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Data Flow Diagrams
* Graphically characterize data processes and flows in a business system Basic Symbols
* A double square for an external entity
* An arrow for movement of data from one point to another * A rectangle with rounded corners for the occurrence of a transforming process * An open-ended rectangle for a data store

The four basic symbols used in data flow diagrams, their meanings, and examples

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Creating the Context Diagram
* The highest level in a data flow diagram
* Contains only one process, representing the entire system * The process is given the number 0
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All external entities, as well as Major data flows are shown Creating Child Diagrams
* Each process on diagram 0 may be exploded to create a child diagram * A child diagram cannot produce output or receive input that the parent process does not also produce or receive * The child process is given the same number as the parent process * Entities are usually not shown on the child diagrams below Diagram 0 * If the parent process has data flow connecting to a data store, the child diagram may include the data store as well * When a process is not exploded, it is called a primitive process Differences between the parent diagram (above) and the child diagram (below)

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Data Flow
* Shows movement of data from one point to another
* Described with a noun
* Arrowhead indicates the flow direction
* Represents data about a person, place, or thing
Steps in developing data flow diagrams
Developing Data Flow Diagrams Using A Top –Down Approach
A. Make a list of business activities and use it to determine various * External entities
* Data flows
* Processes
* Data stored
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