How big must complete XML query languages be?

13 years 4 months ago
How big must complete XML query languages be?
Marx and de Rijke have shown that the navigational core of the w3c XML query language XPath is not first-order complete ? that is it cannot express every query definable in firstorder logic over the navigational predicates. How can one extend XPath to get a first-order complete language? Marx has shown that Conditional XPath ? an extension of XPath with an "Until" operator ? is first order complete. The completeness argument makes essential use of the presence of upward axes in Conditional XPath. We examine whether it is possible to get "forward-only" languages that are first-order complete for XML Boolean queries. It is easy to see that a variant of the temporal logic CTL is first-order complete; the variant has path quantifiers for downward, leftward and rightward paths, while along a path one can check arbitrary formulas of linear temporal logic (LTL). This language has two major disadvantages: it requires path quantification in both horizontal directions (in pa...
Clemens Ley, Michael Benedikt
Added 21 Nov 2009
Updated 21 Nov 2009
Type Conference
Year 2009
Where ICDT
Authors Clemens Ley, Michael Benedikt
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