8. A method for context-based sentiment analysis, comprising: obtaining a piece of comment data that is initially determined to be associated with a positive sentiment, a negative sentiment, a neutral sentiment, or a mixed sentiment, the piece of comment data being included in a comment; determining a context sentiment type of an associated context related to the piece of comment data, the associated context being distinct from the comment and including text that is created at a different time than the piece of comment data, and the determination being made with reference to at least a set of context features, wherein the context sentiment type indicates that the associated context is positive sentiment-entailing, negative sentiment-entailing, or neutral, wherein the determining of the context sentiment type of the associated context related to the piece of comment data comprises: determining whether the context sentiment type of the associated context related to the piece of comment data is positive sentiment-entailing; and in response to a determination that the context sentiment type is determined to be positive sentiment-entailing, classifying the piece of comment data includes using a positive model-based comment classifier, comprising to: performing an initial classification; and in response to a determination that the initial classification is positive and a positive context model-based comment classification of the positive model-based comment classifier is not-positive, determining a final classification to be neutral; and classifying the piece of comment data, the classification being based at least in part on the piece of comment data and the context sentiment type.
11. The method of claim 8 , wherein the set of context features includes a keyword or key phrase.