W3C home > Mailing lists > Public > public-webont-comments@w3.org > December 2003

TexasThings and owl:equivalentThing

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Mon, 15 Dec 2003 19:21:28 +0100
To: <public-webont-comments@w3.org>
Message-ID: <GOEIKOOAMJONEFCANOKCOELFCNAA.bernard.vatant@mondeca.com>


Seems to me that there is something wrong, or at least misleading with the
example of "TexasThings"
http://www.w3.org/TR/owl-guide/#equivalentClass1

<owl:Class rdf:ID="TexasThings">
  <owl:equivalentClass>
    <owl:Restriction>
      <owl:onProperty rdf:resource="#locatedIn" />
      <owl:allValuesFrom rdf:resource="#TexasRegion" />
    </owl:Restriction>
  </owl:equivalentClass>
</owl:Class>

First it would certainly be better to have the singular "TexasThing" rather
than plural "TexasThings" :)

"TexasThings are exactly those things located in the Texas region ..."

This is obviously wrong. There is an allValuesFrom, but not a
someValuesFrom here. As defined, it means : If TexasThings are located
somewhere, they are located in Texas region.

An further on

" ... The difference between using owl:equivalentClass here and using
rdfs:subClassOf is the difference between a necessary condition and a
necessary and sufficient condition. With subClassOf, things that are
located in Texas are not necessarily TexasThings. But, using
owl:equivalentClass, if something is located in Texas, then it must be in
the class of TexasThings."

... but not the other way round, unfortunately.

In fact under this definition any thing located nowhere is a Texas Thing.
Thinking about it, maybe it makes sense after all. Nowhere is indeed in
Texas, and especially its middle ... :))

Bernard Vatant
Senior Consultant
Knowledge Engineering
Mondeca - www.mondeca.com
bernard.vatant@mondeca.com
Received on Monday, 15 December 2003 13:21:35 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:43:29 GMT