Solutions_05 - Systems Analysis and Design in a Changing...

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Systems Analysis and Design in a Changing World, Fourth Edition 5-1 Chapter 5 – Modeling System Requirements Solutions to End-of-Chapter Material Review Questions 1. What are some of the reasons for creating models during system development? See the list in Figure 5-2 on page 152. 2. What are three types of models? Mathematical models, descriptive models, and graphical models. 3. What are the two key concepts used to begin defining system requirements? Events the system needs to respond to and things that the system needs to store information about. 4. What is an event? An event is an occurrence at a specific time and place that can be described and is worth remembering by the system. 5. What are the three types of events? External events, temporal events, and state events. 6. Which type of event results in data entering the system? External event. 7. Which type of event occurs at a defined point in time? Temporal event. 8. Which type of event does not result in data entering the system but always results in an output? Temporal event. 9. What type of event would be named Employee quits job ? An external event because the data entering the system would be data about the termination of the employee (who, when, and why).
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Systems Analysis and Design in a Changing World, Fourth Edition 5-2 10. What type of event would be named Time to produce paychecks ? A temporal event because the system knows it is time to produce paychecks at the end of the month. 11. What are some examples of system controls? Validating user input, requiring user IDs and passwords for logging on to the system, backing up data regularly, encrypting data that is transmitted, and so on. 12. What does the perfect technology assumption state? The perfect technology assumption states that events should be included during analysis only if the system would be required to respond under perfect conditions—that is, with equipment never breaking down, capacity for processing and storage being unlimited, and people operating the system being completely honest and never making mistakes. Basically, the perfect technology assumption prevents analysts from worrying about systems controls until later during the design phase. 13. What are the columns in an event table? Event, trigger, source, activity/use case, response, and destination. 14. What is a trigger? A source? An activity or use case? A response? A destination? See margin definitions. A trigger is a data input for an external event and a definition of a point of time for a temporal event. A source is what external agent or actor supplies the data input for an external event. The activity/use case is what the system does when the event occurs (the process). A response is a data output from the system. The destination is the external agent or actor that receives the data output.
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This note was uploaded on 11/16/2011 for the course MATH 407 taught by Professor H.ayad during the Spring '11 term at Cairo University.

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Solutions_05 - Systems Analysis and Design in a Changing...

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