We take an LSTM structure similar to the baseline BiLSTM for modelling state transition, using a recurrent cell c t i for each w i and a cell c t g for g. As shown in Figure 1, the value of each h t i is computed based on the values of i+1 and g t−1 , together with their corresponding cell values: where ξ t i is the concatenation of hidden vectors of a context window, and gates that control information flow from ξ t i and x i to c t i .
i t i controls information from the input x i ; l t i , r t i , f t i and s t i control information from the left context cell c t−1 i−1 , the right context cell c t−1 i+1 , c t−1 i and the sentence context cell c t−1 g , respectively.