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Resources, Classes, and Concepts

From: David Menendez <zednenem@psualum.com>
Date: Sat, 02 Oct 2004 00:48:53 -0400
To: public-esw-thes@w3.org
Message-id: <r02010200-1035-5D8A5D14142E11D9B4B0000393758032@[192.168.2.44]>

I missed most of the skos:denotes thread, so I'll try to summarize my
position here. Let me restate Alistair's example:

    a:ajm a skos:Concept
        ; skos:prefLabel "Alistair Miles"
        ; skos:scopeNote "The man from SKOS"
        .
    
    b:ajm a foaf:Person
        ; foaf:name "Alistair Miles"
        ; foaf:mbox <mailto:A.J.Miles@rl.ac.uk>
        .

My feeling is that a:ajm and b:ajm should not be considered to denote
the same resource.

Let's say they did. That would mean that we can replace a:ajm with b:ajm
and vice versa anywhere in the graph without changing its
interpretation. Now let's say that another concept scheme also includes
a concept for Alistair:

    c:ajm a skos:Concept
        ; skos:prefLabel "Alistair Miles"
        .

In that case, we'd have to say that c:ajm also denotes the same resource
as a:ajm and b:ajm. The problem is that most of the annotation
properties SKOS provides only make sense in the context of a single
concept scheme. My feeling is that we do not want a:ajm and c:ajm to
denote the same resource.

What we want to say is:

    a:ajm skosmap:exactMatch c:ajm.

An analogous situation applies to classes in RDFS and OWL. rdfs:Class
and owl:Class are intensional, which means that two classes can have the
same extension but still be distinct. For example, here are two distinct
classes with the same extension:

    d:ajm a owl:Class
        ; rdfs:label "A class whose only instance is Alistair"
        ; owl:oneOf ( b:ajm )
        .
    
    e:ajm a owl:Class
        ; rdfs:label "A different class whose only instance is Alistair"
        ; owl:oneOf ( b:ajm )
        .

Additionally, if a:ajm and b:ajm are distinct, we can make a useful
distinction between dc:subject and foaf:topic:

    ex:something_about_alistair
        ; dc:subject a:ajm
        ; foaf:topic b:ajm
        .

    ex:something_about_concept_ajm
        ; foaf:topic a:ajm
        .
-- 
David Menendez <zednenem@psualum.com> <http://www.eyrie.org/~zednenem/>
Received on Saturday, 2 October 2004 04:48:57 UTC

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