Preface of the special issue ‘Logic, argumentation and AI’ in JLC

in Journal of Logic and Computation (2021), 31(8), 1901-1902

Preface

in Journal of Logic and Computation (2017)

Prioritized Norms in Formal Argumentation

in Journal of Logic and Computation (2017), abs/1709.08034

To resolve conflicts among norms,various nonmonotonic formalisms can be used to perform prioritized normative reasoning. Meanwhile, formal argumentation provides a way to represent nonmonotonic logics. In ... [more ▼]

To resolve conflicts among norms,various nonmonotonic formalisms can be used to perform prioritized normative reasoning. Meanwhile, formal argumentation provides a way to represent nonmonotonic logics. In this paper, we propose a representation of prioritized normative reasoning by argumentation. Using hierarchical abstract normative systems, we define three kinds of prioritized normative reasoning approaches, called Greedy, Reduction, and Optimization. Then, after formulating an argumentation theory for a hierarchical abstract normative system, we show that for a totally ordered hierarchical abstract normative system, Greedy and Reduction can be represented in argumentation by applying the weakest link and the last link principles respectively, and Optimization can be represented by introducing additional defeats capturing implicit conflicts between arguments. [less ▲]

The handling of loops in argumentation networks

in Journal of Logic and Computation (2016), 26(4), 1065--1147

Logical foundations for bipolar and tripolar argumentation networks: preliminary results

in Journal of Logic and Computation (2016), 26(1), 247--292

Proof theory, semantics and algebra for normative systems

in Journal of logic and computation (2015)

This paper reports a correspondence between input/output logic and the theory of joining-system, an algebraic approach to normative system. The results have the form: every norm (a; x) is logically ... [more ▼]

This paper reports a correspondence between input/output logic and the theory of joining-system, an algebraic approach to normative system. The results have the form: every norm (a; x) is logically derivable from a set of norms G if and only if it is in the space of norms algebraically generated by G. We present three versions of correspondence: input/output logic and Boolean joining-system, intuitionistic input/output logic and Heyting joining-system, quasi input/output logic and quasi joining-system. The algebraic approach o ers a holistic perspective on normative systems. We use isomorphism and embedding of joining-system to discuss the similarity of normative systems. [less ▲]

An equational approach to the merging of argumentation networks

in Journal of Logic and Computation (2014), 24(6), 1253--1277

Attack-Defense Trees

in Journal of Logic and Computation (2012)

Attack-defense trees are a novel methodology for graphical security modeling and assessment. They extend the well known formalism of attack trees by allowing nodes that represent defensive measures to ... [more ▼]

Attack-defense trees are a novel methodology for graphical security modeling and assessment. They extend the well known formalism of attack trees by allowing nodes that represent defensive measures to appear at any level of the tree. This enlarges the modeling capabilities of attack trees and makes the new formalism suitable for representing interactions between an attacker and a defender. Our formalization supports different semantical approaches for which we provide usage scenarios. We also formalize how to quantitatively analyze attack and defense scenarios using attributes. [less ▲]

Reliable Methods of Judgement Aggregation

in Journal of Logic and Computation (2010), 20(2), 603617

The aggregation of consistent individual judgements on logically interconnected propositions into a collective judgement on the same propositions has recently drawn much attention. Seemingly reasonable ... [more ▼]

The aggregation of consistent individual judgements on logically interconnected propositions into a collective judgement on the same propositions has recently drawn much attention. Seemingly reasonable aggregation procedures, such as propositionwise majority voting, cannot ensure an equally consistent collective conclusion. The literature on judgement aggregation refers to such a problem as the discursive dilemma. In this article we assume that the decision which the group is trying to reach is factually right or wrong. Hence, we address the question of how good various approaches are at selecting the right conclusion. We focus on two approaches: distance-based procedures and a Bayesian analysis. They correspond to group-internal and group external decision making, respectively. We compare those methods in a probabilistic model whose assumptions are subsequently relaxed. Our findings have two general implications for judgement aggregation problems: first, in a voting procedure, reasons should carry higher weight than the conclusion, and second, considering members of an advisory board to be highly competent is a better strategy than discounting their advice. [less ▲]

Cut-Based Abduction

in Journal of Logic and Computation (2008), 16(6), 537560

In this paper we explore a generalization of traditional abduction which can simultaneously perform two different tasks: (i) given an unprovable sequent G, find a sentence H such that, H G is provable ... [more ▼]

In this paper we explore a generalization of traditional abduction which can simultaneously perform two different tasks: (i) given an unprovable sequent G, find a sentence H such that, H G is provable (hypothesis generation); (ii) given a provable sequent G, find a sentence H such that H and the proof of , H G is simpler than the proof of G (lemma generation). We argue that the two tasks should not be distinguished,and present a general procedure for indingsuitable hypotheses or lemmas. When the original sequent is provable, the abduced formula can be seen asa cut formula with respect to Gentzen's sequent calculus, so the abduction method is cut-based. Our method is based on the tableau-like system KE and we argue for its advantages over existing abduction methods based on traditional Smullyan-styleTableaux. [less ▲]