Answering Complex Open-domain Questions Through Iterative Query Generation
Paper · 2019 · Peng Qi, Xiaowen Lin, Leo Mehr et al.
Summary
Standard open-domain QA systems run one retrieval step using the question and then read the results. This fails for multi-hop questions, where a key entity, such as the author of a book, never appears in the question and cannot be found directly. The authors propose GoldEn (Gold Entity) Retriever. It alternates between reading the retrieved context and writing a new natural-language search query, which is then sent to an ordinary off-the-shelf IR engine. This replaces costly, opaque neural retrievers. Each query generator selects a span from the question plus the context gathered so far. It is trained on oracle queries derived from the gold supporting documents, so little extra supervision is needed. A QA module built on BiDAF++ reads the documents collected over two hops. On the fullwiki (open-domain) setting of HotpotQA, the system beats the best previously published model without using pretrained language models such as BERT. It also improves recall of gold evidence, and its readable queries let humans inspect and correct the reasoning process.
Key points
- The evaluation uses the HotpotQA fullwiki setting rather than the few-document setting with distractors. The authors argue the latter can be gamed and is unrealistic.
- With 10 retrieved documents, the generated queries raise recall of the second gold document (d2) from 36.91% to 61.01% compared with question-only retrieval. Recall of the first document (d1) improves only slightly, from 87.85% to 89.91%.
- On non-comparison questions, d2 recall rises from 27.88% to 53.23%. This roughly doubles the number of questions for which the complete gold context is available.
- Oracle substitution experiments show that most errors come from the second-hop generator (G2), which must pick spans from a longer context. Typical failures include choosing entity spans that are too short and picking the wrong entity.
- Restricting queries to span selection and using a fixed number of hops are acknowledged limitations. Code and models are released at github.com/qipeng/golden-retriever.
Institutions
📚 Shelves 5 Computer Science · 9,086 works Artificial Intelligence · 8,889 works Arts and Humanities · 9,296 works Language and Linguistics · 9,206 works Information Systems · 523 works
🧭 Topics 2 Question answering · 242 works Information retrieval & search · 145 works
Cite
Cite as Peng Qi, Xiaowen Lin, Leo Mehr, Zijian Wang and Christopher D. Manning. 2019. Answering Complex Open-domain Questions Through Iterative Query Generation. Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing and the 9th International Joint Conference on Natural Language Processing (EMNLP-IJCNLP).
@inproceedings{qi2019answering,
title = {{Answering Complex Open-domain Questions Through Iterative Query Generation}},
author = {Peng Qi, Xiaowen Lin, Leo Mehr, Zijian Wang and Christopher D. Manning},
booktitle = {Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing and the 9th International Joint Conference on Natural Language Processing (EMNLP-IJCNLP)},
year = {2019},
doi = {10.18653/v1/d19-1261},
url = {https://doi.org/10.18653/v1/d19-1261}
}References
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