Recent work on open-domain question answering largely follow this retrieve-and-read approach, and focus on improving the information retrieval component with question answering performance in consideration (Nishida et al., 2018;Kratzwald and Feuerriegel, 2018;Nogueira et al., 2019).
these one-step retrieve-and-read approaches are fundamentally ill-equipped to address questions that require multi-hop reasoning, especially when necessary evidence is not readily retrievable with the question.