It is normal for a team of people to work on the development of a new information system.

1. The system life cycle is a series of stages that are worked through during the development of a new information system. A lot of time and money can be wasted if a system is developed that doesn’t work properly or do exactly what is required of it. A new system is much more likely to be successful if it is carefully planned and developed.

2. It is normal for a team of people to work on the development of a new information system. This group is called the system development project team. Most of the members of this team will be systems analysts. A systems analyst is responsible for finding out about the existing system, designing a new system to replace it and supervising its development. The other members of the team are programmers. Programmers write computer programs that match the design specifications given to them by systems analysts.

3. Stages of the system life cycle

4. The feasibility study is an investigation carried out by systems analysts to find out: • what the main problems are with the existing system • if it is technically possible and cost-effective to solve these problems by developing a computer based solution. • At the end of this stage a feasibility report is produced.

5. A feasibility report should contain: • a description of the existing system outlining what is being done and how it is being done; • a set of problem statements describing exactly what the problems are with the existing system; • a set of system objectives which describe what the new system must be able to do; • a description of some alternative solutions; • a description of the technical, economic, legal and social factors that have been considered; • a recommended course of action.

6. During the analysis stage systems analysts investigate the existing system to identify exactly what the problems are with the existing system • Systems analysts use a variety of fact-finding methods to gather information such as: • questionnaires; • interviews; • observation; • examining documents.

8. Once systems analysts have completed their investigation they produce a detailed description of how the existing system works. Methods used to help describe the system include data flow diagrams and systems flowcharts.

9. Symbols used in Data Flow Diagrams External entity – data source or data destination, for example people who generate data such as a customer order, or receive information such as an invoice. Process – an operation performed on data. The two lines are optional; the top section of the box can be used to label the process, the middle to give a brief explanation, the bottom to say where the process takes place. Data store – such as a file held on disk or a batch of documents Data flow – the arrow represents movement between entities, processes or data stores. The arrow should be labelled to describe what data is involved.

10. Symbols used in systems flowcharts

11. During the design stage: • alternative possible solutions are identified; • alternative solutions are evaluated; • the best solution is identified; • a design specification is produced containing information about: • input; • output; • data storage; • user interface; • backup and recovery procedures; • security procedures; • testing the new system.

12. Typical format for a test plan

13. The implementation stage involves: • Setting up the system so that it matches the design specification. • Testing to make sure that all the parts of the system work correctly with normal, extreme and erroneous data. • Normal test data is used to check that a system can handle the sort of data that would be expected during day-to-day use • Extreme test data is used to check that a system can cope with data that lies on the boundaries of what is acceptable • Erroneous (or exceptional) test data is used to check that a system can identify data that is wrong and reject it.

14. Installing the new system – this might include: • installing any new hardware and software; • transferring data from the existing system to the new one; • training users how to operate the new system. • producing user documentation and technical documentation for the new system.

15. User documentation should contain: • a description of what the system is designed to do; • minimum hardware and software requirements of the system; • instructions on how to load and run the system; • detailed instructions on how to operate each part of the system; • error messages, their meaning and how to deal with them. • where to get more help, such as telephone support lines and on-line tutorials.

16. Part of the user documentation for a new video rental shop system.

17. Technical documentation should contain: • the system design specification; • systems flowcharts; • data flow diagrams; • a description of the various parts of the system and what each one does; • screen layouts and user interface designs; • a test plan.

18. A post implementation review or evaluation should be carried out after a new system has been running for a few weeks or months to identify any modifications that may need to be made. Modifications identified as a result of a post implementation review or evaluation are made during the maintenance stage of the system life cycle.