In our experiments, we employed equation 3to infer for each para-phrase pair translation model probabilities p φ (syn|trg) and p φ (trg|syn) from relative frequencies of phrases in bilingual tables.
to Bannard and Callison-Burch (2005), we applied the same inference step to infer also lexical translation probabilities p w (syn|trg) and p w (trg|syn) as defined in Koehn et al.