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Future users of large data banks must be protected from having to know how the data is organized in the machine (the internal representation). A prompting service which supplies such information is not a satisfactory solution. Activities of users at terminals and most application programs should remain unaffected when the internal representation of data is(More)
During the last three or four years several investigators have been exploring “semantic models” for formatted databases. The intent is to capture (in a more or less formal way) more of the meaning of the data so that database design can become more systematic and the database system itself can behave more intelligently. Two major thrusts are(More)
During the last three or four years several investigators have been exploring 'semantic models' for formatted data bases. The intent is to capture (in a more or less formal way) more of the meaning of the data, so that data base design can become more systematic and the data base system itself can behave more intelligently. Two major thrusts are clear:1)(More)
  • E. F. Codd
  • 1980
It is a combination of three components: 1) a collection of data structure types (the building blocks of any database that conforms to the model); 2) a collection of operators or inferencing rules, which can be applied to any valid instances of the data types listed in (1), to retrieve or derive data from any parts of those structures in any combinations(More)