 A central topic in contemporary computability theory is the study of relative computability—i.e., if we assume that we are able to decide membership in a given set or compute a given function, which other sets or functions would we be able to decide or compute? This question may be studied using the notion of a reduction of one set \(A\) to another \(B\) which was introduced informally by Kolmogorov (1932) as a means of transforming a “solution” of \(A\) into a “solution” of  \(B\).[23]  Turing (1939) provided the first formal definition of a computational reduction in his study of ordinal logics. However, it was Post who first proposed to systematically study reducibility notions and their associated degree structures in his highly influential paper “Recursively enumerable sets of positive integers and their decision problems” (1944).