Most stateof-the-art SMT systems treat grammatical elements in exactly the same way as content words, and rely on general-purpose phrasal translations and target language models to generate these elements (e.g., Och and Ney, 2002;Koehn et al., 2003;Quirk et al., 2005;Chiang, 2005;Galley et al., 2006).
since these grammatical elements in the target language often correspond to long-range dependencies and/or do not have any words corresponding in the source, they may be difficult to model, and the output of an SMT system is often ungrammatical.