Choose Your QA Model Wisely: A Systematic Study of Generative and Extractive Readers for Question Answering

Man Luo, Kazuma Hashimoto, Semih Yavuz, Zhiwei Liu, Chitta Baral, Yingbo Zhou


Abstract
While both extractive and generative readers have been successfully applied to the Question Answering (QA) task, little attention has been paid toward the systematic comparison of them. Characterizing the strengths and weaknesses of the two readers is crucial not only for making a more informed reader selection in practice but also for developing a deeper understanding to foster further research on improving readers in a principled manner. Motivated by this goal, we make the first attempt to systematically study the comparison of extractive and generative readers for question answering. To be aligned with the state-of-the-art, we explore nine transformer-based large pre-trained language models (PrLMs) as backbone architectures. Furthermore, we organize our findings under two main categories: (1) keeping the architecture invariant, and (2) varying the underlying PrLMs. Among several interesting findings, it is important to highlight that (1) the generative readers perform better in long context QA, (2) the extractive readers perform better in short context while also showing better out-of-domain generalization, and (3) the encoder of encoder-decoder PrLMs (e.g., T5) turns out to be a strong extractive reader and outperforms the standard choice of encoder-only PrLMs (e.g., RoBERTa). We also study the effect of multi-task learning on the two types of readers varying the underlying PrLMs and perform qualitative and quantitative diagnosis to provide further insights into future directions in modeling better readers.
Anthology ID:
2022.spanlp-1.2
Volume:
Proceedings of the 1st Workshop on Semiparametric Methods in NLP: Decoupling Logic from Knowledge
Month:
May
Year:
2022
Address:
Dublin, Ireland and Online
Venue:
SpaNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
7–22
Language:
URL:
https://aclanthology.org/2022.spanlp-1.2
DOI:
10.18653/v1/2022.spanlp-1.2
Bibkey:
Cite (ACL):
Man Luo, Kazuma Hashimoto, Semih Yavuz, Zhiwei Liu, Chitta Baral, and Yingbo Zhou. 2022. Choose Your QA Model Wisely: A Systematic Study of Generative and Extractive Readers for Question Answering. In Proceedings of the 1st Workshop on Semiparametric Methods in NLP: Decoupling Logic from Knowledge, pages 7–22, Dublin, Ireland and Online. Association for Computational Linguistics.
Cite (Informal):
Choose Your QA Model Wisely: A Systematic Study of Generative and Extractive Readers for Question Answering (Luo et al., SpaNLP 2022)
Copy Citation:
PDF:
https://aclanthology.org/2022.spanlp-1.2.pdf
Video:
 https://aclanthology.org/2022.spanlp-1.2.mp4
Data
MRQANatural QuestionsSQuAD