Approximate query processing using multilayered database model and inference control

In this thesis. we describe a query approximation system which uses the Multi-Layered Database (MLDB), and then proceeds to analyze different inference problems that may occur in MLDB. MLDB is a collection of summarized relational data generated using domain based concept hierarchies, which provides an approximate result even when the user does not have access. The system, we described not only generates approximate answers to queries based on the user\u27s access control level but also enforces inference checking, thus preserving both privacy of data and purpose of the application --Abstract, page iv