Processing Unions of Conjunctive Queries with Negation under Limited Access Patterns
EDBT, pp. 422-440, 2004.
We study the problem of answering queries over sources with limited access patterns. The problem is to decide whether a given query Q is feasible, i.e., equivalent to an executable query Q0 that observes the limited access patterns given by the sources. We characterize the complexity of deciding feasibility for the classes CQ¬ (conjunctiv...More
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