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ICDT
2009
ACM

Containment of conjunctive queries on annotated relations

14 years 11 months ago
Containment of conjunctive queries on annotated relations
We study containment and equivalence of (unions of) conjunctive queries on relations annotated with elements of a commutative semiring. Such relations and the semantics of positive relational queries on them were introduced in a recent paper as a generalization of set semantics, bag semantics, incomplete databases, and databases annotated with various kinds of provenance information. We obtain positive decidability results and complexity characterizations for databases with lineage, why-provenance, and provenance polynomial annotations, for both conjunctive queries and unions of conjunctive queries. At least one of these results is surprising given that provenance polynomial annotations seem "more expressive" than bag semantics and under the latter, containment of unions of conjunctive queries is known to be undecidable. The decision procedures rely on interesting variations on the notion of containment mappings. We also show that for any positive semiring (a very large clas...
Todd J. Green
Added 21 Nov 2009
Updated 21 Nov 2009
Type Conference
Year 2009
Where ICDT
Authors Todd J. Green
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