【作者】 陈曦；

【导师】 曾华燊；

【作者基本信息】 西南交通大学 ， 计算机应用技术， 2013， 博士

【摘要】 在设计之初,0SI/RM和Internet被定义为用于解决计算机系统问一致化访问的网络级互联平台。此后应用层被添加到该平台之上以提供对应用的若干通用支持,但应用系统仍被排除在OSI/RM范围之外。事实上,OSI/RM缺少开放的应用层服务及其接口的定义,这客观上使应用层与实际网络应用界限不清,不能实现网络支撑功能的有效封装及一致化交付,造成实际的网络应用与应用层往往紧紧耦合在一起,难以移植,这一情况在分布式环境下表现得尤为明显。为解决网络应用支撑平台与网络应用系统之间界线模糊的问题,本论文以OSI/RM为背景,给出了开放式网络应用服务模型(ONAS模型,Open Network Application Service Model),探讨如何通过显式定义的网络应用服务接口NASI(Network Application Service Interface)提供公用支撑功能,以简化网络应用系统的开发。论文特别选取Web服务为特例,讨论了上述设计思路。近年来,Web已经从单纯的超文本／超媒体交换工具演变为业务应用支撑平台,而Web服务技术也应运而生以适应这一演进。事实上,诸多C/S或P2P模式的应用往往采用Web服务作为其访问入口。Web服务的流行得益于其良好的封装性、松散的耦合性及高度的集成性。这些优点使得Web服务可被广泛复用,以组装的方式快速构建网络应用。尽管如此,在Web服务生命周期的各个阶段(服务建模、发布、发现、合成、执行阶段等),仍有若干亟待解决的问题妨碍了Web服务的进一步发展和更广泛的应用。本论文以ONAS模型为基础,着重探讨了Web服务资源的管理问题,为各个阶段存在的问题提供了相应的解决方案。论文在这方面的主要贡献如下：(1)提出了Web服务的统一建模、存储和查询平台ServUnity:ServUnity构成了异构Web服务(如W3C Web Service.RESTful Service、一般的Web API等)的桥梁,实现对其一致化的管理。具体而言,ServUnity包含以下几个方面的研究工作：·统一服务图模型USGM(Unified Service Graph Model):USGM是对不同服务语言的高层抽象,利用W3C的资源描述框架RDF(Resource Description Framework)将异构Web服务建模为RDF服务图,以此为基础实施对Web服务的统一建模、存储和查询。·服务图转换方案和服务知识库：为基于标准的服务类型(如WSDL.Yahoo! Pipes等)提供了向服务图的自动转换算法；为非标准的服务类型(如RESTfulService)提供了半自动化协助的交互式转换方案。构建了基于服务图的服务知识库(Service Knowledge Base,SKB),以实现基于服务图的语义挖掘,为合理地选择服务提供决策支持。●基于服务知识库的Web服务统一查询引擎：该引擎支持标准的RDF查询语言SPARQL及基于费用的服务链多路优选算法CSCO(Cost-based Service Chain Optimization)以适应不同的应用场景和用户需求。(2)设计了基于空间填充曲线和分布式哈希表的协作式Web服务合成方案CWSC(Collaborative Web Service Composition)：CWCS将服务合成请求与分布式解集数据库进行匹配以求解感知QoS的服务合成,相对于传统的基于数学规划的解法,避免了繁重的运算;相对于集中式的基于案例推理(Case Based Reasoning, CBR)解法,提高了系统伸缩性和可靠性。(3)针对组合Web服务的执行,设计了局部中心化的去中心式编制DOLCO(Decentralized Orchestration with Local Centralized Orchestration):通过结合传统的中心式编制CO(Centralized Orchestration)和去中心式编制DO (Decentralized Orchestration)的优点,DOLCO采用了根据关联度划分的多调用代理结构。相对于CO,DOLCO提供了更高的系统并发度和可靠性。相对于DO,在服务请求高峰期,DOLCO通过动态配置调用代理,提供了备用调用代理,可降低调用代理失效率。此外,本论文另一方面的贡献在于,在前几章研讨ONAS模型的基础上,第7章提出了用于开放式应用互联的NTSP-DAS RM(网络传输支撑平台-分布式应用系统关系模型,Network Transport Support Platform-Distributed Application Service Relation Model),探索性地从应用系统开放式互联的角度挑战了OSI/RM体系结构。通过将应用层纳入到应用系统,NTSP-DAS RM简化了网络平台和分布式应用系统的交互。分析表明NTSP-DAS RM使得网络平台和应用之间的信息、交互大为减少,并可更灵活地适配到异构网络环境,因此相对于ONAS模型更具优势。更多还原

【Abstract】 The OSI/RM and Internet were essentially designed as a network interconnection platform addressing universal access issues among computer systems. However, application systems were out of the scope of OSI/RM, although a layer called Application had been added on top of the platform to perform common support for applications. The fact that OSI/RM lacks the open Application-Layer service and interface definitions blurs the demarcation between network applications and Application Layer, leading to a situation that support functions offered by network platforms can hardly be encapsulated and delivered to applications in a unified and effective manner. Applications are thus tightly coupled with Application Layer, resulting in poor portability, especially in a distributed environment. In this dissertation, the ONAS (Open Network Application Service) Model in the context of OSI/RM was introduced with the aim to clearly set the boundary between applications and network. It was discussed in this dissertation on how to simplify the development of network applications by offering common support functions through explicitly well-defined Network Application Service Interfaces (NASI). And Web services were deliberately chosen to investigate the above design ideas.Over the years, the Web has evolved from a hypertext/hypermedia exchange tool to a business application support platform. Recent years have also witnessed the emergence of Web services to adapt to the evolution. In fact, Web services have become the common portals for a variety of applications not only in C/S mode but also in P2P mode. Benefited from advantages such as well encapsulation, loose coupling and high integration, Web services can be extensively reused to assemble network applications. However, there are still a few problems left unsolved in different stages (service modeling, publishing, discovery, composition, execution, etc.) spanning the Web service life cycle, which hampers the further development and wider adoption of Web services. This dissertation is devoted to solutions to a few critical Web service resource management issues in different stages from the perspective of ONAS Model. The contributions to Web service resource management include:(1) Proposed the ServUnity platform providing a unified approach for Web service modeling, storing, and discovering to bridge the gap among diverse Web services such as W3C Web Services(i.e. WSDL), RESTful Services and general Web APIs to achieve unified management. Specifically, ServUnity is supported by the following research work:? The Unified Service Graph Model (USGM):a high-level abstraction of different service languages, which models heterogeneous services as service graphs by means of W3C Resource Description Framework (RDF) and enables unified service modeling, publishing and discovery. ? Service graph conversion schemes and the Service Knowledge Base (SKB): automatic conversion algorithms for standard-based service types (such as WSDL, Yahoo! Pipes, etc.), interactive conversion with semi-automated assistance for non-standard-based service types (such as RESTful Service). On the basis of the generated service graphs, SKB is constructed for extensive semantics mining and sensible service selection decisions.? A unified Web service query engine over SKB supported by the standard RDF query language SPARQL and the new Cost-based Service Chain Optimization (CSCO) algorithm to meet different requirements in different application scenarios.(2) Proposed the Collaborative Web Service Composition (CWSC) scheme based on Space-filling Curve and Distributed Hashing Table:It solves QoS-aware service composition problem by matching new requests with distributed solution-bases to avoid intensive computation as with traditional Mathematical Programming approaches, and provide better scalability and reliability than centralized Case Based Reasoning (CBR) approaches.(3) Proposed a new approach called DOLCO (Decentralized Orchestration with Local Centralized Orchestration) for composite Web service execution:It improves composite service execution performance with affinity-based multi-proxies by combining the advantages of traditional CO (Centralized Orchestration) and DO (Decentralized Orchestration), resulting in better system concurrency and reliability than CO and higher utility of proxies than DO at average request rate. A few backup proxies can be used to cope with peak request traffic via dynamic proxy configuration to reduce proxy failure.The final contribution of this dissertation is, on the basis of ONAS Model, the introduction of a new open application interconnection model called NTSP-DAS/RM (Network Transport Support Platform-Distributed Application Service/Relation Model) as discussed in Chapter7, which challenges OSI/RM from the perspective of application interconnections. It simplifies the interaction between the NTSP and distributed application systems by returning the Application Layer back to application systems. Analysis has shown that NTSP-DAS RM is more superior over ONAS Model discussed in Chapter1, considering that information exchange between network platform and applications can be greatly reduced and it is also more flexible to adapt to heterogeneous networking environment.更多还原