 The notion of relative computability mentioned at the beginning of this section is now standardly analyzed in terms of computability in a set \(A \subseteq \mathbb{N}\). Informally, we say that a function \(f(\vec{x})\) is computable in \(A\) just in case there exists an algorithm which is effective in the traditional sense with the exception of the fact its computation may rely on computing one or more values \(\chi_A(y)\). These values are in turn assumed to be available to the algorithm in a single step even though \(\chi_A(y)\) may not itself be computable—e.g., if \(A = K\).