W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > July 2003

Re: Assessment of RDF Scheme edits needed re rdfs:subClassOf iff -> if

From: Dan Brickley <danbri@w3.org>
Date: Fri, 11 Jul 2003 10:03:22 -0400
To: w3c-rdfcore-wg@w3.org
Message-ID: <20030711140322.GA19315@w3.org>

Committed:
http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-schema-20030117/
Revision 1.16  2003/07/11 13:57:42  danbri
Updated in light of iff->if decision on subPropertyOf, subClassOf. See
http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Jul/0161.html for
details.

...I backed off commiting my rdf:List wording tweaks to get this done,
which was more straightforward. Let me know if there's any problem.

cheers,

Dan

* Dan Brickley <danbri@w3.org> [2003-07-11 09:53-0400]
> 
> 
> I'm working through the edits required on RDF Schema following this 
> decision (which I wasn't party to, but support).
> 
> In section "2. Classes" of RDFS, we say:
> 
> [[
> RDF distinguishes between a class and the set of its instances.
> Associated with each class is a set, called the class extension of the
> class, which is the set of the instances of the class. Two classes may
> have the same set of instances but be different classes. For example,
> the tax office may define the class of people living at the same address
> as the editor of this document. The Post Office may define the class of
> people whose address has the same zip code as the address of the author.
> It is possible for these classes to have exactly the same instances, yet
> to have different properties. Only one of the classes has the property
> that it was defined by the tax office, and only the other has the
> property that it was defined by the Post Office.
> 
> A class may be a member of its own class extension and thus may be an
> instance of itself. 
> ]]
> 
> I propose to leave this intact except for striking 'thus' from the
> second sentence.
> 
> We go on to say:
> [[
> A class C is a subclass of a class C' if and only if all the instances
> of C are also instances of C'. All classes are subclasses of themselves.
> The rdfs:subClassOf property may be used to state that one class is a
> subclass of another. The term super-class is used as the inverse of
> subclass. A class C' is a super-class of a class C if and only if C is a
> subclass of C'.
> ]]
> 
> This is the crux of it. As a replacement, I propose:
> [[
> If a class C is a subclass of a class C', then all instances of C will
> also be instances of C'. The rdfs:subClassOf property may be used to
> state that one class is a subclass of another. The term super-class is
> used as the inverse of subclass. If a class C' is a super-class of a
> class C, then all instances of C are also instances of C'.
> ]]
> 
> Given the new semantics, this as close to a definition as we can easily
> get. We tell the world the consequences of an rdfs:subClassOf relation, 
> but we don't have an 'iff' definition anymore, which is necessarily
> going to be a crisper read.
> 
> Section "3. Properties", 
> [[
> This specification defines the concept of subproperty. A property P is a
> subproperty of property P' if and only if all subjects and objects
> related by P are also related by P'. All properties are subproperties of
> themselves. The term super-property is often used as the inverse of
> subproperty, i.e. P is a super-property of P' if and only if P' is a
> subproperty of P. This specification does not define a top property that
> is the super-property of all properties.
> ]]
> needs to become:
> [[
> This specification defines the concept of subproperty. If a property P
> is a subproperty of property P', then all pairs of resources which are 
> related by P are also related by P'. The term super-property is often
> used as the inverse of subproperty. If a property P' is a super-property
> of a property P, then all pairs of resources which are related by P 
> are also related by P'. This specification does not define a top
> property that is the super-property of all properties.
> ]]
> 
> Sections "3.4 rdfs:subClassOf" and "3.5 rdfs:subPropertyOf" - no change
> needed. 
> 
> I believe this is all the edit needed to bring things back into line
> with the semantics. Someone else's attention on this would be much
> appreciated, though I'll commit an updated doc with these changes for
> review.
> 
> Thanks,
> 
> Dan
> 
> 
> ----- Forwarded message from Dan Connolly <connolly@w3.org> -----
> 
> From: Dan Connolly <connolly@w3.org>
> Date: 10 Jul 2003 11:00:19 -0500
> To: www-webont-wg@w3.org
> Cc: Brian McBride <bwm@hplb.hpl.hp.com>
> Subject: RDFCore changed rdfs:subClassOf from iff to if
> Message-Id: <1057852819.16090.432.camel@dirk.dm93.org>
> Resent-From: www-webont-wg@w3.org
> Resent-Date: Thu, 10 Jul 2003 12:36:27 -0400 (EDT)
> Organization: World Wide Web Consortium (http://www.w3.org/)
> 
> 
> As I mentioned briefly last week...
> http://www.w3.org/2003/07/03-webont-irc#T17-26-38
> 
> RDF Core has decided to change the semantics of rdfs:subClassOf
> and subPropertyOf...
> 
> [[
> 10: Issue horst-01
> 
> DECISION: to close horst-01 by moving to intensional semantics for
> subClassOf ('if' rather than 'if and only if'), and by including new
> rules rdfs12a and rdfs12b in additional part of rules section.
> [...]
> 
> ACTION: DanC to inform WebOnt. context,
> http://www.w3.org/2003/06/27-rdfcore-irc#T15-21-11
> 
> ACTION: PatH to respond to the commentor (ter horst). context,
> http://www.w3.org/2003/06/27-rdfcore-irc#T15-21-48
> ]]
> 
> I think the only impact is on S&AS, and Peter said
> he was well prepared for it; he'd only have to
> un-comment some stuff from his source.
> 
> 
> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
> 
> 
> ----- End forwarded message -----
Received on Friday, 11 July 2003 10:03:22 EDT

This archive was generated by hypermail pre-2.1.9 : Wednesday, 3 September 2003 09:58:45 EDT