Analysis : Breaking The System Down

Usually an information system can be broken down into a number of distinct tasks. For example a system used to manage a car repair garage could be broken down into these tasks :

• Designing an advertisement poster to be displayed around the town the garage is in.
• Booking cars into the garage at appropriate times.
• Producing invoices (bills) for customers showing what work has been done on their cars.
• Keeping track of the spare parts that the garage has in stock.
• Printing pay slips for the garage employees at the end of the week.

Breaking down a job into smaller tasks that can be worked on more easily is known as top down design. The work done in the feasibility study should help identify these tasks. From the garage example you can see that some of the tasks are completely unconnected whereas there may be links between the other tasks :

• The advertisement is not connected to any other task.
• The invoice and stock control system could be linked together. When parts names are written onto an invoice to show that they have been used in a repair then the parts can automatically be taken off the stock list by the stock system. The price of the parts used in the repair can be filled onto the invoice from the stock database.

For a small information system the individual tasks can be tackled one at a time. For a large information system different tasks may be worked on by different people. If a task you have identified is still quite large then you may want to break it up into even smaller parts to work on when you produce your design. Continuing to break a task up into smaller parts like this is all part of the top down design process.

From this point on each task should be treated separately. A separate requirements specification, design, implementation, testing and evaluation stage should be produced for each task.

GCSE ICT Companion 04 - (C) P Meakin 2004