多主体交互协议的表示和实现

多主体系统中,按照协议进行的交互具有显著的优点。文章首先提出一种交互协议表示方法,从协议描述和决策规则两方面来表示交互协议;然后改进主体的结构,提出一种知识层、会话控制层和通信层的三层结构,在原有主体结构中增加交互协议解释器。这种方法使得主体可以灵活地选择交互协议,同时将会话控制从知识层中分离出来,不仅使得交互更加可靠,而且减轻了主体推理的负担,简化了知识层的结构。     

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.     

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。     

基于着色网的Agent会话协议规范与会话建模

会话以及与之相关的会话协议的概念，作为用来刻画Agent之间交互的抽象机制已经研究多年。然而对这些抽象的形式化规范还没有达成共识。文中基于着色网的形式化表示，对多Agent系统中Agent之间复杂并行的会话进行建模。着色网不但可以用来描述简单的会话协议，也可以描述由简单会话协议合成的复杂会话，刻画会话的并行特征以及复杂会话运行时的状态。     

基于LOBA逻辑的言语行为表示

言语行为是多主体系统中一个有趣而重要的问题.该文从实际推理主体(practical reasoningagents)研究的角度对语用学中的言语行为进行了探讨.在多主体系统中言语行为的研究主要集中在3个方面:1)言语行为的本体描述;2)主体如何推理出合理的言语行为;3)主体如何正确处理其他主体发出的言语行为.这3个方面侧重点不同,但是相互间又紧密关联.重点讨论上述2)和3)两方面的内容,建立了一个主体认知过程的模型,并用可信主体逻辑LOBA(logic of believable agents)进行形式化表示.在主体认知过程的模型中,考虑包括主体的感知、信念、情绪、期望、目标、意图、承诺在内的各种认知成分,通过引入相应的认知动作来考虑这些认知成分之间的动态关系,并在此基础上描述主体如何产生和处理言语行为.在逻辑系统的构建上,LOBA逻辑扩展了KARO逻辑和LORA逻辑,将主体的情绪和认知动作都作为模态算子进行处理,并构建了3层语义模型以解释主体的认知动作.利用上述方法,LOBA可以在更细的粒度上来刻画主体的动态的实际推理过程.     

动力传动协同仿真平台中的主体交互协议

本文提出了一种主体交互协议的表示法,构建一个包括知识层、会话控制层、通信层的三层主体体系结构,我们在会话控制层嵌入一个协议解释程序来处理主体间的交互,这样可以使主体灵活地选择协议,减轻推论的负担,简化知识层的结构。     

MAS交互协议的形式化描述和验证

在MAS的分析与设计中,Agent间的交互协议设计是极其重要的内容.特别是交互协议的正确性、有效性和可验证性尤为关键,因此形式化描述和验证多Agent的交互协议非常有必要.定义了用于描述多Agent基于对话的交互协议的一个演算,该演算是基于进程代数的并且独立于Agent的推理过程.该机制可以实现异构多Agent系统的交互协议验证.通过Agent会话环境的状态和演算的形式语义,可以验证会话协议的一些属性,例如:终止性、是否死锁等.该方法可以有效地解决交互协议的语义验证问题,因为协议的状态和Agent的行为由协议本身定义,并且可以避免基于状态搜索的状态空间爆炸问题.     

形式化多主体系统中的交互及交互协议

深入研究了多主体系统中的交互及其协议,并用一种进程演算;即π演算进行了形式化的描述.为了研究主体之间的交互,首先对参与交互的主体的行为进行了分类,并形式化地描述了其行为规范,然后用进程定义了主体间的交互协议,并在此基础上分析了主体交互的一致性及无死锁性.     

一种基于CPN的运行时监控服务交互行为的方法

BPEL对Web服务组合的描述特性使得它很难表达和分析服务组合中的交互行为属性.这些行为属性需要遵循一定的交互协议.然而良定义的交互协议还是容易受到侵犯,这将导致服务组合进程产生状态不一致的问题.为了解决这类实际交互行为与其服务组合描述之间的不一致性问题,提出了一种由BPEL描述自动构造运行时监控器的方法.首先提出了一种基于有色Petri网(CPN)的形式化表示模型以及服务组合规约到模型的映射方法,用于精确表达从BPEL流程描述中提取的服务交互行为规约.然后,描述了由CPN形式化表示模型生成运行时监控器的方法.该运行时监控器能够捕获所有进出服务组合进程的交互消息,并且检测是否存在违背交互协议的行为.     

基于流演算的多Agent通信动作的研究

为扩展多Agent系统中Agents之间的交互特性,在流演算理论框架下研究了多Agent的通信动作.根据流演算理论和主体通信语言ACL,结合其它Agent的知识表示,引入了通信动作,给出了形式化描述,并讨论了通信动作如何影响通信双方的知识状态,并通过一个智能日程安排实例验证了上述理论,为构建适应动态.不完全可知环境下复杂的多主体系统提供了理论基础.     

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.     

To Commit or Not to Commit: Modeling Agent Conversations for Action

Conversations are sequences of messages exchanged among interacting agents. For conversations to be meaningful, agents ought to follow commonly known specifications limiting the types of messages that can be exchanged at any point in the conversation. These specifications are usually implemented using conversation policies (which are rules of inference) or conversation protocols (which are predefined conversation templates). In this article we present a semantic model for specifying conversations using conversation policies. This model is based on the principles that the negotiation and uptake of shared social commitments entail the adoption of obligations to action, which indicate the actions that agents have agreed to perform. In the same way, obligations are retracted based on the negotiation to discharge their corresponding shared social commitments. Based on these principles, conversations are specified as interaction specifications that model the ideal sequencing of agent participations negotiating the execution of actions in a joint activity. These specifications not only specify the adoption and discharge of shared commitments and obligations during an activity, but also indicate the commitments and obligations that are required (as preconditions) or that outlive a joint activity (as postconditions). We model the Contract Net Protocol as an example of the specification of conversations in a joint activity.     

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。     

Coordination Tools for MAS Development and Deployment

One of the most critical issues in the engineering of multi-agent systems (MAS) is the inadequacy of the available tools for MAS development and deployment. As we assume interaction as a first-class issue in MAS, tools are particularly required to monitor and debug inter-agents aspects, such as interaction protocols, coordination policies, social norms, and environment constraints. Since we claim that the definition of such tools is a basic research issue, in this paper we aim to identify the main requirements for development and deployment tools within an effective agent infrastructure. Focusing on agent interaction aspects, we take tuple-based coordination infrastructures--in particular the TuCSoN technology and tools--as our reference, and discuss the role of tools in a simple case study: the development and deployment of a well-known agent interaction protocol, the Contract Net.     

An authentication logic with formal semantics supportingsynchronization, revocation, and recency

Distributed systems inherently involve dynamic changes to the value of security-relevant attributes such as the goodness of encryption keys, trustworthiness of participants, and synchronization between principals. Since concurrent knowledge is usually infeasible or impractical, it is often necessary for the participants of distributed protocols to determine and act on beliefs that may not be supported by the current state of the system. Policies for determining beliefs in such situations can range from extremely conservative, such as only believing statements if they are very recent, to extremely optimistic, such as believing all statements that are not yet known to be revoked. Such security policies often are heavily dependent on timing of received messages and on synchronization between principals. We present a logic for analyzing cryptographic protocols that has the capability to specify time and synchronization details. This capability considerably advances the scope of known techniques both for expressing practical authentication policies of protocol participants as constraints and for reasoning about protocol goals subject to these constraints     

Protocol engineering for web services conversations

Although web services aim to bring about seamless and effective communication in a wide variety of Internet applications, the interactions between them are currently limited to simple request–response exchanges. However, in the longer term we believe this is unsustainable. In particular, we believe that more complex protocols for web service conversations are necessary if the participants are to tailor their needs and offers to the prevailing context and they are to coordinate multiple services in open and realistic environments. To this end, this paper combines and extends two recent web service languages, WS-Conversation Language (WSCL) and WS-Agreement, in order to obtain a method for engineering protocols of sufficient expressiveness for the next generation of flexible and autonomous services. Specifically, we propose that the protocols include speech-acts as the individual messages and we show how to model such speech-acts as WS-Agreement schemas, which can, in turn, be imported into the specification of the protocols in WSCL. To demonstrate our approach, we express a standard contracting protocol in the extended WSCL/WS-Agreement languages. Furthermore, we use statechart notation as a visual counterpart to help developers write clients that flexibly interact with a service and to help users to better understand how to interact with a service. Finally, we show that the translation between statecharts and WSCL/WS-Agreement protocols is straightforward.     

一种自顶而下的Web-服务全局行为设计方法

“Web-服务”组合的分布式本质,使得设计者们在需求说明和逻辑确认方面都遇到了新的挑战。我们先分析自底而上方法的不足,提出了一种自顶而下的设计和验证方法。该方法是用“会话协议”来描述想得到的全局行为,然后在全局会话协议上验证预设的系统目标。最后按会话协议合成各实体。     

无速度输入多智能体系统的一致性

本文研究了有无引导者的多智能体系统在非线性协议下的一致性问题.当智能体速度信息无法获知时,分别针对有无引导者的多智能体系统设计了包含辅助系统和智能体相对位移信息的非线性分布式协议.借助图论、Lyapunov稳定性理论、Barbalat引理等方法,推导出有无引导者的多智能体系统在连通无向通讯网络中实现一致的充分条件,其次,设计了一种新的能使引导–追随者多智能体系统在有向通讯网络中实现期望一致的协议.最后,数值仿真验证了结果的正确性.     

Toward A Formalism for Conversation Protocols Using Joint Intention Theory

Conversation protocols are used to achieve certain goals or to bring about certain states in the world. Therefore, one may identify the landmarks or the states that must be brought about during the goal–directed execution of a protocol. Accordingly, the landmarks, characterized by propositions that are true in the state represented by that landmark, are the most important aspect of a protocol. Families of conversation protocols can be expressed formally as partially ordered landmarks after the landmarks necessary to achieve a goal have been identified. Concrete protocols represented as joint action expressions can, then, be derived from the partially ordered landmarks and executed directly by joint intention interpreters. This approach of applying Joint Intention theory to protocols also supports flexibility in the actions used to get to landmarks, shortcutting protocol execution, automatic exception handling, and correctness criterion for protocols and protocol compositions.