Can You Unpack That? Learning to Rewrite Questions-in-Context
Summary
In conversational question answering, later questions depend on earlier turns. Pronouns, dropped entities, and phrases like "anything else" only make sense given the dialogue history. The authors define a task called question-in-context rewriting: converting such a dependent question into a standalone version with the same answer. To support it, they built CANARD by crowdsourcing rewrites of QuAC questions on Mechanical Turk. Workers were told to make minimal edits, live JavaScript checks warned about leftover pronouns or vague words, and the authors manually reviewed flagged submissions. They compare three baselines using BLEU against human rewrites: an unchanged copy, a rule replacing the first pronoun with the article title, and an attention-based Seq2Seq LSTM with a copy mechanism. The neural model beats the simple baselines but stays roughly 9 BLEU below human agreement. Its typical errors are overly short rewrites, confusion between related entities, and dropped list items. The resource matters because it turns conversational QA into ordinary reading comprehension and supports future systems that ask users for clarification.
Key points
- CANARD contains 40,527 rewritten questions derived from QuAC: 31,538 for training, 3,418 for development (from QuAC train), and 5,571 for testing (QuAC's full dev set).
- Quality control flagged about 15% of the data for review, and 19.9% of submissions were rejected. In a manual check of 50 rewrites, every desired property appeared in at least 90% of cases.
- BLEU scores (dev/test):
- Copy: 33.84/36.25
- Pronoun Sub: 47.72/47.44
- Seq2Seq (OpenNMT, GloVE embeddings): 51.37/49.67
- Human: 59.92, measured on a small validation subset
- Pronouns appear in 53.9% of QuAC questions and in 75.0% of conversation histories. Mixed-category pronouns in the history affect 27.8% of the data, and only about a third of rewrites are reachable by pronoun replacement alone.
Cited by
- Open-Domain Question Answering Goes Conversational via Question Rewriting
- Bridging Background Knowledge Gaps in Translation with Automatic Explicitation
Cite
@inproceedings{elgohary2019can,
title = {{Can You Unpack That? Learning to Rewrite Questions-in-Context}},
author = {Elgohary, Ahmed and Peskov, Denis and Boyd-Graber, Jordan},
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/d19-1605},
url = {https://doi.org/10.18653/v1/d19-1605}
}References
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