ANALYSIS TOOLSTHEORY15. Data Flow Diagrams (cont)
Extra rules
There are some other sensible rules regarding allowed data flows. For instance, a flow from one external entity to another external entity is not useful when describing this particular system.
Another one is, do not show data flows going directly from one data store into another one - simply combine the data stores if that is the case and call the composite data store something else.
The table below summarises the rules for data flow.
challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Creating DFDs