Commutation properties and generating sets characterize slices of various synchronization primitives

Various synchronization primitives are described by adding and testing integer vectors, or by using “Petri Nets”. A slice represents a local behavior, described by permissible sequences of distinct actions of the system.We present a double characterization of slices defined by various synchronization primitives: In terms of generating sets and dually in terms of commutation properties. A typical form of a commutation property is: The set of sequences of past actions which disallow a certain coming action is closed under certain permutations. The synchronization primitives treated here include various systems which lie between PV and Vector Replacement Systems or Petri Nets.     

Modeling shared resources with generalized synchronization within aPetri net bottom-up approach

This paper proposes a simple and effective way to represent shared resources in manufacturing systems within a Petri net model previously developed. Such a model relies on the bottom-up and modular approach to synthesis and analysis. The designer may define elementary tasks and then connect them with one another with three kinds of connections: self-loops, inhibitor arcs and simple synchronizations. A theoretical framework has been established for the analysis of liveness and reversibility of such models. The generalized synchronization, here formalized, represents an extension of the simple synchronization, allowing the merging of suitable subnets among elementary tasks. It is proved that under suitable, but not restrictive, hypotheses the generalized synchronization may be substituted for a simple one, thus being compatible with all the developed theoretical body.     

基于Petri网的多媒体同步通信模型

本文提出了一种新的多媒体同步模型--交互式多媒体动态同步Petri网模型(IMDSPN)。IMDSPN能够准确地描述多媒体对象的各种同步时态关系,可以克服其表现过程中的同步失败问题,并可以保证在用户交互控制下同步关系的全局一致性,它有效地描述了多媒体的动态特性。     

A methodology to specify three-dimensional interaction using Petri Nets

This work presents a methodology to formally model and to build three-dimensional interaction tasks in virtual environments using three different tools: Petri Nets, the Interaction Technique Decomposition taxonomy, and Object-Oriented techniques. User operations in the virtual environment are represented as Petri Net nodes; these nodes, when linked, represent the interaction process stages. In our methodology, places represent all the states an application can reach, transitions define the conditions to start an action, and tokens embody the data manipulated by the application. As a result of this modeling process we automatically generate the core of the application's source code. We also use a Petri Net execution library to run the application code. In order to facilitate the application modeling, we have adapted Dia, a well-known graphical diagram editor, to support Petri Nets creation and code generation. The integration of these approaches results in a modular application, based on Petri Nets formalism that allows for the specification of an interaction task and for the reuse of developed blocks in new virtual environment projects.     

扩展模糊时间Petri网的定义和性质

随着装备的复杂程度不断地提高,对装备的故障诊断难度也不断加大,容易出现故障原因漏判的现象。为解决此问题,文章在模糊时间Petri网的基础上,通过在库所和变迁中引入模糊时间戳对其进行扩展,建立扩展模糊时间Petri网模型,并给出相关计算和运行实例。     

一种基于同步合成构造Petri网进程表达式的方法

Petri网的进程是用于系统行为和状态描述的有效工具,Petri网的进程表达式可以给出系统全部进程的描述,但是对于任意无界Petri网而言求取其进程表达式十分困难.文中首先考察结构简单的S-网的进程行为,给出各种类型的S-网的进程表达式的描述方法.然后拓展了Petri网同步合成的概念,分析了同步合成过程中基本进程段集之间的关系,并利用同步混排给出了进程表达式之间的关系.随后证明了一个Petri网可以通过一组S-网同步合成得到,利用S-网的进程表达式给出了构造Petri网的进程表达式的方法.     

一种生成具有变量标识的高级Petri网可达树的算法

Petri网动态性质的考察一般基于网不变量(Net Invariants)和可达树(Reachability Tree).这两个概念已被扩展到高级Petri网中.高级Petri网可达集空间随着网的复杂性而指数性增长是计算可达树问题中的一个主要难 点.本文定义了具有变量标识的高级Petri网并给出了构造该类网的可达树的算法.本文的算法以变量标识的等价关系(equivalent relation)和覆盖关系(covering relation)为基础,明显地简化了可达集空间.个体标识的信息可从变量标识的定义域中获得.     

Coloured Petri Nets and CPN Tools for modelling and validation of concurrent systems

Coloured Petri Nets (CPNs) is a language for the modelling and validation of systems in which concurrency, communication, and synchronisation play a major role. Coloured Petri Nets is a discrete-event modelling language combining Petri nets with the functional programming language Standard ML. Petri nets provide the foundation of the graphical notation and the basic primitives for modelling concurrency, communication, and synchronisation. Standard ML provides the primitives for the definition of data types, describing data manipulation, and for creating compact and parameterisable models. A CPN model of a system is an executable model representing the states of the system and the events (transitions) that can cause the system to change state. The CPN language makes it possible to organise a model as a set of modules, and it includes a time concept for representing the time taken to execute events in the modelled system. CPN Tools is an industrial-strength computer tool for constructing and analysing CPN models. Using CPN Tools, it is possible to investigate the behaviour of the modelled system using simulation, to verify properties by means of state space methods and model checking, and to conduct simulation-based performance analysis. User interaction with CPN Tools is based on direct manipulation of the graphical representation of the CPN model using interaction techniques, such as tool palettes and marking menus. A license for CPN Tools can be obtained free of charge, also for commercial use.     

Another approach to the implementation of synchronization primitives

A new method for the implementation of synchronization primitives is described. The method combines the flexibility of user defined primitives with the possibility of compiler checks. The method allows the tailoring of the size and of the performance of the synchronization primitives to the needs of the user.     

Implementing Coloured Petri Nets Using a Functional Programming Language

Coloured Petri Nets (CPNs) are a graphically oriented modelling language for concurrent systems based on Petri Nets and the functional programming language Standard ML. Petri Nets provide the primitives for modelling concurrency and synchronisation. Standard ML provides the primitives for modelling data manipulation and for creating compact and parameterisable CPN models.Functional programming and Standard ML have played a major role in the development of CPNs and the CPN computer tools supporting modelling, simulation, verification, and performance analysis of concurrent systems. At the modelling language level, Standard ML has extended Petri Nets with the practical expressiveness required for modelling systems of the size and complexity found in typical industrial projects. At the implementation level, Standard ML has been used to implement the formal semantics of CPNs that provide the theoretical foundation of the CPN computer tools.This paper provides an overview of how functional programming and Standard ML are applied in the CPN modelling language and the supporting computer tools. We give a detailed presentation of the key algorithms and techniques used for implementing the formal semantics of CPNs, and we survey a number of case studies where CPNs have been used for the design and analysis of systems. We also demonstrate how the use of a Standard ML programming environment has allowed Petri Nets to be used for the implementation of systems.     

Model interoperability via Model Driven Development

Among the factors that contribute to the inherent complexity of the software development process is the gap between the design and the formal analysis domains. Software design is often considered a human oriented task while the analysis phase draws on formal representation and mathematical foundations. An example of this dichotomy is the use of UML for the software design phase and Petri Nets for the analysis; a separation of concerns that leads to the creation of heterogeneous models. Although UML is widely accepted as a language that can be used to model the structural and behavioural aspects of a system, its lack of mathematical foundations is seen as a serious impediment to rigorous analysis. Petri Nets on the other hand have a strong mathematical basis that are well suited for formal analysis; they lack however the appeal and the ease-of-use of UML. A pressing concern for software developers is how to bridge the gap between these domains and allow for model interoperability and the integration of different toolsets across them, and thus reduce the complexity of the software development process. The aim of this paper is to present a Model Driven Development (MDD) model transformation which supports a seamless transition between UML and Petri Nets. This is achieved by model interoperability from UML Sequence Diagrams to Petri Nets and supported by tool integration. The model transformation framework allows a software system to be designed in terms of UML Sequence Diagrams and subjected to formal analysis by taking advantage of the strong mathematical framework of Petri Nets. The behaviour of a Personal Area Network will be used to illustrate the proposed approach and to highlight model interoperability and tool integration through the design, the transformation and the analysis phases.     

基于物料清单的制造过程工作流建模

分析了物料清单(BOM)在产品制造过程中的核心地位,提出了将BOM表映射成PETRI网的算法,利用所得到的PETRI网建立了面向制造过程的工作流管理系统的模型。从而允许设计者根据产品的结构而不需要知道实际的过程流程来安排生产任务的自动执行。对于生产作业计划的制订有很好的指导意义。     

时间约束工作流的可调度性分析

提出一种时间约束工作流的可调度性分析方法。针对时间约束Petri网（Timing Constraint Petri Nets,TCPN）为普通Petri网无法建模多参与资源的不足,给出了扩展的时间约束Petri网（w-TCPN）的定义;结合w-TCPN的拓扑结构,从模型和实例两个层次,给出了w-TCPN变迁可调度的判定定理;提出了时间约束的调整策略。w-TCPN的研究使得时间约束工作流的建模和可调度性分析更加合理。     

基于Petri网与SimEvents的半导体晶圆生产线建模与仿真

SimEvents与Petri网相结合是一种很好的复杂生产线建模仿真方法,应用这一方法建立了一条300mm晶圆生产线的仿真模型.描述了其Petri网模型建立的总体流程和各个详细步骤,以及在SimEvents环境下实现Petri网模型并进行仿真的关键技术.在此基础上,对晶圆生产的不同调度方案分别进行了仿真,并把仿真结果进行了比较,从而验证了仿真建模方法的正确性.     

离散事件动态系统的代数模型及其控制器的分析计算

本文在离散事件动态系统的Ｐｅｔｒｉ网图形描述的基础上建立了相应的代数模型，该模型可以用来计算无竞争无回路Ｐｅｔｒｉ网的“最大状态”；该“最大状态”的计算在本文给出的动态反馈控制器中得到了应用。     

分布式虚拟现实系统的信息同步研究

分布式虚拟现实技术已经开始应用于军事、航天、娱乐等多个领域,并取得了较好的效果,该文对分布式虚拟现实系统的一个关键技术－信息同步技术,进行了比较深入的分析和研究,提出了一个基于Ｐｅｔｒｉ信息同步模型,并提出了基于该模型的信息预取,状态估算,系统时间同步等控制策略。     

Graphical simulation of Petri Nets

An interactive graphics package for modeling with Petri Nets has been implemented. It uses the VT-11 graphics terminal supported on the PDP-11/35 computer to draw, execute, analyze, edit and redraw a Petri Net. Each of the above mentioned tasks can be performed by selecting appropriate items from a menu displayed on the screen. Petri Nets with a reasonably large number of nodes can be created and analyzed using this package. The number of nodes supported may be increased by making simple changes in the program. Being interactive, the program seeks information from the user after displaying appropriate messages on the terminal. After completing the Petri Net, it may be executed step by step and the changes in the number of tokens may be observed on the screen, at each place. Some properties of Petri Nets like safety, boundedness, conservation and redundancy can be checked using this package. This package can be used very effectively for modeling asynchronous (concurrent) systems with Petri Nets and simulating the model by “graphical execution.”