<P> In 1974, IBM began developing System R, a research project to develop a prototype RDBMS . However, the first commercially available RDBMS was Oracle, released in 1979 by Relational Software, now Oracle Corporation . Other examples of an RDBMS include DB2, SAP Sybase ASE, and Informix . In 1984, the first RDBMS for Macintosh began being developed, code - named Silver Surfer, it was later released in 1987 as 4th Dimension and known today as 4D . </P> <P> The term "relational database" was invented by E.F. Codd at IBM in 1970 . Codd introduced the term in his research paper "A Relational Model of Data for Large Shared Data Banks". In this paper and later papers, he defined what he meant by "relational". One well - known definition of what constitutes a relational database system is composed of Codd's 12 rules . However, many of the early implementations of the relational model did not conform to all of Codd's rules, so the term gradually came to describe a broader class of database systems, which at a minimum: </P> <Ul> <Li> Present the data to the user as relations (a presentation in tabular form, i.e. as a collection of tables with each table consisting of a set of rows and columns); </Li> <Li> Provide relational operators to manipulate the data in tabular form . </Li> </Ul> <Li> Present the data to the user as relations (a presentation in tabular form, i.e. as a collection of tables with each table consisting of a set of rows and columns); </Li>

Explain the meaning of a relational database management system