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Re: URIs : How to find the ontologies behind them

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 10 Apr 2003 09:45:31 -0400 (EDT)
Message-Id: <20030410.094531.130347639.pfps@research.bell-labs.com>
To: Patrick.Stickler@nokia.com
Cc: www-rdf-interest@w3.org

From: <Patrick.Stickler@nokia.com>
Subject: RE: URIs : How to find the ontologies behind them
Date: Thu, 10 Apr 2003 09:40:56 +0300

> 
> > > I'm primarily interested in the 'when the SW gets going' 
> > case (it's about
> > > time we get it going, no? ;).  You seem to be saying that a 
> > best practice
> > > would be to put the OWL describing the resource in the 
> > place that the URI of
> > > the resource refers to.
> > 
> > Not necessarily in that exact place.  However, most RDF URI 
> > references have
> > fragment identifiers, so it would be possible for example to place
> > information about http://foo.ex/bar#bax in a document located at
> > http://foo.ex/bar.  
> 
> Sorry. Unfortunately, no.
> 
> RDF fragment IDs do not work in exactly the same way as XML ID's.
> 
> You can describe the resource http://foo.ex/bar#bax in a dozen
> different RDF/XML instances, none of which are http://foo.ex/bar.
> And in all cases, you need not use rdf:ID ever. So even if
> http://foo.ex/bar#bax is defined by http://foo.ex/bar, that
> doesn't guaruntee that rdf:ID="bax" occurs anywhere in that
> RDF/XML instance.

So?  Does this mean that what I said is not possible?

> And there is no assertion that http://foo.ex/bar#bax relates to
> a particular XML *element* in an RDF/XML instance having an
> rdf:ID="bax" even if the parser will map such an rdf:ID value
> to a URI based on an xml:base separated by '#'. rdf:ID is
> not defined as an XML ID attribute.

Agreed, but, again, what does this have to do with what I said?

> And in fact, though there should only be one occurrence of a given
> rdf:ID value for an xml:base scope, one can have descriptions using
> both rdf:ID and rdf:about about the very same resource in the same
> RDF/XML instance.

Agreed, but, again, what does this have to do with what I said?

> One should not think of URIrefs as working in RDF the same way
> as they do in an HTML browser. They don't.

Agreed, but, again, what does this have to do with what I said?
 
> Thus, just as one cannot reliably get to a namespace document
> from a URI, one cannot get to a definitive RDF/XML instance from
> a URIref.

Agreed, but, again, what does this have to do with what I said?

> *** TAKE NOTE: URIrefs are *fully opaque* in an RDF graph and SW
> *** agents operating on RDF expressed knowledge should not attempt
> *** to parse URIrefs to infer any relationships between the resource
> *** denoted by the URIref and any other resource that might share
> *** some intersection of some character sequence with the URIref. 

Aaah, but I'm not saying that this is part of RDF.  I'm just saying that it
is possible (in some unspecified, and maybe never formally specified,
manner) to place information about an RDF URI reference at a particular
URI.

> The SW deals with RDF graphs, not RDF/XML instances, so
> one should not be concerned with aspects of the XML serialization 
> when requesting knowledge from a knowledge base. And looking
> at URI vs. URIref or URI vs. namespace relations (neither of 
> which can be reliably utilized) is the wrong way to go.

Why not?  Many RDF URI references can be so decomposed.  

I'm not suggesting that this be part of RDF per se.  

> The SW architecture should provide for a standardized means by
> which, given a URIref, one can inquire from the web authority
> of the URIref (presuming there is one) for a description of 
> the resource denoted by the URIref.
> 
> One can also inquire from various registries or other sources
> for non-web-authoritative descriptions of the resource, allowing
> for one to syndicate various views and opinions of the resource.

Sure why not?

It may be that there is a better way than the one I described.  However,
what is wrong with what I said?

> URIQA will provide for both.
> 
> > ... I think that the
> > relationship between ontologies and URI references is many to 
> > many (and
> > many to many in interesting ways).
> 
> Agreed.
> 
> Patrick

peter
Received on Thursday, 10 April 2003 09:45:44 GMT

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