How Important Is POS to Dependency Parsing? Joint POS Tagging and Dependency Parsing Neural Networks

Abstract

It is widely accepted that part-of-speech (POS) tagging and dependency parsing are highly related. Most state-of-the-art dependency parsing methods still rely on the results of POS tagging, though the tagger is not perfect yet. Inevitably, dependency parsing model will encounter performance degradation due to the error propagation problems. And it still remains uncertain about how important POS tagging is to dependency parsing. In this work, we propose a method to jointly learn POS tagging and dependency parsing so as to alleviate the error propagation problems. Our proposed method is based on transition system, which is capable to produce dependency tree efficiently and accurately. The results reported in the experiments support our idea that POS tagging is a crucial syntactic component for dependency parsing.