Second, even for the perfectly aligned sentences, the oracle action sequence is not the only or the best action sequence that can lead to the gold graph; there could be shorter sequences that are easier to learn.
strictly binding the training objective to the oracle action sequences can lead to suboptimal performance, as evidenced in (Daumé III and Marcu, 2005;Daumé III et al., 2009;Nivre, 2012, 2013;Ballesteros et al., 2016) among others.