Table 4.

Existing work categorized by sensor modality and the differences between the source and target datasets.

Sensor Modality	χs ≠ χt	P(Xs) ≠ P(Xt)	Ys ≠ Yt	fs(x) ≠ ft(x)
Video	(Duan et al., 2010; Farhadi and Tabrizi, 2008; Liu et al., 2011; Wei and Pal, 2011; Wu et al., 2010)	(Cao et al., 2010; Duan et al., 2010; Xian-ming and Shao-zi, 2009; Yang et al., 2007; Wu et al., 2010)	(Lam et al., 2011; Nater et al., 2011; Yang et al., 2011)	(Cao et al., 2010; Duan et al., 2010; Lam et al., 2011; Liu et al., 2011; Nater et al., 2011; Xian-ming and Shao-zi, 2009; Yang et al., 2007; Yang et al., 2011)
Wearable	(Calatroni et al., 2011; Kurz et al., 2011; Pan, Zheng, Yang and Hu, 2008; Roggen et al., 2011; Yang, 2009; Zhao et al., 2010; Zheng et al., 2008)	(Chieu et al., 2006; Hachiya et al., 2012; Krishnan, 2010; Pan et al., 2006; Pan et al., 2011; Pan et al., 2007; Pan, Shen, Yang and Kwok, 2008; Pan, Zheng, Yang and Hu, 2008; Venkatesan, 2011; Venkatesan et al., 2010; Yang, 2009)	(Blanke and Schiele, 2010; Hu and Yang, 2011; Hu et al., 2010; Zheng et al., 2009)	(Blanke and Schiele, 2010; Hachiya et al., 2012; Hu and Yang, 2011; Hu et al., 2010; Krishnan, 2010; Pan et al., 2006; Pan et al., 2011; Pan et al., 2007; Pan, Shen, Yang and Kwok, 2008; Pan, Zheng, Yang and Hu, 2008; Venkatesan et al., 2010; Yang, 2009; Zheng et al., 2009)
Ambient	(Cook, 2010; Rashidi and Cook, 2010a; Rashidi and Cook, 2010b; Rashidi and Cook, 2011; Roggen et al., 2011; van Kasteren et al., 2008; van Kasteren et al., 2010)	(Cook, 2010; Rashidi and Cook, 2009; Rashidi and Cook, 2010a; Rashidi and Cook, 2010b; Rashidi and Cook, 2011; van Kasteren et al., 2008; van Kasteren et al., 2010)	(Hu and Yang, 2011; Hu et al., 2010; Zheng et al., 2009)	(Cook, 2010; Hu and Yang, 2011; Hu et al., 2010; Rashidi and Cook, 2009; Rashidi and Cook, 2010a; Rashidi and Cook, 2010b; Rashidi and Cook, 2011; van Kasteren et al., 2008; van Kasteren et al., 2010; Zheng et al., 2009)