Exercise06 - Systems Analysis and Design in a Changing...

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Systems Analysis and Design in a Changing World, Fourth Edition 6-1 Chapter 6 – The Traditional Approach to Requirements Solutions to End-of-Chapter Material Review Questions 1. List at least three different types of DFDs. What is each diagram type used to represent? Types of DFDs include context diagrams, event-partitioned system models, subsystem DFDs, diagram 0, DFD fragments, process decompositions, physical DFDs, and logical DFDs. A context diagram contains a single process representing the entire system. The diagram shows important interactions between the system and external agents. An event-partitioned system model contains one process per event. The model shows important interfaces with external agents. If no subsystem DFD is created, the event- partitioned system model is also called diagram 0. A subsystem DFD contains one process per major subsystem. The DFD shows important interfaces with external agents. Each process is further represented by another DFD—an event-partitioned DFD (or diagram zero) for that subsystem. A DFD fragment is a portion of an event-partitioned system model that shows the process, external agents, data stores, and data flows needed to respond to a single event. A process decomposition is a DFD that shows the internal implementation details of a single process on another DFD. A physical DFD is any DFD that shows the specifics of a particular system implementation. A logical DFD is any DFD that shows system requirements under the assumption of perfect technology. 2. List the five component parts (symbols) of a DFD. Briefly describe what each symbol represents. Process (a rectangle with rounded corners) – Represents an algorithm for transforming data input into data output. Data flow (a one- or two-headed arrow) – Represents the movement of data among processes, data stores, and external agents.
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Systems Analysis and Design in a Changing World, Fourth Edition 6-2 External agent (a square) – Represents a person or organization outside the scope and control of the system that provides data inputs and/or accepts data outputs. Data store (a shallow rectangle missing either its left or right side) – Data at rest, awaiting future access by a process or between process invocations.
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