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Re: A Rough Guide to Notation3

From: Sandro Hawke <sandro@w3.org>
Date: Fri, 23 Aug 2002 16:00:30 -0400
Message-Id: <200208232000.g7NK0U215776@wadimousa.hawke.org>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
cc: seth@robustai.net, sean@mysterylights.com, www-rdf-interest@w3.org

> From: Sandro Hawke <sandro@w3.org>
> Subject: Re: A Rough Guide to Notation3 
> Date: Fri, 23 Aug 2002 14:47:55 -0400
> > 
> > Peter F. Patel-Schneider writes:
> > > Well, how do you *represent* - and here I mean represent, not encode - th
> e
> > > following first-order sentence using *only* labeled directed graphs?
> > > 
> > > 	forall x exists y forall z P(x,y) -> Q(y,z) v S(z,y)
> > 
> > As I mentioned yesterday [1], I believe your example can be
> > respresented in RDF using a pre-arranged vocabulary for describing
> > true sentences.  This is a same-syntax extension to RDF, of the sort
> > one is expected to use in expressing any knowledge with RDF.  (If you
> > want to talk about widgets, you're expected to do so by creating a
> > vocabulary for talking about widgets.  I'm suggesting that a viable if
> > cumbersome way to _say_ "a or b" is to _describe_as_true_ the sentence
> > "a or b".)
> [This now has little to do with graphs, and more to do with RDF.]
> How is the meaning of this pre-arranged vocabulary going to be expressed?

In the usual ways: a model theory and/or FOL axioms.  If we were
talking about widgets, the vocabulary terms would be defined in
natural language, perhaps with some ontology language helping to keep
things straight.  For talking about logical formulas, FOL axioms and
mathematical jargon can give us added clarity.  Many readers will be
happy enough with my ontology [1], but people needing to know the
details will want to look at the axioms [2].   (I should hedge that I
only consider the axioms 85% correct.  I'm looking for feedback on
this technique before going farther with them.)

> Can the meaning be expressed in RDF at all?

Not in an formal sense, no.    (That's a trick question, right?)

> Is the meaning compatible with the RDF
> meaning of the triples that encode the sentences?

Yes.  I believe my approach of translating RDF to FOL means that a
proof of the satisfiability of my axioms is a proof of their
compatibility with RDF.  (I'll need to add some more axioms for RDFS
inference to be complete here.)

   -- sandro

[1] http://www.w3.org/2002/08/LX/RDF/v1 or
[2] http://www.w3.org/2002/08/LX/RDF/ax3.20020822T1630.html
Received on Friday, 23 August 2002 16:00:48 UTC

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