- From: Jeff Heflin <heflin@cs.umd.edu>
- Date: Mon, 13 Nov 2000 13:53:48 -0500
- To: www-rdf-logic@w3.org
Deborah, Here are a few more comments on your proposed semantics for DAML-ont: 1) The "imports" statement is lacking semantics. The intent of "imports" is so that you can say the current ontology or document includes the rules and definitions from some other ontology. I imagine in order to define this formally in KIF, you would need to add something like the "ist" predicate (meaning "is true in") from context logic (see McCarthy's and Guha's work). Assuming you had such a predicate, where the first argument was an ontology, the second a predicate name, and the rest arguments of that predicate, you might add this rule: (=> (imports ?o1 ?o2)(ist ?o2 ?p ?a1 ?a2) (ist ?o1 ?p ?a1 ?a2)) Note that we could also add a rule that says imports is transitive, but this can be deduced from the above rule and the definition of ist. 2) The following is used for the definition of "domain": %% The object in an RDF statement of the form "(object property resource)" %% must be an instance of the domain of property. (=> (Property ?p)(domain ?p ?d)(holds ?p ?x ?y)(type ?x ?d)) This implies that if there is more than one domain stated for a property, that the "object" must be an instance of the intersection of these domains. However, the RDF Schema spec states "If there is more than one domain property, the constrained property can be used with instances of ANY of the classes..." That is, the "object" must be an instance of the union of the domains. Personally, I like your definition better. If you use the RDF schema definition, then it becomes possible to extend an ontology in such a way that content marked up with respect to new ontology is incompatible with the extended ontology. Also, the RDF definition is meaningless (i.e., you cannot deduce anything from it or perform type checking) unless you can close the world and guarantee that there do not exist any more domain statements for the property in question elsewhere on the Web. I think this is a case where it is worth deviating from RDF, but would like to hear the opinions of others. Jeff
Received on Monday, 13 November 2000 13:53:51 UTC