KBQA includes simple questions that retrieve answers from single-hop triples ("what is Donald Trump's nationality") (Berant et al., 2013;Yih et al., 2014), multi-hop questions that infer answers over triple chains of at least 2 hops under specific constraints ("who is the president of the European Union 2012") (Yih et al., 2016;, and complex questions that involve set operations ("how many rivers flow through India and China") .
complex question answering (CQA) (Saha et al., 2018) is a sophisticated KBQA task in which a sequence of discrete actions-e.g., set intersection and union, counting, comparison-needs to be executed, and is the subject of this paper.