连续媒体网络发布的体系结构研究

该文针对连续媒体的网络发布，研究了活跃服务的体系结构，在采用软状态协议和轻量级会话体系结构基础上，设计了一个课件访问控制协议SCACP，并研究了代理洪水抑制，访问控制带宽限制，系统容错和错误恢复，会话的分裂和重组等问题。     

一种面向图的分布Web应用架构技术

提出一种面向图的软件体系结构描述和实现技术(称为WebGOP)来支持分布Web应用系统的架构，开发者通过定义图的拓扑结构来描述体系结构，并可以根据需要定制图的类型以更好地表达特定的体系结构风格。同时，这个图实现为一个分布共享对象，显式地存在于应用系统之中，为各个构件的执行提供了一个面向图的上下文，也为体系结构的实现和动态演化提供了依托．该技术直观性强，有助于缩小体系结构描述与实现之间的距离，特别是可为系统动态重配置提供良好的支持．该文还利用edNCE图文法对WebGOP进行了形式化处理，设计实现了一个WebGOP原型系统，并对这个原型系统的关键性能指标进行了测试以表明该技术的可行性。     

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。     

并行计算在网络化控制中的机遇与挑战

先进控制中存在着大量费时的计算，这限制了它们的应用．现代控制系统正在 向着网络化方向发展，为在控制系统中实施并行计算提供了必要的环境．控制系统的网络化 从根本上导致了控制应用中计算模式的变化．在网络化控制系统中运用并行计算技术可以 提高先进控制算法的计算速度,从而提高其控制品质和扩展其应用范围．本文探讨了在当今 流行的网络控制系统体系结构上实施并行计算以解决控制应用中的计算问题的可能性以及 待解决的问题．     

基于感知控制的代理体系结构模型

提出一个基于感知控制代理的体系结构模型,旨在建模高可用的交互式软件系统.该模型通过增加新的体系结构层次来显式地建模可用性需求,以实现不同可用性特征之间的正交关系,并采用感知控制理论来匹配用户界面和应用核心之间的非线性关系.与现有的体系结构模型相比,该模型不仅使系统能够呈现用户任务层次的界面元素,而且允许用户在任务层次上对系统进行操作,从而使用户以更自然的方式控制系统来完成任务,实现目标.此外,采用该模型的系统还可以实现可用性的动态扩充.     

基于Petri网的密码协议形式化建模

密码协议是安全共享网络资源的机制和规范,是构建网络安全环境的基石,其安全性对整个网络环境的安全起着至关重要的作用。提出了采用Colored Petri Nets(CPN,着色Petri网)分析密码协议的新方法。采用新方法对TMN协议的多次并发会话通信进行形式化建模,模型依据会话配置和会话顺序进行功能单元划分,采用on-the-fly方法生成攻击路径。采用状态空间搜索技术,发现了该协议的多次并发会话不安全状态,并获得了新的攻击模式。     

分布式入侵检测系统中自保护代理的系统设计

采用分布式结构的基于网络的入侵检测系统(NIDS)自身的安全性已经成为一个重要问题。在分析了已有NIDS的技术特点的基础上，根据其特性引入了报文过滤、进程控制、报文确认和安全通信的思想，提出了面向NIDS的向保护代理(Sclf-protcction Agent)的模型，并给出了SPA的体系结构与详细设计。在与已有的基于代理的入侵检测系统结合后，SPA可以提高NIDS的安全性。     

高校办公网入侵检测系统研究

随着计算机和网络技术的发展，网络入侵事件的日益增加，人们发现只从防御的角度构造安全系统是不够的，入侵检测成为继“防火墙”、“数据加密”等传统安全保护措施后新一代的网络安全保障技术。本文首先介绍入侵检测原理和分布式入侵检测方面的相关工作．在分析已有分布式入侵检测系统模型的基础上，提出了一个基于代理的校园网入侵检测系统模型框架。该模型采用分布式的体系结构．由一个代理控制中心和若干代理组成．结合了基于网络和基于主机的入侵检测方法。使用代理技术在分布式环境下对入侵进行检测，可以有效地检测各种入侵．并具有很好的可扩充性。     

基于主动网络的Policy-control研究

结合主动网络的机制和IntServ体系结构，提出了一种主动网络支持的基于代理-管理者的策略控制机制，可以简化中间节点策略控制复杂性，保证在一个管理域中的策略一致性，并且可以实现控制策略代理的动态部署、更新。在此基础上，提出了基于发送用户的策略控制方法。     

基于本体的MAS黑板模型研究

探讨了基于本体的多智能代理黑板知识库系统(OMSBS)的体系结构及OMABS中Agent的模型、组织和交互方式。提出了一种描述混合知识类型的本体知识表达模型。本体在OMSBS中作为领域知识智能代理的知识库，是知识共享和智能代理之间通讯的基础，设计了一类调度智能代理以控制知识源智能代理的行为。OMSBS可以表达混合类型知识及其推理过程，具有良好的适应性和扩展性，呈现出开放结构。     

The Shared Control Parallel Architecture Model

SIMD machines are considered special purpose architectures chiefly because of their inability to support control parallelism. This restriction exists because there is a single control unit that is shared at the thread level; concurrent control threads must time-share the control unit (they are sequentially executed). We present an alternative model for building centralized control architectures that allows better support for control parallelism. This model, called shared control, shares the control unit(s) at the instruction level. More precisely, in each cycle the control signals for all the supported instructions are broadcast to the PEs. In turn, each PE receives its control by synchronizing with the control unit responsible for its local instruction. The shared control model is fundamentally different from the SIMD model. There are a number of architectural issues that must be resolved in order for this model to be useful. This paper identifies some of these issues and discusses their respective trade-off spaces. An integrated shared-control/SIMD architecture design (SharC) is presented and used to demonstrate the relative performance relative to a SIMD architecture.     

User-level network interface protocols

Modern high speed local area networks offer great potential for communication intensive applications, but their performance is limited by the use of traditional communication protocols, such as TCP/IP. In most cases, these protocols require that all network access be through the operating system, which adds significant overhead to both the transmission path (typically a system call and data copy) and the receive path (typically an interrupt, a system call, and a data copy). To address this performance problem, several user level communication architectures have been developed that remove the operating system from the critical communication path. The article describes six important issues to consider in designing communication protocols for user level architectures. The issues discussed focus on the performance and semantics of a communication system. These issues include data transfer, address translation, protection, and control transfer mechanisms, as well as the issues of reliability and multicast. To provide a basis for analyzing these issues, the authors present a simple network interface protocol for Myricom's Myrinet network, which has a programmable network interface. Researchers can thus explore many protocol design options, and several groups have designed communication systems for Myrinet. The authors refer to 11 such systems, all of which differ significantly in how they resolve these design issues but all of which aim for high performance and provide a lean, low level, and more or less generic communication facility     

A feedback control structure for on-line learning tasks

This paper addresses adaptive control architectures for systems that respond autonomously to changing tasks. Such systems often have many sensory and motor alternatives and behavior drawn from these produces varying quality solutions. The objective is then to ground behavior in control laws which, combined with resources, enumerate closed-loop behavioral alternatives. Use of such controllers leads to analyzable and predictable composite systems, permitting the construction of abstract behavioral models. Here, discrete event system and reinforcement learning techniques are employed to constrain the behavioral alternatives and to synthesize behavior on-line. To illustrate this, a quadruped robot learning a turning gait subject to safety and kinematic constraints is presented.     

网络化控制系统的故障诊断与容错控制

介绍了网络化控制系统几类故障诊断与容错控制方法的基本思想。故障诊断与容错控制对于控制工程实践特别是对安全性有严格要求的控制系统是十分重要的。网络化控制系统通过共享网络资源实现控制而带来了各种优越性的同时,也给传统的控制理论带来了新的挑战。因此需要发展适用于此类异步的、基于信包的控制系统的控制理论与技术。网络化控制系统基于数学模型的故障诊断问题,在建立恰当的网络化系统模型后,可转化一类特定的时延系统故障诊断问题。     

Biotope: an integrated framework for simulating distributed multiagent computational systems

The study of distributed computational systems issues, such as heterogeneity, concurrency, control, and coordination, has yielded a number of models and architectures, which aspire to provide satisfying solutions to each of the above problems. One of the most intriguing and complex classes of distributed systems are computational ecosystems, which add an "ecological" perspective to these issues and introduce the characteristic of self-organization. Extending previous research work on self-organizing communities, we have developed Biotope, which is an agent simulation framework, where each one of its members is dynamic and self-maintaining. The system provides a highly configurable interface for modeling various environments as well as the "living" or computational entities that reside in them, while it introduces a series of tools for monitoring system evolution. Classifier systems and genetic algorithms have been employed for agent learning, while the dispersal distance theory has been adopted for agent replication. The framework has been used for the development of a characteristic demonstrator, where Biotope agents are engaged in well-known vital activities-nutrition, communication, growth, death-directed toward their own self-replication, just like in natural environments. This paper presents an analytical overview of the work conducted and concludes with a methodology for simulating distributed multiagent computational systems.     

Design and analysis of a robust real-time engine control network

Increasing numbers of automotive control systems are being designed as distributed systems, with critical functions linked by electronic communications. This includes X-by-wire systems, which seek to replace mechanical or hydraulic linkages with electrical or communications links. These systems raise a number of new challenges: Safety is a function of the whole system rather than any one system feature. Thus, safety analysis and understanding must occur at the (complex) system level. A robust design process is essential to ensure that complex system issues and critical analysis occur at the right development stage and cover all appropriate parts of the system. This article provides a case study of a development project to show how these and other issues can be addressed. We describe the development of a communications network for a safety-related engine application that consists of a central electronic control unit (ECU) and a number of distributed actuators that are controlled via the network. We apply several techniques, such as hazard and scheduling analysis, to resolve safety and reliability issues     

Networked Control Systems: A Survey of Trends and Techniques

Networked control systems are spatially distributed systems in which the communication between sensors, actuators,and controllers occurs through a shared band-limited digital communication network. Several advantages of the network architectures include reduced system wiring, plug and play devices,increased system agility, and ease of system diagnosis and maintenance. Consequently, networked control is the current trend for industrial automation and has ever-increasing applications in a wide range of areas, such as smart grids, manufacturing systems,process control, automobiles, automated highway systems, and unmanned aerial vehicles. The modelling, analysis, and control of networked control systems have received considerable attention in the last two decades. The ‘control over networks’ is one of the key research directions for networked control systems. This paper aims at presenting a survey of trends and techniques in networked control systems from the perspective of ‘control over networks’, providing a snapshot of five control issues: sampled-data control, quantization control, networked control, event-triggered control, and security control. Some challenging issues are suggested to direct the future research.     

Parallel database systems: Open problems and new issues

Parallel database systems attempt to exploit recent multiprocessor computer architectures in order to build high-performance and high-availability database servers at a much lower price than equivalent mainframe computers. Although there are commercial SQL-based products, a number of open problems hamper the full exploitation of the capabilities of parallel systems. These problems touch on issues ranging from those of parallel processing to distributed database management. Furthermore, it is still an open issue to decide which of the various architectures among shared-memory, shared-disk, and shared-nothing, is best for database management under various conditions. Finally, there are new issues raised by the introduction of higher functionality such as knowledge-based or object-oriented capabilities within a parallel database system.