The class of decision problems solvable in O(f(n))-space with error probability at most 1/3, by a Turing machine that halts on every input and every random tape setting.
Contains RHSPACE(f(n)).
Is contained in DSPACE(f(n)3/2) [SZ95].
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)).
Has the same relation to BPHSPACE(f(n)) as RP does to BPP.