Abstract: The present invention addresses the problem of implementing X.500 using an SQL product. The present application discloses an application of X.500 to a relational database, a database design and use of the database to perform X.500 services. Particularly, the disclosure relates to implementation using an RDBMS (Relational DataBase Management System). One invention disclosed resides around service modelling, the processing of arbitrary data using a fixed set of queries/services. Another invention resides in the implementation of a disk based model using relational queries to satisfy X.500 services and enables benefits of RDBMS to be exploited. Further, the invention provides an SQL based X.500 application that can perform at subsecond speed and is relatively unaffected by the size of database, DIT shape, type of data or complexity of service, including aliases.