We consider the problems of finding and determining certain query answers and of determining containment between queries; each problem is formulated in presence of materialized views and dependencies under the closed-world assumption. We show a tight relationship between the problems in this setting. Further, we introduce algorithms for solving each problem for those inputs where all the queries and views are conjunctive, and the dependencies are embedded weakly acyclic. We also determine the complexity of each problem under the security-relevant complexity measure introduced by Zhang and Mendelzon in 2005. The problems studied in this paper are fundamental in ensuring correct specification of database access-control policies, in particular in case of fine-grained access control. Our approaches can also be applied in the areas of inference control, secure data publishing, and database auditing.
The work @cite_1 by Zhang and Mendelzon introduced and solved the problem of conditional containment'' between two CQ queries in presence of materialized CQ views, under CWA and in the absence of dependencies. @cite_1 also introduced a security-relevant complexity metric, under which their problem is @math complete. ( @cite_1 also provides an excellent overview of the connections of the query-containment problem of @cite_1 to database-theory literature.) In our work, we add dependencies to the formulation of the problem of @cite_1 , and extend the approach of @cite_1 , both to solve the resulting problem in the CQ weakly acyclic setting and to analyze the complexity of the problem. We also uncover a tight relationship of the problem with the problems of finding and determining certain query answers, under CWA in presence of view materializations and of dependencies.
@cite_1
1508622259
A recent proposal for database access control consists of defining “authorization views” that specify the accessible data, and declaring a query valid if it can be completely rewritten using the views. Unlike traditional work in query rewriting using views, the rewritten query needs to be equivalent to the original query only over the set of database states that agree with a given set of materializations for the authorization views. With this motivation, we study conditional query containment, i.e. , containment over states that agree on a set of materialized views. We give an algorithm to test conditional containment of conjunctive queries with respect to a set of materialized conjunctive views. We show the problem is @math -complete. Based on the algorithm, we give a test for a query to be conditionally authorized given a set of materialized authorization views.