3. The method of claim 1 , wherein the single-aspect evaluation comprises one or more of: Inverse Document Frequency (IDF), Average IDF (AVAIDF), chi-square, Information Gain (IG), Mutual Information (MI), Expect Cross Entropy (ECE), Entropy (ENT) and selective preference (SELPRE).
3. The method of claim 1 , wherein the single-aspect evaluation comprises one or more of: Inverse Document Frequency (IDF), Average IDF (AVAIDF), chi-square, Information Gain (IG), Mutual Information (MI), Expect Cross Entropy (ECE), Entropy (ENT) and selective preference (SELPRE). 4. The method of claim 3 , wherein the single-aspect evaluation is the IG, the evaluating the word comprises: classifying all candidate words into ranges according to DFs of the candidate words; and calculating the IG of the word based on the categorized data corresponding to a range of the word.