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1.
单个资源的服务往往不能满足任务需求,而多个服务的组合却可以派生出新的服务。为此,模拟迷宫求解的思路,设计了一套通用服务组合算法,将分布式资源提供的可用服务看作为迷宫中的条条道路,而将服务组合方案看作为连接迷宫入口和出口的一条通路,通过服务与服务、服务与需求之间的功能性关联,自动生成满足任务需求的服务组合方案。模拟实验验证了方法的有效性。 相似文献
2.
Towards efficiency of QoS-driven semantic web service composition for large-scale service-oriented systems 总被引:1,自引:0,他引:1
Quality-of-Service (QoS) performance guarantee for service-oriented systems (SOS) has become a critical problem. With the
increasing number of offered services comes the challenge of efficiently building large-scale SOS to meet the required QoS
criteria. Optimization of QoS-driven semantic Web service composition is known to be NP-hard. We address the efficiency issue
by developing a polynomial time algorithm (QDA) for shortest sequence composition. We use dynamic programming to find service
candidates for each execution. When all the services are searched, we use a depth-first trace back to derive the execution
plan. We have tested our approach under Web-scale demands 20,000 services and 150,000 semantic concepts. In comparison with
existing approaches, our experimental results show that QDA can be used to solve large-scale service composition problem effectively
and efficiently with QoS guarantee. 相似文献
3.
Walid Fdhila Marlon Dumas Claude Godart Luciano García-Bañuelos 《Software and Systems Modeling》2014,13(2):599-619
A composite service is usually specified by means of a process model that captures control-flow and data-flow relations between activities that are bound to underlying component services. In mainstream service orchestration platforms, this process model is executed by a centralized orchestrator through which all interactions are channeled. This architecture is not optimal in terms of communication overhead and has the usual problems of a single point of failure. In previous work, we proposed a method for executing composite services in a decentralized manner. However, this and similar methods for decentralized composite service execution do not optimize the communication overhead between the services participating in the composition. This paper studies the problem of optimizing the selection of services assigned to activities in a decentralized composite service, both in terms of communication overhead and overall quality of service, and taking into account collocation and separation constraints that may exist between activities in the composite service. This optimization problem is formulated as a quadratic assignment problem. The paper puts forward a greedy algorithm to compute an initial solution as well as a tabu search heuristic to identify improved solutions. An experimental evaluation shows that the tabu search heuristic achieves significant improvements over the initial greedy solution. It is also shown that the greedy algorithm combined with the tabu search heuristic scale up to models of realistic size. 相似文献
4.
一种高效的服务组合优化算法 总被引:1,自引:0,他引:1
随着功能性属性相同而非功能性属性各异的Web服务的大量涌现,如何在服务组合业务流程中为各个任务选择相应的组件服务以达到组合服务的QoS(quality of service)最大化,并在此基础上满足不同用户的需求,已成为了国内外研究的热点.由于该问题的复杂性(NP-hard),目前存在的大多数方法都并不十分适合需要相对精确、实时决策的Web服务组合系统.因此,本文提出了一种基于凸包构建的组合服务优化算法(CM-HEU)用以解决QoS感知的服务组合优化问题.CM-HEU首先通过对组合服务中的每组任务进行凸包构建,以减少搜索空间.然后通过对初始解向量的多次升级和一次降级操作以达到全局优化的目标.实验表明:相对于现阶段存在的一些主流方法,CM-HEU不仅能得到一个比较理想的结果,并且具有良好的效率. 相似文献
5.
服务组合是快速构造增值服务应用的有效途径.现有的组合服务选择模型基于单个需求的假设,而在实际应用中,需求是大量的且在较小时间范围内认为是多个需求同时到达.这些需求在服务调用上的交集导致它们竞争或者共享使用某些服务,使得当前的服务组合方法无法有效应对此类场景.提出面向多需求的服务组合模型与算法.考虑到服务资源的独占及共享特性以及多个评价要素间的决定性优先关系,给出基于冲突避免调度和优先级别的评价方法.在此基础上针对遗传算法制定多需求权衡策略,提出面向多需求可满足性折中的服务组合方法.实验结果表明该方法可保证多个需求的可满足性之间的均衡,通过改进编码能够高效获得较优结果.与目前可能的其他策略相比,该方法对可用服务在数量、质量方面的不同情况表现出更优的适应性. 相似文献
6.
The application of biologically inspired algorithms to multimedia repurposing systems in heterogeneous network environments
is gaining importance due to its ability to adapt and customize multimedia content to frequently changing network environments.
This paper presents a biologically inspired proxy-based multimedia content adaptation system, which is used to repurpose multimedia
content dynamically for the transmission over heterogeneous networks and end devices. We use a series of repurposing proxies’
services in a chain fashion between the sender and multiple end devices. In order to find the appropriate chain of repurposing
services that satisfy the Quality of Experience (QoE) requirements, the proposed service selection algorithm uses the ant
colony metaphor. During the communication session, the algorithm uses biological foraging behavior inspired from ant agents
to find optimal service paths between the media sender and the destination. Experimental results demonstrate that the proposed
algorithm provides significant performance gain over traditional, state of the art selection algorithms and saves the average
delay. 相似文献
7.
Amina Bekkouche Sidi Mohammed Benslimane Marianne Huchard Chouki Tibermacine Fethallah Hadjila Mohammed Merzoug 《Service Oriented Computing and Applications》2017,11(2):183-201
Automated semantic web service composition is one of the critical research challenges of service-oriented computing, since it allows users to create an application simply by specifying the inputs that the application requires, the outputs it should produce, and any constraints it should respect. The composition problem has been handled using a variety of techniques, from artificial intelligence planning to optimization algorithms. However no approach so far has focused on handling three composition dimensions simultaneously, producing solutions that are: (1) fully functional (i.e., fully executable) by using a mechanism of semantic matching between the services involved in the solutions, (2) are optimized according to non-functional quality-of-service (QoS) measurements, and (3) respect global QoS constraints. This paper presents a novel approach based on a Harmony Search algorithm that addresses these three dimensions simultaneously through a fitness function, to select the optimal or near-optimal solution in semantic web service composition. In our approach, the search space is modeled as a planning-graph structure which encodes all the possible composition solutions for a given user request. To improve the selection process we have compared the original Harmony Search algorithm with its recently developed variants Improved Harmony Search (IHS) algorithm and Global Best Harmony Search (GHS) algorithm. An experimentation of the approach conducted with an extended version of the Web Service Challenge 2009 dataset showed that: (1) our approach is efficient and effective to extract the optimal or near-optimal composition in diverse scenarios; and (2) both variants IHS and GHS algorithms have brought improvements in terms of fitness and execution time. 相似文献
8.
大数据时代以多媒体计算为基础的跨媒体计算技术已成为信息技术研究的热点。但是,对跨媒体的获取、组合和应用仍缺乏有效的方法。提出了两种跨媒体组合方法。以开发跨媒体在线二叉树遍历课程为例。第一种方法以Web服务的模式,引用多种类型多媒体数据,将其以服务组合的方式进行拼接,从而构成跨媒体服务。第二种方法是基于本实验室团队自主研发的PAR平台中的"New SQL"技术与Apla语言程序,使用PAR平台的多媒体数据库技术实现对跨媒体数据的存储和检索,进而构成Apla语言程序,实现部署在云端的多媒体服务,有效地解决了跨媒体的组合与存储问题。 相似文献
9.
基于行为效果的服务可替换性分析 总被引:1,自引:0,他引:1
服务可替换性分析是服务无缝集成与协作领域的一个重要问题,通过形式化的分析方法验证替换前后服务组合效果是否一致,有助于实现服务的动态组合.现有研究针对服务内部的操作和操作序列是否一致对服务的可替换性进行分析,会缩小可替换服务的空间.基于服务执行时的触发条件和结果提出了服务可替换性的定量判定方法.该方法采用有色Petri网对服务行为进行建模,将服务执行时的触发条件和结果定义为服务的行为效果,给出了行为效果一致的概念,并结合Petri网变换理论实现对服务可替换度的计算.最后通过定理证明了方法的有效性,这种定量分析的判定方法对于服务替换的正确建立和替换后组合服务的可靠执行具有重要作用. 相似文献
10.
Web service composition is an inevitable aspect of Web services technology, which solves complex problems by combining available basic services and ordering them to best suit the problem requirements. Automatic composition gives us flexibility of selecting best candidate services at composition time satisfying QoS requirements; this would require the user to define constraints for selecting and composing candidate Web services. In this work, a Web service composition approach is presented in which a rich set of constraints can be defined on the composite service. The output of the framework is the schedule of Web service composition in which how and when services are executed is defined. The basic properties of the proposed approach is converting Web service composition problem into a constraint satisfaction problem in order to find the best solution that meets all criteria defined by user and providing semantic compatibility and composability during composition. 相似文献
11.
The delivery of multimedia content often needs the adaptation of the content in order to satisfy user constraints. With the
Digital Item Adaptation part, the MPEG-21 standard already defines a useful frame-work to handle this task. However, in modern
service-oriented architectures the functionality of adaptation is split over several services. Hence, the central instantiation
of a suitable service chain needs to tackle a complex multi-objective optimization problem. In this problem between content
choice and possible adaptations the current preference model in the MPEG-7/21 standard still lacks expressiveness. In the
course of this paper we demonstrate this shortcoming and how the integration of more powerful models can ease the instantiation
problem. Furthermore we explain how to efficiently evaluate preference trade-offs by evaluating skyline queries as currently
investigated in the field of information systems. As a running example we use preference-based content adaptation in a typical
media streaming application with Web services as basic modules. The contribution of our framework is to enable a central coordinator
to instantiate an executable service composition chain by integrating all needed Web services to adapt the multimedia content
in the best possible fashion in the sense of Pareto optimality.
This work was supported in part by the German Research Foundation (DFG) within the Emmy-Noether Program of Exellence. 相似文献
12.
Service composition enables users to realize their complex needs as a single request and it has been recognized as a flexible
way for resource sharing and application integration since the appearance of Service-Oriented Architecture (SOA). For each
of the needed individual services there may be many candidate services available presented by different vendors and with different
functional and non-functional properties such as Quality of Service (QoS). Approaches are needed to select candidate services
with various QoS levels according to user’s performance requirements meanwhile adapt to dynamic churn in grid environments.
This paper mainly focuses on adaptive management of QoS-aware service composition in grid environments and proposes an adaptive
algorithm for QoS-aware service composition (AQSC). In AQSC we model this problem as the Multi-Constrained Optimal Path selection
problem (MCOP) and use heuristic approach for service selection, then backup services set is introduced as an adaptive mechanism
so as to ensure the fulfillment of composite service when some candidate services fail or withdraw. Both theoretical analysis
and simulation results indicate that AQSC has high composition success rate, finish rate and low cost. 相似文献
13.
Ruben Verborgh Davy Van Deursen Erik Mannens Chris Poppe Rik Van de Walle 《Multimedia Tools and Applications》2012,61(1):105-129
Automatic generation of metadata, facilitating the retrieval of multimedia items, potentially saves large amounts of manual work. However, the high specialization degree of feature extraction algorithms makes them unaware of the context they operate in, which contains valuable and often necessary information. In this paper, we show how Semantic Web technologies can provide a context that algorithms can interact with. We propose a generic problem-solving platform that uses Web services and various knowledge sources to find solutions to complex requests. The platform employs a reasoner-based composition algorithm, generating an execution plan that combines several algorithms as services. It then supervises the execution of this plan, intervening in case of errors or unexpected behavior. We illustrate our approach by a use case in which we annotate the names of people depicted in a photograph. 相似文献
14.
服务选择算法是影响组合服务的QoS和服务组合性能高低的关键因素。针对将多维QoS属性加权聚合为一个目标函数进行优化的选择算法不能实质性地解决基于QoS的Web服务选择问题,采用改进的强度Pareto进化算法(SPEA2+)多目标优化求解该问题,设计了一种Web服务选择算法。该算法在满足声誉、可靠性和可利用性属性的约束下,同时最小化服务时间T和服务费用C,以产生Pareto最优解集。通过与运用SPEA2算法求解该问题的实验对比,表明了两算法所获取的Pareto最优解集中QoS属性T和C各均值各有优劣,用户可依据对T或C的偏好择优选择。 相似文献
15.
随着服务计算、云计算技术的迅速发展,具有相同或相似功能但服务质量(QoS)不同的可用服务已大规模部署在互联网上。如何从这些海量Web服务中为服务组合选择令人满意的服务成了一个重要的研究问题,其选择方法是影响组合服务的QoS 和服务组合性能高低的关键因素。为了解决该问题,研究者们已开发了许多服务选择方法以帮助用户选择合适的服务。针对近五年基于QoS的Web服务选择方法的新进展进行了综述。归纳了包括运用Skyline计算、协同过滤、优化算法、多属性决策支持理论和混合方法等一些典型的服务选择方法,讨论了各方法的优势和局限性,并根据当前研究现状,探讨了该领域的发展趋势和未来研究方向和挑战。 相似文献
16.
随着面向服务计算(Service-oriented Computing,SOC)的不断发展,基于服务质量(Quality of Service,QoS)的Web服务组合研究成为了必然趋势。鉴于QoS属性的多维性及相互矛盾性,提出将基于QoS的Web服务组合优化问题转化为多属性决策问题进行求解。采用折中系数 对每个组合服务实例到正负理想点的距离进行累加求和,最终得到一组最优服务排序结果,用户可以根据自身偏好进行选择。传统的多属性决策方法无法有效地处理大规模的组合服务搜索空间,因此,为了有效地解决Web服务组合优化这一NP难题,提出一种结合多属性决策方法和自适应遗传算法的新型优化算法来解决该问题。实验采用真实的QoS综合服务数据集进行验证,实验结果表明,该方法能够在较短时间内找到全局近似最优解,且解集的排序结果接近于实际的最优服务排序。同时,该方法对于解决大规模的Web服务组合优化问题具有良好的可伸缩性。 相似文献
17.
QoS-Driven Self-Healing Web Service Composition Based on Performance Prediction 总被引:2,自引:0,他引:2
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Web services run in a highly dynamic environment, as a result, the QoS of which will change relatively frequently. In order
to make the composite service adapt to such dynamic property of Web services, we propose a self-healing approach for web service
composition. Such an approach is an integration of backing up in selection and reselecting in execution. In order to make
the composite service heal itself as quickly as possible and minimize the number of reselections, a way of performance prediction
is proposed in this paper. On this basis, the self-healing approach is presented including framework, the triggering algorithm
of the reselection and the reliability model of the service. Experiments show that the proposed solutions have better performance
in supporting the self-healing Web service composition.
This work is supported by the National Natural Science Foundation of China under Grant No. 60773218. 相似文献
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