信息网格中元数据层次化结构模型的研究和应用

数据的透明访问是信息集成技术研究的重点问题之一，分布自治的动态网格环境为数据的透明访问带来了更大的挑战，因此网格在分布式数据的异构透明和位置透明的基础上，提出了名字透明、并行透明、模式变更透明等更高层次的要求，这对于描述资源结构、内容、访问方式的元数据的设计也提出了更高的要求，基于信息资源空间模型的元数据层次化结构模型对屏蔽物理资源模式差异和模式变化，实现物理资源命名和位置独立性，实现资源透明访问的目标具有有益的帮助，最后介绍了支持这种元数据结构的元数据目录服务在铁路信息网格中间件中的设计和实现。

Research on a Layered Architecture for the Metadata with Applications in Information Grid

How to access data transparently is an important issue in information integration research. Grid introduces new challenges to access data transparently, because of the autonomy, diversity and dynamism of data sources. Therefore, higher transparency requirements are enforced in the grid environment, such as name transparency, parallelism transparency and schema change transparency in addition to heterogeneity and location transparency, and they bring stricter requirements to metadata design. A layered architecture of metadata based on the information grid resource space model is introduced to mask the diversity and volatility of physical resources' schema, to realize independency of physical resource's name and location, and to realize the goals of transparently accessing resources. Finally, a metadata catalog service that is designed with this metadata architecture, as well as its application in the design and implementation of railway information grid middleware are introduced.