- From: Bijan Parsia <bparsia@cs.man.ac.uk>
- Date: Thu, 17 Jan 2008 16:58:01 +0000
- To: "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>
To go a bit further in this vein, it's pretty clear that the semantics are primary, not the conformance levels. I presume that the reason we have entailment tests, for example, in Old Owl is to test whether the semantics have been respected. Given a sensible semantics, the need for speccing conformance per se for entailment is lower since we have known definitions. You respect the semantics by having your entailment services respect that semantics. Furthermore, there is support (e.g., Sandro voiced it at the F2F and I saw nods; Peter just voiced it; I hereby voice it) for supporting conformance levels to help interoperability of systems in what they actually do for users and help guide implementors. Core services for OWL DL users are classification and realization, both forms of entailment. That's *the point* of selecting ontology languages like OWL (e.g., see Alan Rector's very illuminating presentation: <http://rease.semanticweb.org/ubp>). Future query languages (which are coming soon) involve entailment. How does it help mitigate user surprise for them to load an ontology up, get the same consistency results, then classify and get different class hierarchies from Pellet and from FaCT++? "Oh, well, y'know, we conform to *owl* which is designed so that it doesn't say anything about entailment, sorry." It's hard to see how we can make conformance games work for this issue. Usually, you muck with conformance in order to help implementors, not to help spec writing (e.g., making something optional if some system couldn't reasonably adapt to i t). On the other hand, if you don't care about entailment, it's hard to see why you think it's important to maintain variable *semantics*. Why not change OWL Full to skolem semantics as well? It would arguably simplify the semantics presentation. Cheers, Bijan.
Received on Thursday, 17 January 2008 16:56:07 UTC