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Re: LANG: owl:import - Two Proposals

From: Jim Hendler <hendler@cs.umd.edu>
Date: Wed, 2 Oct 2002 11:50:30 -0400
Message-Id: <p05111702b9c0c427338f@[]>
To: Jeff Heflin <heflin@cse.lehigh.edu>, Jonathan Borden <jonathan@openhealth.org>
Cc: WebOnt <www-webont-wg@w3.org>

>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

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 :->

>  >
>  > - 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

>  > [[
>>  - 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 :->)

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)
Received on Wednesday, 2 October 2002 11:50:47 UTC

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