A method of providing interoperability between an open standard directory service and a proprietary database. The directory is represented as a mapping tree, consistent with directory service protocols such as X.500 or LDAP. The mapping tree node associated with the proprietary database is configured as a null suffix mapping tree entry, so that database mapping tree node replaces root of the mapping tree and the proprietary database the default backend of the directory service. The core server of the directory service is configured to recognize the null suffix mapping tree entry. All directory service operations are routed to a pre-operation plug-in that handles operations in the proprietary database, and remaining operations are redirected to the core server, preserving default functionality of the directory service. Normal data constraints are suspended for operations performed in the proprietary database.