A DFD is a graphical technique that depicts information flow and transformation that are applied as data moved from input to output. This article shows a first level DFD of book management of a Library Management System.
A data flow diagram (DFD) is a graphical technique that depicts information flow and transformation that are applied as data moved from input to output. The DFD may be used to represent a system or software at any level of abstraction. In fact, DFD system may be portioned into levels that represent increasing information flow and functional detail.
In the DFD, a rectangle is used to represents an external entity that is a system, element of another system that produces information for transaction by the software or receives information produced by the software .A circle represents a process for transform that is applied to data and changes it in some way. Processes can be people, procedures or devices that use or produce or transform data. External source or destination data, which may be people, program, organization or other entities, interact with the system but are outside the system boundary. In the data store, data are stored or referenced by a process in the system. The data store may represent computerized or non computerized devices. An arrow represents one or more data items. The double line represents data stored information that is used by the software. DFD may be used to represent a system or software at any level of abstraction. DFD may be pointed in to levels that represent increasing information flow and functional details. DFD provides a mechanism for functional modeling as well as information flow modeling.
DFD may be drawn upto three levels as Zero Level, First Level & Second Level.
A example of DFD if following which describes the process in a Book Library.