Preface to the Special Issue on Advances in Argumentation in Artificial Intelligence

Now at the forefront of automated reasoning, argumentation has become a key research topic within Artificial Intelligence. It involves the investigation of those activities for the production and exchange of arguments, where arguments are attempts to persuade someone of something by giving reasons for accepting a particular conclusion or claim as evident. The study of argumentation has been the focus of attention of philosophers and scholars, from Aristotle and classical rhetoric to the present day. The computational study of arguments has emerged as a field of research in AI in the last two decades, mainly fuelled by the interest from scholars in logics, non-monotonic and epistemic reasoning, and in related disciplines such as Law, Sociology and Computational Linguistics. This special issue collects a selection of five papers from the 2nd Workshop on Advances In Argumentation In Artificial Intelligence, co-located with AI*IA 2018, the 17th International Conference of the Italian Association for Artificial Intelligence held in Trento in November 2018. The workshop was organized as part of the activities of the Argumentation in Artificial Intelligence Working Group. The Argumentation Group is a working group of the Associazione Italiana per l’Intelligenza Artificiale (AI*IA) whose general goal is to promote Italian scientific activities in the field of Argumentation in Artificial Intelligence, and foster collaborations between research groups. The selected papers discuss theoretical foundations in argumentation as well as challenges and real-world problems for which argumentation may represent a viable AI-paradigm. Each submission underwent a single-blind peer-review process and the five accepted articles were reviewed by at least two independent expert reviewers. Much work in computational models of argument is centered on Dung’ seminal 1995 paper “On the acceptability of arguments and its fundamental role in nonmonotonic reasoning, logic programming and n-person games.”. On the one hand, this is reflected by the papers presented in this special issue, with four out of five papers describing works directly linked to Dung’s abstract framework or to its extensions. On the other hand, the papers also testify the variety and richness of the current state-of-the-art of argumentation studies, which extends and goes far beyond Dung’s work, proposing research combining natural language processing and probabilistic reasoning with abstract argumentation The papers by Flesca, Dondio and Longo, and Taticchi and Bistarelli are theoretical works in the area of computational argumentation. The paper by Flesca examines the problem of efficiently computing the probability of the extensions of bipolar probabilistic argumentation frameworks, proposing a set of more efficient and empirically-tested algorithms. The paper by Dondio and Longo introduces a novel abstract argumentation semantics. Inspired by the ambiguity blocking semantics of defeasible logic, the authors propose a semantics where the undecided label assigned to some arguments could be blocked instead of being propagated to attacked arguments. The paper by Taticchi and Bistarelli proposes a cooperative-game approach to share acceptability and rank arguments of an argumentation framework. The paper by Gobbo et al. proposes a new method for annotating arguments expressed in natural language, called adpositional argumentation. By doing so, they provide the guidelines for designing a gold standard corpus that could benefit studies in argumentation mining and arguments definition. The paper by Pazienza et al. proposes an interesting application of abstract argumentation to financial predictions. The authors design a framework combining natural language processing along with abstract argumentation techniques to automatically extract relevant arguments from Earning Conference Call transcripts, weight such arguments and produce a final advice aimed to anticipate and predict analysts’ recommendations. Finally, the Editors are like to acknowledge the work of the members of the Programme Committee whose invaluable expertise and efforts have led to the selection of the papers included in this special issue. Last but not least, the editors would like to thank all the authors that have contributed to this special issue

Constrained Cost-Coupled Stochastic Games with Independent State Processes

We consider a non-cooperative constrained stochastic games with N players with the following special structure. With each player there is an associated controlled Markov chain. The transition probabilities of the i-th Markov chain depend only on the state and actions of controller i. The information structure that we consider is such that each player knows the state of its own MDP and its own actions. It does not know the states of, and the actions taken by other players. Finally, each player wishes to minimize a time-average cost function, and has constraints over other time-avrage cost functions. Both the cost that is minimized as well as those defining the constraints depend on the state and actions of all players. We study in this paper the existence of a Nash equilirium. Examples in power control in wireless communications are given.Comment: 7 pages, submitted in september 2006 to Operations Research Letter

Hypergraph conditions for the solvability of the ergodic equation for zero-sum games

The ergodic equation is a basic tool in the study of mean-payoff stochastic games. Its solvability entails that the mean payoff is independent of the initial state. Moreover, optimal stationary strategies are readily obtained from its solution. In this paper, we give a general sufficient condition for the solvability of the ergodic equation, for a game with finite state space but arbitrary action spaces. This condition involves a pair of directed hypergraphs depending only on the ``growth at infinity'' of the Shapley operator of the game. This refines a recent result of the authors which only applied to games with bounded payments, as well as earlier nonlinear fixed point results for order preserving maps, involving graph conditions.Comment: 6 pages, 1 figure, to appear in Proc. 54th IEEE Conference on Decision and Control (CDC 2015

Affect and believability in game characters:a review of the use of affective computing in games

Virtual agents are important in many digital environments. Designing a character that highly engages users in terms of interaction is an intricate task constrained by many requirements. One aspect that has gained more attention recently is the effective dimension of the agent. Several studies have addressed the possibility of developing an affect-aware system for a better user experience. Particularly in games, including emotional and social features in NPCs adds depth to the characters, enriches interaction possibilities, and combined with the basic level of competence, creates a more appealing game. Design requirements for emotionally intelligent NPCs differ from general autonomous agents with the main goal being a stronger player-agent relationship as opposed to problem solving and goal assessment. Nevertheless, deploying an affective module into NPCs adds to the complexity of the architecture and constraints. In addition, using such composite NPC in games seems beyond current technology, despite some brave attempts. However, a MARPO-type modular architecture would seem a useful starting point for adding emotions

Computational Aspects of Extending the Shapley Value to Coalitional Games with Externalities

Until recently, computational aspects of the Shapley value were only studied under the assumption that there are no externalities from coalition formation, i.e., that the value of any coalition is independent of other coalitions in the system. However, externalities play a key role in many real-life situations and have been extensively studied in the game-theoretic and economic literature. In this paper, we consider the issue of computing extensions of the Shapley value to coalitional games with externalities proposed by Myerson [21], Pham Do and Norde [23], and McQuillin [17]. To facilitate efficient computation of these extensions, we propose a new representation for coalitional games with externalities, which is based on weighted logical expressions. We demonstrate that this representation is fully expressive and, sometimes, exponentially more concise than the conventional partition function game model. Furthermore, it allows us to compute the aforementioned extensions of the Shapley value in time linear in the size of the input