W3C home > Mailing lists > Public > public-rif-wg@w3.org > January 2006

Re: [SWC] Re: [OWL Compatibility] Re: RIF & OWL compatibility

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Thu, 12 Jan 2006 11:01:52 -0500
To: Enrico Franconi <franconi@inf.unibz.it>
Cc: Jos de Bruijn <jos.debruijn@deri.org>, public-rif-wg@w3.org
Message-Id: <20060112160152.E82B8CB968@kiferserv.kiferhome.com>


Enrico Franconi <franconi@inf.unibz.it> wrote:
> 
> On 12 Jan 2006, at 11:46, Jos de Bruijn wrote:
> >>> Wrt. the existential information: the semantics of LP rules is
> >>> based on
> >>> Herbrand models, which means (among other things) that every
> >>> individual
> >>> in the universe is represented with a name in the language. This  
> >>> makes
> >>> it impossible to truly capture existential information.
> >>
> >> I disagree. For example, In Rosati's approach non-distinguished
> >> varibales (i.e., existentials) are not restricted to the herbrand
> >> universe. BTW all the use cases in Managing Incomplete Information
> >> <http://www.w3.org/2005/rules/wg/wiki/
> >> Managing_incomplete_information> would be correctly handled by
> >> Rosati's approach.
> >
> > Rosati uses the standard names assumption, which excludes considering
> > unnamed individuals, thus, certain kinds of existential knowledge  
> > cannot
> > be captured in his approach.
> 
> As in none LP based approaches.

The question is whether this is a real limitation or that the cases that
can't be captured are too esoteric to worry about.
This issue was raised by me in a different thread on this list.
http://lists.w3.org/Archives/Public/public-rif-wg/2006Jan/0037.html



	--michael  


> 
> > If you have a name for the individual, then you can certainly deal  
> > with
> > it in the logic program.
> > However, if we would take the following example:
> >
> > take the following first-order sentence:
> > \exists x. p(x)
> >
> > and the following rule:
> >
> > r <- p(x)
> >
> > One cannot conclude r, because there is no name a such that p(a).
> 
> In Eiter, the above rule would not derive r, and in Rosati it  
> couldn't even be written since it is not DL-safe. You could  
> automatically make it DL-safe, and then you wouldn't derive r either.
> 
> However, unlike Eiter, and unlike pure LP based approaches, in his  
> recent work Rosati does allow for several kind of classical  
> existentials. For example, the use cases involving OWL-Lite in  
> <http://www.w3.org/2005/rules/wg/wiki/ 
> Managing_incomplete_information> would be captured correctly by  
> Rosati but not by Eiter.
> 
> cheers
> --e.
> 
> 
Received on Thursday, 12 January 2006 16:02:05 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 2 June 2009 18:33:26 GMT