Since then, the approach grew in popularity (Bunescu and Mooney, 2007;Bellare and McCallum, 2007;Wu and Weld, 2007;Mintz et al., 2009;Riedel et al., 2010;Hoffmann et al., 2011;Nguyen and Moschitti, 2011;Sun et al., 2011;Surdeanu et al., 2011a).
most of these approaches make one or more approximations in learning.