1. A method, comprising: receiving, by a surface realizer of a paraphrase generation system, a plurality of bidirectional disjunctive logical forms, wherein the plurality of bidirectional disjunctive logical forms includes two directional disjunctions of differences between a first logical form of a first sentence and a second logical form of a second sentence; realizing, by the surface realizer, the plurality of bidirectional disjunctive logical forms to generate first paraphrases of the first and second sentences; determining a first score for a third paraphrase of the first paraphrases; determining a second score for a fourth paraphrase of the first paraphrases, wherein the first score is higher than the second score based in part on a first syntactic variation between the third paraphrase and the first sentence and the second sentence being greater than a second syntactic variation between the fourth paraphrase and the first sentence and the second sentence; and pruning, by the paraphrase generation system, the first paraphrases to generate second paraphrases, wherein the first paraphrases are pruned based on the first score and the second score such that the third paraphrase is included in the second paraphrases and the fourth paraphrase is not included in the second paraphrases based on the first score being higher than the second score.