Re: [SWC] RIF & OWL compatibility

On Thu, 2006-01-12 at 11:06 -0500, Michael Kifer wrote:
> "Gerd Wagner" <wagnerg@tu-cottbus.de> wrote:
> > 
> > Enrico and Jos,
> > 
> > yes, the issue of existential information is interesting
> > (and also in the field of databases there is no consensus
> > about null values being a good idea or not), but is it 
> > really an urgent issue for RIF? 
> > 
> > Some form of null values (or "blank nodes" or skolem 
> > constants/terms) may be useful, but probably not needed 
> > in phase 1. Do you know of any non-experimental (if not 
> > commercial) rule system that supports existential 
> > information?
> > 
> > The differences between a constructive LP-style 
> > interpretation of the existential quantifier and 
> > the non-consructive classical logic and DL-style 
> > interpretation seem to be even less relevant for
> > RIF than the issue itself.
> > 
> > -Gerd
> 
> Exactly. From talking to a number of people with real-world RDF experience,
> I get the impression that b-nodes are used to refer to individuals when it
> is too inconvenient to give them explicit names. This is just Scolemization.
> 
> Does anybody have *real-world* RDF experience with cases where truly
> existential semantics of b-nodes is used?

When considering OWL rather than RDF, we see a lot more use of
existentials. The question is really what to do with them.
We could limit OWL in certain ways, as Enrico pointed out with the
standard names assumption, and have interaction between the DL ontology
and the logic program on a model level, as Rosati demonstrated.
We could also limit ourselves to the exchange of ground consequence, as
proposed by Eiter et al., so that we can reuse existing reasoners.


Best, Jos

> 
> 
> 	--michael  
> 
--
Jos de Bruijn,        http://www.debruijn.net/
+43 512 507 6475         jos.debruijn@deri.org

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