A RELATIONAL MODEL OF DATA FOR LARGE SHARED DATA-BANKS (REPRINTED FROM COMMUNICATIONS OF THE ACM, JUNE, PG 377-87, 1970)

Future users of large data banks must be protected from having to know how the data is [sic] organized in the machine (the internal represen tation). A prompting service which supplies such information is not a satisfactory solution. Activities of users at terminals and most appli cation programs should remain unaffected when the interned representat ion of data is changed and even when some aspects of the external repr esentation are changed. Changes in data representation will often be n eeded as a result of changes in query, update, and report traffic and natural growth in the types of stored information. Existing noninferen tial, formatted data systems provide users with tree-structured files or slightly more general network models of the data. Inadequacies of t hese models are discussed. A model based on n-ary relations, a normal form for data base relations, and the concept of a universal data subl anguage are introduced.