Unlocking Keys for XML Trees

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Unlocking Keys for XML Trees
Abstract. We review key constraints in the context of XML as introduced by Buneman et al. We show that one of the proposed inference rules is not sound in general, and the axiomatisation proposed for XML keys is incomplete even if key paths are simple. Therefore, the axiomatisation and also the implication problem for XML keys are still unsolved. We propose a set of inference rules that is indeed sound and complete for the implication of XML keys with simple key paths. Our completeness proof enables us to characterise the implication of XML keys in terms of the reachability problem of nodes in a digraph. This results in a quadratic time algorithm for deciding XML key implication, and shows that reasoning for XML keys is practically efficient.
Sven Hartmann, Sebastian Link
Added 16 Aug 2010
Updated 16 Aug 2010
Type Conference
Year 2007
Where ICDT
Authors Sven Hartmann, Sebastian Link
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