Study On Native XML Data Engine

With the wide use of Extensible Markup Language and the XML data growing in exponential grade,the efficient management of the XML data becomes an urgent problem.And the present methods,such as the use of file system or traditional relational database system to store and manage data,are not designed for XML,thus these data management methods have its limitation.Accordingly,the study and design of native XML data management technology based on the characteristics and requirements of XML data is conducted in this thesis.On the basis of the study of the core technologies of native XML data management,the realization of native XML data engine system is achieved. The main work as following:1.The analysis of the advantages and disadvantages of a typical XML data encoding scheme is conducted.The improvement for the DLN encoding scheme,which reduces the length of the code of DLN by a newly-designed digital model,is put forward.Subsequently,a capability analysis of the improved DLN encoding scheme is conducted.2.Based on the characteristics of XML,the compression and storage model in Xindice system is improved.And accordingly,the compression and storage design based on the byte stream is implemented.More important, this native XML data storage technology achieves efficient compression in XML data while maintaining the relationship between the data.3.On the foundation of the byte stream-based XML data compression and storage technology,and combined with the improved DLN Coding technology,a composite index structure,which supports both the query of value and the query of structure,is proposed.And the basic nature and algorithm of the index structure are discussed in detail.4.The grammar of the core expressions of XQuery query language including the PATH expression and FLWOR expression is designed.With the use of JavaCC tools and JJTree tools,the lexical analyzer and syntax analyzer are designed according to the grammar aforementioned.The analyzers shall be used to identify the syntax structure of XQuery query input,and generate a syntax tree correspondingly.5.Based on the syntax tree,the expression processing is realized.As to the PATH expression,in addition to the realization of the regular navigation processing,the composite index designed in this thesis achieves the set-processing.And for the FLWOR expression,the clauses of the expression are decomposed from the syntax tree and corresponding query processing is conducted with the final query result.