Hence, when constructing storyline for the main body d in current time period t, we use the model in previous time period t − 1 and predict the storyline distribution p t−1 (s d ).
then we measure current storyline distribution p t (s d ) and predicted distribution p t−1 (s d ) by KL divergence which can be defined as below: the final objective function is to minimize: where α and β are the weights controlling the contributions of the two loss terms.