- From: Jonathan Borden <jonathan@openhealth.org>
- Date: Thu, 12 Jun 2003 19:31:09 -0400
- To: "Jim Hendler" <hendler@cs.umd.edu>, "pat hayes" <phayes@ihmc.us>
- Cc: <www-webont-wg@w3.org>
Pat, May I summarize your post by saying that owl:Class and rdfs:Class need to be distinct because the concepts of "Class" in OWL-DL and RDFS are distinct? If so, what about owl:Class in OWL-DL vs. OWL-Full? Ought not OWL-Full be defined using rdfs:Class? If so, when using OWL-Full should owl:Class retain its OWL-DL meaning? Doesn't this 'break' layering? (perhaps I am being naive?) It seems to me that the meaning of owl:Class does depend on whether we are using OWL-DL vs. OWL-Full in which case the meaning of the URIref depends on the framework we are using ... in which case could not the 'meaning' of rdfs:Class depend on whether we are using OWL-DL vs. OWL-Full/RDFS? however, >... > And then with these assumptions, we can identify the OWL and RDFS > universes. This hybrid is called OWL Full. It allows the same > syntactic freedom as RDFS - it is in fact an RDF semantic extension > of RDFS - and Peter has proven an ingenious theorem to the effect > that if one restricts oneself to the OWL-DL syntactic case, then > being in OWL-DL and being in OWL Full are indistinguishable states, > as it were, so that OWL-DL is a genuine sublanguage of OWL Full, > which itself is a genuine RDFS semantic extension. > > However, notice that there is a genuine tension here. This Full > hybrid asserts that the OWL and RDFS universes are identical; but > they are not, if we understand the OWL terminology according to > OWL-DL. So OWL Full is constructed so that *either* it must be > incommensurate with OWL-DL - ie the OWL terminology must have > different meanings in the two versions of OWL - *or* it is a > restriction of RDFS to the OWL-DL universe, which makes it > incommensurate with much of RDFS - for example, many RDFS logical > truths will be false in OWL Full, under this interpretation. So OWL > Full either breaks with OWL-DL, or amounts to a grand claim that the > entire RDFS universe must be understood as conforming to the limited > OWL-DL 'layered' framework. > > It is easy to see that both versions of OWL (DL and Full) could > safely, each in their own terms, merge the concepts of owl:Class and > rdfs:Class without actually breaking 'internally': OWL-DL could > because it is simply unable to express the ways that RDFS classes > differ from OWL classes - what might be called a 'thought police' way > of making the vocabularies similar - and OWL Full could simply > because it is simply asserts that they are identical. But as I hope > the above makes clear, this assertion would be troublesome for any > kind of consistent interaction between OWL-DL and other RDFS > applications. For example, if OWL-DL were to use the > rdfs:Class/Resource/rdf:Property terminology while in fact referring > only to the OWL-DL subsets of these classes, then OWL-DL theorems > would become sharply false when transcribed into RDFS, and vice > versa; for example, > > _:x rdf:type _:x . > _:x rdf:type rdfs:Class . > > is logically true in RDFS (by rules se1 and se2 from the > self-membership of rdfs:Class) but would be a logical contradiction > in OWL-DL if rdfs:Class were identified there with owl:Class. Again, > many other examples could be given. > Understood, but what about 'translating' between OWL-DL and OWL-Full -- same problem??? e.g. _:x rdf:type _:x . _:x rdf:type owl:Class . logically true in OWL-Full, but contradiction in OWL-DL? (I am assuming that since owl:Class and rdfs:Class have the same extensions in OWL-Full and RDFS, that rules se1 and se2 for rdfs:Class apply to owl:Class.) Jonathan (who doesn't really have a clue about this, but ...)
Received on Thursday, 12 June 2003 19:31:17 UTC