For further understanding, we first describe some definitions.
given a word-aligned sentence pair (F I 1 , E J 1 , A), an alignment set A set (i) is the set of target word positions that aligned to the source word F i i : For example, in Figure 1, the alignment set for the Chinese word "shaoshu 3 " is the alignment span for the Chinese word "shaoshu 3 " is A span (3) = [5, 10].