We investigate properties of the relativized AC and NC hierarchies in
their DLOGTIME-, respectively, ALOGTIME-uniform setting and show that
these hierarchies can be characterized in terms of adaptive reducibili
ty in deterministic (poly)logarithmic time, i.e. in time O(log n)(i) f
or i greater than or equal to 0. Using this characterization, we subst
antially generalize various previous results concerning the structure
of the two hierarchies.