We therefore hypothesize that the choice of vocabulary is not only a matter of topic but also of perspective, while word recurrence has mainly to do with the topical composition of the text.
tracing word frequencies is not going to be effective for perspective classification beyond noting the mere presence/absence of words, differently from the findings in text categorization, where frequency-based features usually do better than boolean features for sufficiently large vocabulary sizes (McCallum and Nigam, 1998).