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Re: POWDER-S Schema - revised version

From: Andrea Perego <andrea.perego@uninsubria.it>
Date: Thu, 02 Oct 2008 10:22:27 +0200
Message-ID: <48E484C3.5040206@uninsubria.it>
To: Public POWDER <public-powderwg@w3.org>

Hi, Phil.

> [snip]
> 
> As you'll appreciate, there are some aspects of this that I'm not able 
> to fully understand, however, I do get the thrust of what you're saying. 
> Let's test that... We could define wdrs:issuedby as an owl:annotation 
> property thus
> 
> <owl:AnnotationProperty rdf:about="#issuedby">  <rdfs:range>
>     <owl:Class>
>       <owl:unionOf rdf:parseType="Collection">
>         <owl:Class rdf:about="&dcterms;creator"/>
>         <owl:Class rdf:about="&foaf;maker"/>
>       </owl:unionOf>
>      </owl:Class>
>  </rdfs:range>
> </owl:AnnotationProperty>

Unfortunately, this is not allowed in OWL DL. Quoting from [1]:

[[
Annotation properties must not be used in property axioms. Thus, in OWL 
DL one cannot define subproperties or domain/range constraints for 
annotation properties.
]]

> [snip]
> 
> I think I favour the slightly more restrictive approach since we want to 
> make it clear what people are expected to do when they create POWDER 
> docs. We have a lot of flexibility in the way IRI sets and descriptor 
> sets are created - it's the attribution bit that we're talking about 
> here and we've deliberately been much more prescriptive as this is the 
> basis of any trust system around POWDER.

I agree. However, based on what Stasinos has said about the owl:Ontology 
and OWL DL issues, I cannot see a way out. If POWDER-S documents are 
ontologies, it is quite complicate to map wdrs:issuedby to 
dcterms:creator and/or foaf:maker, unless we move to OWL Full. So, I 
agree with Stasinos that  options (B3-A1) or (B3-A1a) are the safest 
solutions.

BTW, note that this does not apply to POWDER (XML) documents. They are 
not ontologies. So, we can use wdrs:Document to publish in RDF a list of 
POWDER documents, possibly along with their attribution. E.g.:

<rdf:RDF ...>
   <wdrs:Document rdf:about="http://www.example.org/powder1.xml">
     <foaf:maker rdf:resource="http://www.example.org/foaf.rdf#me" />
   </wdrs:Document>
   <wdrs:Document rdf:about="http://www.example.org/powder2.xml">
     <foaf:maker rdf:resource="http://www.example.org/foaf.rdf#you" />
   </wdrs:Document>
   <wdrs:Document rdf:about="http://www.example.org/powder3.xml" />
   <wdrs:Document rdf:about="http://www.example.org/powder4.xml" />
</rdf:RDF>

Of course, wdrs:Document must be redefined according to Stasinos's comments.

Andrea


[1]http://www.w3.org/TR/owl-ref/#Annotations
Received on Thursday, 2 October 2008 08:23:09 GMT

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