- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Mon, 16 Oct 2000 09:31:37 -0400
- To: connolly@w3.org
- Cc: www-rdf-logic@w3.org
From: Dan Connolly <connolly@w3.org> Subject: Re: comparing DAML-ONT and OIL (was Re: semantics of daml) Date: Sat, 14 Oct 2000 22:59:58 -0500 > "Peter F. Patel-Schneider" wrote: > > > > Peter Patel-Schneider > > > > OIL-Standard DAML 1.2 > > > > Semantics denotational English > > complete, unambiguous partial, ambiguous > > I expect that eventually we can change that DAML entry > here to "provided by OIL", but I haven't finished > studying the OIL denotational semantics. > > TODO: see if OIL denotational semantics agree with > my understanding of DAML. OK, this would be a good thing, but then why not have presented DAML with such a semantics from the start? > > Meaning of a collection always conjunctive usually conjuctive > > of statements sometimes disjunctive > > (domain from RDF) > > I consider RDF to be always conjunctive; the suggestion > (in the RDF spec) that domain is disjunctive is > disputed; one of the RDF schema spec editors > agrees that it's bogus: If DAML-ONT is going to use stuff from RDF that is suspect in some way, then there should be comments in the DAML-ONT document to the effect that either 1/ DAML-ONT will not use RDF in a way that will trigger the suspect behaviour or 2/ DAML-ONT depends on a change to RDF By the way, the most-recent RDF specification has no hint that domain will be changed. > > Equivalence yes (defined classes) maybe > > I hope you consider this one "yes" by now. No I certainly do not. There have been comments that eequivalentTo should be read as an aliasing mechanism. > > Individuals yes yes > > I'm not sure I understand what Individuals are; cf > "universe of discourse" above. Individuals are, well, individuals. Things like Joe and Mary and a rock. Some systems only allow classes. There are lots of related issues, such as whether a class is also an individual, and whether there are things like metaclasses. > > Reasoning > > > > Specification complete incomplete > > > > Completion Possible no no > > Least Partial Model no no > > > > Difficulty EXPtime complete (?) unknown, at least NP hard > > How do you conclude that DAML reasoning is at least NP hard > without a specification for it? OK. OK. There might be a reading for the DAML-ONT constructors that makes reasoning easy. However, the only readings that I could construct do make some reasoning hard in DAML-ONT. I will produce (shortly) a longer message making this point slightly more formally. > Could you point me toward a specification for Least Partial > Model? I learned about models a few months ago, and I > was able to record my understanding in larch[fs] > so I'm fairly confident I understand it, but > I didn't run across the term "Least Partial Model". Least Partial Model may not be a common term, but it does get used in some places. Perhaps the easiest way to show what I mean is to look at a database, but without the closed world assumption. Then there are many possible models for a database, but there is a canonical, or least, partial model, namely the positive portion of the normal (closed world) model for the database. On the other hand, most disjunctions don't have this sort of model. For example ``it is Tuesday or it is raining'' has two possible small models, one for each of the disjuncts and no least partial model. The best work on this that I have seen was some stuff that Hector Levesque did about 10-15 years ago. Peter Patel-Schneider
Received on Monday, 16 October 2000 09:32:03 UTC