Using Left-corner Parsing to Encode Universal Structural Constraints in Grammar Induction
Hiroshi Noji, Yusuke Miyao, Mark S. Johnson · 2016
Center-embedding is difficult to process and is known as a rare syntactic construction across languages.In this paper we describe a method to incorporate this assumption into the grammar induction tasks by restricting the search space of a model to trees with limited centerembedding.The key idea is the tabulation of left-corner parsing, which captures the degree of center-embedding of a parse via its stack depth.We apply the technique to learning of famous generative model, the dependency model with valence (Klein and Manning, 2004).Cross-linguistic experiments on Universal Dependencies show that often our method boosts the performance from the baseline, and competes with the current state-ofthe-art model in a number of languages.