Current summarization systems often represent concepts indirectly via textual features that give high scores to the textual units that contain important information and should be used in the summary and low scores to those textual units which are not likely to contain information worth to be included in the final output.
many summarization approaches use as conceptual units lexical features like tf*idf weighing of words in the input text(s), words used in the titles and section headings of the source documents (Luhn, 1959;H.P.Edmundson, 1968), or certain cue phrases like significant, important and in conclusion (Kupiec et al., 1995;Teufel and Moens, 1997).