XPath Whole Query Optimization

Sebastian Maneth, Kim Nguyen

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Previous work reports about SXSI, a fast XPath engine which executes tree automata over compressed XML indexes. Here, reasons are investigated why SXSI is so fast. It is shown that tree automata can be used as a general framework for fine grained XML query optimization. We define the “relevant nodes” of a query as those nodes that a minimal automaton must touch in order to answer the query. This notion allows to skip many subtrees during execution, and, with the help of particular tree indexes, even allows to skip internal nodes of the tree. We efficiently approximate runs over relevant nodes by means of on-the-fly removal of alternation and non-determinism of (alternating) tree automata. We also introduce many implementation techniques which allows us to efficiently evaluate tree automata, even in the absence of special indexes. Through extensive experiments, we demonstrate the impact
of the different optimization techniques.
Original languageEnglish
Pages (from-to)882-893
Number of pages12
JournalProceedings of the VLDB Endowment (PVLDB)
Volume3
Issue number1
Publication statusPublished - 2010

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