The difference between a logical and a physical data flow diagram, typically referred to as a DFD, lies primarily in how the data is identified and represented. A data flow diagram in general represents the movement of data within an organization, concentrating on its information system. A logical DFD focuses more on the organization itself and identifies the data-generating events that take place. A physical DFD instead is concerned with how that data is represented.
Both types of DFDs are valuable tools for allowing users to monitor the flow of information from its entry point to its movement throughout the organization, and eventually to its exit point. Interpretation of the data along the way relies partially on recognizing whether the information is processed sequentially or in a parallel fashion. The benefits of a logical DFD include easy communication between employees, the potential for more stable systems, better understanding of the data and the system by analysts, and an overall flexibility. It is also easy to maintain and to remove redundancies as they accumulate. A physical DFD, on the other hand, has a clear distinction between manual and automated processes, provides more controls over the system, and identifies temporary data stores.