Software Engineering Data Flow Diagrams | What is DFD (Data Flow Diagram) ?

Data Flow Diagram:

DFD (Data Flow Diagram) is an important tool used by system analysts. The flow of data of a system or a process is represented by DFD. A data flow diagram (DFD) is a visual representation of the flow of information through a process or a system.

It is a graphical representation of flow of data in an information system. It can be used to represent a system in terms of the input data to the system, various processing carried out on those data, and the output data generated by the system.

In nutshell, data flow diagrams simply provide a visual representation of how data is handled in a system. The main merit of DFD is that it can provide an overview of what data a system would process, what transformations of data are done, what files are used and where the results flow. The graphical representation of the systems makes it a good communication tool between a user and analyst. 

DFDs are structured in such a way that starting from a simple diagram which provides a broad overview at a glance, they can be expanded to hierarchy of diagrams giving more and more detail. 

The data flow diagram provides information about the process itself, outputs and inputs of each entity, and the various sub processes the data moves through. 

Components of DFD:

The data flow diagram shows data inputs, outputs, storage, and flow of data using symbols and shapes like rectangles, circles, and arrows. DFD mainly consists of four components. 

The components of DFD are ----

    ·   External Entities    

    ·   Processes

    ·   Data Store

    ·   Data Flow

Name	Description	Symbol
External Entity	It is represented by a rectangle and simply depicts a source or destination of data.
Process	It is represented by a circle and depicts how the data is handled and processed in the system.
Data Store	It is represented by open-ended rectangles and depicts a location where data is stored in the system. A repository of data.
Data Flow	It is represented by an arrow and depicts the flow of data between the entities, processes and data stores.