Abstract
We study the containment, satisfiability, and validity problems for conjunctive queries over trees with respect to a schema. We show that conjunctive query containment and validity are 2EXPTIME-complete w.r.t. a schema (DTD or Relax NG). Furthermore, we show that satisfiability for conjunctive queries w.r.t. a schema can be decided in NP. The problem is NP-hard already for queries using only one kind of axis. Finally, we consider conjunctive queries that can test for equalities and inequalities of data values. Here, satisfiability and validity are decidable, but containment is undecidable, even without schema information. On the other hand, containment w.r.t. a schema becomes decidable again if the “larger” query is not allowed to use both equalities and inequalities.
This work was supported by the DFG Grant SCHW678/3-1.
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Björklund, H., Martens, W., Schwentick, T. (2008). Optimizing Conjunctive Queries over Trees Using Schema Information. In: Ochmański, E., Tyszkiewicz, J. (eds) Mathematical Foundations of Computer Science 2008. MFCS 2008. Lecture Notes in Computer Science, vol 5162. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-85238-4_10
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DOI: https://doi.org/10.1007/978-3-540-85238-4_10
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