Data Flow Diagram (DFD)

Data Flow Diagram (DFD):

It is a logical model that describes what take place in an existing system, or proposed system; it does not specify how the activities are accomplished.

            It shows the flow of data and the flow of logic involved.

Characteristics of DFD:

                                i.            It focuses on the process that transforms incoming data flows (Input) into outgoing data flows (Output).

                              ii.            It shows the passage of data through the system.

                            iii.            This diagram also known as bubble chart.

                             iv.            DFD supports a top down approach for analysis that is an analyst begins with general understanding of system then draws each component’s details.

Symbols used in DFD:

1.      External Entity:

It is a source or destination of data; it may be person, organisation or other entity that interact with the system.

For ex: Customer, supplier;

            The entity supplying data is known as source & those that consume data or give output are called sinks.

2.      Data Flow/Flow line:

It shows how data travels from one point to another point in diagram.

3.      Process: 

It shows the transformation of input data flows to output data flows.

            All processes are numbered in DFD for easy identification. Numbering follows a left to right convention. Name of the process describes what happened to the data as it flows through the process.

4.      Data store:

It is warehouse for data