<Li> The relational division operation is a slightly more complex operation and essentially involves using the tuples of one relation (the dividend) to partition a second relation (the divisor). The relational division operator is effectively the opposite of the cartesian product operator (hence the name). </Li> <P> Other operators have been introduced or proposed since Codd's introduction of the original eight including relational comparison operators and extensions that offer support for nesting and hierarchical data, among others . </P> <P> Normalization was first proposed by Codd as an integral part of the relational model . It encompasses a set of procedures designed to eliminate non-simple domains (non-atomic values) and the redundancy (duplication) of data, which in turn prevents data manipulation anomalies and loss of data integrity . The most common forms of normalization applied to databases are called the normal forms . </P> <P> Distributed Relational Database Architecture (DRDA) was designed by a workgroup within IBM in the period 1988 to 1994 . DRDA enables network connected relational databases to cooperate to fulfill SQL requests . The messages, protocols, and structural components of DRDA are defined by the Distributed Data Management Architecture . </P>

In a relational model the rows are called attributes and the columns are called tuples