We first discuss the results for the TripAdvisor-Gold dataset shown in We use LIBLINEAR (Fan et al., 2008) with L2regulization, parameter optimized over the 80% training data (3 folds for training, 1 fold for testing).
another question one might have is whether the performance gain of PCFG features are mostly from local sequences of POS tags, indirectly encoded in the production rules.