A well-designed database must balance security-control and operational efficiency. Consequently, the principal objective is to develop a design theory for multilevel databases unifying security (access-control and inference-control) and efficiency aspects in a dynamic environment. This project identifies the key constraints imposed by these aspects and formulates practical guidelines for database design. Emphasis is placed on data dependencies fundamental to inference-control and anomaly- elimination. The approach employed deals with a lattice-theoretic relational model enforcing database security by abstracting or clouding sensitive information in user views. The model uses "contexts" constructed from natural equivalences. Contexts induce multilevel relations capable of holding abstraction, and support a rich and highly secure data language. Contexts also incorporate semantics in abstraction; this helps balance user convenience and database security. The lattice-theoretic framework simplifies the investigation; classical design issues are also readily mapped to their multilevel formulations. The investigation also focuses on an Oracle implementation of the security-control model. Special consideration is given to implementing the query-handling facility. The results of this research will have a significant impact on the design of databases handling abstract information, and particularly those supporting AI and expert systems applications, as robust and efficient security-control is a critical issue facing database and knowledge-base designers. //
