Improving Syntactic Parsing of Chinese with Empty Element Recovery

This paper puts forward and explores the problem of empty element (EE) recovery in Chinese from the syntactic parsing perspective, which has been largely ignored in the literature. First, we demonstrate why EEs play a critical role in syntactic parsing of Chinese and how EEs can better benefit syntactic parsing of Chinese via re-categorization from the syntactic perspective. Then, we propose two ways to automatically recover EEs: a joint constituent parsing approach and a chunk-based dependency parsing approach. Evaluation on the Chinese TreeBank (CTB) 5.1 corpus shows that integrating EE recovery into the Charniak parser achieves a significant performance improvement of 1.29 in F1-measure. To the best of our knowledge, this is the first close examination of EEs in syntactic parsing of Chinese, which deserves more attention in the future with regard to its specific importance.