- From: Jeremy Carroll <jjc@hpl.hp.com>
- Date: Thu, 14 Jun 2007 16:03:31 +0100
- To: Alan Ruttenberg <alanruttenberg@gmail.com>, Owl Dev <public-owl-dev@w3.org>
Hi Alan following up from our chat yesterday, (but note public list), you mentioned how some of the possible constructs in OWL Full seemed totally useless and just plain confusing. Two you mentioned were: what would rdf:type rdf:type rdfs:Class . mean? And what would: restriction( owl:imports, minCardinality(4) ) mean? The general OWL Full mentality, is to allow people to say things, including unhelpful things, and then to take a garbage-in garbage-out type approach. For instance, earlier today I have been answering a question on the jena support list concerning an intersection of a class and a datatype property: unsurprisingly not what was intended. But, it has occurred to me that the restriction on owl:imports is, in fact, plausibly useful in some cases. Here goes: I have been investigating improving Jena's performance. A possible area of investigation is how well does Jena perform when a large number of imports have been made. As long as each ontology is a semantically distinct thing then restriction( owl:imports, minCardinality(4) ) is the class of ontologies that have imported at least 4 ontologies. This may be a useful class of ontologies to concentrate my performance tests on. To make that work within a reasoner, I would have to augment the formal OWL Semantics, perhaps, to make uri1 rdf:type owl:Ontology uri2 rdf:type owl:Ontology uri1 owl:sameAs uri2 into a contradiction (when uri1 and uri2 differ). This would reflect some sense of the meaning of the uri of an ontology being its (unique?) name. I believe that would be a compliant extension to the semantics (although not one that I would propose for standardization). Probably to answer the most useful question in this case I would want a transitive superproperty of owl:imports, and then ask the minCardinality question: this would give me a class of ontologies whose import closure is large. ===== I am not trying to claim that this is an important use case, that must be addressed - I am more trying to articulate a mentality: we have a powerful tool for describing resources on the web and their relationships - it can be used to help with a number of tasks. The limitations of OWL DL guarantee certain computational properties, but at the cost of syntactically prohibiting certain constructs, most of which do not address the main tasks of traditional ontologies. It doesn't mean that such constructs are useless. Jeremy -- Hewlett-Packard Limited registered Office: Cain Road, Bracknell, Berks RG12 1HN Registered No: 690597 England
Received on Thursday, 14 June 2007 15:04:08 UTC