A paraphrase that is totally transformed from the source sentence and another that is almost unchanged may get the same score.
we propose two strategies, i.e., PR1 and PR2, to compute the paraphrase rate: Here, PR1 is defined based on word overlapping rate, in which OL(S, T ) denotes the number of overlapping words between a paraphrase T and its source sentence S, L(S) denotes the number of words in S. PR2 is defined based on edit distance, in which ED(S, T ) denotes the edit distance between T and S. Obviously, PR1 only measures the percentage of words that are changed from S to T , whereas PR2 further takes word order changes into consideration.