1. A data processing system having: input means providing input signals; a visual display; storage means providing working storage and database storage; and a processor having means for controlling said visual display, means for reading and writing said storage means, means for responding to said input signals, and access means for retrieving record occurrence signals from said database storage and for storing retrieved record occurrence signals in said working storage, characterized in having means in said working storage for providing format signals representative of a predefined display format data structure means in said database storage for providing description signal representative of a description data structure describing a data dictionary for describing the elements of a relational database, said description data structure being modeled as relations in a relational database, and interactive and nonprocedural data dictionary defining means for controlling said display to display elements comprising representations of record occurrences retrieved from said description data structure signals and representations of selectable operations, in a format derived from said display format data structure signals, accepting from said input means, input signals representing element enumeration, characters, and operation selection, and allocating storage within said database storage and placing therein signals representative of a data dictionary data structure responsive to said description data structure and to said input signals, said data dictionary data structure being modeled as relations in a relational database and being descriptive of a particular other relational database.