Track:
Query Optimization
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Abstract:
We examine the query planning problem in information integration systems in the presence of sources that contain disjunctive information. We show that datalog, the language of choice for representing query plans in information integration systems, is not sufficiently expressive in this case. We prove that disjunctive datalog with inequality is sufficiently expressive, and present a construction of query plans that are guaranteed to extract all available information from disjunctive sources.