- From: Ivan Herman <ivan@w3.org>
- Date: Thu, 24 Apr 2008 02:25:20 +0200
- To: Sandro Hawke <sandro@w3.org>
- CC: public-owl-wg@w3.org
- Message-ID: <480FD370.5030308@w3.org>
Sandro Hawke wrote: > Here's a possible solution for ISSUE-111 [1], with some variations and > discussion. I was only considering the RDF/XML serialization here. For > the XML serialization, a MIME type could a good solution. > > * Basic Approach: > > Use an ontology property. So the users adds a triple like this: > > <> owl:intendedProfile owl:DL. > > This would have processing-model semantics, much like owl:imports. The > processing model is something like this: > > 1. You fetch the content from some URI U. > 2. If its Content-Type is "application/rdf+xml", proceed. > (otherwise, this procedure doesn't apply; it's not OWL > in RDF/XML.) What about other RDF serializations (current, like Turtle, or others that may come in future?). Would it lead to problems if we cast in concrete the role of RDF/XML here? Ivan > 3. Parse it into an RDF graph. > 4. Look for any triples matching { U owl:intendedProfile ?x } > 5. If there are zero or >1 distict values for ?x, then > this algorithm does not apply. Fall back to whatever > you did before OWL 2. > 6. If you implement the profile named by ?x, use it. > Otherwise, you MAY proceed using some other profile that you do > implement, but you SHOULD warn the user about how the results may > be different. (You may be able to characterize, for the user, how > the results will be different and ask them whether to proceed.) > > That seems pretty simple, and I don't see any problem with it. The key > point is that the failure mode in step 5, which also occurs if you > eliminate the triple by some kind of RDF entailment, leaves us no worse > off than we are in the OWL 1 world. > > Some variations.... > > 1. Allow one to specify multiple profiles. In this sense, they > become more like "Features" or "Semantic Extensions" than > "Profiles". > > <> owl:usesSemanticExtension owl:DL. > <> owl:usesSemanticExtension owl:DL-Safe-Rules. > > 2. Perhaps #1 has to be done with an RDF List, since if it were > done with just more triples, you wouldn't be able to detect the > case where the triple naming some extension was removed. You'd > think you knew the exact intended semantics but would be wrong. > I'm not sure if this is a problem -- we don't seem to mind it > with owl:imports. Anyway, if it's a problem, we can do > something like this: > > <> owl:usesSemanticExtensions ( owl:DL owl:DL-Safe-Rules ) > > 3. Call it "imports", or something like "imports". As a rules user, > it seems perfectly natural to me to say that RDF graphs have only > RDF Simple Entailment until/unless they "import" various > semantics. I picture import as loading the rulebases which > compute entailments under those semantics, but I would expect > that in some cases (eg owl:DL) there would be vastly superior > implementations that simply recognized the owl:DL URI and turned > on their local DL reasoner. > > <> owl:imports owl:DL # this ontology uses DL > <> owl:imports owl:DL-Safe-Rules # and also these > <> owl:imports <some_std_facts>. > <> owl:imports <some_other_ontology>. > > Ideally, one could have an ontology which uses owl:DL and imports > another ontology which use owl:OWL-R. My sense is that allowing that > would complicate matters a lot -- you couldn't just compute the imports > closure and then hand it off to the reasoner! -- so we probably want to > make that an Extra Credit thing for now, saying system MAY do that, but > are also free to simply report an error, that ontologies are being > combined which use incompatible profiles. > > Oh... Another idea: users might want to say "at least" OWL DL-Lite. > > Ontology A: > <A> owl:exactSemantics owl:DL. > Ontology B: > <B> owl:exactSemantics owl:DL-Lite. > Ontology C: > <C> owl:minimalSemantics owl:DL-Lite. > > Now, A+B could only be run by some very clever (impossibly clever?) > system which somehow combined A and B keeping their separate intended > semantics. Is that even well defined? I dunno. Avoid this case. > > But A+C could be handled, no problem, by an owl:DL reasoner. > > ... > > Somewhere in here, it would be nice to tell people they SHOULD NOT (even > MUST NOT?) rely on the places where these various languages are not > neatly stacked semantic extensions. So that, while falling back from > owl:DL to RDFS semantics obviously makes the reasoning incomplete (with > respect to the intended DL semantics), the fact that in some corner > cases it also makes the reasoning unsound..., well, we'd like that not > to cause real-world problems. > > -- Sandro > > [1] http://www.w3.org/2007/OWL/tracker/issues/111 > -- Ivan Herman, W3C Semantic Web Activity Lead Home: http://www.w3.org/People/Ivan/ PGP Key: http://www.ivan-herman.net/pgpkey.html FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Thursday, 24 April 2008 00:26:02 UTC