Non-linear decision surfaces can be realized by replacing the inner product of (4) with a kernel function K(x • x i ) : In this paper, we use polynomial kernel functions that have been very effective when applied to other tasks, such as natural language processing (Joachims, 1998;Kudo and Matsumoto, 2001; Kudo and Matsumoto, 2000): 2.2 Sentence Ranking by using Support Vector Machines Important sentence extraction can be regarded as a two-class problem: important or unimportant.
the proportion of important sentences in training data will differ from that in the test data.