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Re: LANG: owl:ontology

From: Jeff Heflin <heflin@cse.lehigh.edu>
Date: Thu, 19 Sep 2002 16:51:22 -0400
Message-ID: <3D8A38CA.DF3C491@cse.lehigh.edu>
To: Raphael Volz <volz@aifb.uni-karlsruhe.de>
CC: Webont <www-webont-wg@w3.org>

Hi Raphael,

For those of us who don't have time to read the XInclude spec, could you
explain how it would solve the problem of when two ontology documents
have different default namespaces? Usually, these are expressed in the
rdf:RDF tag, but you omit one ontology's RDF tag in your approach. It
seems to me that the imported stuff would get the wrong default
namespace.

Jeff


Raphael Volz wrote:
> 
> Hi -
> 
> actually Peter is right, since some thing referred to as
> object in a <x, owl:subclassof, y), i.e. y is automagically
> made a class in OWL (by entailment). The only the thing we
> loose is everything else that is said about y in document 1.
> 
> I have an alternative proposal for doing the owl:imports,
> which happens to be compatibel with RDF, and uses standard
> W3C technologies, namely XInclude http://www.w3.org/TR/xinclude/, which is
> the candidate
> recommendation for doing inclusion for arbitrary XML.
> 
> It would look like this
> 
> document 1:
> -----------
> <rdf:RDF>
> 
>         <!-- Document metadata -->
>         <owl:Ontology rdf:about="">
>         ...
>         </owl:Ontology>
> 
>         <!-- classes -->
>         <owl:Class rdf:ID="foo" />
>         ...
>         <!-- properties -->
>         <owl:Class rdf:ID="bar" />
>         ...
> </rdf:RDF>
> 
> document2:
> ----------
> <rdf:RDF>
>         <!-- Inclusion -->
>         <xi:include xi:href="document1#xpointer(/rdf:RDF/*)"/>
> 
>         <!-- Document metadata -->
>         <owl:Ontology rdf:about="">
>         ...
>         </owl:Ontology>
> 
>         <!-- classes -->
>         <owl:Class rdf:ID="foo2" />
>         ...
>         <!-- properties -->
>         <owl:Class rdf:ID="bar2" />
>         ...
> </rdf:RDF>
> 
> result would be
> 
> <rdf:RDF>
>         <!-- Included information -->
>                 <!-- Document metadata -->
>         <owl:Ontology rdf:about="file:/document1">
>         ...
>         </owl:Ontology>
> 
>         <!-- classes -->
>         <owl:Class rdf:ID="file:/document1#foo" />
>         ...
>         <!-- properties -->
>         <owl:Class rdf:ID="file:/document2/#bar" />
> 
>         <!-- Document metadata -->
>         <owl:Ontology about="">
>         ...
>         </owl:Ontology>
> 
>         <!-- classes -->
>         <owl:Class rdf:ID="foo2" />
>         ...
>         <!-- properties -->
>         <owl:Class rdf:ID="bar2" /><rdf:RDF>
>         ...
> </rdf:RDF>
> 
> The xi:include is valid RDF via a combination of the
> many convenience syntaxes for RDF and turns out to be
> two triples, namely
> 
>         <xi:include xi:href="document1#xpointer(/rdf:RDF/*)"/>
> -->
> (@anonymous, rdf:type, xi:include)
> (@anonymous, xi:href, "document1#xpointer(/rdf:RDF/*")
> 
> The usage of XPointer does not really impose any realistic
> restriction on implementation, since the XPAth used is
> always the same, namely give me all children elements of rdf:RDF.
> 
> Of course, there are alternative, equivalent XPath expressions that
> can say the same, but they are usually more un-intuitive.
> 
> The semantics of the operation is a merge of the XML Info Sets of the
> document and the addressed document fragments.
> 
> If we restrict our self to simple inclusion and specify the semantics
> as a merger of the RDF graphs, then this operation would exactly do
> that.
> 
> Raphael
> 
> PS: I tried to send that yesterday, but apparently my emails did not
> arrive...
Received on Thursday, 19 September 2002 16:51:25 GMT

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