EXTERNAL SCHEMA FACILITY FOR CODFASYL 1978.

A new external schema facility more powerful than that presently offered by CODASYL subschemes is proposed as an extension to the CODASYL Data Description Language. This facility offers applications programmers a virtual data base. This data base, while derivable from the stored data base, is not constrained to resemble it in form; thus programmers will use records formatted, not like those stored in the common data base, but like the cognitive structures employed in program development. A possible language for external schema definition is introduced.