We present an accurate word alignment algorithm that heavily exploits source and target-language syntax. Using a discriminative framework and an efficient bottom-up search algorithm, we train a model of hundreds of thousands of syntactic features. Our new model (1) helps us to very accurately model syntactic transformations between languages; (2) is language-independent; and (3) with automatic feature extraction, assists system developers in obtaining good word-alignment performance off-the-shelf when tackling new language pairs. We analyze the impact of our features, describe inference under the model, and demonstrate significant alignment and translation quality improvements over already-powerful baselines trained on very large corpora. We observe translation quality improvements corresponding to 1.0 and 1.3 BLEU for Arabic-English and Chinese-English, respectively.
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