From: Harold Boley (boley@informatik.uni-kl.de)
Date: 03/18/03
Hi JC Colleagues, Peter started today's discussion on using OWL in its favorite (perhaps XML-based) syntax and using subClassOf of RDFS for encoding the DL-generated class hierarchy in a second document type. Both can be regarded as 'terminological documents' (T-Docs, webized T-Boxes). As we had discussed earlier (http://www.dfki.uni-kl.de/ruleml/rdf/ruleml-rdf.pdf), RuleML derivation rules (e.g., webized Horn rules) can then access such an RDFS class hierarchy, via urirefs, for variable typing. Similarly to a DL classifier generating an extensional class lattice from a set of intensional class definitions, a (bottom-up/forward) rule engine generates instance descriptions / facts via derivation rules. Both facts and rules can be regarded as 'assertional documents' (A-Docs, webized A-Boxes) [although rules may also be viewed as separate 'inferentional documents' (I-Docs, webized I-Boxes)]. A second link between the T-Doc and A-Doc layers is urirefs pointing from constants (often URIs) in instance descriptions / facts 'up to' the extensional class lattice, e.g. via rdf:type. Finally, Benjamin's and Ian's description logic programs explore direct connections between derivation rules and intensional class definitions. In summary, we get this picture: T-Docs: Intensional Class Definitions Extensional Class Lattice (in OWL, queried by DQL) --generate--> (in RDFS) ^ ^ ^ | | | Description | | | | urirefs for typing variables | | urirefs for Logic | | | typing constants | --------------------------------- | Programs | | | | | | | | | A-Docs: v | | Derivation Rules Instance Descriptions / Facts (in RuleML) ---------------generate--> (in OWL, RDF, RuleML, DBs, ...) A version of this picture might help us keeping together the different KR communities and 'cultures' that have been developing languages for the Semantic Web. Best, Harold
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