- From: Alan Ruttenberg <alanruttenberg@gmail.com>
- Date: Tue, 12 Aug 2008 11:22:40 -0400
- To: Ivan Herman <ivan@w3.org>
- Cc: Michael Schneider <schneid@fzi.de>, public-owl-wg Group WG <public-owl-wg@w3.org>, Zhe Wu <alan.wu@oracle.com>, Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
On Aug 12, 2008, at 11:16 AM, Ivan Herman wrote: > Alan Ruttenberg wrote: >> On Aug 12, 2008, at 11:02 AM, Michael Schneider wrote: >>> Alan Ruttenberg wrote: >>> >>>> Is the assumption that in OWL R/Full that the only way in which one >>>> determine entailments is to forward chain rules and then look in >>>> the >>>> resultant triples for it? >>> >>> It's not an "execution semantics". Instead, there has to *exist* >>> a finite >>> sequence of rule applications, which leads from the LHS to the >>> RHS (or an >>> upper graph of the RHS). >> OK. I'm then confused by Ian's comment about generating infinite >> numbers of triples: > > But his comment _was_ justified. In > > http://www.w3.org/TR/rdf-mt/#RDFINTERP > > the number of axiomatic triples is infinite indeed, due to the > rdf:_i terms. Herman ter Horst's trick of keeping it finite for a > specific graph tries to get around that problem and thereby making > it possible to do, eg, a forward chaining on a specific graph (with > the caveat that PFPS just referred to in another mail:-( Yes, but my question to Michael was to this point. From what he says I don't see that the theoretical existence of an infinite number of triples necessitates their materialization by forward chaining. There are other methods of using rules. -Alan > > Ivan > > >>> Presumably, making axiomatic triples be part of OWL RL (Full) >>> would mean extending the rule set so that it would generate such >>> triples. There could be a very large (perhaps even infinite) >>> number of such triples. This might be a serious burden on >>> implementations and lead to a significant degradation in >>> performance. >>> "Entailment" might be not the right term here, because it is >>> probably more >>> typically used in the context of model-theoretic semantics. I >>> prefer to speak about "derivations". >> We need to figure out and use a common language or make the >> appropriate language visible in the specification if it is missing. >> -Alan >>> >>>> -Alan >>> >>> Cheers, >>> Michael >>> >>> -- >>> Dipl.-Inform. Michael Schneider >>> FZI Forschungszentrum Informatik Karlsruhe >>> Abtl. Information Process Engineering (IPE) >>> Tel : +49-721-9654-726 >>> Fax : +49-721-9654-727 >>> Email: Michael.Schneider@fzi.de >>> Web : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555 >>> >>> FZI Forschungszentrum Informatik an der Universität Karlsruhe >>> Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe >>> Tel.: +49-721-9654-0, Fax: +49-721-9654-959 >>> Stiftung des bürgerlichen Rechts >>> Az: 14-0563.1 Regierungspräsidium Karlsruhe >>> Vorstand: Rüdiger Dillmann, Michael Flor, Jivka Ovtcharova, Rudi >>> Studer >>> Vorsitzender des Kuratoriums: Ministerialdirigent Günther >>> Leßnerkraus >>> > > -- > > Ivan Herman, W3C Semantic Web Activity Lead > Home: http://www.w3.org/People/Ivan/ > PGP Key: http://www.ivan-herman.net/pgpkey.html > FOAF: http://www.ivan-herman.net/foaf.rdf >
Received on Tuesday, 12 August 2008 15:23:20 UTC