We present a new release of the Paraphrase Database. PPDB 2.0 includes a discriminatively re-ranked set of paraphrases that achieve a higher correlation with human judgments than PPDB 1.0's heuristic rankings. Each paraphrase pair in the database now also includes finegrained entailment relations, word embedding similarities, and style annotations.

This paper describes a lexical trigger model for statistical machine translation. We present various methods using triplets incorporating long-distance dependencies that can go beyond the local context of phrases or n-gram based language models. We evaluate the presented methods on two translation tasks in a reranking framework and compare it to the related IBM model 1. We show slightly improved translation quality in terms of BLEU and TER and address various constraints to speed up the training based on Expectation-Maximization and to lower the overall number of triplets without loss in translation performance.

The validity of applying paraphrase rules depends on the domain of the text that they are being applied to. We develop a novel method for extracting domainspecific paraphrases. We adapt the bilingual pivoting paraphrase method to bias the training data to be more like our target domain of biology. Our best model results in higher precision while retaining complete recall, giving a 10% relative improvement in AUC.

Paraphrase evaluation is typically done either manually or through indirect, taskbased evaluation. We introduce an intrinsic evaluation PARADIGM which measures the goodness of paraphrase collections that are represented using synchronous grammars. We formulate two measures that evaluate these paraphrase grammars using gold standard sentential paraphrases drawn from a monolingual parallel corpus. The first measure calculates how often a paraphrase grammar is able to synchronously parse the sentence pairs in the corpus. The second measure enumerates paraphrase rules from the monolingual parallel corpus and calculates the overlap between this reference paraphrase collection and the paraphrase resource being evaluated. We demonstrate the use of these evaluation metrics on paraphrase collections derived from three different data types: multiple translations of classic French novels, comparable sentence pairs drawn from different newspapers, and bilingual parallel corpora. We show that PARADIGM correlates with human judgments more strongly than BLEU on a task-based evaluation of paraphrase quality.

We describe Joshua, an open source toolkit for statistical machine translation. Joshua implements all of the algorithms required for synchronous context free grammars (SCFGs): chart-parsing, ngram language model integration, beamand cube-pruning, and k-best extraction. The toolkit also implements suffix-array grammar extraction and minimum error rate training. It uses parallel and distributed computing techniques for scalability. We demonstrate that the toolkit achieves state of the art translation performance on the WMT09 French-English translation task.