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    Expressing Data Flow Diagrams in the Unified Modeling Language

    1. DFD::="Data Flow Diagram".

      This series of diagrams show different ways to model a simple business process.

      SSADM -- Structured Systems Analysis and Design Methodology

      One kind of DFD that shows how stocks are ordered, paid for, sold, and provide income. Notice that all the processes are operating in parallel and are connected by buffered data flows.


      DFD as Use Case

      A Use Case model forces us to introduce actors. The connectivity between use cases must not be shown. Each use case describes a way that a user gets something out of the system -- and is not a running process.

      Use Case version

      DFD as a collaboration

      A collaboration expresses the interactions well but takes a lot of extra drawing and uses non-standard stereotypes. Notice that this diagram models only half of the original DFD.

      Collaboration of half DFD

      DFD as a UML2.0 Activity Diagram

      An activity diagram shows actors as swim lanes and forces you to work out a lot of extra detail: in particular how the external entities operate. As a result the diagram only shows half of the original DFD. Also notice the UML2.0 connectors that express data flows between activities.

      Activity diagram of half the DFD

      DFD as a UML2.0 Component diagram

      In the appendix of the draft UML2.0 standard there is the a notation that can be used to show data flows fairly precisely. There are also a couple of useful stereotypes:

      Component model of DFD

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Formulae and Definitions in Alphabetical Order