- From: Drew McDermott <drew.mcdermott@yale.edu>
- Date: Wed, 8 May 2002 20:29:54 -0400 (EDT)
- To: www-rdf-logic@w3.org
Jeff's response to Pat's "dream world" comment reminded me that I hadn't responded. [Jeff Heflin] >In terms of merging RDF graphs, daml:imports means you can't add that >triples from some graph unless you also add all the triples from the >graphs of the resources that are imported. [Pat Hayes] But wait a minute. What does it even mean for your ontology to say what my reasoning engine can or cannot do? Of course I CAN add triples from one graph without adding triples from another. All that any ontology can do is to express some propositional content. What another engine does with that content can be reasonably expected to conform to the semantics of the language, but that's about all. If the engine decides to ignore some of what you say, that's it's business, not yours. Ignoring part of any RDF graph is perfectly valid considered as an inference, after all: an RDF graph entails all its subgraphs. I would disagree with Jeff on technical grounds: the daml:imports statement states what is *not* to be included, as opposed to what *must* be included. That is, it points to a DAML+OIL document, and says that any triple outside this document is not encompassed by the import unless specifically authorized by daml:imports within that document. As I've said elsewhere, this leaves open the possibility that the document uses proper-name URIs from other, unimported documents. However, pragmatically, Jeff has a point: If my inference engine fails to draw an inference, and the inference follows from premises I have in hand plus stuff from an imported ontology, I can't call up the tech-support staff for the ontology and expect much if the conversation goes like this: Me: "My inference engine didn't conclude P when it clearly follows from premises Q1 and Q2. Q1 is in my local dataset, and Q2 is in your ontology, which my dataset imports." Tech Support: "What exactly does your inference engine do with Q2?" Me: "Oh. It ignores it. Pat Hayes said I was free to do that, and it did make the implementation of my inference engine much simpler." Tech Support: <dial tone> [Pat] I think this entire discussion is in a dream world. First, there are no clear notions of definition to appeal to. And none needed. Second, no ontology can restrain the actions of a remote inference engine. True but irrelevant. Third, why would one want things to be different? Because it's not a matter of "restraining" anyone. If ontologies are posted with well-defined semantics, and people advertise inference engines that claim to use those ontologies, then consumers should have a reasonable expectation that the inference engines respect the semantics and draw mostly useful inferences that mostly don't require an exponential amount of work. It's in everyone's interest to play by the rules. Am I missing something? -- Drew McDermott
Received on Wednesday, 8 May 2002 20:29:57 UTC