16. A computer-readable medium encoded with computer-executable instructions for controlling a computing device to determine an opinion expressed in a sentence, by a method comprising: calculating a probability that the sentence contains a sequence of parts of speech that indicate an expression of the opinion; determining a probability that the sentence contains an opinion word that expresses the opinion given the sequence; determining a probability that a word of the sentence expresses the opinion given the opinion word; and calculating an overall probability that the sentence expresses the opinion by combining the probabilities.
16. A computer-readable medium encoded with computer-executable instructions for controlling a computing device to determine an opinion expressed in a sentence, by a method comprising: calculating a probability that the sentence contains a sequence of parts of speech that indicate an expression of the opinion; determining a probability that the sentence contains an opinion word that expresses the opinion given the sequence; determining a probability that a word of the sentence expresses the opinion given the opinion word; and calculating an overall probability that the sentence expresses the opinion by combining the probabilities. 19. The computer-readable medium of claim 16 including providing an opinion data store that specifies sequences of parts of speech that may express an opinion, a probability that each sequence contains a word that may express an opinion, and a probability that each word expresses an opinion.