Conversational search is one of the ultimate goals of information retrieval.
Recent research approaches conversational search by simplified settings of
response ranking and conversational question answering, where an answer is
either selected from a given candidate set or extracted from a given passage.
These simplifications neglect the fundamental role of retrieval in
conversational search. To address this limitation, we introduce an
open-retrieval conversational question answering (ORConvQA) setting, where we
learn to retrieve evidence from a large collection before extracting answers,
as a further step towards building functional conversational search systems. We
create a dataset, OR-QuAC, to facilitate research on ORConvQA. We build an
end-to-end system for ORConvQA, featuring a retriever, a reranker, and a reader
that are all based on Transformers. Our extensive experiments on OR-QuAC
demonstrate that a learnable retriever is crucial for ORConvQA. We further show
that our system can make a substantial improvement when we enable history
modeling in all system components. Moreover, we show that the reranker
component contributes to the model performance by providing a regularization
effect. Finally, further in-depth analyses are performed to provide new
insights into ORConvQA.

本文提出一种名为 ORConvQA 的交互式检索问答方法，通过基于 Transformers 的检索器、排序器和阅读器，实现在大规模语料库中检索答案并提取答案以构建功能性的交互式检索系统，并创建了 OR-QuAC 数据集以促进 ORConvQA 的研究。实验证明可学习的检索器对 ORConvQA 至关重要，在所有系统组件中启用历史建模可以显著提高系统性能，排序器组件提供了正则化效果并有助于模型性能的提升。