Re: same-syntax extensions to RDF

> 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 going.

I think I gave that mistaken impression by trying to keep my options
open.   My "uncle" example certainly involves entailment. 

> > 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".

It's possible, but those divergences might not matter in practice.
I'd rather not throw away this chick before it's hatched.

> 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".

This "parsing" is the same as graph matching, which is the bread and
butter of RDF applications, so I don't see it as any particular
challenge.  Maybe I'm missing some additional challenge -- I never
read Sean's paper, and my OWL implementation just did little graph
matches on the triples as needed.  Trying to get the full "abstract"
syntax out would be more challenging, I suppose, although probably not
in a rule 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.)

Again, I don't want to prejudge the result.   Mostly right now I'd
like to find out of its theoretically possible to do; if it is, then
we can try to see if there's a user-friendly way to do it.   Encoding
in strings might actually be very nice for users, and isn't a big
problem for my style of formalizing the semantics, if we define a
predicate connecting string literals to an rdf:List of the
one-character string literals which form it.   (It's tedious to map
the strings to the triple form I've been using in examples, but it's
mechanical -- it's basically a prolog DCG.)

Sorry I'm not giving you a proper detailed answer to some of your
questions yet; it's at the top of my non-interupt queue.

        -- sandro

[1] http://lists.w3.org/Archives/Public/www-rdf-logic/2004Dec/0016

Received on Wednesday, 22 December 2004 18:32:51 UTC