- From: Pat Hayes <phayes@ihmc.us>
- Date: Fri, 10 Aug 2007 12:33:41 -0500
- To: Alan Ruttenberg <alanruttenberg@gmail.com>
- Cc: Bijan Parsia <bparsia@cs.man.ac.uk>, "Michael Schneider" <m_schnei@gmx.de>, public-owl-dev@w3.org, bmotik@cs.man.ac.uk
>Thanks Pat, > >Followup question in line > >On Aug 9, 2007, at 1:41 PM, Pat Hayes wrote: > >>>Does it break it, or does it make the OWL-1.1 entailments only be >>>a subset of OWL-Full entailments. >>>If it breaks, could you say how please? >> >>Peter Patel-Schneider has made the point. RDF semantics is in line >>with CL semantics by interpreting names as individuals, and >>allowing individuals to act as classes and properties by mapping >>them to class and property extensions. This has the consequence >>that A=B means they are equal in every way, including as classes >>and as properties. 1.1-style punning maps each name to individuals, >>classes and properties separately, with no semantic association >>between these three denotation mappings. This allows the names A >>and B to have any pattern of identity, including being equal but >>not equal as classes, which is impossible in RDF or CL. > >In RDF this isn't possible anyways, is it, since there is no way to >express that two individuals are the same, is there? True. But there is in OWL-level languages and above, so the question arises of whether equality is congruent with what the RDF semantics says is identity. >CL is a point of interest, but I'm not sure how germane it is to a >discussion of OWL. Well, I have a side axe to grind here, in that I want the W3C standards to be at least compatible with the CL ISO standard. Quite a lot of people in Government agencies are very keen to use an ISO standard when one is available, so it would I think be a mistake to break the link to CL casually, if it is easy to keep it by a relatively small change. But also, we have found in several recent projects that the CL semantic (and syntactic) 'style' has a lot of operational advantages. And more basically still, to me, the idea that things can be the same thing yet at the same time different classes, just seems semantically incoherent. It doesn't make intuitive sense. The fact is, one simply cannot have a logical equality in the punning semantics: but equality is a very basic notion, and is widely thought of as part of the fundamental apparatus of logic like the quantifiers or connectives. So the fact that it is incommensurate with the punning semantics strongly suggests that there is something basically wrong with the latter. OK, I concede that this is only a theoretician's intuition, but it is a very strong one, and I tend to rely on intuitions like this. > >Also, would this situation (A=B misses entailment >equivalentClasses(A,B) and equivalentProperties(A,B)) not fit my >characterization that the relation of OWL 1.1 to OWL Full is that >OWL 1.1 is missing some entailments that would be concluded using >OWL Full semantics? > >>One cannot build the 'punning' style semantics as a semantic >>extension of the CL-style model theory. One also cannot have >>genuine logical identity in the punning style semantics. (You can >>imitate it in OWL 1.1 by saying that it means (sameIndividual AND >>sameClass AND sameProperty), but this hack won't extend to richer >>logics and so will have to be redefined over and over again.) > >I think this answers the reverse question, namely can OWL 1.1 be >considered a semantic extension of OWL Full. I was asking if >OWL-Full can be considered a semantic extension of OWL 1.1. Yes, it can. If one imposes the extra condition that sameIndividualAs always entails all the other identities, then the punning semantics becomes isomorphic to the RDFS/CL-style semantics. But this makes OWL 1.1 into a kind of sub-logic rather than a real logic. I think its important to get the basic logic of the Web as intuitively semantically clear as possible, independently of considerations of efficiency for reasoners. If it turns out that nobody at Manchester or anywhere else knows how to make an efficient, complete theorem-prover for the language, then let them publish the deficiencies of their software clearly and tell people how to avoid them: but don't warp the basic communication language of the SWeb to fit the current state of the inference-engine art (which is in any case a constantly moving target.) Well, now you know what I think, anyway :-) Pat > >Thanks, >Alan > >> >>Pat >> >>>-Alan >>> >>>On Aug 9, 2007, at 12:23 PM, Pat Hayes wrote: >>> >>>>Not really. Im sure it was meant to have this intention, but the >>>>effect of moving to punning is two-fold: it breaks the OWL Full >>>>semantics, and it breaks the semantic connection between OWL and >>>>RDF. Neither of which are desirable, IMO, though both of them are >>>>in line with a certain perspective that has long been associated >>>>with Manchester >> >> >>-- >>--------------------------------------------------------------------- >>IHMC (850)434 8903 or (650)494 3973 home >>40 South Alcaniz St. (850)202 4416 office >>Pensacola (850)202 4440 fax >>FL 32502 (850)291 0667 cell >>phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes -- --------------------------------------------------------------------- IHMC (850)434 8903 or (650)494 3973 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 cell phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
Received on Friday, 10 August 2007 17:33:55 UTC