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Re: Transport XML meta data as well as RDF?

From: Phil Archer <parcher@icra.org>
Date: Wed, 18 Jun 2008 15:11:14 +0100
Message-ID: <48591782.4010302@icra.org>
To: Public POWDER <public-powderwg@w3.org>



Smith, Kevin, (R&D) VF-Group wrote:
> Hmmm...so does that mean that any descriptors more complex than a
> triple(s) are treated as 'xmldata'?
> 
> E.g. 
> <descriptorset>
>    <ex:palette type="1">
> 	<ex:colour>red</ex:colour>	
> 	<ex:luminance>50</ex:luminance>	
>    </ex:palette>
> </descriptorset> 
> 
> ? If so, can we simply say that where the descriptor contains a triple
> such as <> ex:color red, then map this to 
> 
>        <owl:onProperty rdf:resource="http://example.org/vocab#colour" />
>        <owl:hasValue>red</owl:hasValue>
> 
> but, if the descriptor is more complex, then map this to 
> 
>        <owl:onProperty
> rdf:resource="http://www.w3.org/2007/05/powder-s#xmldata" />
>        <owl:hasValue>
> 	  <!-- add XML verbatim-->
> 	 </owl:hasValue>

Not quite no. This:

<descriptorset>
   <ex:colour>
     <ex:Red>
       <ex:hex>ff0000</ex:hex>
     </ex:Red>
   </ex:colour>
</descriptorset>

gets transformed into this:

<owl:Class rdf:nodeID="descriptorset_1">
   <owl:intersectionOf rdf:parseType="Collection">
     <owl:Restriction>
       <owl:onProperty rdf:resource="http://example.org/vocab#colour"/>
       <owl:hasValue>
         <ex:Red>
           <ex:hex>ff0000</ex:hex>
         </ex:Red>
       </owl:hasValue>
     </owl:Restriction>
   </owl:intersectionOf>
</owl:Class>

(see example 3-13 in the soon to be published Formal semantics doc). So 
the property is restricted in the OWL sense of the word and its value 
can be anything.

That's not the same as a (new) xmldata element where the property wouold 
always be in the POWDER-S namespace and the value would be whatever 
arbitrary XML was in there. Actually Stasinos has reminded me that you 
should add rdf:parseType="Literal" to the owl:hasValue element (see 
http://www.w3.org/TR/rdf-primer/#xmlliterals)

> 
> The complex descriptors can be easily spotted with the following XPATH:
> 
> count(descendant::*) >1 
> 
> Just a bit wary of having a wrapper element called <xmldata> if we can
> determine that implicitly.

I don't like implicit things either as it can easily go wrong, hence I'd 
prefer quite separate elements for XML meta data and RDF stuff (if we do 
this at all).

P

> 
> 
> -----Original Message-----
> From: public-powderwg-request@w3.org
> [mailto:public-powderwg-request@w3.org] On Behalf Of Phil Archer
> Sent: 18 June 2008 14:13
> To: Public POWDER
> Subject: Re: Transport XML meta data as well as RDF?
> 
> 
> Yes, that's fine for POWDER and in terms of the XML schema but what will
> the transform make of it? This...
> 
> <descriptorset>
>    <ex:colour>red</ex:colour>
> </descriptorset>
> 
> ends up as
> 
> <owl:Class rdf:nodeID="descriptorset_1">
>    <owl:intersectionOf rdf:parseType="Collection">
>      <owl:Restriction>
>        <owl:onProperty rdf:resource="http://example.org/vocab#colour" />
>        <owl:hasValue>red</owl:hasValue>
>      </owl:Restriction>
>    </owl:intersectionOf>
> </owl:Class>
> 
> and there are rules for things like rdf:resource and all that so I think
> we'd need an explicit element type so that the GRDDL can turn your
> POWDER example into
> 
> <owl:Class rdf:nodeID="descriptorset_1">
>    <owl:intersectionOf rdf:parseType="Collection">
>      <owl:Restriction>
>        <owl:onProperty
> rdf:resource="http://www.w3.org/2007/05/powder-s#xmldata" />
>        <owl:hasValue>
> <!--
> UKOLN xml quoted here verbaitm
> -->
> 
> </owl:hasValue>
>      </owl:Restriction>
>    </owl:intersectionOf>
> </owl:Class>
> 
> (we'd need to create that 'xmldata' element in POWDER and its term in 
> POWDER-S).
> 
> Phil.
> 
> Smith, Kevin, (R&D) VF-Group wrote:
>> HI Phil,
>>
>> You can already include that metadata block in a DescriptorSet as
>> regards the XML schema, so would that suffice?
>>
>> Cheers
>> Kev
>>
>> E.g.:
>>
>> <?xml version="1.0" encoding="UTF-8"?>
>> <powder xmlns="http://www.w3.org/2007/05/powder"
>> xmlns:dc="http://dublincore.org/schemas/xmls/qdc/dc.xsd"
>> xmlns:dcterms="http://dublincore.org/schemas/xmls/qdc/dcterms.xsd"
>> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>> xsi:schemaLocation="http://www.w3.org/2007/05/powder wdr.xsd">
>> 	<attribution>
>> 	
>>
> <maker><dc:creator>http://people.example.com/kevin</dc:creator></maker>
>> 	</attribution>
>> 	<dr>
>> 		<iriset>
>> 	
>> <includeregex>http://ukoln.ac.uk/*</includeregex>
>> 		</iriset>
>> 		<descriptorset>
>> 			<metadata xmlns="http://example.org/myapp/">
>> 			   <dc:title>UKOLN</dc:title>
>> 			   <dc:description>
>> 				 UKOLN is a national focus of expertise
>> in digital information
>> 				 management. It provides policy,
>> research and awareness services
>> 				 to the UK library, information and
>> cultural heritage communities.
>> 				 UKOLN is based at the University of
>> Bath.
>> 			   </dc:description>
>> 			   <dc:publisher>UKOLN, University of
>> Bath</dc:publisher>
>> 	
>> <dc:identifier>http://www.ukoln.ac.uk/</dc:identifier>
>> 		</metadata>
>> 		</descriptorset>
>> 	</dr>
>> </powder>
>>
>> -----Original Message-----
>> From: public-powderwg-request@w3.org
>> [mailto:public-powderwg-request@w3.org] On Behalf Of Phil Archer
>> Sent: 18 June 2008 12:14
>> To: Public POWDER
>> Subject: Transport XML meta data as well as RDF?
>>
>>
>> I've just had an interesting conversation with Karen Van Godtsenhoven
>> and Patrick Hochstenbach at the University of Gent who are running a
>> project called DRIVER [1] - which is concerned with Open Access
>> scientific publications. One question raised was whether POWDER could
>> transport XML meta elements as well as RDF. Er... well, it's designed
> to
>> transport RDF but I wonder how difficult it would be to add support
> for
>> transporting XML that doesn't get treated as RDF? (there are some very
>> well established XML-based metadata systems).
>>
>> To try and work through an example I looked at the Dublin Core XML
>> implementation guide [2], example 4.3 of which is
>>
>> <metadata
>>    xmlns="http://example.org/myapp/"
>>    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>>    xsi:schemaLocation="http://example.org/myapp/
>> http://example.org/myapp/schema.xsd"
>>    xmlns:dc="http://purl.org/dc/elements/1.1/">
>>
>>    <dc:title>UKOLN</dc:title>
>>    <dc:description>
>>      UKOLN is a national focus of expertise in digital information
>>      management. It provides policy, research and awareness services
>>      to the UK library, information and cultural heritage communities.
>>      UKOLN is based at the University of Bath.
>>    </dc:description>
>>    <dc:publisher>UKOLN, University of Bath</dc:publisher>
>>    <dc:identifier>http://www.ukoln.ac.uk/</dc:identifier>
>> </metadata>
>>
>> Hmmm... so we have an arbitrary bit of XML that provides data about,
> in
>> this case, UKOLN. POWDER could be useful in associating this data with
>> "everything on ukoln.ac.uk" ?
>>
>> I think all we'd need to do would be to define a new element for our
> DRs
>> of, say, xmldata, and treat it more or less the same as we do tagset
> and
>> descriptorset in that you can have multiple instances of them but you
>> must have at least one of tagset, descriptorset or xmldata for the DR
> to
>> be valid. In POWDER-S there would be a class with a property that had
>> the XML chunk as its value (RDF has specific support for transporting
>> XML as the value of a property).
>>
>> Something to talk about on our next telecon?
>>
>> Phil.
>>
>>
>> [1] http://www.driver-repository.be/
>> [2] http://dublincore.org/documents/dc-xml-guidelines/
>>
Received on Wednesday, 18 June 2008 14:12:05 GMT

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