CONQRR: Conversational Query Rewriting for Retrieval with Reinforcement Learning

For open-domain conversational question answering (CQA), it is important to retrieve the most relevant passages to answer a question, but this is challenging compared with standard passage retrieval because it requires understanding the full dialogue context rather than a single query. Moreover, it can be expensive to re-train well-established retrievers such as search engines that are originally developed for non-conversational queries. To facilitate their use, we develop a query rewriting model CONQRR that rewrites a conversational question in context into a standalone question. It is trained with a novel reward function to directly optimize towards retrieval and can be adapted to any fixed blackbox retriever using reinforcement learning. We show that CONQRR achieves state-of-the-art results on a recent open-domain CQA dataset, a combination of conversations from three different sources. We also conduct extensive experiments to show the effectiveness of CONQRR for any given fixed retriever.