“…ramified recurrence has been used to obtain machine-independent characterizations of several major complexity classes, such as polynomial time [4,22] and polynomial space [26,36], as well as alternating log time [8,27], alternating poly-log time [8], NC [23,35], logarithmic space [34], monotonic PTime [13], linear space [21,15,22], NP [2,37], the poly-time hierarchy [3], exponential time [10], Kalmarelementary resources [24], and probabilistic polynomial time [20]. The method is all the more of interest given the roots of ramification in the foundations of mathematics [42,41], thus bridging abstraction levels in set-theory and type-theory to computational complexity classes.…”