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Re: more on RIF entailment regime

From: Chimezie Ogbuji <ogbujic@ccf.org>
Date: Thu, 25 Mar 2010 10:24:47 -0400
To: "Axel Polleres" <axel.polleres@deri.org>, "SPARQL Working Group" <public-rdf-dawg@w3.org>
Message-ID: <C7D0EA6F.10830%ogbujic@ccf.org>
On 3/25/10 4:34 AM, "Axel Polleres" <axel.polleres@deri.org> wrote:
> "Without appropriate safety conditions, cyclic references can rule out the
> existence of a single intended Herbrand model of the combination and indeed
> various stratification and stable model theories [STABLEMODEL] have been
> defined in the literature that use a dependency graph to determine if a
> ruleset is stratified and incorporate the restricted use of built-in function
> symbols that allow the truth of a predicate to be well-defined by an external
> procedure.  This entailment regime restricts the legal graphs to only those
> that refer to strongly safe RIF core documents. This excludes the use of
> negated (non-monotonic) atoms and cyclic references between terms in
> built-ins."
> I think this paragraph might confuse. Stable models, stratification, etc. are
> only vaguely related to the issue we face here, since they are usually only of
> interest in the context of rule languages with (non-monotonic) negation.

The cyclic restrictions of stable models and stratification are of the same
kind used in the RIF Core strong safety conditions (whether or not they are
used for negation).  This paragraph (and reference) was meant to describe
how (traditionally) these kind of restrictions are used and how they are
leveraged to ensure finiteness.
-- Chime


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Received on Thursday, 25 March 2010 14:25:42 UTC

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