The search problem given by this model (the search for the segmentation and DA sequence with maximum probability) is solved using the Viterbi process, which implies that the summation is changed by a maximisation.
the final model is: Following the work of other authors (Stolcke et al., 2000;Young, 2000), the terms in Equation 4 are modelled as follows: Pr(u k |u k−1 k−n+1 ) is usually represented by a statistical model of DA sequences (DA language model), generally an n-gram model, and Pr(w s k s k−1 +1 |u k ) is usually modelled by a HMM.