13. The system of claim 12 , wherein the phase transition formula is: f N x , wherein x≧1.
12. A system comprising: at least one processor; memory; and at least one program stored in the memory and executable by the at least one processor, the at least one program comprising instructions to: crawl a plurality of websites to obtain metadata from social media content, extract the metadata from the social media content by identifying at least one sentiment-bearing keyword and a polarity thereof in a sentence from the social media content, determine at least one category corresponding to the at least one sentiment-bearing keyword of the sentence, and determine at least one sentiment corresponding to the at least one category based on the at least one sentiment-bearing keyword, wherein, the instructions further include instructions to extract a list of keywords from a plurality of documents, the instructions to extract the list of keywords including instructions to: (a) extract keywords from each document of the plurality of documents, and (b) for each keyword, calculate a frequency, f, of the keyword in the plurality of documents and a number of documents, N, that include the keyword, use a phase transition formula to calculate a relevancy of the keyword based on the frequency of the keyword in the plurality of documents and the number of documents that include the keyword, and add the keyword to the list of keywords when the relevancy of the keyword exceeds a predetermined threshold.