Research On Key Technology Of XML Middleware In Dameng Database

With the development of network, XML (eXtensible Markup Language) is the criteria of data representation and data exchange for its merits and is widely used. How to make use of relational database, which is proficient in data processing and has high performance in data querying, to store and process these data is now a hot point in research.XML middleware based on ralational database can store XML data and change query results from database into XML documents. Its main deficiencies lie in difficulties to map complicated elements and query the XML data. To solve the problem, research on the two key technologies which are the mapping algorithm based on DTD (Document Type Definition) and the technology of querying XML data by SQL (Structured Query Language).Aiming at the shortcomings of the mapping on attribute and element of traditional mapping algorithm based on DTD, an improved mapping algorithm is brought up. The algorithm improves the mapping of attribute by recording the default value and the enumerated value, and simplifies the element by rules. The algorithm can map DTD to relational schema exactly, analyze the relational schema, and build the tables automatically. Aiming at the shortcomings of the traditional querying algorithm based on SQL, the querying algorithm based on related tables and the querying algorithm based on mutiset are brought up. The querying algorithm based on related tables translates the query on the elements to the query on the tables, uses the foreign key between tables, and accomplishes the query on the element and the children of the element with many sentences. The querying algorithm based on mutiset translates the query on many elements to the query on many tables, and accomplishes the query on many elements with many sentences.Based on the Dameng database management System, the XML middleware is designed and accomplished, and then tested. The result of test shows that the XML middleware can map the DTD to the relational schema and query the XML data exactly.