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Author Codd, E. F.
Source ACM Digital Library
Content type Text
Publisher Association for Computing Machinery (ACM)
File Format PDF
Language English
Subject Keyword Derivability ♦ Composition ♦ Redundancy ♦ Consistency ♦ Join ♦ Networks of data ♦ Relations ♦ Predicate calculus ♦ Security ♦ Data base ♦ Hierarchies of data ♦ Data integrity ♦ Data organization ♦ Retrieval language ♦ Data bank ♦ Data structure
Abstract 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 changed and even when some aspects of the external representation are changed. Changes in data representation will often be needed as a result of changes in query, update, and report traffic and natural growth in the types of stored information.Existing noninferential, formatted data systems provide users with tree-structured files or slightly more general network models of the data. In Section 1, inadequacies of these models are discussed. A model based on n-ary relations, a normal form for data base relations, and the concept of a universal data sublanguage are introduced. In Section 2, certain operations on relations (other than logical inference) are discussed and applied to the problems of redundancy and consistency in the user's model.
Description Affiliation: IBM Research Lab, San Jose, CA (Codd, E. F.)
Age Range 18 to 22 years ♦ above 22 year
Educational Use Research
Education Level UG and PG
Learning Resource Type Article
Publisher Date 2005-08-01
Publisher Place New York
Journal Communications of the ACM (CACM)
Volume Number 26
Issue Number 1
Page Count 6
Starting Page 64
Ending Page 69


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Source: ACM Digital Library