Chapter 12 - Chapter 12 DEveloping Information systems You...

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Chapter 12 DEveloping Information systems You must plan carefully before beginning: Steps in information system design: called the life-cycle of an info. system 1. Analyze needs for new system 2. Design the new systems 3. Code or implement the new system 4. Install the new system - get people using it 5. Maintain the new system Called a life cycle for 2 reasons. Like a living being, an information system has different stages it goes through. The process repeats itself when an existing system is replaced with a newer one. Steps 1 through 4 may take a few months each. Step 5 may last for 2 or 3 years. During this period it may be necessary to make changes - the steps followed for the system as a whole are followed to institute the changes. At the end of the useful period of a system, there are enough problems that need to be fixed that it is better to design a new system that try to maintain the existing system. Step 1. Analyze user needs 1. Bring together a system development team consisting of systems analysts, managers and users of the system. 2. Identify the problem areas. Determine the shortcomings of the existing system and new features that should be in the new system. - 3. Learn as much as possible about the operation of the existing system, so that you will be able to replicate the parts you wish to keep. Document the existing system by creating a data dictionary showing all data items stored in the system, their use and format. Use data flow diagrams to show how data flows through the existing system. Use structured English or pseucode to describe the processes carried out by the existing system. Systems analysts use CASE tools (Computer- Aided Software Engineering) to help build the data flow diagrams and data dictionaries. if quantityOnHand = 0 then Create a backOrder record Write backOrder record to backOrder file else if quantityOnHand < OrderAmount then Perform fill_partial_order process Set QuantityOnHand to zero Create a backOrder record Write backOrder record to back order file else if quantityOnHand > OrderAmount then perform fill_complete_order process
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Chapter 12 - Chapter 12 DEveloping Information systems You...

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