18. The method of claim 16 further comprising defining the set of spans of contiguous words in the source sentence by requiring that each span in the set begin with a source word that is aligned with at least one target word and end with a source word that is aligned with at least one target word.
18. The method of claim 16 further comprising defining the set of spans of contiguous words in the source sentence by requiring that each span in the set begin with a source word that is aligned with at least one target word and end with a source word that is aligned with at least one target word. 19. The method of claim 18 further comprising, after designating the span of contiguous words in the source sentence and the span of contiguous words in the target sentence as a phrase alignment pair, shifting the beginning of the span of contiguous words in the source sentence so that the span of contiguous words in the source sentence covers more words and begins with a word that is not aligned with a word in the target sentence to form an expanded span of contiguous words in the source sentence and designating the expanded span of contiguous words in the source sentence and the span of contiguous words in the target sentence as a phrase alignment pair.