For each pair of sentences (u, v) : u < v in D , we generate two training entries.
the first, signifying that u appears before v in D , assigns the label true to a trigger list consisting of standard feature functions derived from u, and complementary feature functions derived from v. the second, reinforcing this observation, assigns the label false to a trigger list consisting of complementary feature functions from u, and standard feature functions from v. the labeled training set (feature:label pairs) for the comparator can be expressed as follows: if there are d sentences in D , we obtain a total of d(d − 1) labeled examples to train the comparator.