Re: Blank nodes for concepts.

Makes sense to me.

Might be worth adding an explanation to one of the docos, both technical (as
below) and non technical (implication - you can't add a new concept with the
same prefLabel as another concept in the same thesaurus)

Cheers

Steve
----- Original Message -----
From: "Miles, AJ (Alistair) " <A.J.Miles@rl.ac.uk>
To: <public-esw-thes@w3.org>
Sent: Thursday, February 05, 2004 6:03 PM
Subject: Blank nodes for concepts.


>
> Hi,
>
> A couple of people have picked up that in the examples in the documents
[1]
> [2] [3] I've encoded concepts as blank nodes, without URIs.  This email
> addresses why I chose to do that.
>
> My thinking is as follows.  We allow three methods for uniquely
identifying
> a concept:
>
> a.  The URI for the concept.
> b.  A combination of the concept's prefLabel and the URI of the
> thesaurus to which it belongs.
> c.  A combination of the concept's externalID and the URI of the
> thesaurus to which it belongs.
>
> So, the following are all valid globally unique concept declarations:
> ----
> <soks:Concept rdf:about="http://foo.com/examplethes/aconcept"/>
> ----
> <soks:Concept>
> <soks:prefLabel>Bangers & Mash</soks:prefLabel>
> <rdfs:isDefinedBy rdf:resource="http://foo.com/examplethes"/>
> </soks:Concept>
> ----
> <soks:Concept>
> <soks:externalID>A00456</soks:externalID>
> <rdfs:isDefinedBy rdf:resource="http://foo.com/examplethes"/>
> </soks:Concept>
> ----
>
> I'll get to why in a minute.
>
> I also then thought, rather than giving every concept and
<rdfs:isDefinedBy>
> property to indicate membership of some conceptual scheme, why not allow
> people to subclass the <soks:Concept> class?
>
> So, for example, you could define the class:
> ----
> <rdfs:Class rdf:about="http://foo.com/thesaurus/Concept">
> <rdfs:subClassOf
> rdf:resource="http://www.w3c.rl.ac.uk/2003/11/21-skos-core#Concept"/>
> <rdfs:comment>This is the class of all concepts from the foo.com
> thesaurus.</rdfs:comment>
> </rdfs:Class>
> ----
> Which would then allow globally unique concept declarations such as the
> following:
> ----
> <foo:Concept>
> <soks:prefLabel>Bangers & Mash</soks:prefLabel>
> </foo:Concept>
> ----
> <foo:Concept>
> <soks:externalID>A00456</soks:externalID>
> </foo:Concept>
> ----
>
> OK, so why bother?
>
> 1.  It makes for better-looking RDF encodings (this is a serious point, as
> it may help reduce the uptake hurdle - how many times have you heard
people
> groan that RDF looks like gobbledegook because of all the URIs?  Also
> remember many potential users are from totally non sem-web environments,
> e.g. english heritage.  RDF is a new and complicated beast to them.)
>
> 2.  It may not be appropriate to give a URI to a concept that is part of
> some thesaurus that has been defined by an authority outside the semantic
> web world.  So until the authority itself gives its own concepts URIs, we
> can still make statements about them using reference-by-description.
>
> On the down side ...
>
> 1.  Someone has to write a bit of reasoning code to equate all blank nodes
> with the same prefLabel/rdfs:isDefinedBy property values, and run it over
> the data before publishing it.
>
> Where I fall on the matter:  in the short term use URIs to identify
> concepts, so can work in a world without any reasoning required.  In the
> slightly longer term look into allowing the blank-node style encodings,
and
> support the little bit of reasoning required with some code.
>
> What does everyone think?
>
> Al.
>
>
> [1] http://www.w3c.rl.ac.uk/SWAD/deliverables/8.1.html
> [2] http://www.w3c.rl.ac.uk/SWAD/deliverables/8.3.html
> [3] http://www.w3c.rl.ac.uk/SWAD/deliverables/8.4.html
>
> CCLRC - Rutherford Appleton Laboratory
> Building R1 Room 1.60
> Fermi Avenue
> Chilton
> Didcot
> Oxfordshire OX11 0QX
> United Kingdom
>
> Email:        a.j.miles@rl.ac.uk
> Telephone: +44 (0)1235 445440
>
>

Received on Thursday, 5 February 2004 15:13:54 UTC