RE: Thing and Class

I think James Leigh's interpretation is flawed.

1) It confuses "classification" (a statement that is a relationship between a class and a member) with "Class" (a set of things).

2) It seems to miss the fact (at least in some statements) that Classes can also be Individuals (i.e. Classes are also members of the class Thing). All Individual means is "member of class". It is true that some Individuals are not classes (E.g. I am not a Class) but that does not mean no Classes are Individuals.

This mis-interpretation is understandable given OWL DL being defined wrt set theory, not metaphysics. Since OWL DL, the language, says nothing about levels of abstraction being modeled, it cannot say whether any Individual is also a Class or not. As someone pointed out earlier, ISO 15926 Lifecycle integration schema tries to make this clear by defining Possible Individual as being something with a 4D extent and as being disjoint with Class.

Cheers,
David

-----Original Message-----
From: semantic-web-request@w3.org on behalf of James Leigh
Sent: Thu 2008-08-28 03:30
To: Richard H. McCullough
Cc: Semantic Web at W3C
Subject: Re: Thing and Class
 

Hi Richard et al.

Here is an informal interpretation of some of the spec written in plain
English.

Class stands for classification.
We use Class to classify things.
Class is a set of Things.
"I am a Human" - I just classified myself as Human (I hope I'm right).
"I am a Thing" - that is true for everything.
Human is a classification of all people.
Thing is a classification of all things.
Every Human is a Thing. Therefore Thing is a super set of Human.
Is Human a Thing? No! its a Class!
Everything Thing is an individual.
Human is not an individual, it is a classification of individuals.
Thing is not an individual, it is a classification of individuals.
Can we classify Classes? Yes we can! Human is a classification - I just
classified Human as a classification.
Human is a Class.
Thing is a Class.
Are all Things Classes? No! I am a Thing, but I am not a classification.
Is Thing the same as Class? No! Human is not a Thing, but Human is a
Class.

Hope this helps,
James