Corpus-based approaches (contd)
Use constraints (or conventions) on connectives to identify opinion words (Hazivassiloglou and McKeown, ACL-97; Kanayama and Nasukawa, EMNLP-06; Ding and Liu, 2007). E.g.,
Conjunction: conjoined adjectives usually have the same orientation (Hazivassiloglou and McKeown, ACL-97).
E.g., “This car is beautiful and spacious.” (conjunction)
AND, OR, BUT, EITHER-OR, and NEITHER-NOR have similar constraints.
log-linear model: determine if two conjoined adjectives are of the same or different orientations.
Clustering: produce two sets of words: positive and negative
Corpus: 21 million word 1987 Wall Street Journal corpus.