sentence1: sentiment classification is a hot research topic in natural language processing field , and has many applications in both academic and industrial areas ( cite-p-17-1-16 , cite-p-17-1-12 , cite-p-17-3-4 , cite-p-17-3-3 ) .
sentence2: sentiment classification is a special task of text categorization that aims to classify documents according to their opinion of , or sentiment toward a given subject ( e.g. , if an opinion is supported or not ) ( cite-p-11-1-2 ) .