Before revision:  Motivated by engineering considerations, we then consider a natural decomposition of any master equation that implements a given function into a sequence of "hidden" timesteps, demarcated by changes in the set of allowed transitions between states.
After revision:  Motivated by engineering considerations, we then consider a natural decomposition of any master equation implementing a given map can be decomposed into a sequence of "hidden" timesteps, demarcated by changes in the set of allowed transitions between states.