- From: Pat Hayes <phayes@ai.uwf.edu>
- Date: Wed, 24 Apr 2002 21:22:26 -0500
- To: www-webont-wg@w3.org
A few more observations about the owl:Dark proposal (http://lists.w3.org/Archives/Public/www-webont-wg/2002Apr/0290.html). Given an RDF graph G, consider the subgraph containing all the triples in G that do not contain any uriref that occurs as the subject of a triple of the form aaa rdf:type owl:Dark . which is rdfs-entailed by G, ie which is in the rdfs-closure of G. Call this the 'light' subgraph of G, light(G). Any RDF graph has a unique light subgraph which can be figured out by an RDFS reasoner. (This allows implicit 'darkening', eg by defining an rdfs:subClassOf owl:Dark and asserting something to be in the subclass, or by using rdfs:range. An alternative proposal would be to require the triple to occur in the graph explicitly. While syntactically simpler, that would complicate the relationship between RDFS and OWL since drawing a valid conclusion in RDFS could alter the 'darkness' of the vocabulary. ) The desired semantic relationship between the languages can then be stated as the condition: Any satisfying OWL-interpretation of G is a satisfying rdfs-interpretation of light(G). Lemma: If S rdfs-entails G, then light(S) rdfs-entails light(G). This means that drawing valid RDFS conclusions from some OWL (even on the 'dark' vocabulary) isn't going to produce any unwanted conclusions. It might produce some conclusions that are dark, but it isn't going to produce any light ones that it shouldn't produce, ie that OWL would find embarrassing. More later, hopefully with some test cases. Pat -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Wednesday, 24 April 2002 22:22:28 UTC