一种网络服务自动部署方法

为满足网络服务使用者对网络服务部署的功能性和非功能性需求,运用Petri网的方法进行了互联网动态多变环境下的网络服务自动部署的研究,建立了一种基于Petri网的网络服务部署网模型,从形式化的角度描述了网络服务功能的部署情况,提出了一种按照服务质量来选择最优网络服务部署的算法。仿真的结果表明,与目前常用的固定部署算法和随机部署算法相比,按照该方法得到的网络服务部署能最好地满足服务使用者对服务的非功能性方面的需求。     

应用Petri网改进基于故障树的诊断方法

故障树是表示故障发生和故障传播关系的一种逻辑模型,基于故障树诊断方法的广泛应用由于实际故障树分析过程的ＮＰ困难问题而受到妨碍。而Ｐｅｔｉｒ网是一种特殊的有向网,适合于描述故障的传播关系。本文提出了两种基于Ｐｅｔｒｉ网的改进方法,与下行法相比,用该方法寻找最小割集和最小路集能有效地节省上计算时间,提高推理速度和效率;最后还应用Ｐｉｔｒｉ网的状态方程分析方法提出了基于Ｐｅｔｒｉ网的故障监测和诊断方法。     

信任协商策略的Petri网建模分析方法

对Peer-to-Peer网络环境下信任协商和信任协商策略进行了定义和形式化描述,提出了一种基于Petri网模型的信任协商策略建模分析方法,将资源、证书和资源访问策略映射为Petri网网元进行建模,通过可达分析寻找最优资源解锁序列.和其他信任协商策略建模方法相比,该方法具有较好的性能.     

基于Petri网的工作流建模研究

工作流技术正在成为计算机应用领域的研究热点。Petri网以其简洁、直观、潜在模拟能力强等特点被广泛用于用于工作流模型的建立。本文在介绍工作流和Petri网基本概念的基础上,给出了使用Petri网建立工作流的模型。     

基于Petri网的网络安全系统故障查询方法

采用Petri网构造网络系统故障传播模型,并利用网络安全系统的层次特性,将网络安全系统逐级分解,级联,建立出更适用分析网络安全系统的Petri网模型,为具有网络拓扑结构的网络安全系统故障分析提供新的思路。     

基于广义随机Petri网GSPN的系统安全性研究

针对基于广义随机Petri网GSPN的动态系统安全性建模与分析方法进行了系统研究。基于Petri网、GSPN模型的基本原理，提出了关键状态搜索算法，并进行了安全性仿真分析．将广义随机Petri网的扩展模型应用于安全性分析领域，丰富了动态系统安全性问题的研究手段。     

一种实现无扰切换的功能块系统及其着色Petri网建模

提出了基于着色Petri网（CP网）的功能块集成模型。这模型采用模块化、面向对象的建模思想,分别以一个CP网来描述不同的功能块,在每个CP网内部定义了内部变量和外部消息。当利用功能构造控制系统时,相应地把代表它们的CP网集成在一起,并且通过消息传递,协调功能块之间的作用关系,共同完成控制系统的功能。     

基于Petri网的工作流模型的合理性验证

首先根据现实世界中的工作流正确性的概念,给出工作流网正确性的形式化描述,并给出工作流模型的合理性的定义,最后提出基于可达数的合理性验证算法,从而快速完成工作流模型的分析与验证。     

基于TOC和Petri网的业务流程重组方法

业务流程重组是企业根据市场和环境变化进行自身调整和完善,从而在竞争中取得优势的重要手段.通过Petri网建模可以对企业业务流程进行动态分析和控制,寻找制约企业盈利的最薄弱环节.在此基础上,应用约束理论(TOC)能够对业务流程中最薄弱的环节进行改进和重组,逐一消除制约环节,不断提升企业的竞争能力.在分析Petri网流程建模思路和约束理论基本原理的基础上,提出了基于Petri网和约束理论的业务流程重组方法,并进行了实证研究.     

基于UML与Petri网的一体化C4KISR系统体系结构研究

作为高科技武器系统及作战系统的核心部分-C4KISR指挥自动化系统,在现代战争中发挥这日益重要的作用,其性能的优劣直接影响到能否取得信息优势和占据作战优势.未来一体化C4KISR系统的不断完善和发展,将帮助军队以更加准确的获取信息,掌控战场局面.由于一体化C4KISR系统的复杂性,必须在开发前进行仿真建模研究,以验证系统的可行性.该文主要采用UML与Petri网相结合,对C4KISR系统建立动态和静态的模型,对系统进行仿真建模.     

Petri net based scheduling

Timed Petri nets can be used to model and analyse scheduling problems. To support the modelling of scheduling problems, we provide a method to map tasks, resources and constraints onto a timed Petri net. By mapping scheduling problems onto Petri nets, we are able to use standard Petri net theory. In this paper we will show that we can use Petri net based tools and techniques to find conflicting and redundant precedences, upper- and lower-bounds for the makespan, etc. This is illustrated by a Petri net based analysis of the notorious 10×10 problem due to Fisher & Thompson (1963)     

Coloured Petri net‐based modeling for distributed relational database queries

Abstract

In this paper, a new application of colour timed Petri net (CTPN) based methodology for distributed relational database queries modeling and corresponding simulation is addressed. This work, first based on parsed query definitions, converts logical query plans into designed CTPN models. Later, the improved cost‐based functions are then established and appended to CTPN with a general purpose CPN simulator‐Design/CPN to observe the thresholds of query operations. The propose CTPN can be used in the design phase as an experimental prototype to automatically simulate distributed database query processing which, in turn, may considerably reduce the load of developing the actual query processing software in the logical design phase of a distributed database system. Also, since all the essential details of query processing in CTPN have been simulated, the results of this study can be closely related to real world applications.     

Scheduling manufacturing systems with blocking: a Petri net approach

This paper introduces a Petri net-based approach for scheduling manufacturing systems with blocking. The modelling of the job routings and the resource and blocking constraints is carried out with the Petri net formalism due to their capability of representing dynamic, concurrent discrete-event dynamic systems. In addition Petri nets can detect deadlocks typically found in systems with blocking constraints. The scheduling task is performed with an algorithm that combines the classical A* search with an aggressive node-pruning strategy. Tests were conducted on a variety of manufacturing systems that included classical job shop, flexible job shop and flexible manufacturing scheduling problems. The optimisation criterion was makespan. The experiments show that the algorithm performed well in all types of problems both in terms of solution quality and computing times.     

A correct minimal siphons extraction algorithm from a maximal unmarked siphon of a Petri net

When using the machine grouping approach for designing cellular manufacturing cells, improper machine assignment commonly arises resulting in higher intercellular movement of parts. The objective of this paper is therefore to examine the cause of such a problem and to propose a workable optimal solution for it. A machine grouping algorithm that is based in the new machine unit concept is developed and the solution is proven to be optimal at each stage. A comparison of the proposed model with two existing algorithms is presented, followed by a discussion on the behaviour of machine cell formation.     

Hybrid Petri net and digraph approach for deadlock prevention in automated manufacturing systems

This paper proposes a hybrid approach to deadlock prevention in automated manufacturing systems that combines Petri nets (PNs) and digraphs, so taking advantage of the strong points of both techniques. The approach uses digraphs to make the detection of deadlock conditions easier and then translates the obtained information in empty siphons of the PN modelling the same system. The proposed methodology allows the implementation of new PN‐based deadlock prevention control policies. A case study and the simulation results show the benefits of the new control strategies.     

Optimisation of block erection scheduling based on a Petri net and discrete PSO

The shipyard block erection system (SBES) is a typical discrete-event dynamic system. To model multiprocessing paths and a concurrent assembly procedure, a timed Petri net (TPN) is proposed. The definition of a Petri net is extended to accord with the real-world SBES organisation. The basic TPN modules are presented to model the corresponding variable structures in the SBES, and then the scheduling model of the whole SBES is easily constructed. A modified discrete particle swarm optimisation (PSO) based on the reachability analysis of Petri nets is developed for scheduling of the SBES. In the proposed algorithm, particles are coded by welding transitions and selecting places of the TPN model, and then the collaboration and competition of particle individuals is simulated by crossover and mutation operators in a genetic algorithm. Numerical simulation suggests that the proposed TPN–PSO scheduler can provide an improvement over the conventional scheduling method. Finally, a case study of the optimisation of a back block erection process is provided to illustrate the effectiveness of the method.     

A model based approach to assess the performance of production systems in degraded mode

Nowadays production systems are asked to perform their activities in a high uncertainty environment and to guarantee their performance in this environment. Therefore, they are asked to master risks that are part of their daily activities, to maintain the performance which is considered as their key success factor. Risks may cause serious effects that threaten the production systems and degrade their performance. Nevertheless, we cannot estimate the degradation that a risk may cause to system performance, since risk analysis methods found in the literature do not allow simulating the behaviour of the system in degraded mode. In order to help production systems to assess their performance in risk situations, we propose in this paper a model-based approach that enables assessing the performance of production systems in degraded mode. Our approach is based on function, interaction, structure (FIS) modelling framework that enables modelling complex system and its failures. The resulting model is converted into an executable simulation model based on a new class of Petri Nets (PNs) called predicate-transition, prioritised, synchronous (PTPS) PN. The obtained simulation model is then executed in order to obtain performance indicators in degraded mode. This tool is used during the system design, in order to study the impact of risks on the designed production system performance. It is also used to study an existing production system in order to analyse and optimise its behaviour in degraded mode. In this article, we present our tool and apply it to a special case of production systems which is a hospital sterilisation system.     

基于阶层式语义范例推理的服务组合方法研究

为了解决自动服务组合过程中的知识表示和知识积累问题和提高服务组合的可重用性、准确性并减少服务组合的代价,提出了一种基于阶层式语义范例推理的自动服务组合方法。该方法先通过设计适当的语义服务范例描述语言来描述不同类型的服务范例,然后构造阶层式的服务范例,在此基础上通过服务范例的相似度测量与选择机制获取满足用户需求的组合服务逻辑集成或引用,实现服务组合。通过与其他服务组合方法的对比实验与定性分析证明,基于语义范例推理的服务组合方法是可行和有效的。