Fine-grained opinion mining aims to detect structured user opinions in text, which has drawn much attention in the natural language processing (NLP) community <cite>(Kim and Hovy, 2006</cite>; Breck et al., 2007; Ruppenhofer et al., 2008; Wilson et al., 2009; Qiu et al., 2011; Cardie, 2013, 2014; Liu et al., 2015; Wiegand et al., 2016) .