“…Traditional dialogue systems [17,33] usually consist of three components: natural language understanding (NLU) [28,30,58,59], dialogue management (DM) [6,7,18], and natural language generation (NLG) [50,63,65,66] modules. Empirically, NLU plays the most important role in task-oriented dialogue systems, including tasks such as intent detection [12,13,29,57], slot filling [61], and semantic parsing [19? , 20].…”