Risk-bounded formation of fuzzy coalitions among service agents.

Cooperative autonomous agents form coalitions in order ro share and combine resources and services to efficiently respond to market demands. With the variety of resources and services provided online today, there is a need for stable and flexible techniques to support the automation of agent coalition formation in this context. This paper describes an approach to the problem based on fuzzy coalitions. Compared with a classic cooperative game with crisp coalitions (where each agent is a full member of exactly one coalition), an agent can participate in multiple coalitions with varying degrees of involvement. This gives the agent more freedom and flexibility, allowing them to make full use of their resources, thus maximising utility, even if only comparatively small coalitions are formed. An important aspect of our approach is that the agents can control and bound the risk caused by the possible failure or default of some partner agents by spreading their involvement in diverse coalitions

Cooperative Games with Overlapping Coalitions

In the usual models of cooperative game theory, the outcome of a coalition formation process is either the grand coalition or a coalition structure that consists of disjoint coalitions. However, in many domains where coalitions are associated with tasks, an agent may be involved in executing more than one task, and thus may distribute his resources among several coalitions. To tackle such scenarios, we introduce a model for cooperative games with overlapping coalitions--or overlapping coalition formation (OCF) games. We then explore the issue of stability in this setting. In particular, we introduce a notion of the core, which generalizes the corresponding notion in the traditional (non-overlapping) scenario. Then, under some quite general conditions, we characterize the elements of the core, and show that any element of the core maximizes the social welfare. We also introduce a concept of balancedness for overlapping coalitional games, and use it to characterize coalition structures that can be extended to elements of the core. Finally, we generalize the notion of convexity to our setting, and show that under some natural assumptions convex games have a non-empty core. Moreover, we introduce two alternative notions of stability in OCF that allow a wider range of deviations, and explore the relationships among the corresponding definitions of the core, as well as the classic (non-overlapping) core and the Aubin core. We illustrate the general properties of the three cores, and also study them from a computational perspective, thus obtaining additional insights into their fundamental structure

Value allocations in economies with coalition structure

We embody a notion of stability for coalition structures by Hart and Kurz (1983) into the framework of general equilibrium, by generalizing the classical value allocation notion (Shapley, 1969) to situations where: (a) agents organize themselves voluntarily into coalition structures (b) the process of coalition formation is treated as endogenous. To this end we introduce the definition of stable coalition structure value allocation and provide, under standard hypotheses, a preliminary existence result for the three player case in an exchange economy.

Computational Intelligence Inspired Data Delivery for Vehicle-to-Roadside Communications

We propose a vehicle-to-roadside communication protocol based on distributed clustering where a coalitional game approach is used to stimulate the vehicles to join a cluster, and a fuzzy logic algorithm is employed to generate stable clusters by considering multiple metrics of vehicle velocity, moving pattern, and signal qualities between vehicles. A reinforcement learning algorithm with game theory based reward allocation is employed to guide each vehicle to select the route that can maximize the whole network performance. The protocol is integrated with a multi-hop data delivery virtualization scheme that works on the top of the transport layer and provides high performance for multi-hop end-to-end data transmissions. We conduct realistic computer simulations to show the performance advantage of the protocol over other approaches

Cooperative games with overlapping coalitions

In the usual models of cooperative game theory, the outcome of a coalition formation process is either the grand coalition or a coalition structure that consists of disjoint coalitions. However, in many domains where coalitions are associated with tasks, an agent may be involved in executing more than one task, and thus may distribute his resources among several coalitions. To tackle such scenarios, we introduce a model for cooperative games with overlapping coalitions—or overlapping coalition formation (OCF) games. We then explore the issue of stability in this setting. In particular, we introduce a notion of the core, which generalizes the corresponding notion in the traditional (non-overlapping) scenario. Then, under some quite general conditions, we characterize the elements of the core, and show that any element of the core maximizes the social welfare. We also introduce a concept of balancedness for overlapping coalitional games, and use it to characterize coalition structures that can be extended to elements of the core. Finally, we generalize the notion of convexity to our setting, and show that under some natural assumptions convex games have a non-empty core. Moreover, we introduce two alternative notions of stability in OCF that allow a wider range of deviations, and explore the relationships among the corresponding definitions of the core, as well as the classic (non-overlapping) core and the Aubin core. We illustrate the general properties of the three cores, and also study them from a computational perspective, thus obtaining additional insights into their fundamental structure

Optimality of equilibria in differential information economies with restricted coalitions

It is well known that the set of unblocked allocations, the core, and the set of Walras allocations coincide in an atomless economy when all measurable coalitions are allowed to form. Clearly, if only a subset of the set of all coalitions is allowed to form, the set of unblocked allocations enlarges, and generally we can merely say that this larger set contains the set of Walrasian allocations. In reality the lack of communication restricts the set of coalitions that can be formed. The purpose of our work is investigate the Core-Walras equivalence by imposing to the set of all coalitions some restrictions. The notion of the core is based on the premise that any group of agents can cooperate and agree upon a coordinated set of actions which can then be enforced. In the context of a differential information economy, an allocation should be seen as a state-contingent allocation satisfying physical resource constraints in each information state. A central role is played by the information set of each agent. Agents which enter into a coalition contract at the ex-ante stage, i.e. before any agents receives private information, or at the interim, i.e. after each agent has received her private information. It is well known that the ex-post stage, i.e. decisions are made after the information state is known, is no different from a model with complete information. An appropriate notion of the core must take into account of whether the coalition decisions stage is ex-ante or interim. In our work we specially deal with the private core which is an ex-ante concept. It has some interesting properties: it exists under standard continuity and concavity assumptions on utility functions, it is coalitionally incentive, i.e. there is truthful revelation of information in each coalition, and it takes into account the information superiority of traders. From the non cooperative side, we deal with two main equilibrium concepts: • the rational expectations equilibrium which is an interim concept in which prices are referred to as signals reflecting and transferring information; • the competitive private equilibrium, which is closer to the Walrasian equilibrium notion in the deterministic case: this non-cooperative solution concept presumes that agents maximize their ex-ante expected utility subject to their budget constraint in which information constraints, besides the classical ones, are considered. We will consider a differential information exchange economy obtained by introducing in the classical Arrow-Debreu model both uncertainty and asymmetries in information. In these model, uncertainty is exogenous and is represented by a measure space (Ω,F) where Ω denotes the finite set of all possible states of nature and F is the set of all possible events. We will assume that agents make coalitional decisions at the ex-ante stage but each agent receives private information which is not publicly verifiable before consumption takes place. In particular, agents trades with the anonymous market rather than with other agents directly and it becomes very natural to require that agents' trade be measurable with respect to their private information. We characterize in terms of decentralizing prices several notions of core allocations resulting from different possible restrictions imposed to the set of blocking coalitions. Reciprocal relations among cores are also studied. Another issue we have investigated in our work, starting from the reality restrictions of coalitions due by various rules imposed over the society (i.e. information, transportation, legal and institutional constraints), is the number and composition of the set of blocking coalitions