(2008) to use log-BLEU, which is scored by the hypothesis length and a linear function of n-gram matches as: In this definition, is a reference translation, is the length of hypothesis , is an ngram presented in , is the number of times that occurs in , and is an indicator function which equals to 1 when occurs in and 0 otherwise.
mBR-IHmm Word-Comb has ability to generate new hypotheses, while Hypergraph mmmBR only chooses translations from original search spaces.