(Axelrod et al., 2011) presents a technique of using the difference in cross-entropy of the supplementary sentence pairs on 'in-domain' and 'out-of-domain' datasets for ranking and selection by thresholding.
in a similar approach to the lexical table merging, every entry in the new (incremental) batch phrase-table, is compared against the older (baseline) phrase-table and the shared phrase pairs are updated by the formulae in (2): c bl (e)+c inc (e) + φ inc ( f |e) × c inc (e) c bl (e)+c inc (e) 2where φ bl , c bl , φ inc and c inc indicate the baseline phrase translation probability, baseline phrase count, incremental phrase translation probability and incremental phrase count, respectively.