The System Life Cycle

The systems lifecycle is the set of stages that are followed when developing an information system

Summary Slide

Systems Life Cycle What prompts a new system? Feasibility study Analysis System design Implementation System maintenance Systems Life Cycle

Systems Life Cycle

Feasibility Study

Analysis

DesignImplementation

Maintenance

Programming

What prompts a new system?

The current system may no longer be suitable for its purpose

Technological developments may have made the current system redundant or outdated

The current system may be too inflexible or expensive to maintain

Feasibility study– does the technology exist to implement the

proposed system, or is it a practical proposition?

– is proposed system cost-effective – if benefits do not outweigh costs, it’s not worth going ahead.

– how long will the system take to develop, or can it be done in a desired time-frame?

Feasibility Study

The results of the investigation are provided in a feasibility report:

•What needs to be done – a set of objectives

•A description of some alternative solutions

•A recommended course of action

AnalysisThe analysis is the first stage you must tackle when developing an information system.

Analysis is the process of deciding what (if anything) the information system should do.

Method Description

Interviews

People who operate the current system can be interviewed to find out what they think of it. Interviews can be in more depth than a questionnaire could be. If an interviewee makes a useful point about the system then the person doing the interview can follow the point up to get further information. This is not possible with a questionnaire.

Questionnaires

Questionnaires are useful when information about a system has to be gathered from a lot of people. Information can be obtained far more quickly by using questionnaires than carrying out interviews. Because people can remain anonymous they may be more likely to tell the truth than they would in an interview.

Observation

Observation of how the current system works and what each person does to use it can give an unbiased view of how the system works. Because the person designing the information system is doing the observation himself it is possible to get first hand information about how the system works.

Documentation

Manuals describing how the current system operates can be collected. Any forms used to collect information for the current system or reports produced by the current system can be looked at.

System design

Design is the process of deciding how you will set up your information system using the software packages you choose.

To produce a good design you need to show how you have arrived at the design you are going to use, and not simply state one design. i.e. you need to justify the choices you have made and perhaps consider alternatives at each step in the design.

System design

The design stage will need to consider:

Input – what data will need to be input

Output – what output is required from the system

Data storage – what data files are needed; what field will be used

Test plan – a plan for testing the system should be carried out. This needs to consider the details of the purpose of each test and the test data that will be used.

Implementation

Implementation is using appropriate software packages to create the system you have designed

During the implementation you need to collect evidence to show how the information system was created. If you decide to make any changes from your design then you will need to explain why the changes have been made, e.g.. Lists of data entered into the database; Example reports / queries

System maintenance

Maintenance may need to take place when:– the system runs satisfactorily but there is still room

for improvement.– All systems will need to adapt to changing needs

within a company.– Problems frequently surface after a system has been

in use for a short time, however thoroughly it was tested. Any errors must be corrected.

Systems Life Cycle

Feasibility Study

Analysis

DesignImplementation

Maintenance

Programming

Summary Slide

Systems Life Cycle What prompts a new system? Feasibility study Analysis System design Implementation System maintenance Systems Life Cycle