“…Although the number of observations may be of the order of 10 (Yamato et al, 1992;Hertz et al, 2006;Wasikowski and Chen, 2010), it is more common for hundreds of observations to be made (Rigoll et al, 1997;Liang and Ouhyoung, 1998;Wei et al, 2011;Jost et al, 2015;Mapari and Kharat, 2015) and sometimes even thousands (Babu, 2016;Sun et al, 2015;Zheng et al, 2015;Zhou et al, 2015). The number depends strongly on the application, which may vary from object or face recognition in images or clips (Serre et al, 2005;Huang et al, 2007;Toshev et al, 2009) to gestures or patterns coming from complex multimodal inputs (Jaimes and Sebe, 2007;Escalera et al, 2016). Some of the major challenges regarding recognition lie in representation, learning, and detection (Lee et al, 2016).…”