explore more advanced features for aspect-based sentiment classification task and add them

[pfliu-nlp]

• [ ] read the paper, design more advanced features, for example
  • the number of but (however)
  • sentiment consistency of aspects
  • sentiment consistency of samples
  • training set dependent features?

[pfliu-nlp]

• [ ] features that might rely on a sentiment lexicon dictionary:
  • A list of English positive and negative opinion words or sentiment words
  • A list of non-standard English compariative words and phrases for sentiment analysis
• [ ] the number of negation words?