Overview of Software Lifecycle Models

Sep 29, 2024

Software Lifecycle Models

Introduction

  • The objective of software engineering: produce good quality, maintainable software within reasonable time and cost.
  • Mature processes are needed to determine time and effort required beforehand.
  • Lifecycle models affect lifecycle costs of software products.

Software Lifecycle Phases (IEEE Standard)

  • Requirement Phase
  • Design Phase
  • Implementation Phase
  • Test Phase
  • Installation and Checkout Phase
  • Operation and Maintenance Phase
  • Retirement Phase

Software Life Cycle Models

1. Build and Fix Model

  • Ad hoc approach, not well-defined.
  • Simple two-phase model: write code, fix errors.
  • Suitable for small projects, not for large-scale software.

2. Waterfall Model

  • Five phases: Requirement analysis, specification design, implementation, unit testing, integration and system testing, operation and maintenance.
  • Sequential with no overlap.
  • Challenges: Requires complete requirements early, not suitable for large projects or iterative changes.

3. Increment Process Models

  • Effective when requirements are clearly defined.
  • Functionality delivered in phases with each cycle.

4. Iterative Enhancement Model

  • Similar to waterfall but allows multiple cycles.
  • Releases provide additional functionality iteratively.

5. Rapid Application Development (RAD)

  • Increment process model developed by IBM.
  • User involvement from requirements to delivery.
  • Phases: Requirement planning, user description, construction, cutover.

6. Evolutionary Process Model

  • Resembles iterative model; focus on categories.
  • Used for projects using new technology or complex projects.

7. Prototyping Model

  • Develop a working prototype early to refine requirements.
  • Advantages: Early customer feedback.
  • Disadvantages: Not always maintainable or reliable.

8. Spiral Model

  • Incorporates risk assessment into lifecycle.
  • Four phases: Planning, risk analysis, development, assessment.
  • Widely flexible to manage uncertainties.

9. Unified Process (RUP)

  • Iterative and incremental development.
  • Four phases: Inception, Elaboration, Construction, Transition.
  • Aims to accommodate changes and manage risks.

Lifecycle Model Selection

  • Based on requirements, development team, user involvement, project type, and risk.
  • Example factors: complexity, funding stability, reliability requirements, project schedule.

Conclusion

  • Each lifecycle model has its strengths and weaknesses.
  • Selection depends on project-specific factors and characteristics.

These notes summarize the key points discussed in the software lifecycle models lecture. They cover the various software lifecycle models, their characteristics, phases, advantages, and disadvantages, and guidance on selecting the appropriate model for different project needs. They represent a comprehensive guide to understanding the fundamental lifecycle models in software engineering.