- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Fri, 24 Mar 2006 08:30:15 -0500 (EST)
- To: kers@hplb.hpl.hp.com
- Cc: semantic-web@w3.org
On Thursday 23 March 2006 16:44, Peter F. Patel-Schneider wrote: > From: Chris Dollin <kers@hplb.hpl.hp.com> > Subject: Re: Interpretation of RDF reification > Date: Thu, 23 Mar 2006 16:24:18 +0000 > > > On Thursday 23 March 2006 15:44, Peter F. Patel-Schneider wrote: > > > Not really. OWL in RDF gives you much more than specialized relations. > > > Much of the power of OWL comes from syntax that is more than just > > > single relations. It so happens that it is possible to embed OWL in > > > RDF in a certain manner. (This is not always possible, by the way, and > > > OWL is very close to the maximum expressiveness that can be so embedded > > > in RDF.) > > > > Could you articulate which bits of OWL semantics are /more/ than the > > semantics given by the meanings of the OWL predicates and classes? > > From > OWL Web Ontology Language > Semantics and Abstract Syntax > W3C Recommendation 10 February 2004 > Section 5 (snipped) That's not ... quite what I meant by an articulation, but I'll brood on it, since the core seems to be: > You will notice that these semantic conditions are not on particular > OWL predicates and classes but are instead on combinations of triples. And: > > > > So if you take the relation owl:inverseOf then this is just an [RDF] > > > > relation. > > > > > > Well, sure, owl:inverseOf is *just* an RDF property, in RDF. In OWL, > > > on the other hand, owl:inverseOf is a special property - it has a extra > > > meaning provided by the OWL semantics. > > > > > > > But it is linked to the following well known rule: > > > > > > > > { ?r1 owl:inverseOf ?r2 . > > > > ?a ?r1 ?b . } => { ?b ?r2 ?a . } . > > > > > > Not all all. There are *no* rules in RDF, nor in OWL. The above is > > > not even legal RDF syntax, nor legal OWL syntax. > > > > The OWL defining document isn't written on OWL, but that doesn't stop > > it defining the OWL semantics. > > Sure, but so what? So documents that aren't written in RDF or OWL can define the semantics of RDF or OWL, eg the meaning of `inverseOf`; so your objection to the rule-snippet quoted above >>> The above is not even legal RDF syntax, nor legal OWL syntax. to the rule-snippet quoted above doesn't seem to hold. > > When I introduce an predicate into my RDF -- say, kers:birthDate -- I > > can explain what that predicate /means/ to people who want to use it. > > I can't state that meaning in RDF, I can't state it in OWL, I can't teach > > the machine what it means - but it's useful because it has that meaning, > > and I can say that the statement `kers:Chris kers:birthDate 1-Jan-2006` > > is false. The /RDF/ semantics doesn't do that, but it doesn't stop me > > doing it. > > Yes, the RDF semantics doesn't do that, and the RDF semantics is all there > is to RDF itself. You are adding your own intended meaning to the things > you write. There is nothing wrong with this, in fact, it is pretty much > required to proceed at all. However, you do need to know that your > intended meaning is not part of RDF, and that others who read your RDF are > not obligated to put your intended meaning on it. Of course. And neither am I obliged to put the intended OWL meaning on an OWL predicate. Whether or not I do is a pragmatic matter, just as is whether or not someone(s) accept and use my definition for kers:birthDate. Isn't it? -- Chris "x.f(y) == f(x, y) == (x, y).f" Dollin The shortcuts are all full of people using them.
Received on Friday, 24 March 2006 13:31:00 UTC