实时CORBA系统调度模型的分析和比较

实时CORBA系统需要解决如何将有限的计算资源和通信资源分配给实时任务,从而保证端到端执行时间的可预测性需求的问题.为了更好地定量分析可预测性,需要为以固定优先级方式调度的、周期性任务的硬实时CORBA系统建模.文中分析了TAO系统和NraD/URI系统的调度模型以及分别由Bettati ＆ Sun提出和由东南大学提出的端到端调度模型的模型描述和调度方式.在调度模型的描述能力、计算能力、适用范围和存在的联系等方面对上述调度模型进行了分析和比较.     

实时CORBA系统调度模型的分析和比较

实时CORBA系统需要解决如何将有限的计算资源和通信资源分配给实时任务,从而保证端到端执行时间的可预测性需求的问题。为了更好地定量分析可预测性,需要为以固定优先级方式调度的、周期性任务的硬实时CORBA系统建模。文中分析了TAO系统和NraD/URI系统的调度模型以及分别由Bettati＆Sun提出和由东南大学提出的端到端调度模型的模型描述和调度方式。在调度模型的描述能力、计算能力、适用范围和存在的联系等方面对上述调度模型进行了分析和比较。     

实时CORBA规范分析与评述

实时系统是一类应用极为广泛的系统,而通用CORBA规范对实时应用支持不足,所以OMG制订了实时COR-BA1.0规范.。该规范支持固定优先级的实时CORBA应用,提供了实时CORBA应用中对象调用操作端到端的可预测性。文章对实时CORBA规范中所定义的控制和管理系统资源的策略和机制进行了较为详尽的阐述,并对其进行了分析与评述。     

端到端实时CORBA系统调度模型及其可调度性研究

实时CORBA系统中的基本问题是如何合理分配有限的计算资源和通信资源以保证各个实时任务的时间需求。该文以固定优先级方式调度的、周期性任务的硬实时系统为研究对象，提出了端到端实时CORBA系统调度模型，该模型综合考虑了客户端系统的处理、服务对象处理、网络传输等几大主要因素，而且可以描述服务对象间的嵌套调用关系，因而能全面描述实时CORBA系统中客户调用过程。在此基础上，该文基于非连续工作型同步协议，应用时间需求分析方法，研究并提出了该模型的可调度性分析算法。     

RT-CORBA的研究与应用

RT—CORBA是一种实时分布式对象计算中间件。本文介绍了TOMG制定的RT—CORBA2．0规范中的相关实时机制：处理器资源管理、Inter—ORB通信管理等RT—CORBA的资源管理,RT—CORBA端到端的可预测性,固定优先级调度和动态调度,分析了RT—CORBA的研究情况、成果及国内外几个主要的ORB产品。     

实时CORBA端到端调度的研究

当前，对实时CORBA作端到端调度分析的研究还比较少．本文在进行分析了对实时CORBA作端到端调度分析的研究基础上，提出了一种新的方法，旨在提高系统的并发程度，从而提高系统的可调度性。     

实时CORBA及其实现研究

由于普通CORBA规范对实时应用方面支持不足,OMG制订了实时CORBA规范,该规范支持优先级的实时CORBA应用,提供实时CORBA应用中对象调用操作端到端的QoS保证.概述了实时CORBA的特点,并以CORBA中的消息传递规范和实时CORBA规范为基础,提出了一个遵循实时CORBA规范的实现框架rtORB.通过实验对该框架进行了性能测试,并与TAO进行性能对比,验证了其有效性.     

嵌入式Java处理器的方法调用机制

Java语言和Java处理器在实时嵌入式系统开发中的应用受到广泛关注。传统Java虚拟机的方法调用机制采用动态装载迟解析的执行方式,使得最坏情况执行时间(WCET)难以预测。针对该问题,提出一种提前解析-微程序执行的改进方法。将传统方法调用中的符号引用转化为直接调用,以微程序的方式运行在硬件处理器上,使执行限制在可预知的时钟周期内。实验结果证明,改进方法调用机制在执行时间上满足线性关系,具备良好的WCET可预测性。     

一种具有时间语义的实时处理器模型

实时嵌入式系统是安全关键设备的计算与控制核心.为了保证系统的时间行为正确,要求其软硬件具有时序确定性和可预测性.而现代计算机系统的各个抽象层次均缺乏时间语义,无法满足硬实时安全性设计要求.针对指令集体系结构层次的基础设施缺乏时间语义的问题,尝试重新定义实时嵌入式系统的指令集和微体系结构.首先,提出一种具有时间语义的实时...     

一个实时CORBA的动态调度服务模型

在实时CORBA中引入调度服务简化了实时应用的开发,但目前实时CORBA1．0所定义的调度服务使用固定优先级调度策略只能适合于一个封闭的CORBA应用系统．本文针对这一局限性,提出了一个基于客户调度器和服务调度器相协作的动态调度服务模型对其进行扩展,使得调度服务可以适用于一个更为开放的实时CORBA系统．     

Design for Timing Predictability

A large part of safety-critical embedded systems has to satisfy hard real-time constraints. These need sound methods and tools to derive run-time guarantees that are not only reliable but also precise. The achievable precision highly depends on characteristics of the target architecture, the implementation methods and system layers of the software. Trends in hardware and software design run contrary to predictability. This article describes threats to timing predictability of systems, and proposes design principles that support timing predictability. The ultimate goal is to design performant systems with sharp upper and lower bounds on execution times.     

POA剖析及实现

对象适配器是通用对象请求代理体系结构（CORBA）的重要组成部分。概述 了CORBA中可移植的对象适配器（POA）规范，包括POA的组成、请求处理过程等；并阐述了一个POA的实现，包括POA重要组成部分以及重要流程的实现。     

Integrate software agents and CORBA in computational grid

This paper presents an Agent-based Computational Grid (ACG), which applies the concept of CORBA and agent to computational grid. The ACG system is used to implement a uniform higher level management of the computing resources and services on the Grid, and provide users with a consistent and transparent interface for accessing such services. In ACG grid, grid services are implemented by CORBA or by grid agent. Grid agents and CORBA objects will interact with each other to achieve user's service request. Our solution is the creation of a bridge between the CORBA and grid agents. The solution provides with the opportunity of considering an agent as a CORBA service and accessing CORBA services even from a grid agent. Thus, in AGC grid, existing legacy systems can be easily exploited as grid services. In this paper, firstly, the features of ACG grid are described, and then the design and implementation are given. Finally, some conclusions are given.     

Building Web services middleware with predictable execution times

Predictability of execution has seldom been considered important in the design of Web services middleware. However, with the paradigm shift brought by cloud computing and with offerings of Platforms and Infrastructure as services, execution level predictability is mandating an increased importance. Existing Web services middleware are optimised for throughput with unconditional acceptance of requests and execution in a best-effort manner. While achieving perceived levels of throughput, they also result in highly unpredictable execution times. This paper presents a generic set of guidelines, algorithms and software engineering techniques that enable service execution to complete within a given deadline. The proposed algorithms accept requests for execution based on their laxity and executes them to meet requested deadlines. An introduced admission control mechanism results in a large range of laxities, enabling more requests to be scheduled together by phasing out their execution. Specialised development libraries and operating systems empower them with increased control over execution. Two widely used Web services middleware products were enhanced using these techniques. The two systems are compared with their unmodified versions to measure the predictability gain achieved. Empirical evidence confirms that the enhancements made enable these systems to achieve more than 90% of the deadlines under any type of traffic, while the unmodified versions achieve less than 10% of the deadlines in high traffic conditions. Predictability of execution achieved through these techniques, would open up new application areas such as industrial control systems, avionics, robotics and financial trading systems to the use of Web services as a middleware platform.     

基于CORBA架构的组件负载平衡的设计与实现

由于目前OMG的CORBA规范里没有实现负载平衡．本文在CORBA标准协议的基础上扩展设计了组件负载平衡服务。客户由负载平衡服务器重定向到一台轻负载的簇集服务器上。     

Development and integration of a concurrently executing interactive user interface for the I-STAT protable clinical analyzer: A case study in real-time systems integration

A novel real-time scheduler was developed to implement an interactive user interface for an existing state-of-the-art, hand-held blood analyzer. A software-timer-based scheduler was designed and implemented and guaranteed schedulability analysis performed to ensure that all hard execution deadlines could be met at run time. An execution bandwidth preservation mechanism that increases the robustness and predictability of the scheduler is presented. The paper is a case study that describes the design and development process from a point of view that emphasizes the importance of the systems integration issues that were encountered.     

基于CORBA的中介服务器的设计与实现

在CORBA的基础上提出了中介服务器的设想,分析了中介服务器的原理、结构和实现。CORBA具有可移植性、互操作性、可复用性和可扩展性,中介服务器使CORBA具有可预测性,增强了其互操作性,减轻了网络负担。基于此结构的Web体系结构更能适应Internet的发展。     

一个基于CORBA的异构数据源集成系统的设计

提出一个基于CORBA(common object request broker architecture)的即插即用的异构多数据源集成系统的设计方案.由于采用具有较强描述能力的OIM(object model for integration)对象模型作为集成系统的公共数据模型,该系统不仅能集成各种异构数据源,包括数据库系统、文件系统、WWW上HTML文件中的数据,而且能集成随时插入的新数据源中的数据.着重讨论系统的总体结构、OIM对象模型、查询处理及界面设计.     

在基于CORBA/XML网络管理中IDL和XML数据的信息交互*

CORBA与XML结合的关键在于IDL格式和XML格式数据的交互。提出了一种基于WBEM体系结构的网络管理系统的客户端/服务器端模型,同时基于该客户端/服务器端模型提出了一种IDL和XML数据交互的方法并进行了实验实现,实验证明该方法可行。     

基于CORBA的Web机器人系统的设计与实现

：介绍了机器人远程控制的几种方案，分析了基于Web的机器人远程操作系统的基本结构，并提出了一个基于CORBA的Web机器人系统的计算模型。