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Re: Dark triples, current closure / entailment rules, can someone clarify?

From: Jan Grant <Jan.Grant@bristol.ac.uk>
Date: Tue, 25 Jun 2002 16:29:48 +0100 (BST)
To: pat hayes <phayes@ai.uwf.edu>
cc: w3c-rdfcore-wg@w3.org
Message-ID: <Pine.GSO.4.44.0206251622570.27038-100000@mail.ilrt.bris.ac.uk>

On Tue, 25 Jun 2002, pat hayes wrote:

> >To be honest, I think examples like this are why we should have an
> >explicit, not implicit name-based, darkening mechanism.
> I fail to follow why this kind of example would lead you to that
> conclusion. BUt in any case there are other strong reasons for not
> coming to that conclusion, which we have gone over now several times.
> If there is any way to assert darkness, then there is no way, in
> practice, to avoid nonmonotonicity. Moreover, it places an additional
> burden on users and implementers, who ideally shouldnt even have to
> know about this stuff almost all the time.

You misunderstand; I'm not talking about an in-RDF (Guha's "same
syntax") mechanism- I'm talking about explicitly flagging triples as
dark using something like

	<rdf:Descrpition rdf:about="eg:foo">
	  <eg:blah rdf:dark="yes">wibble</eg:blah>

rather than implicitly by examining the property URI.

The burden on users and implementers, I think, is going to be there
regardless. For the most part it can probably be made "invisible" to
users by, for instance, having the daml:colleciton spit out
appropriately-darkened triples (ie, a little bit of sugar in the right


PS. Why I came to this conclusion is that I posed a simple example and
got two sets of answers, neither of which was 100% accurate. I think
things like the subproperty malarky are almost certainly going to crop
up. I'd be happier if the presence of a darkening URI _anywhere_ in a
triple caused the triple to be dark; although I've heard that that has
problems too.

jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/
Tel +44(0)117 9287088 Fax +44 (0)117 9287112 RFC822 jan.grant@bris.ac.uk
You see what happens when you have fun with a stranger in the Alps?
Received on Tuesday, 25 June 2002 11:30:27 UTC

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