Catálogo de publicaciones - libros

The dependability of open multi-agent systems is a particular concern, notably because of their main characteristics as decentralization and no single point of control. This paper describes an approach to increase the availability of such systems through a technique of fault tolerance known as agent replication, and to increase their reliability through a mechanism of agent interaction regulation called law enforcement mechanism. Therefore, we combine two frameworks: one for law enforcement, named XMLaw, and another for agent adaptive replication, named DimaX, in which the decision of replicating an agent is based on a dynamic estimation of its criticality. Moreover, we will describe how we can reuse some of the information expressed by laws in order to help at the estimation of agent criticality, thus providing a better integration of the two frameworks. At the end of the paper, we recommend a means to specify criticality monitoring variation through a structured argumentation approach that documents the rationale around the decisions of the law elements derivation.

The paper introduces the (ontext-ware obile gents) framework intended for developing large-scale mobile applications using the agent paradigm. provides a powerful set of abstractions, a supporting middleware and an adaptation layer allowing developers to address the main characteristics of the mobile applications: openness, asynchronous and anonymous communication, fault tolerance, and device mobility. It ensures recursive system structuring using location, scope, agent, and role abstractions. supports system fault tolerance through exception handling and structured agent coordination within nested scopes. The applicability of the framework is demonstrated using an ambient lecture scenario – the first part of an ongoing work on a series of ambient campus applications. This scenario is developed starting from a thorough definition of the traceable requirements including the fault tolerance requirements. This is followed by the design phase at which the abstractions are applied. At the implementation phase, the middleware services are used through a provided API. This work is part of the FP6 IST RODIN project on Rigorous Open Development Environment for Complex Systems.

Exception handling has a commonly agreed semantics in many programming languages. When an operation is called with inappropriate conditions, the control flow of the program is reversed back to the caller to trigger some handling mechanisms. In Multi-Agent Systems (MAS), this semantics applies to the code of agents, but it does not cover the kind of exceptions that occur at the agent level. For instance, the usual handling semantics does not address the cases where the plan of an agent fails and re-planning is required. In fact, the agent code does not necessarily encounter a programming fault or a ‘catch’ clause in such a case, but the agent has yet to deal with an exceptional situation.

In this paper, we survey the literature on exception handling with the aim to demonstrate that research needs to be conducted in the case of MAS due to their openness, heterogeneity, and the encapsulation of agents. We identify research directions from the survey, and we present a simulation scenario to illustrate the occurrence of agent-level exceptions in a simple case. The current result of the survey analysis is that agent exceptions mechanisms should rely on the proactivity of agents, on exploiting the agent environment, on collaborative handling mechanisms, and on the potential links between code-level and agent-level exceptions.

Handling erroneous conditions in context-aware mobile agent systems is challenging due to their intrinsic characteristics: openness, lack of structuring, mobility, asynchrony and increased unpredictability. Even though several context-aware middleware systems now support the development of mobile agent-based applications, they rarely provide explicit and adequate features for context-aware exception handling. This paper reports our experience in implementing error handling strategies in some prototype context-aware collaborative applications built with the MoCA (Mobile Collaboration Architecture) system. MoCA is a publish-subscribe middleware supporting the development of collaborative mobile applications by providing explicit services that empower software agents with context-awareness. We propose a novel context-aware exception handling mechanism and discuss some lessons learned during its integration in the MoCA infrastructure.

Multi-Agent Systems (MAS) are collection of loosely coupled intelligent agents. These systems operate in a distributed, highly dynamic, unpredictable and unreliable environment in order to meet their overall goals. Agents in such an environment are vulnerable to different types of run time exceptions. It is necessary to have an effective exception diagnosis and resolution mechanism in place in order to ensure reliable interactions between agents. In this paper, we propose novel exception diagnosis architecture for open MAS. The proposed architecture classifies the runtime exceptions and diagnoses the underlying causes of exceptions using a heuristic classification technique. The proposed architecture is realised in terms of specialised exception diagnosing agents known as sentinel agents. The sentinel agents act as delegates of problem solving agents and mediate interactions between them.

Mobile agent systems of the future will be used for secure information delivery and retrieval, off-line searching and purchasing, and even system software updates. As part of such applications, agent and platform integrity must be maintained, confidentiality between agents and the intended platform parties must be preserved, and accountability of agents and their platform counterparts must be stringent. SMASH, Secure Modular Mobile Agent System.H, is an agent system designed using modular components that allow agents to be easily constructed and the system to be easily extended. To facilitate security functionality, the SMASH platform incorporates existing hardware and software security solutions to provide access control, accountability, and integrity. Agents are further protected using a series of standard cryptographic functions. While SMASH promotes high assurance applications, the system also promotes an open network environment, permitting agents to move freely among the platforms and execute unprivileged actions without authenticating. In this paper, we elaborate on the components and capabilities of SMASH and present an application that benefits from each of these elements.

The i* Strategic Dependency model has been successfully employed to analyze trust relationships of networks of agents during the early stages of multiagent systems development. However, the model only supports limited trust reasoning due to its limitation to deal with the vulnerability of the depender regarding the failure of the dependency. In this paper, we introduce the concept of willingness, which provides a solution to the above problem and therefore allows a more complete analysis and reasoning of trust relationships in networks of agents.

With the introduction of large-scale open systems, the need for managing interactions between agents, and in particular for managing the entry of a new agent into an existing system, becomes an increasingly more important objective. Without such management, there may be significant implications for the performance of such systems, negating the benefits to be gained from openness. In this paper, we sketch a process by which open multi-agent systems may be , through the establishment of a system specification to be used by designers of agents that will enter the system, and by the system itself to check that an agent entering a system complies with the system constraints. While not fully detailed, the paper provides an initial model and a clear direction as to how such a system may be constructed, offering a new way of developing open multi-agent systems.

The software agent paradigm has received considerable attention recently, both in research and industrial practice. However, adoption of this software paradigm remains elusive in software engineering practice. We claim that part of the adoption problem lies with the fact that mentalistic and social concepts underlying agents are subjective and complex for the average practitioner. Specifically, although there are many efforts related to the topic coming from philosophy, cognitive sciences and computer science, a uniform and well-founded semantic view on these concepts is currently lacking. This work extends an existing upper-level ontology and offers it as a foundation for evaluating and designing agent-oriented modeling languages. In particular, the paper focuses on the concept of goal, aiming at disambiguating its definition, discussing its different manifestations, and clarifying its relation to other important agent-related concepts. For that, we examine how goals are conceived and used according to some relevant literature on agent-orientation. In addition, related work on akin fields, especially philosophy and AI are used as a basis for the proposed ontological extensions.

Agents provide developers with a flexible way to structure systems around autonomous, communicating elements. To support the efficient development of such systems, design techniques need to be introduced. In this context, we propose an extension of the UML 2.0 metamodel to support agency features and UML-based diagrams which can be used to capture four views of multi-agent systems architecture (Architectural, Intentional, Environmental and Communication). The approach also provides heuristics to guide the description of multi-agent systems according to the proposed diagrams in the context of the Tropos framework. To illustrate the approach we present an Electronic Newspaper example.