From: Rocco Caputo
> [EMAIL PROTECTED] wrote:
> > 
> > So we should talk about the semantic model. Illustatring
> > this with notations might seem useful, but as we
> > experienced in this thread it really produces
> > misunderstandings. So we will have to give
> > specifications. Which leads us to the UML specification, 
> > again. And this is what I suggest, reading the UML specs 
> > and discussing if (and how) we have to adjust or 
> > extend it to fit POE.
> >
> > As this might require too much time, reading tutorials
> > or introductions would be enough as well to be able to
> > know what is being talked about.
> >
> > The UML specs can be found on www.omg.org/uml (can't 
> > give a direct url, get no connection atm). If other
> > people find good introductions/tutorials it might be 
> > helpful to post the URLs here.
> 
> I have spent the better part of the weekend and Monday
> researching the UML.  I still don't know enough to discuss
> it, but I have been avoiding reading the specification
> directly.

AFAIK, the Uml is still a modelling language and not yet a
programming language. So while the recently approved "Action
Semantics" (http://cgi.omg.org/docs/ad/01-03-01.pdf) gives a
specification for communicating state. It still doesn't give
us the textual notation we can use with Perl.

I gather that Rocco Caputo would prefer a textual notation
that looks like Perl. Whereas torvald is recommending XMI. 

While XMI is adequate to the task, it isn't for humans. So
there's no way perl programmers are going to inline XMI in
their code. They might however consider something like HUTN.
HUTN stands for Human-Usable Textual Notation, and is based
on XMI. In fact it is round trip mappable between MOF (Meta-
Object Facility) and XMI... and more importantly you can
actually read it.

HUTN
slides: http://www.dstc.edu.au/Research/Projects/Pegamento/hutn/edoc2001.ppt
spec:   http://cgi.omg.org/cgi-bin/doc?ad/02-03-02

Both the slides and the proposal (sections 2.6-2.8) show
examples of a MOF model represented in XMI and HUTN.

However, HUTN seems oriented toward describing objects... 
I suppose XMI is too for that matter. I haven't yet read
enough to figure out how someone would model states in HUTN.
Still, it's food for thought... and might help prevent the
tendency to reinvent wheels.


While I've been reading up on UML, XMI, HUTN, etc. I ran
across a number of papers which might be of interest.

A Note on Semantics (with an Emphasis on UML):
http://citeseer.nj.nec.com/296632.html

State Based Service Description:
http://citeseer.nj.nec.com/paech96state.html

The Architecture Of A Uml Virtual Machine (2001):
http://citeseer.nj.nec.com/493968.html

Now I just have to find the time to digest it all... ;)

--
Garrett Goebel
IS Development Specialist

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