1. A data processing system, comprising: a plurality of application programs, each application program requiring an input database table having a predefined set of attributes, each predefined set of attributes defining a class of database tables; a relational database for storing a set of database tables, the set of database tables comprising at least one combination database table, each database table having at least one of the predefined sets of attributes: a user interface for entering the at least one combination database table by entering a combination of at least first and second database tables of the set of database tables and for selecting at least first entries from the first database table and second entries from the second database table, and for entering a selection of one of the application programs; a first mapping table for storing assignments of sub-sets of the set of database tables to the classes; and processing means for execution of the selected one of the application programs by reading the database tables of the set of database tables that are assigned to the class required by the selected application program.