Semantics of plan revision in intelligent agents

In this paper, we give an operational and denotational semantics for a meta-language of the 3APL agent programming language. With this meta-language, various 3APL interpreters can be programmed. We prove equivalence of the operational and denotational semantics. Furthermore, we give an operational semantics for object-level 3APL. Using this semantics, we relate the 3APL meta-language to object-level 3APL by providing a specific interpreter, the semantics of which will prove to be equivalent to object-level 3APL.     

Equivalence of formal semantics definition methods

There are numerous methods of formally defining the semantics of computer languages. Each method has been designed to fulfil a different purpose. For example, some have been designed to make reasoning about languages as easy as possible; others have been designed to be accessible to a large audience and some have been designed to ease implementation of languages. Given two semantics definitions of a language written using two separate semantics definition methods, we must be able to show that the two are in fact equivalent. If we cannot do this then we either have an error in one of the semantics definitions, or more seriously we have a problem with the semantics definition methods themselves.Three methods of defining the semantics of computer languages have been considered, i.e. Denotational Semantics, Structural Operational Semantics and Action Semantics. An equivalence between these three is shown for a specific example language by first defining its semantics using each of the three definition methods. The proof of the equivalence is then constructed by selecting pairs of the semantics definitions and showing that they define the same language.A full version of this paper can be accessed via our web page http://www.cs.man.ac.uk/fmethods/ facj.html     

一种基于推荐的分布式信任模型

探讨了信任的定义和基本属性,并基于推荐给出一种分布式信任模型及其实现协议,是对信任管理系统的重要补充,对于实现动态授权和构筑分布系统信任机制具有重要意义。     

开放网络环境中信任的自动建立

提出了一种基于混杂方式的通用信任模型以及在这种模型下的信任协商过程。信任协商利用信任策略对信任实体本地资源进行约束,既可以用于建立信任也可以用于获取服务。还分析了信任协商协议的复杂性,其通信开销为线性,计算开销为O(N·K)。     

Correctness of data representations involving heap data structures

While the semantics of local variables in programming languages is by now well-understood, the semantics of pointer-addressed heap variables is still an outstanding issue. In particular, the commonly assumed relational reasoning principles for data representations have not been validated in a semantic model of heap variables. In this paper, we define a parametricity semantics for a Pascal-like language with pointers and heap variables which gives such reasoning principles. It turns out that the correspondences between data representations cannot simply be relations between states, but more intricate correspondences that also need to keep track of visible locations whose pointers can be stored and leaked.     

基于H指数的网络信任管理模型

网络信任管理是通过对网络节点间的历史交易数据进行收集、分析和处理,通过建立相应的网络信任模型来提高网络的安全性。本文分析了节点信任和节点声誉的区别,给出了节点声誉的定义,并对网络中全局声誉模型进行了研究。给出了网络信任管理中基于H指数理论的全局声誉信任模型,该模型中利用网络节点的全局声誉值作为节点间是否进行交易的决策依据。     

Trust management towards service-oriented applications

In service-oriented computing (SOC) environments, service clients interact with service providers for services or transactions. From the point view of service clients, the trust status of a service provider is a critical issue to consider, particularly when the service provider is unknown to them. Typically, the trust evaluation is based on the feedback on the service quality provided by service clients. In this paper, we first present a trust management framework that is event-driven and rule-based. In this framework, trust computation is based on formulae. But rules are defined to determine which formula to use and what arguments to use, according to the event occurred during the transaction or service. In addition, we propose some trust evaluation metrics and a formula for trust computation. The formula is designed to be adaptable to different application domains by setting suitable arguments. Particularly, the proposed model addresses the incremental characteristics of trust establishment process. Furthermore, we propose a fuzzy logic based approach for determining reputation ranks that particularly differentiates new service providers and old (long-existing) ones. This is further incentive to new service providers and penalize poor quality services from service providers. Finally, a set of empirical studies has been conducted to study the properties of the proposed approaches, and the method to control the trust changes in both trust increment and decrement cases. The proposed framework is adaptable for different domains and complex trust evaluation systems.

纯函数式I/O的操作语义

目前被人们广泛采用的处理函数式Ｉ／Ｏ的机制有三种,ＭｏｎａｄＤｉａｌｏｇｕｅ,ＣＰＳ,本文采用ＣＣＳ的理论和方法,把互模拟等价作为Ｉ／Ｏ程序的相等关系,描述了这三种Ｉ／Ｏ机制的操作语义,推导出这三种Ｉ／Ｏ机制相互之间的转换关系,从而证明了这三种Ｉ／Ｏ机制在语义上是等价的。     

基于模糊聚类的信任类型动态定义机制研究

从主观信任的本质出发,提出了基于Agent的主观信任协作模型,分析了主体信任协作关系的本质;引入模糊集台理论的隶属度概念,以信任向量的形式对主观信任进行定量的描述,解决了主观信任的建模问题;结合主观信任协作模型,引入模糊聚类理论,提出了基于模糊聚类的信任类氆动态定义机制,为各主体之间的信任评估提供了依据。     

基于能量敏感的无线传感器网络信任度计算模型

由于无线传感器网络开放性、动态性等特点,导致整个网络易受攻击而极为脆弱,给传统安全机制带来严峻挑战,从而限制了无线传感器网络的发展。作为对基于密码体系的安全手段的重要补充,信任管理在解决来自网络的内部攻击,识别恶意节点、自私节点及低竞争力节点方面有着显著的优势。本文将节点的能量信息引入节点信任度计算模型中,提高了系统安全性、可靠性和公平性。通过仿真分析说明,模型以较少的资源消耗对网络的资源配置、性能、安全和通信进行统一的维护和管理,能够保证网络正常有效地运行,既缓解了WSN的管理困难,也为信任应用研究开辟了新的途径。     

一种面向Web服务的拜占庭错误容忍算法

随着Web服务的高速发展,其可靠性已经受到了越来越多的重视.针对当前拜占庭错误容忍算法对Web服务支持的不足,提出并设计了一种面向Web服务的拜占庭错误容忍算法.该算法与著名的CLBFT算法有显著区别.在Web服务中,为了支持组合服务必须对进行通信的Web服务双方都创建复制品,而CLBFT算法只在服务器方创建复制品.使用基于状态机的主动复制技术,在进行通信的Web服务双方都创建复制品.引入接收窗口和接收点对异步环境下的消息进行批量确认,同步各复制品收到消息的时间.用I/O自动机给出该算法的自动机模型,并通过遵循TPC-App Benchmark规范的实验平台实现了算法,验证了算法可行性.     

A comparison of simulation techniques and algebraic techniques for verifying concurrent systems

Simulation-based assertional techniques and process algebraic techniques are two of the major methods that have been proposed for the verification of concurrent and distributed systems. It is shown how each of these techniques can be applied to the task of verifying systems described as input/output automata; both safety and liveness properties are considered. A small but typical circuit is verified in both of these ways, first using forward simulations, an execution correspondence lemma, and a simple fairness argument, and second using deductions within the process algebra DIOA for I/O automata. An extended evaluation and comparison of the two methods is given.Supported by NSF grant CCR-89-15206, by DARPA contracts N00014-89-J-1988 and N00014-92J-4033, and by ONR contract N00014-91-J-1046.     

带有信任管理的漫游证书认证系统设计

利用漫游证书、私钥服务器和SSL协议构建了漫游证书认证系统,在客户浏览器上设计一个插件便可以使用现有的公钥基础没施PK1中的各种服务,没有VPN的复杂架构和高昂成本却可以到达到类似VPN的安全性。并在基于漫游证书认证系统的基础上增加了信任管理,解决安全系统中日益复杂的信任关系管理问题。     

Testing Self-Similar Networks

A hard problem in network testing is verifying the correctness of a class of networks, as well as the actual networks under test. In practice, at most a few networks (sometimes only one) are actually tested. Thus an important question is how to select one or more networks that are sufficiently representative to apply the results to a class of networks. We present a model-based technique for selecting a representative network. The central theorem establishes that the representative network displays any faults present in any network of the class. This paper introduces the concept of “self-similarity,” which is used to select the network, and presents the results of an experiment in testing one class of networks.     

递阶混合控制系统的分析,综合与证明

提出两类离散事件域的自动机作为控制分析与综合的中间模型，基于广义受控对象的等价事件模型，递阶型的控制器可被系统地综合。为了保证系统分析和综合的正确性，利用Ｈｏａｒｅ逻辑得到一些验证规则。最后以一级倒立摆的控制为例加以说明。     

关于I/O模拟的讨论

详细分析Windows的I/O机制,提出了分别在用户级、系统级、驱动级的FO模拟操作,通过实际案例和源代码分享在I/O模拟上的得失,着重介绍鼠标与键盘的模拟.     

基于NOW的Collective I/O技术研究

随着ＮＯＷ在科学研究中白益广泛的应用,如何为ＮＯＷ上的科学计算提供高性能的输入输出成为我们面临的一个新课题。作者根据ＮＯＷ的特点,设计并实现了一个具有ＮＯＷ特色的基于ＣｏｌｌｅｃｔｉｖｅＩ／Ｑ的并行Ｉ／Ｏ系统,吸取了ＤＤＩＯ与ｔｗｏ－ｐｈａｓｅＩ／Ｏ的优点,从而有效地解决了高带宽和低延迟问题。初步的系统吞吐量测试显示了良好的性能。     

无线传感器网络基于行为的信任体系的仿真

基于行为的信任体系是适应于无线传感器网络资源受限特性的一种安全增强机制.该体系通过节点的过往行为来评估节点的可信度,从而提高任务完成的质量.现有NS2上的WSN仿真方法往往只模拟网络中的某一个层次,不能满足该体系层次融合和网内逐跳信息处理的两个基本特点.在AD HOC仿真平台的基础上进行改动,在MAC层和网络接口层之间增加信任处理层,实现对节点完成不同类型的任务的能力进行评估.同时,对路由算法进行改进,使其选择信任度更高的节点作为路由的下一跳,从而降低不良节点对无线传感器网络中路由功能的影响.利用该文的仿真框架对基于行为的信任体系进行仿真验证,结果表明该体系的存在有效地提高了路由的成功率.