When large scale commercial systems are developed, a formal approach to the task is essential, as there are likely to be many people involved in the development, and all the work has to be co-ordinated and planned effectively. The system development is made up of the following stages:

• Feasibility study

• Systems analysis and design

• Installation/changeover

• Maintenance

• documentation

During any of the above stages, there may be teams of people (analysts/programmers) working on the system, rather than an individual, as the problems will be too much for one person to handle. The advantages of team working are:

• the tasks will be completed in a shorter timescale

• there will be a wider range of expertise available across the team

• there could be specialist knowledge with one team member

• each team member can contribute ideas – more ideas in a team

There are also disadvantages to the team approach:

• there may be a lack of communication between team members

• one team could miss a deadline which would have knock on effects for other teams

Feasibility Study

The feasibility study is the preliminary investigation of a problem used to decide if a solution is possible and how it may be done. It may be carried out by the main design team or by a separate team which will allow a suitable design team to be chosen. The results of a feasibility study are:

• An evaluation of the problem – is it technically possible

• Identification and justification of possible solutions to the problem

• Time scale for completion – can it be completed in a realistic time?

• Benefits of the new system

• A cost benefit analysis to decide if the solution is affordable

• The disruption to the business during installation/changeover

In order to proceed with the development, the proposed solution must be cost-effective, be developed to an agreed time scale and within an agreed budget.

Systems Analysis and Design

Systems analysis is the investigation into a problem and how a new system will solve it. System design is the production of a detailed description showing how the new system will be constructed.

The first stage in the analysis of any new computer system is an investigation into the current system to find out how it works and what is required from the new system. This is called “gathering information” and the main techniques that can be used for this are:

•interviews (staff and customers)

•questionnaires (staff and customers)

•observation of current system

•detailed study of any existing documentation

Interviews

Here the analyst directly contacts the potential user of the proposed system. For the interview to be a success the analyst should: • be prepared, to know beforehand what exactly needs to be asked

• put the interviewee at ease

• phrase questions clearly

• try to gather maximum relevant information and data

• be a good listener

• evaluate the outcome of the interview

Advantage: can extract almost all the information from the users; ask follow up questions Disadvantage: very time consuming method; interviewees could be on many sites

Questionnaires

Here, users of the system are given questionnaires to be filled up and returned to the analyst.

Advantage: able to gather information from a large number of people; can be done quickly. If anonymous then the respondent answers the questionnaires very honestly and critically.

Disadvantage: may not be completed by users who are busy or who may not give it a reasonable priority; difficult to produce useful questionnaires.

Documentation

Records and reports are the collection of information and data accumulated over the time by the users about the system and it's operations. This can also put light on the requirements of the system and the modifications it has undergone. The analyst may scrutinize the records either at the beginning of his study which may give him a fair introduction about the system and will make him familiar with it or in the end which will provide the analyst with a comparison between what exactly is/was desired from the system and its current working.

Advantage: gives the analyst a basis to start the other investigations from.

Disadvantage: records and reports may have a limitation if they are not up-to-date; some changes may not have been recorded.; the system may not be functioning in the same way as the procedures have been laid out. The data to be used in the system needs to be identified, and the storage and organisation of this data needs to be designed. This process involves designing data structures, choosing appropriate file storage methods, file access methods, record structures and data types.

Appropriate methods of capturing the input data will need to be identified, e.g. scanning bar codes, keying data in via keyboards, scanning OMR documents, OCR and voice input. Data validation and verification rules will also have to be identified for the input data. Forms that will be used for capturing the data and for entering the data need to be designed in such a way as to allow for the efficient capture and entry of the data, and make the job easier for the user.

The output from the system will need to be considered. Will it be a soft copy (on screen) or hard copy (printed)? The format of the output will have to be designed, and be appropriate for the user’s needs – summary information for a manager, but more detailed reports for production/clerical staff.

Consideration must also be given to the selection of suitable hardware and software. The hardware chosen must be able to cope with the current requirements, but also allow for expansion of the system e.g. backing storage capacity would need to be large enough to allow for the amount of data to be stored to increase each year, and the processing power of the cpu would need to provide a reasonable response time for all processes. The options for software are: develop bespoke software, specifically for the company, buy “off the shelf” ready written packages, or customise generic software such as spreadsheets or databases.

Computer Science


QR Code
QR Code system_analysis_and_design (generated for current page)