The Complexity of Order Dependency Inference
نویسندگان
چکیده
Dependencies play an important role in database theory. We study order dependencies (ODs)—and unidirectional order dependencies (UODs), sub-class of ODs—which describe the relationships among lexicographical orderings of sets of tuples. We investigate the inference problem for order dependencies. We establish the following: (i) a sound and complete chase procedure for ODs for testing logical implication demonstrating its decidability, but prove the undecidability of the inference problem for ODs with inclusion dependencies; (ii) a proof of co-NP-completeness for the inference problem for the subclass of UODs; (iii) a proof of co-NP-completeness for the inference problem of functional dependencies (FDs) from ODs in general, but demonstrate linear time complexity for the inference of FDs from UODs; and (iv) a sound and complete inference algorithm for sets of UODs over a natural domain.
منابع مشابه
Expressiveness and Complexity of Order Dependencies
Dependencies play an important role in databases. We study order dependencies (ODs)—and unidirectional order dependencies (UODs), a proper sub-class of ODs—which describe the relationships among lexicographical orderings of sets of tuples. We consider lexicographical ordering, as by the order-by operator in SQL, because this is the notion of order used in SQL and within query optimization. Our ...
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