1 and 2 are parameters of this schema; here 1 = 1 or 1 = 2 and 2 = 1.
the 50 best (i.e., the 50 highest probability) parses of a sentence often contain considerably better parses (in terms of f -score); this paper describes a 50-best parsing al-gorithm with an oracle f -score of 96.8 on the same data.