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Safe rules in SWRL

From: Enrico Franconi <franconi@inf.unibz.it>
Date: Thu, 4 Nov 2004 16:56:21 +0100
Message-Id: <12918E82-2E7A-11D9-8D8F-000A9575BDDE@inf.unibz.it>
To: www-rdf-logic@w3.org

Hi.
 From the latest SWRL document:
"As usual, only variables that occur in the antecedent of a rule may
occur in the consequent (a condition usually referred to as "safety").
This safety condition does not, in fact, restrict the expressive power
of the language (because existentials can already be captured using OWL
someValuesFrom restrictions)."

I believe that the safety condition does restrict the expressive power
of the language, since a rule with a conjunction of atoms in the
consequent with joint existential variables can not be transformed into
multiple rules each with an atomic consequent. Moreover, even in the
case of a rule with an atomic consequent with existential variables,
you need an ontology language with inverse roles, otherwise
existentials can not fully encoded in the ontology.

Am I wrong?
cheers
--e.

Enrico Franconi                  - franconi@inf.unibz.it
Free University of Bozen-Bolzano - http://www.inf.unibz.it/~franconi/
Faculty of Computer Science      - Phone: (+39) 0471-016-120
I-39100 Bozen-Bolzano BZ, Italy  - Fax:   (+39) 0471-016-129
Received on Thursday, 4 November 2004 15:57:01 GMT

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