Abstract: XSIEQ(XML stream query with immediate evaluation), a kind of XML stream query system, can evaluate predicates immediately and output in time. The design and implementation of XSIEQ are presented. XSIEQ uses a modified pushdown automata technique, and its idea is to convert all XPath expressions into a single NFA, then to attach type label and corresponding index info on NFA state. Accordingly, XSIEQ can quickly decide the opportunity of predicate evaluation and data cache in runtime, and implement immediate processing. In the end, the query performance comparison between XSIEQ and YFilter is given and analyzed.

Key words: XML stream, Predicate evaluation, Push down automata(PDA)

摘要： 介绍了一种立即计算谓词并即时输出的XML流数据查询系统XSIEQ。XSIEQ采用修改了的下推自动机技术，对多个XPath式按前缀共享的方式构造NFA，并对NFA状态进行类型标记和添加索引；从而在运行时能快速确定谓词计算和数据缓存等动作的时机，实现了即时处理；最后给出了XSIEQ和YFilter的查询性能对比及分析。

关键词: XML流, 谓词计算, 下推自动机

CLC Number: 

• TP311