Re: DFD equivalent in OOAD

From: Brian S. Smith (techsupport_at_leapse.com)
Date: 10/15/04

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    Date: 14 Oct 2004 16:56:37 -0700

    "H. S. Lahman" <h.lahman@verizon.net> wrote in message news:<mnSad.4526$275.316@trndny01>...
    > Responding to Kumar P...
    >
    > > What is the equivalent of DFD in OOAD?
    >
    > If depends upon the notation. In UML the Interaction Diagrams
    > (Activity, Collaboration, and Sequence) are all basically DFDs. They
    > just use a different layout (though Activity Diagrams are close) and
    > they provide additional bells & whistles especially designed for OOA/D
    > and to allow the diagrams to semantically link to other diagrams.
    >
    > While a DFD decscribes messages (data flows) between functions, in OOA/D
    > messages are between object responsibilities. Since objects represent
    > ochesive abstractions of individual problem space entities, it is
    > convenient to think of message flows between objects and designate the
    > specific responsibility (method function) secondarily. Hence
    > "swimlanes" rather than a flow chart-like format.
    >
    > One can argue that there is really nothing new in OOA/D. That is, it
    > just represents a re-packaging of already recognized Good Practices from
    > the SA/SD days into new methodologies whose associated notations have
    > been updated for those methodologies. Consequently, the graphical
    > notations are fundamentally the same: a Class Diagram is an Entity
    > Relationship Diagram; a Statechart is a State Transition Diagram; a
    > Package Diagram is a System Block Diagram; and the Interaction Diagrams
    > are DFDs. They are just modfied somewhat os that they play together
    > better in the new methodological context.
    >
    > *************
    > There is nothing wrong with me that could
    > not be cured by a capful of Drano.
    >
    > H. S. Lahman
    > hsl@pathfindermda.com
    > Pathfinder Solutions -- Put MDA to Work
    > http://www.pathfindermda.com
    > blog (under constr): http://pathfinderpeople.blogs.com/hslahman
    > (888)-OOA-PATH

    You're pretty much right on the money. There are many similarities
    between the relational and object world, although debate will
    continue, I'm sure. Because most large systems today use an RDBMS
    (Oracle, for example), I am always looking for these parallels. An
    entity equates to a class (without behavior), and an ERD is very close
    to a Class diagram in displaying the inter-relationship among
    entities, or objects in OOA and OOD. One point should be mentioned,
    however, in that DFDs are "process" oriented, where each bubble
    represents a function (hence the verbs), or perhaps a subsystem of
    functionality (Diagram 0) at the highest level in the DFD hierarchy.
    Regarding Interaction Diagrams, the Sequence Diagram, IMHO, is by far
    the most valuable OO UML diagram (along with the class diagram, of
    course) and is probably your best bet for a fit to a DFD. It parellels
    the use of messages well. 

    --
Brian S. Smith
Leap Systems
techsupport@leapse.com
http://www.leapse.com
(321) 435-7511
"Turn requirements into object models, instantly, with Leap SE."
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