Miguel Rebollo

An open architecture for service-oriented virtual organizations

Recent technological advances in open systems have imposed new needs on multi-agent systems. Nowadays, open systems require open autonomous scenarios in which heterogeneous entities (agents or services) interact to fulfill the system goals. The main contribution of this paper is the definition of an open architecture and computational model for largescale open multi-agent systems based on a service-oriented approach. This work requires a high-level design of all features and needs for systems of this kind. The new proposed architecture, called THOMAS, is specifically addressed for the design of virtual organizations. A simplified example for the management of a travel agency system, which shows the features of the proposal, is also included.

Enhancing decentralized service discovery in open service-oriented multi-agent systems

Service-oriented multi-agent systems are dynamic systems that are populated by heterogeneous agents. These agents model their functionality as services in order to allow heterogeneous agents or other entities to interact with each other in a standardized way. Furthermore, due to the large-scale and adaptative needs of the system, traditional directory facilitators or middle-agents are not suitable for the management of agent services. This article proposes the introduction of homophily in service-oriented multi-agent systems to create efficient decentralized and self-organized structures where agents have a greater probability of establishing links with similar agents than with dissimilar ones. This similarity is based on two social dimensions: the set of services that an agent provides and the organizational roles that it plays. A second contribution is an algorithm for service discovery that it is carried out taking into account the local information that is related to the homophily between agents. The experiments compare our proposal with other proposals in distributed environments. The results show that the proposed structure and algorithm offer desirable features for service discovery in decentralized environments. Specifically, these features provide short paths and a high success rate in the service discovery process and resilience under deliberate failures.

Multi-domain case-based module for customer support

Technology management centres provide technological and customer support services for private or public organisations. Commonly, these centres offer support by using a helpdesk software that facilitates the work of their operators. In this paper, a CBR module that acts as a solution recommender for customer support environments is presented. The CBR module is flexible and multi-domain, in order to be easily integrable with any existing helpdesk software in the company.

Agent Design Using Model Driven Development

Object-oriented software development methodologies have adopted a model-driven approach to analysis and design phases. Currently, a similar approach is being adopted for Multi-Agent Systems to improve the development process and the quality of the agent-based software. Model-Driven Development is a technique that allows to obtain executable code by means of transformations from models and meta-models. This work presents a transformation process that allows to generate automatically the code of an agent over his execution platform. That is, an agent is developed under the MDD approach in an easy and transparent way for the user. The code obtained from the transformations is executed over Andromeda and JADE-Leap embedded agent platforms.

SIMBA: An Approach for Real-Time Multi-agent Systems

The use of the agent/multi-agent system paradigm has increased sharply as an important field of research within the Artificial Intelligence area. In recent times, the application of this paradigm seems appropriate for solving complex problems which require intelligence and bounded response times. This paper presents Simba : an architecture based on ARTIS agents as its main component for the development of real-time multi-agent systems. The ARTIS agent architecture guarantees an agent response that satisfies all its critical temporal restrictions in a real-time environment. The main feature of SIMBA systems is their applicability for complex, distributed, real-time domains. The architecture allows the communication among agents taking into account their hard temporal restrictions. In order to show the use of systems of this kind, the paper describes the design of a multi-agent system for the distributed intelligent control of a residential building.

Does the type of event influence how user interactions evolve on Twitter

The number of people using on-line social networks as a new way of communication is continually increasing. The messages that a user writes in these networks and his/her interactions with other users leave a digital trace that is recorded. Thanks to this fact and the use of network theory, the analysis of messages, user interactions, and the complex structures that emerge is greatly facilitated. In addition, information generated in on-line social networks is labeled temporarily, which makes it possible to go a step further analyzing the dynamics of the interaction patterns. In this article, we present an analysis of the evolution of user interactions that take place in television, socio-political, conference, and keynote events on Twitter. Interactions have been modeled as networks that are annotated with the time markers. We study changes in the structural properties at both the network level and the node level. As a result of this analysis, we have detected patterns of network evolution and common structural features as well as differences among the events.

Combination of self-organization mechanisms to enhance service discovery in open systems

Abstract Decentralized systems have emerged as an alternative to centralized approaches for dealing with dynamic requirements in new business models. These systems should provide mechanisms that contribute to flexibility and facilitate adaptation to changes in the environment. In this paper, we present two self-organization mechanisms for a decentralized service discovery system in order to improve its performance. These mechanisms are based on local actions of agents that only consider local information about queries they forward during the discovery process. The self-organization actions are chosen by each agent individually when the agent considers them to be appropriate. The actions are: remaining in the system, leaving the system, cloning, and changing structural relations with other agents. We have evaluated each self-organization mechanism separately but also the combination of the two as the environmental conditions in the service demand change. The results show that the proposed self-organization mechanisms considerably improve the performance of the service discovery system.

A formal model based on Game Theory for the analysis of cooperation in distributed service discovery

New systems can be designed, developed, and managed as societies of agents that interact with each other by offering and providing services. These systems can be viewed as complex networks where nodes are bounded rational agents. In order to deal with complex goals, they require cooperation of the other agents to be able to locate the required services. The aim of this paper is formally and empirically analyze under which circumstances cooperation emerges in decentralized search of services. We propose a repeated game model that formalizes the interactions among agents in a search process where agents are free to choose between cooperate or not in the process. Agents make decisions based on the cost of their actions and the expected reward if they participate forwarding queries in a search process that ends successfully. We propose a strategy that is based on random-walks, and we study under what conditions the strategy is a Nash equilibrium. We performed several experiments in order to evaluate the model and the strategy and to analyze which network structures are more appropriate to promote cooperation.

STRS: Social Network Based Recommender System for Tourism Enhanced with Trust

Nowadays, the development and use of Recommender Systems has grown significantly as a tool to counteract the overload information problem, by selecting a subset of personalized items from a huge set of information based on user preferences. On the other hand, Multi-Agent System applications have shown to be an important area where the Recommender System theory can be applied. This paper presents a tourism Recommender System architecture integrating Multi-Agent Technology and Social Network Analysis, applying trust concepts to create relevant and good quality personalized recommendations trying to solve the tourist Recommender Systems issues.

Promoting cooperation in service-oriented MAS through social plasticity and incentives

Highlights? We propose a model to promote cooperation in decentralized service discovery scenarios where agent is situated in a network based on social preferences. ? The model integrates structural changes and the use of incentives to promote and maintain cooperation even in scenarios where there is a large number of non-cooperative agents. ? The model does not rely on third parties to take decisions. Each agent relies on local information generated during the service discovery process to take decisions about its neighbors and its behavior. In distributed environments where entities only have a partial view of the system, cooperation plays a key issue. In the case of decentralized service discovery in open service-oriented multi-agent systems, agents only know about the services they provide and their direct neighbors. Therefore, they need the cooperation of their neighbors in order to locate the required services. However, cooperation is not always present in open and distributed systems. Non-cooperative agents pursuing their own goals could refuse to forward queries from other agents to avoid the cost of this action; therefore, the efficiency of the decentralized service discovery could be seriously damaged. In this paper, we propose the combination of local structural changes and incentives in order to promote cooperation in the service discovery process. The results show that, even in scenarios where the predominant behavior is not collaborative the cooperation emerges.