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Re: RDF vocabulary definitions

From: Richard H. McCullough <rhm@cdepot.net>
Date: Tue, 19 Nov 2002 21:54:53 -0800
Message-ID: <000d01c29059$594d6a50$bd7ba8c0@rhm8200>
To: "David Menendez" <zednenem@psualum.com>, "Sandro Hawke" <sandro@w3.org>
Cc: <www-rdf-interest@w3.org>
I agree with Sandro 100%.  That asymmetry was confusing me too.
The problem is that Class (sense 1) is like a Datatype used to represent a Class (sense 2).

To focus on the contrast between these two senses, consider

1.    entity  type  Class
2.    person  type  entity

which can be uniformly interpreted as

3.    entity  Datatype  Class (sense 1)
4.    entity  subClassOf  Class (sense 2)
5.    Class (sense 2)  subClassOf  Resource
6.    person  Datatype  Class (sense 1) 
7.    person  subClassOf  entity
8.    entity  subClassOf  Resource
Dick McCullough 
knowledge := man do identify od existent done
knowledge haspart list of proposition

  ----- Original Message ----- 
  From: Sandro Hawke 
  To: David Menendez 
  Cc: www-rdf-interest@w3.org 
  Sent: Tuesday, November 19, 2002 7:48 PM
  Subject: Re: RDF vocabulary definitions 

  > At 9:17 AM -0800 2002-11-19, Richard H. McCullough wrote:
  > >The two triples have the same meaning; either one implies the other.
  > ><_:MyClass> <rdf:type> <rdfs:Class>
  > ><_:MyClass> <rdfs:subClassOf> <rdfs:Class>
  > This is not my understanding of how RDFS defines these terms.
  > As a practical example, if I declare a class "Car", I would say:
  >    eg:Car rdf:type rdfs:Class.
  > If this implied that eg:Car is a subclass of rdfs:Class, then it 
  > would mean that any instance of eg:Car is also a class.
  > Given:
  >    eg:my_car rdf:type eg:Car.
  >    eg:Car rdf:type rdfs:Class.
  > Implies:
  >    eg:Car rdfs:subClassOf rdfs:Class. # according to what you just said
  >    eg:my_car rdf:type rdfs:Class.     # according to rdfs9
  > RDFS distinguishes between classes and class extensions. You could 
  > create a system where my car is a class consisting of all cars that 
  > are my car, but that's not how RDFS does it.

  Ugh, indeed you're right.  Thanks for the clear and gentle correction.

  These are true though, I think:

    x rdf:type rdfs:Property.   
    x rdfs:subPropertyOf rdfs:Property.

    x rdf:type rdfs:Class.  
    x rdfs:subClassOf rdfs:Resource.

  and that little asymmetry was confusing me.

       -- sandro
Received on Wednesday, 20 November 2002 00:54:58 UTC

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