Same as RL, but for O(f(n))-space instead of logarithmic-space. (Just as an RL machine must run in polynomial time, so an RSPACE(f(n)) machine must run in 2O(f(n)) time.)
Contained in NSPACE(f(n)) and BPSPACE(f(n)).
The class of decision problems solvable in O(f(n))-space with error probability at most 1/3, by a Turing machine that halts with probability 1 on every input.
Contains RSPACE(f(n)) and BPHSPACE(f(n)).