Theory of Semi-Instantiation in Abstract Argumentation

We study instantiated abstract argumentation frames of the form $(S,R,I)$, where $(S,R)$ is an abstract argumentation frame and where the arguments $x$ of $S$ are instantiated by $I(x)$ as well formed formulas of a well known logic, for example as Boolean formulas or as predicate logic formulas or as modal logic formulas. We use the method of conceptual analysis to derive the properties of our proposed system. We seek to define the notion of complete extensions for such systems and provide algorithms for finding such extensions. We further develop a theory of instantiation in the abstract, using the framework of Boolean attack formations and of conjunctive and disjunctive attacks. We discuss applications and compare critically with the existing related literature

Automata for infinite argumentation structures

The theory of abstract argumentation frameworks (afs) has, in the main, focused on finite structures, though there are many significant contexts where argumentation can be regarded as a process involving infinite objects. To address this limitation, in this paper we propose a novel approach for describing infinite afs using tools from formal language theory. In particular, the possibly infinite set of arguments is specified through the language recognized by a deterministic finite automaton while a suitable formalism, called attack expression, is introduced to describe the relation of attack between arguments. The proposed approach is shown to satisfy some desirable properties which cannot be achieved through other “naive” uses of formal languages. In particular, the approach is shown to be expressive enough to capture (besides any arbitrary finite structure) a large variety of infinite afs including two major examples from previous literature and two sample cases from the domains of multi-agent negotiation and ambient intelligence. On the computational side, we show that several decision and construction problems which are known to be polynomial time solvable in finite afs are decidable in the context of the proposed formalism and we provide the relevant algorithms. Moreover we obtain additional results concerning the case of finitaryafs

Etude du changement en argumentation : de la théorie à la pratique

L'argumentation, au sens de l'intelligence artificielle, est un formalisme permettant de raisonner à partir d'informations incomplètes et/ou contradictoires ainsi que de modéliser un échange d'arguments entre plusieurs agents. Un système d'argumentation consiste généralement en un ensemble d'arguments interagissant les uns avec les autres, et duquel il est possible d'extraire un ou plusieurs points de vue cohérents. Dans cette thèse, nous nous plaçons dans le cadre de l'argumentation abstraite dans lequel les arguments sont manipulés en tant qu'entités abstraites dont le sens nous est inconnu et dans lequel les interactions représentent des conflits. Ceci nous permet de nous concentrer sur le point particulier de la dynamique dans les systèmes d'argumentation abstraits, c'est-à-dire les changements pouvant impacter ces systèmes, notamment dans le cadre d'un dialogue. Nous commençons par justifier l'intérêt d'un tel cadre formel puis nous nous intéressons au comment et au pourquoi du changement en argumentation abstraite. Le comment est approché en établissant une liste des modifications que peut subir un système d'argumentation et en étudiant sous quelles conditions elles peuvent survenir. Le pourquoi est abordé par l'introduction de la notion de but motivant un changement et le choix du meilleur changement à faire pour satisfaire un but en prenant en considération des contraintes portant sur l'agent à convaincre. Enfin, nous concrétisons notre étude en proposant un outil logiciel implémentant les notions introduites et nous étudions ses performances.Argumentation, in the field of artificial intelligence, is a formalism allowing to reason with incomplete and/or contradictory information as well as to model an exchange of arguments between several agents. An argumentation system usually consists of a set of arguments interacting with each other, and from which it is possible to extract one or several consistent points of view. In this thesis, we are mainly concerned with the abstract argumentation in which arguments are handled as abstract entities whose meaning is unknown and in which the interactions represent conflicts. This allows us to focus on the particular point of the dynamics in abstract argumentation systems, that is to say the changes that could impact these systems, particularly in the context of a dialogue. We start with justifying the interest of such a formal framework, then we study the how and the why of change in abstract argumentation. The how is tackled by establishing a list of changes that an argumentation system can undergo and by studying the conditions under which they may occur. The why is addressed by introducing the notion of goal motivating a change and by choosing the best change to make in order to satisfy a goal, taking into account constraints on the agent to convince. Finally, we make our study concrete by proposing a tool that implements the concepts introduced and we study its performance

Dialectical Proofs for Constrained Argumentation

Session: Dialectical issues in argumentation, Chair: Guido BoellaInternational audienceConstrained argumentation frameworks (CAF) generalize Dung's frameworks by allowing additional constraints on arguments to be taken into account in the definition of acceptability of arguments. These constraints are expressed by means of a logical formula which is added to Dung's framework. The resulting system captures several other extensions of Dung's original system. To determine if a set of arguments is credulously inferred from a CAF, the notion of dialectical proof (alternating pros and cons arguments) is extended for Dung's frameworks in order to respect the additional constraint. The new constrained dialectical proofs are computed by using Answer Set Programming.</p