XPath satisfiability in the presence of DTDs
Proceedings of the twenty-fourth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
On testing satisfiability of tree pattern queries
VLDB '04 Proceedings of the Thirtieth international conference on Very large data bases - Volume 30
XPath satisfiability in the presence of DTDs
Journal of the ACM (JACM)
Satisfiability of downward XPath with data equality tests
Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Satisfiability of XPath queries with sibling axes
DBPL'05 Proceedings of the 10th international conference on Database Programming Languages
XPath query satisfiability is in PTIME for real-world DTDs
XSym'07 Proceedings of the 5th international conference on Database and XML Technologies
Extending the tractability results on XPath satisfiability with sibling axes
XSym'10 Proceedings of the 7th international XML database conference on Database and XML technologies
Satisfiability of simple Xpath fragments under fixed DTDs
BNCOD'11 Proceedings of the 28th British national conference on Advances in databases
XPath satisfiability with downward and sibling axes is tractable under most of real-world DTDs
Proceedings of the twelfth international workshop on Web information and data management
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For an XPath expression q and a DTD D, q is satisfiable under D if there exists an XML document t such that t is valid against D and that the answer of q on t is nonempty. Evaluating an unsatisfiable XPath expression is meaningless, since such an expression can always be replaced by an empty set without evaluating it. However, it is shown that the XPath satisfiability problem is intractable for a large number of XPath fragments. In this paper, we consider simple XPath fragments under two restrictions; (i) only a label can be specified as a node test and (ii) operators such as qualifier ([]) and union (∪) are not allowed. We first show that, for some small XPath fragments under the above restrictions, the satisfiability problem is still NP-complete. Then we show that there exist XPath fragments, containing the above small fragments, for which the satisfiability problem is in PTIME under duplicate-free DTDs.