时延Petri网模拟能力研究

Petri网是一个功能强大的建模工具,然而原型Petri网的模拟能力有限,而对原型Petri网的扩充可以提高其模拟能力.时延Petri网是一种重要的含时间因素的Petri网,已广泛应用于并发系统的建模,所以对时延Petri网的模拟能力的研究就非常必要.本文首先说明时延Petri网能够满足零检验理论,然后通过模拟随机存取机来证明时延Petri网具有与图灵机相等的模拟能力.而后用时延Petri网实现对计算机经典问题的建模.     

基于Uppaal的时延Petri网到时间自动机等价模型验证*

时延Petri网和时间自动机都可以有效地对实时系统的行为进行模拟和性能分析。利用时延Petri网到时间自动机等价转换算法（简记作TPN-to-TA 转换）,将一个描述实时系统的时延Petri网模型转换成与其语义等价的一组时间自动机模型。使用时间自动机中成熟的模型验证工具Uppaal对此时延Petri网的模型进行验证。     

基于Petri网的工作流过程模型及资源分布分析

针对工作流系统的特点对时延Petri网模型进行扩展,提出了一种新的工作流建模方法,即扩展时延Petri网。给出了扩展时延Petri网的定义,并用该方法分析了工作流四种基本模型;给出了利用排队论和随机Petri网理论计算工作流模型时间性能指标的新方法,用这种方法可求得与实例到达率相关的工作流模型平均完成时间。最后应用上述方法讨论了工作流资源分布的几种模式,并与模拟结果加以对比,计算结果的最大误差在3%左右,说明基于扩展时延Petri网的方法是分析工作流系统时间性能的有效方法。     

时间Petri网模拟能力的研究

模型的模拟能力一直是系统建模方面的一个重要研究课题。本文先用一个直观的“零检验”例子说明时间Petri网的模拟能力比传统Petri网要强,并首次证明了时间Petri网与计算科学的最高模型——图灵机有相等的模拟能力;最后给出了另外一种含时间因素的时延Petri网向时间Petri网的转换方法,这说明了时间Petri网虽然形式上较为简单,但其模拟能力却并不比其它含时间因素的Petri网逊色,同时为时延Petri网的研究提供了另外一种有效方法。     

基于时延Petri网的移动电子支付协议模型

时延Petri网是在一般Petri网的基础上,在变迁上引入相应的时间函数,使其具有很强的描述能力与性能分析能力。针对移动电子支付中愈加严重的交易安全问题,通过对电子支付系统和移动电子支付流程的分析,发现移动电子商务SET协议存在漏洞,建立基于时延Petri网移动电子支付协议时延Petri网模型,为安全电子交易过程提供进一步的安全保障。     

一种随机Petri网模拟系统时延分析的新方法*

本文首先引入了时延网和闭网的概念,证明了Petri网N为时延网的充要条件是其闭网为常返网;然后,从时延网模型出发,讨论了变迁发射时间为任意分布的随机离散事件系统时延特性的求取方法,给出了时延密度的计算公式。     

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。     

基于逻辑时延Petri网的停车预订系统建模与分析

为解决逻辑Petri网不能详尽地描述模型在规定时间点变迁引发和引发完成的时间问题,提出逻辑时延Petri网.首先在普通变迁的基础上引入变迁的引发时间和变迁完成时间形成决策变迁,为每个token定义到达时间和自身时间属性等;其次重新定义引发规则和可达图算法,并针对决策变迁和可达图生成进行算法描述;最后使用逻辑时延Petri网对停车预订系统进行建模,构建可达图分析系统中重分配问题以及车位的利用率等问题.在此基础上设计实验验证了逻辑时延Petri网的可行性和智能停车预订系统的优势.     

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。     

基于时延Petri网的双重数字签名技术研究

时延Petri网是在一般Petri网的基础上,在变迁上引入相应的时间函数,使其具有很强的描述能力与性能分析能力.论文利用时延Petri网对安全电子交易的双重数字签名技术进行建模,通过对所建模型进行描述与分析,指出问题所在,找到问题的解决方案,为安全电子交易过程提供进一步的安全保障.     

一类受控Petri网的反馈控制

受控Petri网是离散事件动态系统(DEDS)的一种控制理论模型.通过模型来研究实现 禁止状态避免的最大允许反馈控制是DEDS控制理论中的一个重要课题.文中对受控Petri网 的一个子类(非受控变迁子集的外延子网为TC网)讨论控制综合问题,给出求这类受控网中实 现禁止状态避免的最大允许反馈控制的一个算法.     

Half a century after Carl Adam Petri’s Ph.D. thesis: A perspective on the field

It is certainly worth remarking on half a century of a work defining a landmark in Discrete Event Dynamic Systems (DEDS) theory. This invited contribution aims to combine some historical facts with elements of a conceptual view on concurrent DEDS, giving pointers about the development of the field. Simplifying the historical trajectory, it can be said that the seed sown by Carl Adam Petri in 1962 first grew in America (essentially until the mid 1970s), where an appropriate intellectual ambiance existed in computer science, business process management and switching systems design. Later, many other new lines of activity, including logic control and performance evaluation, flourished in Europe. Today Petri nets are widespread all over the world. The conceptual paradigm of Petri nets deals inter alia with modeling, logical analysis, performance evaluation, parametric optimization, dynamic control, diagnosis and implementation issues. In summary, multidisciplinary in themselves, formalisms belonging to the Petri nets paradigm may cover several phases of the life-cycle of complex DEDS.Given the hundreds of research and text monographs on Petri nets, together with the many thousands of theoretical and applied contributions on the subject, not to mention the ISO (International Organization for Standardization) or IEC (International Electrotechnical Commission) standards for the use of Petri nets in engineering, this work cannot hope to be a complete survey or a tutorial in the more classical sense. It is more of an impressionistic overview of the field.     

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.     

Petri网用于表示知识

本文研究了各种级别Petri网与模态逻辑之间的关系.Petri网的Enlogy是研究这些关系的基础.状况(case)和可达(Reachability)概念已经成功地用于以条件/事件(Condition/Event,简称C/E)网作知识表示.本文引用上述两个概念,使位置/变迁(Place/Transition,简称P/T)网和高级Petri网(High Level Petri Net,简称HLPN)可作知识表示.为了增强以 HLPN网作知识表示的能力,我们引用了状况变量和等价状况变量的概念.文中我们还以例子说明这些方法是可用的和有效的.     

Bounded self-stabilizing Petri nets

We investigate the property of self-stabilization in bounded Petri nets. We give characterizations for both self-stabilizing bounded ordinary Petri nets (i.e., Petri nets without multiple arcs) and self-stabilizing bounded general Petri nets (i.e., Petri nets with multiple arcs). These characterizations allow us to determine the complexity of deciding self-stabilization for each of these classes. In particular, we show the self-stabilization problem to be PTIME-complete for bounded ordinary Petri nets and PSPACE-complete for bounded general Petri nets.Louis Rosier passed away on May 6, 1991, while this paper was under review     

A characterization of the stochastic process underlying astochastic Petri net

Stochastic Petri nets (SPN's) with generally distributed firing times can model a large class of systems, but simulation is the only feasible approach for their solution. We explore a hierarchy of SPN classes where modeling power is reduced in exchange for an increasingly efficient solution. Generalized stochastic Petri nets (GSPN's), deterministic and stochastic Petri nets (DSPN's), semi-Markovian stochastic Petri nets (SM-SPN's), timed Petri nets (TPN's), and generalized timed Petri nets (GTPN's) are particular entries in our hierarchy. Additional classes of SPN's for which we show how to compute an analytical solution are obtained by the method of the embedded Markov chain (DSPN's are just one example in this class) and state discretization, which we apply not only to the continuous-time case (PH-type distributions), but also to the discrete case     

Polynomial-time algorithm for the legal firing sequences problem of a type of synchronous composition Petri nets

As far as we know, the testing problem of legal firing sequence is NP-complete for gener-al Petri net, the related results of this problem on the polynomial-time solvability are limited only to some special net classes, such as persistent Petri nets, conflict-free Petri nets and state machine Petri nets. In this paper, the language properties of synchronous composition net are discussed. Based on these results, the testing algorithm polynomial-time complexity for legal firing sequence is proposed. Therefore, net classification of polynomial-time solvability for testing legal firing sequence is extended.     

Well-structured languages

This paper introduces the notion of well-structured language. A well-structured language can be defined by a labelled well-structured transition system, equipped with an upward-closed set of accepting states. That peculiar class of transition systems has been extensively studied in the field of computer-aided verification, where it has direct an important applications. Petri nets, and their monotonic extensions (like Petri nets with non-blocking arcs or Petri nets with transfer arcs), for instance, are special subclasses of well-structured transition systems. We show that the class of well-structured languages enjoy several important closure properties. We propose several pumping lemmata that are applicable respectively to the whole class of well-structured languages and to the classes of languages recognized by Petri nets or Petri nets with non-blocking arcs. These pumping lemmata allow us to characterize the limits in the expressiveness of these classes of language. Furthermore, we exploit the pumping lemmata to strictly separate the expressive power of Petri nets, Petri nets with non-blocking arcs and Petri nets with transfer arcs.     

On the Regularity of Petri Net Languages

Petri nets are known to be useful for modeling concurrent systems. Once modeled by a Petri net, the behavior of a concurrent system can be characterized by the set of all executable transition sequences, which in turn can be viewed as a language over an alphabet of symbols corresponding to the transitions of the underlying Petri net. In this paper, we study the language issue of Petri nets from a computational complexity viewpoint. We analyze the complexity of theregularity problem(i.e., the problem of determining whether a given Petri net defines an irregular language or not) for a variety of classes of Petri nets, includingconflict-free,trap-circuit,normal,sinkless,extended trap-circuit,BPP, andgeneralPetri nets. (Extended trap-circuit Petri nets are trap-circuit Petri nets augmented with a specific type ofcircuits.) As it turns out, the complexities for these Petri net classes range from NL (nondeterministic logspace), PTIME (polynomial time), and NP (nondeterministic polynomial time), to EXPSPACE (exponential space). In the process of deriving the complexity results, we develop adecomposition approachwhich, we feel, is interesting in its own right, and might have other applications to the analysis of Petri nets as well. As a by-product, an NP upper bound of the reachability problem for the class of extended trap-circuit Petri nets (which properly contains that of trap-circuit (and hence, conflict-free) and BPP-nets, and is incomparable with that of normal and sinkless Petri nets) is derived.