Data Flow Diagrams

A data-flow diagram is a way of representing a flow of data through a process or a system (usually an information system).The DFD also provides information about the outputs and inputs of each entity and the process itself. A data-flow diagram has no control flow, there are no decision rules and no loops.It is a graphical tool because it presents a picture.It presents a system or software at any level of abstraction.

Four simple notations are used to complete a DFD-

i. Data Flow-The data flow is used to describe the movement of information from a part of the system to another part.

ii. Process-A circle or bubble represents a process that transforms incoming data to outgoing data.

iii. External Entity- A square defines a source or destination of system data. External entities represent any entity that supplies information from the system.

iv. Data Store- The data store is used to collect data at rest or a temporary repository of data.

Example: