What is Data flow diagram (DFD)

Data flow diagram (DFD) is a graphical representation of how data is processed by a system in terms providing input and collecting output. It represents the flow of data through an information system, modeling its process aspects. Data flow diagram can be dividing into more detail using DFD levels and layers which gives clear look with deep view and easy access.

Data flow diagram represents the flow of information, where data comes from, where it goes and where it is stored.

A DFD is often used as a preliminary step to create an overview of the system without going into great detail, which can later be elaborated.

It is designing tool used in top-down approach to system design. So it is used for both analysis and design phase of SDLC.
The purpose of DFD is clarifying system requirements and identifying major transformations of system.

It is also called as bubble chart.

DFD can be used in -:
1] Use of DFD in software engineering-:
With the help of DFD, developers and designers can use it to write pseudo code, which is combination of English and coding language. Pseudo code facilitates the development of the actual code.

2] Use of DFD in business analysis-:
It is used to analyze existing system and find deficiencies.

3] Use of DFD in business process re-engineering-:
DFD used to model a better, more efficient flow of data through a business process.

4] Use of DFD in agile development-:
In agile development DFD can be used to visualize and understand business and technical requirements after merging new requirement and plan the next steps

5] Use of DFD in system structure-:
It is used to analyze the system requirement and improve system technical and non technical requirement basis.

The symbols of DFD used / named after their creators:
1) Yourdon and Coad

2) Gane and Sarson

3) Yourdon and DeMarco

Following symbols depict the four components or notations of data flow diagrams.
1] External entity – Objects outside the system, with which the system communicates

2] Process – Transforms incoming data flow into outgoing data flow.

3] Data flow – Information moves from one to another

4] Data store – Data storage or data files

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