- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Mon, 20 Dec 2004 08:29:40 -0500 (EST)
- To: sandro@w3.org
- Cc: tammet@staff.ttu.ee, www-rdf-logic@w3.org
From: Sandro Hawke <sandro@w3.org> Subject: Re: same-syntax extensions to RDF Date: Sun, 19 Dec 2004 21:20:10 -0500 > > "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. OK. However, the (best) part of FOL is entailment. If you haven't captured that, then you havn't captured FOL, and it didn't seem as if that is what you were goind. > 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]. Well, here we have a distinct disagreement. My view is that even if you actually succeed, the result will not be worthwhile. Consider the case of OWL. Through much effort, OWL is a same-syntax extension of RDFS. However, there are differences between this version of OWL and the DL (i.e., more-or-less FOL) version of OWL, which is not great. I expect that even a (mostly) successful effort of encoding FOL in RDF will have similar divergences from "the one true FOL". Further, writing parsers for the RDF/XML syntax of OWL is a royal pain. (Yes, I did say parser. An RDF/XML system is really only a tokenizer for OWL.) Having to write such parsers eliminates any potential benefit associated with having one Semantic Web "language". > 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. Well, I at least worry that it is not possible to do this extending in a reasonable manner. (I certainly don't view using strings to encode sentences as being in a reasonable manner.) [...] > -- sandro [...] peter
Received on Monday, 20 December 2004 13:29:50 UTC