A recent comparison of summaries from human experts versus extractive summarizers on forty-six topics from the TAC 2010 summarization challenge used automatic caseframe analysis, and found essentially these same properties in the human summaries, and not in the extractive ones (Cheung and Penn, 2013).
recall from section 4.3, every pair of segments in an SCU has an edge ≥ t edge ; therefore an SCU with r + 1 contributors can be decomposed into SCUs with r contributors.