Implementation Of XQuery Language

XML is a standard for data representation and exchange on the Internet. The basic ideas underlying XML are very simple: tags on data elements identify the meaning of the data and nesting and references represent relationships between data elements. These features make XML suitable for both structured data and semi-structured data, and XML is widely used in data integration, metadata management, and Web data management. With the emerging of volumes of XML data, the efficient storage and query mechanism of XML data become very important. In this paper, we concentrate on implementation of XML query language-XQuery-and the storage mechanism that supports efficient query, including:1. XML data model and algebra: algebra is theory that is the foundation of a query language, and is very important for query evaluation and optimization. Algebra operates on data model. So it is necessary to investigate the data model and algebra of XML data to understand XML query language, and this paper introduces XML data model and algebra briefly.2. Storage method of XML data: The storage method is as important as query language for a database. This paper introduces the storage strategy we used when we implement XQuery language, and also some other storage methods.3. Implementation of XQuery: XQuery is the XML query language produced by W3C. There are many XML query language before XQuery draft. Some of them are based on language of previous project, such as Lorel. Some of them are graphical query language, such as XML-GL. Some languages are based on the nature of XML data, such as XQL and XML-QL. XQuery has borrowed features from these languages and it is a powerful language for querying XML. XQuery is only in a draft status, and its enhancements are undergoing, but many companies and research institutes show great interests in this language. They have implemented many demoes of XQuery language. We also implemented one, and this paper introduces algorithms that we designed to implement XQuery.