![]() External entity: an outside system that sends or receives data, communicating with the system being diagrammed.Using any convention’s DFD rules or guidelines, the symbols depict the four components of data flow diagrams. There are other symbol variations in use as well, so the important thing to keep in mind is to be clear and consistent in the shapes and notations you use to communicate and collaborate with others. One main difference in their symbols is that Yourdon-Coad and Yourdon-DeMarco use circles for processes, while Gane and Sarson use rectangles with rounded corners, sometimes called lozenges. Three common systems of symbols are named after their creators: They teamed up in different combinations to be the main definers of the symbols and notations used for a data flow diagram. ![]() Three other experts contributing to this rise in DFD methodology were Tom DeMarco, Chris Gane and Trish Sarson. This rigorous documentation approach contrasts with modern agile approaches such as Scrum and Dynamic Systems Development Method (DSDM.)
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