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RE: RIF and QL

From: Gerd Wagner <wagnerg@tu-cottbus.de>
Date: Sat, 28 Jan 2006 13:51:20 +0100
To: "'Peter F. Patel-Schneider'" <pfps@inf.unibz.it>, <jos.deroo@agfa.com>
Cc: <public-rif-wg@w3.org>
Message-ID: <001a01c62409$8f2351c0$17d52b8d@TMGWAGNER>

>> I would have thought that
[my rewriting:]

{ p v q => r. }


{ p => r. q => r. }

>> are equivalent rulesets, no?
> Well obviously not at least in some readings, as they produce 
> different answers.

Their equivalence (according to the principle called 
"disjunction in the premise") is generally valid in all 
kinds of standard logics if "=>" is read as the implication 
connective. And it also holds in disjunctive logic programs. 

However, they may not be equivalent, if "=>" is read as a 
rule operator (not an object language symbol) having the 
epistemic flavor of requiring the condition to be "known"
(it's not the same to know just p v q or to know p or q).

Since we are assuming standard classical logic (do we?),
reading rules as plain Horn formulas, Jos is right.


Gerd Wagner 
Brandenburg University of Technology 
at Cottbus, Germany
Received on Saturday, 28 January 2006 12:54:20 UTC

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