Data Flow Diagram And Their Symbols

Data flow diagram (DFD) and their symbols

Data flow diagram (DFD) has following features:-

v  Data flow diagram is a very simple and a standard way to represent database system information graphically.

v  Data flow diagram shows a flow of data in the system.

v  Data flow diagram shows a visualization of the data processing in the system.

v  Data flow diagram hides the complexity of the organization.

v  Data flow diagram is not like a flowchart.

v  Data flow diagram help in understanding that all the data and process are define.

v  Relationship between system and sub system are defines in data flow diagram.

v  Information about an input and output of the system are shows in data flow diagram.

v  Logical data flow diagram does not cause the problem of data duplication and redundancy.

Data flow diagram has a different level such as context diagram, o-level, 1-level etc to represent different aspect of the system. Data flow diagram represents a system in more detail.

The symbols that are used in data flow diagram to represent data flow, process, data store, input or output, files are as follows:-

1.    Input / output

              An Input and output is represented by a rectangular shape.

       

2.    Data flow

              Data flow is represented by an arrow line that is labeled with the name of data. A data flow symbol shows the flow of information from one entity to another entity.

3.    Process / function

                    A process is an action to achieve a particular result or output. In process, incoming data flow is transformed into outgoing data flow.  A process / function are represented by an oval or rounded rectangle shape.

 

4.    Data store

           Data store symbol is used to store data in the database. A data store is represented by rectangle shape that is open in one side and right side of the rectangle is double lines.

5.    Collector

Collector shows that data from different location is merge into a single location.

         

6.    Separator

       A separator is used to separate a thing into different particles.

7.    File / database

                 Database is represented by double line that is separated from one another and database name is written in between these lines.

  

Example of data flow diagram

                   Figure: data flow diagram of food order

Data flow diagram has some issue on the bases of its use

Data flow diagram focused on flow of information and does not provide any facility of decision making.  Physical data flow diagram creates an un-normalized database.