Sentiment analysis is a form of text categorization that works on opinions instead of topics. Often, texts are categorized according to the subject they discuss. For example, sentiment analysis attempts to categorize texts according to the opinions or emotions of the writers, whether the text is about cars or pets. Often, these are cast in binary terms: good or bad, like or dislike, positive or negative, and so on. Does this person love Toyotas or hate them? Are Pugs the best or German Shepherds? Would they go back to this restaurant? Questions like these have proven to be an important area of research, simply because so many companies want to know what people say about their goods and services online. This provides a way for companies' marketing departments to monitor people's opinions about their products or services as they talk on Twitter and other online public forums. They can reach out to unhappy customers to provide better, more proactive customer...