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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. }

and

{ 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

--------------------------------------------
Gerd Wagner 
http://www.informatik.tu-cottbus.de/~gwagner
Brandenburg University of Technology 
at Cottbus, Germany
Received on Saturday, 28 January 2006 12:54:20 GMT

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