Reference • Stephen Schach, Classical and Object-Oriented Software Engineering with UML and Java,Chapter 3, McGraw-Hill, New York, USA. • http://www.mhhe.com/engcs/compsci/schach5/samplech.mhtml