15. The computer-implemented information processing of claim 13 , wherein the sentence is a first sentence among a plurality of sentences, and the method further comprises the steps of: extracting the sentences from the document; generating a list of sentence scores for the sentences; identifying high sentence scores as the sentence scores in the list which exceed the threshold; identifying low sentence scores as the sentence scores in the list which lie below the threshold; extracting first sentences corresponding to the high sentence scores; extracting second sentences corresponding to the low scores; and displaying at least one of the first sentences or the second sentences on a display.
16. The computer-implemented information processing of claim 15 , wherein the displaying step includes: determining a degree of commonness of the document; displaying first sentences on a display when the degree of commonness lies below a second threshold; and displaying second sentences on the display when the degree of commonness exceeds the second threshold.