In some alternative notations the Interface shape may be known as a Terminator, an Input/Output or an Entity.Ī Data Flow line shows data flowing from a Process to an external Interface or Data Store, or data flowing from an external Interface or Data Store to a Process. This rectangle shape represents an external Interface, which is any external system or human actor that interacts with our system processes. This lozenge shape represents a system Process which typically consumes data from an Interface or Data Store (see below), transforms it in some way, and then feeds out the end result. There are other symbol sets such as Yourdon-Coad, which comprise the same four element types albeit represented using different shapes. The diagram elements listed below and in the subsequent worked example are based on the Gane-Sarson symbol set (or notation) for Data Flow Diagrams. This does not mean that the DFD has lost its usefulness even for new analysis endeavors, and any business analyst is bound to encounter them while reviewing the original design documentation for ‘legacy’ systems. It shows logically what information is exchanged by our system processes and external interfaces or data stores, but it does not explicitly show when or in what sequence the information is exchanged.ĭata Flow Diagrams are one of the three essential perspectives of the Structured Systems Analysis and Design Method (SSADM) that predates the more recent object oriented design methods and notations such as UML. The Data Flow Diagram (DFD) provides a graphical representation of the flow of data through a system. It follows logically from the Context Diagram article in which we used a much simplified Data Flow Diagram to show a proposed system in the context of its external interfaces and actors. This article describes the Data Flow Diagram devised by Larry Constantine in the 1970s as part of the Structured Analysis movement.
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