Relational Model.pdf

E.F. Codd's paper introduces a relational model of data for large shared data banks, aiming to protect users from knowing how data is organized in the machine. The model is based on n-ary relations, a normal form for data base relations, and a universal data sublanguage. Key features include:

Data independence: application programs and terminal activities remain unaffected by changes in internal data representation.
Relational view: describes data with its natural structure, without superimposing additional structure for machine representation purposes.
Normal form: ensures data consistency and reduces redundancy.
Universal data sublanguage: provides a high-level data language for maximal independence between programs and machine representation.

The paper discusses inadequacies of existing non-inferential, formatted data systems, including:

Ordering dependence: application programs assuming a specific stored ordering of data.
Indexing dependence: application programs relying on specific indexing schemes.
* Access path dependence: application programs assuming specific access paths to data.

Codd's relational model addresses these issues, providing a sound basis for treating derivability, redundancy, and consistency of relations. The model permits a clearer evaluation of the scope and logical limitations of present formatted data systems and competing representations of data within a single system.