Timed Petri net representation of SMIL

A multimedia server needs to satisfy the temporal relations between multimedia objects when servicing clients. We propose an enhanced timed Petri net (TPN) model to capture the information of multimedia objects along with their timing and synchronization specified in the synchronized multimedia integration language (SMIL) of XML.     

基于颜色Petri网的生产者—消费者问题建模分析

生产者—消费者问题是计算机领域一个经典的问题,经过多年的研究广泛地应用于并行系统中。现在已经利用多种技术实现了生产者—消费者问题的仿真,其中,利用Petri网对生产者—消费者问题仿真已经被证明是一种比较可行的仿真方案。文章对Petri网仿真生产者—消费者问题进行进一步优化,采用颜色Petri网对其进行仿真,并对优化后的模型与普通的模型进行了模拟运行。实验结果表明:优化后的模型与普通的Petri网模型有相近的模拟结果,说明优化后的模型可以代替原有的模型进行生产者—消费者问题的模拟,降低了系统模型的复杂度。     

基于随机Petri网模型的多DSP系统性能分析

多处理器并行处理系统在许多领域都有广泛的应用,然而由于存在系统体系结构、通信带宽和软件并行性等诸多因素的影响,往往会很大程度上制约多处理器系统性能的发挥,因此有效的评估多处理器并行处理系统的性能是系统设计阶段必不可少的任务之一。本文以ADSP14060为核心的多DSP并行处理系统的结构特征,分析了＂主从＂并行结构和＂流水线＂结构的特点;在系统结构分析的基础上,分别建立了基于广义随机Petri网的多DSP并行处理系统模型,并应用该系统模型对＂主从＂结构和＂流水线＂结构的性能进行了全面的评估,找到影响系统性能的各种因素和提高系统性能的办法。     

基于扩展Petri网的ECA规则集表示及终止性分析

为了提高ECA规则集可终止性分析的准确性,建立了一种可描述ECA规则集的扩展Petri网(EPN, extended Petri net)模型,在此基础上研究并提出了一种ECA规则集终止性判定算法。该算法充分利用EPN网所包含ECA规则特性的丰富信息,综合分析了ECA规则特性对规则集可终止性的影响。理论分析和实验结果表明,所提出的算法具有更高的准确性和更低的时间复杂度。     

基于Petri网的交通信号控制系统的建模与分析

随着物联网的发展,智能交通的应用前景广阔。文章提出一种基于Petri网建模的智能交通信号控制系统,其特点是局部控制、共同负责。交通信号控制系统基于安装在车道上的车辆检测器反馈信息,改变信号相位顺序来提高路口的道路使用率。经过仿真模拟,该模型在安全前提下能够有效减少车辆排队等候时间。     

基于Petri网动态工作流在OA系统中的应用

介绍了工作流技术,分析传统工作流模型不能根据实际情况进行动态改变的缺点,在此基础上,提出了一种支持流程动态修改的工作流,主要实现了过程模型的动态修改。针对请假流程,用Petri网建模,实现对其进行动态修改,并利用经典Petri网的遍历树算法对迁移后实例的准确性进行验证。最后展示了动态工作流的具体实现方法。     

安全信息流的实时监控机制

提出了一种基于安全自动机的信息流实时监控技术,该技术防范了恶意用户通过程序结构的缺陷窃取机密信息.监控机制使用了下推自动机,结合动态分析技术和静态分析技术,利用清除函数的原理,通过状态变换实时检测信息流的安全性.在程序执行期间,对程序事件进行抽象并跟踪信息流,用安全自动机产生的断言控制目标程序的执行,防止非法操作.用C语言实现了安全自动机,实验结果证明这种技术是灵活实用的.     

基于随机Petri网的通信网络性能评价

利用Petri网的动态描述能力,将Petri网应用到通信网动态可靠性分析上。通过分析网络故障的起因,把故障原因抽象为三个子故障系统。根据故障产生、消解的随机性,运用SPN建模,然后运算求解,得到网络可靠度的表达式。最后通过实例验证了方法的正确性。     

Necessary and sufficient conditions for deadlock-free operation inflexible manufacturing systems using a colored Petri net model

Concurrent competition for finite resources by multiple parts in flexible manufacturing systems (FMS) results in deadlock. This is an important issue to be addressed in the operation of the system. A Petri net model, called colored resource-oriented Petri net (CROPN), is developed in this paper. The concurrent resource contention and the important characteristics of the production processes necessary for deadlock control are well modeled by this model. Based on the developed model, necessary and sufficient conditions and an efficient control law are presented for deadlock-free operation in FMS. This control law is a policy of dynamic resource allocation. It determines when a resource can be allocated to which job to avoid deadlock. This control law allows as many active parts as possible to be in the system, while deadlock is totally avoided. This control law is easy to implement and can be embedded into the real-time scheduler. A simple example is used to illustrate the application of the approach     

面向对象Petri网建模技术与应用

面向对象方法使得系统设计简化,符合所描述的现实事物的特点,简单易于理解.但是在设计系统时没有进行严格的检验和验证.Petri网提供了形式化的图形表示,层次化的结构在表示类的继承以及描述对象的动态性方面非常有用.现介绍一种抽象节点技术,将面向对象设计模型转换成层次化的Petri网模型将对象和对象属性封装到数据结构中去,从而结合了两者的优点.     

Petri net approach to the analysis of a structured program

The analysis problem of complexity and execution time of a structured program has been tackled using the concept of Petri net (PN). This type of representation is useful due to its graphical and precise nature of representation scheme and also the established relationship between certain net structure and dynamic behaviour of PN can be used as a tool for analysing the behavior of the system. A PN representation of various nested blocks of the structured program is given. The firing characteristic of the transitions in a PN has been used to give an interpretation to each of the blocks and it is shown how each of the blocks can be simplified with a view to calculating the total execution time of a program. It is simple as it gives a straightforward procedure for analysing the program.     

PKI构建的安全医疗信息体系

从PKI的构成和它涉及的核心技术进行分析，提出了构建基于PKI的医疗信息体系是可行的，并对PKI构建的安全医疗信息体系进行了分析和研究。     

基于Petri网的攻击检测模式的优化生成算法

本文介绍了基于Petri网的入侵检测系统的概念,指出了这种方法所面临的主要困难是状态的组合爆炸,由此提出了通过将入侵模式Petri网和应用约束Petri网进行合成操作,从而减小无用状态的优化算法。     

Petri net models of latch metastability

Data communication between concurrent processes often employs shared latch circuitry which may display metastable transients when the processes are not synchronised. A method of deriving discrete Petri net models for such latches is proposed. The representation includes both the local onset of metastability and the effects of metastable input signals     

银行卡网上支付安全认证模式分析

前言随着电子商务近几年来的迅猛发展,电子支付已越来越成为人们普遍接受的生活方式。国内各大银行都已建立了自己的网上银行,仅2003年一年,工商银行网上银行交易额接近20万亿人民币,比上一年度增长35%;建设银行也达到1万亿人民币,比上一年度增长25%。中国银联成立以后,银行卡业务在中国飞速发展。相比邮政汇款、银行电汇,银行卡网上支付由于其高实时、便捷性,成为网上B2C业务的一种主要支付手段。国内各大厂商,如首信、21CN、润讯等都开通了银行卡网上支付,支付范围覆盖全国主要城市。网上支付的安全问题B2C网上支付是一个“四角模式”,…     

Modeling and emulation of a furnace in IC fab based oncolored-timed Petri net

In integrated circuit (IC) manufacturing, the wafer processing takes more time in furnaces than other equipment. How to effectively integrate furnaces with other automated machines is very important. In particular, using the real furnace for testing not only introduces trouble but also wastes time. This paper aims to model and construct an emulation environment for the furnace. The colored timed Petri net (CTPN) is used to model the furnace. Based on CTPN, the dynamic behaviors of the furnace, such as loading, processing, unloading and wafer count mismatching, can be emulated. The proposed CTPN model is hierarchical and modular. The hierarchical architecture is built by dividing the behaviors of the furnace to make the model more compact and the modular modeling makes the model flexible and easy to use. On the other hand, the furnace emulator provides a quasi environment for testing so that potential problems of the system can be detected in advance and the testing time can be economized     

基于SPN的军用飞机备件供应保障建模

采用随机Petri网(SPN)对军用飞机备件供应保障进行建模;并对建立的模型进行合理性分析,从分析结果可以看出:建立的模型是正确的,能够较好地对军用飞机备件供应保障进行描述。在此建立的模型可扩展性强,能用于该型飞机以及其他机型飞机的备件供应保障研究及更高层次军事系统仿真的组成部分。     

Real-time information flow analysis

In previous work, we studied some noninterference properties for information flow analysis in computer systems on classic (possibilistic) labeled transition systems. In this paper, some of these properties, notably bisimulation-based nondeducibility on compositions (BNDC), are reformulated in a real-time setting. This is done by first enhancing the security process algebra proposed by two of the authors with some extra constructs to model real-time systems (in a discrete time setting), and then by studying the natural extension of these properties in this enriched setting. We prove essentially the same results known for the untimed case: ordering relation among properties, compositionality aspects, partial model checking techniques. Finally, we illustrate the approach through two case studies, where in both cases the untimed specification is secure, while the timed specification may show up interesting timing covert channels.