DFD Help (1 Viewer)

[Teh Duke]

Hey guys,

I'm getting a bit confused with the proper way to do DFD's. I never know where to start or how to split up the main process into smaller processes.

Are there any threads or guides that cover DFD's and maybe also example responses to past HSC questions?

 

[ondroo]

I find the best way is to draw a simple context diagram first. That way you know exactly what entities data flows to/from. Then u should refine the system process into basic processes then into more complex processes to the detail required.

 

[mijoe]

Usually, all the processes/entities are written in the question and you simply need to identify them. Otherwise, just make up stuff that seems correct.

 

[cwongquer]

Lol Joe!
Ok
With a DFD, Draw a circle representing the Database
then draw a Box representing where stuff goes, and draw arrows to (request from database <- replace with the request, e.g. "Client Details Request) if needed, but ALWAYS have arrows from Boxes (Things like "Client", "Customer", "Bank" ) and shove words along arrows like "Client Details", "Credit Card Number"
Basically, a DFD shows the FLOW of data and what the data is..
Hope this helps you.

Edit: THIS IS FOR CONTEXT DIAGRAMS, arrows can be from either direction to the Info System, but they must always be.. connected to the information system.

 

[Makro]

Err data stores (i.e. databases) are open rectangles.

Also, external entities are people/organisations, so they're boxes.

The processes (circles) must be a VERB, a doing word: "process this", "collect that".

Data stores can ONLY be linked to a process and not an external entity.

 

[cwongquer]

Oh crap, that was for Context Diagrams..
Well Context Diagrams don't necessarily have to have arrows going to the info system.
Data flow diagrams have:
-Processes (Circles)
-Entities (supply or receive data, Open ended Rectangle)
-Data stores (Rectangle)
-Data Flow (arrows)

Thanks for correcting me Makro!