Software modeling and analysis using a hierarchical object-oriented Petri net

Petri net is used widely to analyze and model various systems formally. Recently, many Petri nets mania devote their efforts to enhancing and extending the expressive power of Petri nets. One such effort is to extend Petri nets with object-oriented concepts. An object-oriented paradigm provides excellent concepts to model real-world problems. Object-oriented concepts allow us to build software systems easily, intuitively, and naturally. Although several high-level Petri nets with the concept of objects are suggested, these nets do not fully support the object-oriented concepts. In this paper, we propose a hierarchical object-oriented Petri net (HOONet). The formal syntax and semantics of HOONet are explained in detail. HOONet supports a wide range of object-oriented features including abstract, encapsulated and modularized objects, object interaction by message passing, inheritance, and ploymorphism. HOONet also supports a variety of modeling and analysis mechanisms such as incremental modeling of evolving systems, unfolding the HOONet to lower level Petri net, and incremental reachability analysis for HOONet models. We demonstrate the usefulness of HOONet by applying it to modeling and analysis with an example.     

价格着色Petri网在工作流建模中的应用

在着色网的基础上扩展了价格信息,提出了价格着色网,用来对业务流程进行价格建模并对其作相应的成本预算分析.其中讨论了价格着色网的变迁步规则,提出了价格着色网中的标识--经济标识的定义,并有针对性地提出了最小成本构造算法.最后以一个业务流程实例演示了该模型的应用,得出结论为价格着色网能够较好地解决业务流程建模中的成本预算分析问题而且该模型中的最小成本构造算法是有效的.     

可重构制造系统的Petri网建模和分析方法

提出一种针对可重构制造系统的Petri网建模和分析方法．根据生产流程图可以得出制造系统的基本网模型,扩展基本网模型即可得到系统的Petri网模型．当生产任务发生改变并建立新的生产流程图时,可直接从原来的基本网模型构造出新构形的基本网模型．此外给出了系统重构代价的评价方法．仿真研究验证了该方法的有效性。     

A Petri net synthesis theory for modeling flexible manufacturingsystems

A theory that synthesizes Petri nets for modeling flexible manufacturing systems is presented. The theory adopts a bottom-up or modular-composition approach to construct net models. Each module is modeled as a resource control net (RCN), which represents a subsystem that controls a resource type in a flexible manufacturing system. Interactions among the modules are described as the common transition and transition subnets. The net obtained by merging the modules with two minimal restrictions is shown to be conservative and thus bounded. An algorithm is developed to detect two sufficient conditions for structural liveness of the net. The algorithm examines only the net's structure and the initial marking, and appears to be more efficient than state enumeration techniques such as the reachability tree method. In this paper, the sufficient conditions for liveness are shown to be related to some structural objects called siphons. To demonstrate the applicability of the theory, a flexible manufacturing system of a moderate size is modeled and analyzed using the proposed theory.     

Deadlock avoidance schemes in a distributed robotic system: Petri net modeling and analysis

This article presents a Petri net-based approach to modeling and evaluating four different deadlock avoidance schemes for a distributed robotic system, i.e., a five-robot-five-assembly-line system. Among these four schemes are the conventional, full synchronization, global semaphore, and partial synchronization schemes. To explore such issues as the system performance and control structure complexity, this article conducts detailed Petri net modeling for this system and evaluates performance of the deadlock avoidance schemes using stochastic Petri nets. The interesting results presented include that: (1) any possible system deadlock can seriously degrade the system performance even if effective deadlock resolution techniques are available; (2) conservative use of resources is likely to be the best policy; and (3) higher resource utilization may not necessarily imply higher system production rate in a resource-sharing environment. The related results need to be further explored for the larger resource-sharing discrete event systems. © 1995 John Wiley & Sons, Inc.     

Petri net modeling and deadlock analysis of parallel manufacturing processes with shared-resources

Multiple resource-sharing is a common situation in parallel and complex manufacturing processes and may lead to deadlock states. To alleviate this issue, this paper presents the method of modeling parallel processing flows, sharing limited number of resources, in flexible manufacturing systems (FMSs). A new class of Petri net called parallel process net with resources (PPNRs) is introduced for modeling such FMSs. PPNRs have the capacity to model the more complex resource-sharing among parallel manufacturing processes. Furthermore, this paper presents the simple diagnostic and remedial procedures for deadlocks in PPNRs. The proposed technique for deadlock detection and recovery is based on transition vectors which have the power of determining the structural aspects as well as the process flow condition in PPNRs. Moreover, the proposed technique for dealing with deadlocks is not a siphon-based thus the large-scale PPNRs for real-life FMSs can be tackled. Finally, the proposed method of modeling and deadlock analysis in the FMS having parallel processing is demonstrated by a practical example.     

Neuron type processor modeling using a timed Petri net

The basic operation of a digital neuron is reviewed, and the theory of time Petri nets used for modeling, representation, and analysis of the neuron-type processor (NTP) is reviewed. The timed Petri net is utilized to produce a model for the digital NTP. The neuron-type processor performs input temporal and spatial summation, as well as thresholding. The timed Petri net of the NTP operates asynchronously and sequentially takes on a series of distinct internal states, so that each of these states can concurrently realize a distinct set of steering switching functions depending on the pattern of steering inputs applied to it at the time. This model is structured using several subnets, called essential module units. Depending on the desired number of input dendrites required for the NTP, the essential module units (EMU) are interconnected to produce the required timed Petri net. The timed Petri net and representation facilitates a method of analysis of neural net works containing NTPs prior to hardware implementation.     

无线通信系统的Petri网建模与分析

无线通信系统是一个分布式实时多任务数据处理系统,具有实时性、并发、异步和多任务等特点.Petri网是描述和分析异步并发现象的一种有效的模型工具.以Petri网为工具,建立了无线通信系统的仿真模型,对其功能和数据流进行模拟,并对其结构性能、任务的忙闲程度、死锁进行了定性分析,实现了模型和程序结构的自动转换,从一个全新角度对无线通信系统进行了分析和评价.     

道路交通信息分析与建模

交通流速度.流量和密度是道路交通信息的主要参数,分析参数的特性并对其建模是研究交通信息重要部分.以浮动车和线圈采集的数据为研究对象,基于小波技术对数据除去噪声,并通过线性回归预测误差的衰减率选取合适的拟合阶数,从而运用线性回归方法对数据进行拟合.最后对北京市区某道路的采集数据进行分析,结果表明该模型具有可行性和有效性.     

基于Petri网的混合安全策略建模与验证

提出了一种基于有色Petri网的建模方法,在系统的Petri网模型中可以对中国墙策略进行分析和验证.给出了基于有色Petri网的混合安全策略的形式化定义;并通过一个系统实例阐述了如何利用该方法对系统的混合安全性进行分析和验证.无论是在系统的设计阶段还是实现阶段,该方法都能够有效地提升系统的混合安全性.     

Supervisory control of a multi-echelon supply chain: A modular Petri net approach for inter-organizational control

Petri nets (PNs) are frequently utilized to model system dynamics due to their ability to handle concurrencies and sequential dependence. In this paper, a portion of the supply chain operations reference (SCOR) model has been extracted and modeled using PNs for the purpose of exerting supervisory control upon a multi-echelon supply chain (SC). The activities of source, make and deliver, inherent in the SCOR model form the basis of the representation of the PN model for each echelon considered in the SC model. Two control nets are utilized: one above the base model of each echelon to exert local constraints and an enterprise level supply chain manager (SCM). The local constraints are at the tactical and operational levels while the SCM enforces additional constraints consisting of long term planning goals at the strategic level. Place invariants are used to create the supervisors. Performance measures of the total SC are formulated to determine the effectiveness of any partnership. An efficient method for finding the current state of the system is developed which is used to determine the performance measures of each echelon. This paper presents a modular approach to the overall structure and PN modeling for a SC system. It is intended to extend the use of supervisory control from a shop-floor level to an inter-organizational facility and enterprise level.     

基于Petri网的数字系统建模和VHDL实现

基于Petri网的数字系统的建模及其硬件实现方法已经得到了广泛的研究,然而现有的方法主要适用于同步电路,由此提出了一种基于Petri网的数字系统建模和VHDL实现的新方法。首先定义了一种广义同步自控网系统,解决了数字系统的Petri网建模问题。基于一种带优先级的多输入多时钟D触发器,设计了对应的软IP核,进而探讨了广义同步自控网系统模型到VHDL代码的具体转换方法。设计的CAD工具支持数字系统的建模、功能分析与代码转换功能。通过设计示例表明了所述方法和相关工具的有效性。     

并行计算的Petri网建模和FPGA实现

在分析现有Petri网建模及其FPGA实现方法的基础上, 首先探讨了并行计算的Petri网建模方法, 将并行计算任务分解成多个并行处理单元, 用IOPT网为系统进行建模; 然后提出了构造监控层和算法层的双层结构以实现模型到FPGA实现的具体映射, 有效解决了Petri网模型中变迁只能表示简单加减运算的问题。通过矩阵乘法的应用示例, 表明了上述方法的正确性和通用性。最后提出了进一步的研究方向。     

A new Petri net modeling technique for the performance analysis of discrete event dynamic systems

An interesting modeling problem is the need to model one or more of the system modules without exposition to the other system modules. This modeling problem arises due to our interest in these modules or incomplete knowledge, or inherent complexity, of the rest of the system modules. Whenever the performance measures (one or more) of the desired modules are available through previous performance studies, data sheets, or previous experimental works, the required performance measures for the whole system can be predicted from our proposed modeling technique. The incomplete knowledge problem of the dynamic behavior of some system modules has been studied by control theory. In the control area, such systems are known as partially observed discrete event dynamic systems, or POS systems. To the best of our knowledge, the performance evaluation of the POS system has not been addressed by the Petri net theory yet.Therefore, in this paper, we propose a new modeling technique for solving this kind of problem based on using the Petri net theory (i.e. Stochastic Reward Nets (SRNs)) in conjunction with the optimal control theory. In this technique, we develop an SRN Equivalent Model (EM) for the modeled system. The SRN EM-model consists of two main nets and their interface nets. One of the main nets represents the part(s) of interest or the known part(s) of the overall POS system that allows us to model its dynamic behavior and evaluate its performance measures. The other main net represents the remaining part(s) of the overall POS system that feeds the part(s) of interest. The well-known maximum principles have been used to develop an algorithm for determining the unknown transition rates of the proposed model. Numerical simulations are given to show that the proposed approach is more effective than the conventional modeling techniques, especially when dealing with systems having a large number of states.     

基于Petri网的情境感知系统建模与仿真*

情境感知系统对情境信息的利用程度在不断提高,对服务的多样性提出了更高要求,但是传统的情境感知系统的建模方法难以满足对系统动态描述和模拟的需求。通过对传统的Petri网进行扩展,提出了情境感知系统的赋时着色Petri网模型;并结合仿真工具CPN Tools对模型进行模拟和验证,进而发现系统设计中存在的潜在不足,对其优化改进。以痴呆老人智能辅助系统为例,证明了该方法的有效性。     

虚拟制造企业的Petri网建模/仿真

为降低Petri网建模难度并增强模型的可读性,提出一种通过消息序列表（Message Sequence Chart,MSC）模型对虚拟制造（Virtual Manufacturing,VM）企业的生产经营过程进行Petri网建模的新方法．建立冲突消解机制,给出从MSC模型到Petri网模型的转换算法,在不改变Petri模型活性、安全性和有界性等特性的基础上对其进一步优化,并对Petri网模型进行分析与评估．     

Stochastic Petri net analysis of a replicated file system

The authors present a stochastic Petri net model of a replicated file system in a distributed environment where replicated files reside on different hosts and a voting algorithm is used to maintain consistency. Witnesses, which simply record the status of the file but contain no data, can be used in addition to or in place of files to reduce overhead. A model sufficiently detailed to include file status (current or out-of-date) as well as failure and repair of hosts where copies or witnesses reside, is presented. The number of copies and witnesses is not fixed, but is a parameter of the model. Two different majority protocols are examined     

基于Petri网理论的计算机网络性能分析和电子商务模型设计

本文采用Petri网作为建模求解工具,揭示TCP网络的实质,探讨TCP网络的性能分析问题和电子商务系统中的买方和卖方模型设计问题。最后对全文进行了概括性总结,并指出了理论和应用上有待进一步研究的问题。     

基于扩展Petri网的系统建模及形式化验证方法*

嵌入式实时系统对时间约束性、安全性和可靠性具有非常高的要求,但是传统的建模和形式化验证方法难以满足对系统的实时性和安全性的模拟和验证需求。通过对有色Petri网的时间属性进行扩展,提出了实时有色Petri网模型,能够对系统的时间属性进行模拟和评估;参考实时有色Petri网模型到时间自动机的语义转换规则对模型进行转换,可以利用时间计算树逻辑对系统的实时性、安全性和可靠性进行形式化验证。以列车通信网络控制器的双线冗余控制模块的建模和形式化验证为例,证明了该方法的有效性。     

Petri网在代谢网络模块化分析中的应用

代谢网络的模块化分析有助于理解网络的结构和功能。然而,当前众多的模块化分析方法大多将代谢网络考虑为普通的复杂网络,所得模块的生物学意义较低。对枯草芽孢杆菌的核黄素代谢进行Petri网建模分析,研究结果表明：Petri网的T不变量可用于识别代谢网络中的功能模块,具备较好的生物学意义。