How to draw DFD

   

There are only four symbols:

1. Squares representing external entities, which are sources or destinations of data.

2. Rounded rectangles representing processes, which take data as input, do something to it, and output it.

3. Arrows representing the data flows, which can either be electronic data or physical items.

4. Open-ended rectangles representing data stores, including electronic stores such as databases or XML files and physical stores such as or filing cabinets or stacks of paper.

 

There are several common modelling rules that I follow when creating DFDs:

1. All processes must have at least one data flow in and one data flow out.

2. All processes should modify the incoming data, producing new forms of outgoing data.

3. Each data store must be involved with at least one data flow.

4. Each external entity must be involved with at least one data flow.

5. A data flow must be attached to at least one process.

 

 

 

 

 

For more information visit:

http://www.agilemodeling.com/artifacts/dataFlowDiagram.htm