Codd, 1985

According to E. F. Codd, "For any system that is claimed to be a relational database management system, that system must be able to manage data entirely through its relational capabilities."

Codd specified the relational data model in 1970 and he identified 12 rules to determine whether a DBMS is relational and to what extent it is relational. The above statement is known as rule zero. It is fundamental in evaluating relational database management systems.

from Codd, E. F. (1985), "Is Your DBMS Really Relational?" and "Does Your DBMS Run By the Rules?", ComputerWorld, October 14 and October 21.

appeared in DSS News, February 17, 2002, Vol. 3, No. 4