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ISSUE-183: Last Call Comment: Class-Topic relationships

From: SWD Issue Tracker <dean+cgi@w3.org>
Date: Wed, 8 Oct 2008 10:07:16 +0000 (GMT)
To: public-swd-wg@w3.org,public-rdf-in-xhtml-tf@w3.org
Message-Id: <20081008100716.78E4C6B62C@tibor.w3.org>


ISSUE-183: Last Call Comment: Class-Topic relationships

http://www.w3.org/2006/07/SWD/track/issues/183

Raised by: Sean Bechhofer
On product: SKOS

Raised by Michael Panzer [1]:


3. Class-Topic relationships
----------------------------

This issue seems to cause some general problems for using SKOS as a
general tool to model classification systems, since the fundamental
entity in a classification system is not the concept but the class, or,
more precisely, the distinction between classes and their subjects.
There are numerous examples of problems that arise by the difficulty of
expressing in SKOS the interplay between a class and the subjects that
form that class on the basis of at least one common characteristic.

The inability to model other than concept-concept relationships with
SKOS sometimes leads to inconsistencies as subjects/topics are
frequently in the domain or range of common classification
relationships.

In the DDC, this can manifest itself in classes being connected by both
hierarchical and non-hierarchical relationships if modeled with current
SKOS:

<A> skos:narrower <B> .
<B> skos:related <A> .

This arises because what is expressed here isn't really a relationship
between classes, but between topics and classes:

<A> ddc:narrower <B> .
<Topic_in_B> ddc:related <A> .

This pattern can also lead to circular hierarchical relationships:

<A> ddc:narrower <Topic_in_B> .
<B> ddc:narrower <Topic_in_A> .

At the moment in SKOS, this has to be coded at class level:

<A> skos:narrower <B> .
<B> skos:narrower <A> .

which produces inconsistencies. A possible solution would be to
introduce/define ddc:related (or similar relationships) as a new element
without extending SKOS semantic relationships, even if this would mean
lowering the utility of classification systems in SKOS applications.

[1] http://lists.w3.org/Archives/Public/public-swd-wg/2008Oct/0061.html
Received on Wednesday, 8 October 2008 10:07:57 GMT

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