1. Relational model

The relational data model emerged in the early 1970s as a simple, rigorous and powerful mathematical formalism for describing and manipulating data. Ten years later, the first database management software (DBMS) made it possible to build large databases and access them easily.

This model uses two-dimensional tables to store data. Processing rules (normal forms) guarantee data consistency, avoiding anomalies during updates.

The data in a relational database is manipulated using declarative languages (SQL: Structured Query Language or QBE: Query By Example ). The ease of use of these languages, as opposed to the complexity of programming languages, has enabled users to access data much more simply.

Relational databases have gradually supplanted other types of database (inverted files, hierarchical databases and networks)....