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Union rewritings for XPath fragments
(2011)
In this paper, we study the problem of finding an equivalent rewriting of an XPath query using multiple views, and we show that the union operator may be required in order to find such a rewriting. In particular, focusing ...
Query containment under bag and bag-set semantics
(2010)
Conjunctive queries (CQs) are at the core of query languages encountered in many logic-based research fields such as AI, or database systems. The majority of existing work assumes set semantics but often in real applications ...