基于Petri网的工作流过程建模

业务过程建模是整个工作流管理系统的基础,选择一种高效的建模技术对复杂多变的实际业务流程进行形式化表示对构建一个灵活的工作流管理系统起着至关重要的作用。本文利用了Petri网技术给业务过程建模,构造了一个灵活可分析的过程模型：首先介绍了相关的基于Petri网的工作流建模技术,接着描述了Petri网到工作流过程模型执行的映 射,然后给出了一个具体的基于Petri网建模方式的实例,最后利用随机Petri网和概率论的一些知识对该模型进行了时间性能分析。     

Enhanced high-level Petri nets with multiple colors for knowledgeverification/validation of rule-based expert systems

Exploring the properties of rule-based expert systems through Petri net models has received a lot of attention. Traditional Petri nets provide a straightforward but inadequate method for knowledge verification/validation of rule-based expert systems. We propose an enhanced high-level Petri net model in which variables and negative information can be represented and processed properly. Rule inference is modeled exactly and some important aspects in rule-based systems (RBSs), such as conservation of facts, refraction, and closed-world assumption, are considered in this model. With the coloring scheme proposed in this paper, the tasks involved in checking the logic structure and output correctness of an RES are formally investigated. We focus on the detection of redundancy, conflicts, cycles, unnecessary conditions, dead ends, and unreachable goals in an RES. These knowledge verification/validation (KVV) tasks are formulated as the reachability problem and improper knowledge can be detected by solving a set of equations with respect to multiple colors. The complexity of our method is discussed and a comparison of our model with other Petri net models is presented.     

Timed high-level nets

Petri nets have been widely used for modeling and analyzing concurrent systems. Several reasons contribute to their success: the simplicity of the model, the immediate graphical representation, the easy modeling of asynchronous aspects, the possibility of reasoning about important properties such as reachability, liveness, boundedness. However, the original model fails in representing two important features: complex functional aspects, such as conditions which rule the flow of control, and time. Due to that, two different classes of extensions of Petri nets have been proposed: high-level nets and timed Petri nets. High-level nets allow the representation of functional aspects in full details, but do not provide a means for representing time; on the other hand, timed Petri nets have been thought for time representation, but they do not provide a means for representing detailed functinal aspects. Thus, these two important aspects cannot be mastered together. In particular, it is difficult to express relationships between time and functional aspects.This paper investigates the relationships between high-level nets and timed Petri nets, thus extending a first set of results published in a previous paper, where a unifying Petri net based model for time representation has been proposed. It first recalls how time can be represented in a Petri net extension called ER nets, and assesses its generality. It then investigates the relationships of ER nets with the best known high-level nets. In particular it shows the overall equivalence of ER nets, Colored Petri nets and Predicate/Transition nets, and extends the mechanism for time representation introduced in ER nets to both Colored Petri nets and Predicate/Transition nets. It also shows that these models cannot be simplified without significantly constraining the timing aspects that can be modeled.     

Integer Linear Programming and the Analysis of Some Petri Net Problems

A class of Petri nets (called type \cal L Petri nets in this paper) whose reachability sets can be characterized by integer linear programming is defined. Such Petri nets include the classes of conflict-free , normal , BPP , trap-circuit , and extended trap-circuit Petri nets, which have been extensively studied in the literature. We demonstrate that being of type \cal L is invariant with respect to a number of Petri net operations, using which Petri nets can be pieced together to form larger ones. We also show in this paper that for type \cal L Petri nets, the model checking problem for a number of temporal logics is reducible to the integer linear programming problem, yielding an NP upper bound for the model checking problem. Our work supplements some of the previous results concerning model checking for Petri nets. Received October 1997, and in revised form July 1998.     

On the Regularity of Petri Net Languages

Petri nets are known to be useful for modeling concurrent systems. Once modeled by a Petri net, the behavior of a concurrent system can be characterized by the set of all executable transition sequences, which in turn can be viewed as a language over an alphabet of symbols corresponding to the transitions of the underlying Petri net. In this paper, we study the language issue of Petri nets from a computational complexity viewpoint. We analyze the complexity of theregularity problem(i.e., the problem of determining whether a given Petri net defines an irregular language or not) for a variety of classes of Petri nets, includingconflict-free,trap-circuit,normal,sinkless,extended trap-circuit,BPP, andgeneralPetri nets. (Extended trap-circuit Petri nets are trap-circuit Petri nets augmented with a specific type ofcircuits.) As it turns out, the complexities for these Petri net classes range from NL (nondeterministic logspace), PTIME (polynomial time), and NP (nondeterministic polynomial time), to EXPSPACE (exponential space). In the process of deriving the complexity results, we develop adecomposition approachwhich, we feel, is interesting in its own right, and might have other applications to the analysis of Petri nets as well. As a by-product, an NP upper bound of the reachability problem for the class of extended trap-circuit Petri nets (which properly contains that of trap-circuit (and hence, conflict-free) and BPP-nets, and is incomparable with that of normal and sinkless Petri nets) is derived.     

Two theoretical and practical aspects of knitting technique:invariants and a new class of Petri net

We present two aspects of knitting technique, the structural properties (especially the P- and T-invariants), and the synchronized choice net (a new class of Petri net), that are of both theoretical importance and practical uses to the verification of structural correctness of a Petri net or to detect the structural problem of a Petri net. This work first proves that the ordinary Petri nets synthesized with knitting technique are structurally bounded, consistent, conservative and safe (when each home place holds one token) using the well-known linear algebra approach. It also provides a procedure for finding P- and T-invariants for Petri net synthesized using the knitting technique. We present examples for P-invariants and show that we can synthesize Petri nets more general than the "asymmetric-choice nets". The algorithm for finding P-invariants of ordinary Petri nets is extended to find the P-invariants for a general Petri net synthesized with knitting technique and the arc-ratio rules. We present a new class of Petri nets, called synchronized choice nets, which are the largest set of Petri nets that can be covered by both T-components and P-components. An algorithm is proposed to find its T-components and the P-components, respectively. The complexity of this algorithm is also presented. The theory of synchronized choice nets has the potential to simplify that for free choice nets.     

土壤—植被混合地表红外辐射温度场的耦合建模方法*

目前混合地表温度场的数学模型忽略了地表内部各组分间的热通量交互,致使温度场模拟结果不够准确、真实.针对已有独立求解模型的不足,结合土壤-植被混合地表的材质组成及空间分布特点,建立温度场的耦合求解模型,通过在热平衡方程中引入组分间热通量的交互项,对土壤-植被-大气耦合的能量平衡过程进行描述.实验结果表明,利用耦合模型求解的混合地表的温度场分布和热图像特征与自然地表红外辐射特性的真实分布规律具有更好的一致性,从而验证了温度场耦合建模方法的有效性.     

基于Petri网的建设工程项目实施阶段资源建模与仿真*

基于分层赋时着色Petri网,构建了一个能够准确表达资源配置、任务持续时间及信息传递的资源模型,以便有效进行建设工程项目实施阶段的资源管理和优化配置.在建设工程项目实施阶段资源特点分析的基础上,对分层赋时着色Petri网中的非空颜色集合进行定义,并对资源管理中分层建模、资源分配和资源归还基础模型进行了研究,解决了基于分层赋时着色Petri网构建建设工程项目实施阶段资源模型的关键问题.最后,以某工业与民用建筑的实施阶段为例,进行资源管理模型的构建和仿真分析,验证了基于分层赋时着色Petri网构建建设工程项目实施阶段资源管理模型的正确性和有效性.     

基于模糊神经Petri网的故障诊断模型

Petri网是对具有产生式规则的故障诊断系统的有力建模工具，但其缺乏较强的学习能力．本文以Petri网的基本定义为基础，结合模糊逻辑和Petri网模型，定义了模糊Petri网模型，在此基础上引入人工神经网络技术，给出了人工神经网络的模糊Petri网表示方法，并针对工程机械故障诊断异步、离散等特点，提出并建立了故障诊断的模糊神经Petri网模型及其改进模型．基于模糊神经Petri网的故障诊断系统结合了Petri网和人工神经网络的优点，经过自学习后同时具有很强的推理能力和自适应能力．     

基于Petri网的APT攻击模型生成方法

在严峻的APT(Advanced Persistent Threat)攻击防御背景下,针对现有网络攻击建模方法无法反映APT攻击的攻击特点,建立了基于Petri网的APT攻击模型。借助Petri网,首先针对APT攻击的特点及生命周期,建立APT攻击的基本Petri网模型;然后设计并实现APTPN(Advanced Persistent Threat Petri Nets)模型的生成算法,针对具体的APT攻击生成其完整的攻击路径;最后,实验通过模拟极光攻击验证了算法的有效性及正确性。     

A methodology for evaluating test coverage criteria of high levelPetri nets

High level Petri nets have been extensively used for modeling concurrent systems; however, their strong expressive power reduces their ability to be easily analyzed. Currently there are few effective formal analysis techniques to support the validation of high level Petri nets. The executable nature of high level Petri nets means that during validation they can be analyzed using test criteria defined on the net model. Recently, theoretical test adequacy coverage criteria for concurrent systems using high level Petri nets have been proposed. However, determining the applicability of these test adequacy criteria has not yet been undertaken. In this paper, we present an approach for evaluating the proposed test adequacy criteria for high level Petri nets through experimentation. In our experiments we use the simulation functionality of the model checker SPIN to analyze various test coverage criteria on high level Petri nets.     

Synchronization models for multimedia presentation with user participation

This paper addresses the key issue of providingflexible multimedia presentation with user participation and suggests synchronization models that can specify the user participation during the presentation. We study models like the Petrinet-based hypertext model and the object composition Petri nets (OCPN). We suggest adynamic timed Petri nets structure that can model pre-emptions and modifications to the temporal characteristics of the net. This structure can be adopted by the OCPN to facilitate modeling of multimedia synchronization characteristics with dynamic user participation. We show that the suggested enhancements for the dynamic timed Petri nets satisfy all the properties of the Petri net theory. We use the suggested enhancements to model typical scenarios in a multimedia presentation with user inputs.     

一种基于对象网的多视角软件过程模型

基于关注点分离原则,结合多视角软件过程建模与对象网之间的相似性,提出了一种基于对象网的多视角软件过程模型MOPN-SP-net,可以提高软件过程模型的可复用性(reusability).在使用MOPN-SP-net建模时,得到的多视角软件过程模型是一种多维网.直接分析这种多维网比较困难,为此,提供了一种从对象网到平面网的等价转换规则,且转换前后的模型在合理性准则上保持等价.根据这个转换规则,可以通过分析转换后平面网模型的合理性得知转换前的对象网的合理性.     

Verifying functions in online stock trading systems

Temporal colored Petri nets, an extension of temporal Petri nets, are introduced in this paper. It can distinguish the personality of individuals (tokens), describe clearly the causal and temporal relationships betwee nevents in concurrent systems, and represent elegantly certain fundamental properties of concurrent systems, such as eventuality and fairness. The use of this method is illustrated with an example of modeling and formal verification of an online stock trading system. The functional correctness of the modeled system is formally verified based on the temporal colored Petri net model and temporal assertions. Also, some main properties of the system are analyzed. It has been demonstrated sufficiently that temporal colored Petri nets can verify efficiently some time-related properties of concurrent systems, and provide both the power of dynamic representation graphically and the function of logical inference formally. Finally. future work is described.     

模糊Petri网在带权不精确知识表示和推理中的应用研究

Petri网是一种适合于描述异步并发事件的计算机系统模型 ,可以有效地对并行和并发系统进行形式化验证和行为分析 .以模糊 Petri网的基本定义为基础 ,讨论了带权模糊知识的模糊产生式系统表示法 ,建立了这种表示法与模糊 Petri网之间的映射关系和转换算法 ;在对模糊 Petri网进一步扩充的基础上 ,解决了与知识的模糊Petri网表示相关的几个问题 ;最后给出了模糊 Petri网中不确定性的计算方法和相应的不精确推理算法     

着色Petri网应用研究

着色Petri网是在经典Petri网理论基础上增加了token类型和网的模块这两个功能,它现在已成为一种较完善的语言,可以用来对各种系统规范和协议等进行设计、规范描写、仿真和验证等。文章对着色Petri网的基本理论进行了简单介绍,并对一个简单的通信协议进行建模和分析,提出了今后着色Petri网发展的一个主要方向。     

Petri net models for the semi-automatic construction of large scale biological networks

For the implementation of the virtual cell, the fundamental question is how to model and simulate complex biological networks. During the last 15 years, Petri nets have attracted more and more attention to help to solve this key problem. Regarding the published papers, it seems clear that hybrid functional Petri nets are the adequate method to model complex biological networks. Today, a Petri net model of biological networks is built manually by drawing places, transitions and arcs with mouse events. Therefore, based on relevant molecular database and information systems biological data integration is an essential step in constructing biological networks. In this paper, we will motivate the application of Petri nets for modeling and simulation of biological networks. Furthermore, we will present a type of access to relevant metabolic databases such as KEGG, BRENDA, etc. Based on this integration process, the system supports semi-automatic generation of the correlated hybrid Petri net model. A case study of the cardio-disease related gene-regulated biological network is also presented. MoVisPP is available at .     

Coloured Petri net refinement specification and correctness proof with Coq

In this work, we address the issue of the formal proof (using the proof assistant Coq) of refinement correctness for symmetric nets, a subclass of coloured Petri nets. We provide a formalisation of the net models, and of their type refinement in Coq. Then the Coq proof assistant is used to prove the refinement correctness lemma. An example adapted from a protocol example illustrates our work.