The model implemented here is of second order: at any decision point t we condition the probability distribution over labels on the previous two predictions y t−1 and y t−2 in addition to the given (static) word context from both the source and target sentences.
the probability of a predicted inflection sequence is defined as follows: where x t denotes the given context at position t and I t is the set of inflections corresponding to S t , from which the model should choose y t .