A service-based architecture for dynamically reconfigurable workflows

In the last few years, business process management systems have been employed for handling information systems of ever increasing complexity. As a consequence, the adoption of modelling languages enabling smooth and seamless transitions among the various phases of the process lifecycle, the ability of exploiting coordination schema over distributed execution contexts and the support for dynamic evolution and reconfiguration have become software engineering issues of great importance. This paper proposes the use of PN-Engine, a decentralized Petri nets execution engine, as a business process enactment engine. PN-Engine, which is based on the Jini service architecture, supports the decentralized execution of process models specified as Petri nets (PNs) enhanced with modular constructs and offers suitable mechanisms for dealing with the aforementioned design issues. PN-Engine allows to deploy and enact a new version of an existing process model without requiring the stopping/removal of older instances that are still running. The paper presents a novel approach enabling a decentralized migration procedure where concurrent portions of older instances migrate asynchronously to the new process model. Advantages of the proposed approach are demonstrated by means of an example concerning a workflow for a wine-production process.     

Inheritance of behavior

One of the key issues of object-oriented modeling and design is inheritance. It allows for the definition of subclasses that inherit features of some superclass. Inheritance is well defined for static properties of classes such as attributes and methods. However, there is no general agreement on the meaning of inheritance when considering the dynamic behavior of objects, captured by their life cycles. This paper studies inheritance of behavior both in a simple process-algebraic setting and in a Petri-net framework. Process algebra is chosen, because it concentrates on behavior, while abstracting from the internal states of processes. The result of the algebraic study is a clear conceptual understanding of inheritance of behavior. It can be expressed in terms of blocking and hiding method calls. The results in the algebraic framework inspire the development of the concept of inheritance of behavior in the Petri-net framework. The Petri-net formalism allows for a graphical representation of life cycles of objects with an explicit representation of object states. In the Petri-net framework, four inheritance rules are defined that can be used to construct life cycles of subclasses from the object life cycles of given (super-)classes. These inheritance rules can be used to structure a design process and they stimulate the reuse of life-cycle specifications. It turns out that the combination of blocking and hiding method calls captures a number of important operators for constructing life cycles of subclasses from life cycles of superclasses, namely choice, sequential composition, parallel composition, and iteration. A small case study validates our approach to inheritance of behavior.     

一种结构化的工作流过程建模方法

提出了一种结构化的工作流过程建模方法,并给出了相应的过程建模算法和过程模型分析,从而证明了所提出的方法的有设性。     

Exterminating the Dynamic Change Bug: A Concrete Approach to Support Workflow Change

Adaptability has become one of the major research topics in the area of workflow management. Today's workflow management systems have problems dealing with both ad-hoc changes and evolutionary changes. As a result, the workflow management system is not used to support dynamically changing workflow processes or the workflow process is supported in a rigid manner, i.e., changes are not allowed or handled outside of the workflow management system. In this paper, we focus on a notorious problem caused by workflow change: the dynamic change bug (Ellis et al.; Proceedings of the Conference on Organizational Computing Systems, Milpitas, California, ACM SIGOIS, ACM Press, New York, 1995, pp. 10–21). The dynamic change bug refers to errors introduced by migrating a case (i.e., a process instance) from the old process definition to the new one. A transfer from the old process to the new process can lead to duplication of work, skipping of tasks, deadlocks, and livelocks. This paper describes an approach for calculating a safe change region. If a case is in such a change region, the transfer is postponed.     

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.     

Genetic process mining: an experimental evaluation

One of the aims of process mining is to retrieve a process model from an event log. The discovered models can be used as objective starting points during the deployment of process-aware information systems (Dumas et al., eds., Process-Aware Information Systems: Bridging People and Software Through Process Technology. Wiley, New York, 2005) and/or as a feedback mechanism to check prescribed models against enacted ones. However, current techniques have problems when mining processes that contain non-trivial constructs and/or when dealing with the presence of noise in the logs. Most of the problems happen because many current techniques are based on local information in the event log. To overcome these problems, we try to use genetic algorithms to mine process models. The main motivation is to benefit from the global search performed by this kind of algorithms. The non-trivial constructs are tackled by choosing an internal representation that supports them. The problem of noise is naturally tackled by the genetic algorithm because, per definition, these algorithms are robust to noise. The main challenge in a genetic approach is the definition of a good fitness measure because it guides the global search performed by the genetic algorithm. This paper explains how the genetic algorithm works. Experiments with synthetic and real-life logs show that the fitness measure indeed leads to the mining of process models that are complete (can reproduce all the behavior in the log) and precise (do not allow for extra behavior that cannot be derived from the event log). The genetic algorithm is implemented as a plug-in in the ProM framework.     

一种基于模式组件的工作流管理系统构建方法

从描述流程控制特征的工作流模式出发,提出了一种基于工作流模式的工作流模型,给出了先将工作流模式映射到工作流模式组件,再构建基于模式组件的工作流管理系统的方法。     

A probabilistic approach to modeling and estimating the QoS of web-services-based workflows

Web services promise to become a key enabling technology for B2B e-commerce. One of the most-touted features of Web services is their capability to recursively construct a Web service as a workflow of other existing Web services. The quality of service (QoS) of Web-services-based workflows may be an essential determinant when selecting constituent Web services and determining the service-level agreement with users. To make such a selection possible, it is essential to estimate the QoS of a WS workflow based on the QoSs of its constituent WSs. In the context of WS workflow, this estimation can be made by a method called QoS aggregation. While most of the existing work on QoS aggregation treats the QoS as a deterministic value, we argue that due to some uncertainty related to a WS, it is more realistic to model its QoS as a random variable, and estimate the QoS of a WS workflow probabilistically. In this paper, we identify a set of QoS metrics in the context of WS workflows, and propose a unified probabilistic model for describing QoS values of a broader spectrum of atomic and composite Web services. Emulation data are used to demonstrate the efficiency and accuracy of the proposed approach.     

Inheritance of Interorganizational Workflows: How to Agree to Disagree Without Loosing Control?

Internet-based technology, E-commerce, and the rise of networked virtual enterprises have fueled the need for interorganizational workflows. Although XML allows trading partners to exchange information, it cannot be used to coordinate activities in different organizational entities. Business-to-business processes are hindered by the lack of a common language to support collaboration. This paper describes the P2P (Public-To-Private) approach which addresses one of the most notorious problems in this domain: How to design an interorganizational workflow such that there is local autonomy without compromising the consistency of the overall process. The approach uses a notion of inheritance and consists of three steps: (1) create a common understanding of the interorganizational workflow by specifying the shared public workflow, (2) partition the public workflow over the organizational entities involved, and (3) for each organizational entity: create a private workflow which is a subclass of the relevant part of the public workflow. This paper shows that this approach avoids typical anomalies in business-to-business collaboration (e.g., deadlocks and livelocks) and yields an interorganizational workflow which is guaranteed to realize the behavior specified in the public workflow.     

基于PETRI网的工作流模型分析与应用

目前,工作流的建模和分析工具有很多,由于Petri网具有坚实的理论基础和易于使用的图形表示,因而是一种理想的建模和分析工具。论文着重讨论基于Petri网的工作流模型的分析技术,对其基本的过程和所涉及的问题进行了分析,尤其对模型正确性的判定等问题,进行了详细的阐述。在文章最后,将给出一个应用的实例:全国高校网上招生录取系统。     

ECA规则在工作流管理系统中的应用

针对工作流管理系统的实现复杂性及模型可靠性的验证问题,提出了一种结合工作流网和ECA规则来创建工作流管理系统的方法。这种基于ECA规则的工作流描述和执行机制较好地实现了工作流网模型的语义描述和控制的统一。通过建立基于ECA规则的工作流描述表,将ECA 规则引入到工作流路由机制中,灵活地控制了工作流的流程。通过事件触发和消息处理机制,工作流描述表处理可以被实际系统加以执行和控制。     

基于工作流的虚拟企业信息管理模型

现代企业生产环境随着生产的全球化已经跨越 了国界,进行全球范围内的资源优化配置是有效利用全球资源的理想方案, 虚拟企业正是在 此需求下产生的．由于虚拟企业的分布式特点,其信息管理不同于传统的本地的管理方式． 本文给出一个基于工作流的虚拟企业信息管理模型,此模型支持的异构环境是地理上分散的 ,涉及到不同的应用包,多平台、多协议和多种用户界面,为虚拟企业生产信息管理提出了 一种方案．     

工作流管理系统异常处理的方法与层次

工作流技术在信息处理领域的应用越来越受到重视,但应用中环境和用户要求的不断发展和变化需要工作流管理系统具有灵活的处理能力,工作流系统的异常处理正是要解决这种不断要求的变化。文章介绍了工作流异常处理的应用范围,总结了不同的应用方法,从系统的角度提出了工作流未来的异常处理层次,并在研究可适应性工作流技术方面进行了探讨。     

基于Petri网的流程挖掘算法设计与应用

讨论了利用Petri网对应用系统日志进行建模和分析的方法,给出一个日志过滤、简化及转换模型的方法,提出了一个基于Petri网的专家挖掘算法,其中专家是指对某个业务流程特别熟练的人.以广州地铁法律咨询流程为例,介绍了该流程的建模和模型的简化算法.使用该算法可以有效的对操作人员进行评估和考核,有利于资源的合理配置.最后,以法律咨询流程日志为基础进行了实验,实验结果表明,算法认准率达90%以上,且通过模型简化可有效减低算法时间复杂度.     

面向并行工程的产品设计过程管理的抽象模型

设计过程管理是企业新产品开发活动的一个重要组成部分,它关系着企业是否能够更好的产品,更快地抢占市场。通过仔细调研国内多家大中型国有企业的产品设计过程管理活动,以并行工程思想方法为指导,指出了一个产品设计过程管理的抽象模型。最后针对抽象模型的应用,提出了建立多级抽象层的方法。     

Comparison of selected algorithms for scheduling workflow applications with dynamically changing service availability

This paper compares the quality and execution times of several algorithms for scheduling service based workflow applications with changeable service availability and parameters. A workflow is defined as an acyclic directed graph with nodes corresponding to tasks and edges to dependencies between tasks. For each task, one out of several available services needs to be chosen and scheduled to minimize the workflow execution time and keep the cost of service within the budget. During the execution ofa workflow, some services may become unavailable, new ones may appear, and costs and execution times may change with a certain probability. Rescheduling is needed to obtain a better schedule. A solution is proposed on how integer linear pro- gramming can be used to solve this problem to obtain optimal solutions for smaller problems or suboptimal solutions for larger ones. It is compared side-by-side with GAIN, divide-and-conquer, and genetic algorithms for various probabilities of service unavailability or change in service parameters. The algorithms are implemented and subsequently tested in a real BeesyCluster environment.     

判断工作流Petri网模型结构变化兼容性的算法

动态适应性已成为在工作流管理系统领域的主要研究课题之一。当工作流的结构发生变化时,面临着如何保证新旧工作流之间的兼容性的问题。利用Petri网作为分析工具来研究工作流的结构变化,提出了一种生成变化区域的算法。经过分析,可以证明该变化区域是最小的,并证明了通过分析最小变化区域的特性可以解决整个工作流Petri网模型结构变化兼容性问题。