基于服务质量的Web服务发现研究与实现

随着Web服务的广泛应用,网络上提供的服务数量越来越多,如何在动态的环境下从海量的Web服务中找到满足用户需求的最优服务就成了Web服务应用急需解决的问题.介绍了服务质量的量化评价方法,并且在不改变传统Web服务架构的基础上,建立了一种基于服务质量的Web服务三层匹配模型,最后实验结果证明了该模型的可行性.     

Client-side selection of replicated web services: An empirical assessment

Replicating web services over physically distributed servers can offer client applications a number of QoS benefits, including higher availability and reduced response time. However, selecting the “best” service replica to invoke at the client-side is not a trivial task, as this requires taking into account factors such as local and external network conditions, and the servers’ current workload. This paper presents an empirical assessment of five representative client-side service selection policies for accessing replicated web services. The assessment measured the response time obtained with each of the five policies, at two different client configurations, when accessing a world-wide replicated service with four replicas located in three continents. The assessment’s results were analyzed both quantitatively and qualitatively. In essence, the results show that, in addition to the QoS levels provided by the external network and the remote servers, characteristics of the local client environment can have a significant impact on the performance of some of the policies investigated. In this regard, the paper presents a set of guidelines to help application developers in identifying a server selection policy that best suits a particular service replication scenario.     

An open framework supporting multimedia web services

With the rapid emergence of Web services, more and more Web services are published on the Internet as resources for Web application development. There may exist some relationships among different Web services, such as exact match, plug-in match, and irrelevant. In this paper, we discuss a set of requirements related to multimedia Web services, and propose a three-tier framework to establish an open environment supporting multimedia Web services, while partially implementing the requirements. This paper focuses on the design of the service broker tier that is essential for future Web services-oriented system design and integration and enabling Web services more transparent, interoperable, and fault-tolerate.     

WSB: a broker‐centric framework for quality‐driven web service discovery

Web service interfaces can be discovered through several means, including service registries, search engines, service portals, and peer‐to‐peer networks. But discovering Web services in such heterogeneous environments is becoming a challenging task and raises several concerns, such as performance, reliability, and robustness. In this paper, we introduce the Web Service Broker (WSB) framework that provides a universal access point for discovering Web services. WSB uses a crawler to collect the plurality of Web services disseminated throughout the Web, continuously monitor the behavior of Web services in delivering the expected functionality, and enable clients to articulate service queries tailored to their needs. The framework features ranking algorithms we have developed which are capable of ranking services according to Quality of Web Service parameters. WSB can be seamlessly integrated into the existing service‐oriented architectures. Copyright © 2010 John Wiley & Sons, Ltd.     

Web caching: A way to improve web QoS

As the Internet and World Wide Web grow at a fast pace, it is essential that the Web‘s performance should keep up with increased demand and expectations. Web Caching technology has.been widely accepted as one of the effective approaches to alleviating Web traffic and increase the Web Quality of Service (QoS). This paper provides an up-to-date survey of the rapidly expanding Web Caching literature. It discusses the state-of-the-art web caching schemes and techniques, with emphasis on the recent developments in Web Caching technology such as the differentiated Web services, heterogeneous caching network structures, and dynamic content caching.     

Recommending multimedia web services in a multi-device environment

In the last years, the Web community has shown a broad interest in Web services that handle multimedia contents. To improve the usability of these services different tools have been proposed in the literature, and in this context agent-based recommender systems appear to be a promising solution. However, the recommender systems presented in the past do not take into account, in their recommendation algorithms, the effect of the device exploited by the user, while it is clear that the same user shows a different behavior in the presence of different devices. This paper tries to give a contribution in this setting, in order to match more accurately user preferences and interests. In particular, a new agent-based system is proposed, whose architecture allows to compute recommendations of multimedia Web services, considering the effect of the currently exploited device. Some experimental results confirm the high quality of the recommendations generated by the proposed approach.     

Quality models for web services: A systematic mapping

ContextQuality of Service (QoS) is a major issue in various web service related activities. Quality models have been proposed as the engineering artefact to provide a common framework of understanding for QoS, by defining the quality factors that apply to web service usage.ObjectiveThe goal of this study is to evaluate the current state of the art of the proposed quality models for web services, specifically: (1) which are these proposals and how are they related; (2) what are their structural characteristics; (3) what quality factors are the most and least addressed; and (4) what are their most consolidated definitions.MethodWe have conducted a systematic mapping by defining a robust protocol that combines automatic and manual searches from different sources. We used a rigorous method to elicitate the keywords from the research questions and a selection criteria to retrieve the final papers to evaluate. We have adopted the ISO/IEC 25010 standard to articulate our analysis.ResultsWe have evaluated 47 different quality models from 65 papers that fulfilled the selection criteria. By analyzing in depth these quality models, we have: (1) distributed the proposals along the time dimension and identified their relationships; (2) analyzed their size (visualizing the number of nodes and levels) and definition coverage (as indicator of quality of the proposals); (3) quantified the coverage of the different ISO/IEC 25010 quality factors by the proposals; (4) identified the quality factors that appeared in at least 30% of the surveyed proposals and provided the most consolidated definitions for them.ConclusionsWe believe that this panoramic view on the anatomy of the quality models for web services may be a good reference for prospective researchers and practitioners in the field and especially may help avoiding the definition of new proposals that do not align with current research.     

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.     

一种支持QoS的语义Web服务发现框架研究

随着Web服务的广泛使用,Web服务的发现机制显得尤为重要.现有的Web服务发现方法,因缺乏对服务质量(QoS)的描述而难以为用户选择最佳服务.主要提出一种考虑QoS的语义Web服务发现框架,采用分类和反馈机制,及相应的匹配级别和过滤机制,以便用户查找到与自己需求最接近的服务,提高服务的查找率.     

QoS驱动的Web services动态计价机制研究

结合Web services的服务质量(QoS)因素和用户经验,对Web services的计价机制进行研究,提出一种QoS驱动的Web services动态计价模型,描述其计价过程,并给出相应的实现算法。通过对模型的简单实现,经测试这一计价模型在准确性和合理性上具有一定优势。     

基于Web Services的语义异构数据集成设计与实现

高校在信息化建设过程中积累了大量异构、异质的数据源,如何将这些异构数据源中相关的数据资源进行有效整合是当前急需解决的问题.为此,提出了一种新的基于Web Services的异构数据集成解决方案,利用Web Services技术在异构数据集成中的优势,采用虚拟数据库法设计思想,通过设计领域字典表及字段映射表,有效地解决了异构数据集成中最难解决的语义异构问题,并从数据模型转换、全局查询等方面阐述了该方案的可行性.实验结果表明,该方案具有可用性和高效性.     

Agent-based communities of web services: an argumentation-driven approach

The objective of this paper is to discuss how to sustain the growth of Web services through the use of communities. A community aims at gathering Web services with the same functionality independently of their origins, locations, and functioning. To make Web services more responsive to the environment in which they run and to be more flexible when managing communities, Web services are associated with software agents enhanced with argumentation capacities. This type of agents persuade and negotiate with other peers for the sake of letting their respective Web services reach their goals in an efficient way. Associating Web services with this type of agents allows them to select good communities and allow the communities to host the good Web services and to select the best ones for composite scenarios. Furthermore, this provides satisfactory solutions for three open problems: starvation (Web services refuse all the possibilities of joining communities), competition-free (Web services accept joining any community without being selective), and unfairness (always the same Web services members of a community are selected out of many others to participate in composite scenarios). In addition, the paper presents a formal and computational persuasive and negotiation protocol to manage the attraction and retainment of Web services in the communities and their identification for composite services.     

面向Web2.0的测试管理工具设计与实现

Web2.0时代带来了软件设计理念的全面更新.独占性的Web工具操作、多项目并行管理,用户主导的内容配置等新模式已经被广泛应用于软件设计和网络服务中.分析了目前测试管理工具的现状,提出了一种面向Web2.0的测试管理工具设计和实现方案.它扩展了用户主导应用的理念,实现灵活的定制功能提高了工具的项目适应性,利用AJAX技术增强了系统的交互能力,采用开放的Web Service接口技术实现了与软件生命周期中其它工具的协同操作,是将Web2.0时代新技术应用在测试管理工具设计和实现方面的一种探索.     

Design and implementation of a Secure Bandwidth Broker Discovery Protocol

Differentiated Services architecture definition lacks control level functionalities. One of the solutions proposed to fill this gap is Bandwidth Brokers (BB). Bandwidth Brokers are autonomous entities inside a network which is responsible for bandwidth management of the network along with other tasks. There is a lack of protocol for Bandwidth Brokers to discover other Bandwidth Brokers automatically. This study introduces a new Secure Bandwidth Broker Discovery Protocol (BBDP), which allows Bandwidth Brokers to automatically discover other Bandwidth Brokers. In this paper design principles, protocol details, working scenarios and implementation details of the BBDP protocol are presented.     

一种语义Web服务的多层次匹配方法

现有的语义Web服务发现方法大多采用匹配等级来筛选服务，查找到的服务粒度较大，也没有考虑服务质量。对OWL-S语言进行扩展，增加对QoS（服务质量）的描述，提出了五层次三阶段的多层次匹配过程，采用语义相似度进行匹配。实验结果表明该匹配方法能够保证查找的查准率和查全率。     

QoS-aware web services composition using GRASP with Path Relinking

In service oriented scenarios, applications are created by composing atomic services and exposing the resulting added value logic as a service. When several alternative service providers are available for composition, quality of service (QoS) properties such as execution time, cost, or availability are taken into account to make the choice, leading to the creation of QoS-aware composite web services. Finding the set of service providers that result in the best QoS is a NP-hard optimization problem. This paper presents QoS-Gasp, a metaheuristic algorithm for performing QoS-aware web service composition at runtime. QoS-Gasp is an hybrid approach that combines GRASP with Path Relinking. For the evaluation of our approach we compared it with related metaheuristic algorithms found in the literature. Experiments show that when results must be available in seconds, QoS-Gasp improves the results of previous proposals up to 40%. Beside this, QoS-Gasp found better solutions than any of the compared techniques in a 92% of the runs when results must be available in 100 ms; i.e., it provides compositions with a better QoS, implying cost savings, increased availability and reduced execution times for the end-user.     

Method of design and specification of web services based on quality system documentation

In this paper, we present a method for development and specification of web services based on the quality system documentation. The general assumption is that service oriented architecture is based on business services and these business services mostly correspond to exchanged documentation in a real business system. Documentation of a quality system is recognized in form of documents that describe business processes in a real business system and identify exchanged documentation with environment. Presented method uses documentation of quality system and documentation flow for web service specification. We developed the CASE tool for web service specification based on a new approach, and we compare it to other existing tools.

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.     

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。