Data Flow Diagram (DFD), Parts, examples and symbols

Data Flow Diagram (DFD), Parts, examples, and symbols

The data flow diagram shows that how inputs can be given, how data can be processed and how data can be shown as output. Formal and proper visual symbols are used to represent the flow of data from input to processing and from processing to output. The important thing in DFD is that we can see the interaction of different processes with our database.

Parts of the Data Flow Diagram (DFD)

An entity

 An entity is a source of data. An entity can be a name of any place, person, thing, event or object for which data is collected.

A process

A process is performed by the system.

A data store

Different processes can store and can get the data from the data store. Data store means a simple database table.

A data flow.

Data flow is represented by a simple arrow. Data flow indicates the direction of flow of data.

Symbols used in Data Flow Diagram (DFD)

DFD symbols dataflow diagram
Figure: DFD symbols data flow diagram

Example of Data Flow Diagram (DFD)

In this example there are three processes: Verify availability, of course, Enroll student and confirm registration. There are two database tables, courses, and student info. Similarly, only one entity exists as a student.

Data flow diagram DFD eaxmples
Figure: Data flow diagram DFD examples

The student can request for course registration. After that availability, of course, will be tested.

Now the interesting thing to note is that courses availability can only be checked if courses database table gives the response to process course is available or not. Similarly when enrolling the student then all the enrollment details will be saved in the coursed database table.

The database table courses send the response to the process “enroll student” that course is registered or not. If the course is temporarily registered then STUDENT can confirm the registration.


Fazal Rehman Shamil
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