分布式工作流引擎的设计方法

分布式工作流技术是计算机应用领域的一个较新的研究方向,工作流引擎的分布执行是工作流技术发展的一种必然趋势.针对企业级的实际需求,提出一种分布式工作流引擎的体系结构,并对引擎结构的各部分功能进行了描述,以及对工作流引擎的执行过程进行了分析.最后将工作流引擎的设计思想应用到具体实例分析中.     

自适应分布式工作流引擎的研究与设计

目前,分布式工作流系统已经取代集中式系统成为工作流系统主流。针对当前分布式工作流应用中执行环境和需求的变化性,提出了一种基于MVC结构和中介者模式的自适应的分布式工作流系统框架。在该框架中,一方面,执行引擎动态迁入迁出;另一方面,系统对过程和活动两个粒度进行任务调度,从而提高系统对运行环境的适应性以实现分布式工作流系统的柔性和扩展性。     

一种用于无人机的分布式飞行控制系统设计①

分布式结构已广泛应用于高可靠航空电子设备的设计中。设计了一种基于控制局域网（CAN）的分布式飞行控制计算机,用于在执行飞行任务过程中无人机的飞行控制律解算和系统管理。根据无人机控制的实时性和可靠性需求,提出了一种CAN通信、双端口随机访问存储器（DPRAM）通信和控制任务相互配合的内部通信机制。实验表明根据该通信机制设计的通信方案完全满足无人机控制的实时性和可靠性要求,同时解决了分布式结构引入的数据延时问题。     

基于Web服务的工作流事务处理的研究与实现

事务处理是Web服务实现分布式信息集成的关键技术之一,利用工作流技术实现Web服务的事务处理是实现分布式事务的一种有效手段.提出一个能够处理分布式、异构应用下Web服务组合事务的模型,并详述Web服务事务在执行过程中抛出异常时,补偿事务的产生策略和执行机制.     

基于UML的HLA/RTI联邦执行管理的可视化建模

RTI是HLA体系结构中的重要组成部分,理解RTI所提供的各种服务函数之间的交互过程是个难点。该文运用了可视化建模语言UML对RTI的联邦执行管理进行了建模,提供了分析和理解RTI的新思路。该文介绍了新一代分布式仿真体系结构HLA的主要研究内容,阐述了RTI的功能和体系结构。对HLA／RTI的联邦执行管理机制作了重点分析,在Rational Rose软件平台上对其进行了可视化的建模,给出了联邦执行管理的时序图。     

DDBMS的进程结构和执行方式

本文简要介绍了三个有代表性的 DDBMS—R、POREL、分布式 INGRES—的进程结构和执行方式,讨论了它们对系统性能的影响,借以说明一般 DDBMS 的进程结构和执行方式及其对系统性能的影响。     

动态安全组播密钥管理结构的研究

介绍并分析了安全组播通信中安全问题和密钥管理的分布式管理、集中式管理以及分布式子组管理的方法结构和算法，并对现有基于树型结构的密钥管理结构中所使用的相关技术进行了集中的讨论，分析了它们的执行效率。     

基于HLA的仿真程序设计研究

高层体系结构HLA以其突出的互操作性和可重用性,成为当今分布式交互仿真系统结构标准,研究基于HLA的仿真程序设计方法对于分布式交互仿真系统的开发具有重要意义。该文从联邦创建到联邦退出,以程序设汁的角度,详细地剖析了联邦执行的整个生命周期过程,还分析了联邦执行的整个生命周期中联邦执行的各种状态以及联邦成员、联邦执行、RTI这三者之间的关系。根据联邦执行的生命周期过程,给出了联邦成员的应用程序框架,并且举例说明了HLA仿真程序设计的步骤和一般方法。     

基于MIDAS分布式多层系统执行效率的研究

讨论了基于MIDAS服务器的三层结构,分析了在分布式多层结构中影响系统效率的因素以及提高系统执行效率的一些方法。     

分布式工作流系统的柔性管理

柔性问题是当前工作流系统中的研究热点之一。讨论了分布式工作流系统的柔性管理问题。在模型定义中用工作流接口-工作流定义的结构替代传统的工作流定义,将工作流定义具体划分为预定义操作包和扩展定义操作包,实现了动态的功能自适应;在执行过程中动态进行注册和注销执行机,引入协调机和路由规则库,实现了可变的路径自适应。     

分布式工作流执行服务的设计与实现

工作流执行服务的实现方案是实施工作流技术最为关键的一个方面,工作流管理系统的应用特点决定了它必须与各种分布的、异构的应用进行通信或与其集成。为了给用户提供透明的工作流执行服务而隐藏工作流执行服务实现的复杂性,文章提出了一种具有三层层次结构的工作流执行服务实现方案,其中的分布式通信服务层由通信中间件实现,使开发者无需关心程序间通信的复杂性,从而将精力放在解决业务问题和优化业务逻辑方面,提高了应用开发的效率。     

基于多Agent与工作流的分布式ETL引擎的研究

针对传统ETL工具集中式执行方式的不足,提出了一种基于多Agent与工作流相结合的分布式ETL引擎的体系结构。该体系结构由一个主控引擎和多个执行引擎组成,执行引擎可自主地向主控引擎注册执行服务,并利用分布式计算和多线程并行计算技术,实现由多个执行引擎协同执行ETL工作流,从而提高整个系统的灵活性和吞吐率。实验结果表明,该引擎具有较好的可扩展性和负载平衡性能,并提高了执行效率。     

支持动态联盟的分布式工作流管理系统--AgentFlow

提出了一个支持动态联盟的工作流描述模型，在此基础上提出了一个基于Agent的分布式的软件体系结构，重点分析了基于多Agent的工作流管理系统中工作流的动态集成和工作流的执行。最后讨论了工作流的分布式协作监控。     

网格环境中基于移动Agent的工作流架构研究

传统的工作流架构有很多弱点,比如架构严重降低了系统性能,在动态环境中缺少灵活性。本文提出了一个集成了WebServices,网格,工作流和移动代理技术的分布式工作流架构。在这个架构中,我们可以通过移动代理间的通讯来达到工作流之间协同工作,而且这个架构增强了工作流的灵活性和可靠性。最后,以这个新的模型为基础实现了一个具体的工作流工作站。     

Exotica/FMDC: A workflow management system for mobile and disconnected clients

Workflow Management Systems (WFMSs) automate the execution of business processes in environments encompassing large numbers of users distributed over a wide geographic area and using heterogeneous resources. Current implementations allow the definition and controlled execution of complex and long lived business processes as the basis for an enterprise-wide collaborative system but, in most cases, the autonomy of the users is greatly restricted due to architectural and design considerations. In particular, existing systems are built around a centralized server. As a result, users need to maintain an uninterrupted connection with the server to perform the different tasks assigned to them. This is a severe restriction, especially when considering the emergence of mobile computing, and the increase in use of laptops and small computers which are connected to the network only occasionally and which will, undoubtedly, be the tool of choice for many users. This paper addresses the problem of supporting disconnected workflow clients in large workflow management systems while still preserving the correctness of the overall execution and allowing coordinated interactions between the different users regardless of their location.Recommended by: Daniel Barbara, Ravi Jain, Narayanan Krishnakumar     

基于CORBA的工作流管理系统的研究与实现

该文提出了一个基于CORBA的完全分布式的工作流管理系统框架,在系统进程执行的过程中,进程的定义可以进行动态修改,解决了Client/Server模式中服务器将成为应用处理过程中瓶颈的问题、服务器一旦出现差错则导致整个系统瘫痪的问题以及工作流一经定义就无法修改的弊端,从而克服了基于Client/Server模式的工作流管理系统的一个固有缺陷,使工作流管理系统向大规模、灵活的方向发展。     

A distributed server architecture supporting dynamic resource provisioning for BPM-oriented workflow management systems

Workflow management systems have been widely used in many business process management (BPM) applications. There are also a lot of companies offering commercial software solutions for BPM. However, most of them adopt a simple client/server architecture with one single centralized workflow-management server only. As the number of incoming workflow requests increases, the single workflow-management server might become the performance bottleneck, leading to unacceptable response time. Development of parallel servers might be a possible solution. However, a parallel server architecture with a fixed-number of servers cannot efficiently utilize computing resources under time-varying system workloads. This paper presents a distributed workflow-management server architecture which adopts dynamic resource provisioning mechanisms to deal with the probable performance bottleneck. We implemented a prototype system of the proposed architecture based on a commercial workflow management system, Agentflow. A series of experiments were conducted on the prototype system for performance evaluation. The experimental results indicate that the proposed architecture can deliver scalable performance and effectively maintain stable request response time under a wide range of incoming workflow request workloads.     

From Centralized Workflow Specification to Distributed Workflow Execution

Current workflow management systems fall short of supporting large-scale distributed, enterprise-wide applications. We present a scalable, rigorously founded approach to enterprise-wide workflow management, based on the distributed execution of state and activity charts. By exploiting the formal semantics of state and activity charts, we develop an algorithm for transforming a centralized state and activity chart into a provably equivalent partitioned one, suitable for distributed execution. A synchronization scheme is developed that guarantees an execution equivalent to a non-distributed one. This basic solution is further refined in order to reduce communication overhead and exploit parallelism between partitions whenever possible. The developed synchronization schemes are compared in terms of the number and size of synchronization messages.     

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.     

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.