基于一致分布的时间Petri网模型

时间Petri网的现有分析理论主要关注基于区间端点的计算和推理,缺乏对实施区间内不确定性的定量描述,不利于时间Petri网进行系统性能评价和动态模拟实现.为了解决这一问题,提出基于一致分布的时间Petri网模型.首先给出变迁实施概率和变迁序列实施概率的计算方法;然后引入概率条件到状态类,用于构造时间Petri网的概率可达类树;最后给出动态模拟实验,检验理论方法的正确性.     

VPML过程模型到面向对象Petri网模型的映射

为了支持对企业业务流程进行建模和分析,辅助过程改进,文章提出了用VPML语言建立过程模型.然后将该过程模型映射为面向对象Petri网模型,通过对Petri网模型的定性分析和模拟仿真,其结果可用于修正和改进模型设计.     

时延Petri网分布式模拟的先行值研究

先行值计算是提高时延Petri网并行模拟性能的一个好的方法。给出了时延Petri网的先行值计算的四种基本结构,对于存在循环的复杂的Petri网结构给出了预测图算法,通过预测图,能够很容易求出静态和动态先行值,在并行模拟中利用先行值可以分析出存在并发和阻塞的结构,从而为网分块在并行机的结点上运行奠定了基础。     

UML-OOPN集成建模方法及其在柔性制造系统的应用

针对柔性制造系统FMS(Flexible manufacturing system)建模特点,提出了UML-OOPN集成建模方法。该方法是用UML(the Unified Modeling Language)建立柔性制造系统FMS(Flexible manufacturing system)模型,然后将该模型映射为面向对象Petri网OOPN(Object-Oriented Petri Nets)网模型,通过Petri网模型的分析和仿真,其结果可用于修正和改进模型设计。     

VPML OOPN集成建模方法的设计与实现*

为了支持对企业业务流程进行建模和分析,辅助过程改进,提出了VPML-OOPN集成建模方法.该建模方法是利用可视化过程建模语言VPML建立企业过程模型,然后将该过程模型映射为面向对象Petri网模型.通过Petri网模型的分析和仿真,其结果可用于修正和改进模型设计.     

着色Petri网对高性能集群的建模与性能评估

针对形式化建模方法导致的状态空间爆炸问题,提出了一种基于Petri网的高性能集群建模与性能评估方法.首先分析了高性能集群的系统架构,构建了模型的总体结构;然后针对集群系统建立了相应的任务产生子模型和调度子模型,并通过对Petri网进行着色,根据不同种类任务的执行特点设计了相应的任务处理模型.仿真结果表明,利用所建立的模型能够有效评估关键参数对集群性能的影响.     

有色Petri网协作模型的BPEL代码实现

Web服务业务流程执行语言（BPEL）提供了有力的技术来聚合封装的功能以及定义高质量的Web服务,然而,尽管功能强大,但是BPEL却难于使用。另一方面,有色Petri（CPNs）可以用于模拟、分析以及校验Web服务。为了在CPNs协作模型和业务流程的执行之间建立一座桥梁,给出了基于CPNs从过程模型驱动演绎出一致的BPEL代码的方法。首先,把CPNs协作模型转换为结构工作流网模型;然后,把工作流网模转换为BPEL代码,最后,通过电话机故障修理的案例研究,说明了算法的有效性。     

模拟实时系统的点区间优先级时间Petri网与TCTL验证

时间Petri网为实时系统提供了一种形式化的建模方法, 时间计算树逻辑(TCTL)为描述实时系统与时间相关的设计需求提供了一种逻辑化的表达方式, 因此基于时间Petri网的TCTL模型检测广泛应用于实时系统的正确性验证.然而对于一些涉及优先级的实时系统, 例如多核多任务实时系统, 这里不仅需要考虑任务之间的时间约束还要考虑任务执行的优先级以及引入优先级带来的抢占式调度问题, 致使相应的建模和分析变得更加困难.为此, 本文提出了点区间优先级时间Petri网, 通过在时间Petri网上定义变迁发生的优先级以及变迁的可挂起性, 从而可以模拟实时系统的抢占式调度机制, 即首先高优先级的任务抢占低优先级的任务所占用的资源, 导致后者被中断, 然后前者执行完毕后释放资源, 最后后者再次获得资源从中断的地方恢复.本文通过点区间优先级时间Petri网来模拟多核多任务实时系统, 使用TCTL来描述它们的设计需求, 设计了相应的模型检测算法, 开发了相应的模型检测器以验证它们的正确性.我们通过一个实例来说明我们的模型和方法的有效性.     

基于EPN的学习资源组合研究

提出基拳Petri网(EPN)的资源组合方法,用于对学习资源和组合流程进行建模和分析.首先对基于Petri网的组合方法进行综述,这些方法推动了资源组合的发展,但其所描述的资源及变迁规则不适合学习资源.为此提出了基于EPN的资源组合,以解决这一问题.改进EPN的变迁规则,把学习资源封装为Web服务,使用改进后的模型对服务进行建模,然后提出组合算法根据已知条件和变迁规则组合学习资源.最后,给出学习资源组合的实例验证方法的可行性.     

基于本体的Petri网模型转换方法

在现有的UML到Petri网模型转化规则的基础上,引入本体将其作为各种模型到Petri网模型之间转化的桥梁,研究各种模型到Petri网的通用转化方法.为每个模型包括Petri网模型建立本体,再根据基于分类树的本体映射建立模型转化步骤.通过计算不同模型中概念的相似度建立不同模型中概念的对应关系,完成模型转化.     

Using information flow analysis to detect implicit information leaks for web service composition

Information leak, which can undermine the compliance of web-service-composition business processes for some policies, is one of the major concerns in web service composition. We present an automated and effective approach for the detection of implicit information leaks in business process execution language (BPEL) based on information flow analysis. We introduce an adequate meta-model for BPEL representation based on a Petri net for transformation and analysis. Building on the concept of Petri net place-based noninterference, the core contribution of this paper is the application of a Petri net reachability graph to estimate Petri net interference and thereby to detect implicit information leaks in web service composition. In addition, a case study illustrates the application of the approach on a concrete workflow in BPEL notation.     

一种用于柔性制造系统仿真的图形Petri网软件工具

本文致力于图形Ｐｅｔｒｉ网软件工具—ＧＰＮＳＴ软件包的设计与实现。首先介绍了ＧＰＮＳＴ的结构和功能，分析了它在Ｐｅｔｒｉ网图形编辑和网结构分析方面的能力；其次正式定义了Ｐｅｔｒｉ网的扩展—赋时着色Ｐｅｔｒｉ网（ＴＣＰＮ），并且使用ＴＣＰＮ建立了柔性制造系统（ＦＭＳ）的简化仿真模型。利用这个模型，能基本实现ＦＭＳ的动态仿真，同时显示整个仿真的过程；最后将调度算法、启发式规则、ＴＣＰＮ模型和仿真结合起来，构成一个基于专家系统的调度器，产生出虽非最优，但是具有比较好结果的可行调度，有效地解决了动态仿真中的ＦＭＳ调度问题。     

基于带标记的并发可达标识图的关键路径的求解方法

将AOE 网转换成有色时延Petri网模型,在模型转换过程中同时计算出各位置所对应的事件的最早开始时间,给出了模拟AOE 网的有色时延Petri网模型的带标记的并发可达标识图的构建算法;利用并发可达标识图中的标记序列直接得到关键路径并计算出完成所有活动所需的最短时间。实例与仿真实验结果表明,当AOE网中平均存在3个以上的并发活动时,所提方法执行效率优于传统的求解关键路径的算法,并发活动越多,所提算法效率越高。     

网格计算资源调度的层次Petri网建模与分析

本文给出了网格计算资源的三层调度方案,并利用层次颜色Petri网对这一调度方案进行了建模与分析。对不同层次的资源调度建立了相应的颜色时延Petri网模型,不同层次的颜色时延Petri网模型可以有不同的行为表现,体现了网格计算资源的异构、自治等特点。给出了层次颜色Petri网的可迭任务图的概念及构造算法,并利用可达任务图,对网格计算资源调度系统的运行状态进行了分析。     

A Petri Net Approach to Support Resource Assignment in Project Management

Petri nets have long been used in modeling and simulating project execution because of their great capability to describe concurrent activities and simulate the evolvement of processes. Although a number of extended Petri net models have been proposed to model and simulate resource sharing and activity dependence in projects, none of them has ever included a resource assignment mechanism into their models. Because resource assignments influence how limited resources are allocated among conflicting activities, they may heavily affect the availability of resources and the execution of projects. Therefore, a model without considering resource-sharing and resource assignment strategies may lead to a misunderstanding about project scheduling, resource consumption behaviors, and estimated project time. Accordingly, this paper proposes a new extended Petri net model that can describe how resources are shared and assigned among concurrent activities of multiple projects. The proposed model is named as resource assignment Petri net (RAPN), which extends an object composition Petri net with new places, transitions, attributes, and firing rules to model resource-sharing and resource assignment strategies. Finally, we prove that RAPN can correctly model the resource consumption behaviors of projects and can correctly compute the total elapsed time of projects.     

Robot task plan representation by Petri nets: modelling, identification, analysis and execution

In this paper we introduce a framework to represent robot task plans based on Petri nets. Our approach enables modelling a robot task, analysing its qualitative and quantitative properties and using the Petri net representation for actual plan execution. The overall model is obtained from the composition of simple models, leading to a modular approach. Analysis is applied to a closed loop between the robot controller and the environment Petri net models. We focus here on the quantitative properties, captured by stochastic Petri net models. Furthermore, we introduce a method to identify the environment and action layer parameters of the stochastic Petri net models from real data, improving the significance of the model. The framework building blocks and a single-robot task model are detailed. Results of a case study with simulated soccer robots show the ability of the framework to provide a systematic modelling tool, and of determining, through well-known analysis methods for stochastic Petri nets, relevant properties of the task plan applied to a particular environment.     

一类资源组合问题的扩展参数Petri网建模与优化研究

现代企业重组及ＣＩＭＳ资源调度问题是一类典型资源组合优化问题。文中针对这类资源组合优化问题。提出一种新的建模方法－－扩展参数Ｐｅｔｒｉ网。该网通过着色Ｐｅｔｒｉ网和时间Ｐｅｔｒｉ网中引入扩展参数使之对任务执行过程具有很强的模型描述与性能评价能力。另外,在该网中扩展的控制决策层Ｐｅｔｒｉ网模型不仅实现了对资源组合方案选择与评价并且可以方便地与不同的优化策略与优化算法进行集成,使问题的求解更加灵活、高     

Integration of Petri nets and moment generating function approaches for system performance evaluation

This article integrates arbitrary stochastic Petri nets (ASPN) and moment generating function approaches for performance evaluation of discrete event dynamic systems (DEDS). These systems include computer-integrated manufacturing systems, resource-shared distributed systems, and communication networks. ASPN can describe various DEDS in which the time duration for activities may be a random variable of arbitrary distributions. In ASPN models, transitions with firing delays of general distributions are used to model these activities. Using our proposed performance analysis methodology, we first represent a system as an ASPN model, then generate its reachability graph and convert it into a state machine Petri net, derive the transfer functions of interesting performance measures through stepwise reductions, and finally obtain the analysis results. This method makes it possible to obtain analytical solutions of important performance indices. We use a robotic assembly system to illustrate the method. We obtain several important performance measures of a closed-form. Finally, we discuss the limitations of this approach and future research.     

State equation, controllability, and maximal matchings of petri nets

Petri nets are a versatile modeling device for studying the structure and control of concurrent systems. Petri nets and related graph models have been used for modeling a wide variety of systems from computers to social systems. In order to introduce this interesting modeling device to the researcher in control theory, this paper discusses Petri nets in the context of the state equation for a linear discrete-time system. The controllability concept of dynamic systems is applied to Petri nets for the first time. It is also shown that the controllability and reachability of a Petri net are related to maximal matchings of its bipartite graph.