274,786 research outputs found
Agent-based Computing in Java
Agents are powerful, autonomous entities capable of performing simple, or vastly complex, operations individually or in groups of agent systems. Their capabilities extend significantly as mobile agents distributed across a network. Agent-based computing is a widely used technology with a broad range of applications, particularly in distributed computing and agent-based modeling. Many types of systems can be designed using the different architectures that define how they act, communicate, migrate, and more. This paper surveys agent-based computing, their architectures, and efforts at the standardization of certain aspects of the technology. It explores an existing framework called Jade through the lens of a demonstration based on the Sugarscape model, implemented using Jadeâs library. Finally, it presents a new framework, called NOMAD, a simple barebones framework which comprises the most essential components needed for a mobile agent framework. With it, a user can quickly and more deeply understand the vital challenges agent systems must address, such as communication and code mobility, and the solutions needed to be implemented. Theyâll be able to use the framework to extend its capabilities, create new components, and build powerful agent systems of their own
DâAgents: Security in a Multiple-Language, Mobile-Agent System
Abstract. Mobile-agent systems must address three security issues: protecting an individual machine, protecting a group of machines, and protecting an agent. In this chapter, we discuss these three issues in the context of DâAgents, a mobile-agent system whose agents can be written in Tcl, Java and Scheme. (DâAgents was formerly known as Agent Tcl.) First we discuss mechanisms existing in DâAgents for protecting an individual machine: (1) cryptographic authentication of the agentâs owner, (2) resource managers that make policy decisions based on the ownerâs identity, and (3) secure execution environments for each language that enforce the decisions of the resource managers. Then we discuss our planned market-based approach for protecting machine groups. Finally we consider several (partial) solutions for protecting an agent from a malicious machine.
Ubiquitous Computing for Mobile Environments
The increasing role and importance of ubiquitous computing and mobile environments in our daily lives implies the need for new solutions. The characteristics of agents and multi-agent systems make them very appropriate for constructing ubiquitous and mobile systems. This chapter presents some of the advances in practical and theoretical applications of multi-agent systems in the fields of ubiquitous computing and mobile environments carried out by several AgentCities.ES research groups
The shadow approach : an orphan detection protocol for mobile agents
Orphan detection in distributed systems is a well researched field for which many solutions exist. These solutions exploit well defined parent-child relationships given in distributed systems. But they are not applicable in mobile agent systems, since no similar natural relationship between agents exist. Thus new protocols have to be developed. In this paper one such protocol for controlling mobile mobile agents and for orphan detection is presented. The shadow' approach presented in this paper uses the idea of a placeholder (shadow) which is assigned by the agent system to each new agent. This defines an artificial relationship between agents and shadow. The shadow records the location of all dependent agents. Removing the root shadow implies that all dependent agents are declared orphan and are eventually terminated. We introduce agent proxies that create a path from shadow to every agent. In an extension of the basic protocol we additionally allow the shadow to be mobile. The shadow approach can be used for termination of groups of agents even if the exact location of each single agent is not known
Using mobility and exception handling to achieve mobile agents that survive server crash failures
Mobile agent technology, when designed and used effectively, can minimize bandwidth consumption and autonomously provide a snapshot of the current context of a distributed system. Protecting mobile agents from server crashes is a challenging issue, since developers normally have no control over remote servers. Server crash failures can leave replicas, instable storage, unavailable for an unknown time period. Furthermore, few systems have considered the need for using a fault tolerant protocol among a group of collaborating mobile agents. This thesis uses exception handling to protect mobile agents from server crash failures. An exception model is proposed for mobile agents and two exception handler designs are investigated. The first exists at the server that created the mobile agent and uses a timeout mechanism. The second, the mobile shadow scheme, migrates with the mobile agent and operates at the previous server visited by the mobile agent. A case study application has been developed to compare the performance of the two exception handler designs. Performance results demonstrate that although the second design is slower it offers the smaller trip time when handling a server crash. Furthermore, no modification of the server environment is necessary. This thesis shows that the mobile shadow exception handling scheme reduces complexity for a group of mobile agents to survive server crashes. The scheme deploys a replica that monitors the server occupied by the master, at each stage of the itinerary. The replica exists at the previous server visited in the itinerary. Consequently, each group member is a single fault tolerant entity with respect to server crash failures. Other schemes introduce greater complexity and performance overheads since, for each stage of the itinerary, a group of replicas is sent to servers that offer an equivalent service. In addition, future research is established for fault tolerance in groups of collaborating mobile agents
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Collective Decision-Making in Multi-Agent Systems by Implicit Leadership
Coordination within decentralized agent groups frequently requires reaching global consensus, but typical hierarchical approaches to reaching such decisions can be complex, slow, and not fault-tolerant. By contrast, recent studies have shown that in decentralized animal groups, a few individuals without privileged roles can guide the entire group to collective consensus on matters like travel direction. Inspired by these ïŹndings, we propose an implicit leadership algorithm for distributed multi-agent systems, which we prove reliably allows all agents to agree on a decision that can be determined by one or a few better-informed agents, through purely local sensing and interaction. The approach generalizes work on distributed consensus to cases where agents have different conïŹdence levels in their preferred states. We present cases where informed agents share a common goal or have conïŹicting goals, and show how the number of informed agents and their conïŹdence levels affects the consensus process. We further present an extension that allows for fast decision-making in a rapidly changing environment. Finally, we show how the framework can be applied to a diverse variety of applications, including mobile robot exploration, sensor network clock synchronization, and shape formation in modular robots.Engineering and Applied SciencesOther Research Uni
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