[Uml-devel] bug

[Jens Krüger]

Am Donnerstag, 28. November 2002 11:29 schrieb Jonathan Riddell:
> > > > > I have never seen such a thing in UML books. Do you really think
> > > > > this is necessary? I mean if it is possible to have multiple
> > > > > transition, why is there fork/join/branch/merge?
> > > >
> > > > well... the forj/join is a different beast: those are to represent
> > > > different threads of execution --> to go to activities which are
> > > > supposed to happen in "parallel" (fork) or to synchronize the
> > > > execution at the end of two activities (join)
> > > >
> > > > s for branch/merge.. yes.. I suppose you are right:
> > > > All you can achieve with multiple transitions can be represented with
> > > > a branch (actually, I think this is the clearer way to do it).. I
> > > > just think that having the transitions directly from the activities
> > > > could save some work.
> > > >
> > > > UML says that activities can have more than one outgoing transitions
> > > > as long as they are differentiated by conditions (if [condition a]
> > > > transition 1, if [condition b] transition 2, else transition 3 )
> > > > which is precisily what branches do ... again, it would be only for
> > > > convencience... but it's up to you if you want to accept this.
> >
> > I think it was no good idea to allow multiple outgoing associations from
> > an activity. I've never seen this in any literature, but what I've seen
> > is that an object is used inside an activity diagram which transports
> > information from one to an other activity. But we haven't implemented the
> > occurence of an object in an activity diagram, so we should not allow
> > multiple outgoing an ingoing associations from and to activities. I
> > think, the idea of the singularity of associations is well founded. The
> > designer should use the branche/merge and fork/join elements to model.
> > Otherwise you have no mechanism to check in what case you use the one and
> > in what case you use the other association.
>
> Do you have an opinion on multiple outgoing associations in state
> diagrams?

In state diagrams it is very often used. Assuming you have three states and 
one of them is your normal state you may go to the other both of course if 
your model allows this. Now you have more than one outgoing association.
Otherwise you may reach a state from more than one other and you have multiple 
incoming associations.

Regards

Jens

>
> Jonathan
>
>
>
>
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