针对XML流数据的复杂Twig Pattern查询处理

XML流数据处理在研究领域引起了研究者的广泛兴趣.针对XML流数据的、具有嵌套AND/OR谓词的复杂Twig Pattern查询处理,提出一种新方法.为了提高查询处理性能,将所有Twig Pattern合并为一个共享前缀的查询树,其中,AND/OR谓词被表示为单独的抽象语法树,因而能够以文档顺序、单遍地处理复杂Twig Pattern的匹配,并避免了YFilter中对嵌套谓词进行后置处理所产生的中间结果.实验结果表明,该方法能够有效改善Twig Pattern的处理性能,尤其是在处理大文档的情况下.基于已

Complex Twig Pattern Query Processing over XML Streams

The problem of processing streaming XML data is gaining widespread attention from the research community. In this paper, a novel approach for processing complex Twig Pattern with OR-predicates and AND-predicates over XML documents stream is presented. For the improvement of the processing performance of Twig Patterns, all the Twig Patterns are combined into a single prefix query tree that represents such queries by sharing their common prefixes. Its OR-predicates and AND-predicates of a node are represented as a separate abstract syntax tree associated with the node. Consequently, all the Twig Patterns are evaluated in a single, document-order pass over the input document stream for avoiding the interim results produced by the post-processing nested paths of YFilter. Compared with the existing approach, experimental results show that it can significantly improve the performance for matching complex Twig Patterns over XML document stream, especially for large size XML documents. Based on the prior works, the optimization of twig patters under DTD (document type definition) by using structural and constraint information of DTD is also addressed, which is static, namely, it is processed before the runtime of stream processing.