Friday, September 14, 2012

Data Flow Diagram

  • A data flow diagram (DFD) is a  graphic representation of the application's component parts. 
  • The entities and data flows  from  the  context diagram are  all  present ini DFD.  
  • Data flows may connect processes to other processes,  data  stores,  or  external  entities.  
  • Data stores and external entities do not interact directly with each other. 
  • All entities and data flows from the higher level processes must be in every more detailed diagram.  The names of entities and data flows must be consistent across the levels of the  diagrams

DFD Rules:
  1. Define the processes. 
  2. Define the files  and other data flows  required to support the processes. 
  3. Draw a Level 0 DFD. At level 0,  ignore trivial error paths and data stores. If you define a validation process, you must eventually identify an error path.  Define the error path at the primitive level. Similarly for data stores, define files  when they are shared between processes. Introduce files  that are only used within a given process at the level at which the file  is shared between two or more subprocesses.
  4. Balance the DFD with the context diagram. Compare the net inputs and outputs to external entities on the DFD to the net inputs and outputs on the context diagram. There should be a one-to-one correspondence between the diagrams. 
  5. Iterate through this procedure until the primi-tive level of DFD is reached for  all processes. Always balance the current level DFD's net inputs and outputs with those of the previous level.
Sumber: Conger, 2008

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