In contrast, qualitative analysis of the unparameterized transition model show that its alignments learn desirable correspondences (see Figure 2).
the forward variable α i (j) representing p(y 1:j , a j = i|x 1:i ) is recursively as αi(j) = p(yj|i, x1:i, y1:j−1) × i k=1 α k (j − 1)p(aj = i|k, x 1:k , y1:j−1).