Three-Phase Opinion Analysis System at NTCIR-6

We developed an opinion analysis system at NTCIR-6. Our system can detect opinion sentences and extract opinion holders by executing three phases: (1) opinion sentence classification by SVM that distinguishes an opinionated sentence from others, (2) opinion-holder candidate extraction using named entity recognition, (3) opinion-holder detection by rules that find the correspondence between the sentence and the holder. Characteristics of the system are the following two points: (a) in phase 1, the end of a sentence expression is added to the feature in SVM vector, and (b) phase 3 is separated into the author detection and the others. As a result of the evaluation, in opinion sentence judgment both precision and the recall ratio improved based on point (a). In opinion holder extraction, precision has improved greatly based on point (b).