If x contains fewer a's than b's, then PRODUCE And if a's and b's appear equally often in x, then PRODUCE(x) is the union of the two sets.
while the x-to-z mapping is not a regular relation under this grammar, at least PRODUCE(x) is a regular set for each x-just as finite-state OT constraints, notably Koskenniemi's (1983) two-level model, which like OT used finite-state constraints on candidates y that encoded an alignment between underlying x and surface z. guarantees.