On Supervisory Policies that Enforce Global Fairness and Bounded Fairness in Partially Controlled Petri Nets

In this paper we consider the notions of global-fairness (G-fairness) and bounded-fairness (B-fairness) for arbitrary Petri nets (PNs). G-fairness in a PN guarantees every transition occurs infinitely often in every valid firing sequence of infinite length. B-fairness guarantees a bound on the number of times a transition in the PN can fire without some transition firing at least once. These properties are guaranteed without recourse to assumptions on firing time distributions or contention resolution policies. We present a necessary and sufficient condition for the existence of supervisory policies that enforce G-fairness and B-fairness along with various observations on the closure properties of policies that enforce these notions of fairness in controlled PNs with a (possibly) non-empty set of uncontrollable transitions. We also derive a necessary and sufficient condition that guarantees a minimally restrictive supervisor that enforces these notions of fairness for bounded PNs. These results are illustrated via examples.     

Petri网共享T型子网合成公平性分析

共享T-型子网合成是研究复杂Petri网系统性质的一个有效途径.本文研究了共享T-型子网合成对参与合成的各网系统的公平性的继承关系,给出了合成网保持公平性的充分条件.随后给出的有关制造系统设计的举例,说明了该合成方法的有效性.本文的结果可为Petri网系统合成性质的考察提供有效途径.     

Petri网弱公平性和公平性关系的进一步研究

在Petri网中,公平性概念的引入是为了讨论网系统中两个变迁发生之间的相互关系。这种关系可以很好地反映出模拟系统的各个事件在资源竞争中的有无饥饿性问题。文中基于弱公平性和公平性的定义与联系,证明了对于有界Petri网,满足弱公平性就满足公平性;同时证明了在两类无界Petri网中,可由弱公平性推导出公平性。并进一步证明其他类型的无界Petri网是不满足公平性的,即无法从弱公平性直接推导出公平性。     

Petri网的TT型子网精细化操作性质分析及其应用

针对企业用加工厂或车间加工某种产品等这一类业务处理问题，提出了用Petri网精细化操作解决问题的方案。定义了一种TT-型子网，用这种子网分别对Petri网系统中的某些变迁进行细化，得到更细致、更精确的Petri网系统。研究了Petri网精细化操作的动态性质保持问题，给出这种精细化操作保持活性、有界性、可回复性和公平性的充要条件；本文的结果可为Petri网系统静态和动态性质的考察提供有效途径，为Petri网复杂大系统的分析提供重要手段，并特别适合于一类业务系统的描述和处理，具有一定的实用价值。     

Petri网的PP型子网精细化操作性质分析及应用

针对工厂用车间中的若干台机器加工某些部件等这一类业务处理问题,提出了用Petri网精细化操作解决问题的方案。定义了一种PP型子网,用这种子网分别对Petri网系统中的某些库所进行细化,得到更细致、更精确的Petri网系统。研究了Petri网精细化操作的动态性质保持问题,给出这种精细化操作保持活性、有界性、可回复性和公平性的充要条件;本文的结果可为Petri网系统静态和动态性质的考察提供有效途径,为Petri网复杂大系统的分析提供重要手段,并特别适合于一类业务系统的描述和处理,具有一定的实用价值。     

Petri网共享T型子网合成结构性质分析及其应用

为了解决系统设计中的子系统共享问题,提出了经由Petri网共享T-型子网构成共享T-型子网合成网的解决方案;研究了共享T-型子网合成网的结构性质,提出了共享T-型子网合成网保持结构有界性、守恒性、可重复性、相容性、P-不变量、T-不变量、公平性和结构活性的充分条件或充要条件;特别在证明结构活性保持性的过程中,体现了Petri网层次化的描述方法。本文的结果可为Petri网系统合成性质的考察提供有效途径,为复杂大系统的分析提供重要手段,并特别适合于一类系统的设计和分析,具有一定的实用价值。     

基于随机对象Petri网的柔性制造系统性能分析

为了增强传统对象Petri网的定量分析能力,提出随机对象Petri网模型。该模型具备随机性和层次特性,获得与随机Petri网的等价关系,从宏观和微观2个层面对系统进行性能分析,并将该模型应用到柔性制造系统中。实验结果表明,该系统保留了面向对象的建模能力,具有较强的定量分析能力。     

主动网络中CPU和带宽资源分配的公平性

传统的包调度方案能实现单一资源分配的公平性,但不能直接应用于主动网络中的主动节点上,因为主动节点包含多种相互关联的资源。提出一种能实现在主动节点中公平分配资源的包调度算法。仿真实验结果显示,该算法能在主动流之间实现CPU和带宽资源的有效公平分配。     

Tutorial and Survey Articles: An introduction to Petri Nets

This paper describes the fundamental concepts and characteristics of Petri nets (PNs) that make them a significant tool for modeling and analyzing asynchronous systems with concurrent and parallel activities and follows the extensions that improved the implementation capabilities of the original PNs.

Their first and most relevant extension was time modeling, a vital aspect of system performances not considered in the original version. There are several possibilities for introducing time in PNs. Among them, a technique that associates time with places is presented in some detail. As PNs tend to become cumbersome and time consuming when large and complex systems are involved, a method for decomposing timed PNs of open queuing networks is reviewed here.

Though initially developed as an information/computer-based technique, PNs were immediately adopted in a variety of application areas, such as manufacturing, design, planning and control. Viewed through a more recently developed programming perspective, the ordinary PNs became “high level” PNs suitable for defining different data types and for applying hierarchical approaches.

It is expected that the robust theoretical basis of this tool coupled with its visual and flexibility features will continue to appeal to researchers and practitioners alike in a variety of domains and as a result will continue to evolve and expand.     

基于跳数的公平性增强RED及其分类器实现

为了同时兼顾改善不同往返时延(RTT)和多拥塞链路所引发的不公平性问题,在实际网络环境测量结果的基础上,提出了利用数据包所经过的路由器跳数来增强公平性的思路,并构造了一个二维两类分类器来对REI)算法进行简单的修改,实现了一个公平性增强的REI)算法。NS2下的模拟表明,该算法可有效增强公平性,而且具有实现简单、易于在实际网络中部署的优点。     

基于平行Petri网的制造系统调度与控制一体化方法

为了消除制造系统调度层与控制层之间的隔阂, 实现对生产事件快速灵活响应, 本文提出了一种调度与控制一体化的方法. 首先, 定义了一种新型Petri网模型, 即平行Petri网, 从而集成地描述了传感器、执行器、任务和资源信息, 构建制造系统的信息物理系统模型; 其次, 提出了一种从平行Petri网到赋时Petri网的抽象简化方法, 大规模压缩优化调度所需搜索的状态空间; 再次, 定义了策略Petri网以描述最优调度策略. 最后, 给出了平行Petri网与策略Petri网同步执行算法, 使得平行Petri网与物理系统同步执行.     

调度问题的HPN模型研究

本文介绍了层次Ｐｅｔｒｉ网模型（ＨＰＮ）的概念。层次Ｐｅｔｒｉ网的特点在于它不仅可以在某一层次上模拟系统的局部行为，而且还可以通过一定的关联机制来表现系统的整体特性。本文还通过研究调度问题的ＨＰＮ模型，探讨了如何应用ＨＰＮ来分析调度问题，为进一步研究调试方法提供了基础。     

Petri网展开图法的分析和应用

Petri网的展开图是一种特殊的并发系统状态空间搜索方法，它不需要重复考虑并发事件的所有可能的交集，从而大大缩减状态空间爆炸给验证分析带来的空间复杂度和时间复杂度。使用展开图分析Petri网的行为属性与传统的Petri网分析方法相比，具有自己的特点。该文首先介绍了Petri网展开图的构造算法，在此基础上使用展开图分析方法对一个典型Petri网的活性，有界性和可逆性等行为属性进行了分析，并与传统的Petri网分析方法作比较。     

TCPN的状态可达及可调度决策空间算法

Ｔｓａｉ等提出了时间限制Ｐｅｔｒｉ，并讨论了变迁可激活，可调度规律及其计算公式。然而，由于网拓扑和动态的复杂性，某些概念的逻辑关系及公式有矛盾。本文通过引入调度决策变量，动态标记准确地刻画调度规律，修正澄清了Ｔｓａｉ文中的问题，完善了ＴＣＰＮ的调度分析。另外，讨论了ＴＣＰＮ沿含有失败变迁激活路径的调度问题。     

可信机器学习的公平性综述

人工智能在与人类生活息息相关的场景中自主决策时,正逐渐面临法律或伦理的问题或风险.可信机器学习是建立安全人工智能系统的核心技术,是人工智能领域的热门研究方向,而公平性是可信机器学习的重要考量.公平性旨在研究机器学习算法决策对个人或群体不存在因其固有或后天属性所引起的偏见或偏爱.从公平表征、公平建模和公平决策这3个角度出...     

时间约束Petri网的状态可达及可调度分析算法

时间约束Petri网是具有广义时间约束的一类Petri网。时间约束的引入使TCPN’s的演化与系统每一时刻的状态密切相关,导致网的动态复杂性。目前有关TCPN’s状态可达性的研究仅局限于一些较简单的网,该文通过对TCPN’s的进一步研究,给出了更一般的可达性分析方法及变迁可调度决策算法,并讨论了含冲突结构的TCPN’s的可调度分析。     

基于随机Petri网的性能与可靠性评价

近年来,随机Petri网在柔性制造系统、计算机及通信系统等领域的性能与可靠性评价中得到了广泛的应用。文章首先介绍了性能与可靠性评价,然后回顾了广义随机Petri网及其状态空间爆炸问题,最后讨论了非马尔科夫随机Petri网。     

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。     

基于分层模糊有色Petri网的防空C~3I系统建模研究

通过分析某防空C~3I系统的组成和运行方式,针对系统结构复杂、多种资源、资源多种模糊属性等特点,定义了一种分层模糊有色Petri网HFCPN,并给出具体的推理算法。在此基础上建立该防空C~3I系统模型,从而提出了一种建立防空C~3I系统分析模型的新方法。最后通过应用实例验证了该方法在描述系统分布、并发、异步等特性的同时,分析系统资源多种模糊属性问题的能力。     

Fairness and hyperfairness in multi-party interactions

Summary In this paper, a new fairness notion is proposed for languages withmulti-party interactions as the sole interprocess synchronization and communication primitive. The main advantage of this fairness notion is the elimination of starvation occurring solely due to race conditions (i.e., ordering of independent actions). Also, this is the first fairness notion for such languages which is fully adequate with respect to the criteria presented in [2]. The paper defines the notion, proves its properties, and presents examples of its usefulness. Orna Grumberg received her B.Sc. degree, M.Sc. and Ph.D. in the Computer Science Department at the Technion—Israel Institute of Technology. Since 1984 she is a faculty member in the Computer Science Department at the Technion. Her research interests include verification of distributed systems, computer-aided verification, model checking, temporal logics and automata. Paul Attie received a B.A. degree in engineering science from the University of Oxford, and an M.Sc. degree in computer science from the University of London. Since 1986, Paul has been with the Microelectronics and Computer Technology Corporation, where he is currently a member of technical staff. He is also a candidate for the Ph.D. in computer science degree at the University of Texas at Austin. His research interests include temporal logic, fairness, algebraic process theory, formal semantics, and concurrent program verification.The photograph and autobiography of Dr. Nissim Francez were published in Volume 2, Issue No. 4, 1988 on page 226