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Re: question concerning collections

From: Mark van Assem <mark@few.vu.nl>
Date: Mon, 29 May 2006 13:43:34 +0300
Message-ID: <447AD056.6080400@few.vu.nl>
To: Paul Hermans <paul.hermans@amplexor.com>
CC: public-esw-thes@w3.org

Hi Paul,

The SKOS Core Guide [1] says:

"Note that in the example above the collection was defined as a blank 
node, i.e. no URI was allocated. URIs may be allocated to collections, 
but usually this is not necessary."

So the first answer to your question is 'yes, it is possible and it is 
allowed'.

However, I think the wording above should be stronger, stating that it 
is recommended NOT to give a URI for a collection. Collections are used 
to represent node labels, and node labels should not be used for 
indexing. Therefore annotators should not be tempted to use them anyway, 
simply because a URI is available for them.

Again quoting [1]:

'There is consensus that a 'node label' does not represent a label for a 
concept in its own right, and therefore correctly modelling this kind of 
structure in RDF requires careful consideration.'

Cheers,
Mark.

[1]http://www.w3.org/TR/swbp-skos-core-guide/#seccollections




Paul Hermans wrote:
> In the SKOS core guide I do find following example :
> 
> <rdf:RDF
>   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>   xmlns:skos="http://www.w3.org/2004/02/skos/core#"
>   xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
>   
>   <skos:Concept rdf:about="http://www.example.com/concepts#milk">
>     <skos:prefLabel>milk</skos:prefLabel>
>     <skos:narrower>
>       <skos:Collection>
>         <rdfs:label>milk by source animal</rdfs:label>
>         <skos:member rdf:resource="http://www.example.com/concepts#buffalomilk"/>
>         <skos:member rdf:resource="http://www.example.com/concepts#cowmilk"/>
>         <skos:member rdf:resource="http://www.example.com/concepts#goatmilk"/>
>         <skos:member rdf:resource="http://www.example.com/concepts#sheepmilk"/>
>       </skos:Collection>
>     </skos:narrower>
>   </skos:Concept>
> </rdf:RDF>
> 
> Where in this case Collection is within the narrower element as a blank node.
> 
> I suppose I can do the same using a node with a URI as follows.
> 
> <rdf:RDF
>   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>   xmlns:skos="http://www.w3.org/2004/02/skos/core#"
>   xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
>   
>   <skos:Concept rdf:about="http://www.example.com/concepts#milk">
>     <skos:prefLabel>milk</skos:prefLabel>
>     <skos:narrower rdf:resource="http://www.example.com/collections#milkbyanimal"/>
>   </skos:Concept>
>   
>   <skos:Collection rdf:about="http://www.example.com/collections#milkbyanimal">
>         <rdfs:label>milk by source animal</rdfs:label>
>         <skos:member rdf:resource="http://www.example.com/concepts#buffalomilk"/>
>         <skos:member rdf:resource="http://www.example.com/concepts#cowmilk"/>
>         <skos:member rdf:resource="http://www.example.com/concepts#goatmilk"/>
>         <skos:member rdf:resource="http://www.example.com/concepts#sheepmilk"/>
>  </skos:Collection>
> 
> </rdf:RDF>
> 
> 
> I just want to check since someone told me this can and may not be done according to the SKOS spec.
> 
> Regards,
> 
> 
> Paul
> 

-- 
  Mark F.J. van Assem - Vrije Universiteit Amsterdam
        markREMOVE@cs.vu.nl - http://www.cs.vu.nl/~mark
Received on Monday, 29 May 2006 10:45:13 GMT

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