Graph-Based Multilingual Label Propagation for Low-Resource Part-of-Speech Tagging
This addresses the lack of labeled data for POS tagging in low-resource languages, which is an incremental improvement over existing transfer methods.
The paper tackles the problem of part-of-speech tagging for low-resource languages by proposing a graph-based label propagation method to transfer labels from multiple high-resource languages, achieving a new state-of-the-art in unsupervised POS tagging.
Part-of-Speech (POS) tagging is an important component of the NLP pipeline, but many low-resource languages lack labeled data for training. An established method for training a POS tagger in such a scenario is to create a labeled training set by transferring from high-resource languages. In this paper, we propose a novel method for transferring labels from multiple high-resource source to low-resource target languages. We formalize POS tag projection as graph-based label propagation. Given translations of a sentence in multiple languages, we create a graph with words as nodes and alignment links as edges by aligning words for all language pairs. We then propagate node labels from source to target using a Graph Neural Network augmented with transformer layers. We show that our propagation creates training sets that allow us to train POS taggers for a diverse set of languages. When combined with enhanced contextualized embeddings, our method achieves a new state-of-the-art for unsupervised POS tagging of low-resource languages.