Structural soundness of workflow nets is decidable

The problem of deciding whether a given workflow net is k-sound for some k?1 is known as structural soundness. We prove that structural soundness of workflow nets is decidable.     

The relationship between workflow graphs and free-choice workflow nets

Workflow graphs represent the main control-flow constructs of industrial process modeling languages such as BPMN, EPC and UML activity diagrams, whereas free-choice workflow nets are a well understood class of Petri nets that possesses many efficient analysis techniques. In this paper, we provide new results on the translation between workflow graphs and free-choice workflow nets.We distinguish workflow graphs with and without inclusive Or-logic. For workflow graphs without inclusive logic, we show that workflow graphs and free-choice workflow nets are essentially the same thing. More precisely, each workflow graph and each free-choice workflow net can be brought into an equivalent normal form such that the normal forms are, in some sense, isomorphic. This result gives rise to a translation from arbitrary free-choice workflow nets to workflow graphs.For workflow graphs with inclusive logic, we provide various techniques to replace inclusive Or-joins by subgraphs without inclusive logic, thus giving rise to translations from workflow graphs to free-choice nets. Additionally, we characterize the applicability of these replacements. Finally, we also display a simple workflow graph with an inclusive Or-join, which, in some sense, cannot be replaced. This shows a limitation of translating inclusive logic into free-choice nets and illustrates also a difficulty of translating inclusive logic into general Petri nets.     

Verification of workflow nets with transition conditions

Workflow management is concerned with automated support for business processes.Workflow management systems are driven by process models specifying the tasks that need to be executed,the order in which they can be executed,which resources are authorised to perform which tasks,and data that is required for,and produced by,these tasks.As workflow instances may run over a sustained period of time,it is important that workflow specifications be checked before they are deployed.Workflow verification is usually concerned with control-flow dependencies only;however,transition conditions based on data may further restrict possible choices between tasks.In this paper we extend workflow nets where transitions have concrete conditions associated with them,called WTC-nets.We then demonstrate that we can determine which execution paths of a WTC-net that are possible according to the control-flow dependencies,are actually possible when considering the conditions based on data.Thus,we are able to more accurately determine at design time whether a workflow net with transition conditions is sound.     

A method of workflow scheduling based on colored Petri nets

Effective methods of workflow scheduling can improve the performance of workflow systems. Based on the study of existing scheduling methods, a method of workflow scheduling, called phased method, is proposed. This method is based on colored Petri nets. Activities of workflows are divided into several groups to be scheduled in different phases using this method. Details of the method are discussed. Experimental results show that the proposed method can deal with the uncertainties and the dynamic circumstances very well and a satisfactory balance can be achieved between static global optimization and dynamic local optimization.     

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.     

A short note concerning lazy reduction rules for append

We show that informing a lazy evaluator that the APPEND operator is associative reduces the overall worst case performance from O(n²) to O(n).     

基于知识Petri网和归结规则的推理方法

本文提出了一种基于知识Petri网和归结规则的推理方法.通过知识Petri网描述命题逻辑知识库,将归结规则映射到知识Petri网上,根据库所和变迁的连接关系,定义了知识Petri网中的归结结构.利用归结结构,给出了基于知识Petri网的归结推理算法和扩展知识库的推理算法,并利用Wumpus实例验证了推理算法.该推理方法是可靠且完备的,能够利用知识Petri网的网络结构降低计算复杂性.     

Reduction rules for reset/inhibitor nets

Reset/inhibitor nets are Petri nets extended with reset arcs and inhibitor arcs. These extensions can be used to model cancellation and blocking. A reset arc allows a transition to remove all tokens from a certain place when the transition fires. An inhibitor arc can stop a transition from being enabled if the place contains one or more tokens. While reset/inhibitor nets increase the expressive power of Petri nets, they also result in increased complexity of analysis techniques. One way of speeding up Petri net analysis is to apply reduction rules. Unfortunately, many of the rules defined for classical Petri nets do not hold in the presence of reset and/or inhibitor arcs. Moreover, new rules can be added. This is the first paper systematically presenting a comprehensive set of reduction rules for reset/inhibitor nets. These rules are liveness and boundedness preserving and are able to dramatically reduce models and their state spaces. It can be observed that most of the modeling languages used in practice have features related to cancellation and blocking. Therefore, this work is highly relevant for all kinds of application areas where analysis is currently intractable.     

Property specifications for workflow modelling

Previously we provided two formal behavioural semantics for the Business Process Modelling Notation (BPMN) in the process algebra CSP. By exploiting CSP’s refinement orderings, developers may formally compare their BPMN models. However, BPMN is not a specification language, and it is difficult and sometimes impossible to use it to construct behavioural properties against which other BPMN models may be verified. This paper considers a pattern-based approach to expressing behavioural properties. We describe a property specification language PL for capturing a generalisation of Dwyer et al.’s Property Specification Patterns, and present a translation from PL into a bounded, positive fragment of linear temporal logic, which can then be automatically translated into CSP for simple refinement checking. We present a detailed example studying the behavioural properties of an airline ticket reservation business process. Using the same example we also describe some recent results on expressing behavioural compatibility within our semantic models. These results lead to a compositional approach for ensuring deadlock freedom of interacting business processes.     

Agent-based workflow management systems (WfMSs)

Workflow management systems (WfMSs) based on agent technology can cope with the rapidly evolving business environment better than most other systems as they are more flexible and open. In this paper we describe a possible architecture of such a system by means of our prototype WfMS called JBees. The combination of collaborating agents and the Coloured Petri Net (CPN)-formalism in JBees enables a flexible and adaptive system with the possibility of simulation, analysis, and monitoring of the process execution in order to identify potential inconsistencies and to provide appropriate information to the workflow administrator for the purpose of the process improvement.     

工作流模型正确性验证过程中的模型简化问题

将工作流概念映射到Petri网后得到的工作流网的合理性验证过程比较复杂,容易出现状态空间爆炸的问题,需要对工作流模型进行简化。文章将工作流模型的简化过程分为两个步骤,首先将工作流模型转化为经典Petri网,再对经典Petri网进行简化。对于自由选择网可以采用自由选择语义的规约方法进行简化,而对于非自由选择网可以结合自由选择语义的规约方法和标准的Petri网简化方法进行简化。     

Soundness verification for conceptual workflow nets with data: Early detection of errors with the most precision possible

A conceptual workflow model specifies the control flow of a workflow together with abstract data information. This model is later on refined by adding specific data information, resulting in an executable workflow which is then run on an information system. It is desirable that correctness properties of the conceptual workflow are transferable to its refinements. In this paper, we present classical workflow nets extended with data operations as a conceptual workflow model. For these nets, we develop a novel technique to verify soundness. An executable workflow is sound if from every reachable state it is always possible to terminate properly. Our technique allows us to analyze a conceptual workflow and to conclude whether there exists at least one sound refinement of it, and whether any refinement of a conceptual workflow model is sound. The positive answer to the first question in combination with the negative answer to the second question means that sound and unsound refinements for the conceptual workflow in question are possible.     

A novel general framework for automatic and cost-effective handling of recoverable temporal violations in scientific workflow systems

Due to the complex nature of scientific workflow environments, temporal violations often take place and may severely reduce the timeliness of the execution's results. To handle temporal violations in an automatic and cost-effective fashion, two interdependent fundamental issues viz. the definition of fine-grained recoverable temporal violations and the design of light-weight effective exception handling strategies need to be resolved. However, most existing works study them separately without defining a comprehensive framework. To address such a problem, with the probability based temporal consistency model which defines the range of recoverable temporal violations, a novel general automatic and cost-effective exception handling framework is proposed in this paper where fine-grained temporal violations are defined based on the empirical function for the capability lower bounds of the exception handling strategies. To serve as a representative case study, a concrete example exception handling framework which consists of three levels of fine-grained temporal violations and their corresponding exception handling strategies is presented. The effectiveness of the example framework is evaluated by large scale simulation experiments conducted in the SwinDeW-G scientific grid workflow system. The experimental results demonstrate that the example framework can significantly reduce the overall average violation rates of local temporal constraints and global temporal constraints to 0.127% and 0.167% respectively.     

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.     

基于Petri网化简技术的工作流模型正确性研究

为了更有效地对工作流模型进行分析验证，提出了一种基于Petri网化简技术的工作流模型正确性验证方法。在对各种工作流模型验证技术深入研究的基础上，通过对非自由选择网结构活性和有界性的分析，给出了针对Petri网中非自由选择部分的分析方法。在保持活性和有界性的前提下，给出了将活的且有界的非自由选择部分转化为自由选择部分的转化方法，从而将非自由选择的Petri网验证问题转化为自由选择Petri网的验证问题。通过一个例子说明了如何使用该文提出的方法来验证模型的正确性。     

规则和流程管理在纳税评估系统中的应用研究

为适应评估方法不断变化和灵活扩充的需要,通过引入ILog JRules业务规则引擎和InforFlow工作流,将评估方法逻辑转化为业务规则.利用业务规则引擎技术,在税务海量数据分析、复杂业务领域建模和多规则评估应用方面进行了探索,通过Ilog Jrules、InforFlow等技术的有机结合,建立了省级数据集中环境下的智能化纳税评估系统.将多种方法和模板以业务规则形式固化到系统中,实现了方法灵活配置和根据预警指标自动调用方法模板进行审核分析的目的.     

Partitioning rules for orchestrating mobile information systems

New mobile technologies such as Bluetooth or Wi-Fi suffer from many limitations and problems, especially when they are used in combination, whereas they are quite stable in small networks. The lack of specialised mobile middleware requires new methods in the design and execution of mobile information systems. We propose a two-phase approach to manage a mobile business process by partitioning a given workflow into several workflows, with each one governed by a controller. In the first phase, we introduce synchronisation tasks between different controllers. In the second phase, we create for each controller a local process view. Thanks to added tasks, the overall execution of all local workflows achieve the same result as the original one. The mobile scenario and the necessity for more automation lead us to choose the Business Process Execution Language for Web Services (BPEL4WS) as the language for the process definition.