< database > An operational methodolgy, founded on predicate calculus , dealing with descripitive expressions that are equivalent to the operations of relational algebra . Codd's reduction algorithm can convert from relational calculus to relational algebra .
Two forms of the relational calculus exist: the tuple calculus and the domain calculus .
["An Introduction To Database Systems" (6th ed), C. J. Date, Addison Wesley].
(1998-10-05)