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Re: Summary and some analysis: New Semantics Initiative

From: Dan Connolly <connolly@w3.org>
Date: 12 Jun 2002 17:49:51 -0500
To: "R.V.Guha" <guha@guha.com>
Cc: Brian McBride <bwm@hplb.hpl.hp.com>, rdf core <w3c-rdfcore-wg@w3.org>
Message-Id: <1023922192.10945.55.camel@dirk>

On Wed, 2002-06-12 at 16:01, R.V.Guha wrote:

> I would like to get a wider sample, especially from the folks building 
> stuff (like Libby, Connolly, ...).

I prefer an axiomatic approach inasmuch as it allows me to use
the machine to check my work etc.

I'm stil mulling over details of this approach; in particular,
stuff like

"Axiom schemes do not take the language beyond first-order, since all
the instances are first-order sentences and the language is compact, so
if any Lbase sentence follows from (the infinite set of instances of) an
axiom scheme, then it must in fact be entailed by some finite set of
instances of that scheme. "
 -- http://tap.stanford.edu/SemanticWebSemantics.html

give me pause, as does:

"Since relations are first-class entities in Lbase, we can express this
relationship with an axiom:

(forall (?x ?y) (rdf:type(?x, ?y) <=> ?y(?x))) "
	-- http://www.coginst.uwf.edu/%7Ephayes/RDF%28S%29_based_on_Lbase.html

I agree with Graham that...
"- in the description of axiom schemata, it is not clear how one is
expected to distinguish "schematic variables" from non-substitutable

I'm quite happy with the "menzel indrection trick" in the present model
theory. I'm still noodling on the corresponding bits of the Lbase stuff.

Another technical reservation I have is committing to classical
negation. Based on discussion with TimBL and study of
systems like Isabelle, I don't think the law of the excluded
middle is a good thing to commit to for the semantic web.

I have to admit that I can't think of a way to make these issues
show up in RDF 1.0 nor RDFS. But the premise of this approach
is that the same base logic works for higher layers too.
Maybe I'll noodle on some test cases that involve webont-ish

oops; stuff exploding around here; gotta go...

Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Wednesday, 12 June 2002 18:50:50 UTC

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