Study And Implement Of A System For Managing Geographical Information Metadata Based On XML_Schema

The Internet/Intranet have developed quickly and provided vast terrace for the geographical information system, the XML( the extensible Markup Language) have already become the fact standard of expressing data on the environment of Internet/ Intranet, at the same time, the development of geographical information system based on Internet have become the direction, so how make use of the XML effectively to express the metadata standard of the geography information system have become the important topic. The geographical information system needs to handle the mass data, and the mass data and metadatabase still exist in the relational database which takes the dominant position, so how to build the bridge of data change and data manipulation become one of our most urgent topic between RDB and XML for the process that the geographical information system realized informatization in Internet/intranet.Aim at these two topics, this paper at the foundation of the research result that have been released already at home and abroad, go deep into the research and designed to carry out system of managing metadata of the geographical information on the environment of Internet based on XML_Schema. This main research issues and achievements in this paper are as follows:The XML_Schema Expression of the Core Metadata of the Geography Information It is proved with prodigious localized and complexity that use text method and SGML express metadata of geographical information, this paper analyzing the method of XML express method for metadata geographical information and the complexity and difficulty of setting up XML_Schema's glossary based on tree, and adopts the technology of UML to form XML_Schema's glossary,data type and structure to express the metadata standard of the geographical information system integrated and exactly in study of making use of XML_Schema to express metadata of the geographical information system, and produces a text document of XML_Schema. Bi-directional Data Transformation between RDB and XML with Semantic ConstraintsPreserved For most of existing researches on static data transformation between XML and RDB, DTD is taken as the schema description language for XML, and the semantic constraints are often lost during the transformation process. To overcome these disadvantages, the author adopts XMLSchema, a standard schema description language proposed by W3C to replace DTD. After analyzing in-depth the constraints characteristics in both XML_Schema and Relational Schema and the mapping algorithm form DTD to relational schema based on direct graph, adopts a formalized description of XML based on regular tree and a general expression for relational schema based on direct graph approach, styding the patulous E-R model, a semantic constraints-preserved algorithm which can translate XMLSchema to the general Relational schema, the procreant algorithm for the idiographic relational schema, the mapping template model of XMl_Schema, the mapping algorithm of integrated constraints, realize the bi-directional schema mapping between RDB and XML with semantic constraints-preserved, completes the bi-directional data conversion between XML and RDB. Thus, the holistic data transformation is implemented between RDB and XML and their integration on the static transformation tier is achieved. With this integration, a mass of data stored in RDB can be published as XML, and the XML data can be stored into RDB.System of Managing Metadata of the Geography Information basis of the research work above, a prototypal system of managing metadata of the geographical information, is designed and realized to validate the whole thoughts and the algorithms researched.