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This paper is a contribution to the study of equality-free logic, that is, first-order logic without equality. We mainly devote ourselves to the study of algebraic characterizations of its relation of elementary equivalence by providing some Keisler-Shelah type ultrapower theorems and an Ehrenfeucht-Fra¨ıssé type theorem. We also give characterizations of… (More)
In this article I prove preservation theorems for the positive and for the universal-existential fragment of equality-free logic. I give a systematic presentation of the method of diagrams for first-order languages without equality.
In this paper we present completeness results of several fuzzy logics trying to capture different notions of necessity (in the sense of Possibility theory) for Gödel logic formulas. In a first attempt, based on different characterizations of necessity measures on fuzzy sets, a group of logics, with Kripke style semantics, are built over a restricted… (More)
Our work is a contribution to the model-theoretic study of equality-free fuzzy predicate logics. We give a characterization of elementary equivalence in fuzzy predicate logics using elementary extensions and introduce an strengthening of this notion, the so-called strong elementary equivalence. Using the method of diagrams developed in  and elementary… (More)
In this paper we present several fuzzy logics trying to capture different notions of necessity (in the sense of Possibility theory) for Gödel logic formulas. Based on different characterizations of necessity measures on fuzzy sets, a group of logics with Kripke style semantics are built over a restricted language, namely a two level language composed of… (More)
This paper is a contribution to the formalisation of Thagard's coherence theory. The term coherence is defined as the quality or the state of cohering, especially a logical, orderly, and aesthetically consistent relationship of parts. A coherent set is interdependent such that every element in it contributes to the coherence. We take Thagard's proposal of a… (More)
This contribution proposes a model for argumentation-based multi-agent planning, with a focus on cooperative scenarios. It consists in a multi-agent extension of DeLP-POP, partial order planning on top of argumentation-based defeasible logic programming. In DeLP-POP, actions and arguments (combinations of rules and facts) may be used to enforce some goal,… (More)