The Relational Database Management System (often called RDBMS for short) has become the dominant DBMS in use today, with estimated sales of approximately $15–$20 billion per year ($50 billion with tools sales included), and growing at a rate of about 25 percent per year. The DBMS represents the second generation of DBMS and is based on the relational data model proposed by Dr E.F. Codd in his seminal paper ‘A Relational Model of Data for Large Shared Data Banks’ in 1970.
An integrated collection of concepts for describing data, relationships between data, and constraints on the data used by an organization. A model is a representation of ‘real world’ objects and events, and their associations. It concentrates on the essential, inherent aspects of an organization and ignores the accidental properties. A data model attempts to represent the data
requirements of the organization, or the part of the organization, that you wish to model. It should provide the basic concepts and notations that will allow database designers and end-users to communicate their understanding of the organizational data unambiguously and accurately.
The relational model is based on the mathematical concept of a relation, which is physically represented as a table.