Publications on Argumentation

Jenny Eriksson Lundström, Guido Governatori, Subhasis Thakur, and Vineet Padmanabhan.
An asymmetric protocol for argumentation games in defeasible logic. In Aditya Ghose and Guido Governatori, editors, 10 Pacific Rim International Workshop on Multi-Agents, LNAI 5044. Springer, 2008 Copyright © 2008 Springer.
Abstract: Agent interactions where the agents hold conflicting goals could be modelled as adversarial argumentation games. In many real-life situations (e.g., criminal litigation, consumer legislation), due to ethical, moral or other principles governing interaction, the burden of proof, i.e., which party is to lose if the evidence is balanced, is a priori fixed to one of the parties. Analogously, when resolving disputes in a heterogeneous agent-system the unequal importance of different agents for carrying out the overall system goal need to be accounted for. In this paper we present an asymmetric protocol for an adversarial argumentation game in Defeasible Logic, suggesting Defeasible Logic as a general representation formalism for argumentation games modelling agent interactions.
 
Guido Governatori.
On the relationship between Carneades and defeasible logic. In Tom van Engers, editor, Proceedings of the 13th International Conference on Artificial Intelligence and Law (ICAIL 2011). ACM Press, 2011. Copyrigth © 2011 ACM Press.
Abstract: We study the formal relationships between the inferential aspects of Carneades (a general argumentation framework) and Defeasible Logic. The outcome of the investigation is that the current proof standards proposed in the Carneades framework correspond to some variants of Defeasible Logic.
 
Guido Governatori, Marlon Dumas, Arthur H.M. ter Hofstede, and Phillipa Oaks.
A formal approach to protocols and strategies for (legal) negotiation. In Henry Prakken, editor, Procedings of the 8th International Conference on Artificial Intelligence and Law, pages 168-177. IAAIL, ACM Press, 2001, Copyright © 2001 ACM.
Abstract: We propose a formal and executable framework for expressing protocols and strategies for automated (legal) negotiation. In this framework a party involved in a negotiation is represented through a software agent composed of four modules: (i) a communication module which manages the interaction with the other agents; (ii) a control module; (iii) a reasoning module specified as a defeasible theory; and (iv) a knowledge base which bridges the control and the reasoning modules, while keeping track of past decisions and interactions. The choice of defeasible logic is justified against a set of desirable criteria for negotiation automation languages. Moreover, the suitability of the framework is illustrated through two case studies.
 
Guido Governatori and Michael J. Maher.
An argumentation-theoretic characterization of defeasible logic. In Werner Horn, editor, ECAI 2000. Proceedings of the 14th European Conference on Artificial Intelligence, pages 469-474, Amsterdam, 2000. IOS Press.
Abstract: Defeasible logic is an efficient non-monotonic logic that is defined only proof-theoretically. It has potential application in some legal domains. We present here an argumentation semantics for defeasible logic that will be useful in these applications. Our development differs at several points from existing argumentation frameworks since there are several features of defeasible logic that have not been addressed in the literature.
 
Guido Governatori, Michael J. Maher, Grigoris Antoniou, and David Billington.
Argumentation semantics for defeasible logics. In Riichiro Mizoguchi and John Slaney, editors, PRICAI 2000: Topics in Artificial Intelligence, volume 1886 of LNAI, pages 27-37, Berlin, 2000. Springer-Verlag, Copyright © 2000 Springer-Verlag.
Abstract: Defeasible logic is an efficient non-monotonic logic that is defined only proof-theoretically. It has potential application in some legal domains. We present here argumentation semantics for variants of defeasible logic that will be useful in these applications.
 
Guido Governatori, Michael J. Maher, David Billington, and Grigoris Antoniou.
Argumentation semantics for defeasible logics. Journal of Logic and Computation, 14, no. 5, pp. 675-702, 2004. Copyright © 2004 Oxford University Press.
Abstract:Defeasible reasoning is a simple but efficient rule-based approach to nonmonotonic reasoning. It has powerful implementations and shows promise to be applied in the areas of legal reasoning and the modeling of business rules. This paper establishes significant links between defeasible reasoning and argumentation. In particular, Dung-like argumentation semantics is provided for two key defeasible logics, of which one is ambiguity propagating and the other ambiguity blocking. There are several reasons for the significance of this work: (a) establishing links between formal systems leads to a better understanding and cross-fertilization, in particular our work sheds light on the argumentation-theoretic features of defeasible logic; (b) we provide the first ambiguity blocking Dung-like argumentation system; (c) defeasible reasoning may provide an efficient implementation platform for systems of argumentation; and (d) argumentation-based semantics support a deeper understanding of defeasible reasoning, especially in the context of the intended applications.
 
Guido Governatori and Giovanni Sartor.
Burdens of proof in monological argumentation. In Radboud Winkels, editor, Legal Knowledge and Information Systems JURIX 2010: The Twenty-Third Annual Conference, Frontiers in Artificial Intelligence and Applications, Amsterdam, 2010. IOS Press.
Abstract: We shall argue that burdens of proof are relevant also to monological reasoning, i.e., for deriving the conclusions of a knowledge-base allowing for conflicting arguments. Reasoning with burdens of proof can provide a useful extension of current argument-based non-monotonic logics, at least a different perspective on them. Firstly we shall provide an objective characterisation of burdens of proof, assuming that burdens concerns rule antecedents (literals in the body of rules), rather than agents. Secondly, we shall analyse the conditions for a burden to be satisfied, by considering credulous or skeptical derivability of the concerned antecedent or of its complement. Finally, we shall develop a method for developing inferences out of a knowledge base merging rules and proof burdens in the framework of defeasible logic.
 
Duy Hoang Pham, Subhasis Thakur, and Guido Governatori.
Settling on the group's goals: An n-person argumentation game approach. In The Duy Bui, Tuong Vinh Ho, and Quang-Thuy Ha, editors, 11th Pacific Rim International Conference on Multi-Agents (PRIMA 2008), Lecture Notes in Computer Science 5357, pages 328-339. Springer, 2008, Copyright © 2008 Springer.
Abstract: Argumentation games have been proved to be a robust and flexible tool to resolve conflicts among agents. An agent can propose its explanation and its goal known as a claim, which can be refuted by other agents. The situation is more complicated when there are more than two agents playing the game. We propose a weighting mechanism for competing premises to tackle with conflicts from multiple agents in an n-person game. An agent can defend its proposal by giving a counter-argument to change the ``opinion'' of the majority of opposing agents. During the game, an agent can exploit the knowledge that other agents expose in order to promote and defend its main claim.
 
Duy Hoang Pham, Subhasis Thakur, and Guido Governatori.
Defeasible logic to model n-person argumentation game. In Maurice Pagnuco and Michael Thielscher, editors, Twelfth International Workshop on Non-Monotonic Reasoning, pages 215-222, 13--15 September 2008.
Abstract: In multi-agent systems, an individual agent can pursue its own goals, which may conflict with those hold by other agents. To settle on a common goal for the group of agents, the argumentation/dialogue game provides a robust and flexible tool where an agent can send its explanation for its goal in order to convince other agents. In the setting that the number of agents is greater than two and they are equally trustful, it is not clear how to extend existing argumentation/dialogue frameworks to tackle conflicts from many agents. We propose to use the defeasible logic to model the n-person argumentation game and to use the majority rule as an additional preference mechanism to tackle conflicts between arguments from individual agents.
 
Duy Hoang Pham, Guido Governatori, and Subhasis Thakur.
Extended defeasible reasoning for common goals in n-person argumentation games. Journal of Universal Computer Science, 15 no. 13 pp. 2653--2675, 2009.
Abstract: Argumentation games have been proved to be a robust and flexible tool to resolve conflicts among agents. An agent can propose its explanation and its goal known as a claim, which can be refuted by other agents. The situation is more complicated when there are more than two agents playing the game. We propose a weighting mechanism for competing premises to tackle with conflicts from multiple agents in an n-person game. An agent can defend its proposal by giving a counter-argument to change the "opinion" of the majority of opposing agents. Furthermore, using the extended defeasible reasoning an agent can exploit the knowledge that other agents expose in order to promote and defend its main claim.
 
Régis Riveret, Guido Governatori, and Antonino Rotolo.
Argumentation semantics for temporal defeasible logic. In Pavlos Peppas, Anna Perini, and Loris Penserini, editors, Third European Starting AI Researcher Symposium (STAIRS 2006), pp. 267-268. Riva del Garda, 28-29 August 2006. IOS Press, Amsterdam, 2006.
Abstract: We present an extension of the argumentation semantics for defeasible logic to cover the temporalisation of defeasible logic with permanent and immanent temporal literals.
 
Bram Roth, Régis Riveret, Antonino Rotolo and Guido Governatori.
Strategic Argumentation: A Game Theoretical Investigation. In Radboud Winkels, editor, Proceedings of 11th International Conference on Artificial Intelligence and Law, pp. 81-90. ACM Press, New York, 2007. Copyright © 2007 ACM
Abstract: Argumentation is modelled as a game where the payoffs are measured in terms of the probability that the claimed conclusion is, or is not, defeasibly provable, given a history of arguments that have actually been exchanged, and given the probability of the factual premises. The probability of a conclusion is calculated using a standard variant of Defeasible Logic, in combination with standard probability calculus. It is a new element of the present approach that the exchange of arguments is analysed with game theoretical tools, yielding a prescriptive and to some extent even predictive account of the actual course of play. A brief comparison with existing argument-based dialogue approaches confirms that such a prescriptive account of the actual argumentation has been almost lacking in the approaches proposed so far.
 
Insu Song and Guido Governatori.
A compact argumentation system for agent system specification. In Pavlos Peppas, Anna Perini, and Loris Penserini, editors, Third European Starting AI Researcher Symposium (STAIRS 2006), pp. 26-37. Riva del Garda, 28-29 August 2006. IOS Press, Amsterdam, 2006.
Abstract: We present a non-monotonic logic tailored for specifying compact autonomous agent systems. The language is a consistent instantiation of a logic based argumentation system extended with Brooks' subsumption concept and varying degree of belief. Particularly, we present a practical implementation of the language by developing a meta-encoding method that translates logical specifications into compact general logic programs. The language allows n-ary predicate literals with the usual first-order term definitions. We show that the space complexity of the resulting general logic program is linear to the size of the original theory.
 
Insu Song, Guido Governatori, and Joachim Diederich.
Layered argumentation for fuzzy automation controllers. In IEEE Conference on Cybernetics and Intelligent Systems (CIS), , pages 189-194. IEEE Press, June 28-30 2010, Copyrigth © 2010 IEEE.
Abstract: We develop a layered argumentation system (LAS) for efficient implementation of Fuzzy automation controllers. LAS extends a logic based proposal of argumentation with subsumption concept and varying degree of confidences in beliefs. We show that this argumentation system can be used to model Fuzzy automation controllers. The argumentation system is based on a nonmonotonic logic, the computational complexity of which is known to be linear to the size of the knowledge base. LAS theories can also be mapped into RTL-VHDL (Register Transfer Level-VLSI Hardware Description Language) or RTL Verilog for very efficient hardware implementation of Fuzzy automation controllers.
 
Subhasis Thakur, Guido Governatori, Vineet Padmanabhan, and Jenny Eriksson Lundström.
Dialogue games in defeasible logic. In Mehmet A. Orgun and John Thornton, editors, 20th Australian Joint Conference on Artificial Intelligence, AI 2007, LNAI 4830, pages 497-506. Springer, 2007. Copyright © 2007 Springer.
Abstract: In this paper we show how to capture dialogue games in Defeasible Logic. We argue that Defeasible Logic is a natural candidate and general representation formalism to capture dialogue games even with requirements more complex than existing formalisms for this kind of games. We parse the dialogue into defeasible rules with time of the dialogue as time of the rule. As the dialogue evolves we allow an agent to upgrade the strength of unchallenged rules. The proof procedures of (Antoniou, Billington, Governatori, Maher 2001) are used to determine the winner of a dialogue game.