System development life cycle

The System Development Life Cycle (SDLC) is a framework that describes the phases through which an information system is planned, created, tested, deployed and maintained. It gives a structured approach so that the system meets user needs on time and within cost.

Planning -> Analysis -> Design -> Implementation
    ^                                  |
    |                                  v
Maintenance <- Deployment <------- Testing

Phases

1. Planning / feasibility study
   • Identify the problem and objectives; check technical, economic, operational and schedule feasibility.
   • Output: feasibility report, project plan.
2. Requirement analysis
   • Collect user needs through interviews, questionnaires and observation.
   • Model the current and required system (DFD, use cases).
   • Output: Software Requirement Specification (SRS).
3. Design
   • Architecture, database, interface, algorithm and security design.
   • Output: system design document.
4. Implementation (coding)
   • Developers write the code following standards and do unit testing.
5. Testing
   • Integration, system and acceptance testing find defects and verify the requirements.
6. Deployment
   • Install the system, convert data, train users, and use a parallel or direct changeover.
7. Maintenance
   • Fix bugs (corrective), adapt to new environments (adaptive), add features (perfective) and improve performance.

Advantages

Clear structure and documentation, control of cost and quality, and checkpoints at each phase.

Limitations

Rigid if used linearly; changes late in the cycle are costly; users see the product late.

SDLC models

Waterfall, iterative, spiral, V-model, prototyping and agile are different ways of arranging these phases.

Example: For a hospital system, planning shows the need, analysis collects patient registration requirements, design prepares the database, coders write the modules, testers verify them, staff are trained and the vendor supports maintenance.