W3C home > Mailing lists > Public > www-webont-wg@w3.org > April 2002

Re: SEM: semantics for current proposal (why R disjoint V?)

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Fri, 5 Apr 2002 14:08:00 +0100
Message-ID: <15533.41392.552131.743764@oaklands.demon.co.uk>
To: Dan Connolly <connolly@w3.org>
Cc: Libby Miller <Libby.Miller@bristol.ac.uk>, "Peter F. " Patel-Schneider <pfps@research.bell-labs.com>, webont <www-webont-wg@w3.org>
On March 21, Dan Connolly writes:
> On Thu, 2002-03-21 at 14:28, Ian Horrocks wrote:
> > On March 21, Libby Miller writes:
> > > >
> > > > As noted in the design discussions for DAML+OIL, I don't
> > > > see sufficient justification for making V disjoint
> > > > from R.
> > > >
> > > > It seems silly not to be able to talk about the intersection
> > > > of two sets of strings, or UniqueProperty's whose
> > > > range is dates, or whatever.
> > 
> > This means that any OWL reasoner has to take on responsibility for
> > reasoning about types
> 
> I gather when you say "OWL reasoner" you mean a complete
> reasoner.
> 
> I'm not very interested in such a thing.
> 
> Regular old horn-clause/datalog reasoners
> (with some built-in predicates like
> string:lessThan and such) seem
> to get me what I need pretty well.

Dan,

It seems that, on the basis of a few toy examples where using ad-hoc
reasoning seems give the results you want/expect, you conclude that
this will be appropriate/adequate for all applications.  I don't find
this argument very convincing. 

Even w.r.t. ontology level reasoning I expect things to rapidly get
large and complex enough that humans wont be able to check all
inferences - we will just have to trust that the reasoner got it
right. Soundness is therefore essential, and completeness highly
desirable. For example, when multiple processes are interacting, some
action may be taken by one process on the basis of a non-inference by
another process, so incompleteness can easily lead to "unsoundness".

As far as the disjointness of object/data domains and properties is
concerned, there are also good pragmatic reasons for this, including
the ability to use hybrid designs for OWL reasoners, i.e., the ability
for an owl "object class" reasoner implementation to "bolt on" a type
checker for arbitrary type systems.

Ian

> 
> So this argument about negation and complete reasoning
> doesn't persuade me that we should keep R and V disjoint.
> 
> > - which could be a major implementation overhead
> > (there are also some technical reasons related to negation - full
> > details can be found in [1]). The current design means that all this
> > can be delegated to a "type system" (the details of which we don't
> > need to consider in OWL).
> > 
> > [1] http://www-lti.informatik.rwth-aachen.de/~clu/papers/archive/lutzdiss.pdf
> > 
> > > >
> > > 
> > > I agree. It's very counter-intuitive to separate them out. I ran into a
> > > lot of problems with this, creating a daml schema for icalendar.
> > 
> > An example would be useful here.
> > 
> > Ian
> > 
> > > 
> > > libby
> > > 
> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
> 
Received on Friday, 5 April 2002 08:10:25 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:57:49 GMT