“…Moreover, the past value of the newly introduced hidden state, v s,kÀ1 , can be seen as an arrival cost-value, carrying all the past information of the drift to the current time instance, so the drifting state can be estimated. Thus, the analytical expressions for the hidden state value of the slow rate target node x s,k vary depending on the availability of laboratory data, that is, if 4 ¼ 0 or 4 ¼ 1: Thus, using first-order optimality conditions on Equation (10) results in a set of simultaneous linear equations, where estimates of quality variable (x s ) at k th instance is obtained through the following analytical solutions given in Equations ( 11) and (12). In Equations ( 11) and ( 12), N Ch refers to the number of child nodes of the target variable node (x s ) and σ 2 ch x s ð Þ refers to the variance between the target node x s ð Þ and its child node.…”