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Re: LANG: owl:import - Two Proposals

From: Jeff Heflin <heflin@cse.lehigh.edu>
Date: Thu, 03 Oct 2002 09:51:50 -0400
Message-ID: <3D9C4B76.6A129CA5@cse.lehigh.edu>
To: Jim Hendler <hendler@cs.umd.edu>
CC: WebOnt <www-webont-wg@w3.org>

Jim Hendler wrote:
> >
> >We can come up with all kinds of examples along this theme that lead to
> >nightmares for implementation (imagine where I import something that
> >then says that another property I have is actually a subclass of
> >imports, then I have to import a whole new set of things, which in turn
> >might have other subclasses of imports). That's why proposal 2 suggested
> >that anything that has imports as a subject or object be undefined.
> >However, if we do this, some tools might decide to do some inferences
> >based on it, others might do a different set of inferences and still
> >others might consider it invalid syntax. If people start relying on the
> >processing aspects of their favorite tools (which they tend to do, see
> >web pages and web browsers as a case in point), then we have reduced
> >interoperability by not saying what all valid syntactic constructs must
> >mean.
> jeff - I can't let this one go - you're confusing over control with
> interoperability.  We say "If you care about interop - use what is
> defined" if you have a better idea, and implement in the undefined
> space, and people start using it, then in version 2.0 your approach
> will likely be accepted (or if several approaches compete, a followon
> group will resolve).  Look at the history of the most used web
> language ever (HTML) - it's whole history is publish spec, people
> extend and it loses some interoperability in esxchange for new power,
> and then the next WG resolves and add features.  The original HTML is
> extremely simple compared to what we use now - and there are many
> variants around, but it seems to me it is a pretty successful
> language - heck, people even built ontologies in it :->

Maybe we're arguing semantics here, but it seems to me if someone builds
an ontology that only works if you use ToolVendor(TM)'s tool, then
you've lost interoperability. I could be mistaken here, but I had heard
that the W3C found it very frustrating that Netscape and Microsoft
created their own HTML tags, and that this was one of the motivations
for XML, so that people could develop their own tags in a somewhat
controlled manner.

> >  >
> >  > - The fact that an ontology's classes and properties do not occur
> >>  between the <Ontology> tags is unintuitive
> >>  ]]
> >>
> >>  Oh well. That's an artifact of the decision to use RDF, however we decided
> >>  to use RDF/XML at F2F 2.
> >
> >Sure this isn't a deal-breaker, but because of it, proposal #1 has the
> >advantage of us not having to constantly answer the question "So tell me
> >again why the contents of an ontology are described outside of the
> ><Ontology> tag?"
> Not sure I understand, reopening decisions isn't to be taken lightly

I don't see it as reopening the decision. The decision is pretty vague,
so I guess it comes down to a matter of interpretation.

> >  > [[
> >>  - The use of about="" to make statements about the enclosing document
> >>  seems like a hack. In particular is seems like we could be confusing the
> >>  notion of a document that describes an ontology and the concept of an
> >>  ontology itself.
> >>  ]]
> >
> >>  Maybe, but what is the functional significance of this, and what requires us
> >>  to use rdf:about=""?
> >>
> >
> >If we are using RDF triples for everything, then triples that say
> >something is of type owl:Ontology and that that something imports
> >something else need a subject. In particular, this subject should be the
> >same for all such triples that concern the same ontology. The use of
> >about="" is a quick and dirty way of saying "use the base URL of the
> >document, since this should at least be different from the URIs of other
> >ontologies." Once again, this isn't huge; so far it hasn't seemed to
> >cause significant problems in practice with DAML+OIL. However, it
> >contributes to the difference between a language with an elegant design
> >and one that appears to be cobbled together. Which I think is one of the
> >most important factors in acceptance.
> actually, given that my group cheated and never used rdf:id="" but
> instead put a name there - the ontology got assigned a proper URI,
> and we refer to that - but this was a non-normative use (which I hope
> will become normative in some future version, see above :->)
> [snip]
> --
> 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
Received on Thursday, 3 October 2002 09:51:57 UTC

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