一种XML数据流之上持续查询执行器的增量维护方法

在XML数据流的海量持续查询处理领域中，很少有研究涉及到在查询集合发生变化的情况下，如何调整查询执行器以满足当前查询集合的问题．由于XML数据查询的数目是海量的，查询执行器重新构建的代价非常高．针对上述问题，提出了基于转换累计自动机的查询执行器的增量维护方法，来完成查询集合的增量增加和删除，从而避免了执行器重构的昂贵代价．同时，利用XML文档DTD结构约束，提高了查询执行器增量维护的效率，减少了增量维护所导致的空间冗余．实验表明，该方法能够以有限空间为代价，有效完成XML数据流持续查询执行器的动态维护．

Incremental Maintenance of Continuous Query Evaluator over XML Data Stream

In the research of massive continuous XPaths evaluation over XML data stream, little has been done on the maintenance of the evaluator when the query set evolves Due to the massiveness of the XPath set, it takes a high cost to reconstruct the evaluator each time A new method is proposed to handle this problem Based on the new transition-rules-counting automata, this method implements the increase and removal of XPath query dynamically and incrementally, and therefore, avoids the high cost of reconstruction In addition, XML structural constraints DTD can be exploited to improve the efficiency of the incremental maintenance and reduce the possible redundant space cost incurred in the incremental maintenance The experiments show that the method proposed can efficiently maintain the evaluator of the continuous query over XML data stream at a low cost of extra space resource