- From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
- Date: Wed, 13 Feb 2002 00:54:10 +0100
- To: www-webont-wg@w3.org
"Peter F. Patel-Schneider" wrote: > The *next* step, of course, is to decide on which layering approach to use. > I am delaying throwing out the ceremonial grenade for this next step until > the current document has been at least somewhat assimilated. However, if > you can't wait, don't let my (unusual) reticence dissuade you. :-) Discussion so far has focussed on how to salvage the first layering approach (same syntax, extended semantics), and rightly so in my opinion, since this is the most natural option. 1. The first fix to RDFS that would save the preferred layering option has been dubbed "moving rdf:type into the meta-theory". Can someone clarify if this is the same as what was called "stratifying RDF Schema" in earlier discussions? (ie not making rdfs:Class an instance of itself). Stratifying the RDFS class-hierarchy has been explored before by different authors (e.g. [1],[2],[3]) 2. The second fix to RDFS that would save the first layering option would be to distinguish "asserted RDF triples" from "not-asserted RDF triples". The RDF(S) model-theory would only apply to asserted triples. The triples that are "only OWL syntax" would be not-asserted, would not contribute to the models, and would therefore not construct paradoxes. Pat Hayes has been claiming that RDF Core would seriously consider such an option. It would not only solve our layering problem, but also solve the problems of anybody else who tries to define other languages on top of RDF. (For instance, McDermott has to resort to reification to encode 'a->b' in RDF to avoid ending up with asserting 'a'. Allowing unasserted triples would also solve his problem.) 3. I think it's a shortcoming of this (otherwise excellent) document that it seems to suggest that the same-syntax/extended-semantics is not obtainable. It >*is*< obtainable with any of the above fixes to RDF(S), and I would strongly suggest that the document discusses them (after all, its purpose is to lay out the map of all options). Frank. ---- As a PS: I'm very happy that with the highly readable requirements doc by Jeff et al. and the layering options doc by Peter and Dieter this WG is well on its way to produce much more readable documents than any of the other W3C groups I know of. [1] http://sesame.aidministrator.nl/doc/rdf-interpretation.html#N1c1e48d [2] http://www.semanticweb.org/SWWS/program/full/paper11.pdf [3] http://www.kbs.uni-hannover.de/Arbeiten/Publikationen/2000/modeling2000/wolpers.pdf
Received on Tuesday, 12 February 2002 18:55:07 UTC