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FW: Global concept identification and reference

From: Miles, AJ (Alistair) <A.J.Miles@rl.ac.uk>
Date: Wed, 10 Nov 2004 12:15:34 -0000
Message-ID: <350DC7048372D31197F200902773DF4C05E50D0F@exchange11.rl.ac.uk>
To: "'public-esw-thes@w3.org'" <public-esw-thes@w3.org>

Fwded further discussion with Leonard ...


-----Original Message-----
From: Miles, AJ (Alistair) 
Sent: 08 November 2004 11:22
To: 'Leonard Will'
Subject: RE: Global concept identification and reference


Hi Leonard,

> Perhaps I am misunderstanding what you are trying to do, so 
> perhaps we 
> should clarify first whether
> 
> (a) you are seeking a single definition for each concept that can be 
> accepted and applied universally, so that you can build 
> useful semantic 
> networks incorporating that concept
> 

No.  

> or
> 
> (b) you just wish to have a way of pointing unambiguously to 
> a specific 
> definition of a concept within a specific controlled vocabulary.
>

Yes.

> I thought 
> from previous discussions that options were proposed for referring to 
> the two elements above by giving a URL for the thesaurus 
> followed by a # 
> or a / and the descriptor. That seems a reasonable way of 
> combining the 
> two properties required.
> 

Yes this the best option.  If the authority owning the thesaurus decides to
do this, and then publishes these URIs, then that's all well and good.  

But if the thesaurus has no URIs, and if the authority owning the thesaurus
no longer exists, or doesn't want to assign URIs, then if you want to
publish and use an RDF description of this thesaurus, what do you do?  

One option is to make up and use your own URIs.  Here it is generally
considered bad practise to make up URIs using a namespace that you don't
own.  So then, it is possible that a number of RDF descriptions of the same
thesaurus could get published on the semantic web, each using different URIs
for the same concepts.

This is similar to the problem with using URIs to identify people.  

This isn't a serious problem.  The machinery exists to cope with this, via
the owl:sameAs predicate.  (I.e. you can say 'the thing with URI X is the
same thing as the thing with URI Y').

However, I was thinking that, as an alternative, we could offer a
recommendation to use 'reference by description' when creating RDF
descriptions of *existing thesauri without published URIs*, rather than
inventing new ones.

Reference by description means rather than saying ...

<rdf:RDF>
  <skos:Concept rdf:about="[someURI]"/>
</rdf:RDF>

... you say ...

<rdf:RDF>
  <skos:Concept>
    <skos:prefLabel>bananas</skos:prefLabel>
    <skos:inScheme>
      <skos:ConceptScheme>
        <foaf:homepage rdf:resource="[someURL]"/>
      </skos:ConceptScheme>
    </skos:inScheme>
  </skos:Concept>
</rdf:RDF>

... which to convert to human speak, means that, rather than referring to
...

'the concept with URI [someURI]'

... we refer instead to ...

'the concept with preferred label 'bananas' from the concept scheme with
homepage at [someURL]'.

This skirts around the problem of having to assign URIs to things, and tries
to exploit traditional and existing methods of identification, which it is
possible to do in RDF.

> Sorry again, but I don't know how a URI becomes "official" - can you 
> enlighten me?
> 

All I meant by 'official' was that the authority owning a thesaurus has said
'use this URI for this concept' ... so in a sense, the URI has been
'endorsed' by the owning authority.

> When you talk about "multiple published URIs for the same concept" do 
> you mean "different ways of pointing to the same concept 
> within the same 
> thesaurus" or "pointers to concepts within different thesauri that 
> appear to have more or less the same scope"?

The former.

Do you mind if I forward this email to public-esw-thes?  Seems like it might
be useful.

Yours,

Alistair.




> 
> Regards
> 
> Leonard
> 
> -- 
> Willpower Information       (Partners: Dr Leonard D Will, 
> Sheena E Will)
> Information Management Consultants              Tel: +44 
> (0)20 8372 0092
> 27 Calshot Way, Enfield, Middlesex EN2 7BQ, UK. Fax: +44 
> (0)870 051 7276
> L.Will@Willpowerinfo.co.uk               
> Sheena.Will@Willpowerinfo.co.uk
> ---------------- <URL:http://www.willpowerinfo.co.uk/> 
> -----------------
> 
Received on Wednesday, 10 November 2004 12:16:07 GMT

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