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.     

A dynamic Petri net model for iterative and interactive distributed multimedia presentation

Object Composition Petri Nets, Priority Petri Nets, Dynamic OCPN, and Enhanced P-Nets have extended the original Petri Net to achieve the modeling of media synchronization and asynchronous user interactions during multimedia playback. The dynamic Petri Net (DPN) has been conceptualized to tackle existing problems in these two areas of modeling distributed multimedia systems. DPN features dynamic modeling elements which allows iteration and hence is able to reduce graph sizes of synchronous playback models while allowing greater details to be shown. DPN also introduces asynchronous event handling techniques that are powerful and effective. DPN was used in the design and modeling of a multimedia orchestration tool which is a typical representation of an application that works in a distributed multimedia system.     

Building insightful simulation models using Petri Nets — A structured approach

Petri Nets have essential strengths in capturing a system's static structure and dynamics, its mathematical underpinning, and providing a graphical representation. However, visual simulation models of realistic systems based on Petri Nets are often perceived as too large and too complex to be easily understood. This constrains stakeholders in participating in such modeling and solution finding, and limits acceptance. We address this issue by considering a structured approach for guiding the analyst in creating more insightful models. Key elements are a domain-related reference architecture that supports conceptual modeling coupled with uniform rules for mapping high-level concepts onto low-level Petri Net components. The proposed approach is implemented and illustrated in the manufacturing domain.     

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.”     

Modular Petri Net based modeling,analysis, synthesis and performance evaluation of random topology dedicated production systems

Ordinary t-timed modular Petri Nets are used for modeling, analysis, synthesis and performance evaluation of random topology dedicated production systems. Each system is first decomposed into production line, assembly, disassembly and parallel machine modules followed by derivation of their modular Petri Net models. Two sets of modules, generic and generalized respectively, are derived corresponding to the simplest and most general cases. Overall system Petri Net model is obtained via synthesis of the individual modules satisfying system features (production rates, buffer capacities, machine expected up, down or idle times). Detailed mathematical expressions are derived for modules P-invariants (and T-invariants when exist); they are further generalized for a random topology and complexity dedicated production system. Total number of the individual Petri Net module nodes as well as of the combined system Petri Net model is also calculated. Results show the applicability of the proposed methodology and justify its modeling power and generality.     

CPM: A collaborative process modeling for cooperative manufacturers

In a manufacturing system, we need to capture collaborative processes among its components in order to clearly define supporting functions of a system. However, pervasive process modeling techniques, including IDEF3, Petri Nets, and UML, are not sufficient for modeling collaborative processes. Therefore, we have developed a novel modeling method referred to as collaborative process modeling (CPM) to describe collaborative processes. CPM models can be transformed into marked graph models so that we can use the analysis power of Petri Nets. In this paper, we first briefly discuss these process modeling techniques. Then, we illustrate the CPM method and transformation rules with illustrative examples. CPM allows us to develop collaborative process models, understand and facilitate the realization of collaboration, and verify models before moving onto development.     

Petri Net Plans

Programming the behavior of multi-robot systems is a challenging task which has a key role in developing effective systems in many application domains. In this paper, we present Petri Net Plans (PNPs), a language based on Petri Nets (PNs), which allows for intuitive and effective robot and multi-robot behavior design. PNPs are very expressive and support a rich set of features that are critical to develop robotic applications, including sensing, interrupts and concurrency. As a central feature, PNPs allow for a formal analysis of plans based on standard PN tools. Moreover, PNPs are suitable for modeling multi-robot systems and the developed behaviors can be executed in a distributed setting, while preserving the properties of the modeled system. PNPs have been deployed in several robotic platforms in different application domains. In this paper, we report three case studies, which address complex single robot plans, coordination and collaboration.     

一种随机着色Petri网及模型的性能分析

针对随机Petri网（SPN）在系统性能分析时,其状态空间随着系统规模增大而指数性增长,造成求解稳定状态概率的复杂性的不足,提出了一种随机着色Petri网（SCPN）。分析了它的有界性和可达性,证明了它同构于一个一维连续时间的马尔可夫链;同时,也分析了随机着色Petri网用于建模和系统性能定量分析的方法。     

Performance Modeling and Evaluation of Distributed Component-Based Systems Using Queueing Petri Nets

Performance models are used increasingly throughout the phases of the software engineering lifecycle of distributed component-based systems. However, as systems grow in size and complexity, building models that accurately capture the different aspects of their behavior becomes a more and more challenging task. In this paper, we present a novel case study of a realistic distributed component-based system, showing how Queueing Petri Net models can be exploited as a powerful performance prediction tool in the software engineering process. A detailed system model is built in a step-by-step fashion, validated, and then used to evaluate the system performance and scalability. Along with the case study, a practical performance modeling methodology is presented which helps to construct models that accurately reflect the system performance and scalability characteristics. Taking advantage of the modeling power and expressiveness of Queueing Petri Nets, our approach makes it possible to model the system at a higher degree of accuracy, providing a number of important benefits.     

Design and Analysis of Internet-Based Tele-Coordinated Multi-Robot Systems

The coordination of multi-robots is required in many scenarios for efficiency and task completion. Combined with teleoperation capabilities, coordinating robots provide a powerful tool. Add to this the Internet and now it is possible for multi-experts at multi-remote sites to control multi-robots in a coordinated fashion. For this to be feasible there are several hurdles to be crossed including Internet type delays, uncertainties in the environment and uncertainties in the object manipulated. In addition, there is a need to measure and control the quality of tele-coordination. To this end, the measure of force sensed by each robot is suggested and justified as a coordination index. It was proven that if n robots are event-transparent and event-synchronous then they can be teleoperated under random delay conditions to coordinate to any index value, which is feasible under no delay conditions. The design procedure that ensures a system can satisfy a small coordination index was presented and analyzed.In addition, the design and analysis of event-synchronous systems using Petri Nets is detailed. The Petri Net design methodology is presented for both event-synchronous single operator single robot teleoperation systems and event-synchronous multi-operator multi-robot teleoperation systems.The theory developed was tested by bilaterally tele-coordinating two mobile manipulators via the Internet. The experimental results confirmed the theoretical results presented.     

一类Petri网系统的活性

Petri网是一种用来研究具有异步、并发特征的离散事件系统的合适的工具，当用Petri网来模拟一个实际系统时，关心的问题之一就是要确定这个Petri网模型是否具有一些所期望的特生，如活性、有界性等，这些特性均是系统的重要动态行为，该文基于文献[1]给出了Petri网的一子类，即弱化非自控网（Weak Extended Non SelfControlling Nets,简称WENSeC网），该类网覆盖了扩展自由选择网和扩展非自控网，文中提出了并证明了WENSeC网系统活性的的充分必要条件满足死锁－陷阱性质，同时对WENSeC网的一子类，通过转化方法，证明了该类结构有界网的结构活判定算法可借用扩非自控网的有关结果也是多项式时间算法。     

立体分层Petri网的对象化专家系统实现

Ｐｅｔｒｉ网是描述分布式系统的强有力工具,立体分层Ｐｅｔｒｉ网是从系统的监控、行为和运行三个侧面分析实时分布式多智能体系的建模和分析工具。将立分层Ｐｅｔｒ８网转化为对象化的高级Ｐｅｔｒｉ网,利用和ＲＥＴＥ算泊结构相似性改善其软件实现方法,提高系统运行效率。     

一种面向对象Petri网模型的语义和行为分析

面向对象Petri网根据面向对象思想的特点,对基本Petri网进行了扩展,引入了门、位置类型函数、多态迁移、聚集迁移以及禁止弧等概念.本文介绍了一种面向对象Petri网模型（Object-Oriented Petri Net,OOPN）,给出了OOPN的基本定义和图形表示,并对OOPN进行了语义与行为分析.OOPN能够成为面向对象系统的一种形式化的建模工具.     

模糊Petri网的反馈控制研究

本文首先将模拟技术应用于Ｐｅｔｒｉ网中，得到模糊Ｐｅｔｒｉ网模型，然后基于Ｐｅｔｒｉ网中的库所湾量的概念，在普通Ｐｅｔｒｉ网的反馈控制基础上提出了一种模型Ｐｅｔｒｉ网的反馈控制方法。该方法使得对复杂系统的模糊Ｐｅｔｒｉ多控制器的系统设计成为可能。     

Mobile Synchronizing Petri Nets: A Choreographic Approach for Coordination in Ubiquitous Systems

The term Ubiquitous Computing was coined by Mark Weiser almost two decades ago. Despite all the time that has passed since Weiser's vision, ubiquitous computing still has a long way ahead to become a pervasive reality. One of the reasons for this may be the lack of widely accepted formal models capable of capturing and analyzing the complexity of the new paradigm. We propose a simple Petri Net based model to study some of its main characteristics. We model both devices and software components as a special kind of coloured Petri Nets, located in locations, that can move to other locations and synchronize with other co-located nets, offering and requesting services. We obtain an amenable model for ubiquitous computing, due to its graphical representation. We present our proposal in a progressive way, first presenting a basic model where coordination is formalized by the synchronized firing of pairs of compatible transitions that offer and request a specific service, and ad hoc networks are modeled by constraining mobility by the dynamic acquisition of locality names. Next, we introduce a mechanism for the treatment of robust security properties, namely the generation of fresh private names, to be used for authentication properties.     

序佩特里(Petri)网计算能力分析

本文通过引进序Petri网的概念,定义了序Petri网计算机,最后讨论该机器的计算能力:它可以计算所有的一般递归函数。