A Real-Time Object Architecture for Large Scale Distributed Systems

随着分布式系统的广泛应用，这种分布式环境中的实时计算将在各种应用中发挥重要作用，如由高速网络连接的多台计算机组成的分布式多媒体系统，高速网络连接邻近机场的大规模空中交通管制系统，以及必须控制多颗远程卫星的卫星监控系统。因此，已经做出了大量的努力来构建静态可预测的实时系统。然而，在我们瞄准的分布式环境中，网络并不总是可靠的。这种可靠性的缺乏给消息的传输带来了意外的延迟，或者造成了消息的丢失，从而使得软件在与其他节点以静态和统一的…进行通信时的时序特性分析变得困难更多的简易爆炸装置方法。此外，从全局的角度分析整个系统的行为也变得困难，因此，我们所强调的集中式实时系统的可预测性是没有意义的。需要一种用于分布式实时系统的新的编程范例。本文提出了分布式实时对象模型，作为一种新的编程模型，能够灵活地处理这种意外情况。在此基础上，设计并实现了C++的扩展语言DROL。定义在程序设计语言DROL中的分布式实时对象是一种主动对象，它封装了时间信息，支持最佳服务和最小痛苦两种策略。为了验证分布式实时对象模型的有效性和程序设计语言DROL的设计与实现，我们具体描述了DROL的编程实例和运行时性能评估结果。同时，我们还提出了一种用于定时并发系统的进程演算，并研究了它的理论性质。该演算是对Milner的CCS的扩展，引入了两个与时间相关的概念：计时操作和超时操作符。微积分的运算语义由一个标记的转换系统给出。它不仅可以描述并发系统的功能行为，还可以描述它们的各种时间属性，如定量时间、时间流逝上的时间行为和通信延迟。它享有CCS的大部分基本框架，几乎没有变化。较少

As the utility of distributed systems is widely recognized, real-time computing in such distributed environments will play an important role for various applications such as distributed multi-media systems consisting of multiple computers connected by high-speed networks, large scale air traffic control systems where high-speed networks connect neighboring airports, and satellite monitoring systems that have to control multiple remote satellites.Most of previously proposed real-time programming languages has been designed to describe centralized real-time systems. Thus, a great deal of effort has been made to construct statically predictable real-time systems. However, in distributed environments at which we aim, networks are not always reliable. This lack of reliability brings unexpected delay to message transmissions, or causes the loss of messages.Consequently, it makes difficult to analyze timing characteristics of software which communicates with other nodes with a static and unif … More ied method. Moreover, it also becomes difficult to analyze whole of system's behavior from a global view point.Thus, the predictability on which in the category of the centralized real-time systems we have laid stress is meaningless. A new programming paradigm for distributed real-time systems is needed. This dissertation proposes the Distributed Real-time Object model, as a new programming model that can flexibly deal with such unexpected situations. Then, a programming language DROL that is an extension of C++ is designed and Implemented. A distributed real-time object defined in the programming language DROL is an active object which encapsulates timing information and supports two strategies, best service and least suffering.In order to demonstrate the effectiveness of the distributed real-time object model and the design and implementation of the programming language DROL,we describe programming examples of DROL and evaluation results of runtime performance concretely.We also present a process calculus for timed concurrent systems and study its theoretical properties. The calculus is an extension of Milner's CCS by introducing two timed related notion : a tick action and a timeout operator. The operational semantics of the calculus is given by a labelled transition system. It allows to describe not only the functional behavior of concurrent systems but also variant time properties of them, such as quantitative time, timed behavior on the passage of time, and communication delay. It enjoys most of the fundamental framework of CCS almost unchanged. Less