- From: Michael Schneider <schneid@fzi.de>
- Date: Fri, 23 Nov 2007 00:14:04 +0100
- To: "Owl Dev" <public-owl-dev@w3.org>
- Cc: "Jeremy Carroll" <jjc@hpl.hp.com>, <boris.motik@comlab.ox.ac.uk>, <hendler@cs.rpi.edu>, <gstoil@image.ece.ntua.gr>, <alanruttenberg@gmail.com>
[ public comment to OWL-1.1-WG issue 67 cc'ed to WG-members involved in this discussion ] Hi! On Tue, 20 Nov 2007, Jeremy Carroll has raised the following issue: <http://lists.w3.org/Archives/Public/public-owl-wg/2007Nov/0369.html> ISSUE-67 (reification): REPORTED: use of reification in mapping rules is unwise "The mapping rules use RDF reification. However, RDF reification has very weak semantics, making it difficult to achieve an OWL Full semantics that works. It is unlikely that RDF graph's constructed with such rules mean what is intended." The wording in this issue is pretty generical, but, AFAICS, the ongoing discussion in the WG about this issue is completely restricted to /axiom annotations/. I just want to bring to everyone's attention that axiom annotations are not the only OWL-1.1 constructs which have an RDF mapping that uses RDF reification. There are also so called "NegativePropertyAssertion"s, both for object and data properties, which specify that a given "s p o" statement does /not/ exist in the knowledge base, see Table 4 in [1]. As an example, let's regard the following ontology, given in functional syntax: (A1) ObjectPropertyAssertion(p u w) (A2) NegativeObjectPropertyAssertion(p u w) Now, if I map this ontology to RDF, according to Table 2 of [2] I receive (ignoring the required additional typing triples): (R11) u p w . (R21) _:x rdf:type owl11:NegativeObjectPropertyAssertion . (R22) _:x rdf:subject u . (R23) _:x rdf:predicate p . (R24) _:x rdf:object w . So the NegativeObjectProperty has been encoded by reifying the statement 'u p w'. The ontology {(A1),(A2)} is clearly contradictory according to the OWL-1.1-DL semantics given in [1]. This would mean for a (yet-to-specify) RDF-compatible OWL-1.1-Full semantics that a contradiction must be entailable somehow from the RDF graph {(Rij)}. I think that the concerns regarding the use of RDF reification, generically stated by Jeremy in ISSUE-67 (see above), hold for NegativeObjectPropertyS, too. So I suggest that ISSUE-67 should be attached a comment, which tells what OWL-1.1 constructs actually fall under ISSUE-67. Otherwise the discussion in the WG might move into a wrong direction. For example, Boris Motik discusses: <http://lists.w3.org/Archives/Public/public-owl-wg/2007Nov/0389.html> "There is yet another solution: we might have axiom annotations in the structural specification, but then disallow (or simply delete them) when the ontology is exported into OWL RDF." While this would really be a technical solution for the case of "semantic-less" annotations, an analog approach would obviously /not/ be a working solution for the case of negative property assertions, because the latter are real axioms, and therefore must be represented in every syntax. Cheers, Michael [1] OWL-1.1 Semantics <http://www.w3.org/2007/OWL/wiki/Semantics> [2] OWL-1.1 RDF-Mapping <http://www.w3.org/2007/OWL/wiki/Mapping_to_RDF_Graphs> -- 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
Received on Thursday, 22 November 2007 23:14:17 UTC