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    Minimising simple XPath expressions

    Wood, Peter (2001) Minimising simple XPath expressions. In: Mecca, G. and Simeon, J. (eds.) WebDB 2001: Proceedings of the Fourth International Workshop on the Web and Databases. WebDB, pp. 13-18.

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    We consider a subset of XPath expressions, called simple XPath expressions, which correspond to a class of conjunctive queries. We show that, in the absence of a DTD, each simple XPath expression has a unique minimal equivalent expression which can be found in polynomial time. We then consider D-equivalence, the equivalence of expressions with respect to the set of documents valid for a given DTD D. We show that a simple XPath expression P does not necessarily have a unique minimal D-equivalent expression. However, if P is reduced (there are no wildcards in it), then there is a unique minimal equivalent expression, but we show that deciding whether two reduced expressions are D-equivalent is coNP-hard.


    Item Type: Book Section
    School: Birkbeck Faculties and Schools > Faculty of Science > School of Computing and Mathematical Sciences
    Depositing User: Sarah Hall
    Date Deposited: 18 Oct 2021 14:49
    Last Modified: 09 Aug 2023 12:52


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