In the area of agent-based computing there are many proposals for specific system architectures, and a number of proposals for general approaches to building agents. As yet, however, there are comparatively few attempts to relate these together, and even fewer attempts to provide methodologies which relate designs to architectures and then to executable agents. This paper provides a first attempt to address this shortcoming. We propose a general method of specifying logic-based agents, which is based on the use of multi-context systems, and give examples of its use. The resulting specifications can be directly executed, and we discuss an implementation which makes this direct execution possible.

Abstract. Many techniques for coordinating agents require that the agents communicate, and many of the requisite communications need more than the exchange of a few terse illocutions. In other words they require some form of dialogue. This paper discusses one way to create such dialogues, the use of argumentation, and illustrates the use of this approach in the definition of dialogues about joint plans. 1.

As multi-agent systems proliferate and employ different and more sophisticated formal logics, it is increasingly likely that agents will be reasoning with different rules of inference. Hence, an agent seeking to convince another of some proposition may first have to convince the latter to use a rule of inference which it has not thus far adopted. We define a formalism to represent degrees of acceptability or validity of rules of inference, to enable autonomous agents to undertake dialogue concerning inference rules. Even when they disagree over the acceptability of a rule, two agents may still use the proposed formalism to reason collaboratively. 1

Abstract. In this paper we study the fragment of Dung’s argumentation theory in which the strict attack relation is acyclic. We show that every attack relation satisfying a particular property can be represented by a symmetric conflict relation and a transitive preference relation argumentation theory, in which ‘argument A attacks argument B ’ is defined as ‘argument A conflicts with argument B ’ and ‘argument A is at least as preferred as argument B’, where the conflict relation is symmetric and the preference relation is transitive. We show that this new preference-based argumentation theory characterizes the acyclic strict attack relation, in the sense that every attack relation defined as such a combination satisfies the property, and for every attack relation satisfying the property we can find a symmetric conflict relation and a transitive preference relation satisfying the equation. 1 Acyclic argumentation framework

In this paper we are interested in the role of preferences in argumentation theory. To promote a higher impact of preference reasoning in argumentation, we introduce a novel preference-based argumentation theory. Using non-monotonic preference reasoning we derive a Dung-style attack relation from a preference specification together with a defeat relation. In particular, our theory uses efficient algorithms computing acceptable arguments via a unique preference relation among arguments from a preference relation among sets of arguments.

Abstract. In this paper we study the acceptability of incompatible arguments within Dung’s abstract argumentation framework. As an example we introduce an instance of Dung’s framework where arguments are represented by propositional formulas and an argument attacks another one when the conjunction of their representations is inconsistent, which we characterize as a kind of symmetric attack. Since symmetric attack is known to have the drawback to collapse the various argumentation semantics, we consider also two variations. First, we consider propositional arguments distinguishing support and conclusion. Second, we introduce a preference ordering over the arguments and we define the attack relation in terms of a symmetric incompatibility relation and the preference relation. We show how to characterize preference-based argumentation using a kind of acyclic attack relation. 1

This paper presents a protocol for agents engaged in argumentation over access to information sources. Obtaining relevant information is essential for agents engaged in autonomous, goal-directed behavior, but access to such information is usually controlled by other autonomous agents having their own goals. Because these various goals may be in conflict with one another, rational interactions between the two agents may take the form of a dialog, in which requests for information are successively issued, considered, justified and criticized. Even when the agents involved in such discussions agree on all the arguments for and the arguments against granting access to some information source, they may still disagree on their preferences between these arguments. To represent such situations, we design a protocol for dialogs between two autonomous agents for seeking and granting authorization to access some information source. This protocol is based on an argumentation dialog where agents handle specific preferences and acceptability over arguments.