Build data Flow diagrams showing functional dependencies

Data flow diagrams are very useful for showing functional dependencies. In data flow diagrams processes are indicated with bubbles, each bubble containing with name of process inside. Arrowhead lines are used to connect the processes to one another, and to objects in system. The lines are label with information which is being passed.

Objects are drawn as rectangular boxes, same as that of the object model, but usually with just name of these objects and not attributes and operations.

                                                                     A simple DFD is given for sales system