Open Multi-agent Systems Research Articles

EVALUATING PERFORMANCE AND ACCURACY OF A SENTINEL-BASED EXCEPTION DIAGNOSIS APPROACH FOR P2P AGENT SYSTEMS

Using open Multi-agent systems (MAS) to represent a peer-to-peer (P2P) organization is a complex application of distributed artificial intelligence. These systems are designed to create networked applications where each peer node contributes to the overall functionality of the application. Each agent in such systems acts as a peer and has no fixed role. In other words a peer may assume the role of either service provider or service consumer in a given interaction. The dynamics of these networked applications make them vulnerable to different kinds of exceptions. Also the absence of centralized control and changes in organizational structure gives rise to unpredictable exceptions. It becomes essential to have some exception diagnosis mechanisms in place to be able to diagnose the cause of such exceptions while preserving the autonomy of the peer agents. These mechanisms do come with some overheads. In this paper we present an evaluation of the application of our proposed sentinel based approach to exception diagnosis in P2P based MAS and also discuss the trade offs that arise in using a sentinel based approach to exception diagnosis in such systems.

Mapping deontic operators to abductive expectations

Deontic concepts and operators have been widely used in several fields where representation of norms is needed, including legal reasoning and normative multi-agent systems.The EU-funded SOCS project has provided a language to specify the agent interaction in open multi-agent systems. The language is equipped with a declarative semantics based on abductive logic programming, and an operational semantics consisting of a (sound and complete) abductive proof procedure. In the SOCS framework, the specification is used directly as a program for the verification procedure.In this paper, we propose a mapping of the usual deontic operators (obligations, prohibition, permission) to language entities, called expectations, available in the SOCS social framework. Although expectations and deontic operators can be quite different from a philosophical viewpoint, we support our mapping by showing a similarity between the abductive semantics for expectations and the Kripke semantics that can be given to deontic operators.The main purpose of this work is to make the computational machinery from the SOCS social framework available for the specification and verification of systems by means of deontic operators.

Self-regulation through social institutions: A framework for the design of open agent-based electronic marketplaces

In this paper, we argue that allowing self-interested agents to activate social institutions during runtime can improve the robustness (i.e., stability, reliability, or scalability) of open multiagent systems (MAS). Referring to sociological theory, we consider institutions to be rules that need to be activated and adopted by the agent population during runtime and propose a framework for self-regulation of MAS for the domain of electronic marketplaces. The framework consists of three different institutional types that are defined by the mechanisms and instances that generate, change or safeguard them. We suggest that allowing autonomous agents both the reasoning about their compliance with a rule and the selection of an adequate institutional types helps to balance the trade-off between the autonomy of self-interested agents and the maintenance of social order (cf. Castelfranchi, 2000) in MAS, and to ensure almost the same qualities as in closed environments. A preliminary report of the evaluation of the prototype by empirical simulations is given.

Agent communication and artificial institutions

In this paper we propose an application-independent model for the definition of artificial institutions that can be used to define open multi-agent systems. Such a model of institutional reality makes us able also to define an objective and external semantics of a commitment-based Agent Communication Language (ACL). In particular we propose to regard an ACL as a set of conventions to act on a fragment of institutional reality, defined in the context of an artificial institution. Another contribution of the work presented in this paper is an operational definition of norms, a crucial component of artificial institutions. In fact in open systems interacting agents might not conform to the specifications. We regard norms as event-driven rules that when are fired by events happening in the system create or cancel a set of commitments. An interesting aspect of our proposal is that both the definition of the ACL and the definition of norms are based on the same notion of commitment. Therefore an agent capable of reasoning on commitments can reason on the semantics of communicative acts and on the system of norms.

Une approche multi-agent pour la gestion de la communication dans les réseaux de capteurs sans fil

This paper deals with multiagent self-organization giving adaptive features to a distributed system embodied in an agressive environment. It proposes an original approach of open multiagent systems in the context of wireless networks of intelligent sensors. Such networks are composed by sensors with independant energy sources. These networks need routing techniques which minimize communication energy cost with a strong fault tolerant feature. The paper presents finally the simulation platform, which we built, who allows us to compare our solution based on self-organization and common ad hoc routing protocols.

Coordinating Agents in Organizations Using Social Commitments

One of the main challenges faced by the multi-agent community is to ensure the coordination of autonomous agents in open heterogeneous multi-agent systems. In order to coordinate their behaviour, the agents should be able to interact with each other. Social commitments have been used in recent years as an answer to the challenges of enabling heterogeneous agents to communicate and interact successfully. However, coordinating agents only by means of interaction models is difficult in open multi-agent systems, where possibly malevolent agents can enter at any time and violate the interaction rules. Agent organizations, institutions and normative systems have been used to control the way agents interact and behave. In this paper we try to bring together the two models of coordinating agents: commitment-based interaction and organizations. To this aim we describe how one can use social commitments to represent the expected behaviour of an agent playing a role in an organization. We thus make a first step towards a unified model of coordination in multi-agent systems: a definition of the expected behaviour of an agent using social commitments in both organizational and non-organizational contexts.

Communication Attitudes: A Formal Approach to Ostensible Intentions, and Individual and Group Opinions

Conventional approaches to the modeling of autonomous agents and agent communication rely heavily on the ascription of mental properties like beliefs and intentions to the individual agents. These “mentalistic” approaches are, when applicable, very powerful, but become problematic in open environments like the Semantic Web, Peer2Peer systems and open multiagent systems populated by truly autonomous, self-interested grey- or black-box agents with limited trustability.In this work, we propose communication attitudes in form of dynamic, revisable ostensible beliefs (or opinions) and ostensible intentions as foundational means for the logical, external description of agents obtained from the observation of communication processes, in order to retain the advantages of mentalistic agent models as far as possible, but with verifiable results without the need to speculate about covert agent internals. As potential applications, communication attitudes allow for a simultaneous reasoning about the (possibly inconsistent) "public image(-s)" of a certain agent and her mental properties without blurring interferences, new approaches to communication language semantics, and a fine-grained, statement-level concept of trustability.As a further application of communicative attitudes, we introduce multi-source opinions and opinion bases. These allow for the computational representation of semantically heterogeneous knowledge, including the representation of inconsistent knowledge in a socially reified form, and a probabilistic weighting of possibly indefinite and inconsistent assertions explicitly attributed to different provenances and social contexts.

Representing Conversations for Scalable Overhearing

Open distributed multi-agent systems are gaining interest in the academic community and in industry. In such open settings, agents are often coordinated using standardized agent conversation protocols. The representation of such protocols (for analysis, validation, monitoring, etc) is an important aspect of multi-agent applications. Recently, Petri nets have been shown to be an interesting approach to such representation, and radically different approaches using Petri nets have been proposed. However, their relative strengths and weaknesses have not been examined. Moreover, their scalability and suitability for different tasks have not been addressed. This paper addresses both these challenges. First, we analyze existing Petri net representations in terms of their scalability and appropriateness for overhearing, an important task in monitoring open multi-agent systems. Then, building on the insights gained, we introduce a novel representation using Colored Petri nets that explicitly represent legal joint conversation states and messages. This representation approach offers significant improvements in scalability and is particularly suitable for overhearing. Furthermore, we show that this new representation offers a comprehensive coverage of all conversation features of FIPA conversation standards. We also present a procedure for transforming AUML conversation protocol diagrams (a standard human-readable representation), to our Colored Petri net representation.

An integrated trust and reputation model for open multi-agent systems

Trust and reputation are central to effective interactions in open multi-agent systems (MAS) in which agents, that are owned by a variety of stakeholders, continuously enter and leave the system. This openness means existing trust and reputation models cannot readily be used since their performance suffers when there are various (unforseen) changes in the environment. To this end, this paper presents FIRE, a trust and reputation model that integrates a number of information sources to produce a comprehensive assessment of an agent's likely performance in open systems. Specifically, FIRE incorporates interaction trust, role-based trust, witness reputation, and certified reputation to provide trust metrics in most circumstances. FIRE is empirically evaluated and is shown to help agents gain better utility (by effectively selecting appropriate interaction partners) than our benchmarks in a variety of agent populations. It is also shown that FIRE is able to effectively respond to changes that occur in an agent's environment.

SELF-LEARNING DECISIONAL INFORMATION SYSTEM FOR SECURITY (SL-D.I.S.S.) FOR HUMAN SPACE RXPLORATION MISSION

This paper presents a Self-Learning Decisional Information System for Security (SL-D.I.S.S.) dedicated to the Human Space Exploration Mission. The objective is to conceive a decisional information system for human long duration space flight (> 950 days) which will be realise in entire autonomy in the solar system. This article describes the importance of the ontological and epistemological context for designing an open multi-agent and reliable system able for self-adapt in dangerous and unforeseen situations. We present in link with our research, the limits of the empirical analytical paradigm and several paths of research lead by the nascent paradigm of enaction. The strong presumption is that classical ways of modelisation could not respond and challenge the security of a technical system which will support human exploration missions.

Information Quality Assurance by Lazy Exploration of Information Source Combinations Space in Open Multi-Agent Systems

Information quality assurance under the existence of uncertainty can be investigated in the context of soft security, where an agent maintains trustworthiness evaluations of its information sources to assist in the evaluation of incoming information quality from those sources. Since dependency inherently exists in a system where agents do not have self- sufficient sensing or data collection capabilities, finding an appropriate set of information sources is important for assuring the quality of information and for increasing the agent's goal achievement. This research proposes an approach for selecting information sources as partners. In order to increase the efficiency and the accuracy, we use trustworthiness, information cost and goal coverage as the metrics for information valuation while adopting a lazy exploration of information sources combination space. Experimental results show that the proposed approach increases the efficiency and results in quality information acquisition.

MASCARET

This study concerns virtual environments for training in operational conditions. The principal developed idea is that these environments are heterogeneous and open multi-agent systems. The MASCARET model is proposed to organize the interactions between agents and to provide them reactive, cognitive and social abilities to simulate the physical and social environment. The physical environment represents, in a realistic way, the phenomena that learners and teachers have to take into account. The social environment is simulated by agents executing collaborative and adaptive tasks. These agents realize, in team, procedures that they have to adapt to the environment. The users participate to the training environment through their avatar. In this article, we explain how we integrated, in MASCARET, models necessary to the creation of Intelligent Tutoring System. We notably incorporate pedagogical strategies and pedagogical actions. We present pedagogical agents. To validate our model, the SÉCURÉVI application for fire fighters’ training is developed.

MAIS ­ Un système multi-agents pour la recherche d'information sur le web

In this paper we present a multi-agent system for searching the Internet. The search for interesting documents on the Internet is becoming increasingly difficult, mainly because search engines cannot cope with the expansion of the Internet. Consequently, the results of queries are often of very poor quality. Multi-agent systems can give more accurate results than traditional search engines because agents can be specialized in different tasks (search or filtering) and can personalize information. We implemented such an approach using an open multi-agent system containing personal assistants, library agents, filter agents and search agents. In this paper, we detail the elements of our multi-agent system and compare its performance with more traditional search engines. Our results yield a better accuracy.

Open Multi-Agent Systems for Collaborative Web-Based Learning

Web-based learning plays an important role in the modern teaching environment. Many Web-based tools are becoming available in this huge marketplace. Agent technology contributes substantially to this achievement. One of the fundamental problems facing both students and education services providers is how to locate and integrate these valuable services in such a dynamic environment. In this paper, I present mediator-based architecture to build open multi-agent applications for eLearning. An agent services description language is presented to enable services advertising and collaboration. The language exploits ontology of service domain, and provides the flexibility for developers to plug in any suitable constraint languages. Multiple matchmaking strategies based on agent service ontology are given to help agents finding appropriate service providers. The series of strategies consider various features of service providers, the nature of requirements, and more importantly the relationships among services.

Using Domain-Independent Exception Handling Services to Enable Robust Open Multi-Agent Systems: The Case of Agent Death

This paper addresses a simple but critical question: how can we create robust multi-agent systems out of the often unreliable agents and infrastructures we can expect to find in open systems contexts? We propose an approach to this problem based on distinct exception handling (EH) services that enact coordination protocol-specific but domain-independent strategies to monitor agent systems for problems (‘exceptions’) and intervene when necessary to avoid or resolve them. The value of this approach is demonstrated for the ‘agent death’ exception in the Contract Net protocol; we show through simulation that the EH service approach provides substantially improved performance compared to existing approaches in a way that is appropriate for open multi-agent systems.

Mobile agent security

The agent paradigm is currently attracting much research. A mobile agent is a particular type of agent with the ability to migrate from one host to another, where it can resume its execution. We consider security issues that need to be addressed before multi-agent systems in general, and mobile agents in particular, can be a viable solution for a broad range of commercial applications. This is done by considering the implications of the characteristics given to agents and the general properties of open multi-agent systems. The paper then looks in some more detail at security technology and methods applicable to mobile agent systems.

Negotiating the Semantics of Agent Communication Languages

This article presents a formal framework and outlines a method that autonomous agents can use to negotiate the semantics of their communication language at run–time. Such an ability is needed in open multi–agent systems so that agents can ensure they understand the implications of the utterances that are being made and so that they can tailor the meaning of the primitives to best fit their prevailing circumstances. To this end, the semantic space framework provides a systematic means of classifying the primitives along multiple relevant dimensions. This classification can then be used by the agents to structure their negotiation (or semantic fixing) process so that they converge to the mutually agreeable semantics that are necessary for coherent social interactions.

Management of Renewable Resources in the Open Multi-Agent System

The problem of management of the renewable resources appears in different fields like the ecological systems, city traffic, network bandwidth etc. These problems often have distributed and decentralized nature and are solved by activity of reasoning entities, so application of the multi-agent systems (MAS) seems to be appropriate and profitable. In the paper the system SMAORR - simulation of the open multiagent system with the renewable resources is presented. The system is composed of heterogeneous population of agents and resources located in the environment. The agents realize their goals performing activities for their own benefit or for benefit of other agents.

On Achievable Goals and Feasible Plans in Open Multi-Agent Systems

Abstract In this paper, we present a subjective representation of the notions of feasible plans and achievable goals , in order to model the decision mechanism of autonomous agents, immersed in an open multi-agent context. By open, we mean that agents may enter or leave the agency at any moment, without a centralized control. We believe that an agent who uses this model can better adapt himself to the changing conditions of the system, specifically to the fact that services may dynamically become available/not available.

Expert-Coop: An Environment for Cognitive Multi-Agent Systems

Abstract A modular object-oriented environment, called Expert-Coop, designed to help the implementation of open heterogeneous cognitive Multi-Agent Systems is presented in this paper. The environment consists of a library of classes that supports the creation of agents according to a predefined concurrent agent architecture. The environment is written in Common Lisp/CLOS and its modularity, guaranteed by the object-oriented design methodology, makes it easy to modify and augment it with new features. The environment is being used to develop an application concerning the restoration of an electricity transmission network, covering Brazil's south region, after a blackout has affected part of the network.