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  • david@uidesign.net
    original article:http://www.egroups.com/group/usage-centered/?start=10 ... weaknesses of ... The clear advantage to UML is that is becoming ubiquitious and
    Message 1 of 1 , Aug 3, 1999
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      original article:http://www.egroups.com/group/usage-centered/?start=10
      >
      > I'm very
      > interested
      > in discussing this topic. E.g., what are the advantages and
      weaknesses of
      > UML for
      > user interface specification and design, and how should we address
      > shortcomings.
      >

      The clear advantage to UML is that is becoming ubiquitious and
      pervasive and will be a common notation amongst software engineers. At
      a code design level, it is clearly capable of expressing some of the
      issues in UI Design. Class Diagrams can provide that Screen, Frame,
      Widget description in a static sense. Statecharts can model the State
      and Event description.

      UML is almost sufficient to express that technical code level of UI
      Design.

      Where UML is weak, and this is no accident - it was never designed for
      UI or HCI purposes, is that it cannot communicate the User level of
      understanding of a UI Design. It cannot communicate what Laura Arlov
      calls the Navigation Model.

      There is also a tendency to degenerate into trying to use UML for
      analysis and design together rather than separately. With UI as with
      Business Modeling, it is essential to analyse then design and to have a
      notation that can cope with each phase independently.

      Use Cases may be useful for Analysis but for code development and
      communicating a rigourous design to coders, I believe that Class
      Diagrams and Statecharts are probably sufficient.

      Some work has been done to extend UML to cope with the Navigation
      Model. For example, Dave Roberts et al, in the OVID work. However, I
      believe that their notation needs to be openly discussed and improved
      before it will be fit for the purpose.

      The Statechart notation will also have to change. Anyone who has tried
      to model a significant UI in a Statechart will know that it suffers
      from the same problem as ERDs, inheritance is shown using containment
      with the super state. This leads to unwiedly drawings. The UML Class
      diagram technique of using arrows to show inheritance works better.

      The areas that need specific work in UML are all related to, how do we
      get from a paper prototype, mock-up etc. through to a code design, in a
      rigourous and traceable fashion, whilst maintaining the ability to
      communicate with Users.

      UML needs extending to express the Navigation model. This will need to
      include extensions for Transaction Scoping and Exception handling. We
      will also need the ability to view the transactions on the Navigation
      Model, the Class Diagram and the Statechart.

      In the meantime, I address the shortcomings by printing out the
      diagrams and adding the missing content by hand.

      David
      http://www.uidesign.net
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