Systems Analysis and Design: notes

The systems development life cycle (SDLC) is the set of stages used to replace an old system with a better one.

The stages

1. Problem identification: say clearly what is wrong with the current system.
2. Feasibility study: can we do it? Check if it is technically possible, affordable (economic), legal, and acceptable to staff (operational), and if it can be done in time.
3. Systems analysis: study the current system in detail. Fact-finding methods:
   • Interviews: detailed answers, but take time.
   • Questionnaires: reach many people quickly; answers may be short.
   • Observation: see the real work; people may act differently when watched.
   • Document inspection: read forms, reports and records.
4. Systems design: plan the new system: inputs (forms and screens), outputs (reports), files and database, processes, validation and security.
5. Development and testing: build the system, then test it with normal, extreme (boundary) and erroneous (invalid) data.
6. Documentation: a user guide shows how to use it; technical documentation helps programmers maintain it.
7. User training: teach staff to use the new system.
8. Implementation (changeover):
   • Direct: stop the old, start the new at once. Fast, risky.
   • Parallel: run old and new together. Safe, costly.
   • Phased: bring in one part at a time.
   • Pilot: try it in one branch or department first.
9. Evaluation: check that the new system meets its objectives.
10. Maintenance: fix errors, adapt to change, add improvements.