A simulation-based approach for dynamic process management at web service platforms

Web services technology is being adopted as a viable deployment approach for future distributed software systems that enable business-to-business and business-to-consumer interactions across the open and dynamic internet environment. Recent research is focused on developing support technologies for web service discovery, on-demand service composition, and robust execution to facilitate web services based deployment of business processes. Developing techniques to cope with the volatile and open nature of the web during execution of composite services at the service platform is essential for delivering reliable and acceptable performance in this new process delivery framework. In this paper, we propose a simulation-based framework to guide scheduling of composite service execution. Online simulation of the dynamics of the open environment is used for scheduling service requests at the service platform. Comparison of the look-ahead simulation for different scheduling policies with the current execution state provides guidelines for service execution in order to cope with system volatility. We have implemented a prototype of the proposed framework and illustrate the feasibility of our approach with experimental studies.     

基于WS-BPEL 的Web 服务组合技术

随着Web服务技术的不断发展,越来越多的Web服务已经发布在互联网上。然而独立的Web服务功能通常有限,不能满足用户或企业实际应用的需求。因此,Web服务的组合显得越来越重要。介绍了Web服务组合和WS-BPEL的相关知识,使用最新的业务流程执行语言WS-BPEL描述业务流程,在J2EE集成开发环境下设计并实现了基于业务流程思想的贷款审批应用实例,在Web服务执行引擎Active BPEL上进行部署,对Web服务进行了有效的组合。     

Quality-of-service oriented web service composition algorithm and planning architecture

In the next few decades, it is expected that web services will proliferate, many web services will offer the same services, and the clients will demand more value added and informative services rather than those offered by single, isolated web services. As the result, the problem of synthesizing web services of high quality will be raised as a prominent issue. The clients will face the trouble of choosing or creating composition plans, among numerous possible plans, that satisfy their quality-of-service (QoS) requirements. Typical QoS properties associated with a web service are the execution cost and time, availability, successful execution rate, reputation, and usage frequency. In engineering perspective, generating the composition plan that fulfills a client’s QoS requirement is a time-consuming optimization problem. To resolve the problem in a timely manner, we propose a constraint satisfaction based web service composition algorithm that combines tabu search and simulated annealing meta-heuristics. As an implementation framework of the algorithm, we suggest a QoS-oriented web service composition planning architecture. The architecture maintains expert made composition schemas in a service category and assists the client as pure user to choose the one he/she wants to use. The main modules of the architecture are composition broker and execution plan optimizer. With the aid of the UDDI server, the composition broker discovers candidate outsourced web services for each atomic process of the selected schema and gathers QoS information on the web services. After that, the execution plan optimizer runs the web service composition algorithm in order to generate a QoS-oriented composition plan. The performance of the algorithm was tested in a simulated environment.     

comFlow:一个支持Web服务动态组合的原型系统

随着电子商务的迅速发展及用户对企业服务质量和及时信息反馈的要求越来越高,企业内及企业间各个系统之间的交互对企业的发展越来越重要.结合Web服务技术和流程建模技术,设计并初步实现了支持Web服务动态组合和执行的原型系统,给出了comFlow的系统架构,并描述它的组成部分.     

服务时间随机条件下服务组合质量分析

本文分析采用业务过程执行语言（BPEL2WS）描述的web服务组合的执行时间,给出在服务执行时间随机情况下,根据单个服务的执行时间概率分布密度和BPEL2WS模型的结构求解web服务组合执行时间的概率分布密度函数的算法。根据概率密度函数可以求得业务过程执行时间在任意时限内的概率,从而可以根据给定的概率条件优化组合服务,使得服务执行成本最低．最后通过一个应用实例验证了算法的有效性。     

Service Composition and Execution Plan Generation of Composite Semantic WEB Services Using Abductive Event Calculus

Web Service composition is indispensable, as a single web service cannot satisfy the complex functional requirement of a user. The two key challenges of semantic web service composition are the discovery of the most relevant atomic services from the composite semantic web services and by no means we can assure the execution of the composed atomic services in a proper order. In this work, these two challenges are addressed, and a novel architecture is proposed for atomic service discovery, composition and automatic plan generation for the proper execution of its candidate services. The proposed architecture takes the advantage of abductive event calculus that uses abductive theorem prover to generate a plan for the proper order of execution of the atomic services. The research has found that the plan generated by the proposed architecture is sound and complete.     

语义网服务中的本体综述

作为实现下一代Web的集成方案,语义网服务将语义Web技术和Web服务技术相结合,以支持Web服务的自动发现、选择、合成和执行.本体是语义网服务的理论基础.介绍了Web资源描述本体OWL和Web服务描述本体的概况,并对3种主流的Web服务语义描述框架进行对比分析,为语义网服务中本体的创建提供基础知识.研究了语义网服务中存在的各层次的本体异构问题,明确了语义网服务中本体集成的主要研究方向.     

A Web-Service based framework for analyzing and measuring business performance

The web services paradigm provides organizations with an environment to enhance B2B communications. The aim is to create modularized services supporting the business processes within their organization and also those external entities participating in these same business processes. Current web service frameworks do not include the functionality required for web service execution performance measurement from an organization perspective. As such, a shift to this paradigm is at the expense of the organizations performance knowledge, as this knowledge will become buried within the internal processing of the web service platform. This research introduces an approach to reclaim and improve this knowledge for the organization establishing a framework that enables the definition of web services from a performance measurement perspective, together with the logging and analysis of the enactment of web services. This framework utilizes web service concepts, DSS principles, and agent technologies, to enable feedback on the organizations performance measures through the analysis of the web services. A key benefit of this work is that the data is stored once but provides information both to the customer and the supplier of a web service, removing the need for development of internal web service performance monitoring.     

An extended XACML model to ensure secure information access for web services

More and more software systems based on web services have been developed. Web service development techniques are thus becoming crucial. To ensure secure information access, access control should be taken into consideration when developing web services. This paper proposes an extended XACML model named EXACML to ensure secure information access for web services. It is based on the technique of information flow control. Primary features offered by the model are: (1) both the information of requesters and that of web services are protected, (2) the access control of web services is more precise than just “allow or reject” policy in existing models, and (3) the model will deny non-secure information access during the execution of a web service even when a requester is allowed to invoke the web service.     

A monolithic approach to automated composition of semantic web services with the Event Calculus

In this paper, a web service composition and execution framework is presented for semantically -annotated web services. A monolithic approach to automated web service composition and execution problem is chosen, which provides some benefits by separating composition and execution phases. An AI planning method using a logical formalism, namely Abductive Event Calculus, is chosen for the composition phase. This formalism allows one to generate a narrative of actions and temporal orderings using abductive planning techniques given a goal. The functional properties of services, namely input/output/precondition/effects (IOPE) are taken into consideration in the composition phase and non-functional properties, namely Quality of Service (QoS) parameters are used in selecting the most appropriate solution to be executed. The repository of OWL-S semantic web services are translated to the Event Calculus axioms and the resulting plans found by the Abductive Event Calculus Planner are converted to graphs. These graphs can be sorted according to a score calculated using the defined quality of service parameters of the atomic services in the composition to determine the optimal solution. The selected graph is converted to an OWL-S file which is executed consequently.     

Web服务核心支撑技术:研究综述

随着电子商务的迅速崛起,基于Web的应用模式迅速发展,Web应用从局部化发展到全球化,从B2C(business-to-customer)发展到B2B(business-to-business),从集中式发展到分布式,Web服务成为电子商务的有效解决方案.Web服务是一个崭新的分布式计算模型,是Web上数据和信息集成的有效机制.Web服务的新型构架,Web服务的高效执行方式,Web服务与其他成熟技术的有机结合以及Web服务的集成是解决现实应用问题的重要技术.从Web服务研究的不同侧面对其进行了综述,阐述了Web服务的基本概念,分析了当前Web服务的主要研究问题及其核心支撑技术,概括了Web服务中的数据集成技术、Web服务的组合、语义Web服务、Web服务发现,Web服务安全,P2P(Peer-to-Peer)新型计算环境下的Web服务解决方案和网格服务等方面的研究内容,并对这些技术进行了总结,结合已有的研究成果,展望了Web服务未来的研究方向及其面临的挑战.     

Service-oriented smart home applications: composition, code generation, deployment, and execution

A smart home usually has a variety of devices or home appliance, instead of designing software for a specific home, this paper proposes a service-oriented framework with a set of ontology systems to support service and device publishing, discovery of devices and their services, composition of control software using existing control services that wrap devices, deployment, and execution of the composed service in an computing environment, monitoring the execution, and recovery from device failure. The ontology systems specify semantic information about devices, services, and workflows used in various smart home, and users can compose and recompose services for their specific needs. New devices, workflows, and services can be added into ontology. Most of the steps in this process can be automated including code generation. For example, service composition will be carried out in three steps: abstract workflow design, function construction, and device discovery, and different codes can be generated for different computing platforms such as Java and Open Services Gateway initiative environments. In this way, a variety of smart home can be constructed rapidly using the framework by discovery and composition using existing services and workflows. This paper illustrates this framework using a media control example to illustrate the ontology, discovery, composition, deployment, execution, monitoring, and recovery.     

Eine Dienstgüte unterstützende Webservice-Architektur für flexible Geschäftsprozesse

Web services as a technology to enable distributed business processes gain in importance. However, the support of Quality of Service (QoS) is crucial in this context. Thus, we present an integrated web service architecture with comprehensive QoS support. The architecture we introduce in this paper supports the assessment of web services to assure that only web services will be used in critical business processes that satisfy the requirements defined by the user. The selection and execution of a certain web service depends on its QoS-properties that must be guaranteed in Service Level Agreements (SLAs). The compliance with SLAs is monitored by the system as well. Furthermore we introduce a prototypical implementation of our web service architecture.     

动态Web服务合成中的服务选择算法研究

为了提高服务合成效率并更好的适应动态变化的应用环境,提出了基于流程修改的服务合成方案,使得复合服务的执行与服务发现过程并行化。提出了基于QoS属性的服务选择算法,该算法能够实现服务执行时选择服务,在考虑综合QoS信息及时间因素的基础上,通过不断更新用户需求来进行服务选择,提高了服务合成效率。实验结果表明,该选择算法可以获得满足用户需求且最优的服务,很好的保证了服务的可靠执行。     

Web Service Diagnoser Model for managing faults in web services

Reliability is an important criterion to facilitate extensive deployment of web service technology for commercial business applications. Run-time monitoring and fault management of web services are essential to ensure uninterrupted and continuous availability of web services. This paper presents WISDOM (Web Service Diagnoser Model) a generic architecture for detecting faults during execution of web services. Policies have been proposed to describe the intended behavior of web services and faulty behavior would be detected as deviations or inconsistencies with respect to the specified behavior. The model proposes the use of monitoring components in service registries and service providers to detect run-time faults during publishing, discovery, binding and execution of web services. An independent fault diagnoser is proposed to coordinate the individual monitoring components and also act as a repository for the specified web service policies. The proposed model has been tested with a sample web service application and the results obtained are presented.     

A semantical framework to engineering WSBPEL processes

Web services promise the interoperability of various applications running on heterogeneous platforms over the Internet, and are gaining more and more attention. Web service composition refers to the process of combining Web services to provide value-added services, which has received much interest in supporting enterprize application integration. Industry standards for Web Service composition, such as WSBPEL, provide the notation and additional control mechanisms for the execution of business processes in Web service collaborations. However, these standards do not provide support for checking interesting properties related to Web Service and process behavior. In an attempt to fill this gap, we describe a formalization of WSBPEL business processes, that adds communications semantics to the specifications of interacting Web services, and uses a formal logic to model their dynamic behavior, which enables their formal analysis and the inference of relevant properties of the systems being built.