Because DFD symbols vary, it’s important to be consistent with whatever notation you choose in order to avoid confusion. Another variation is the symbol used for data stores-Yourdon and Coad uses parallel lines while Gane and Sarson notation uses an open-ended rectangle.
For example, Yourdon and Coad notation uses circles to represent processes, whereas Gane and Sarson notation use rectangles with rounded corners. There are some differences in style between the notation types.
The two main types of notation used for data flow diagrams are Yourdon-Coad and Gane-Sarson, both named after their creators, all experts who helped develop DFD methodology: Ed Yourdon, Peter Coad, Chris Gane and Trish Sarson.
