学科：地图学与地理信息系统. 对地观测传感网服务,出版时间：2008,导师：狄黎平，龚健雅指导,学位授予单位：武汉大学,论文作者：闵敏著,
中文
近年来，随着计算机技术、通信技术、微电子技术、信息处理技术等各方面的迅速发展，使得传感器网络(SensorNetworks)的发展日新月异。传感网(SensorWeb)技术是将传感器和传感器网络技术与面向服务的体系构架以及网络服务技术相结合而出现的一项新技术。随着传感网研究和技术的发展，目前许多测量设施，包括从传感器仪器到传感器系统，再到数据存储技术和远程数据访问等技术都趋向成熟。在地球科学领域，各种研究模型也因为各种可访问和获取的数据量的极大丰富而获得进一步改进，可以获取更准确的分析、更准确的控制并产生更可靠的预测结果。地学领域里的对地观测传感网的目标就是可以动态连接各种传感器和终端用户，形成一套从观测规划、数据接收、数据处理到应需产品生成工作流自动化系统模式。因此，如何建立一个对地观测传感网系统信息服务体系架构来整合对地观测技术和地球科学建模技术，实现二者之间的动态自适应性交互是对地观测传感网的核心所在。 SEPS(Self-Adaptive Earth Predictive Systems，自适应地球预测系统)是一种满足动态交互性、可扩展性、可重用性的等基本特点的对地观测传感网系统信息服务体系架构。SEPS可以为地理空间信息科学提供了更宽广的发展空间和更广泛的应用领域。同时，SEPS的实施过程中出现一些对现有的信息处理技术的挑战问题。实时动态的传感器数据的定制、获取、分析和处理是不同于以往静态空间数据查询、访问、获取、处理的一个长期复杂的过程。目前地球空间信息科学系统中的Web服务功能和Web服务组合技术主要是基于静态同步信息处理的。以OGC为代表的地球科学信息服务标准化组织制定了一系列基于同步通讯的互操作Web服务标准和规范，这些标准和规范适用于简单的、非实时的分布式计算环境，但对于复杂的动态异步信息的处理存在着许多不足之处，难以满足Sensor Web环境下web服务以及进行服务组合的异步性要求。为此，本文从介绍Sensor Web这一地球空间信息科学的新研究背景出发，研究了在对地观测传感网环境下实现异步空间信息服务框架的一些关键技术。 本文具体研究内容和创新之处主要体现在以下几个方面： ● 提出了建立对地观测传感网(Sensor Web)服务体系框架时必须实现的几个原则特点。文章首先对传感网技术进行了回顾和分析，在此基础上，对于对地观测传感网(geospatial Sensor Web)的定义内涵、技术特性和发展状况进行了明晰，从而明确了对地观测传感网的核心在于建立一个对地观测传感网系统信息服务体系架构来整合对地观测技术和地球科学建模技术，实现二者之间的动态自适应性交互。根据这一特点，提出了建立对地观测传感网系统框架的3大原则，即动态交互性、可扩展性以及可重用性。根据这些原则，研究了一种自适应性反馈的对地观测传感网服务体系框架SEPS，并分析了目前实现SEPS框架时存在的一些技术难题，明确了本文的研究重点。 ● 提出了一种基于异步消息通知中间件扩展网络服务处理调用的OGC网络服务的异步服务机制。这种异步服务机制是针对目前OGC普遍实现的基于HTTP绑定的Web服务而提出的。该方法基于OGC的异步消息通知服务WNS的two-way通信方法的回调机制，实现了对OGC中提供缓存(store)和/或状态(status)更新机制的服务实现异步调用。这种方法以OGC的各种数据处理服务和WNS为核心。只要服务器端能支持缓存和/或状态更新，就可以采用这种消息中间件进行异步扩展，而服务器端现有的OGC的Web服务而无需进行任何改动。这种异步机制解决了OGC服务中SOAP绑定使用不普遍而导致无法使用通用异步机制实施异步服务的问题。 ● 提出了一种使用基于异步消息扩展的OGC WPS服务与BPEL异步执行相结合而扩展的异步动态耦合服务链机制。该方法将所有参与链接的OGC Web服务封装成可使用SOAP和WSDL的WPS服务，WNS作为这些服务内部的异步消息通信机制实现服务回调，再采用BPEL WS-Addressing实现服务之间异步链。这样所有工作流中涉及的服务都成为了可使用PUSH模式的异步服务，再将这种使用异步消息的服务用基于BPEL的工作流引擎进行自动化执行。这种方法既充分利用了BPEL的成熟技术支持，又保留了各Web服务器端提供HTTP为主的服务不变，实施简便，大量节省开发成本和时间，易于各种工作流的共享。避免了领域科学家需要使用OGC服务链引擎时编码复杂，难以适应各种不同语言平台环境的问题。在研究过程中，也分析比较了目前工业界通用的工作流方法以及目前OGC提出的几种服务链机制。 ● 以鸟类迁徙为例，进行了自适应性传感网信息服务框架SEPS以及提出的异步服务机制和动态耦合机制进行了在地球观测科学研究领域的应用实证。该实证应用研究证明了自适应对地观测传感网框架以及文中的异步服务机制和动态工作流机制在地球科学研究应用中具有可行性和可重用性价值。 ● 归纳总结了对地观测传感网研究在理论和方法有待进一步研究和解决的问题，提出了对地观测传感网在理论模型和领域应用中的未来研究方向。 关键词：对地观测传感网，异步服务，异步服务链，
英文
Recent technological advancement in computation, wireless communication, microelectronics and networking has enabled the rapid development of low-cost sensors and sensor networks. Sensor web is a new concept which is enabled by the advancement of sensors and sensor network technologies under the service-oriental architecture (SOA) and web service environment. With the advances in sensor web technologies, great achievements are made for lots of observation instruments which involve from sensors to sensor systems, from data storing to remote accessing. In the meanwhile, the modeling research in many earth science communities has been greatly improved because of the abundant earth observation data, so that more accurate prediction can be made because of the more accurate analysis and more accurate controlling in the earth system models. The goal of geospatial sensor web is to connect various sensors with clients dynamically and automatically establish the dynamic system including observation planning, data accessing, data processing, and on-demand data acquisition. The key of geospatial sensor web is the geospatial sensor web framework which can dynamically couple sensor web and earth system models and provide the interoperability between them in a self-adaptive way. SEPS (Self-Adaptive Earth Predictive Systems) is a geospatial sensor web framework which is dynamically interoperable, scalable, and reusable. SEPS can provide more application fields and more developing space for geospatial information science, however, there are still some technology challenges in implementing SEPS. The discovering, tasking, accessing, and processing of dynamic real-time observations are often complicated long-term processes, which is much different with those of the previous static archived data. However, the present Web services and Web service orchestration technologies are mostly based on the processing of static synchronous information. OGC, an organization of geospatial information standardized service, provides a series of standards and specifications in geospatial Web services interoperability based on synchronous communication. The OGC standards and specifications are useful in the simple and non-realtime distributed computation environment. But these standards and specifications can not satisfy the requirement of asynchronous Web services and Web services orchestration in sensor web. In this paper, based on the concept of sensor web, we try to provide some solutions for these challenges. The main works and contributions of this paper are as following: ● The principles of developing a geospatial sensor web framework are provided. Based on the review of sensor web, we analyzed the concept, properties and developing of geospatial Sensor Web, points out that the key in developing the geospatial Sensor Web framework is to dynamically coupling the earth observation and earth system models and enabling the interoperability. Based on that, 3 main principles were pointed out—dynamic interoperability, scalability and reusability. On the basis of these principles, SEPS framework and the technical issues in implementation of SEPS are analyzed. ● An asynchronous Web service mechanism of augmenting OGC Web services with message-based asynchronous notification middleware is provided. This asynchronous mechanism is for the popular HTTP-binding OGC services. It is based on the two-way communication of OGC WNS, and realizes the asynchronous invocation to the OGC services which support “store” and/or “status”. This middleware can be used for augmenting OGC Web services asynchronously without any revision of the existed OGC synchronous web services. It overcomes the asynchronous issue of non-SOAP binding in OGC OWS. ● An asynchronous web services orchestration mechanism for OGC web services is provided which based on OGC WPS extended with asynchronous message and BPEL engine. In this way, all OGC web services in the service chain are wrapped with WPS which uses SOAP and WSDL, WNS enables the asynchronous invocation, and BPEL WS-Addressing fulfills the asynchronous chaining. All the services involved are converted to asynchronous web services in PUSH mode. This method not only makes full use of the mature technology of BPEL, but also remain the existed OGC OWS unchanged. It’s money-saving, and easy-sharing. ● A case of bird migration is established to verify the SEPS framework and the asynchronous web services technology and dynamically web services orchestration technology in this paper. The case successfully demonstrates the feasibility and reusability of SEPS framework and the key technologies mentioned above. ● At last, the thesis summarizes the main works and lists some future research aspect of geospatial sensor web. Keywords: Geospatial Sensor Web, asynchronous Web services, asynchronous Web services orchestration
