1. A database management system which runs on a computer serving a plurality of users and which interfaces a plurality of user application programs to a database for managing sets of data stored on said database comprising: data dictionary means for specifying relationships between each of said user application programs and said sets of said data stored in said database associated with each of said user application program; data model means for controlling the definition of the specified relationships of said data dictionary; query means responsive to change commands from a user application program for modifying said data model; wherein said query means includes means responsive to said change commands for changing said data dictionary to correspond to said data model changes; and said query means further includes means responsive to a data request from said user application program for accessing the requested sets of said data from said database.