Vol. 15 No. 5, © The Author, 2005. Published by Oxford University Press. All rights reserved.
Original Articles |
Pivotal and Pivotal-discriminative Consequence Relations
Laboratoire d'Informatique Fondamentale de Marseille (LIF), CNRS UMR 6166, CMI 39, rue Joliot-Curie, F-13453 Marseille Cedex 13, France. Email: jbennaim{at}lif.univ-mrs.fr
A pivotal consequence relation is defined to hold between a set of formulas
and formula
iff every non-negligible model for
is a model for
. Unlike preferential consequence relations, the set of all non-negligible (or preferred) valuations is fixed and thus does not depend on the premisses under consideration. The first purpose of the present paper is to investigate pivotal consequence relations. We provide characterizations of several families in the classical framework, but also in certain three/four-valued frameworks, well-known as the paraconsistent logics J3 and 


. We show also that there is no normal characterization of the family of all pivotal consequence relations, in the infinite classical framework. And we show a link with X-logics. Our second purpose is to investigate a qualified version of pivotal consequence, which we call pivotal-discriminative consequence. This is defined to hold between a set of formulas
and formula
iff
but
¬
, where
is the plain relation. We provide characterizations of several families of such relations for the classical, three, and four-valued frameworks.
Keywords: Pivotal consequence relations, paraconsistent logics, many-valued lgoics
Received 18 October 2004.