Satisfiability of XPath Queries with Sibling Axes

Floris Geerts, Wenfei Fan

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We study the satisfiability problem for XPath fragments supporting the following-sibling and preceding-sibling axes. Although this problem was recently studied for XPath fragments without sibling axes, little is known about the impact of the sibling axes on the satisfiability analysis. To this end we revisit the satisfiability problem for a variety of XPath fragments with sibling axes, in the presence of DTDs, in the absence of DTDs, and under various restricted DTDs. In these settings we establish complexity bounds ranging from NLOGSPACE to undecidable. Our main conclusion is that in many cases, the presence of sibling axes complicates the satisfiability analysis. Indeed, we show that there are XPath satisfiability problems that are in PTIME and PSPACE in the absence of sibling axes, but that become NP-hard and EXPTIME-hard, respectively, when sibling axes are used instead of the corresponding vertical modalities (e.g., the wildcard and the descendant axis).
Original languageEnglish
Title of host publicationDatabase Programming Languages
Subtitle of host publication10th International Symposium, DBPL 2005, Trondheim, Norway, August 28-29, 2005, Revised Selected Papers
PublisherSpringer Berlin Heidelberg
Number of pages16
ISBN (Electronic)978-3-540-31445-5
ISBN (Print)978-3-540-30951-2
Publication statusPublished - 2005

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