Giacomo Cabri

MARS: a programmable coordination architecture for mobile agents

Mobile agents offer much promise, but agent mobility and Internet openness make coordination more difficult. Mobile Agent Reactive Spaces (MARS), a Linda-like coordination architecture with programming features, can handle a heterogeneous network while still allowing simple and flexible application design.

Mobile-agent coordination models for Internet applications

Internet applications face challenges that mobile agents and the adoption of enhanced coordination models may overcome. Each year more applications shift from intranets to the Internet, and Internet-oriented applications become more popular. New design and programming paradigms call help harness the Webs potential. Traditional distributed applications assign a set of processes to a given execution environment that, acting as local-resource managers, cooperating a network-unaware fashion. In contrast, the mobile-agent paradigm defines applications as consisting of network-aware entities-agents-which can exhibit mobility by actively changing their execution environment, transferring themselves during execution. The authors propose a taxonomy of possible coordination models for mobile-agent applications, then use their taxonomy to survey and analyze resent mobile-agent coordination proposals. Their case study, which focuses on a Web-based information-retrieval application, helps show that the mobility of application components and the distribution areas breadth can create coordination problems different from those encountered in traditional distributed applications.

Reactive Tuple Spaces for Mobile Agent Coordination

The paper surveys several coordination models for mobile agent applications and outlines the advantages of uncoupled coordination models based on reactive blackboards. On this base, the paper presents the design and the implementation of the MARS system, a coordination tool for Java-based mobile agents. MARS defines Linda-like tuple spaces that can be programmed to react with specific actions to the accesses made by mobile agents.

Engineering mobile agent applications via context-dependent coordination

Mobility introduces peculiar coordination problems in agent-based Internet applications. First, it suggests the exploitation of an infrastructure based on a multiplicity of local interaction spaces. Second, it may require coordination activities to be adapted both to the characteristics of the execution environment where they occur and to the needs of the application to which the coordinating agents belong. This paper introduces the concept of context-dependent coordination based on programmable interaction spaces. On the one hand, interaction spaces associated to different execution environments may be independently programmed so as to lead to differentiated, environment-dependent, behaviors. On the other hand, agents can program the interaction spaces of the visited execution environments to obtain an application-dependent behavior of the interaction spaces themselves. Several examples show how an infrastructure for context-dependent coordination can be exploited to simplify the design of Internet applications based on mobile agents. In addition, the MARS coordination infrastructure is presented as an example of a system in which the concept of context-dependent coordination has found a clean and efficient implementation.

Supporting cooperative WWW browsing: a proxy-based approach

The paper presents a system for synchronous cooperative browsing that permits users within a workgroup to share information and cooperate toward a common goal. The system implementation is based on a Java proxy, to achieve portability without requiring modification neither to browsers nor to servers. In addition, the paper shows that the implemented system defines a general framework for interactive multi-user WWW applications.

BRAIN: A Framework for Flexible Role-Based Interactions in Multiagent Systems

Agent-based approaches in application development seem to meet the requirements of adaptability, scalability, decentralization, and flexibility imposed by complex software systems. In open applications, interactions among agents are one of the most important issues that must be faced carefully. In this paper we propose the BRAIN framework, which aims at supporting the different phases of the development of interactions in agent-based applications, relying on the concept of role to model agent interactions. Roles carry different advantages in modeling interactions and, consequently, in exploiting derived infrastructures to support multiagent systems. Besides the interaction model, the BRAIN framework includes XRole, an XML-based notation to express roles in an interoperable way, and Rolesystem, an interaction infrastructure that implements the proposed model. An application example shows the advantages of our approach in application engineering.

Tuple-based technologies for coordination

By tuple-based technologies we refer to any coordination system that uses associative access to shared dataspaces for communication / synchronization purposes.

On Self-Adaptation, Self-Expression, and Self-Awareness in Autonomic Service Component Ensembles

Software systems operating in open-ended and unpredictable environments have to become autonomic, i.e., capable of dynamically adapting their behavior in response to changing situations. To this end, key research issues include: (i) framing the schemes that can facilitate components (or ensembles of) to exhibit self-adaptive behaviors, (ii) identifying mechanisms to enable components or ensembles to self-express the most suitable adaptation scheme, and (iii) acquiring the proper degree of self-awareness to enable putting in action self-adaptation and self-expression schemes. In this position paper, with the help of a representative case study, we frame and discuss the above issues, survey the state of the art in the area, and sketch the main research challenges that will be faced in the ASCENS project towards the definition of a fully-fledged framework for autonomic services.

Agent role-based collaboration and coordination: a survey about existing approaches

The development of agent-based systems must take into account interactions, carefully modelling and engineering them. Roles represent a good concept that can help designers and developers dealing with interactions. So far, several role approaches for agents have been proposed. This paper presents a survey on the most important existing approaches. This survey evaluates the above approaches presenting their main characteristics and comparing them each other to find out how they provide support for analysis, design, implementation, interoperability and openness. Also the support for a formal notation is evaluated. This survey does not try to find out the best role approach, but to expose to designers and developers advantages and drawbacks of several approaches, so that they can recognize the conditions under which their use is preferable rather than others.

Agents for information retrieval: issues of mobility and coordination

Abstract This paper focuses on agent-based applications for information retrieval on the Web, by specifically analysing mobility and coordination issues. On the one hand, mobile agents well suit the requirements of information retrieval in the new dynamic scenario derived from the Internet. This is due to their capability of moving to the place where the information is stored – therefore saving bandwidth – and to their robustness in the presence of unreliable connections. On the other hand, the search for information by several mobile active agents calls for suitable models to rule the interactions among agents and between agents and execution environments. The paper surveys different coordination approaches and evaluates their impact in information retrieval applications based on mobile agents. The survey outlines the advantages of uncoupled coordination models and points out the suitability of a coordination model based on reactive and programmable tuple spaces: they may increase the safety and the security of the environment while simplifying the task of programming distributed mobile agent applications.