Thematic Real-time Environmental Data Distributed Services (THREDDS)

UCAR Unidata计划正在开发一个组织基础设施和一个软件基础设施，即主题性实时环境分布式数据服务(THREDDS)，使教育工作者和研究人员能够在他们的教室和实验室中定位、分析、可视化和发布各种环境数据。这一基础设施的框架以可公布(数据)清单和目录(PICAT)的概念为基础，并将驻留在远程分布式服务器上的现有广泛环境数据集合中已在使用的一系列技术联系在一起。其中包括罗德岛大学和威斯康星大学麦迪逊分校的客户/服务器数据访问协议、UniData的实时互联网数据分发系统、地球系统教育数字图书馆(DLESE)的发现系统，以及一套广泛的客户可视化工具。基于可扩展标记语言(XML)，PICAT形式的元数据以多种不同的方式创建。接收实时环境数据仪器解码器的站点，以创建描述到达时的数据产品的PICAT。爬虫程序还可以通过遍历现有的回溯数据集合来创建PICAT。由于PICAT不一定驻留在包含数据的服务器上，因此研究人员可以为指向驻留在多个数据服务器上的数据集的研究出版物创建PICAT。同样，教育工作者可以将说明性数据集的PICAT合并到教育模块中，这些模块还包括数据分析和可视化工具。学生也可以使用PICAT来指向与其研究项目相关的数据集，就像他们现在使用URL来指向相关文档一样。最后，PICat以文本为基础的性质使其不仅可以通过当前的文献搜索引擎，而且还可以通过利用PICat的内部结构和语义内容的专门工具在数字图书馆中进行收获和索引。该项目的部分共同资金由美国国家科学基金会地球科学局的地球科学部提供。

The UCAR Unidata program is developing an organizational infrastructure and a software infrastructure, Thematic Real-time Environmental Distributed Data Services (THREDDS), to enable educators and researchers to locate, analyze, visualize, and publish a wide variety of environmental data in both their classrooms and laboratories. The framework for this infrastructure is based on the concept of publishable (data) inventories and catalogs (PICats) and ties together a set of technologies already in use in existing, extensive collections of environmental data that reside on remote, distributed servers. These include client/server data-access protocols from the University of Rhode Island and the University of Wisconsin-Madison, the real-time Internet Data Distribution system from Unidata, the discovery system at the Digital Library for Earth System Education (DLESE), and an extensive set of client visualization tools. Based on the eXtensible Markup Language (XML), metadata in the form of PICats are created in many different ways. Sites receiving real-time environmental data instrument decoders to create PICats describing data products as they arrive. Crawlers can also create PICats by traversing existing retrospective data collections. Since the PICats do not necessarily reside on the server with the data, researchers can create PICats for research publications that point to datasets residing on several data servers. Likewise educators can incorporate PICats of illustrative datasets into educational modules that also include the tools for data analysis and visualization. Students may also use PICats to point to datasets related to their research projects, just as they now use URLs to point to relevant documents. Finally, the text-based nature of PICats allows them to be harvested and indexed in digital libraries not only by current document search engines, but also by specialized tools that make use of the internal structure and semantic content of the PICats. Partial co-funding of this project is being provided by the Division of Earth Sciences in NSF's Geosciences Directorate.