In the absence of a good stopping criterion, the resulting list of patterns must be manually reviewed by a human; otherwise one can set ad-hoc thresholds, e.g., on the number of allowed iterations, as in (Riloff and Jones, 1999), or else to resort to supervised training to determine such thresholds-which is unsatisfactory when our goal from the outset is to try to limit supervision.
the lack of natural stopping criteria renders these algorithms less unsupervised than one would hope.