Retrieval-Augmented Few-shot Text Classification

Guoxin Yu, Lemao Liu, Haiyun Jiang, Shuming Shi, Xiang Ao


Abstract
Retrieval-augmented methods are successful in the standard scenario where the retrieval space is sufficient; whereas in the few-shot scenario with limited retrieval space, this paper shows it is non-trivial to put them into practice. First, it is impossible to retrieve semantically similar examples by using an off-the-shelf metric and it is crucial to learn a task-specific retrieval metric; Second, our preliminary experiments demonstrate that it is difficult to optimize a plausible metric by minimizing the standard cross-entropy loss. The in-depth analyses quantitatively show minimizing cross-entropy loss suffers from the weak supervision signals and the severe gradient vanishing issue during the optimization. To address these issues, we introduce two novel training objectives, namely EM-L and R-L, which provide more task-specific guidance to the retrieval metric by the EM algorithm and a ranking-based loss, respectively. Extensive experiments on 10 datasets prove the superiority of the proposed retrieval augmented methods on the performance.
Anthology ID:
2023.findings-emnlp.447
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2023
Month:
December
Year:
2023
Address:
Singapore
Editors:
Houda Bouamor, Juan Pino, Kalika Bali
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
6721–6735
Language:
URL:
https://aclanthology.org/2023.findings-emnlp.447
DOI:
10.18653/v1/2023.findings-emnlp.447
Bibkey:
Cite (ACL):
Guoxin Yu, Lemao Liu, Haiyun Jiang, Shuming Shi, and Xiang Ao. 2023. Retrieval-Augmented Few-shot Text Classification. In Findings of the Association for Computational Linguistics: EMNLP 2023, pages 6721–6735, Singapore. Association for Computational Linguistics.
Cite (Informal):
Retrieval-Augmented Few-shot Text Classification (Yu et al., Findings 2023)
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PDF:
https://aclanthology.org/2023.findings-emnlp.447.pdf