Unlocking Keys for XML Trees

  • Sven Hartmann
  • Sebastian Link
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4353)


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.


Inference Rule Integrity Constraint Reachability Problem Path Expression Target Path 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2006

Authors and Affiliations

  • Sven Hartmann
    • 1
  • Sebastian Link
    • 1
  1. 1.Information Science Research CentreMassey UniversityNew Zealand

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