Stages in the Systems Development Life Cycle
The systems life cycle models the stages involved in developing an Information technology system. The system life cycle may be looked at as a 7 phase- problem solving procedure.
These stages are:
- Preliminary Investigation
- System Analysis
- System Design
- System Development
- System Implementation
- System Maintenance
This is the first stage of the system life cycle and it involves finding out all about the existing system. Problems (limitations) with the existing systems are determined, and possible solutions are identified. This leads to a feasibility study which involves, costing, timescales, hardware and software requirements and staffing issues.
This stage is often referred to as the preliminary investigation stage, in which case the problems are defined, the scope of the system is determined, alternative solutions are suggested and a short report is produced.
Within this stage, data is collected and a deeper look (study) of the existing system is done. Data collection may be done through observation, interviews, document analysis and questionnaires.
Modeling tools are then used to analyze the system and new requirements are defined.
Modeling tools may include checklists, structural diagrams such as top-down analysis methodology, flow charts, grid charts and decision tables. Others are automated design tools such as computer-aided software engineering tools (CASE) which help system analysts to evaluate hardware and software alternatives.
At the end of this analysis, findings are documented. The documentation of these findings includes the description and scope of the existing system, the requirement of the new system and a proposed development programme or schedule is produced.
The design stage takes into consideration all the information gathered in the previous stages and uses this information to produce a technical document which is often referred to as the system specification.
Before the report or specification is produced however, alternative designs are evaluated. The evaluation of the designs involves economic, technical and operational feasibility. Economic consideration will include cost benefit analysis, while operational and technical evaluation will consider among others flexibility, scalability, integration and security.
At the end, a report is also produced which will include alternative designs and a recommendation.
The system specification developed in the design stage is used to develop the system. Under system development, two options are considered; this involves the type of developing software to use. This may be:
- A packaged software (off-the shelf) e.g. Microsoft access software
- Custom design software (bespoke)
This stage will also take in to consideration the hardware that is needed and the installation process.
The last step of this stage may also include the testing of the new system in which case sample data are fed into the system and the results are evaluated to ensure that the system is working according to specification.
The system implementation stage involves the installation of the system, staff training and conversion. There are different types of conversion plan, these are:
- Direct approach: the old system is completely abandoned and a new one takes it place.
- Parallel approach: Just as the name implies the old and the new systems are operated concurrently. This continues until the new system proves that it can be operated on its own and that it is works according to specification.
- Pilot approach: This is when the new system is launched in just one sector or department of the entire organization or business. If the system works according to specification, it will then be implemented fully.
Stages of a system life cycle may differ depending on a given model. While some stages are separated in one model, they may be merged in another. The main point here is to understand what these stages involve and their roles in the development of information systems.