This paper reports some implementation work done within the MULTI SAFE database protection research project group at Virginia Tech. It describes the evolution of an approach to database security from a formal model of predicate-based protection, through an implementation model, to an on-going implementation. The implementation model is based on a relational database approach to the management of protection information (stored representations of authorizations). Classes of access decision dependency are reviewed. Protection policies, design deci¬sions, and special implementation problems are discussed. Detailed examples are used to illustrate the use of this flexible and generalized approach to database security within the MULTI SAFE system architecture.