Agent通信语言及相关理论的研究

在多代理系统里，为了实现某一目标，Agent需要通信和交互。因此，设计一个理想的Agent通信语言就显得十分重要。Agent通信语言的实现涉及的因素，除了语言本身外，还包括Agent理论、语义、证明和会话策略等。该文就Agent通信语言和相关理论作了简单的分析并指出存在的问题。     

基于本体和会话策略的多主体交互协议描述方法

提出一种基于会话策略的多主体交互协议描述方法。交互协议中的消息用言语动作来表示,这些言语动作被描述为WS-Agreement的schema;会话策略则描述了消息传递的流程以及交互过程中的上下文信息,如参与者属性、时间阈值等等,所有这些会话策略组成了一个多主体交互协议;采用本体描述语言OWL作为会话策略的表示语言。这种方法使得主体在一个开放、动态的环境中可以灵活地选择交互协议。     

An infrastructure to support cooperation of knowledge-level agents on the semantic Grid

Can a Knowledge-Level layer be located in the Semantic Grid infrastructure? Is it possible to design an Agent Communication Language (ACL) which enables Knowledge-Level agents to cooperate in a geographically distributed Semantic Grid despite nodes’ failures or malfunctions? This paper tries to address the above Semantic Grid challenges presenting an agent-based Open Service Architecture which integrates geographically distributed agents in a Semantic Grid. The architecture is well integrated with standard Internet components and technologies and supports communication among Knowledge-Level agents. The role of agents is to retrieve, execute and compose available services providing more sophisticated instances of them. Inter-agent communication is realized by exploiting an advanced Agent Communication Language which supports a fault-tolerant anonymous interaction protocol and satisfies a set of well defined Knowledge-Level programming requirements. Here, we present the design of the architecture and of the Agent Communication Language as well as their implementation. The architecture is evaluated by means of several case studies which highlight the main feature of our proposal. The main advantage of our approach is to demonstrate that different issues, such as high level inter-agent communication and fault tolerance, can be successfully integrated in Grid infrastructures which provide Web Services maintaining a clean design of the architecture and a Knowledge-Level characterization.     

Protocol Moderators as Active Middle-Agents in Multi-Agent Systems

Interaction protocols are widely recognized as an essential mechanism for coordination within multi-agent systems. There is thus a need for coordination models for specifying, validating, and implementing protocols, possibly open and concurrent, efficiently and reliably. This paper proposes such a model, which considers protocols as resources and each conversation among agents following the rules of a protocol as a well-identified process. To this end, a new kind of middle-agent, called Moderator, is introduced. A Moderator is in charge of monitoring a conversation so that it progresses according to the protocol rules, and provides agents with services to ease their involvement in the conversation. This model fits the organization-centered view of multi-agent systems as it strictly distinguishes the agent-level and the organization-level concerns with regard to interaction. In addition, the paper shows that this model is supported by a High-Level Petri Net language that covers all the steps of protocol engineering: design, validation, implementation. This paper presents this Moderator Coordination Model along four related dimensions: a conceptual model of protocols, a MAS architecture, a suitable modeling formalism, and an associated development process.     

Crash failure detection in asynchronous agent communication languages

Agent Communication Languages (ACLs) have been developed to provide a way for agents to communicate with each other supporting cooperation in Multi-Agent Systems (MAS). In the past few years many ACLs have been proposed for MAS and new standards are emerging such as the ACL developed by the Foundation for Intelligent Physical Agents (FIPA). Despite these efforts, an important issue in the research on ACLs is still open and concerns how these languages should deal with failures of agents in asynchronous MAS. The Fault Tolerant Agent Communication Language ( - ) presented in this paper addresses this issue dealing with crash failures of agents. - provides high-level communication primitives which support a fault-tolerant anonymous interaction protocol designed for open MAS. We present a formal semantics for - and a formal specification of the underlying agent architecture. This formal framework allows us to prove that the ACL satisfies a set of well defined knowledge-level programming requirements. To illustrate the language features we show how - can be effectively used to write high-level executable specifications of fault tolerant protocols, such as the Contract Net one.     

多主体会话策略研究

用交互协议对主体之间的交互进行抽象的研究已经好多年了。然而,主体间会话的效率很低,而且会话的语义冲突问题一直没有解决。本文分析了主体之间通信协议和会话策略的关系,利用引入了本体的Dooley图描述出了主体间会话策略,并通过实验对主体选择不同的会话策略做了比较,其意义在于提高主体之间消除语义冲突的会话的效率,降低会话成本。     

一种典型MANET匿名路由协议的分析与改进

鉴于现有MANET匿名路由协议中不明确的敌手模型、未知安全性的密码学原语以及非严格的分析方法不能提供协议匿名性的信任,因此,对其中一种有代表性的匿名DSR进行了分析与改进,先从定义敌手攻击能力的角度明确敌手模型,并以数据分组与端节点不可关联性为目标定义协议的理想过程.然后,在路由发现阶段获得由UC安全的会话密钥组成的路径,在数据传输阶段用该密钥构造可验证的轻型路由洋葱.最后,在UC框架中基于理想过程证明协议的匿名性.     

移动通信环境下基于智能卡的脱线式匿名数字现金协议

本文基于Sehnorr不可抵赖签名算法提出了一个可追踪匿名的脱线式数字现金协议。它使用智能卡作为分布匿名代理，实现了数字现金的动态匿名和兑零的功能；证明数字现金是安全的且满足可追究匿名性；协议的效率比基于盲签名和匿名代理服务器的协议高，可以应用于移动环境下的匿名支付。     

多主体团队交互协议

团队是动态不可预测性环境下协作问题求解的有效方式,联合意图是团队联合求解的关键.因此,主体在团队活动中如何采用言语动作形成、维护、解除联合意图,是一个值得研究的重要问题.旨在设计一种基于主体通信语言FIPA(foundation forintelligent physical Agent)ACL(Agent communication language)的多主体团队交互协议.首先,分析了现有FIPA ACL支持团队联合求解的充分性问题.在概念上明确区分了联合请求与委托请求,指出委托请求言语动作不能充分支持团队协作.并扩展定义了联合请求,讨论了相关定理.然后,基于联合请求动作,提出一种主体团队交互协议,并给出了协议的形式化语义,最后讨论了协议的实际应用.区别于现有的基本动作请求协议、合同网协议以及拍卖协议,团队交互协议描述了另一类主体交互模式,对主体交互模块的设计具有指导意义.     

WCL: A co-ordination language for geographically distributed agents

In this paper a tuple space based co-ordination language, and a run-time system which supports it, is described. The co-ordination language is called WCL, and it is designed to support agent co-ordination over the Internet between agents which are geographically distributed. WCL uses tuple spaces as used in Linda. WCL provides a richer set of primitives than traditional tuple space based systems, and provides asynchronous and synchronous tuple space access, bulk tuple primitives, and streaming primitives which, as a whole, provide a complete framework more suited to co-ordination over the Internet compared with the Linda primitives. The primitives emphasise efficiency and location transparency (of data and agents) and this is exploited in the current run-time system used to support WCL. The run-time system described in this paper is distributed and uses location transparency and dynamic analysis of tuple space usage to migrate tuple spaces around the distributed system. Some initial experimental results are given which demonstrate the performance gains of using the tuple space migration. The paper motivates the inclusion of many of the primitives, and demonstrates how a well designed set of primitives provides performance and efficiency. The JavaSpace primitives are used as an example of how the choice of primitives can detrimentally affect the efficiency of the language, and exclude required co-ordination constructs.     

FreeWalk: a social interaction platform for group behaviour in a virtual space

FreeWalk is a social interaction platform where people and agents can socially and spatially interact with one another. FreeWalk has evolved to support heterogeneous interaction styles including meetings, cross-cultural encounters, and evacuation drills. Each of them is usually supported by an individual virtual environment. This evolution extended the capability to control social interaction. The first prototype only provides people with an environment in which they can gather to talk with one another while the third prototype provides them with a whole situation to behave according to their assigned roles and tasks. FreeWalk1 is a spatial videoconferencing system. In this system, the positions of participants make spontaneous simultaneous conversations possible. Spatial movements are integrated with video-mediated communication. FreeWalk1 is able to make social interaction more casual and relaxed than telephone-like telecommunication media. In contrast to conventional videoconferencing systems, people formed concurrent multiple groups to greet and chat with others. In FreeWalk2, a social agent acts as an in-between of people to reduce the problem of the low social context in virtual spaces. When the agent notes an awkward pause in a conversation, it approaches those involved in the conversation with a suggestion for a new topic to talk about. We used this agent to support cross-cultural communication between Japan and US. Our agent strongly influenced people's impressions of their partners, and also, their stereotypes about their partner's nationality. FreeWalk3 is a virtual city simulator to conduct virtual evacuation drills. This system brings social interaction into crisis management simulation. People can join a virtual scene of a disaster at home. Social agents can also join to play their roles assigned by simulation designers. The system architecture has a split control interface to divide control of multiple agents into high-level instruction for them and simulation of their low-level actions. The interface helps simulation designers to control many agents efficiently.     

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.     

基于卫星网络管理的SNMP扩展原语设计

针对卫星网中卫星节点的动态性和管理域动态划分的特点,提出卫星网络动态管理域划分的注册注销机制。地面分管理站向视域内的卫星发送注册广播分组,星上SNMP代理收到广播分组后采用链路延迟测试应答。根据该机制扩展了SNMP的原语,对原语的定义遵循RFC1157规范,可采用BER编码。该设计实现了SNMP协议对基于注册注销机制的动态管理域划分策略的支持。     

Agent主动目标的形式化模型

在agent结构中,主动目标是一个功能上自含且有自己独立控制流的实体.给出了主动目标相关的语法定义以及主动目标运行的操作语义,而且主动目标驱动下的BDI agent结构也被形式化地定义出来.区别于以往的一些BDI agent结构,目标不是隐含地表示而是作为实体显式地表示在agent结构中,使agent结构很自然地支持并行的目标,这被认为是agent理性行为的一个重要方面.此外,对目标的显式定义也为agent在动态的环境中对承诺的重新考虑带来了方便.     

Security in the Ajanta mobile agent system

A mobile agent is an object which can autonomously migrate in a distributed system to perform tasks on behalf of its creator. Security issues in regard to the protection of host resources, as well as the agent themselves, raise significant obstacles in practical applications of the agent paradigm. This article describes the security architecture of Ajanta, a Java‐based system for mobile agent programming. This architecture provides mechanisms to protect server resources from malicious agents, agent data from tampering by malicious servers and communication channels during its travel, and protection of name service data and the global namespace. We present here a proxy based mechanism for secure access to server resources by agents. Using Java's class loader model and thread group mechanism, isolated execution domains are created for agents at a server. An agent can contain three kinds of protected objects: read‐only objects whose tampering can be detected, encrypted objects for specific servers, and a secure append‐only log of objects. A generic authentication protocol is used for all client–server interactions when protection is required. Using this mechanism, the security model of Ajanta enforces protection of namespaces, and secure execution of control primitives such as agent recall or abort. Ajanta also supports communication between agents using RMI, which can be controlled if required by the servers' security policies. Copyright © 2001 John Wiley & Sons, Ltd.     

Applying game theory mechanisms in open agent systems with complete information

Game theory is a popular tool for designing interaction protocols for agent systems. It is currently not clear how to extend this to open agent systems. By “open” we mean that foreign agents will be free to enter and leave different systems at will. This means that agents will need to be able to work with previously unseen protocols. There does not yet exist any agreement on a standard way in which such protocols can be specified and published. Furthermore, it is not clear how an agent could be given the ability to use an arbitrary published protocol; the agent would need to be able to work out a strategy for participation. To address this we propose a machine readable language in which a game theory mechanism can be written in the form of an agent interaction protocol. This language allows the workings of the protocol to be made public so that agents can inspect it to determine its properties and hence their best strategy. Enabling agents to automatically determine the game theoretic properties of an arbitrary interaction protocol is difficult. Rather than requiring agents to find the equilibrium of a game, we propose that a recommended equilibrium will be published along with the protocol; agents can then check the recommendation to decide if it is indeed an equilibrium. We present an algorithm for this decision problem. We also develop an equilibrium which simplifies the complexity of the checking problem, while still being robust to unilateral deviations.     

THE STROBE MODEL: DYNAMIC SERVICE GENERATION ON THE GRID

This article presents the STROBE model: both an agent representation and an agent communication, model based on a social approach, which means interaction centered. This model represents how agents may realize the interactive, dynamic generation of services on the Grid. Dynamically generated services embody a new concept of service implying a collaborative creation of knowledge, i.e., learning; services are constructed interactively between agents depending on a conversation. The approach consists of integrating selected features from multi-agent systems and agent communication, language interpretation in applicative/functional programming and e-learning/human-learning into a unique, original, and simple view that privileges interactions, including control. The main characteristic of STROBE agents is that they develop a language (environment + interpreter) for each of their interlocutors. The model is inscribed within a global approach, defending a shift from the classical algorithmic (control based) view to problem solving in computing to an interaction-based view of social informatics, where artificial as well as human agents operate by communicating as well as by computing. The paper shows how the model may not only account for the classical communicating agent approaches, but also represent a fundamental advance in modeling societies of agents in particular in dynamic service generation scenarios such as those necessary today on the Web and proposed tomorrow for the Grid. Preliminary concrete experimentations illustrate the potential of the model; they are significant examples for a very wide class of computational and learning situations.     

一种基于智能卡的匿名公平移动支付系统

提出了一种基于智能卡的匿名公平移动支付系统模型,基于该模型提出了一个可追踪匿名的脱线式数字现金协议,它使用智能卡作为分布匿名代理,实现了数字现金的动态匿名和兑零的功能;证明了匿名数字现金满足安全性和可追踪匿名性,该协议的效率高于基于盲签名和匿名代理服务器技术的协议.提出了一个关于时间敏感商品的公平移动支付方案,即使用智...     

Non-linear protocols for optimal distributed consensus in networks of dynamic agents

We consider stationary consensus protocols for networks of dynamic agents with fixed topologies. At each time instant, each agent knows only its and its neighbors’ state, but must reach consensus on a group decision value that is function of all the agents’ initial state. We show that the agents can reach consensus if the value of such a function is time-invariant when computed over the agents’ state trajectories. We use this basic result to introduce a non-linear protocol design rule allowing consensus on a quite general set of values. Such a set includes, e.g., any generalized mean of order p of the agents’ initial states. As a second contribution we show that our protocol design is the solution of individual optimizations performed by the agents. This notion suggests a game theoretic interpretation of consensus problems as mechanism design problems. Under this perspective a supervisor entails the agents to reach a consensus by imposing individual objectives. We prove that such objectives can be chosen so that rational agents have a unique optimal protocol, and asymptotically reach consensus on a desired group decision value. We use a Lyapunov approach to prove that the asymptotical consensus can be reached when the communication links between nearby agents define a time-invariant undirected network. Finally we perform a simulation study concerning the vertical alignment maneuver of a team of unmanned air vehicles.