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Re: LANG: syntactic version for imports (and other things)

From: Jeff Heflin <heflin@cse.lehigh.edu>
Date: Tue, 17 Sep 2002 13:33:41 -0400
Message-ID: <3D876775.7502556C@cse.lehigh.edu>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
CC: www-webont-wg@w3.org

"Peter F. Patel-Schneider" wrote:
> From: Jeff Heflin <heflin@cse.lehigh.edu>
> Subject: Re: LANG: syntactic version for imports (and other things)
> Date: Mon, 16 Sep 2002 17:59:02 -0400
> > "Peter F. Patel-Schneider" wrote:
> > >
> > > From: Jeff Heflin <heflin@cse.lehigh.edu>
> > > Subject: Re: LANG: syntactic version for imports (and other things)
> > > Date: Mon, 16 Sep 2002 10:06:27 -0400
> [...]
> > > > Also, I expected to see some account of the meaning of this construct.
> > > > You didn't like my entailment-based version, what would you suggest
> > > > instead?
> > >
> > > The meaning is the obvious one.  The contents of the imported ontology
> > > are considered to be part of the meaning of this ontology.
> >
> > I have to admit I am a bit suprised at this answer, especially since it
> > is coming from someone who normally holds semantic precision as
> > something of uptmost importance.
> The meaning is quite clear, and quite precise.
> > What are the "contents" of an ontology?
> An ontology is a document.  Its contents are the contents of the document.
> > Is it the RDF syntax? The triples? The abstract syntax?  The conditions
> > imposed on interpretations by the syntax?
> At the level of *syntax* it doesn't matter.  All you need to do is to take
> the document, in whatever form it is, and add it to the importing ontology,
> in whatever form *it* is.  Then the syntax-to-semantics mapping takes
> over.

But that's where it's NOT clear. What does it mean to "add a document to
an ontology?" If the documents are RDF/XML, you can't simply insert one
document into the next and expect it to work (as we've seen with the
iterations we've done on Mike Smith's approach). Clearly, the syntax
does matter. We can't just say "ignore the XML junk" because the WG has
made the decision that we must work in the RDF/XML world.

> > Do you agree with Mike Smith's
> > syntactic approach [1]?
> Sure, except that it runs afowl of XML junk.
> > If so, what about the issues I raised [2]?
> By treating the imported ontologies as separate documents, and doing the
> syntax-to-semantics translation in that context.  Actually only the XML/RDF
> to RDF graph needs to be done in context.  You could also duplicate the NS
> stuff on every top-level element in the included ontology.

Now this seems like we are getting somewhere.  Although it is still a
little vague (it sounds like two or three alternatives are described), I
think I hear you saying that one solution is to do inclusion at the
abstract syntax level. Note, that this is very different from Mike's
approach because he does the inclusion at the XML syntax level. It needs
to be fleshed out, but I think I see how you could go from an OWL RDF
document into a semantics that takes imports into account and does what
its supposed to. But don't get me wrong, I'm still not wild about it
because it seems that were specifying a procedure for computing meaning
as opposed to saying what the meaning is. It seems contrary to the whole
notion of model theoretic semantics.

> > And
> > finally, how is this "better" than my entailments based approach?
> Your approach requires a treatment of ontologies and imports in the
> semantics, which raises big issues that I don't want to have to handle in
> the semantics.

I have to admit, I still don't understand what the big issues in the
semantics are. 

> > One of
> > the problems we got into with DAML+OIL is we didn't say what imports
> > meant, and thus everybody interpreted it to mean whatever they felt
> > like.
> Well, I think that the problem was that we thought that it was obvious what
> a DAML+OIL ontology was, and thus what imports meant.
> > If we cannot be perfectly clear about its meaning in OWL then we
> > have failed.
> Well maybe not failed, but certainly we would not have a complete success.
> > Jeff
> >
> > [1] http://lists.w3.org/Archives/Public/www-webont-wg/2002Sep/0167.html
> > [2] http://lists.w3.org/Archives/Public/www-webont-wg/2002Sep/0197.html
> peter
Received on Tuesday, 17 September 2002 13:33:45 UTC

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