Based on Equation (10) and (11), it is easy to derive the similarity as follows:   To incorporate more information than the original similarity functions -IBM model 1 probabilities in Equation 6and naïve cosine distance similarity function in Equation 12 .
the original similarity functions are to compare the two context vectors built on full training data directly, as shown in Equation 13 where the parameters i λ (i=1,2,3) can be tuned via minimal error rate training (MERT) (Och, 2003).