To further accelerate the distillation process of the domaininvariant features, we also introduce an adversarial loss of the domain classifier for the feature extractor.
we calculate the loss in Equation 10 with the flipped domain labels inspired by the work (Shu et al., 2018): We model the AD task as a sequence labeling problem, and each word in the sentence is marked as a tag in {B, I, O}, which means the word is at the beginning (B) or the inside (I) of an aspect term or other word (O).