9. The method of claim 1 , further comprising: constructing a classifier based on a first subset of the keywords, comprising: for each of the first subset of keywords, for each of the labels annotating the keyword, determining a correctness of the label; calculating a first index-wise product between a word count vector of the keyword document corresponding to the keyword and a word count vector of the label document corresponding to the label; and forming a pair of the correctness and the first index-wise product; and training the classifier using the pairs of the correctness and the first index-wise product; and for each of a second subset of the keywords, for each of the labels annotating the keyword, calculating a second index-wise product between a word count vector of the keyword document corresponding to the keyword and a word count vector of the label document corresponding to the label; and predicting whether the label is correct using the classifier with the second index-wise product as an input to the classifier.
9. The method of claim 1 , further comprising: constructing a classifier based on a first subset of the keywords, comprising: for each of the first subset of keywords, for each of the labels annotating the keyword, determining a correctness of the label; calculating a first index-wise product between a word count vector of the keyword document corresponding to the keyword and a word count vector of the label document corresponding to the label; and forming a pair of the correctness and the first index-wise product; and training the classifier using the pairs of the correctness and the first index-wise product; and for each of a second subset of the keywords, for each of the labels annotating the keyword, calculating a second index-wise product between a word count vector of the keyword document corresponding to the keyword and a word count vector of the label document corresponding to the label; and predicting whether the label is correct using the classifier with the second index-wise product as an input to the classifier. 10. The method of claim 9 , further comprising: for each of the second subset of the keywords, calculating a confidence score based on the prediction made by the classifier for the keyword; sorting the second subset of the keywords based on their confidence scores; and for each of the second subset of the keywords, accepting the labels annotating the keyword when the confidence score of the keyword is above a first threshold; rejecting the labels annotating the keyword when the confidence score of the keyword is below a second threshold; manually reviewing the labels annotating the keyword when the confidence score of the keyword is between the first threshold and the second threshold.