Sentiment Analysis aims to determine the overall sentiment orientation of a given input text. One motivation for research in this area is the need for consumer related industries to extract public opinion from online portals such as blogs, discussion boards, and reviews. Estimating sentiment orientation in text involves extraction of sentiment rich phrases and the aggregation of their sentiment orientation. Identifying sentiment rich phrases is typically achieved by using manually selected

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... of-speech (PoS) patterns. In this paper we present an algorithm for automated discovery of PoS patterns from sentiment rich background data. Here PoS patterns are selected by applying standard feature selection heuristics: Information Gain (IG), Chi-Squared (CHI) score, and Document Frequency (DF). Experimental results from two real-world datasets suggests that classification accuracy is significantly better with DF selected patterns than with IG or the CHI score. Importantly, we also found DF selected patterns to result in comparative classifier accuracy to that of manually selected patterns. Proceedings of AI-2007, 27th SGAI Int Conf on innovative techniques and applications of AI. Springer