Secure query-processing strategies

Strategies for secure query processing multilevel-security database management systems are proposed. They are carried out by query modification, a technique that has been used for enforcing integrity constraints and providing view mechanisms. The technique consists of replacing the query the user presents with one that, when evaluated, will perform the desired function. In the case of a view mechanism, the names of views referenced in the query are replaced by the definitions of the views in terms of base relations. The basic strategy and two variants-adding environmental information and using graphs-are described. The performance of the strategies is examined