English Opinion Analysis for NTCIR7 at POSTECH

We describe an opinion analysis system developed for Multilingual Opinion Analysis Task at NTCIR7. Given a topic and relevant newspaper articles, our system determines whether a sentence in the articles carries an opinion, if so, then extract the polarity and holder of the opinion. Our system uses subjectivity lexicons to score the sentiment weight of a word, in addition with a weight that reflects the discriminating power of the word. We borrow some techniques from Information Retrieval because discovering the importance and discriminating power of a word in a collection of documents is a commonly dealt issue in information retrieval tasks. We also use our own set of heuristics that are more specific to the task. Our system achieves high performance overall, with exceptional performances on polarity judgment of sentences.