Exogenous and Endogenous Data Augmentation for Low-Resource Complex Named Entity Recognition

Low-resource Complex Named Entity Recognition aims to detect entities with the form of any linguistic constituent under scenarios with limited manually annotated data. Existing studies augment the text through the substitution of same type entities or language modeling, but suffer from the lower quality and the limited entity context patterns within low-resource corpora. In this paper, we propose a novel data augmentation method E(2)DA from both exogenous and endogenous perspectives. As for exogenous augmentation, we treat the limited manually annotated data as anchors, and leverage the powerful instruction-following capabilities of Large Language Models (LLMs) to expand the anchors by generating data that are highly dissimilar from the original anchor texts in terms of entity mentions and contexts. As regards the endogenous augmentation, we explore diverse semantic directions in the implicit feature space of the original and expanded anchors for effective data augmentation. Our complementary augmentation method from two perspectives not only continuously expands the global text-level space, but also fully explores the local semantic space for more diverse data augmentation. Extensive experiments on 10 diverse datasets across various low-resource settings demonstrate that the proposed method excels significantly over prior state-of-the-art data augmentation methods.