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Coalition Structures in Weighted Voting Games

Coalition Structures in Weighted Voting Games
Coalition Structures in Weighted Voting Games
Weighted voting games are a popular model of collaboration in multiagent systems. In such games, each agent has a weight (intuitively corresponding to resources he can contribute), and a coalition of agents wins if its total weight meets or exceeds a given threshold. Even though coalitional stability in such games is important, existing research has nonetheless only considered the stability of the grand coalition. In this paper, we introduce a model for weighted voting games with coalition structures. This is a natural extension in the context of multiagent systems, as several groups of agents may be simultaneously at work, each serving a different task. We then proceed to study stability in this context. First, we define the CS-core, a notion of the core for such settings, discuss its non-emptiness, and relate it to the traditional notion of the core in weighted voting games. We then investigate its computational properties. We show that, in contrast with the traditional setting, it is computationally hard to decide whether a game has a non-empty CS-core, or whether a given outcome is in the CS-core. However, we then provide an efficient algorithm that verifies whether an outcome is in the CS-core if all weights are small (polynomially bounded). Finally, we also suggest heuristic algorithms for checking the non-emptiness of the CS-core.
393-397
Elkind, Edith
7a013473-5cd0-4e41-b907-66b30a04a400
Chalkiadakis, Georgios
50ef5d10-3ffe-4253-ac88-fad4004240e7
Jennings, Nick
ab3d94cc-247c-4545-9d1e-65873d6cdb30
Elkind, Edith
7a013473-5cd0-4e41-b907-66b30a04a400
Chalkiadakis, Georgios
50ef5d10-3ffe-4253-ac88-fad4004240e7
Jennings, Nick
ab3d94cc-247c-4545-9d1e-65873d6cdb30

Elkind, Edith, Chalkiadakis, Georgios and Jennings, Nick (2008) Coalition Structures in Weighted Voting Games. Proc. 18th European Conf on AI (ECAI), Greece. pp. 393-397 .

Record type: Conference or Workshop Item (Paper)

Abstract

Weighted voting games are a popular model of collaboration in multiagent systems. In such games, each agent has a weight (intuitively corresponding to resources he can contribute), and a coalition of agents wins if its total weight meets or exceeds a given threshold. Even though coalitional stability in such games is important, existing research has nonetheless only considered the stability of the grand coalition. In this paper, we introduce a model for weighted voting games with coalition structures. This is a natural extension in the context of multiagent systems, as several groups of agents may be simultaneously at work, each serving a different task. We then proceed to study stability in this context. First, we define the CS-core, a notion of the core for such settings, discuss its non-emptiness, and relate it to the traditional notion of the core in weighted voting games. We then investigate its computational properties. We show that, in contrast with the traditional setting, it is computationally hard to decide whether a game has a non-empty CS-core, or whether a given outcome is in the CS-core. However, we then provide an efficient algorithm that verifies whether an outcome is in the CS-core if all weights are small (polynomially bounded). Finally, we also suggest heuristic algorithms for checking the non-emptiness of the CS-core.

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Published date: 2008
Venue - Dates: Proc. 18th European Conf on AI (ECAI), Greece, 2008-01-01
Organisations: Agents, Interactions & Complexity

Identifiers

Local EPrints ID: 265803
URI: http://eprints.soton.ac.uk/id/eprint/265803
PURE UUID: ab6f1575-e7e5-4cd8-94e9-457e48dcb07b

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Date deposited: 27 May 2008 15:12
Last modified: 09 Dec 2019 20:11

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Contributors

Author: Edith Elkind
Author: Georgios Chalkiadakis
Author: Nick Jennings

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