- From: <herman.ter.horst@philips.com>
- Date: Wed, 30 Jul 2003 20:16:56 +0200
- To: pat hayes <phayes@ihmc.us>
- Cc: www-rdf-comments@w3.org
Pat, Thank you for your reaction http://lists.w3.org/Archives/Public/www-rdf-comments/2003JulSep/0012.html to my comment. I believe that it is a wise decision of the RDF Core Working Group to change (weaken) the normative RDFS semantic conditions on subClassOf and subPropertyOf in order to preserve the completeness claim of the RDFS entailment lemma. The error that I noted in this lemma indeed vanishes by means of this change. As you note, there is now a direct correspondence between many of the RDFS semantic conditions and many of the RFDS closure rules. It is interesting that the new version of the RDF Semantics document presents, in addition, in Section 7.3.1, a number of entailment rules that are valid (sound but not complete) if the previous iff semantics is considered instead. Best regards, Herman ter Horst ===================================================================== Herman, with reference to your comment http://lists.w3.org/Archives/Public/www-rdf-comments/2003AprJun/0042.html archived as horst-01. First, many thanks for your close attention to the technical matters and your helpful comments, which have required the WG to re-examine several of its earlier decisions. The WG has resolved http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Jul/0025.html to proceed as follows. The RDS semantic conditions on subClassOf and subPropertyOf have been weakened to be 'only if' rather than 'iff' conditions; under these conditions, the entailments that you noted are no longer valid. Details can be checked in the current editor's draft at http://www.ihmc.us/users/phayes/RDF_Semant_Edit_Weak.html#rdfs_interp The document mentions the stronger (iff) conditions under the heading 'extensional semantic conditions' http://www.ihmc.us/users/phayes/RDF_Semant_Edit_Weak.html#ExtensionalDomRang , and describes some inference rules which are valid under these stronger conditions, including rules which cover the case you describe http://www.ihmc.us/users/phayes/RDF_Semant_Edit_Weak.html#RDFSExtRules ; but it does not claim to offer a complete set of such rules for these stronger conditions. A proof of the completeness of the (somewhat shortened) list of RDFS rules http://www.ihmc.us/users/phayes/RDF_Semant_Edit_Weak.html#RDFSRules WRT the weakened semantic conditions is provided in appendix B http://www.ihmc.us/users/phayes/RDF_Semant_Edit_Weak.html#prf . As you will see, most of the complexity of the proof has to do with the treatment of literals; the RDFS rules correspondence is now straightforward since all the semantic conditions map directly into forward implications. Please reply to this message, copying www-rdf-comments@w3.org, indicating whether this response addresses your comment adequately. Sincerely Pat Hayes -- --------------------------------------------------------------------- IHMC (850)434 8903 or (650)494 3973 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32501 (850)291 0667 cell phayes@ihmc.us http://www.ihmc.us/users/phayes
Received on Wednesday, 30 July 2003 14:18:19 UTC