  Let H be a pseudovariety of groups in which the kappa-word problem is
decidable. Here, kappa denotes the canonical implicit signature, which consists
of the multiplication and the (omega-1)-power. We prove that the kappa-word
problem is also decidable over DRH, the pseudovariety of all finite semigroups
whose regular R-classes lie in H. Further, we present a canonical form for
elements in the free kappa-semigroup over DRH, based on the knowledge of a
canonical form for elements in the free kappa-semigroup over H. This extends
work of Almeida and Zeitoun on the pseudovariety of all finite R-trivial
semigroups.
