Reasoning about Domain Semantics over Relations, Bags, Partial Relations and Partial Bags

摘要: Quality database schemata must capture both the structure and semantics of domain interest. Classes data dependencies have been studied extensively to model do- main semantics. Traditionally, theory has limited relations. In practice, duplicate partial information are permitted occur in instances. These features supported make processing more efficient. We study implication problem for an expressive class over all structures that arise from two features. include bags permit tuples, relations null marker occurrences, tuples occurrences. The encompasses uniqueness constraints, functional multivalued dependencies. establish axiomatizations sharp upper bounds worst-case time complexity problem.