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Re: same-syntax extensions to RDF

From: Sandro Hawke <sandro@w3.org>
Date: Sun, 19 Dec 2004 21:20:10 -0500
To: tammet@staff.ttu.ee
Cc: www-rdf-logic@w3.org, "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Message-Id: <20041220021715.991454F0EA@homer.w3.org>


"Peter F. Patel-Schneider" <pfps@research.bell-labs.com> writes:
> My understanding of the problem was to write extra semantic conditions on
> RDF(S) interpretations, and thus generate an embedding/encoding of binary
> first-order logic into a semantic extension of RDF(S).  You can't extend
> the syntax at the same time, however, which means that you have to encode
> formulae as triples somehow, and these triples retain their RDF(S) meaning.
> 
> However, it doesn't seem to me that Sandro has the same understanding.

No, that's exactly what I want, too.

I would also like the whole exercise to be, in the end, simple enough
that the community interested in rule languages and RDF can be
comfortably with the results.  I keep hearing about projects using RDF
encodings of Horn or FOL, and they turn out to have either unclear or
inconsistent semantics.  If we're going to move to a standard here, it
would help to clear up whether it is possible to do this kind of
encoding properly.  I can't imagine, for instance, that the approach
taken by SWRL 0.6 would ever be approved in a W3C Recommendation, for
the reasons I outlined in the team comment [1].

If Peter can convince me that it's not possible to write the desired
semantic condition, I can help him convince others that a different
path needs to be taken for rule languages.  If I can convince Peter it
*is* possible (and we figure out how onerous it is), then a standard
can use it (or not, but because the difficulty has been actually
weighed).

Unfortunately, I can't just hand Peter the desired semantic
conditions.  I don't really know how to write them in the formalism of
RDF Semantics [2].  My understanding is that Peter doesn't either and
suspects it's not possible to write them.

Meanwhile, it is "obvious" how to write them informally and with
subtle errors.   Something like "put the FOL expressions in a string
literal and assert it", as I explored in my previous e-mail [3].

So I've been trying to write them using a formalism in which I have a
good sense of how to do it and with which I think I can detect most if
not all subtle errors.  It may also show the way in which to do it in
the desired formalism.

I'll try to return to the substance of this thread shortly.  Peter's
raised to questions I need to explore.

       -- sandro

[1] http://www.w3.org/Submission/2004/03/Comment (in the "RDF" section)
[2] http://www.w3.org/TR/rdf-mt/
[3] http://lists.w3.org/Archives/Public/www-rdf-logic/2004Dec/0022.html
Received on Monday, 20 December 2004 02:17:16 GMT

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