Abstract: A tool for assisting an operator to detect security violations in a multilevel secure database. The database stores data classified at a plurality of security levels, where the different users of the database are cleared to different security levels and access the database through a multilevel secure database management system. Security constraints are represented in conceptual structures, rules, or frames, and operator communication with the constraint representation is provided by a user interface. An inference engine uses reasoning strategies on the security-constraint representations base to detect security violations in the database by inference.