Reorder and then Parse, Fast and Accurate Discontinuous Constituency Parsing
Kailai Sun, Zuchao Li, Hai Yan Zhao · 2022
Discontinuous constituency parsing is still kept developing for its efficiency and accuracy are far behind its continuous counterparts.Motivated by the observation that a discontinuous constituent tree can be simply transformed into a pseudo-continuous one by artificially reordering words in the sentence, we propose a novel reordering method, thereby construct fast and accurate discontinuous constituency parsing systems working in continuous way.Specifically, we model the relative position changes of words as a list of actions.By parsing and performing this actions, the corresponding pseudocontinuous sequence is derived.Discontinuous parse tree can be further inferred via integrating a high-performance pseudo-continuous constituency parser.Our systems are evaluated on three classical discontinuous constituency treebanks, achieving new state-of-the-art on two treebanks and showing a distinct advantage in speed.