15. The apparatus according to claim 14 , wherein the text features of the block comprise at least one of: number of the block's occurrences in the plurality of historical versions; size of the block; positions of the block in pages of the plurality of historical versions; number of differences in the block; distribution style of differences in the block; and positions of differences in the block.
15. The apparatus according to claim 14 , wherein the text features of the block comprise at least one of: number of the block's occurrences in the plurality of historical versions; size of the block; positions of the block in pages of the plurality of historical versions; number of differences in the block; distribution style of differences in the block; and positions of differences in the block. 16. The apparatus according to claim 15 , wherein the probability evaluating module comprises: a first calculating module configured to, with respect to at least one respect of the text features, calculate a score component; and a second calculating module configured to calculate the probability score of the block on the basis of the score component.