If the maximum number of sentences/comments chosen were k, we brought both hs and ht to the same approximate scale as hm by dividing hs by k(k − 1)/2 and ht by k − 1. from dependency parse tree) along with computing similarity in semantic spaces (using WordNet) clearly produces an improvement in the summarization quality (+1.4 improvement in ROUGE-1 F-score).
this is an interesting extension of their previous submodular framework and while the new formulation permits more complex functions, the resulting function is still submodular and hence can be combined with the dispersion measures proposed in this paper.