Results 1  10
of
51
A short introduction to computational social choice
 Proc. 33rd Conference on Current Trends in Theory and Practice of Computer Science
, 2007
"... ..."
Complexity of Constructing Solutions in the Core Based on Synergies among Coalitions
 ARTIFICIAL INTELLIGENCE
, 2006
"... Coalition formation is a key problem in automated negotiation among selfinterested agents, and other multiagent applications. A coalition of agents can sometimes accomplish things that the individual agents cannot, or can accomplish them more efficiently. Motivating the agents to abide by a solut ..."
Abstract

Cited by 33 (1 self)
 Add to MetaCart
Coalition formation is a key problem in automated negotiation among selfinterested agents, and other multiagent applications. A coalition of agents can sometimes accomplish things that the individual agents cannot, or can accomplish them more efficiently. Motivating the agents to abide by a solution requires careful analysis: only some of the solutions are stable in the sense that no group of agents is motivated to break off and form a new coalition. This constraint has been studied extensively in cooperative game theory: the set of solutions that satisfy it is known as the core. The computational questions around the core have received less attention. When it comes to coalition formation among software agents (that represent realworld parties), these questions become increasingly explicit. In this
Modelbased overlapping clustering
 In KDD
, 2005
"... While the vast majority of clustering algorithms are partitional, many real world datasets have inherently overlapping clusters. Several approaches to finding overlapping clusters have come from work on analysis of biological datasets. In this paper, we interpret an overlapping clustering model prop ..."
Abstract

Cited by 29 (6 self)
 Add to MetaCart
While the vast majority of clustering algorithms are partitional, many real world datasets have inherently overlapping clusters. Several approaches to finding overlapping clusters have come from work on analysis of biological datasets. In this paper, we interpret an overlapping clustering model proposed by Segal et al. [23] as a generalization of Gaussian mixture models, and we extend it to an overlapping clustering model based on mixtures of any regular exponential family distribution and the corresponding Bregman divergence. We provide the necessary algorithm modifications for this extension, and present results on synthetic data as well as subsets of 20Newsgroups and EachMovie datasets.
Coalitional games in open anonymous environments
 In AAAI
, 2005
"... Coalition formation is a key aspect of automated negotiation among selfinterested agents. In order for coalitions to be stable, a key question that must be answered is how the gains from cooperation are to be distributed. Various solution concepts (such as the Shapley value, core, least core, and n ..."
Abstract

Cited by 26 (7 self)
 Add to MetaCart
Coalition formation is a key aspect of automated negotiation among selfinterested agents. In order for coalitions to be stable, a key question that must be answered is how the gains from cooperation are to be distributed. Various solution concepts (such as the Shapley value, core, least core, and nucleolus) have been proposed. In this paper, we demonstrate how these concepts are vulnerable to various kinds of manipulations in open anonymous environments such as the Internet. These manipulations include submitting false names (one acting as many), collusion (many acting as one), and the hiding of skills. To address these threats, we introduce a new solution concept called the anonymityproof core, which is robust to these manipulations. We show that the anonymityproof core is characterized by certain simple axiomatic conditions. Furthermore, we show that by relaxing these conditions, we obtain a concept called the least anonymityproof core, which is guaranteed to be nonempty. We also show that computational hardness of manipulation may provide an alternative barrier to manipulation.
Coalitional Skill Games
"... We consider Coalitional Skill Games (CSGs), a simple model of cooperation among agents. This is a restricted form of coalitional games, where each agent has a set of skills that are required to complete various tasks. Each task requires a set of skills in order to be completed, and a coalition can a ..."
Abstract

Cited by 19 (8 self)
 Add to MetaCart
We consider Coalitional Skill Games (CSGs), a simple model of cooperation among agents. This is a restricted form of coalitional games, where each agent has a set of skills that are required to complete various tasks. Each task requires a set of skills in order to be completed, and a coalition can accomplish the task only if the coalition’s agents cover the set of required skills for the task. The gain for a coalition depends only on the subset of tasks it can complete. We consider the computational complexity of several problems in CSGs, for example, testing if an agent is a dummy or veto agent, computing the core of the game or testing whether the core is empty, and finding the Shapley value or Banzhaf power index of agents.
Coalition Structure Generation Utilizing Compact Characteristic Function Representations (Extended Abstract)
"... Forming e ective coalitions is a major research challenge in AI and multiagent systems. Coalition structure generation (CSG), which involves partitioning a set of agents into coalitions so that social surplus is maximized, is a central research topic due to its computational complexity. In this pap ..."
Abstract

Cited by 17 (3 self)
 Add to MetaCart
Forming e ective coalitions is a major research challenge in AI and multiagent systems. Coalition structure generation (CSG), which involves partitioning a set of agents into coalitions so that social surplus is maximized, is a central research topic due to its computational complexity. In this paper, we present new methods for CSG utilizing recently developed compact representation schemes for characteristic functions. We characterize the complexity of CSG under these representation schemes. In this context, the complexity is driven more by the number of synergy coalition groups than by the number of agents. Furthermore, we develop mixed integer programming formulations and show that an otheshelf optimization package can solve these problems quite e ciently.
A compact representation scheme for coalitional games in open anonymous environments
 In AAAI
, 2006
"... Coalition formation is an important capability of automated negotiation among selfinterested agents. In order for coalitions to be stable, a key question that must be answered is how the gains from cooperation are to be distributed. Recent research has revealed that traditional solution concepts, s ..."
Abstract

Cited by 16 (4 self)
 Add to MetaCart
Coalition formation is an important capability of automated negotiation among selfinterested agents. In order for coalitions to be stable, a key question that must be answered is how the gains from cooperation are to be distributed. Recent research has revealed that traditional solution concepts, such as the Shapley value, core, least core, and nucleolus, are vulnerable to various manipulations in open anonymous environments such as the Internet. These manipulations include submitting false names, collusion, and hiding some skills. To address this, a solution concept called the anonymityproof core, which is robust against such manipulations, was developed. However, the representation size of the outcome function in the anonymityproof core (and similar concepts) requires space exponential in the number of agents/skills. This paper proposes a compact representation of the outcome function, given that the characteristic function is represented using a recently introduced compact language that explicitly specifies only coalitions that introduce synergy. This compact representation scheme can successfully express the outcome function in the anonymityproof core. Furthermore, this paper develops a new solution concept, the anonymityproof nucleolus, that is also expressible in this compact representation. We show that the anonymityproof nucleolus always exists, is unique, and is in the anonymityproof core (if the latter is nonempty), and assigns the same value to symmetric skills.
Divide and Conquer: FalseName Manipulations in Weighted Voting Games
, 2008
"... In this paper, we study falsename manipulations in weighted voting games. Weighted voting is a wellknown model of cooperation among agents in decisionmaking domains. In such games, each of the players has a weight, and a coalition of players wins the game if its total weight exceeds a certain quo ..."
Abstract

Cited by 16 (7 self)
 Add to MetaCart
In this paper, we study falsename manipulations in weighted voting games. Weighted voting is a wellknown model of cooperation among agents in decisionmaking domains. In such games, each of the players has a weight, and a coalition of players wins the game if its total weight exceeds a certain quota. While a player’s ability to influence the outcome of the game is related to its weight, it is not always directly proportional to it. This observation has led to the concept of a power index, which is a measure of an agent’s “real power ” in this domain. One prominent power index is the Shapley–Shubik index, which has been widely used to analyze political power. This index is equal to the Shapley value of the player in the game. If an agent can alter the game so that his Shapley–Shubik index increases, this will mean that he has gained power in the game. Moreover,
The cost of stability in coalitional games
 Tech. Rep. arXiv:0907.4385 [cs.GT], ACM Comp. Research Repository
, 2009
"... Abstract. A key question in cooperative game theory is that of coalitional stability, usually captured by the notion of the core—the set of outcomes such that no subgroup of players has an incentive to deviate. However, some coalitional games have empty cores, and any outcome in such a game is unsta ..."
Abstract

Cited by 16 (5 self)
 Add to MetaCart
Abstract. A key question in cooperative game theory is that of coalitional stability, usually captured by the notion of the core—the set of outcomes such that no subgroup of players has an incentive to deviate. However, some coalitional games have empty cores, and any outcome in such a game is unstable. In this paper, we investigate the possibility of stabilizing a coalitional game by using external payments. We consider a scenario where an external party, which is interested in having the players work together, offers a supplemental payment to the grand coalition (or, more generally, a particular coalition structure). This payment is conditional on players not deviating from their coalition(s). The sum of this payment plus the actual gains of the coalition(s) may then be divided among the agents so as to promote stability. We define the cost of stability (CoS) as the minimal external payment that stabilizes the game. We provide general bounds on the cost of stability in several classes of games, and explore its algorithmic properties. To develop a better intuition for the concepts we introduce, we provide a detailed algorithmic study of the cost of stability in weighted voting games, a simple but expressive class of games which can model decisionmaking in political bodies, and cooperation in multiagent settings. Finally, we extend our model and results to games with coalition structures. 1