W3C home > Mailing lists > Public > www-rdf-interest@w3.org > October 2000

Re: range, domain: Conjunctive AND disjunctive semantics both supportable

From: Jan Grant <Jan.Grant@bristol.ac.uk>
Date: Sun, 1 Oct 2000 15:37:22 +0100 (BST)
To: Ian Horrocks <horrocks@cs.man.ac.uk>
cc: rdf interest <www-rdf-interest@w3.org>
Message-ID: <Pine.GHP.4.21.0010011527090.22987-100000@mail.ilrt.bris.ac.uk>
On Sat, 30 Sep 2000, Ian Horrocks wrote:

> In the OIL language (see http://www.ontoknowledge.org/oil/) we extend
> RDF schema with (amongst other things) logical constructs that allow
> you to say things like:
> 
> 	P --[rdfs:range]-> (A or B)
> 
> This approach has many advantages: it allows disjunctive semantics to
> be exactly captured and it saves cluttering up the class hierarchy with
> unwanted classes.

My original proposal was just a demonstration of how conjunctive
semantics could be used to model the weak 'disjunctive' semantics. The
latter had many problems (as have been repeatedly pointed out: eg, non-
closed world assumptions mean that disjunctive semantics don't give you
very much at all). However, the solution I propose is exactly as strong
as the disjunctive case; it shares all its weaknesses.

As the supporters of the disjunctive use point out, their application
domains allow them to make stronger assumptions or model class
restrictions more closely. Ian's example, OIL, is a prime
example of this in practice ['this' being 'stronger modelling'].

> Of course the meaning would only be accessible to
> OIL-aware agents.

RDFSchema, as I understand it, is merely intended to provide a modelling
framework. It is to be expected that application domains that need more
expressivity build something on top of what RDFSchema provides. However,
_rdfs_ can't mandate an overly complicated logical layer* because,
presumably, we don't want to burden every potential user of rdfs with
a(nother) complex implementation problem.

jan

* Or can it? Discuss :-)

-- 
jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/
Tel +44(0)117 9287163 Fax +44 (0)117 9287112 RFC822 jan.grant@bris.ac.uk
Whose kung-fu is the best?
Received on Sunday, 1 October 2000 10:37:30 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:51:44 GMT