After training, one obtains the optimized W and then easily infers word alignment for a test sentence pair x, y via the MAP strategy as defined in equation 3 by setting Note that if word embeddings and hidden units learned by NMT models capture enough information for word alignment, the above method can obtain excellent word alignment.
because the dataset for supervision in training definitely include some data intrinsic word alignment information, it is unclear how much word alignment is only from NMT models.