具有全局质量保障的Web服务组合研究

随着面向服务架构（SOA）的开发技术不断成熟,Internet上涌现出功能相同或相似的Web服务集合越来越大,如何从这些集合中选出满足用户质量（QoS）的组合Web服务是目前国内外学者研究的热点问题。针对保证组合服务的质量（QoS）全局最优问题,基于图的理论构建服务组合模型,并在此模型上提出相应的服务选择算法,保障选择的组合服务的质量（QoS）全局最优。     

Web service selection algorithm based on principal component analysis

Existing Web service selection approaches usually assume that preferences of users have been provided in a quantitative form by users. However, due to the subjectivity and vagueness of preferences, it may be impractical for users to specify quantitative and exact preferences. Moreover, due to that Quality of Service (QoS) attributes are often interrelated, existing Web service selection approaches which employ weighted summation of QoS attribute values to compute the overall QoS of Web services may produce inaccurate results, since they do not take correlations among QoS attributes into account. To resolve these problems, a Web service selection framework considering user’s preference priority is proposed, which incorporates a searching mechanism with QoS range setting to identify services satisfying the user’s QoS constraints. With the identified service candidates, based on the idea of Principal Component Analysis (PCA), an algorithm of Web service selection named PCA-WSS (Web Service Selection based on PCA) is proposed, which can eliminate the correlations among QoS attributes and compute the overall QoS of Web services accurately. After computing the overall QoS for each service, the algorithm ranks the Web service candidates based on their overall QoS and recommends services with top QoS values to users. Finally, the effectiveness and feasibility of our approach are validated by experiments, i.e. the selected Web service by our approach is given high average evaluation than other ones by users and the time cost of PCA-WSS algorithm is not affected acutely by the number of service candidates.     

基于差异演化算法的QoS全局最优动态Web服务选择

QoS全局最优动态Web服务选择是服务组合中的一个难题。基于差异演化算法,设计一种用于解决该问题的DE-GODSS算法。算法的主要思想是将问题表示为一个带QoS约束的多目标服务组合优化问题,通过理想点的方法将多目标向单目标转化,然后利用差异演化算法的智能优化原理进行算法设计及求解,最终产生一组满足约束条件的优化服务组合流程集。理论分析证明DE-GODSS算法的时间复杂度优于已有的多目标遗传算法,且实验结果表明该算法的收敛速度优于已有的多目标遗传算法。     

动态QoS数据驱动的可靠Web服务选择

基于服务质量(QoS)的Web服务最优选择是一个热点问题。高度动态的QoS数据导致QoS模型的不确定性,对可靠的Web服务选择构成巨大的挑战,该文提出动态QoS数据驱动的可靠Web服务选择(DQoS_RSS)。首先利用均值标准差刻画QoS数据的效益和风险,提高QoS描述的准确度;接着建立不确定服务Skyline集,缩小搜索空间,提高选择效率;借鉴优劣解距离法(TOPSIS),设计2种Web服务选择算法,获得体现用户需求的最优服务。另外,介绍2种QoS模型转换器,以及能够适应QoS动态变化的QoS模型自适应调整机制。最后,实验分析验证了该方法的优越性和高效性。     

基于Sub Web Service服务组合方法

在当前Web服务动态组合研究的基础上,提出了一种基于Sub Web Service的混合Web服务组合方法。结合静态与动态服务组合方法,将动态生成的服务组合计划描述保存在缓冲池中,当用户使用该组合服务时,系统将会在缓冲池中搜寻此服务组合,并为请求调用它。在组合算法中提出了基于Sub Web Service的组合算法,将多输入多输出的Web服务分解为多输入单输出的Sub Web服务执行服务组合。在避免重复动态组合服务的基础上,减轻了Web服务在组合过程中对多输出接口的依赖性,提高了系统服务效率。     

QoE/QoS driven simulated annealing-based genetic algorithm for Web services selection

In order to improve the efficiency and effect of Web service selection, an algorithm named quality of experience (QoE)/quality of service (QoS) driven simulated annealing-based genetic algorithm (QQDSGA) is given to achieve Web services selection efficiently with excellent QoE. QQDSGA includes two parts: QoE/QoS driven composite Web services evaluation model and simulated annealing-based (SA-based) genetic algorithm for Web services selection. Simulations show that when used in Web service selection, QQDSGA is better than genetic algorithm (GA) and SA in efficiency and is more satisfied in effect than no customer feedback.     

支持事务机制的Web服务组合QoS属性预测方法

该文提出了一种支持事务机制的Web服务组合QoS属性预测方法。分析了事务异常处理策略及其对组合服务执行流程的影响,定义了支持事务机制的组合服务描述模型,并基于此模型提出了组合服务QoS属性预测算法。实验证明该文方法在对具有事务机制的组合服务进行预测时,准确度优于已有的工作流预测方法,具有较好的可行性和有效性。     

A cloud service composition method using a trust‐based clustering algorithm and honeybee mating optimization algorithm

One of the most critical issues in using service‐oriented technologies is the combination of services, which has become an important challenge in the present. There are some significant challenges in the service composition, most notable is the quality of service (QoS), which is more challenging due to changing circumstances in dynamic service environments. Also, trust value in the case of selection of more reliable services is another challenge in the service composition. Due to NP‐hard complexity of service composition, many metaheuristic algorithms have been used so far. Therefore, in this paper, the honeybee mating optimization algorithm as one of the powerful metaheuristic algorithms is used for achieving the desired goals. To improve the QoS, inspirations from the mating stages of the honeybee, the interactions between honeybees and queen bee mating and the selection of the new queen from the relevant optimization algorithm have been used. To address the trust challenge, a trust‐based clustering algorithm has also been used. The simulation results using C# language have shown that the proposed method in small scale problem acts better than particle swarm optimization algorithm, genetic algorithm, and discrete gbest‐guided artificial bee colony algorithm. With the clustering and reduction of the search space, the response time is improved; also, more trusted services are selected. The results of the simulation on a large‐scale problem have indicated that the proposed method is exhibited worse performance than the average results of previous works in computation time.     

Privacy-aware RBAC model for web services composition

Web services collaborative environments are highly automatic, dynamic, and heterogeneous. These characteristics always lead to high risks of services for interaction participants. Hence, it becomes one of the most important things to guarantee that the private information in cross-domain services is not illegally collected, used, disclosed or stored when the Web services are required to combine secure composition. This paper proposes the privacy-aware role based access control model for Web services composition (WSC-PRBAC), which provides protection for private data of users in composite service. The element services are divided into local services and outside services. Because the local service is authorized by users, it is exactly different from other services in the composition. To avoid sending private information to other outside services directly, we define global roles to help access these data in local service. Using global roles can realize a more strict control of the private data. In the end, the experiment and analysis of the proposed model show its and efficiency.     

Flexible user-centric service selection algorithm for Internet of Things services

In Internet of Things (IoT), the similar functional services are evolving in different quality of services (QoS) due to the widespread deployment of spatially distributed things on dynamic networks through the web. Therefore, the user involvement in service selection systems becomes a vital role to enhance the system performance by taking into account of subjective factors. This paper proposes a flexible QoS-based service selection algorithm (FQSA) which mainly targets to the users to be able to give their subjective preferences in an easy and friendly manner. The FQSA algorithm selects the services based on subjective information provided by the service consumers and objective information supported by the service providers. It adopts artificial neural network backpropagation algorithm to find the objective factors and applies similarity aggregation method to evaluate the creditability of the user subjective factors which have already been evaluated by ontological reasoning with the help of proposed QoS ontology. The comparative study and experimental results show that our FQSA algorithm is superior to other service selection approaches.     

基于服务计算的服务组合研究

通过分析现有Web服务组合系统的组合方式及特点,将服务计算引入到Web服务组合领域,提出了基于服务计算的Web服务组合系统方法,设计了基于服务计算的服务组合模型。通过松散耦合的服务组合模型来实现Web服务组合,可为服务消费者提供一个适当的、开放的、按需配置的安全的Web服务组合环境。     

A location-aware hybrid web service QoS prediction algorithm

Quality-of-service (QoS) describes the non-functional characteristics of Web services. As such, the QoS is a critical parameter in service selection, composition and fault tolerance, and must be accurately determined by some type of QoS prediction method. However, with the dramatic increase in the number of Web services, the prediction failure caused by data sparseness has become a critical challenge. In this paper, a new hybrid user-location-aware prediction based on WAA (HUWAA) is proposed. The implicit neighbor search is optimized by incorporating location factors. Meanwhile, the ability of the improved algorithms to solve the data sparsity problem is validated in experiments on public real world datasets. The new algorithms outperform the existing IPCC, UPCC and WSRec algorithms.     

基于语义Web服务的智能电信业务模型

该文针对电信业务领域用户需求多样化的实际情况,将互联网领域语义Web服务模型进行完善,提出了基于语义Web服务的智能电信业务模型。在模型中,设计了电信业务领域本体库,实现了电信业务领域知识的共享;提出了基于本体的用户个性数据库,利用本体的天然推理特性加强对用户个性的挖掘;引入了智能代理,将用户从浩淼的服务选择中解放出来。设计了语义转换XSLT代码生成模块提高了语义Web服务描述效率。该模型已经在实际的测试环境中得到验证,最后以流媒体业务为例,说明了该模型的工作原理。     

基于定性多用户偏好的Web服务选择

随着Web服务数量逐渐增多,出现了许多服务提供者提供功能相同或相似服务的情况.如何在一些功能相似或相同的服务集合中,根据用户对服务质量的需求选出更符合用户要求的服务,是当前研究人员普遍关心的课题.本文提出一种定性的服务选择方法,用来解决涉及多个用户的Web服务选择问题.各用户对服务质量的需求被表示为偏好.提出的算法将能够综合考虑各个用户的偏好,使选出的服务尽可能满足大部分用户的偏好要求,并给出了一个实例说明该算法的应用.实验结果表明了算法的有效性.     

基于Java语言的Web服务的动态发现与调用研究

Web服务是一个崭新的分布式计算模型,它的研究重点是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。为了充分发挥Web服务的灵活性,用户必须能够动态地发现和调用Web服务。动态发现Web服务的研究目标是服务发现的高效率和自动化。在此使用Java的开放源码包uddi4j,wsdl4j和Apache Axis 2来实现Web服务的动态发现与调用的方法。该方法实现了Web服务与Java技术的有机结合,为更高效率的应用Web服务提供一种思路。     

利用新的模糊免疫分类器的评价模型设计

随着Web服务数量的增加,根据Web服务的多维Qos属性度量Web服务质量成为研究热点之一。提出了一种利用模糊免疫网络记忆分类器的Web服务Qos评价。在该评价中首先结合SOA中Web服务描述给出了Web服务QoS评价模型。然后提出了一种新的人工免疫分类算法——FAINMC,利用该算法利用该算法对大量的Web服务实现准确、高效的分类。通过每类记忆细胞反应的特征得到相对应服务等级,最后使用模糊隶属度和百分法得到了反应Web服务质量优劣评价值。通过原型系统对模拟Web服务属性数据进行测试,表明该方法优选出QoS值尽可能大,QoS向量分量的特征分量一致性好的Web服务。     

运用备份服务位置和概率QoS模型的Web服务组合算法

针对工作流服务数的增加过程中最初规划的潜在成本较高以及很多服务组合算法可靠性不足等问题,提出了一种利用备份服务位置和概率服务质量（QoS）模型的服务组合算法。该算法计算服务集群的QoS优化选择,为每个服务包含足够数量的备份服务,且考虑了备份服务位置,以便在单个故障点上进行评估。由于这些备份服务分布均匀,防止了任务失败的发生。对于服务选择问题,采用一种改进的多目标优化（MOO）算法,利用聚类和QoS模型来计算可行解集合。仿真实验采用JMETAL 3.1框架,评估备份服务位置的收益以及算法的可靠性。结果表明,相比于其他MOO算法,提出的算法可靠性更高,从备份服务位置所获得的收益更高。