基于分布式中间件的电力监控系统设计与实现

基于对象的分布式计算技术是当今计算机软件开发的所采用的一种重要技术.与传统开发技术相比,分布式对象技术具有更好的开放性和扩展性.基于对象的中间件是分布式对象技术的良好应用.结合能量管理系统的需要,在分布式对象互操作思想的基础上,对电力监控系统中所采用的分布式中间件技术进行了设计与分析,对电力监控系统中的中间件技术的组织模式、系统流程及实现模式进行了设计,应用cORBA中间件技术对其进行了实现,并在某智能配电自动化有限公司得到了相应的应用.     

对象事务管理中间件的设计与实现

对象事务管理是分布式对象技术与TP Monitor技术相结合的产物,它集成了两者的优点,解决了目前事务处理领域面临的问题,本文主要介绍我们设计和实现的基于StarBus软总线的对象事务管理中间件StarBus-OTM,并讨论了该中间件的典型应用。     

基于CORBA-JAVA软件复用查询系统中间件技术的研究与实现

分布式对象中间件技术是为了解决分布计算和软件复用过程中存在的异构问题而提出的。CORBA，EJB，COM／DCOM是目前主要的三大中间件技术，它们都有自己的优势应用领域，CORBA和Java的结合在解决Internet www应用方面具有无比的优势，本文介绍了基于Java／CORBA的WWW信息查询系统开发的一般方法。     

关于CORBA与EJB集成模型的研究

分布式对象中间件技术是解决软件复用过程中存在的异构问题和分布式计算而提出来的,目前主要的中间件技术有:CORBA、EJB、COM等,分析了CORBA和EJB各自的优势,在此提出了CORBA和EJB结合来解决WEB应用方面更多的问题,解决两者的互访问题。     

关于CORBA与EJB集成模型的研究

分布式对象中间件技术是解决软件复用过程中存在的异构问题和分布式计算而提出来的,目前主要的中间件技术有:CORBA、EJB、COM等,分析了CORBA和EJ各自的优势,在此提出了CORBA和EJB结合来解决WEB应用方面更多的问题,解决两者的互访问题.     

基于构件的海量信息存储中间件的研究与实现

目前,中间件技术正成为构建大规模信息系统的主流技术。通过构件化一个已有的基于CORBA对象模型技术的海量数据存储中间件,构建了一个海量信息存储中间件。该中间件基于CORBA CCM技术实现,在保持原有中间件高性能,可扩展特性的同时,增强了其可管理性、可重用性和可维护性。     

多级文法在通用型中间件中的应用

在当今计算机技术发展的主流中，中间件技术是客户／服务器结构的关键技术.在对数据库专用中间件──RDA技术的深入研究后，针对它灵活性低、可扩充性差的特点，本文提出了适于构造基于通用型中间件的分布式环境的新技术──多级文法.实践证明将多级文法的技术引入中间件的构造大大提高了中间件的灵活性，增强了它的可扩充性，并使中间件本身具有了一些新的特点.目前，一个基于该多级文法的通用型中间件的原型系统已可在UNIX平台运行.     

基于XML的分布式数据交换中间件模型设计

报告了中间件技术的现状和发展趋势，分析了分布式网络应用对主流中间件设计开发的需求，讨论了异构应用系统间在降低数据交换复杂度的基础上实现透明数据交换的可能性，研究了CORBA，XML，Java等分布式信息处理及交换技术，介绍了基于XML的分布式数据交换中间件模型的设计目标、设计内容、技术路线及可行性分析，提出一个在多应用系统间交换数据的解决方案。     

分布式数据服务中间件实现技术研究

数据服务中间件的主要功能包括数据位置的透明性，分布式数据查询，事务处理，异构数据源兼容等，以数据服务中间件的实现技术为核心，详细介绍了基于DCOM／COM＋技术的分布式通用数据服务中间件的功能及开发方法，并以企业的分布式数据管理为例，介绍了本分布式数据服务中间件的应用及特点，该分布式数据服务中间件可满足企业分布式查询，分布式计算等实际应用需求。     

基于移动代理的分布式并行计算中间件设计与实现

文中提出了一个基于移动代理(Mobile Agent)的分布式并行计算中间件，用于将Internet用户闲置的计算资源与其他成员共享。针对分布式并行计算中存在的问题，利用移动代理技术的特点，将中间件的体系结构分为两层，为分布式并行计算提供各种基础服务，尤其是任务迁移和容错机制。着重介绍了分布式并行计算中间件的主要实现技术，实现了一个分布式并行计算原型系统并给出实验结果。     

A middleware for industry

This paper describes an innovative distributed framework for monitoring and control of large-scale systems by integrating heterogeneous smart objects, the world of physical devices, sensors and actuators, legacy devices and sub-systems, cooperating to support holistic management [1]. Its featured Service Oriented Architecture (SOA) exposes objects’ capabilities by means of web services, thus supporting syntactic and semantic interoperability among different technologies, including SCADA systems [23]. Wireless Sensor and Actuator Network (WSAN) devices and legacy subsystems cooperate while orchestrated by a manager in charge of enforcing a distributed logic. Particularly crafted for industrial networks are new middleware services such as dynamic spectrum management, distributed control logic, object virtualization, WSANs gateways, a SCADA gateway service, and data fusion transport capability. In addition, new application oriented objects such as shop floor, manufacturing line, welding station, robots, and cells have been introduced in the middleware. The combination of such objects and previous modules offers a new and flexible industry oriented middleware. A second contribution is in the form of traffic analysis conducted at the floor level. It shows the dominance of some end systems such as PLCs, the presence well behaved almost constant traffic made up of small packets.     

基于CORBA的消息中间件的设计与实现

在日益复杂的分布式计算环境中，中间件减少了复杂应用系统的开发和集成的难度，成为分布式计算应用的关键性部件。该文设计并实现了一个基于CORBA的消息中间件系统，提供了在异构平台中分布对象之间进行消息驱动的、透明的、异步的、基于消息内容的消息传输方法。     

Web services interaction models. Current practice

Each middleware approach has one or more interaction models associated with it that determine how applications built on top of the middleware interact with each other. Message-oriented middleware (MOM) applications interact rather simply, for example, by posting messages to and retrieving messages from queues. Object-oriented middleware applications such as those based on Corba or Enterprise Java Beans (EJB) interact by invoking methods on distributed objects. Because interaction models significantly influence the types of abstractions a middleware system makes available to applications, they figure prominently in determining the breadth and variety of application integration that the middleware supports. As Web services evolve, they too will acquire standard interaction models; otherwise, their use will be limited to small-scale proprietary systems, rather than providing the standards-based "middleware for middleware" for uniting disparate islands of integration. At this point, however, the industry and standards bodies have yet to reach consensus on Web services interaction models. I consider some of the problems associated with a popular current approach to Web services interaction models     

MobiPADS: a reflective middleware for context-aware mobile computing

Traditionally, middleware technologies, such as CORBA, Java RMI, and Microsoft's DCOM, have provided a set of distributed computing services that essentially abstract the underlying network services to a monolithic "black box." In a mobile operating environment, the fundamental assumption of middleware abstracting a unified distributed service for all types of applications operating over a static network infrastructure is no longer valid. In particular, mobile applications are not able to leverage the benefits of adaptive computing to optimize its computation based on current contextual situations. In this paper, we introduce the Mobile Platform for Actively Deployable Service (MobiPADS) system. MobiPADS is designed to support context-aware processing by providing an executing platform to enable active service deployment and reconfiguration of the service composition in response to environments of varying contexts. Unlike most mobile middleware, MobiPADS supports dynamic adaptation at both the middleware and application layers to provide flexible configuration of resources to optimize the operations of mobile applications. Within the MobiPADS system, services (known as mobilets) are configured as chained service objects to provide augmented services to the underlying mobile applications so as to alleviate the adverse conditions of a wireless environment.     

A new fuzzy-decision based load balancing system for distributed object computing

Distributed object computing systems are widely envisioned to be the desired distributed software development paradigm due to the higher modularity and the capability of handling machine and operating system heterogeneity. Indeed, enabled by the tremendous advancements in processor and networking technologies, complex operations such as object serialization and data marshaling have become very efficient, and thus, distributed object systems are being built for many different applications. However, as the system scales up (e.g., with larger number of server and client objects, and more machines), a judicious load balancing system is required to efficiently distribute the workload (e.g., the queries, messages/objects passing) among the different servers in the system. Unfortunately, in existing distributed object middleware systems, such a load balancing facility does not exist. In this paper, we present the design and implementation of a new dynamic fuzzy-decision-based load balancing system incorporated in a distributed object computing environment. Our proposed approach works by using a fuzzy logic controller which informs a client object to use the most appropriate service such that load balancing among servers is achieved. We have chosen Jini to build our experimental middleware platform, on which our proposed approach as well as other related techniques are implemented and compared. Extensive experiments are conducted to investigate the effectiveness of our fuzzy-decision-based algorithm, which is found to be consistently better than other approaches.     

基于RTI的集群计算中间件

以大运算量和大记录数据量为特征的大规模数学仿真系统，可以采用集群计算的方式实现。集群计算可分为基于单一操作系统和基于中间件两种模式。支持集群计算的中间件可以基于分布式对象实现，也可以基于HLA／RTI实现。该文分析了基于RTI的中间件（RTI Based Middleware，RBM）应能满足的基本要求，讨论了陆军师作战仿真系统中RBM的设计与实现问题。在该系统中，RBM被设计为一个接口类，全面封装了所用到的RTI服务，并为仿真应用程序提供了方便的访问接口。测试表明，RBM能够满足支持集群计算的大规模数据交互能力需求。     

Node-Capability-Aware Replica Management for Peer-to-Peer Grids

Data objects have to be replicated in large-scale distributed systems for reasons of fault tolerance, availability, and performance. Furthermore, computations may have to be scheduled on these objects, when these objects are part of a grid computation. Although replication mechanism for unstructured peer-to-peer (P2P) systems can place replicas on capable nodes, they may not be able to provide deterministic guarantees on searching. Replication mechanisms in structured P2P systems provide deterministic guarantees on searching but do not address node capability in replica placement. We propose Virat, a node-capability-aware P2P middleware for managing replicas in large-scale distributed systems. Virat uses a unique two-layered architecture that builds a structured overlay over an unstructured P2P layer, combining the advantages of both structured and unstructured P2P systems. Detailed performance comparison is made with a replication mechanism realized over OpenDHT, a state-of-the-art structured P2P system. We show that the 99th percentile response time for Virat does not exceed 600 ms, whereas for OpenDHT, it goes beyond 2000 ms in our test bed, created specifically for the aforementioned comparison.     

An energy-efficient object discovery protocol for context-sensitive middleware for ubiquitous computing

Many ubiquitous computing applications may be context-sensitive due to the ambient environments, mobile devices, and other detectable factors. A context-sensitive middleware provides the necessary support to context-sensitive application objects to participate in spontaneous and ad hoc communications with other applications in remote devices whenever suitable contexts exist. A context-sensitive middleware can provide this support effectively if its communication subsystem, such as an Object Request Broker (ORB), can properly discover other objects in devices. This capability is usually known as object discovery protocol. An energy-efficient object discovery protocol is needed to help prolong a device's battery life because many devices in ubiquitous computing environments are battery-powered and, thus, have limited energy sources. An energy-efficient object discovery protocol, RKS, for context-sensitive middleware for ubiquitous computing is presented. RKS reduces energy consumption by reducing the amount of information that needs to be sent to remote devices to discover objects. A novel feature of RKS is that it advertises its server-objects' availability only when it detects that these servers can be activated in the current context and when it finds that the neighbor devices have some potential clients that are willing to discover objects. Analytical comparisons of the energy-consumptions are given between RKS and two other protocols for object discovery in context-sensitive middleware. Furthermore, our experimental results, based on the implementations of these protocols and RKS on a context-sensitive middleware test bed, confirm our analytical results in that the RKS conserves more energy than the other two.     

Mastering the middleware muddle

For many software-development managers, staying abreast of the many new technologies that affect the systems we build is nearly impossible. One of the most complex and confusing technology areas is middleware-the cornerstone required to build enterprise-scale distributed systems. Within this esoteric technology domain, it's all too easy to hold up our hands and declare that the outlook is bleak for any kind of consensus on the direction distributed systems will take. Enterprise application integration issues, the nuances of competing middleware products from lots of vendors, and several overlapping standards activities all contribute to the confusion and uncertainty. To help us make sense of the middleware muddle, I discuss the key concepts and issues involved. To better understand recent progress in this arena, the focus is on current best practices for building enterprise-scale systems. That way, we can assess the current state of the technology and its impact on potential future strategies for distributed-systems developers. I begin by generalizing that any successful solution in enterprise-scale software engineering has four key elements: processes, infrastructure, tools, and adoption services. I briefly review current best practice in each of these four areas     

工控系统数据访问中间件的研究与设计

通过对现有OPC规范的研究。提出了在现有的各种规范之上增加“中间件层”，从而建立一种真正开放的工控系统中间件规范的建议。针对工控系统的特点和数据访问中间件的需求分析，提出了工控系统数据访问中间件的3层C/M／S（Client／Middleware／Server）体系结构，并建立了系统模型。最后阐述了数据访问中间件的设计思路，也给出了实现方案。