An Efficient Active Learning Pipeline for Legal Text Classification

Sepideh Mamooler, Rémi Lebret, Stephane Massonnet, Karl Aberer


Abstract
Active Learning (AL) is a powerful tool for learning with less labeled data, in particular, for specialized domains, like legal documents, where unlabeled data is abundant, but the annotation requires domain expertise and is thus expensive. Recent works have shown the effectiveness of AL strategies for pre-trained language models. However, most AL strategies require a set of labeled samples to start with, which is expensive to acquire. In addition, pre-trained language models have been shown unstable during fine-tuning with small datasets, and their embeddings are not semantically meaningful. In this work, we propose a pipeline for effectively using active learning with pre-trained language models in the legal domain. To this end, we leverage the available unlabeled data in three phases. First, we continue pre-training the model to adapt it to the downstream task. Second, we use knowledge distillation to guide the model’s embeddings to a semantically meaningful space. Finally, we propose a simple, yet effective, strategy to find the initial set of labeled samples with fewer actions compared to existing methods. Our experiments on Contract-NLI, adapted to the classification task, and LEDGAR benchmarks show that our approach outperforms standard AL strategies, and is more efficient. Furthermore, our pipeline reaches comparable results to the fully-supervised approach with a small performance gap, and dramatically reduced annotation cost. Code and the adapted data will be made available.
Anthology ID:
2022.nllp-1.32
Volume:
Proceedings of the Natural Legal Language Processing Workshop 2022
Month:
December
Year:
2022
Address:
Abu Dhabi, United Arab Emirates (Hybrid)
Editors:
Nikolaos Aletras, Ilias Chalkidis, Leslie Barrett, Cătălina Goanță, Daniel Preoțiuc-Pietro
Venue:
NLLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
345–358
Language:
URL:
https://aclanthology.org/2022.nllp-1.32
DOI:
10.18653/v1/2022.nllp-1.32
Bibkey:
Cite (ACL):
Sepideh Mamooler, Rémi Lebret, Stephane Massonnet, and Karl Aberer. 2022. An Efficient Active Learning Pipeline for Legal Text Classification. In Proceedings of the Natural Legal Language Processing Workshop 2022, pages 345–358, Abu Dhabi, United Arab Emirates (Hybrid). Association for Computational Linguistics.
Cite (Informal):
An Efficient Active Learning Pipeline for Legal Text Classification (Mamooler et al., NLLP 2022)
Copy Citation:
PDF:
https://aclanthology.org/2022.nllp-1.32.pdf