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Created with Fabric.js 1.4.5 System analysis and design A system analysis team if often brought in to review an existing system and suggest a number of improvements.There are many stages in system analysis: Analysis Design Developmentand testing Implementation Documentation Evaluationand review Analisys stage: 1) fact finding/collecting data from the current system.2) description of the current system.(establishing inputs, outputs and procecing being done)3) identification of the problems with the current system.4) agreeing the objectives with the customer.5) identifying and agreeing the customerยดs requirements.6) interpreting the custommerยดs requirements7) producing a cost-benefit analysis.8) producing a data flow diagram. Design stage: In order to design the key parts of the recommended system, the most important tasks to be done are:> to select and design the validation rules that are needed to be used.> to select the most apropiate data verification methods. >Verification: It is a way of preventing errors when data is copied from one medium to another (e.g. from paper to disck).There are two comon ways that verification checks are carried out: 1) Double entry: in this method, data is entered twice, using two different people.The computer compares the two entries, either after data entry or during the data entry process,and identifies any differences.2) Visual Check: this is the checking for errors by comparing entered data on the screen with thedata in the original document (this is not the same as proof reading). >Validation: Validation is a process where data is checked to see if it satisfies certain criteria when input intoa computer, for example to see if the data falls within accepted boundaries. The most comon validation techniques are: <>Range check: Checks whether the data is within given/acceptable values.(e.g. A personยดs age should be in the range >0 but <150).<>Length check: Checks if the input data contains the required number of characters.(e.g. if a field needs six digits then inputting a five- or seven-digit number,for example, should cause an error message).<>Character/Type check: Checks that the input data does not contain invalidcharacters.(e.g. A personยดs name should not contain numbers).<>Format/Picture check: Checks that the data is in a specific format.(e.g. date should be in the form dd/mm/yyyy).<>Limit check: Similar to range check exept that only one of the limits (boundaries) is checked.(e.g. input data must be >10).<>Presence check: Checks if data is actually present and has not been missed out.<>Consistency check: Checks if fields correspond (tie up) with each other.(e.g. If "Mr." has been typed into a fild called TITLE then the GENDER field mustcontain either "M" or "Male"). Once the development of each module is completed, the whole system needs to be tested(all modules functioning together). Modules may not work correctly when together and thismay lead to improving the input and output methods, verification and validation methods, etc.Testing may use many different types of data, which will fall into one of three categories: Normal, Extreme and Abnormal. Development and testing: _Normal: this data which is acceptable/valid and has an expected (known) outcome.(e.g. a month can be any whole number in the range 1 to 12)._Extreme: this is data at the limits of acceptability/validity.(e.g. the month can be either of the two end values -1 or 12-)._Abnormal: this is data outside the limits of acceptavility/validity and should be rejected or cause an error message.(e.g. month number <1 or >12; or negative, decimal numbers). Implementation: Once the system is fully tested, the next stage is to fully implement it.There are four comon methods for changing over from the old system tothe new system. >Direct changeover: the old system is stopped overnight and the new system is introduced immediately.(Benefits are immediate and costs reduced; but if the new system fails, this method can be disastrous)>Parallel running: the old and new systems are run side by side for a time before the new system takesover all toguether.(If the new system fails, the old one will be still available as a back-up; staff have time to get usedto the new system. This method is more expensive than direct changeover since extra staff would beneeded to run both systems together)>Pilot implementation: the new system is introduced into one part of the company and its performanceassessed.(If the system fails only one part of the company is affected; it is posible to train staff in one area only,which is much faster and less costly than parallel running also because only one part of the system isbeing used in the pilot)>Phased implmentation: initialy, only one part of the new system is introduced. Only when it proves towork satisfactorily is the next part introduced, and so on, until the old system is fully replaced.(If the latest part fails, it is only necessary to go back in the system to the point of failure, hence failureis not disastrous; and it is posible to ensure the system works properly before expanding, but thismethod is more expencive than the direct changeover since it is necessary to evaluate each fase beforemoving to the next stage. Once the new system is fully developed, a considerable amount of documentationneeds to be produced for the end user, and for the people who may need to modifyor develop the system further at some stage. Documentation: Evaluation: Once a system is up and running it is necessary to do some evaluation and carry out anymaintenance, if necessary. The following is a list of some of the things considered when evaluating how well the new systemhas worked and that migh lead back to a re-design of part of the system: . compare de final solution with the original requirements.. identify any limitations in the system.. identify any necessary improvements that need to be made.. evaluate the userยดs responses to using the new system.. give out questionnaires to gather responses about the ease of use of the new system.
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