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rdfs:Class and rdfs:subClassOf considered harmful

From: Richard H. McCullough <rhm@cdepot.net>
Date: Wed, 20 Nov 2002 00:34:03 -0800
Message-ID: <000c01c2906f$e886c070$bd7ba8c0@rhm8200>
To: "RDF-Interest" <www-rdf-interest@w3.org>
Note: this document is available online at http://rhm.cdepot.net/doc/CASharmful.txt

# KEHOME/doc/CASharmful.txt
# Nov/20/2002

rdfs:Class and rdfs:subClassOf considered harmful
=====================================
Author: Richard H. McCullough
Date: November 20, 2002

Contents
=======
Abstract
rdfs:Class
rdfs:subClassOf
References


Abstract
======
In two previous documents [1],[2], I pointed out some
logical problems with rdfs:Class and rdfs:subClassOf.
In this document I identify the exact nature of the
problems.

rdfs:Class is a contradiction with two distinct,
essentially-different definitions.

The definition of rdfs:subClassOf logically permits
contradictions.

rdfs:Class
=======
rdfs:Class has two separate definitions (not explicitly
stated anywhere).

1. Class1 is the Datatype used to represent a concept.

2. Class2 is concept.

Definition 1 implies that statements such as

        <rdfs:Resource> <rdf:type> <rdfs:Class>

should be replaced by

        <rdfs:Resource> <rdfs:Datatype> <rdfs:Class1>

Definition 2 implies that statements such as

        <Person> <rdfs:subClassOf> <rdfs:Class>
        <rdfs:Class> <rdfs:subClassOf> <rdfs:Resource>

should be replaced by

        <Person> <rdfs:subClassOf> <rdfs:Class2>
        <rdfs:Class2> <rdfs:subClassOf> <rdfs:Resource>

I recommend that Class2 be removed from RDFS.

rdfs:subClassOf
============
Example:

        <man> <rdfs:subClassOf> <animal>

logically permits the alternative that the set of all
men is identical to the set of all animals, which is
clearly false.

I recommend that subClassOf be replaced by speciesOf
and individualOf, i.e., replace subset by proper subset
and explicitly distinguish Individuals from Classes.


References
========
[1] Class and Subclass
    "http://rhm.cdepot.net/doc/ClassAndSubclass.txt"
[2] owl:definitionOf
    "http://rhm.cdepot.net/doc/definitionOf.txt"
============ 
Dick McCullough 
knowledge := man do identify od existent done
knowledge haspart list of proposition
Received on Wednesday, 20 November 2002 03:36:26 GMT

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