并发对象的一种描述机制

面向对象模型潜在的并发计算能力为并发程序设计提供了更高层次的解决方案。为了充分利用这种潜在的并发招行能力,必须在对象模型中显式地给出并发控制。本文给出了一种描述并发对象的机制,即：把对象的并发控制作为对象的单独属性进行描述,在定义子类时,把对象的并发描述与对象的方法分开进行继承。我们的目标是使得引进的并发机制尽量少地与对象模型的各个重要特性相冲突,减轻继承异常。另外,我们提出的并发模型允许对象内部的并发。     

基于双层类结构的继承异常处理方法

继承异常是并发面向对象语言中的一个很重要而且也是处理起来很困难的问题,它会使同步代码难以重用.为解决此问题,文章提出了一种新的双层类结构模型的方法,来解决继承异常问题,它可对同步代码的复用提供全方位的支持.     

并发面向对象模型中继承异常的一种解决方案

1 引言继承机制是面向对象软件开发中的重要设施,是实现软件复用和扩充的一种有效的语言机制,它是顺序面向对象语言的一个基本特点。但是,在将面向对象技术与并发相结合的过程中,对并发控制机制处理不当,将会引起继承机制与并发控制间的冲突问题。这种冲突主要表现在:定义子类时需要修改(重定义)父类中的所有代码才能实现自身的并发控制,从而使得子类无法继承父类的代码,产生继承异常现象、继承异常的出现将进一步破坏面向对象技术的两大优点,即:继承和封装。所以,如何有效地避免继承异常或将继承异常的产生降低到最小的程度是并发面向对象模型所要研究的一个重要问题。     

并发面向对象语言的组合同步控制模型

要将并发性与面向对象及代码重用结合起来,必须解决“继承异常”问题。目前提出的方案大都针对特定问题,有一定的局限性。本文引入了一种新的同步模型,将同步控制分为同步策略控制与同步条件控制,同时引入了策略库,加大了并发对象的代码可重用性,在很大程度上避免或减少了“继承异常”的发生。     

并发代码的继承问题

文献[1]提出了一种新的刻划并发行为的方法.本文继续讨论这种方法在面向对象的程序设计中是如何解决并发代码在继承过程中的冲突问题的.     

全复制结构下基于对象数据模型的并发控制

以全复制结构实现的同步群件系统中一个重要问题就是寻求一种能够支持人机及用户间自然、自由交互的并发控制方法,文中首先总结了以往的研究在这个问题上所取得的结果,并分析了这些结果不的不足,然后基于一种扩展的ＯＤＭＧ对象模型给出了一种全新的并发控制模型ｏｏｄＯＰＴ,该模型的主要思想是利用对象本身及其上所定义的操作的语义进行冲突解析,文中分析了不同语义对象上操作之间的冲突情况并给出了解析这些冲突的方法,以此     

多Agent协同模型在基于Web的异地同步技术中的应用

分析了多Agent协同模型在基于Web的异地同步技术中的应用.包括基于Web的多Agent协同模型、Agent的结构和功能.重点描述基于Web的多Agent通信和并发冲突的解决.最后提出了几个改进的措施.     

并发面向对象中的继承反常现象

如果不考虑继承性,并发性与对象技术的结合是很自然的.继承反常(又称继承异常)现象是继承性和并发性不相容的主要原因之一.现阶段人们对继承反常现象的认识有许多模糊之处,出发点不尽相同,形式化的工作也很少.对不同的subtyping关系考虑其特有的渐增式继承方法有利于把握继承反常现象的实质,也丰富了"在并发面向对象语言中应将inheritance层次和subtyping层次区别对待"这一认识的内涵.在阐述基本观点之后,采用范畴论的术语对相关的概念和定义做了形式化工作.一些观点和结论适用于区分和解释相关工作的出发点和贡献,并对并发面向对象技术中继承性的建模问题有所启示.     

协同设计中以实体为中心的并发操作控制机制

并发操作控制机制是协同设计中的重要问题，其实质是解决操作冲突并提供无冲突操作；而一致性、响应性和并发性是其中三个重要但互斥的需求．因此，并发操作控制机制的焦点是在保证一致性前提下，以最小响应时间和最大并发程度，解决操作冲突．文中提出了并发操作控制机制的重要设计准则，并进一步提出一种以实体为中心的并发控制机制及其形式化定义和总体实现．该机制以冲突消除取代冲突避免，通过本地操作、服务器端操作确认和复制同步三个步骤，实现松散WYSIWIS原则；其中本地操作改善响应性；服务器端操作确认最大化并发性；复制同步保证一致性．     

分布式工作流MIS系统的高级Petri网模型研究

随着信息技术的发展,分布式工作流MIS系统得到了进一步应用,以基于Web的远程计算机考试系统为例,阐述了一种基于高级Petri网姝工作流模型,并对其工作流、工作任务间的顺序、并发、冲突、同步及资源共享与竞争等关系进行了详细地分析。     

Synchronisation of heterogeneous Kuramoto oscillators with sampled information and a constant leader

The Kuramoto oscillator has been widely studied because it can model a wide variety of engineering problems. Conditions for frequency synchronisation of a network of undirected coupled Kuramoto oscillators have been well established. However, the topology that describes the interaction between oscillators may not be connected due to environmental limitations or link failures. In this work we propose a consensus-based control strategy that forces the network to follow a virtual agent with a constant frequency, and where only few agents have access to the leader state. The controller is based on the exchange of information between the oscillators through a communication network. We introduce conditions for synchronisation and phase cohesiveness with the proposed control strategy that depends on the interaction between the physical topology and the communication topology. Finally, we study two applications to illustrate concepts presented in this work: (1) frequency synchronisation in smart grids; and (2) vehicle coordination.     

Ada-I:支持保护对象继承的Ada95扩充语言

面向对象并发程序设计语言能够帮助程序员利用面向对象技术编写并发程序,从而获得面向对象技术给软件开发带来的种种好处.然而,由于继承异常现象的存在,影响了并发程序设计语言引入继承特性.Ada95语言是支持并发程序设计的面向对象语言之一,但并不支持保护对象的继承.Ada-I语言在Ada95语言的基础上进行扩充,从而支持保护对象的继承,并且避免了继承异常现象的出现.     

Cost-effective solution to synchronised audio-visual data capture using multiple sensors

Applications such as surveillance and human behaviour analysis require high-bandwidth recording from multiple cameras, as well as from other sensors. In turn, sensor fusion has increased the required accuracy of synchronisation between sensors. Using commercial off-the-shelf components may compromise quality and accuracy due to several challenges, such as dealing with the combined data rate from multiple sensors; unknown offset and rate discrepancies between independent hardware clocks; the absence of trigger inputs or -outputs in the hardware; as well as the different methods for time-stamping the recorded data. To achieve accurate synchronisation, we centralise the synchronisation task by recording all trigger- or timestamp signals with a multi-channel audio interface. For sensors that don't have an external trigger signal, we let the computer that captures the sensor data periodically generate timestamp signals from its serial port output. These signals can also be used as a common time base to synchronise multiple asynchronous audio interfaces. Furthermore, we show that a consumer PC can currently capture 8-bit video data with 1024 × 1024 spatial- and 59.1 Hz temporal resolution, from at least 14 cameras, together with 8 channels of 24-bit audio at 96 kHz. We thus improve the quality/cost ratio of multi-sensor systems data capture systems.     

面向协同虚拟维修的并发操作控制方法

在装备维修活动中,许多维修作业必须在多人协同下才能够完成．在此类虚拟维修情况下,同一对象可能同时被多名用户执行相同的操作,称之为并发操作．为高效处理并发操作带来的冲突问题,在分析以往多种并发控制方法的基础上,综合运用多种并发控制机制,提出一套有效的冲突解决方案,缩短冲突消解时间．最后,以实例的实际应用验证了方案的可行性与有效性．     

MPEG-4形式化同步描述信息的研究与设计

媒体对象内部和多个媒体对象之间的同步是多媒体研究的一个重要研究方向。简述了MPEG-4的相关概念以及体系结构,融合并扩展了诸多传统方法,提出加权有向图的形式化同步描述方法在MPEG-4体系结构中的同步层中应用,这种方法更加适应MPEG-4面向对象的内容编码和传输。通过测试结果可以看出,加权有向图的形式化同步描述方法可以有效地实现同步。     

Improved results on synchronisation of delayed complex dynamical networks via sampled-data control

This paper focuses on the synchronisation problem of delayed complex dynamical networks via sampled-data control. A novel input-delay-dependent Lyapunov–Krasovskii functional (LKF) is constructed for the first time, which can make full use of the information on the input delay. To strengthen the combinations of the vectors in the resulting augmented vector, a new zero value equality is founded. Based on the input-delay-dependent LKF and zero value equality, synchronisation criteria are established. In comparison with some existing synchronisation criteria, the criteria in this paper are less conservative. The desired sampled-data controller is designed by solving a set of linear matrix inequalities. Finally, numerical examples are given to demonstrate the superiorities of proposed results.     

A pragmatic behavior subtyping relation based on both states and actions

A behavior preserving relation between petri-net systems is introduced in this paper,based on the observability of both palces and transitions,which is important in modeling the dynamic behavior of concureent object-oriented systems with Petri nets.Each group of closely related attributes of a concurrent object is modeled by the state of a collection of observable places,and each of its methods by a group of observable transitions.The grouping distinguishes the definition in this paper from others,which makes it easy to work together with the static object models,to reuse the models and to dispel the interference among groups,thus relieving the problem of inheritance anomaly by the possibility of dividing the synchronization code into independent parts.For a formal definition of this behavior subtyping relation,Elementary Net systems,with both S-elements and T-elements labeled,are used.Then it is extended informally to the state based coloured Petri net systems.Finally,the background of the definitions and the future work are presented.