Duality on combinatorial structures. An application to cooperative games

This paper deals with cooperative games in which only certain coalitions are feasible. Several combinatorial structures have been used to represent feasible coalition systems for different situations: poset of ideals, connected sets in graphs, convex geometries or antimatroids. Augmenting systems are combinatorial structures generalizing antimatroids defined in the framework of the game theory. In this paper, we introduced decreasing systems as dual structures of the augmenting systems. We connect the classical concept of dual game with the duality between these structures. The Shapley and the Banzhaf values are studied and compared for augmenting and decreasing systems.     

Estimating a Game Theoretic Model

Applied game theory generally shows possible game situations, discussingtheir implications. This paper derives an estimation procedure fornon-cooperative games, using cross-section data. During thetransformation of the data an attempt is made to pick extreme points, tofind the outer borders for the actual game. The estimation procedure isan algorithm that switches between several software packages. In anapplication a motivated choice can be made for the transformationfunctions such that the estimated game comes closest to the actual gameof the empirical problem under study. To demonstrate the estimationprocedure, a situation is studied in which a villager voluntarilychooses a level of participation in forest management.     

基于TU动态模糊联盟合作博弈的核心及谈判集

利用模糊数学相关理论,对具有可转移效用的模糊合作博弈进行了研究,分析了TU模糊合作博弈的核心,并在此基础上对谈判集理论进行了研究,分析了谈判集与核心之间的关系。对于全联盟可能存在核心空集的情况,L-Z谈判集很好地解决了TU联盟合作博弈的收敛集问题。最后利用实例对该谈判集的有效性和可行性进行了说明。     

Interactive story authoring: A viable form of creative expression for the classroom

The unprecedented growth in numbers of children playing computer games has stimulated discussion and research regarding what, if any, educational value these games have for teaching and learning. The research on this topic has primarily focused on children as players of computer games rather than builders/constructors of computer games. Recently, several game companies, such as BioWare Corp. and Bethesda Softworks, have released game story creation tools to the public, along with their games. However, a major obstacle to using these commercial tools is the level of programming experience required to create interactive game stories. In this paper, we demonstrate that a commercial game story construction tool, BioWare Corp.’s Aurora Toolset, can be augmented by our new tool, ScriptEase, to enable students in two grade ten English classes to successfully construct interactive game stories. We present evidence that describes the relationship between interactive story authoring and traditional story authoring, along with a series of factors that can potentially affect success at these activities: gender, creativity, intellectual ability, previous experiences with programming, time playing computer games, and time spent online. Results indicate that students can successfully construct sophisticated interactive stories with very little training. The results also show no gender differences in the quality of these interactive stories, regardless of programming experience or the amount of time per week playing computer games or participating in general online activities, although a subset of female students did show a slightly higher level of performance on interactive story authoring. In the educational context of this study, we show that ScriptEase provides an easy-to-use tool for interactive story authoring in a constructionist learning environment.     

基于Flash图形引擎的RTS游戏

RTS这类游戏世界结构复杂、表现难度大、性能要求高。为了降低开发难度、提高开发效率，该文采用Flash作为图形引擎，在此基础上通过OOP编程技术和OOD动画设计的结合，进行软件的设计和研究开发。基于Flash的游戏实现策略，构建了一个RTS游戏原型。研究表明，Flash作为图形引擎应用于大型游戏开发是可行的。     

Serious games for higher education: a framework for reducing design complexity

Abstract Serious games open up many new opportunities for complex skills learning in higher education. The inherent complexity of such games, though, requires large efforts for their development. This paper presents a framework for serious game design, which aims to reduce the design complexity at conceptual, technical and practical levels. The approach focuses on a relevant subset of serious games labelled as scenario‐based games. At the conceptual level, it identifies the basic elements that make up the static game configuration; it also describes the game dynamics, i.e. the state changes of the various game components in the course of time. At the technical level, it presents a basic system architecture, which comprises various building tools. Various building tools will be explained and illustrated with technical implementations that are part of the Emergo toolkit for scenario‐based game development. At the practical level, a set of design principles are presented for controlling and reducing game design complexity. The principles cover the topics of game structure, feedback and game representation, respectively. Practical application of the framework and the associated toolkit is briefly reported and evaluated.     

The bounded core for games with restricted cooperation

A game with restricted (incomplete) cooperation is a triple (N, v, Ω), where N represents a finite set of players, Ω ? 2^N is a set of feasible coalitions such that N ∈ Ω, and v: Ω → R denotes a characteristic function. Unlike the classical TU games, the core of a game with restricted cooperation can be unbounded. Recently Grabisch and Sudhölter [9] proposed a new solution concept—the bounded core—that associates a game (N, v,Ω) with the union of all bounded faces of the core. The bounded core can be empty even if the core is nonempty. This paper gives two axiomatizations of the bounded core. The first axiomatization characterizes the bounded core for the class G^r of all games with restricted cooperation, whereas the second one for the subclass G_bc^r ? G^r of the games with nonempty bounded cores.     

Algorithms for Finding Repeated Game Equilibria

This paper describes computational techniques for finding all equilibria in infinitely repeated games with discounting and perfect monitoring. It illustrates these techniques with a three player Cournot game. This is the first infinitely repeated three player game ever solved. The paper also presents the solution for the set of equilibria in a two country tariff war. In both games the set of equilibria is large even when the players are not patient.     

Multi-agent discrete-time graphical games and reinforcement learning solutions

This paper introduces a new class of multi-agent discrete-time dynamic games, known in the literature as dynamic graphical games. For that reason a local performance index is defined for each agent that depends only on the local information available to each agent. Nash equilibrium policies and best-response policies are given in terms of the solutions to the discrete-time coupled Hamilton–Jacobi equations. Since in these games the interactions between the agents are prescribed by a communication graph structure we have to introduce a new notion of Nash equilibrium. It is proved that this notion holds if all agents are in Nash equilibrium and the graph is strongly connected. A novel reinforcement learning value iteration algorithm is given to solve the dynamic graphical games in an online manner along with its proof of convergence. The policies of the agents form a Nash equilibrium when all the agents in the neighborhood update their policies, and a best response outcome when the agents in the neighborhood are kept constant. The paper brings together discrete Hamiltonian mechanics, distributed multi-agent control, optimal control theory, and game theory to formulate and solve these multi-agent dynamic graphical games. A simulation example shows the effectiveness of the proposed approach in a leader-synchronization case along with optimality guarantees.     

Children’s choices and strategies in video games

It is important to develop an understanding of children’s engagement and choices in learning experiences outside of school as this has implications for their development and orientations to other learning environments. This mixed-methods study examines relationships between the genres of video games children choose to play and the learning strategies they employ to improve at these games. It also explores students’ motivations for playing the games they choose to play. One hundred eighteen fourth- and fifth-grade students participated in this study. Qualitative analyses of student responses resulted in a model for classifying motivation for game choices. Children primarily cite reasons that can be classified as psychological or cognitive reasons for choosing to play certain video games, and are motivated by the challenge and thinking required in the games. Analyses using Chi-square tests of association demonstrated significant relationships between video game genre and learning strategy used for two of the six learning strategies (p < .05). Children playing action games are more likely to use repetition to learn the game and children playing adventure games are more likely to use their imaginations to take on the role of the character in the game and think the way the character would to make decisions in the game. There were also several gender differences in learning preferences.     

Migration from social casino games to gambling: Motivations and characteristics of gamers who gamble

The increasing convergence of the gambling and gaming industries has raised questions about the extent to which social casino game play may influence gambling. This study aimed to examine the relationship between social casino gaming and gambling through an online survey of 521 adults who played social casino games in the previous 12 months. Most social casino game users (71.2%) reported that these games had no impact on how much they gambled. However, 9.6% reported that their gambling overall had increased and 19.4% reported that they had gambled for money as a direct result of these games. Gambling as a direct result of social casino games was more common among males, younger users, those with higher levels of problem gambling severity and more involved social casino game users in terms of game play frequency and in-game payments. The most commonly reported reason for gambling as a result of playing social casino games was to win real money. As social casino games increased gambling for some users, this suggests that simulated gambling may influence actual gambling expenditure particularly amongst those already vulnerable to or affected by gambling problems.     

Bargaining property of nucleolus and τ-value in a class of TU-games

First, we introduce pairwise-bargained consistency with a reference point, and use as reference points the maxmin and the minmax value within pure strategies of a certain constant-sum bimatrix game, and also the game value within mixed strategies of it. Second, we show that the pairwise-bargained consistency with reference point being the maxmin or the minmax value determines the nucleolus in some class of transferable utility games. (This result is known in the bankruptcy games and the pseudoconcave games with respect to supersets of the managers.) This class of games whose element we call a pseudoconcave game with respect to essential coalitions, of course, includes the bankruptcy games and the pseudoconcave games with respect to supersets of the managers. It is proved that this class of games is exactly the same as the class of games which have a nonempty core that is determined only by one-person and (n − 1)-person coalition constraints. And we give a sufficient condition which guarantees that the bargaining set coincides with the core in this class of games. Third, we interpret the τ-value of a quasibalanced transferable utility game by the pairwise-bargained consistency with reference point being the game value. Finally, by combining the second and the third results, if a transferable utility game in this class is also semiconvex, then the nucleolus and the τ-value are characterized by the pairwise-bargained consistency with different reference points which are given by the associated bimatrix game.     

DIAGAL: An Agent Communication Language Based on Dialogue Games and Sustained by Social Commitments

In recent years, social commitment based approaches have been proposed to solve problems issuing from previous mentalistic based semantics for agent communication languages. This paper follows the same line of thought since it presents the latest version of our dialogue game based agent communication language – DIAlogue-Game based Agent Language (DIAGAL) – which allows agents to manipulate the public layer of social commitments through dialogue, by creating, canceling and updating their social commitments. To make apparent such commitments, we consider here Agent Communication Language (ACL) from the dialectic point of view, where agents “play a game” based on commitments. Such games based on commitments are incorporated in the DIAGAL language, which has been developed having in mind the following questions: (a) What kind of structure does the game have? How are rules specified within the game? (b) What kind of games compositions are allowed? (c) How do participants in conversations reach agreement on the current game? How are games opened or closed? Using such games we show how we can study the commitments dynamic to model agent dialogue and we present metrics that can be used to evaluate the quality of a dialogue between agents. Next, we use an example (summer festival organization) to show how DIAGAL can be used in analyzing and modeling automated conversations in offices. Finally, we present the results and analysis of the summer festival simulations that we realized through our dialogue game simulator (DGS).     

Evolutionary collective behavior decomposition model for time series data mining

In this research, we propose a novel framework referred to as collective game behavior decomposition where complex collective behavior is assumed to be generated by aggregation of several groups of agents following different strategies and complexity emerges from collaboration and competition of individuals. The strategy of an agent is modeled by certain simple game theory models with limited information. Genetic algorithms are used to obtain the optimal collective behavior decomposition based on history data. The trained model can be used for collective behavior prediction. For modeling individual behavior, two simple games, the minority game and mixed game are investigated in experiments on the real-world stock prices and foreign-exchange rate. Experimental results are presented to show the effectiveness of the new proposed model.     

New Algorithms for Solving Simple Stochastic Games

We present new algorithms for determining optimal strategies for two-player games with proba- bilistic moves and reachability winning conditions. Such games, known as simple stochastic games, were extensively studied by A.Condon [Anne Condon. The complexity of stochastic games. Information and Computation, 96(2):203–224, 1992, Anne Condon. On algorithms for simple stochastic games. In Jin-Yi Cai, editor, Advances in Computational Complexity Theory, volume 13 of DIMACS Series in Discrete Mathematics and Theoretical Computer Science, pages 51–73. AMS, 1993]. Many interesting problems, including parity games and hence also mu-calculus model checking, can be reduced to simple stochastic games. It is an open problem, whether simple stochastic games can be solved in polynomial time. Our algorithms determine the optimal expected payoffs in the game. We use geometric interpre- tation of the search space as a subset of the hyper-cube [0,1]^N. The main idea is to divide this set into convex subregions in which linear optimization methods can be used. We show how one can proceed from one subregion to the other so that, eventually, a region containing the optinal payoffs will be found. The total number of subregions is exponential in the size of the game but, in practice, the algorithms need to visit only few of them to find a solution. We believe that our new algorithms could provide new insights into the difficult problem of deter- mining algorithmic complexity of simple stochastic games and other, equivallent problems.     

Evaluation of semi-automatically generated accessible interfaces for educational games

The increasing body of evidence supporting the use of videogames in educational settings (usually referred to as serious games) is pushing their deployment across different areas of the educational system. However, this increased adoption also raises serious ethical issues: videogames are one of the least accessible forms of multimedia, and if education is to embrace serious games, there is an imperative need for universal accessibility in serious games to prevent a digital divide. However, producing accessible games is expensive and effort consuming, and serious games development already fare with limited budgets. In this work we explore the potential impact of the (semi-) automatic adaptation of game interfaces as a way to facilitate accessible game development (and thus trim the cost down). We propose a game interface model optimized for point-and-click adventure games, a popular genre among serious games that we have used to perform different semi-automatic adaptations in a game. We have tested the resulting adapted game with end users with specific disability profiles. Our tests discovered that the automatic adaptations produced usable games that retained part of their attractive, although different usability issues had a negative impact on the user experience. We also discuss the origins of such limitations and propose possible remediation actions, as well as a refined interface model.     

On the Existence and Uniqueness of Equilibrium Situations in Markovian Games with Discounting

Markovian (stochastic) two-person games with discounting are considered. It is proved that if the set of states of such a game and the set of decisions of the players are finite, then the game has values and both players have optimal stationary strategies. The proof, which is based on the principle of contracting mappings, is constructive and leads to a recurrent algorithm of finding solutions of the game. The question of uniqueness of an equilibrium situation in the game considered is also discussed. In addition to the Markovian game with discounting in the context of the principle of contracting mappings, its subgame, namely, a Markovian decision process with discounting is also studied.     

On the usability and likeability of virtual reality games for education: The case of VR-ENGAGE

Educational software games aim at increasing the students’ motivation and engagement while they learn. However, if software games are targeted to school classrooms they have to be usable and likeable by all students. Usability of virtual reality games may be a problem because these games tend to have complex user interfaces so that they are more attractive. Moreover, if the games acquire an educational content they may lose the attractiveness and appeal that they have on users who are familiar with commercial games. Consequently, likeability may also be questioned. In this paper, we address the issue of usability and likeability of a virtual reality game that is meant to teach students geography. We describe the evaluation experiments conducted, which involved three categories of students in terms of their level of game-playing expertise: novice, intermediate and expert game players. The evaluation results showed that the game was indeed usable and likeable but there was scope for usability and likeability improvement so that the educational benefits may be maximised for all categories of students. The evaluation studies reported in this paper, revealed important issues about further research on virtual reality educational games.