一种基于知识树和约束的柔性活动动态细化方法

柔性工作流在应对业务建模过程中的动态不确定因素、提高工作流系统的柔性具有巨大的优势,然而,柔性活动的动态细化一直是柔性工作流建模和应用的一个难点。因此,提出一种基于知识树和约束的柔性活动动态细化方法。该方法以知识树的包含和泛化关系作为启发信息,以活动选取约束和时序约束作为指导和校验,实现柔性活动的动态细化。在介绍了知识树及其蕴含关系以及活动选取约束和时序约束规则的基础上,给出了柔性活动的动态细化算法,描述了活动选取校验和时序约束校验算法。最后给出了算法的实现和实例分析,其结果表明了所提方法的有效性,能够很好地解决柔性活动的细化问题。     

基于时间Petri网的工作流模型分析

工作流管理的最终目的是实现适当的人在适当的时间执行适当的活动.企业要获得竞争力,需要在工作流模型中考虑与业务过程相关的时间约束.一个考虑时间因素的工作流模型,需要在投入运行前进行时间规范与验证,以保证工作流执行的时间协调.通过为工作流网元素扩展时间属性,得到集成业务过程时间约束的工作流模型??时间约束工作流网(TCWF-nets).基于对业务活动的可调度性分析,提出了时序一致性验证方法,确保工作流执行中活动之间时间交互的安全性.在所附加的时间约束下,该可调度分析方法不仅能够检测某一给定工作流调度的时间可行性,还能对特定的实例给出一个最优调度,使工作流执行延迟最小.研究结果表明,该方法支持业务过程的时间建模与分析,对于丰富现有工作流系统的时间管理功能以及增强现存工作流软件对动态业务环境的适应性具有重要意义.     

MPGS: an interactive tool for the specification and generation ofmultimedia presentations

Multimedia presentations are composed of objects belonging to different data types such as video, audio, text and image. An important aspect is that, quite often, the user defining a presentation needs to express sophisticated temporal and spatial constraints among the objects composing the presentation. We present a system (called MPGS-Multimedia Presentation Generator System) which supports the specification of constraints among multimedia objects and the generation of multimedia presentations according to the specified constraints. The constraint model provided by MPGS is very flexible and powerful in terms of the kinds of object constraints it can represent. A large number of innovative features are supported including: asynchronous and simultaneous spatial constraints; components of interest and priority levels; motion functions. Obviously, the flexibility provided to the users requires the development of nontrivial techniques to check constraint consistency and to generate a presentation satisfying the specified constraints. We illustrate the solutions we have devised in the framework of MPGS     

基于时间约束Petri网的工作流动态一致性检验

工作流系统中的时间管理是工作流建模和分析的重要组成部分。支持动态修改是人们在实际应用中对工作流系统提出的新要求。文中在基于时间约束的Petri网模型基础上,根据时间约束推理规则,提出一种动态修改时间约束时检验工作流一致性的方法,从而丰富了工作流的时间管理功能。     

应用角色访问控制的工作流动态授权模型

形式化地描述了角色、用户、权限、任务单元、授权策略、授权约束等实体及其相互间的关系，提出将授权约束分为需求角色约束、需求用户约束、拒绝角色约束及拒绝用户约束，并在此基础上建立了授权约束的冲突检测规则．实现了授权流与工作流的同步，并通过授权约束的冲突检测确保了工作流的有效执行．文中模型具有全面性与实用性较强的特点．     

An analysis of expressiveness and design issues for the generalized temporal role-based access control model

The generalized temporal role-based access control (GTRBAC) model provides a comprehensive set of temporal constraint expressions which can facilitate the specification of fine-grained time-based access control policies. However, the issue of the expressiveness and usability of this model has not been previously investigated. In this paper, we present an analysis of the expressiveness of the constructs provided by this model and illustrate that its constraints-set is not minimal. We show that there is a subset of GTRBAC constraints that is sufficient to express all the access constraints that can be expressed using the full set. We also illustrate that a nonminimal GTRBAC constraint set can provide better flexibility and lower complexity of constraint representation. Based on our analysis, a set of design guidelines for the development of GTRBAC-based security administration is presented.     

On verification of nested workflows with extra constraints: From theory to practice

Workflows are used to formally describe processes of various types such as business and manufacturing processes. One of the critical tasks of workflow management is automated discovery of possible flaws in the workflow – workflow verification. In this paper, we formalize the problem of workflow verification as the problem of verifying that there exists a feasible process for each task in the workflow. This problem is tractable for nested workflows that are the workflows with a hierarchical structure similar to hierarchical task networks in planning. However, we show that if extra synchronization, precedence, or causal constraints are added to the nested structure, the workflow verification problem becomes NP-complete. We present a workflow verification algorithm for nested workflows with extra constraints that is based on constraint satisfaction techniques and exploits an incremental temporal reasoning algorithm. We then experimentally demonstrate efficiency of the proposed techniques on randomly generated workflows with various structures and sizes. The paper is concluded by notes on exploiting the presented techniques in the application FlowOpt for modeling, optimizing, visualizing, and analyzing production workflows.     

柔性化的产品开发工作流模型的研究

现有的工作流模型在支持非确定型业务和意外情况上存在着不同程度的局限性,为了提高产品开发工作流系统的动态适应性,提出了一种新的柔性化工作流模型ASD。文章给出了ASD的形式化定义,并在此基础上介绍了工作流系统的动态过程修改策略和工作流模型执行算法。     

分布式工作流中的柔性事务模型

描述了一种可以为分布式工作流提供事务支持的模型设计、并提出了一种柔性事务模型。给出了柔性事务的定义，然后描述了保证柔性事务被正确调度的可串行化正确性准则。该模型具有在多层工作流管理系统中处理分布式业务流程的能力。     

Contract-collaboration network method for modeling manufacturing resource control workflows

This paper presents contract-collaboration network (CC-Net) method that is developed to model manufacturing resource control workflows. The CC-Net is an object-oriented class diagram. It depicts the contract-collaboration relationships among the classes in a manufacturing system, with constraints. The CC-Net method uses a primitive modeling block called collaboration module by which the CC-Net is established systematically. This idea is very similar to that of the Lego® block toy. Unlike most workflow modeling methods, the CC-Net method views workflow modeling as a constraint satisfaction process. That is, describing the set of constraint recovery rules corresponding to the constraint violations is regarded as workflow modeling. The obtained set of workflow rules is free from process deadlock and considers all the events of triggering the workflow. We explore the use of the CC-Net method for the workflow modeling of a flexible manufacturing system.     

An architecture for workflow scheduling under resource allocation constraints

Research on specification and scheduling of workflows has concentrated on temporal and causality constraints, which specify existence and order dependencies among tasks. However, another set of constraints that specify resource allocation is also equally important. The resources in a workflow environment are agents such as person, machine, software, etc. that execute the task. Execution of a task has a cost and this may vary depending on the resources allocated in order to execute that task. Resource allocation constraints define restrictions on how to allocate resources, and scheduling under resource allocation constraints provide proper resource allocation to tasks. In this work, we provide an architecture to specify and to schedule workflows under resource allocation constraints as well as under the temporal and causality constraints. A specification language with the ability to express resources and resource allocation constraints and a scheduler module that contains a constraint solver in order to find correct resource assignments are core and novel parts of this architecture.     

Temporal logic programming for assembly sequence planning

A temporal-constraint logic programming framework for the specification and automatic verification and synthesis of assembly sequences is developed. The implemented tool is based on the formulated and derived precedence properties for a general mechanical assembly. This tool, called the Mechanical Assembly Sequence Satisfiability Checker (MASS-C), supports the use of a subset of temporal logic for assembly constraint specification. MASS-C provides the logic programming framework by which the designer can be relieved of the tedium of finding the assembly sequences, and the assembly sequence planning process manifests itself in the implicit modelling of assembly sequences by acquiring and formulating the set of correct and complete assembly constraints as a logic program. MASS-C implements a class of temporal expressions as predicates for logic programming of assembly constraints. It provides facilities to either verify an assembly sequence or synthesise all assembly sequences that satisfy the specified constraints composed as a logic program. Two examples illustrate the use of MASS-C for such verification and synthesis.     

基于图形展开及图形归约的过程模型验证方法

工作流过程模型是业务过程的形式化定义，在业务过程的分析、运行和重组方面起着关键性的作用．为了实现预期的业务目标，需要正确地定义工作流过程模型，它的正确性直接影响业务目标的实现，WfMS开始调度执行之前必须对其进行分析．针对大规模复杂应用的特点和业务过程执行的实际需要，对复杂工作流过程模型的正确性验证进行了研究；基于有向有环图(DCG图)详细讨论工作流过程模型的局部错误以及过程逻辑错误；给出了过程建模中避免错误的相关约束规则；另外了提出了一种新型的图形归约和图形展开相结合的验证方法及过程模型验证算法．     

一种支持柔性的工作流过程元模型

工作流管理系统的动态自适应能力在很大程度上取决于过程模型的动态支持能力。本文分析和讨论了过程模型的动态特性和工作流管理联盟WfMC定义的过程元模型。在此基础上,引入柔性工作流定义、同步器、变换器等新元素,改进和扩展过程定义元模型。改进和扩展后的过程元模型具有更大的柔性和重构性。由于引入了变换器,为增强过程元模型的智能性做了基础性工作。另外,对描述过程元模型的定义语言WPDL也做了改进和扩展。     

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。     

An incremental analysis for resource conflicts to workflow specifications

Workflow management technology helps modulizing and controlling complex business processes within an enterprise. Generally speaking, a workflow management system (WfMS) is composed of two primary components, a design environment and a run-time system. Structural, timing and resource verifications of a workflow specification are required to assure the correctness of the specified system. In this paper, an incremental methodology is constructed to analyze resource consistency and temporal constraints after each edit unit defined on a workflow specification. The methodology introduces several algorithms for general and temporal analyses. The output returned right away can improve the judgment and thus the speed and quality on designing.     

工作流时序约束模型分析与验证方法

为了解决工作流时间建模与时序一致性验证问题,以时序逻辑和模型检查为基础,提出了一种工作流时间建模与时序一致性验证方法.该方法用一阶逻辑描述工作流模型及其时间信息,用时序逻辑描述工作流的时序约束,用模型检查算法对时序约束进行验证与分析.该方法不是针对某一种时序约束提出来的,而是能够验证任何用时序逻辑描述的工作流时序约束.该方法还能够对未通过验证的时序约束提供工作流运行实例作为反例,帮助用户定位模型的问题.以一个工作流时间建模和时序一致性验证的实例证实了所提出方法的有效性.     

Constraint-based test generation for automotive operating systems

This work suggests a method for systematically constructing a software-level environment model for safety checking automotive operating systems by introducing a constraint specification language, OSEK_CSL. OSEK_CSL is designed to specify the usage constraints of automotive operating systems using a pre-defined set of constraint types identified from the international standard OSEK/VDX. Each constraint specified in OSEK_CSL is interpreted as either a regular language or a context-free language that can be checked by a finite automaton or a pushdown automaton. The set of usage constraints is used to systematically classify the universal usage model of OSEK-/VDX-based operating systems and to generate test sequences with varying degrees of constraint satisfaction using LTL model checking. With pre-defined constraint patterns and the full support of automation, test engineers can choose the degree of constraint satisfaction and generate test cases using combinatorial intersections of selected constraints that cover all corner cases classified by constraints. A series of experiments on an open-source automotive operating system show that our approach finds safety issues more effectively than conventional specification-based testing, scenario-based testing, and conformance testing.     

工作流管理系统的柔性技术研究与应用

工作流的柔性是指灵活、动态地处理变更和异常的能力,这种能力使得工作流管理系统能够满足企业业务流程不断变更的需求,以及适应市场和企业的发展。自20世纪90年代中期开始,在提高工作流管理系统的柔性方面进行了很多探索和研究,引起了极大关注。该文首先介绍柔性工作流的相关概念及方法,然后结合工作流可扩展模型和跳转返回机制来增强工作流的柔性,最后基于微软WWF（Windows Workflow Foundation）的开发平台,通过示例来演示由宿主动态更新业务流程。     

On Modeling and Verification of Temporal Constraints in Production Workflows

The dynamic nature of events, in particular business processes, is a natural and accepted feature of today’s business environment. Therefore, workflow systems, if they are to successfully model portions of the real world, need to acknowledge the temporal aspect of business processes. This is particularly true for processes where any deviation from the prescribed model is either very expensive, dangerous or even illegal. Such processes include legal processes, airline maintenance or hazardous material handling. However, time modeling in workflows is still an open research problem. This paper proposes a framework for time modeling in production workflows. Relevant temporal constraints are presented, and rules for their verification are defined. Furthermore, to enable visualization of some temporal constraints, a concept of “duration space” is introduced. The duration algorithm which calculates the shortest/longest workflow instance is presented. It is a generalization of two categories of algorithms: the shortest-path partitioning algorithm and the Critical Path Method (CPM). Based on the duration algorithm, the verification algorithm is designed to check the consistency of introduced temporal constraints.