Hybrid Metaheuristics Web Service Composition Model for QoS Aware Services

Recent advancements in cloud computing (CC) technologies signified that several distinct web services are presently developed and exist at the cloud data centre. Currently, web service composition gains maximum attention among researchers due to its significance in real-time applications. Quality of Service (QoS) aware service composition concerned regarding the election of candidate services with the maximization of the whole QoS. But these models have failed to handle the uncertainties of QoS. The resulting QoS of composite service identified by the clients become unstable and subject to risks of failing composition by end-users. On the other hand, trip planning is an essential technique in supporting digital map services. It aims to determine a set of location based services (LBS) which cover all client intended activities quantified in the query. But the available web service composition solutions do not consider the complicated spatio-temporal features. For resolving this issue, this study develops a new hybridization of the firefly optimization algorithm with fuzzy logic based web service composition model (F3L-WSCM) in a cloud environment for location awareness. The presented F3L-WSCM model involves a discovery module which enables the client to provide a query related to trip planning such as flight booking, hotels, car rentals, etc. At the next stage, the firefly algorithm is applied to generate composition plans to minimize the number of composition plans. Followed by, the fuzzy subtractive clustering (FSC) will select the best composition plan from the available composite plans. Besides, the presented F3L-WSCM model involves four input QoS parameters namely service cost, service availability, service response time, and user rating. An extensive experimental analysis takes place on CloudSim tool and exhibit the superior performance of the presented F3L-WSCM model in terms of accuracy, execution time, and efficiency.     

QCWS: an implementation of QoS-capable multimedia web services

QoS (Quality of Service), which defines service quality such as latency, availability, timeliness and reliability, is important for web applications that provide real-time information, multimedia content, or time-critical services. Many web applications are best implemented by servers with a guaranteed server processing capacity. In this research, we study the QoS control issues using the current Web services standards. We propose a QoS-capable Web service architecture, QCWS, by deploying a QoS broker between Web service clients and providers. The functions of the QoS broker module include tracking QoS information about servers, making selection decisions for clients, and negotiating with servers to get QoS agreements. We have implemented a QCWS prototype using IBM WSDK, enhanced with simple QoS capabilities. We have measured the performance running under different service priorities.     

基于FAHP与规划图融合的Web服务组合方法

近年来,随着云计算的发展,越来越多的服务被发布在网上。如何将不同的Web服务组合在一起并使其满足功能性需求和非功能性需求成为了一个研究难点。Web服务质量(Quality of Service,QoS)感知的Web服务组合问题属于NP难问题。为了解决这个问题,文中提出一种融合FAHP与改进Graphp lan算法的方法(FAHP and Improved Graphplan,FIGP)。首先,根据用户偏好使用模糊分析层生成服务的综合QoS;其次,在Graphplan向前扩展中,使用动态阈值对竞争力较差的服务进行剪枝,在保留关键服务的同时降低了时间复杂度;最后,在Graphplan向后搜索阶段,在满足功能性需求的前提下选择综合QoS最好的服务加入到组合中。实例分析和实验结果表明,与普通的Graphplan,Skyline及其他方法相比,FIGP不仅较好地提高了服务组合的质量,而且显著缩短了程序的执行时间。     

Dynamic execution planning for reliable collaborative business processes

Collaborative business processes, implemented and carried out via web services and enabling dynamic interaction among organizations, are becoming more indispensable to competitiveness in the global market. As dynamic collaboration prevails, the quality of service (QoS) of collaborative processes becomes more important. A critical requirement in cases where processes involve long-term activities is to guarantee successful completion within time constraints. In this study, we developed a methodology for dynamic planning of web service execution that imparts reliability to collaborative business processes. In order to ensure that processes successfully execute within time constraints and at minimum cost, the proposed method dynamically modifies execution plans at run-time by means of fault-tolerance techniques. Since generation of an execution plan of minimum cost while guaranteeing successful completion is classified as an NP-hard problem, a heuristic algorithm was developed. Additionally, to compare the proposed algorithm’s performance with those of the branch-and-bound method and the genetic algorithm (GA), a set of experiments was conducted.     

基于可信QoS的路径查找及负载均衡策略研究

Web服务是云计算中资源调用的有效方式。单一Web服务功能往往有限,只能完成特定任务。服务组合则可以将多种Web服务形成有效的调用序列,实现更为强大的功能。服务发布量以及服务请求量的迅速激增带来了新的安全问题。首先,现有的服务组合方案均以服务质量(QoS)为依据进行Web服务选择,但服务质量通常由服务发布者提供,存在服务发布者发布虚假QoS值诱骗用户的欺诈现象;其次,传统的服务组合方案只生成一条最优路径,当恶意请求持续访问时,会造成某服务节点瘫痪,甚至整个服务组合系统失效。因此,针对服务质量恶意欺诈的问题,文章提出一种可信的QoS计算模型,根据Web服务发布者的信用综合评估服务质量;针对单一最优路径无法满足大量请求的问题,文章提出一种路径发现和负载均衡的多路径方法。仿真结果表明,文章提出的方法不仅能提高服务组合的成功率,满足用户的需求,而且能找到更多的服务组合方案执行。     

一种基于QoS的Web服务智能动态组合模型

针对当前Web服务数量剧增以及Web服务QoS综合评价不合理而导致Web服务组合效率和效用不高的问题,改进了Web服务组合中QoS计算模型,利用综合变权法动态调整每个Web服务多个属性的权值,并采用改进的粒子群算法来解决服务动态组合中QoS全局优化的问题.实验结果表明,该模型能够合理的选择和组合众多功能相同的服务,提高...     

Functionality Aware Dynamic Composition of Web Services

The composition of the web service is a common technique to attain the best results of complex web tasks. The selection of appropriate web services, linking those services in the action flow and attaining the actual functionality of the task are the important factors to be considered. Even though different frameworks and methods have been proposed to dynamically compose web services, each method has its advantage and disadvantage over the other. Most of the methods give much importance to the Quality of Service (QoS) but fail to achieve the actual functionality after composition. This paper proposes a functionality-oriented composition technique for composing web services. Moreover, this method helps reach the extreme functionality of each web service in the composition towards customer satisfaction. Apart from considering the overall QoS of every single service, the non-functional parameters associated with these services are also considered for achieving the expected functionality. Each of these non-functional parameters has a vital role in the functional performance of the web service. The web services that satisfy the non-functional requirements are chosen to form the composition to attain the best performance. The list of services in the proposed composition method is different from the conventional one, which is composed based on the overall QoS. The non-functional parametric values, the QoS of each web service and the overall QoS after composition are evaluated for the proposed method and experimentally analyzed to prove their advantage over the others.     

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。     

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。     

用于科技基础条件平台的服务合成研究与应用

Web服务之间的交互是面向服务的体系结构（Service-Oriented Archimcmre,SOA,也称为面向服务架构）中的关键问题。单个Web服务提供的功能往往不能完全满足用户的实际需求．将多个Web服务进行合成实现功能更为强大的服务是SOA必须要解决的问题之一。分析了Web服务合成的研究现状,介绍了Web服务合成方式的分类和商业流程执行语言BPEL4WS,给出了“科技基础条件平台应用服务支撑系统”项目中SOA的设计方案．描述了Web服务合成的关键步骤。该研究成果成功地应用于科技基础条件平台应用服务集成之中,并已通过科技部的前期验收     

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.     

Semantic web service composition testbed

A huge amount of web services are deployed on the Web, nowadays. These services can be used to fulfill online requests. Requests are getting more and more complicated over time. So, there exists a lot of frequent request that cannot be fulfilled using just one web service. For using web services, composing individual services to create the added-value composite web service to fulfill the user request is necessary in most cases. Web services can be composed manually but it is a too tedious and time consuming task. The ability of automatic web service composition to create a new composite web service is one of the key enabling features for the future for the semantic web. There are some successful methods for automatic web service composition, but the lack of standard, open, and lightweight test environment makes the comparison and evaluation of these composition methods impossible. In this paper we propose an architecture for a light weight and scalable testbed to execute, test and evaluate automatic web service composition algorithms. The architecture provides mandatory components for implementing and evaluation of automatic web service composition algorithms. Also, this architecture provides some extension mechanisms to extend its default functionalities. We have also given reference implementations for web service matchmaking and composition. Also, some scenarios for testing and evaluating the testbed are given. We have found that the performance of the composition method will dramatically decrease as the number of web services increases.     

An experience report on developing an automated web services platform

Web services have attracted significant industry interest as a low-cost and flexible technology alternative to distributed object and proprietary message-oriented methods for delivery of on-demand business processes, enabling intra-organizational systems integration, and in the long term, development of dynamic inter-organizational process networks that may revolutionize B2C and B2B e-commerce. Exploiting this latent potential of web services technology requires the development of automated techniques for scalable and reliable service composition and execution in web service platforms. In this paper, we summarize our experience in developing an architectural framework for web services platforms, called Integrated Service Planning and Execution architecture (ISP & E). The use of recent advances in AI planning, learning and semantic web technologies for service composition, reliable service execution, transaction synthesis, and model-driven deployment of services is discussed. Furthermore, we discuss implications for and research issues in the development of web services based systems to aid e-business.     

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.     

基于领域本体的可信服务组合

针对现有Web服务组合方法缺乏对服务自身属性信任问题的深入考虑,服务组合过程可信需求无法得到保障,提出了一种基于领域本体的可信Web服务组合方法。将服务的非功能属性分为服务质量、服务信任和服务上下文三个主要方面,并采用本体构建工具Protégé构建原子服务本体,利用推理机FaCT++对原始服务集进行本体推理过滤;引入了融合本体推理过滤的Web服务架构;提出了基于层次任务网络(hierarchical tasknetwork,HTN)规划法的可信服务组合算法。仿真实验表明:与传统的组合方法相比,该方法可有效提高服务组合的效率和成功率。     

QoS全局最优的多目标Web服务选择算法*

针对现有方法的不足,提出一种基于QoS全局最优的多目标动态Web服务选择算法。在给出动态服务组合模型的基础上,以“抽象服务规划”为输入,以用户的非功能性需求为全局约束,将动态服务选择问题转换为一个带QoS约束的多目标服务组合优化问题;利用多目标蚁群算法,多个目标函数被同时优化并产生一组满足约束条件的Pareto优化解。通过运用实验与基于多目标遗传算法的Web服务选择算法进行对比,证明了该方法的可行性和有效性。     

QoS可信的服务组合技术研究*

现有基于QoS的服务组合方法通常假定QoS数据可信,然而这种假设很难保证,虚假的服务对于服务组合实现的影响常常是致命的。针对该问题,提出一种考虑QoS可信的服务组合方法。分析了QoS来源,建立了相应的系统结构,划分了信任级别,根据社会交往方式量化了直接经验和间接经验在可信判断中的作用,并以此构建QoS的计算模型,设计了相应的算法。最后,通过仿真实验,将考虑可信的服务组合方法与未考虑可信的传统组合方法进行了比较,前者体现出明显的优越性,从而表明提出的方法在性能和执行效率上是可行的。     

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.     

基于QoS和多级索引的Web服务发布订阅

发布订阅机制有利于实现对大规模Web服务的主动管理,提出了基于QoS的Web服务发布订阅模型和系统架构,设计了基于QoS和多级索引的Web服务匹配算法。Web服务的QoS属性和订阅的属性约束所形成相应的匹配关系构成模型的关键;将发布的Web服务及其QoS和服务订阅一起生成过滤矩阵,通过属性约束覆盖可以减少重复匹配;按QoS属性类型对发布的Web服务建立多级索引,生成属性到服务的映射,可以实现服务订阅的快速匹配。实验结果表明,该Web服务发布订阅系统比传统方法有较大提升,能够适应于大规模分布式Web服务管理。