The forward pass for each document, n, starts from τ = 1 and computes: r − n,τ −1,ι e E ln T ι,j + ll n,τ (j), where r − n,0,ι = 1 where ι ='O' and 0 otherwise.
the VB algorithm is described in Algorithm 1, making use of update equations for the variational factors given below.