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Re: WOWG: Report from WWW 2003 - OWL presentation/issues

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>
Message-Id: <1054826822.906.1174.camel@dirk.dm93.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

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