The diversity of chain S is the sum of the diversities of its successive scenes: The diversity d(s i , s i+1 ) of two scenes s i and s i+1 is estimated taking into account two factors: (a) do they have any characters in common, and (b) does the sentiment change from one scene to the next: respectively denote character and sentiment similarity between scenes.
d char (s i , s i+1 ) is the relative character overlap between scenes s i and s i+1 : d char will be 0 if two scenes share the same characters and 1 if no characters are shared.