Relational
Model
The relational model for database
management is a database model based on predicate logic and set theory. It was
first formulated and proposed in 1969 by Edgar Codd with aims that included
avoiding, without loss of completeness, the need to write computer programs to
express database queries and enforce database integrity constraints.
The
foundation for the relational model included important works published by Georg
Cantor (1874) and D.L. Childs (1968). Cantor was a 19th century German
mathematician who published a number of articles and was the principal creator
of set theory. Childs is an American mathematician whose "Description of a
Set-Theoretic Data Structure" was
cited by Codd in his seminal 1970 paper "A
Relational Model of Data for Large Shared Data Banks". Childs' STDS uses set
theory as the basis for querying data using set operations such as union,
intersection, domain, range, restriction, cardinality and Cartesian product. The
use of sets and set operations provided independence from physical data
structures, a pioneering concept at the time.
The relational model allows users to simply specify what
data they require, not how to get them. This is referred to as data independence
and is a key contribution of the relational model.Older models are referred to
as navigational as users must navigate through the data and follow pointers from
one datum to another.
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