learning a weight vector w such that w(x i − x j ) > δ, when essay i has a higher gold score than essay j, where δ is the one-sided margin 3 (Joachims, 2002;Chapelle and Keerthi, 2010).
instead of directly learning to predict the gold score of an essay vector, the model learns a weight vector w that minimizes the misclassification of difference vectors.