The paper describes a new approach to maintaining consistency between objects which reside in dynamic, shared databases and copies of those objects which are cached in application knowledge-bases. The approach relies on an intelligent interface to active databases, a mediator for approximate consistency (MAC). The MAC permits applications to specify their consistency requirements declaratively, using a simple extension of a frame-based representation language. It then automatically generates the interfaces and database objects necessary to enforce those consistency requirements, shielding the knowledge-base developer from the implementation details of consistency maintenance. While the authors focus on knowledge-base/database consistency issues, the approach is applicable to any component of a multidatabase federation which needs to cache dynamic data and to enforce some degree of consistency between itself and other components in the federation. >