In this paper, we are interested in developing a new topic model which can take into account the structural topic dependency by following the higher level document subject structure, but we hope to retain the general flavour of topic models, where components (e.g., sentences) can be a mixture of topics.
we need to depart from the earlier HMM style models, see, e.g., (Blei and Moreno, 2001;Gruber et al., 2007).