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Re: OWL Lite semantics

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 09 Dec 2002 09:01:12 -0500 (EST)
Message-Id: <20021209.090112.50898237.pfps@research.bell-labs.com>
To: hendler@cs.umd.edu
Cc: horrocks@cs.man.ac.uk, jjc@hplb.hpl.hp.com, www-webont-wg@w3.org

From: Jim Hendler <hendler@cs.umd.edu>
Subject: Re: OWL Lite semantics
Date: Mon, 9 Dec 2002 08:34:03 -0500

> (This message follows those by Peter, Pat and Ian)
> 
> The formalists heard from, here's my "scruffy" response
> 
> 
> EASE of implementation:
> 
> What Jeremy suggests is quite appealing to me because there is good 
> evidence that it IS easier to implement -- in fact, the code foe a 
> program with a considerable subset 
> of Jeremy's OWL Lite proposal can 
> be found in the 1987 AI textbook "AI Programming" by Charniak, 
> Riesbeck, McDermott and Meehan *.

Which is also a subset of the current OWL Lite semantics, so no advantage
has been shown.

> Current implementations:
> 
> In fact, a great many implemented AI systems use essentially what 
> Jeremy proposes -- these are the systems that gre primarily from the 
> frame systems (remember that discussion from very early in our 
> group??)  - examples of a number of these tools can be found in the 
> 1999 "Ontology Management Workshop" that AAAI ran [1].

Please point to at least one.  The reference you provide is only to the
table of contents for the workshop proceedings.  Further, it appears to me
that the workshop is not about ontology reasoners at all.  Certainly there
is no obvious relationship between any of the paper titles and existing
ontology reasoners.  The paper that I know best from that workshop is about
a tool for merging ontologies, and not at all about reasoning in an
ontology or even reasoning in multiple ontologies.

> In these systems, 

Which systems?

> the prevailing use has NOT been classification, and 
> I'd argue that most of the "only if"s grow out of the need for 
> classifiers (this is a simplification, I admit, but would take much 
> more bandwdith to be specific).  However, in many cases people build 
> the ontology separately from classification (thus not needing most of 
> the class reasoning in OWL).

Are you arguing that we should give up on the semantics of OWL and the
semantics of RDF?  Are you arguing that classification is different from
any of the other reasoning activities that are needed for OWL (Lite)?  In
particular, are you arguing that determining whether an OWL (Lite) ontology
is consistent is any easier than classification?

> For example, in all the tools built by my current group [2], we 
> assume that either we are importing an ontology from elsewhere, or 
> that someone is extending one by adding classes and properties to 
> existing places in an ontology.  In these cases, we are able to 
> support many of the "if" entailments but not the only-ifs (c.f. my 
> mexican restaurant example summarized by Deb in [3])

If you are only supporting many, not all, of the ``if'' entailments, then
how are Jeremy's changes going to help matters?

> In short, under Jeremy's subset many current systems will already be 
> able to handle OWL Lite, under our current definition they can't. 
> (btw, everyone of the systems that I know of include HAS-VALUE, but 
> only with the "if" semantics)

Please provide an example of a system that can handle (all of) Jeremy's
semantics but that cannot handle (all of) the current semantics.

> SEMANTICS:
> 
> Pat and Ian claim Jeremy's proposal is somehow significantly 
> different semantically than the current one.  This confuses me - what 
> Jeremy proposes is still a proper subset of OWL DL, so I'm not sure 
> why this one is so different from our current as to make trouble - 
> can one of you explain?
> 
> -------------------
> * - sorry, this book predates the web and I can't find the code on the web.
> [1] http://www.aaai.org/Press/Reports/Workshops/ws-99-13.html
> [2] http://www.mindswap.org/downloads.shtml
> [3] http://lists.w3.org/Archives/Public/www-webont-wg/2002Dec/0038.html
> -- 
> 
> Professor James Hendler				  hendler@cs.umd.edu
> Director, Semantic Web and Agent Technologies	  301-405-2696
> Maryland Information and Network Dynamics Lab.	  301-405-6707 (Fax)
> Univ of Maryland, College Park, MD 20742	  240-731-3822 (Cell)
> http://www.cs.umd.edu/users/hendler


peter
Received on Monday, 9 December 2002 09:01:44 GMT

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