We start the process at e 1 and we need to make sure that the pivot phrases f ∈ F align back to the input language, producing the paraphrase e 2 , and to the target language, producing the sense tag q.
to avoid computing the distribution p(e 2 , q|f ) -which would require a trilingual parallel corpus -we assume that e 2 and q are conditionally independent on f : we assume that pivot phrases generate paraphrases and sense tags independently.