W3C home > Mailing lists > Public > www-rdf-interest@w3.org > November 2002

Re: RDF vocabulary definitions

From: Richard H. McCullough <rhm@cdepot.net>
Date: Thu, 21 Nov 2002 11:17:05 -0800
Message-ID: <001b01c29192$baf97ac0$bd7ba8c0@rhm8200>
To: <www-rdf-interest@w3.org>, "David Menendez" <zednenem@psualum.com>, "Brian McBride" <bwm@hplb.hpl.hp.com>
My comments are in the attached file, mcbride.txt
Dick McCullough 
knowledge := man do identify od existent done
knowledge haspart list of proposition

  ----- Original Message ----- 
  From: Brian McBride 
  To: Richard H. McCullough ; www-rdf-interest@w3.org ; David Menendez 
  Sent: Thursday, November 21, 2002 7:29 AM
  Subject: Re: RDF vocabulary definitions

  At 13:31 20/11/2002 -0800, Richard H. McCullough wrote:
  >I appreciate your effort.  I'm afraid I was erroneously venting my 
  >frustration on you.  I apologize for that.
  >I have been frustrated in my attempts to pin down the meaning of 
  >"Class".  There are so many documents that I have trouble finding one 
  >which addresses my concerns, and almost as much trouble re-finding it later.
  >The first documents that I found when I joined RDF-interest stated 
  >(paraphrasing), "Class is concept".  Another document that I found within 
  >the last hour stated (paraphrasing) "Class is the set of types", as you 
  >indicated based on your examination of RDF-MT.


  I was thinking that perhaps the schema document might say something more 
  about class and did a first rough draft.  Do think including something like 
  this in the schema doc would help, or would it just confuse things more?


  RDF Classes

  Resources may be divided into groups called classes. The members of an RDF 
  Schema class are sometimes known as instances of the class. RDF Schema 
  classes are themselves resources. They are often identified by URIref's [@@ 
  have we defined the rdf use of this term yet?] and may be described using 
  RDF properties. The rdf:type property may be used to state that a resource 
  is a member of a class. Two classes may have exactly the same members and 
  yet be different classes.

  The group of resources that are RDF Schema classes is itself a class called 
  rdfs:Class. This may seem a little confusing to some, and especially to 
  those who think of an RDF Schema class as a set of resources, for the most 
  familiar set theory teaches us that sets cannot be members of themselves. 
  However, as explained in [@@RDF-SEMANTICS], a little mathematical trickery 
  enables RDF Schema classes to behave like sets whilst still enabling them 
  to be members of themselves.

  A class A is a subclass of a class B if and only if all the members of A 
  are also members of B. All classes are subclasses of themselves. The 
  rdfs:subClassOf property may be used to state that one class is a subclass 
  of another.

  The RDF Concepts and Abstract Syntax [@@RDF-CONCEPTS] specification defines 
  the RDF concept of a datatype. RDF Schema defines all datatypes to be 
  classes. The members of a class that is a datatype are the members of the 
  value space of the datatype.

  The core RDF specifications define the following classes.


  All things described by RDF are called resources, and are members of the 
  class rdfs:Resource. This is the class of everything. All other classes are 
  subclasses of this class. [@@ is this true; is it stated or implied in the MT?]


  This is the class of resources that are RDF Schema classes. rdfs:Class is a 
  member of rdfs:Class.


  rdfs:Datatype is the class of datatypes. It is a subclass of rdfs:Class.


Received on Thursday, 21 November 2002 14:18:11 UTC

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