Ess of Sys Anls- Rvw Sol- Ch 05

Ess of Sys Anls- Rvw Sol- Ch 05 - Chapter 5: Review...

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Chapter 5: Review Questions Solutions 1. What is a data-flow diagram? Why do systems analysts use data-flow diagrams? A data-flow diagram is a picture of the movement of data between external entities and the processes and data stores within a system. Systems analysts use data-flow diagrams to help them model the processes internal to an information system as well as how data from the system’s environment enter the system, are used by the system, and are returned to the environment. DFDs help analysts understand how the organization handles information and what its information needs are or might be. Analysts also use DFDs to study alternative information handling procedures during the process of designing new information services. 2. Explain the rules for drawing good data-flow diagrams. The rules for DFDs are listed in Table 5–2 and illustrated in Figure 5–6. Processes cannot have only outputs, cannot have only inputs, and must have a verb phrase label. Data can move to a data store from only a process, not from another data store or an outside source. Similarly, data can be moved to only an outside sink or to another data store by a process. Data to and from external sources and sinks can be moved by only processes. Data flows move in one direction only. Both branches of a forked or a joined data flow must represent the same data. A data flow cannot return to the process from which it originated. 3. What is decomposition? What is balancing? How can you determine if DFDs are not balanced? Decomposition is the iterative process by which a system description is broken down into finer and finer detail, creating a set of diagrams in which one process on a given diagram is explained in greater detail on a lower–level diagram. Balancing is the conservation of inputs and outputs to a data-flow diagram process when that process is decomposed to a lower level. You can determine if a set of DFDs are balanced or not by observing whether or not a process that appears in a level- n diagram has the same inputs and outputs when decomposed for a lower-level diagram. 4.
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Ess of Sys Anls- Rvw Sol- Ch 05 - Chapter 5: Review...

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