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Re: [OWL-S] arguments for PAI and PAC

From: Jeff Lansing <jeff@polexis.com>
Date: Wed, 27 Aug 2003 12:47:07 -0700
Message-ID: <3F4D0ABB.2000508@polexis.com>
To: "'www-ws@w3.org'" <www-ws@w3.org>

David Martin wrote:

> ...
> We don't normally model a car as the set of its parts, because we've 
> come to realize that it works better to use some other 
> representational mechanism for the "part-of" relationship.
> Similarly, we don't usually represent the class of, say, dogs, as the 
> set of "life-traces" of individual dogs, or the class of humans as the 
> set of "life-traces" of individual humans.  (Note that I'm not saying 
> we should never do these things; just that we don't usually find it 
> useful to do so.)
> I suppose the obvious rejoinder might be: in modeling processes we are 
> centrally concerned with behavior across time, so it *does* make sense 
> to think of a process as a class of executions (which we most often 
> call "execution traces" in our discussions).  And that thought is in 
> the spirit that initially motivated us to model processes in this 
> way.  But, at least in my view, experience has taught us that it's 
> more natural to think of a process, and an execution of the process, 
> as two different (though obviously very closely related) kinds of 
> things, and model the relationships in some other way than class 
> membership.
> Again, I can't give any "proof" that processes-as-classes doesn't 
> work.  I'm just making the pragmatic argument that it's too hard to 
> work with.  We're building an ontology, and in my view, if an ontology 
> doesn't reflect a natural way of thinking about a domain, it's not so 
> likely to be used.
> ...

As I understand it, this is a several-thousand-year-old debate, so any 
appeal to naturalness here can only be regarded with suspicion. A lot of 
people don't find abstract Forms to be so "natural", but that's 
essentially what you're stuck with, when you separate processes from 
sets of executions of processes.

Received on Wednesday, 27 August 2003 15:47:15 UTC

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