XML Stream Processing

This chapter reviews recent advances on stream XML query evaluation algorithms with stack-based encoding of intermediary data. Originally proposed for disk-resident XML, the stack-based architecture has been extended for streaming algorithms for both single and multiple query processing, ranging from XPath filtering to more complex XQuery. The key benefit of the stack-based architecture is its succinct encoding of partial query results, which can cause exponential enumeration if encoded naively. In addition, the chapter discusses opportunities to integrate benefits demonstrated in the reviewed work. For single-query processing, a sketch is given for an integrated algorithm, StreamTwig2Stack, that achieves all the benefits of existing algorithms in terms of functionality, time complexity, and buffer memory optimality.