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RE: SKOS 'concept schemes' and DCMI 'vocabulary encoding schemes'

From: Houghton,Andrew <houghtoa@oclc.org>
Date: Mon, 10 Oct 2005 15:19:59 -0400
Message-ID: <D53793AA582576458786FBE27899DB18013A54F8@OAEXCH2SERVER.oa.oclc.org>
To: "Pete Johnston" <p.johnston@ukoln.ac.uk>, "Miles, AJ \(Alistair\)" <A.J.Miles@rl.ac.uk>, <DC-RDF-TASKFORCE@jiscmail.ac.uk>
Cc: <public-esw-thes@w3.org>

> From: public-esw-thes-request@w3.org 
> [mailto:public-esw-thes-request@w3.org] On Behalf Of Pete Johnston
> Sent: 10 October, 2005 12:41
> To: 'Miles, AJ (Alistair)'; DC-RDF-TASKFORCE@jiscmail.ac.uk
> Cc: public-esw-thes@w3.org
> Subject: RE: SKOS 'concept schemes' and DCMI 'vocabulary 
> encoding schemes'
> 
> > Oh, another thought, the only way I can see 'Vocabulary Encoding 
> > Scheme' mapping to RDF as is, without changing the AM, is to model 
> > them as RDF datatypes.  I.e.:
> > 
> > <http://www.example.com/somedoc> dc:subject 
> > 'D08.586.682.075.400'^^dcterms:MESH.
> > 
> > Although I certainly can't claim to understand the finer 
> points of how 
> > an RDF datatype maps a set of literal values to resources, 
> the notion 
> > of a datatype in RDF seems to fit best with the notion of 
> 'encoding' 
> > as it is described in the DCMI AM.
> > 
> > Would it be possible to allow both e.g. ...

We had the need for using other subject encoding schemes with Dublin Core, other than the those listed by DCMI, e.g., DDC, LCSH, MESH, UDC.  In our discussion with Andy Powell and Stu Weibel they indicated that DCMI was not happy with subject encoding schemes since everytime you need a new one, you have to add it to the Dublin Core specification.  Last year we proposed an alternate, backward compatible, method for DCMI to deprecate the use of subject encoding schemes and allow any subject scheme to be specified via URI.  I'm not sure where or how far the proposal went.

Our proposal produced the same RDF graph structure as the following example, lifted from the DCMI document:

<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:dcterms="http://purl.org/dc/terms/"
>
  <rdf:Description>
    <dc:subject>
      <dcterms:MESH>
        <rdf:value>D08.586.682.075.400</rdf:value>
        <rdfs:label>Formate Dehydrogenase</rdfs:label>
      </dcterms:MESH>
    </dc:subject>
  </rdf:Description>
</rdf:RDF>

Basically, the above produces the following raw RDF:

<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:dcterms="http://purl.org/dc/terms/"
>
  <rdf:Description>
    <dc:subject>
      <rdf:Description>
        <rdf:type>http://purl.org/dc/terms/MESH</rdf:type>
        <rdf:value>D08.586.682.075.400</rdf:value>
        <rdfs:label>Formate Dehydrogenase</rdfs:label>
      </rdf:Description>
    </dc:subject>
  </rdf:Description>
</rdf:RDF>

Thus, you can deprecate the use of use of subject encoding schemes and allow new subject encoding schemes without having to add them to Dublin Core by changing the URL in rdf:type, for example GSAFD (a list of genre terms for drama and fiction):

<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
  xmlns:dc="http://purl.org/dc/elements/1.1/"
  xmlns:dcterms="http://purl.org/dc/terms/"
>
  <rdf:Description>
    <dc:subject>
      <rdf:Description>
        <rdf:type>info:kos/scheme/gsafd/20010920</rdf:type>
        <rdf:value>GSAFD000001</rdf:value>
        <rdfs:label>Adventure fiction</rdfs:label>
      </rdf:Description>
    </dc:subject>
  </rdf:Description>
</rdf:RDF>

Not sure whether this helps your situation or not...


> > Also, the pattern:
> >
> > <http://www.example.com/somedoc> dc:subject
> 'D08.586.682.075.400'^^dcterms:MESH.
> >
> > ... seems to also match closely the XML encoding of qualified DC,
> using xsi:type.
> 

The use of xsi:type for the XML encoding of qualified DC seems, to me, to be a hack and doesn't quite align with its intended purpose in XML schema.  Also, some XML parsers choke on anything in xsi:type that isn't a qualified XML schema type.


Andy.
Received on Monday, 10 October 2005 19:20:25 GMT

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