Web服务组合中相容性分析与适配方法研究

发布时间：2018-06-25 21:47

本文选题：Web服务 + 服务组合　；参考：《南京航空航天大学》2014年博士论文

【摘要】：近年来,面向服务的计算(Service-Oriented Computing,SOC)和面向服务的体系架构(Service-Oriented Architecture,SOA)作为新型的计算模式和软件架构,有效地解决了在分布、动态、异构环境下的应用集成问题。随着Web服务技术的不断成熟和发展,Web服务以其良好的封装性、松耦合、自描述等特点,成为SOA的重要实现技术之一,促使SOA从概念走向应用。由于单个Web服务提供的功能有限,为了满足实际应用的需求,常常通过组合已有Web服务以构建增值的、具有更大粒度的Web服务。因而,如何分析和保证Web服务之间不同层次的互操作性以实现服务的正确组合,成为当前具有挑战性的关键问题之一。Web服务技术所采用的一系列标准减少了服务之间的异构,实现了Web服务底层的互操作性。然而,Web服务在组合时仍然面临高层的互操作性问题。由于参与组合的Web服务通常是由不同的第三方独立地开发,这些开发者使用不同的方式来定义服务的接口描述、交互协议、功能语义等。因此,在进行服务组合之前,需要进行相容性分析以判定服务之间是否能够互操作。由于服务之间不相容而导致它们不能直接组合的现象常常发生,需要利用服务适配技术来消除服务之间的不相容而不改变服务的内部代码,从而保证服务之间的互操作性。本文主要围绕服务组合中的相容性分析和适配问题展开研究。重点研究了服务的接口、协议和语义建模,服务相容性判定和相容度计算,面向设计阶段的适配器自动构造,面向运行阶段的适配器重配置分析的关键问题。主要工作与贡献如下:(1)针对现有Web服务建模方法对服务接口、协议和语义的形式化描述的不足,提出了一种服务接口、协议和语义的形式化统一建模方法。通过对有限自动机模型进行接口、协议和语义扩展,提出了IPSFA(interface,protocol and semantics extended finite automata)模型用于对服务进行形式化描述;给出了IPSFA的组合模型的形式语义,并讨论了如何将基于XML的服务描述语言转换为IPSFA模型的方法。该建模方法同时兼顾服务在接口层、协议层和语义层上的描述信息以及它们之间的约束关系,为服务相容性分析和适配研究提供了合适的理论模型。(2)针对现有Web服务相容性分析方法通常仅关注服务的协议层信息,且缺乏对服务相容性进行定量分析的问题,提出了一种支持接口、协议和语义的服务相容性判定和相容度计算方法。在分析现有的服务相容性标准的基础上,基于IPSFA模型给出了服务之间三种相容性的形式化定义并给出了相应的判定算法;针对服务实际执行过程中的不确定性,通过引入执行路径概念并分析服务执行路径之间在接口、协议和语义层上的对偶关系来计算服务之间的相容度。该方法可以用于识别导致服务之间不相容的交互部分以反馈给开发者对服务进行重新调整或设计,且其定量计算结果可以为服务选择提供重要参考。(3)针对现有设计时服务适配方法在支持不同层面的适配、适配器构造的自动化程度以及适配器BPEL代码生成方面的不足,提出了一种面向设计阶段的适配器自动构造方法。利用服务的语义信息以及本体概念之间的语义包含关系自动生成服务之间的消息映射;在此基础上,利用“边约简边生成”的思想提出了提高了适配器自动构造的效率,并给出了约简后的适配器模型到BPEL代码的生成方法。通过该方法既可以消除服务之间接口层和协议层上的不相容使得多个服务能够进行组合,又保证了基于适配器的服务组合在语义上的一致性。(4)针对现有运行时服务适配方法缺乏对适配器重配置分析的支持,提出了一种面向运行阶段的适配器重配置分析方法。通过引入后向迹符合和前向迹符合的概念,以判定适配器实例的历史执行和将来可能的执行在新适配器定义下的有效性。在此基础上,提出了基于前/后向迹符合的适配器重配置分析算法,用于判定适配器实例的可迁移性以及确定重配置的目标状态。通过该方法使得适配器具有重配置的能力,以便应对服务在运行期间的演化问题。(5)基于以上方法和理论,设计并部分实现了支持相容性分析和适配的服务组合原型工具,给出了该工具的系统架构、主要功能模块和执行流程。该工具能够支持服务选择阶段的相容性判定和相容度计算、服务组合设计阶段的适配器自动构造、服务组合运行阶段的适配器重配置分析。
[Abstract]:In recent years, service oriented computing (Service-Oriented Computing, SOC) and service oriented architecture (Service-Oriented Architecture, SOA), as a new computing model and software architecture, effectively solve the problem of application in distributed, dynamic and heterogeneous environments. With the continuous maturation and development of Web service technology, Web services With its good encapsulation, loosely coupled, self description and so on, it has become one of the important implementation technologies of SOA, prompting SOA from concept to application. Because the function provided by a single Web service is limited, in order to meet the needs of the actual application, it often constructs value-added and has a larger granularity Web service by combining the existing Web services. An analysis and assurance of interoperability between different levels of Web services to achieve a correct combination of services has become one of the key issues that are currently challenging. A series of standards adopted by.Web services technology reduce the heterogeneity between services and realize the interoperability of the underlying Web services. However, the Web service still faces high-level interoperability in the combination of services. Operational problems. Since the Web services involved in the combination are usually developed independently by different third parties, these developers use different ways to define service interface descriptions, interaction protocols, functional semantics, etc. Therefore, the compatibility analysis needs to be carried out to determine whether the service can be interoperable before the service composition is carried out. The incompatibility between services often leads to their inability to combine directly. The service adaptation technology should be used to eliminate the incompatibility between services without changing the internal code of the service, thus ensuring the interoperability between services. This paper focuses on the compatibility analysis and adaptation problems in the service composition. The interface, protocol and semantic modeling of services, service compatibility determination and compatibility calculation, the automatic construction of adapters in the design phase, and the key problems of the runtime oriented adapter reconfiguration analysis are studied. The main work and contributions are as follows: (1) the formalization of the existing Web service modeling methods for service interfaces, protocols and semantics A formal unified modeling method for service interfaces, protocols and semantics is proposed. Through the interface, protocol and semantic extension of the finite automata model, the IPSFA (interface, protocol and semantics extended finite automata) model is proposed for formal description of service, and a combination mode of IPSFA is given. Form semantics, and discuss how to convert the XML based service description language into a IPSFA model. The modeling method takes into account the description information on the interface layer, the protocol layer and the semantic layer and the constraints between them, and provides a suitable theoretical model for the service compatibility analysis and adaptation research. (2) The existing methods of Web service compatibility analysis usually focus only on the protocol layer information of services, and lack the quantitative analysis of service compatibility. A method of service compatibility determination and compatibility calculation is proposed to support the interface, protocol and semantics. Based on the analysis of the existing standards of service compatibility, the IPSFA model is given. A formal definition of three compatibility between services is defined and a corresponding decision algorithm is given. In view of the uncertainty in the actual execution of services, the compatibility between services is calculated by introducing the concept of the execution path and analyzing the dual relationship between the service execution paths on the interface, protocol and semantic layer. This method can be used to identify the service. Do not cause an incompatible interaction between services to feed back to the developer to adjust or design the service, and its quantitative results can provide an important reference for service selection. (3) for the existing design time service adaptation methods in support of different levels of adaptation, the degree of automation of the adapter structure and the adapter BPEL code In the lack of generation, a method of automatic adaptor construction for design phase is proposed. Using semantic information of service and semantic inclusion relationship between ontology concepts, the message mapping between services is automatically generated. On this basis, the idea of "edge reduction generation" is used to improve the efficiency of automatic adaptor construction. Rate, and gives the generation method of the reduced adapter model to the BPEL code. By this method, the incompatibility between the interface layer and the protocol layer between services can be eliminated so that multiple services can be combined, and the semantic consistency of the adapter based service composition is guaranteed. (4) the existing operation time service adaptation method is short. For the support of the adaptor reconfiguration analysis, a runtime oriented adapter reconfiguration analysis method is proposed. By introducing the concept of back trace coincidence and forward trace conformation, the history execution of the adapter instance and the possible future execution under the new adapter definition are determined. The adapter reconfiguration analysis algorithm is used to determine the mobility of the adapter instance and to determine the target state of the reconfiguration. Through this method, the adapter has the ability to reconfigure the adapter to cope with the evolution of the service during operation. (5) based on the above methods and theories, the support compatibility is designed and partially implemented. The system architecture, the main function modules and the execution flow of the tool are given. The tool can support the compatibility determination and compatibility calculation of the service selection stage, the adapter automatic construction in the service composition design phase, and the adapter reconfiguration analysis in the service composition operation stage.
【学位授予单位】：南京航空航天大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TP393.09

【参考文献】