Carlos Merida-Campos

Modelling Coalition Formation over Time for Iterative Coalition Games

Coalition formation problems arise when groups of agents need to work together to achieve tasks in an environment ¿ such as bidding for a contract or bulk buying goods. The work presented here shows how current theories for coalition formation can be combined with notions from iterative games to cover cases where populations of agents must solve coalition problems many times ¿ modelling a long series of coalition games rather than just a single one. The paper includes a problem formulation for iterative coalition games, experimental results for a simple coalition game world demonstrating how strong coalitions can emerge over time even from basic strategies and a discussion of the interactions between different strategies over time.

Adapting Agent Communication Languages for Semantic Web Service Inter-Communication

The integration of semantic Web and Web services technologies promises to be one of the most promising new areas for development of intelligent Web applications. One challenging area where these technologies meet is in explicit definitions of meaning for the messages exchanged between Web services - in other words, semantic definitions of the meanings of data / commands exchanged in the execution of a Web services based application. While current approaches such as OWL-S tackle these elements in service groundings by mapping processes to function calls with specific arguments, agent communication languages could provide a potentially richer alternative. The work presented here shows how this could be done by mapping the existing agent communication language (FIPA-ACL, FIPA-SL and associated standards developed by the foundation for intelligent physical agents) into OWL based representations which may then be readily used in a Web services environment.

Exploring Social Networks in Request for Proposal Dynamic Coalition Formation Problems

In small scale multi-agent environments, every agent is aware of all of the others. This allows agents to evaluate the potential outcomes of their interaction for each of their possible interaction partners. However, this farsighted knowledge becomes an issue in large scale systems, leading to a combinatorial explosion in evaluation and is unrealistic in communication terms. Limited awareness of other agents is therefore the only plausible scenario in many large-scale environments. This limited awareness can be modeled as a sparse social network in which agents only interact with a limited subset of agents known to them. In this paper, we explore a model of dynamic multi-agent coalition formation in which agents are connected via fixed underlying social networks that exhibit different well known structures such as Small World, Randomand Scale Freetopologies. Agents follow different exploratory policies and are distributed in the network according to a variety of metrics. The primary results of the paper are to demonstrate different positive and negative properties of each topology for the coalition formation problem. In particular we show that despite positive properties for many problems, Small Worldtopologies introduce blocking factors which hinder the emergence of good coalition solutions in many configurations.

Agent compatibility and coalition formation: investigating two interacting negotiation strategies

This paper focuses on the Coalition Formation paradigm as a market mechanism. Concretely, Coalition Formation occurs as part of a wider open world and may occur many times during the lifetime of a population of agents. This fact can in some circumstances be exploited by agents to re-use existing partial coalition and social relationships over time to improve Coalition Formation efficiency. The aim of the work is to analyze the dynamics of two concrete rational behaviors (Competitive and Conservative strategies) and, in particular, to investigate how agents in a heterogeneous population cluster together across multiple Coalition Formation episodes and varying tasks. Preliminary resuls are also shown regarding the manner in which playing distinct strategies interact with one another.

Service Coalitions for Future Internet Services

This paper proposes an algorithm that enables the support for a service market place in which service providers can negotiate and form coalitions in a self-centred approach. We present the main features of the algorithm and evaluate the proposed solution under different technical aspects including social network topology, scalability and convergence to optimal results.

Automated Negotiation in Many-to-Many Markets for Imperfectly Substitutable Goods

In this paper, we present an agent which is able to negotiate the buying and selling of imperfectly sustitutable goods in a double auction style market. Two goods are said to be imperfectly substitutable if a buyer can use either of them, but prefers one over the other. For example, an electronics manufacturer using a RAM chip can use many suppliers to do this but may be willing to pay a premium for components with a lower failure rate. We give a formal description of a double-auction style market mechanism for trading such goods, and define the (classical) equilibrium in such an environment. We present the IS-ZIP agent, which is a generalisation of the ZIP agent for double auctions of Cliff and Bruten [3]. It is able to participate in our double auction environment to make purchases or sales of imperfectly substitutable goods. We demonstrate that, when trading a single good, it is equivalent to Preist and van Tols modification of the ZIP agent [11]. We describe experiments where a group of IS-ZIP agents with different valuations trade repeatedly, and demonstrate that they rapidly converge to our predicted equilibrium. We conclude by relating our work to that of others, particulary work dealing with multi-attribute negotiation, and discussing extensions.

A service-centric orchestration protocol for self-organizing autonomic management systems

This article presents a service-centric orchestration protocol for self-interested autonomic management systems that supports the coalition formation process in largescale collaborative and competitive environments. It supports environments in which coalition formations are carried out targeting multiple service requests at the same time, and in which the autonomic management systems compete to work in the most appropriate coalition. The protocol exploits the benefits of social networking in favor of manageability and scalability. Its performance is analyzed taking into account crucial aspects of self-organizing systems such as stability and convergence to optimal coalition formation results.

Improving the efficiency of case-based reasoning to deal with activated sludge solids separation problems

The potential of Case-Based Reasoning to use the knowledge gained from past experiences to solve problematic situations has made this Artificial Intelligence technique a useful decision support tool in different environmental domains such as wastewater treatment. Case-Based Reasoning tools automatically identify similarities between present and previous situations (cases) and reuse the experiences gained from the previous situations to solve current problems. Case retrieval can be considered to be the most important step in the process of Case-Based Reasoning. In the present study we propose incorporating a relevance network in order to increase the accuracy and the efficiency of case retrieval. The result is a context-sensitive feature-weighting methodology capable of defining the model of relationships between the different attributes or features that define the context in which Case-Based Reasoning is applied. These features affect the retrieval procedure directly. The features degree of relevance in the network is easily translated into a set of simple rules and applied during case retrieval, specifically during the similarity calculation. The results obtained in the present study show significant improvements in the accuracy of case retrieval. With the approach presented here experts considered more than 90% of the retrieved cases to be completely relevant according to the knowledge these cases provided for dealing with solids separation problems.