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3. Current System Top Level DFD

Below is the current physical data flow diagram for Electrical World. This shows the current system, warts and all.

electrical world physical diagram

Figure 10: Current Physical DFD Electrical World

 

Some points to note from the diagram:

  • all input and output dataflows from the context diagram are present on the level 1 DFD;
  • the customer external entity has been duplicated in the diagram to aid drawing;
  • the customer data store has been duplicated in the diagram to aid drawing;
  • certain processes have been marked with an asterix in the bottom right hand corner - if a process has been mark like this it indicates that that process will not be decomposed further -this point will be returned to in a later lecture.
   

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