Re: Status of UML 2.0

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From: Hubert Baumeister (
Date: Fri 25 Oct 2002 - 10:38:53 BST

Dear Robert,

Bauer, Robert wrote:
> Heinrich,

Please read the postings more carefully. I am Hubert and not Heinrich (though I assume he agrees 
mostly with what I am saying :-)

> But my point is that your goal,
> My understanding of "unambiguous" UML is that each UML diagram has well 
> defined meaning as opposed
> to several meanings depending on who is looking at the diagram. This 
> does (and should not) exclude
> the possibility that the same meaning can be expressed by different 
> diagrams.
> is quite difficult, if not impossible to achieve.
> For example, given some program P, I wish to determine it's meaning.  To 
> do so requires that I have
> a formal semantics, one that is unambiguous and complete in the sense 
> that every sentence constructed
> in the implementation language has only one interpretation in the 
> specification language - but that requires
> me to show that the specification language itself is unambiguous - which 
> in general can't be done.

So what your are saying is, that it is impossible to give a precise mathematical semantics to 
programming language constructs?

I suppose the problem is that we have different concepts of "unambiguous" language in mind (cf. 
posting by Peter Schmitt). This is a good example of what in my view is the goal of the 2uworks 
group by trying to give each diagram in the UML an unambiguous meaning as opposed to the situation 
now. At the moment the semantics of UML is described in terms of natural language. Sentences in 
natural language can be ambiguous. This is the ambiguity that the 2uworks group wants to get rid of.


Dr. Hubert Baumeister, Institut für Informatik, Universität München
phone (x49-89)2180-9375  * fax -9175

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