Query Processing And Research For Structural Join Against XML Data

XML has become new criteria of data represention and exchange in Internet and it has been accepted in many fields since it was put forward by W3C in 1998. This is creating a new set of data management requirements involving XML. Traditional database technologies can't work efficiently owing to the tree-like nature of XML data and new application environment .New technologies specially designed for XML data are needed to process XML data efficiently. In this paper, we focus on the path expression processing such that the key issues in the large-scale XML query application can be settled by feasible approaches. We propose a system framework of XPath query, defining the XPath grammar that the system can deal with, giving the query processing system.As the core operation of XML query processing, the efficient implimenation of structural join is the key to improve XML query processing. Based on the region numbering scheme of XML data, we led into filter-based twig structural join technology. Different form previous algorithms, filteration algorithm filters the query pattern and the data set with the path encoded information, leaving the elements to join the structural join. Then we use twig join algorithm for these elements. We introduce the concept of source path and path containment, decreasing the amount of PSet. We hava carried out an experiment to compare the technologys about whether using filtering algorithm or not. The results of our comprehensive experiment show that the twig join algorithm with filtering process performs well both synthetic and real-word datasets,and has good scalability.The XML containment join algorithm is proposed based on XML encoding. Many researchers hava proposed all kinds of encoding and relevant containment join algorithms. We sum various structural join algorithms up. At last, we analyse the performance of these algorithms.