- From: Jeen Broekstra <jeen.broekstra@aidministrator.nl>
- Date: Fri, 1 Feb 2002 12:55:28 +0100 (MET)
- To: www-rdf-comments@w3.org
- cc: Arjohn Kampman <akam@aidministrator.nl>, Frank van Harmelen <frankh@cs.vu.nl>
Dear all, We have recently been implementing a new inferencer for Sesame, that uses the RDFS entailment rules as specified in the MT working draft. While testing this, we came across two issues with the current set of rules. In rule #8, it is stated that any class is a subclass of Resource. Applying this rule in practice resulted in rdfs:Literal also being defined as a subclass of Resource. We are aware that this is an open issue within the RDF Core WG. The current spec still defines Literals as disjoint from Resources, however. Is the MT assuming the issue will be resolved in this fashion, or has this simply been overlooked? This issue has also been raised in the "Compatibility Guide" by Wolfram Conen and Reinhold Klapsing[1], but we thought it would be a good idea to point it out again, to stress that this is encountered in practical applications. Another issue is that of reflexivity of the subClassOf relation. The RDF Core WG has resolved that cycles are allowed in subClassOf hierarchies. Reflexivity of the relation seems a natural consequence of this, since it is in a sense the most trivial form of a cycle. Nevertheless, this is not captured in the current entailment rules. Would it be a good idea to add a rule #8a: if E contains: xxx rdf:type rdfs:Class then add: xxx rdfs:subClassOf xxx to make the schema closure complete (and a similar rule for subPropertyOf, of course)? This is compatible with the rest of the MT since it is explicitly stated that the subset relation need not be proper (i.e. the subset can be equivalent). Best regards, Jeen Broekstra and Arjohn Kampman [1] http://nestroy.wi-inf.uni-essen.de/rdf/new_interpretation/RDFS-LogInt_v10.pdf -- jeen.broekstra@aidministrator.nl aidministrator nederland bv - http://www.aidministrator.nl/ julianaplein 14b, 3817 cs amersfoort, the netherlands tel. +31-(0)33-4659987, fax. +31-(0)33-4659987
Received on Friday, 1 February 2002 06:55:41 UTC