First, existing approaches to MT quality estimation rely on lexical and syntactical features defined over parallel sentence pairs, which includes source sentences, MT outputs and references, and translation models (Blatz et al., 2004;Ueffing and Ney, 2007;Specia et al., 2009a;Xiong et al., 2010;Soricut and Echihabi, 2010a;Bach et al., 2011).
when the MT quality estimation model is trained, it can not be adapted to provide accurate estimates on the outputs of document-specific MT models.