Turing reduction
In computability theory, a Turing reduction from a decision problem formula_1 to a decision problem formula_2 is an oracle machine which decides problem formula_1 given an oracle for formula_2 (Rogers 1967, Soare 1987). It can be understood as an algorithm that could be used to solve formula_1 if it had available to it a subroutine for solving "B". The concept can be analogously applied to function problems.