Abstract :
We propose as an extension to the CODASYL Data Description Language a new external schema facility more powerful than that presently offered by CODASYL subschemas. We note that the present facility relies on records and set that closely resemble those employed in the schema, with unfortunate implications for programmer productivity, data independence, and communications channel traffic. We propose instead a powerful external schema facility that, in effect, 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 scheme definition is introduced.
