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Re: POWDER-S Schema - revised version

From: Phil Archer <parcher@fosi.org>
Date: Thu, 02 Oct 2008 14:56:04 +0100
Message-ID: <48E4D2F4.6020809@fosi.org>
To: Public POWDER <public-powderwg@w3.org>

Andrea, Stasinos,

Thank you for pursuing this, I can see that it is not simple - but I'm 
hoping that between you it's possible to decide on a way forward. For me 
the important things are:

1. At the moment, FOAF is the vocab that a lot of people use and 
therefore we should support it. foaf:Agent must be a possible object of 
wdrs:issuedby.

2. dcterms:Agent has greater formal long term stability and we should 
therefore make it possible to use that as the object of wdrs:issuedby as 
well.

3. We should not make any statement that in any way affects the 
semantics of either of those external vocabularies.

4. IMO, we should /only/ support those two, but, this may not be best 
practice. If we make it so that other hypothetical Agent classes can be 
used, I don't think anyone will object. In general, the fewer 
restrictions that apply to a vocab term the better.

5. We always used to use rdf:Description to describe the POWDER-S doc. 
We changed to owl:Ontology in response to a comment from Ivan. If the 
present discussion means that we should go back and revert to 
rdf:Description, OK, we can do that. As I recall, it was a suggestion 
from Ivan, no more.

6. Kev needs to know the outcome of the discussion so he can complete 
the XSLT ASAP

7. You - Andrea and Stasinos - have the insight and understanding to 
solve this. No one's going to argue with you and we'd be most grateful 
if you could sort this out for us!

8. We can make minor amendments to any of our docs in this regard - 
we've flagged it as an issue, so please don't feel too constrained by 
what is already published.

9. We can take a resolution on Monday but it if there's a clear path 
forwards by then, terrific!

And again, thank you for putting so much thought into this - it proves 
that POWDER is a strong, well thought-out protocol.

Phil.


Andrea Perego wrote:
> 
> 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 13:56:36 GMT

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