synERJY An Object-oriented Synchronous Language

The programming language synERJY is presented. It integrates object-orientation and synchronous formalisms in the spirit of Esterel, Lustre, and Statecharts.     

The Synchronous Approach to Designing Reactive Systems

Synchronous programming is available through several formally defined languages having very different characteristics: Esterel is imperative, while Lustre and Signal are declarative in style; Statecharts and Argos are graphical languages that allow one to program by constructing hierarchical automata. Our motivation for taking the synchronous design paradigm further, integrating imperative, declarative (or dataflow), and graphical programming styles, is that real systems typically have components that match each of these profiles. This paper motivates our interest in the mixed language programming of embedded software around a number of examples, and sketches the semantical foundation of the Synchronie toolset which ensures a coherent computational model. This toolset supports a design trajectory that incorporates rapid prototyping and systematic testing for early design validation, an object oriented development methodology for long term software management, and formal verification at the level of automatically generated object code.     

基于Web的生产者-消费者同步问题的实现技术

论文介绍了用Java语言实现P、V操作互斥原语的一种方法,并借此写了多个生产者和多个消费者的同步算法,以直观的图示方式演示了生产者和消费者的同步动作。     

嵌入式DSP系统中SDF模型的层次化存储优化方法

在同步数据流模型(SDF)描述的嵌入式数字信号处理(DSP)系统中,计算体单一出现调度(SAS)算法对于存在反馈环和数据密集处理的应用不可解或内存优化效果很差.文中提出了将SAS和Non-SAS类型调度算法相结合的层次化的存储优化方法,定义了数据密集分量和强连通分量来描述环和数据密集处理结构,并依据数据优先消耗原则设计了启发式的Non-SAS调度算法对分量进行存储优化.该方法适用于任意SDF模型,并有良好的存储优化效果.实验结果证明了其有效性.     

Implementation of supervisory control using extended finite-state machines

This article aims at bridging the gap between traditional designs to discrete-event control problems and supervisory control theory of Ramadge and Wonham. We propose to implement supervisory control by extending the plant's finite state machine with Boolean variables, guard formulas and updating functions. Boolean variables are used to encode the supervisor's states, event observation is captured by a set of Boolean functions that update the value of variables, and control is introduced by guarding events with Boolean formulas. The framework developed in this work is fundamental in our ongoing research on communication between supervisors in a distributed discrete-event system.     

复杂网络同步态与孤立节点解的关系

复杂网络同步是复杂系统和复杂网络的前沿研究方向之一,已经取得很大的进展. 但是对于节点以耦合矩阵左特征向量加权平均态、孤立节点的解与网络的同步态之间具有什么关系,什么是网络的同步态和同步轨等基本问题仍然缺乏深入的研究,弄清楚这些问题对于复杂网络同步的理解和应用具有重要的意义. 本文采用数学分析方法证明,如果网络同步,则加权平均态 x = j=1Njxj可以定义为同步态,一般来说,x在正极限集的意义下,也就是孤立节点方程的解. 因此在实际应用中,把孤立节点方程的解s（t） 与加权平均态x不加区别地对待是合理的. 同步态是不依赖于初始条件的通解,而同步轨是依赖于初始条件的特解. 对于混沌节点的网络,同步态应该理解为吸引子,而不是某一条轨道. 最后,本文还提供一些实例加以说明,并指出一些尚待解决的问题.     

Fail-Awareness: An Approach to Construct Fail-Safe Systems

We present a framework for building fail-safe hard real-time applications in timed asynchronous distributed systems subject to communication partitions and performance, omission, and crash failures. Most distributed systems built from commercial-off-the-shelf (COTS) processor and communication services are subject to such partitions because their COTS components do not provide hard real-time guarantees. Also custom designed systems can be subject to partitions due to unmaskable link or router failures. The basic assumption behind our approach is that each processor has a local hardware clock that proceeds within a linear envelope of real-time. This allows one to compute an upper bound on the actual delays incurred by a particular processing sequence or message transmission. Services and applications can use these computed bounds to detect when they cannot guarantee all their standard properties because of excessive delays. This allows an application to be fail-aware, that is, to detect when it cannot guarantee all its safety properties and in particular, to detect when to switch to a fail-safe mode.     

面向对象语言Smalltalk-80的并行与分布实现技术的研究

本文首先简要介绍面向对象语言Smalltalk-80系统的顺序实现技术,然后重点论述它的并发、分布及并行实现技术。     

Synchronous/Reactive Programming of Concurrent System Software

Synchronous languages are intended for programming reactive systems. Reactive systems, which include real-time systems and key operating system components, interact continually with their environment. This paper considers the applicability of imperative synchronous/reactive languages to the development of general system software, that is, to the implementation of operating system kernels, file systems, databases, networks, server architectures, device drivers, etc. The languages Esterel and Reactive C (RC) receive special attention as Esterel is the oldest and most developed such language and RC is specifically designed for compatibility with C systems programming. An alternative soft-instruction software architecture is described, which is well suited to real-world system programming. © 1997 by John Wiley & Sons, Ltd.     

ElaVM同步机制的设计与实现

系统地介绍在Linux上"和欣"虚拟机ElaVM(Elastos Virtual Machine)的同步机制的设计和实现。它为虚拟机上层的应用程序提供同步服务。提出了一种通过读写Linux的匿名管道来实现等待操作的方式,具有容易实现,可移植性好等特点。     

基于功能匹配分解的协议转换器构造技术研究

A protocol converter can solve the problem of communication between heterogeneous networks. Based on function matching partition, this paper proposes a novel approach to construct the converter, which consists of two processes and can translate messages concurrently. This technique can improve the conversion efficiency much. The illustrative examole of AR and SW protocols is also presented.     

An interpretation of typed OOP in a language with state

In this paper we give semantics toLoop, an expressive typed object-oriented programming language with updatable instance variables.Loop has a rich type system that allows for the typing of methods operating over an open-ended self type. We prove the type system given is sound;i.e., well-typed programs do not experience message not understood errors. The semantics ofLoop is given by a translation into a state-based language,Soop, that contains reference cells, records, and a form of F-bounded polymorphic type.Partially supported by NSF grant CCR-9109070Partially supported by AFOSR grant F49620-93-1-0169     

An Efficient Modular Method for the Control of Concurrent Discrete Event Systems: A Language-based Approach

In this paper, we are interested in the control of a particular class of Concurrent Discrete Event Systems defined by a collection of components that interact with each other. We investigate the computation of the supremal controllable language contained in the language of the specification. We do not adopt the decentralized approach. Instead, we have chosen to use a modular centralized approach and to perform the control on some approximations of the plant derived from the behavior of each component. The behavior of these approximations is restricted so that they respect a new language property for discrete event systems called partial controllability condition that depends on the specification. It is shown that, under some assumptions, the intersection of these “controlled approximations” corresponds to the supremal controllable language contained in the specification with respect to the plant. This computation is performed without having to build the whole plant, hence avoiding the state space explosion induced by the concurrent nature of the plant. It is finally shown that the class of specifications on which our method can be applied strictly subsumes the class of separable specifications.

Concurrency in Synchronous Systems

In this paper we introduce the notion of weak endochrony, which extends to a synchronous setting the classical theory of Mazurkiewicz traces. The notion is useful in the synthesis of correct-by-construction communication protocols for globally asynchronous, locally synchronous (GALS) systems. The independence between various computations can be exploited here to provide communication schemes that do not restrict concurrency while still guaranteeing correctness. Such communication schemes are then lighter and more flexible than their latency-insensitive or endo/isochronous counterparts. Work supported by the ARTIST and COLUMBUS IST European projects     

Graded State Machines: The Representation of Temporal Contingencies in Simple Recurrent Networks

We explore a network architecture introduced by Elman (1990) for predicting successive elements of a sequence. The network uses the pattern of activation over a set of hidden units from time-step t-1, together with element t, to predict element t + 1. When the network is trained with strings from a particular finite-state grammar, it can learn to be a perfect finite-state recognizer for the grammar. When the net has a minimal number of hidden units, patterns on the hidden units come to correspond to the nodes of the grammar; however, this correspondence is not necessary for the network to act as a perfect finite-state recognizer. Next, we provide a detailed analysis of how the network acquires its internal representations. We show that the network progressively encodes more and more temporal context by means of a probability analysis. Finally, we explore the conditions under which the network can carry information about distant sequential contingencies across intervening elements to distant elements. Such information is maintained with relative ease if it is relevant at each intermediate step; it tends to be lost when intervening elements do not depend on it. At first glance this may suggest that such networks are not relevant to natural language, in which dependencies may span indefinite distances. However, embeddings in natural language are not completely independent of earlier information. The final simulation shows that long distance sequential contingencies can be encoded by the network even if only subtle statistical properties of embedded strings depend on the early information. The network encodes long-distance dependencies by shading internal representations that are responsible for processing common embeddings in otherwise different sequences. This ability to represent simultaneously similarities and differences between several sequences relies on the graded nature of representations used by the network, which contrast with the finite states of traditional automata. For this reason, the network and other similar architectures may be called Graded State Machines.     

基于．NET平台的异步编程实现

开发人员都愿意编写同步代码的原因是简单。但是,如果电脑不能快速响应用户界面的请求,鼠标就会不停地转圈,若在界面上点两下,界面变灰,标题栏上将出现“没有响应”,然后使人束手无策。而异步编程则可使运行耗时的操作线程在后台运行,从而使开发人员在无需等待的同吼去执行其他的线程。为此,文中给出了基于.NET平台的异步编程实现方法。     

线性有限自动机的同步序列及其生成算法

文章主要讨论了线性有限自动机的同步序列,得到了线性有限自动机有同步序列的充要条件,还讨论了一类输入存贮线性有限自动机及可等价嵌入输入存贮线性有限自动机的极小线性有限自动机的同步序列。最后给出了判断线性有限自动机有无同步序列以及求线性有限自动机(最短)同步序列的一些算法。     

多传感数据同步采集系统设计

轨道检测方法涉及到陀螺仪、倾角仪、加速度计等多个传感器,如何实现多传感数据同步采集是实现轨道检测的关键技术之一.为了解决该问题,设计了一种多传感数据同步采集系统,该系统主要由正交编码采集电路、信号调理电路及同步触发电路构成,采用基于μC/OS-Ⅱ嵌入式编程方法,实现了陀螺仪、倾角仪、加速度计的同步采集.通过利用多传感数据同步采集系统设计了轨道检测小车,实验验证了该系统不仅可以精确实现多种传感器的同步采集,而且具有较强的抗干扰能力,其综合测量精度小于0.5 mm.     

取值于完备格的同步机及其最小实现化

首先给出了取值于完备格的同步机以及它的可达性、可观测性的定义,得到了取值于完备格的同步机的两个基本结论：值有限性及序引理。其次,利用值有限性质及序引理,进一步给出了取值于完备格的同步机的最小实现化问题,并证明了可达且可观测的取值于完备格的同步机就是最小实现化的同步机。