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This article deals with many-valued modal logics, based only on the necessity operator, over a residuated lattice. We focus on three basic classes, according to the accessibility relation, of Kripke frames: the full class of frames evaluated in the residuated lattice (and so defining the minimum modal logic), the ones evaluated in the idempotent elements(More)
This paper introduces a new class of fuzzy closure operators called implicative closure operators, which generalize some notions of fuzzy closure operators already introduced by different authors. We show that implicative closure operators capture some usual consequence relations used in Approximate Reasoning, like ChakrabortyÕs graded consequence relation,(More)
One of the goals of a variety of approximate reasoning models is to cope with inference patterns more flexible than those of classical reasoning. Among them, similarity based reasoning aims at modeling notions of resemblance or proximity among propositions and consequence relations which make sense in such a setting. One way of proceeding is to. equip the(More)
We prove strong completeness of the-version and the 3-version of a Gödel modal logic based on Kripke models where propositions at each world and the accessibility relation are both in…nitely valued in the standard Gödel algebra [0,1]. Some asymmetries are revealed: validity in the …rst logic is reducible to the class of frames having two-valued(More)
We consider the Gödel bi-modal logic determined by fuzzy Kripke models where both the propositions and the accessibility relation are infinitely valued over the standard Gödel algebra [0,1] and prove strong completeness of Fischer Servi intuitionistic modal logic IK plus the pre-linearity axiom with respect to this semantics. We axiomatize also the bi-modal(More)
One of the ways to model contraction functions for belief sets is epistemic entrenchment. The first step was provided by Gärdenfors in [5], who defined epistemic entrenchment and a contraction function in terms of it and related the latter with the AGM contraction function. Later Hans Rott in [16] presented an entrenchment based contraction function that(More)
A new semantics with the finite model property is provided and used to establish decidability for Gödel modal logics based on (crisp or fuzzy) Kripke frames combined locally with Gödel logic. A similar methodology is also used to establish decidability, and indeed co-NP-completeness for a Gödel S5 logic that coincides with the one-variable fragment of(More)
SYNOPSIS Assessment of surgical risk in patients undergoing pulmonary resection is a fundamental goal for thoracic surgeons. Usually used risk scores do not predict the individual outcome. Data Mining (DM) and Artificial Neural Networks (ANN) are artificial intelligence mathematical models that have been used for estimation of several prognostic situations.(More)
Semi-contraction is a withdrawal operation defined by Fermé in " On the logic of theory change: Contraction without recovery. " In this paper we propose: (1) an axiomatic characterization of semi-contraction; (2) an alternative construction for semi-contraction based on semi-saturatable sets, inspired by Levi's saturatable sets; (3) a special kind of(More)