Furthermore, sentence-level scoring (i) is compatible with most translation systems, which work on a sentence-bysentence basis, (ii) could be beneficial to modern MT tuning mechanisms such as PRO (Hopkins and May, 2011) and MIRA (Watanabe et al., 2007;Chiang et al., 2008), which also work at the sentence-level, and (iii) could be used for reranking n-best lists of translation hypotheses.
dR-LEX includes the lexical items to account for lexical matching; moreover, it separates the structure (the skeleton) of the tree from its labels, i.e.