The dot-depth hierarchy versus iterated block products of DA

Abstract

Like the sequence of the classes of the dot-depth hierarchy the sequence of classes given by the n-fold iterated block product of DA has the class of starfree regular languages as its limit. It is shown that this DA-block-product hierarchy grows more slowly than the dot-depth hierarchy: in fact already Sigma-2 of the dot-depth hierarchy contains properness witnesses for all levels of the DA-block-product hierarchy.