lesson 26 • Building Information Systems
This lesson includes the following sections: • The Systems Development Life Cycle • Phase 1: Needs Analysis • Phase 2: Systems Design • Phase 3: Development • Phase 4: Implementation • Phase 5: Maintenance
The Systems Development Life Cycle • The systems development life cycle (SDLC) is an organized method for building an information system. • The SDLC includes five phases: • Needs analysis • Systems design • Development • Implementation • Maintenance
Phase 1: Needs Analysis • In the needs analysis phase, the development team must define the IS-related problem, analyze the current system, and select a solution. • Analysts may document the current system using tools such as data flow diagrams, structured English, or decisions trees. • In this phase, IS workers learn how the current system functions and how it meets (or fails to meet) the organization's informational needs.
Phase 2: Systems Design • During systems design, the team determines how the selected solution will work. To do this, designers may use two design methods: • Top-down design, in which designers start with the large picture and move to the details of its function. • Bottom-up design, in which designers start with the details and move to the major functions. In this phase, designers may create working models, or prototypes, of parts of the system, to see if their designs will work.
Phase 3: Development • In the development phase, software components are either created or acquired. • Programmers may elect to build required software from scratch, or to customize software that is purchased from another source. • In this phase, documentation (such as user manuals or online help systems) is also developed.
Phase 4: Implementation • During implementation, the new system is installed. Four conversion methods can be use to move from an old system to a new one: • Direct – all users stop using the old system and start using the new one. • Parallel –the old system stays in use as increasing amounts of data are processed in the new one. • Phased – users start using the new system, one component at a time. • Pilot – users at one site use the new system while all other users keep the old system.
Phase 5: Maintenance • During the maintenance phase, continuing support is provided to the new system's users. • Changes and upgrades are part of the maintenance phase, as is the process of isolating and repairing problems with the system.
lesson 26 review • Define the term systems development life cycle (SDLC). • Identify the five phases in the SDLC. • Name the IS professionals involved in each phase of the SDLC. • Describe four ways an organization can convert from an old information system to a new one.