基于超级账本的蚁群因子差分进化算法的可信服务组合优化

为了保障服务组合优化过程中的QoS数据的真实性,提出了一种基于超级账本平台的可信框架;同时为了提高服务组合的优化效率,提出了一种蚁群因子的差分进化算法的服务组合优化方法(ACOF-DE)。首先,在超级账本平台上部署相应节点,构建可信框架,保障候选服务的真实性;然后,将所提出的算法以智能合约的形式,在区块链上对服务组合的优化问题进行求解,使组合过程在可信的环境下执行。该算法通过引入多种蚁群因子,比如蚁群路径因子、最优蚁群因子、信息素因子以及基于蚁群因子的差分计算,帮助算法动态控制搜索空间、记录迭代过程中的关键信息,以提高算法优化能力。最后,通过仿真实验证明可信框架可以有效地保障数据的可信;ACOF-DE相比其他智能优化算法拥有更佳的优化效率。     

基于多粒度服务库的SOA参考模型及其应用

针对传统的面向服务架构中服务管理、发现、组合等效率较低的问题,通过分析面向服务架构中的粒度思想,提出一种基于多粒度服务库的面向服务架构参考模型.首先,讨论多粒度服务库的概念,并给出服务库的粒化算法;其次,对所提模型的总体结构特别是粒度计算引擎进行了详细的介绍,阐述粒度计算引擎的主要功能,给出一个基于多粒度服务库的服务发现算法;然后,提出一种基于多粒度服务库的服务组合算法,同时说明SOA参考模型的作用;最后,结合具体应用实例验证该模型的有效性.     

服务组合的代数规约

现有的服务组合描述途径不能有效地验证和测试组合正确性,针对这一问题,提出了一个代数规约方法,引入规约包机制扩展面向服务代数规约语言SOFIA以支持该方法。用代数规约单元描述服务系统中的各种实体,其中基调部分定义实体的语法和结构,公理部分定义其功能和行为特性。与一个服务相关的规约单元封装在一个包中或拆分在几个相互引用的包中,每个包形成一个命名空间。当多个服务组合在一起时,以这些服务的代数规约包为基础,一方面抽象地定义组合服务的交互过程和语义,形成描述服务组合实现方式的实现规约包;另一方面抽象地定义组合服务对外接口及其功能语义,形成描述组合服务需求的抽象规约包。在实现规约和抽象规约的双元结构基础上,进一步定义了实现规约和抽象规约之间必须满足的“实现”关系,证明了满足实现关系可以保证实现的正确性,从而为服务组合的可验证性和可测试性奠定了理论基础。最后结合实例分析阐述了用代数规约描述服务组合的抽象性、可表达性和可验证性。     

考虑执行可靠性的云制造服务组合算法

由于制造资源的调用与执行比计算资源要复杂得多,使得在云制造环境下的服务组合执行可靠性成为必须考虑的问题.为此,提出一种基于离散粒子群智能优化的、考虑执行可靠性的云制造服务组合算法.以概率密度函数描述服务可靠性,基于服务模型库动态生成云制造服务组合的工作流模型,基于语义实现服务匹配,通过离散变量粒子群优化算法计算出执行可靠性最优的云制造服务组合方案.最后以结构设计工作流模型为例,在不同服务实例规模、不同恶意服务占比情况下验证了其有效性和可靠性.实例结果表明,在恶意服务占比较高时,该算法仍能保持较高的服务执行可靠性.     

分布式服务网络中保证QoS的服务路由算法研究

服务组合可以通过组合网络上多种服务形成新的服务.针对服务组合的服务路径选择问题,提出在分布式服务网络中确保QoS的服务路由算法.其中,包括通过向量长度的方法合计多QoS约束的函数F以及瓶颈选择算法BNS(bottle-neck se-lection).BNS算法将请求的服务序列按瓶颈从小到大排列,按序进行特定的筛选,可以有效的减小候选图的规模,提高查找效率.最后的仿真证明,提出的服务路由算法达到了良好的成功率及提高了服务网络的负载量.     

基于柯西烟花算法的大规模服务组合优化

随着Web服务的日益丰富,如何动态地从大量候选服务集中选择出整体性能高的组合服务已成为服务组合优化领域亟待解决的问题。为稳定、高效地解决大数据集下的服务组合问题,提出一种柯西烟花算法。该算法在搜索过程中引入柯西变异算子增强了算法的全局搜索能力;采用精英候选策略有效降低了算法的时间开销。实验结果验证了该算法在处理大规模服务组合优化问题时的可行性和稳定性。     

基于业务抽象规划的分布式动态服务组合算法

异构系统间难以实现计算资源的灵活共享,制约分布式信息系统性能的提升,基于面向服务架构的Web服务技术,为异构系统计算资源共享提供了有效手段。为此,针对Web服务组合在集中式发布架构下单点故障和性能瓶颈问题,提出一种基于业务抽象规划的分布式动态服务组合算法。该算法根据组合规划结果对业务抽象规划库进行动态扩充,快速组合出满足需求的服务,逐步提高服务组合响应率。仿真结果表明,该算法在分布式环境下可减少服务请求过程中交互的信息量,降低请求响应时间,提高服务组合效率。     

P_MOEA:一种多目标决策辅助遗传算法用于服务组合QoS优化

在服务组合场景下,SLA约束下的服务组合优选是实现服务质量管理的重要基础之一.服务组合优选既是一个组合优化问题同时也是多目标决策问题,需要高效的算法以支持大规模的候选组合方案集合,同时也需要有效的评价模型来明确定义候选方案的优劣程度,从而为决策者提供支持.现有的服务组合优选方法多基于两种模型定义其优化目标:线性效用函数和Pareto最优.前者需要量化权重配置以定义效用函数,但是对于用户来说精确的量化权重配置是一个非常困难的任务,特别是在涉及到的QoS维度较多时;后者无需权重配置,将Pareto最优的skyline集合作为优化结果返回给用户,然而skyline集合的规模是不可控的,最优结果集的规模会随着问题的规模增大而显著增大,过大的最优结果集显然难以为决策者提供有效参考.针对上述传统方法的不足,在本文中,我们将PROMETHEE方法引入服务组合优选问题,结合Pareto和PROMETHEE两种评价模型,将skyline集合基础上的Top-k PROMETHEE最优方案作为优化目标,提出并实现了一个高效的遗传算法:PMOEA.算法可以针对大规模问题,高效地返回Top-k PROMETHEE最优组合方案集合,从而为进一步的决策提供有效的参考.我们实验验证了算法的效率和有效性.     

一种基于DSL的服务组合语言

针对大规模并发应用在组合服务中的服务调度问题,设计一种基于领域专用语言的服务组合语言,给出该语言的主要功能、构造过程和语言执行引擎的详细设计。该语言提供对Web服务组合过程的语义和语法描述,采用自顶向下的组合方式,能解决Web服务组合过程中的组合粒度控制和异构消息匹配等问题。     

面向领域的服务业务规范化组织模型及其关键技术研究

提出一种面向领域的服务业务规范化组织模型(SBSOM),旨在服务计算环境下针对应用领域中基于服务组合的业务应用系统构建需要,解决如何实现深入到业务层面对服务资源进行有效组织与管理,从而为操作相容组合和服务有效复用提供可靠性保障问题.在该模型的支撑下,基于领域业务本体通过对服务操作的可用性判定,生成服务的领域业务视图,从而完成服务自然面貌、功能面貌、到业务面貌的逐步抽象,全面的展现服务能力,并在以服务为粒度、基于功能对服务资源进行分类管理的基础上,进一步实现以操作为粒度、基于业务适用性组织服务资源.本文重点讨论了SBSOM模型的结构体系,并对服务业务规范化组织建模的关键技术进行了深入探讨,在最后通过实验对SBSOM模型的意义和有效性进行了分析与验证.     

基于服务簇和QoS的Web服务组合方法

针对海量的语义Web 服务组合中如何提高搜索速度和获得最优组合的问题,提出了一种基于服务簇和服务质量(QoS)的快速组合方法。利用预先建立的服务簇进行服务搜索,可以有效缩小搜索空间,降低语义比较的复杂度,快速得到候选服务集合。组合过程中基于服务的最优组合QoS值动态确定阈值进行服务过滤,可以获得多个最优组合。同时采用高效的冗余处理方法保证组合中冗余服务最少,并采用服务簇内部过滤的方法限制候选服务数量,解决了因组合过多造成的运行超时问题。基于海量服务库进行实验,结果表明,服务搜索效率比普通搜索方法可提高几十倍,服务过滤和冗余处理效果明显,可快速获得多个QoS最优的无冗余组合,并且在百万级服务库进行大层次深度的组合时仍可保证良好的运行性能。     

Dynamic web service composition based on OWL-S

Composing existing web services for enterprise applications may enable higher level of reuse. However the composition processes are mostly static and lack of support for runtime redesign. In this paper, we describe our approach to the extension of the OWL-S ontology framework for dynamic web service composition. We raise the level of abstraction and propose an abstract service layer so that web services can be com- posed at the abstract service level instead of the concrete level. Each abstract service is attached with an instance pool including all instances of the abstract service to facilitate fail-over and dynamic compositions.     

Automated and flexible composition based on abstract services for a better adaptation to user intentions

In recent years, the composition of loosely coupled services with the aim of satisfying the user intention is a widely followed research topic. The composition of services implies the ability to select, coordinate, interact, and interoperate existing services. This is considered as a complex task. This complexity is mainly due to the large number of available services and their heterogeneity as they are created by different organizations. This complexity is increased when services must be dynamically and automatically composed to meet requirements which are not satisfied by existing services. In fact, an approach for service composition must offer the potential to achieve flexible and adaptable applications, by selecting and combining services based of the request and the context of the user. In this perspective, different approaches have been developed for services composition. However, most of the existing composition approaches tend to be static and not flexible in the sense that they do not have the ability to adapt to user requirements.To overcome these challenges, we propose a composition approach in which the generation of the composition schema is performed at runtime through the use of abstract services provided at design time. The composition process that we propose takes as input a structure of user requirements materialized by a graph of intentions and enriches this graph to explicit the implicit relationships. The enriched graph is used to generate an initial composition schema by building the control flow and selecting the appropriate abstract services. The selection of these services is based on the semantic matching and the degree of semantic affinity between abstract services. Then, the final composition schema is generated using a refinement mechanism of abstract services using semantic matching techniques and taking into account user context and constraints.     

Towards runtime discovery, selection and composition of semantic services

Service-orientation is gaining momentum in distributed software applications, mainly because it facilitates interoperability and allows application designers to abstract from underlying implementation technologies. Service composition has been acknowledged as a promising approach to create composite services that are capable of supporting service user needs, possibly by personalising the service delivery through the use of context information or user preferences. In this paper we discuss the challenges of automatic service composition, and present DynamiCoS, which is a novel framework that aims at supporting service composition on-demand and at runtime for the benefit of service end-users. We define the DynamiCoS framework based on a service composition life-cycle. Framework mechanisms are introduced to tackle each of the phases and requirements of this life-cycle. Semantic services are used in our framework to enable reasoning on the service requests issued by end-users, making it possible to automate service discovery, selection and composition. We validate our framework with a prototype that we have built in order to experiment with the mechanisms we have designed. The prototype was evaluated in a testing environment using some use case scenarios. The results of our evaluation give evidences of the feasibility of our approach to support runtime service composition. We also show the benefits of semantic-based frameworks for service composition, particularly for end-users who will be able to have more control on the service composition process.     

Open systems interconnection — the presentation service

During 1981 far reaching decisions concerning the presentation service have been achieved. It was recognized that the use of the abstract data-type approach in the presentation service conveniently allows the required degree of precision. A specification of a presentation service based on this abstract data-type approach was outlined by the ISO Working Group 5 (responsible for developing the presentation service specification within ISO/TC97/SC16), was immediately used by Working Group 4 (for clarifying and structuring the area of open systems management, for which this WG is responsible) and was supported by Working Group 1 (responsible for the overall architecture of the area of open systems interconnection). Thus, this abstract data-type approach is currently considered to be the fundamental concept provided by presentation layer service to its users. The paper provides a presentation service specification derived by technical elaboration from the outline produced by WG5. These elaborations were performed keeping in mind the requirements of system design, which eventually must be met by the OSI application services. The paper briefly explains how the requirements of systems and software designers are related to the presentation and application services. A draft proposal for an international standard for the presentation service, which will be based on abstract data typing (as currently being discussed in the WGs of SC16 and as explained in this paper) may be expected by the end of 1982.     

基于信息熵多属性决策的Mashup服务推荐方法

随着Mashup服务的快速发展,如何在海量的服务集合中找到用户感兴趣的、服务质量高的Mashup服务,成为一个难题。针对该问题,提出一种基于信息熵多属性决策的Mashup服务推荐方法。首先建立用户兴趣模型和Mashup服务的质量(Quality of Service,QoS)模型;其次,利用信息熵多属性决策方法,预测用户对候选Mashup服务的综合评分,并将综合评分最高的Top-K Mashup服务推荐给用户;最后,在不同数据集上进行实验比较与分析,结果表明:基于信息熵多属性决策的Mashup服务推荐方法能够有效地为用户推荐其感兴趣的、高质量的Mashup服务。     

基于模糊QoS和偏好权重的Web服务组合方法研究

为了充分体现服务质量(QoS)的不确定性和用户偏好的模糊性,本文将模糊集理论引入基于QoS的Web服务组合中,将不适合精确表示的QoS属性和用户偏好等信息用三角模糊数表示.然后基于权重和法计算模糊总目标,通过设计新的模糊数比较方法,改写Pareto支配关系,将基于模糊数比较的单目标优化问题转化为多目标优化问题,并设计模糊多目标遗传算法(FMOGA)求得Pareto最优解集.该方法不仅能够得到更加贴近实际情况的优化解,同时也解决了多属性决策方法无法对大量候选服务进行全局优化的问题.最后通过实验验证了该算法的有效性和优越性.     

基于邻接矩阵的Web服务组合

针对当前Web服务组合方法在动态性和算法时间复杂度方面存在的不足,提出一种基于邻接矩阵的服务组合方法,使用邻接矩阵表示服务间的顺序及并发关系,在构建抽象服务基础上由领域专家初步建立抽象服务的组合关系,利用Warshall算法计算传递闭包来判定服务请求是否可满足,同时构建动态服务组合流程。方法操作简单,Warshall算法时间复杂度为O(n3),在服务组合中有较好的实用性。