- From: Dan Connolly <connolly@w3.org>
- Date: 05 Jun 2003 10:27:02 -0500
- To: Christopher Welty <welty@us.ibm.com>
- Cc: webont <www-webont-wg@w3.org>
On Thu, 2003-06-05 at 09:58, Christopher Welty wrote: > Jeremy, > > I've argued this with Pat several times. I'd like to see an > authoritative definition of what "first-order" means, otherwise we're > all using our own definitions. In any dictionary of logic or > philosophy or mathematics that I've been able to find, "first-order" > is defined as "not higher order" and "higer order" is defined as > predication of predicates (or functions of functions). > > Until someone produces an authoritative definition of first-order that > says something else, I don't think it's ever "simply incorrect" to > call RDFS higher-order. It is "simply" correct. It may be incorrect > according to your (or Pat's) more complicated definition of what > first-order means, but that is by no means "simple"! > > I have claimed from the start that a useful distinction here is to say > that RDFS is syntactically higher-order and semantically first-order. > Pat has not agreed. > > More to the point, I believe it to be the case that RDFS is > undecidable (has this been proven?) on the contrary; that RDFS is decideable is so clear that nobody has bothered to prove it. The deductive closure of an RDFS KB is finite. You can work it out with a pencil. > , and certainly OWL DL is decidable (has this been proven?). > Therefore I think it may be more useful to make the diagram look like > this: > > RDFS -> (decidable fragment of RDFS) -> OWL Lite -> OWL DL -> OWL Full > +--------------------------------------------------------------^ -- Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 5 June 2003 11:26:36 UTC