ATabase> 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)
