“…We classify the existing methods of detecting OOD intents into two main categories, supervised and unsupervised OOD detection. Supervised OOD detection (Scheirer et al, 2013;Fei and Liu, 2016;Kim and Kim, 2018;Larson et al, 2019;He et al, 2020c;Zheng et al, 2020) represents that there are extensive labeled OOD samples in the training data while unsupervised OOD detection (Breunig et al, 2000;Bendale and Boult, 2016;Hendrycks and Gimpel, 2017;Shu et al, 2017;Lee et al, 2018;Ren et al, 2019;Lin and Xu, 2019) means few or no labeled OOD samples except for labeled in-domain data. Unsupervised OOD detection makes it more complicated to identify unknown intents due to unseen and diverse semantic expressions.…”