Many recent state-of-the-art models for constituency parsing are transition based, decomposing production of each parse tree into a sequence of action decisions Cross and Huang, 2016;Liu and Zhang, 2017;, building on a long line of work in transition-based parsing (Nivre, 2003;Yamada and Matsumoto, 2003;Henderson, 2004;Zhang and Clark, 2011;Chen and Manning, 2014;Andor et al., 2016;Kiperwasser and Goldberg, 2016).
models of this type, which decompose structure prediction into sequential decisions, can be prone to two issues (Ranzato et al., 2016;Wiseman and Rush, 2016).