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Re: FOL versus Rule Languages - A tutorial

From: Sandro Hawke <sandro@w3.org>
Date: Sat, 27 Aug 2005 01:06:06 -0400
To: Michael Kifer <kifer@cs.sunysb.edu>
Cc: doug.foxvog@deri.org, Dieter Fensel <dieter.fensel@deri.org>, public-rule-workshop-discuss@w3.org, Christian de Sainte Marie <csma@ilog.fr>
Message-Id: <20050827050610.2182B4EEBF@homer.w3.org>


> > > MMS is non-monotonic in that anything that cannot be proved
> > > true in MMS is concluded to be false.  Adding any (non-provable)
> > > ground statement or rule to a Herbrand model, limits the Herbrand
> > > space and falsifies the conclusions that various statements are
> > > false obtained from the earlier model.
> > 
> > So MMS necessarily brings with it the CWA?
> > 
> > I guess Flora-2 and Triple do this in a clever way, so they have MMS
> > but their CWA is somehow scoped?
> 
> Actually, there is nothing really clever in what Flora-2 or Triple do. :-)
> What they do is not a semantic trick, but a syntactic one.  They allow the
> user to specify the scope of any inference (positive or negation)
> explicitly, but the semantics remains like in traditional systems.
> (Actually, Triple didn't have SNAF originally -- only positive scoped
> inference. I am not sure if some later versions of Triple have default
> negation, but this is not important here.)
> 
> I already hinted at how this is done when discussing Dan's example.
> Basically, every rule-head (or fact) defined in a particular module
> is treate d as a predicate with a prefix that is specific to that
> module, and different modules have different prefixes. In this way,
> if you ask a negated query against any predicate in a given module,
> then NAF and SNAF give the same result because nothing outside of
> the module matters due to the uniqueness of the predicate names that
> are local to that module.

Can one also define shared/global predicates, for which facts are
allowed to come from multiple sources?  I imagine S/NAF would not be
available for them?

      -- sandro
Received on Saturday, 27 August 2005 05:06:13 GMT

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