We study open-domain question answering (ODQA) with structured, unstructured and semi-structured knowledge sources, including text, tables, lists, and knowledge bases. Our approach homogenizes all sources by reducing them to text, and applies recent, powerful retriever-reader models which have so far been limited to text sources only. We show that knowledge-base QA can be greatly improved when reformulated in this way. Contrary to previous work, we find that combining sources always helps, even for datasets which target a single source by construction. As a result, our unified model produces state-of-the-art results on 3 popular ODQA benchmarks.

该研究致力于利用结构化、非结构化和半结构化知识来源（如文本、表格、列表和知识库）进行开放域问题回答，并提出了统一的方法，将它们转化为文本并采用检索-阅读器模型，从而大大提高了在知识库问题回答任务上的表现，并将异构知识来源融合成一个简单且有效的统一知识模型，并在两个流行的问答基准测试中（自然问题和网络问题）继续提高最新的图形方法等级，分别为3.5和2.6点。

UniK-QA: 面向开放域问答的结构化和非结构化知识统一表示