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Re: Layering on the Semantic Web

From: Dan Connolly <connolly@w3.org>
Date: 03 Jan 2002 13:32:44 -0600
To: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
Cc: www-webont-wg@w3.org
Message-Id: <1010086365.3381.9.camel@dirk>
On Thu, 2002-01-03 at 11:28, Frank van Harmelen wrote:
> In an off-line email message, Jim wrote:
> 
> > I'm curious about losing RDF-schema compatibility, of all of them, that seems
> > like the simplest to preserve (esp. as we can still influence
> > rdf-schema if minor changes to it fix this)
> 
> Two reasons for only partial compatability:
> - syntactic: we're not sure if we can organise the XML syntax to "include" a/some/all of the RDF Schema serialisations. 

Relax-NG seems like a pretty good mechanism for
working with RDF, syntactically.

cf
http://www.w3.org/TR/2001/WD-rdf-syntax-grammar-20011218/#section-RELAXNG-Schema

> - semantic: as you know, the RDF Schema model contains some oddities (classes as members of classes, etc). We might want to make the OWL meta-model simpler. 

Or we might want to work with the RDF Core WG to find
something mutually agreeable. e.g.
re classes as members of classes, this has been addressed
to my satisfaction. I invite other folks to take a look:

 " 1.1 Technical Note

We assume that there is no restriction on the domains and ranges of
properties; in particular, a property may be applied to itself. When
classes are introduced in RDFS, we will assume that they can contain
themselves. This might seem to violate one of the axioms of standard
(Zermelo-Fraenkel) set theory, the axiom of foundation, which forbids
infinitely descending chains of membership. However, the semantic model
given here distinguishes properties and classes as objects from their
extensions - the sets of object-value pairs which satisfy the property,
or things that are 'in' the class - thereby allowing the extension of a
property or class to contain the property or class itself without
violating the axiom of foundation."
	--
http://lists.w3.org/Archives/Public/www-archive/2002Jan/att-0007/01-RDF_Model_Theory.htm

I have raised a related issue; I expect it to be addressed in this
WG rather than in the RDF Core, but I'm happy for it to go
either way...

* vocabulary for traditional sets Dan Connolly (Tue, Nov 06 2001)
http://lists.w3.org/Archives/Public/www-rdf-comments/2001OctDec/0210.html



> 
> Frank.
>    ----
-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 3 January 2002 14:32:44 GMT

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