Hierarchical Indexing for Retrieval-Augmented Opinion Summarization

Tom Hosking, Hao Tang, Mirella Lapata


Abstract
We propose a method for unsupervised abstractive opinion summarization, that combines the attributability and scalability of extractive approaches with the coherence and fluency of Large Language Models (LLMs). Our method, HIRO, learns an index structure that maps sentences to a path through a semantically organized discrete hierarchy. At inference time, we populate the index and use it to identify and retrieve clusters of sentences containing popular opinions from input reviews. Then, we use a pretrained LLM to generate a readable summary that is grounded in these extracted evidential clusters. The modularity of our approach allows us to evaluate its efficacy at each stage. We show that HIRO learns an encoding space that is more semantically structured than prior work, and generates summaries that are more representative of the opinions in the input reviews. Human evaluation confirms that HIRO generates significantly more coherent, detailed, and accurate summaries.
Anthology ID:
2024.tacl-1.84
Volume:
Transactions of the Association for Computational Linguistics, Volume 12
Month:
Year:
2024
Address:
Cambridge, MA
Venue:
TACL
SIG:
Publisher:
MIT Press
Note:
Pages:
1533–1555
Language:
URL:
https://aclanthology.org/2024.tacl-1.84/
DOI:
10.1162/tacl_a_00703
Bibkey:
Cite (ACL):
Tom Hosking, Hao Tang, and Mirella Lapata. 2024. Hierarchical Indexing for Retrieval-Augmented Opinion Summarization. Transactions of the Association for Computational Linguistics, 12:1533–1555.
Cite (Informal):
Hierarchical Indexing for Retrieval-Augmented Opinion Summarization (Hosking et al., TACL 2024)
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PDF:
https://aclanthology.org/2024.tacl-1.84.pdf