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Re: Merging Rulesets

From: Sandro Hawke <sandro@w3.org>
Date: Fri, 26 Aug 2005 17:52:35 -0400
To: Michael Kifer <kifer@cs.sunysb.edu>
Cc: jos.deroo@agfa.com, Christian de Sainte Marie <csma@ilog.fr>, dieter.fensel@deri.org, public-rule-workshop-discuss@w3.org
Message-Id: <20050826215237.DF2F94EF93@homer.w3.org>

> > Michael Kifer writes:
> > >             Merging rules is a whole different ball of hair. As far as I
> > > can tell, logical reasoning (monotonic or nonmonotonic) is not what you
> > > would use here. This is an intellectual activity, which can be automated
> > > with the help of heuristics (which are not logical inference rules),
> > > machine learning, etc.
> > > 
> > > I bet, however, that **if** you decide to encode those rule-merging
> > > heuristics in a rule-based language (and not in Java, for instance) then
> > > you would prefer a Prolog-like language with S/NAF rather than FOL.
> > 
> > The Semantic Web applications I'm familiar with (including everything
> > based on cwm, some of my prolog work, and various things I hear about)
> > all merge rulesets freely by just puting them together (concatenation,
> > set-union, conjunction, etc).  It's trivial with RDF, OWL, N3, and FOL
> > (when you use URIs for names).   It sounds like it might be very hard
> > or impossible with rules written in a non-monotonic language.
> 1.  N3, as I hope we have established by now, is nonmonotonic.

Not at all.   At most we have established that it's semantics are
unclear.  :-)    By design it is meant to be monotonic.

> 2.  Merging rules by concatenation is trivial in Prolog and languages like
>     Flora-2, which allow for rule reification.

Of course if you use any CWA/NAF features in prolog you'll get the
wrong results if you merge by concatenation (with worst-case

> When I mentioned heuristics for merging rules I was talking about more
> interesting issues. You can view schema merging as a special case of rule
> merging. You wouldn't do this by just unioning schemas.
> > Is this the root of all the tension around NAF/LP/etc?
> Root of tension? I don't see any tension. The issue is understanding what
> paradigm suits what tasks, and I don't see this understanding among some of
> the proponents of FOL, cwm, N3, etc.

Then please do explain how to address the merging described in the use
cases in the draft charter, with a non-monotonic logic.

      -- sandro
Received on Friday, 26 August 2005 21:52:47 UTC

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