K-best combination of syntactic parsers

Abstract

In this paper, we propose a linear model-based general framework to combine k-best parse outputs from multiple parsers. The proposed framework leverages on the strengths of previous system combination and re-ranking techniques in parsing by integrating them into a linear model. As a result, it is able to fully utilize both the logarithm of the probability of each k-best parse tree from each individual parser and any additional useful features. For feature weight tuning, we compare the simulated-annealing algorithm and the perceptron algorithm. Our experiments are carried out on both the Chinese and English Penn Treebank syntactic parsing task by combining two stateof-the-art parsing models, a head-driven lexicalized model and a latent-annotation-based un-lexicalized model. Experimental results show that our F-Scores of 85.45 on Chinese and 92.62 on English outperform the previously best-reported systems by 1.21 and 0.52, respectively. © 2009 ACL and AFNLP.