How Data Flow Diagrams (DFD’s) operate…

20 Feb

1. Imagine you work in a small stock control environment where goods are bought and sold

2. There are two job descriptions in our imaginary system, stock clerks and cashiers

3. Stock Clerks ‘order’ and ‘receive’ goods, and Cashiers ‘sell’ goods

4. An analyst has observed you and come up with the following diagram…


5. The Data Flow Diagram (DFD) is the visible part of the Data Flow Modelling (DFM) technique

6. The DFD is drawn at the very beginning of the analysis where, in various guises, it helps define the context of the system under consideration

7. It then becomes, with the LDS, the main place for recording the analysts’ understanding of how the current system functions

8. When a good understanding of the data movements of the current system has been achieved, the logic of the system is distilled from the DFD and a new ‘logical’ DFD may be produced

9. This DFD contains the essence of the system’s functionality, free from technical and physical constraints that may exist in the current system

10. With the logical view of the system in hand, the analysts propose alternative options for a new system

11. The users choose one of these options and a final DFD is drawn for the, by now, ‘required’ system


2 Responses to “How Data Flow Diagrams (DFD’s) operate…”

  1. sad111332336 February 20, 2013 at 7:06 pm #

    Great blog

  2. sad111463042 February 28, 2013 at 7:38 pm #

    intralling read .. .good work

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