Verifying soundness of business processes: A decision process Petri nets approach

This paper presents a trajectory-tracking approach for verifying soundness of workflow/Petri nets represented by a decision-process Petri net. Well-formed business processes correspond to sound workflow nets. The advantage of this approach is its ability to represent the dynamic behavior of the business process. We show that the problem of finding an optimum trajectory for validation of well-formed business processes is solvable. To prove our statement we use the Lyapunov stability theory to tackle the soundness verification problem for decision-process Petri nets. As a result, applying Lyapunov theory, the well-formed verification (soundness) property is solved showing that the workflow net representation using decision process Petri nets is uniformly practically stable. It is important to note that in a complexity-theoretic sense checking the soundness property is computationally tractable, we calculate the computational complexity for solving the problem. We show the connection between workflow nets and partially ordered decision-process Petri net used for business process representation and analysis. Our computational experiment of supply chains demonstrate the viability of the modeling and solution approaches for solving computer science problems.     

SoftPM: a software process management system reconciling formalism with easiness

Various formal approaches to process modeling and analysis have been proposed. With the emerging importance of practicality in this field, easiness in adopting formal technology should be taken into account. In this paper, we propose a PSEE called SoftPM that is based on a high level Petri net formalism for process modeling. To overcome the difficulty in using this formalism, SoftPM exploits a multi-level modeling mechanism for the representation of software processes. SoftPM supports three different levels for process representation. They are cognitive, MAM net, and Pr/T net. Each level has different roles in SoftPM. The cognitive-level modeling provides the means of getting free from difficulties in manipulating the modeling formalism. MAM net takes the role of core modeling formalism in SoftPM. Finally, Pr/T nets support the low-level modeling formalism as an existing Petri-net class. Moreover, SoftPM offers various analysis techniques to aid managerial decision making, as well as conventional Petri-net analysis techniques. Using a Java-based thin client/server architecture, SoftPM smoothly supports execution at distributed heterogeneous platforms over the Internet.     

Development of context-aware workflow systems based on Petri Net Markup Language

The Petri Net Markup Language (PNML) is originally an XML-based interchange format for Petri nets. Individual companies may specify their process models in Petri nets and exchange the Petri nets with other companies in PNML. This paper aims to demonstrate the capabilities of PNML in the development of applications instead of an industrial interchange format only. In this paper, we apply PNML to develop context-aware workflow systems. In existing literature, different methodologies for the design of context-aware systems have been proposed. However, workflow models have not been considered in these methodologies. Our interests in this paper are to propose a methodology to automatically generate context-aware action lists for users and effectively control resource allocation based on the state of the workflow systems. To achieve these objectives, we first propose Petri net models to describe the workflows. Next, we propose models to capture resource activities. Finally, the interactions between workflows and resources are combined to obtain a model for the whole processes. Based on the combined model, we propose architecture to automatically generate context-aware graphical user interface to guide the users and control resource allocation in workflow systems. We demonstrate our design methodology using a health care example.     

Translating unstructured workflow processes to readable BPEL: Theory and implementation

The Business Process Execution Language for Web Services (BPEL) has emerged as the de facto standard for implementing processes. Although intended as a language for connecting web services, its application is not limited to cross-organizational processes. It is expected that in the near future a wide variety of process-aware information systems will be realized using BPEL. While being a powerful language, BPEL is difficult to use. Its XML representation is very verbose and only readable for the trained eye. It offers many constructs and typically things can be implemented in many ways, e.g., using links and the flow construct or using sequences and switches. As a result only experienced users are able to select the right construct. Several vendors offer a graphical interface that generates BPEL code. However, the graphical representations are a direct reflection of the BPEL code and not easy to use by end-users. Therefore, we provide a mapping from Workflow Nets (WF-nets) to BPEL. This mapping builds on the rich theory of Petri nets and can also be used to map other languages (e.g., UML, EPC, BPMN, etc.) onto BPEL. In addition to this we have implemented the algorithm in a tool called WorkflowNet2BPEL4WS.     

着色Petri网在工作流建模中的应用

工作流建模是工作流管理系统进行工作流管理所必不可少的一个环节。而Petri网以其严格的数学基础、成熟的分析方法和工具而日益得到广泛的应用。本文介绍了着色Petri网在工作流建模中的作用，然后对一个具体的业务流程分别用经典Petri网和着色Petri网建立了过程模型并进行了比较。     

Petri net-based process monitoring: a workflow management system for process modelling and monitoring

Nowadays business process management is becoming a fundamental piece of many industrial processes. To manage the evolution and interactions between the business actions it is important to accurately model the steps to follow and the resources needed by a process. Workflows provide a way of describing the order of execution and the dependencies between the constituting activities of business processes. Workflow monitoring can help to improve and avoid delays in industrial environments where concurrent processes are carried out. In this article a new Petri net extension for modelling workflow activities together with their required resources is presented: resource-aware Petri nets (RAPN). An intelligent workflow management system for process monitoring and delay prediction is also introduced. Resource aware-Petri nets include time and resources within the classical Petri net workflow representation, facilitating the task of modelling and monitoring workflows. The workflow management system monitors the execution of workflows and detects possible delays using RAPN. In order to test this new approach, different services from a medical maintenance environment have been modelled and simulated.     

Can I find a partner? Undecidability of partner existence for open nets

We study open nets as Petri net models of web services, with a link to the practically relevant language WS-BPEL. For those nets, we investigate the problem of operability which we consider as fundamental as the successful notion of soundness for workflow nets, i.e., Petri net models of business processes and workflows. While we could give algorithmic solutions to the operability problem for subclasses of open nets in earlier work, this article shows that the problem is in general undecidable.     

Petri网在商务工作流建模中的应用研究

在工作流建模研究中,Petri网是一类重要工具。对于跨机构的商务工作流来说,用基本Petri网建模往往会因为图幅规模过大和细节过多而使得其可读性下降。该文提出了一种活动/层次网(A/H-Nets)模型,并给出了建模过程和应用示例。模型通过引入复合位置和子网转移及过程转移的概念,来满足Petri网在不同层次上建模的需求。为了保证层次之间的一致性,文中给出了层次建模必须的子网(过程)替换规则。     

一种集成U—P的工作流建模方法与正确性分析

Petri网和统一建模语言UML是当前工作流建模领域两种非常流行、功能强大的建模工具。Petri网便于描述,可以动态地运行,但缺乏层次;UML可以完整、细致地刻画系统,但量化不够,缺乏有效、严密的分析工具与方法。本文整合两种建模方法的优点,提出一种集成U．P建模的方法,该方法能够有效地描述系统,实现系统的模块化和模型重用,还能够对系统进行严密的分析,通过对模型仿真,找出其缺,羔和不足。     

Petri网标记语言

Petri网标记语言（PNML）是一种基于XML语言的Petri网文件交换标准,用于实现Petri网工具的互操作性。综合介绍了PNML标准化进程和PNML的核心支撑技术,详细阐述了PNML体系结构各个组成部分及元模型中各个组成对象,借助PNK工具实现一个P／T网模型实例,根据元模型分析对应的PNML文件中的库所、变迁和弧等对象标签的含义,最后分析了PNML在工作流模型与矢量图转换等领域的研究状况,指出了下一步研究方向。     

时间约束Petri网及其可调度性分析与验证

时间约束Petri网(timing constraint Petri nets,简称TCPN)是一类重要的时间Petri网系统.对相关定义重新界定,丰富并完善了TCPN理论.针对变迁可调度原始定义的不足,首先给出了变迁的弱/强可调度的新定义及强可调度判定定理;然后对变迁的强可调度进行了拓展,提出了TCPN时间可调度的概念,并结合Petri网结构给出了TCPN时间可调度判定定理;最后对TCPN的相关特性进行了研究.TCPN对时间Petri网的研究工作将起到启发作用,并对实时系统的描述和建模工作具有一定的参考价值.     

WF-net模型到PNML的转换方法研究与实现

Petri网标记语言PNMI是一种基于XM工的支持不同Petri网工具之间文件交换的标准格式,对于解决不同Petri网变种之间的互操作性问题具有重要意义。工作流网WF-net是用于工作流系统建模和定性、定量分析的重要形式化技术之一。工作重点是将WF-net模型转换为PNML格式。首先,在标准PNML元模型的基础上,通过元素扩展提出WF-net的PNML元模型。然后,依据元模型,提出WF-net模型中各元素到PNMI格式的转换规则,包括起始/结束库所转换、四种触发器转换和四种分支/合并结构转换。最后设计并实现了WF-net描述到PNML描述自动转换的工具软件。这些工作为Petri网标准交换格式的制定做了有力的探索。     

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.     

YAWL: yet another workflow language

Based on a rigorous analysis of existing workflow management systems and workflow languages, a new workflow language is proposed: yet another workflow language (YAWL). To identify the differences between the various languages, we have collected a fairly complete set of workflow patterns. Based on these patterns we have evaluated several workflow products and detected considerable differences in their ability to capture control flows for non-trivial workflow processes. Languages based on Petri nets perform better when it comes to state-based workflow patterns. However, some patterns (e.g. involving multiple instances, complex synchronisations or non-local withdrawals) are not easy to map onto (high-level) Petri nets. This inspired us to develop a new language by taking Petri nets as a starting point and adding mechanisms to allow for a more direct and intuitive support of the workflow patterns identified. This paper motivates the need for such a language, specifies the semantics of the language, and shows that soundness can be verified in a compositional way. Although YAWL is intended as a complete workflow language, the focus of this paper is limited to the control-flow perspective.     

基于时间约束Petri网的工作流可调度性分析

引入时间参数控制工作流高效执行是工作流技术研究的重要内容之一。在工作流的Petri网模型中引入时间参数,不仅可以对工作流中的活动进行时间约束,而且能建立相应的工作流时间约束Petri网模型。文中在分析该模型的时间约束和可调度性的基础上,提出了对工作流可调度性分析验证方法及其相应的算法,最后通过一个实例说明了分析验证的过程。     

基于工作流网的实时协同系统模拟技术

基于Petri网和工作流的概念，提出一种实时协同系统的形式化模拟与分析技术——逻辑工作流网，逻辑工作流网是抑制弧Petri网和高级Petri网的抽象和扩展，其变迁的输入／输出受逻辑表达式的约束，它与一般工作流网相比，能够在一定程度上缓解状态空间爆炸问题，且便于系统设计人员掌握和使用，该文分析了逻辑工作流网的若干性质及组合网的性质继承问题，并以网上企业销售系统为例，说明逻辑工作流网在实时协同系统模拟分析中的应用。     

Modeling production configuration using nested colored object-oriented Petri-nets with changeable structures

Configuring production processes based on process platforms has been well recognized as an effective means for companies to provide product variety while maintaining mass production efficiency. The production processes of product families involve diverse variations in manufacturing and assembly processes resulted from a large variety of component parts and assemblies. This paper develops a multilevel system of nested colored object-oriented Petri nets with changeable structures to model the configuration of production processes. To capture the semantics associated with production configuration decisions, some unique modeling mechanisms are employed, including colored Petri nets, object-oriented Petri nets, changeable Petri net structures, and net nesting. The modeling formalism comprises resource nets, manufacturing nets, assembly nets and process nets. The paper demonstrates how these net definitions are applied to the specification of production process variants at different levels of abstraction. Also reported is a case study in an electronics company. The system model is further analyzed with focus on conflict prevention and deadlock detection.     

基于Petri网的OA工作流模型研究

通过对办公自动化系统中的发文管理实例的描述,提出了一个基于Petri网的办公自动化工作流建模方法,该方法具有完全形式化的图形表示和坚实的数学基础,是一种工作流建模和分析的理想工具.在建立办公自动化系统的工作流模型的基础上,讨论了基于Petri网的工作流建模方法,并对该方法进行了正确性论证,表明该方法对于办公自动化系统的实用性和高效性.     

Petri网用于表示知识

本文研究了各种级别Petri网与模态逻辑之间的关系.Petri网的Enlogy是研究这些关系的基础.状况(case)和可达(Reachability)概念已经成功地用于以条件/事件(Condition/Event,简称C/E)网作知识表示.本文引用上述两个概念,使位置/变迁(Place/Transition,简称P/T)网和高级Petri网(High Level Petri Net,简称HLPN)可作知识表示.为了增强以 HLPN网作知识表示的能力,我们引用了状况变量和等价状况变量的概念.文中我们还以例子说明这些方法是可用的和有效的.