While I'm not a huge fan of it, one of the other databases implementing this functionality does so using the syntax:
WITH ITERATIVE R AS '(' R0 ITERATE Ri UNTIL N (ITERATIONS | UPDATES) ')' Qf
Where N in ITERATIONS represents termination at an explicit count and, in UPDATES, represents termination after Ri updates more than n rows on table R.
Sent too soon :) One of the main reasons I dislike the above is that it assumes N is known. In some cases, however, you really need termination upon a condition.
