Research On XML Query Technology

As the standard of data representation and data exchange over the web, XML technology plays a crucial role in web data management. XML query is an important area of XML technology. Although achievements of XML research are made, there are some problems of XML query technology because of XML's inherent characteristic. This thesis takes focus on the technology of XML query.XML query includes content query and structural query. The query condition can be represented as a simple path expression (SPE) or a regular path expression (RPE). This thesis presents an algorithm based on signature for XML data query. XML document is transferred to sig-DOM tree, which includes signature and filter information. The query signature is compared with node signature of sig-DOM tree in query processing. This algorithm can reduce search space rapidly by filtering and pruning the node of sig-DOM tree.The thesis proposes algorithms based on index for XML data query. Path index named KI is presented to soive the problems of relative path query. Value index named VI is introduced for the value query of elements or attributes. In query processing, signature technology is used to filter the root of sig-DOM tree firstly, and then index is used to find the results of query rapidly. In order to ensure the stability of index query, the index node's splitting conditions and algorithms are studied.All algorithms proposed in this thesis are implemented in a XML query system named SXMLIQ. Performances of them are studied by experiments. XML query examples are tested by the XML datasets of Shakespeare plays. The experiments results show that the query algorithm based signature and the query algorithm based index are effective and efficient.