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RE: geo example

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Tue, 27 Apr 2004 23:39:45 +0200
To: "Dan Brickley" <danbri@w3.org>
Cc: <public-esw-thes@w3.org>
Message-ID: <GOEIKOOAMJONEFCANOKCGEMBDOAA.bernard.vatant@mondeca.com>


Dan

> > > http://dmoz.org/Regional/Europe/United_Kingdom/England/Bristol/ shows a
> > > topic from open directory.
> >
> > Would you call this resource a "subject indicator", to use topic maps dialect?
>
> I don't know enough about the detailed mysteries of topicmaps there, but
> certainly this seems close. It is, colloqially, a subject or topic,
> thought of a thing-in-itself, and distinct from both the thing(s) that
> topic represents, and from documents and data representing either the
> topic or the, er, subject of the topic.

> I give up! this terminology is too overloaded to say anything ;)

Hmm ... trying to sort out terminology ... it's not that difficult, in fact :))

Let's say you have somewhere a formal representation of a Class "City" and an instance of
it "Bristol".

This can be expressed either in OWL-RDF ...

<owl:Class rdf:ID="City"/>
<City rdf:ID="Bristol"/>

.. or in Topic Maps XTM

<topic id="City>
<topic id="Bristol">
	<instanceOf>
		<topicRef xlink:href="#City">
	</instanceOf>
</topic>

Now you want to say that the dmoz resource
http://dmoz.org/Regional/Europe/United_Kingdom/England/Bristol/
somehow "indicates" what the above abstract entity formally "represents"
In XTM, this would be expressed by:

<topic id="Bristol">
	<instanceOf>
		<topicRef xlink:href="#City">
	</instanceOf>
	<subjectIdentity>
            <subjectIndicatorRef
xlink:href="http://dmoz.org/Regional/Europe/United_Kingdom/England/Bristol/"/>
      </subjectIdentity>
</topic>

How you would do it in OWL is not standard ...

> Put another way... the "etc/England/Bristol/" node in the DMoz topic
> graph (and its equiv in SKOS) are things that represent "the concept/idea of the
> place Bristol", rather than representing Bristol directly. There is an
> additional level of indirection compared to 'raw' RDF (and OWL).

Yes, that's exactly what the above XTM example expresses.

> > > And we can doubtless find some RDF representation of Bristol as
> > > a member of a class "City", with location info, population, etc...
> > >
> > > My hypothesis is that a new property in SKOS, skos:conceptualizes,
> > > could be used to relate bristol-the-skos-concept to
> > > bristol-the-thing-in-the-world.
> >
> >  ... looks to me indeed very close to the notion of "subjet indicator".
>
> I suspect so too. Topicmap people have often said that RDF confuses
> things with their representations. I believe RDF allows such modelling
> errors to be made, but also that it allows perfect clarity.

Agreed. In fact there are too many different ways to express clearly any number of levels
of indirection in RDF, but unfortunately no standard one. Hence the endless debates about
URIs "meaning".

> TMs, on my understanding, try to have more built-in facilities for preserving
> those distinctions.

Yes. That does not mean everyone using Topic Maps understand them - let alone those who
won't even try to :))

Bottom line : what about "skos:subjectIndicator" to express what you suggest? For example:

<skos:Concept rdf:about="http:/example.com/geo/Bristol">
		<skos:inScheme rdf:resource="http:/example.com/geo/"/>
		<skos:prefLabel>Bristol</skos:prefLabel>
		<skos:altLabel>City of Bristol</skos:altLabel>
		<skos:subjectIndicator
rdf:resource="http://dmoz.org/Regional/Europe/United_Kingdom/England/Bristol/"/>
</skos:Concept>

Say what?

Bernard

Bernard Vatant
Senior Consultant
Knowledge Engineering
Mondeca - www.mondeca.com
bernard.vatant@mondeca.com
Received on Tuesday, 27 April 2004 17:49:29 GMT

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