A data-flow diagram is a graphical representation of the flow of data through an information system. DFD’s can also be used for the visualization of data processing. On a DFD, data items flow from an external data source or an internal data store to an internal data store or an external data sink, via an internal process.
A DFD provides no information about the timing or ordering of processes, or about whether processes will operate in sequence or in parallel. It is therefore quite different from a flowchart, which shows the flow of control through an algorithm, allowing a reader to determine what operations will be performed, in what order, and under what circumstances, but not what kinds of data will be input to and output from the system, nor where the data will come from and go to, nor where the data will be stored.
Data-flow diagrams are one of the three essential perspectives of the structured-systems analysis and design method. With a data-flow diagram, users are able to visualize how the system will operate, what the system will accomplish, and how the system will be implemented.
http://it.toolbox.com/blogs/enterprise-solutions/data-flow-diagrams-dfds-14573
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