ANALYSIS TOOLSTHEORY13. Data Flow Diagrams (cont)
External Entities
In a DFD, you need to define those external things that have an effect but are not part of the system itself. In the example above the external entities are Factory, Supplier, Accounts and Customer. In this case external entities are represented as an ellipse containing the name of the external entity.
Like so,
An external entity may appear more than once, in which case draw a line within the graphic to show it is a repeating entity, like so,
challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: Planning a DFDs