Another line of work is based on a purely unsupervised learning method, denoising autoencoders, where the hidden layers in multi-layer neural networks are believed to be robust against domain shift (Glorot et al., 2011;Chen et al., 2012;Zhou et al., 2016).
all these methods are still based on traditional discrete representations, and the shared representations are learned separately from the final classifier and therefore not directly related to sentiment classification.