Obtaining Information about Queries behind Views and Dependencies

TL;DR

This paper explores how to determine query answers and containment in databases with views and dependencies, providing algorithms and complexity analysis relevant to security and data management.

Contribution

Introduces algorithms for query answering and containment with conjunctive queries and weakly acyclic dependencies, along with complexity results under security-focused measures.

Findings

Algorithms for conjunctive queries and weakly acyclic dependencies

Complexity analysis under security-relevant measures

Applications in access control and secure data management

Abstract

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.