CASSI: Contextual and Semantic Structure-based Interpolation Augmentation for Low-Resource NER
Tanmay Surana, Thi-Nga Ho, Kyaw Tun, Eng Siong Chng · 2023
While text augmentation methods have been successful in improving performance in the low-resource setting, they suffer from annotation corruption for a token-level task like NER.Moreover, existing methods cannot reliably add context diversity to the dataset, which has been shown to be crucial for low-resource NER.In this work, we propose Contextual and Semantic Structure-based Interpolation (CASSI), a novel augmentation scheme that generates high-quality contextually diverse augmentations while avoiding annotation corruption by structurally combining a pair of semantically similar sentences to generate a new sentence while maintaining semantic correctness and fluency.To accomplish this, we generate candidate augmentations by performing multiple dependency parsing-based exchanges in a pair of semantically similar sentences that are filtered via scoring with a pretrained Masked Language Model and a metric to promote specificity.Experiments show that CASSI consistently outperforms existing methods at multiple low resource levels, in multiple languages, and for noisy and clean text. 1