15. The apparatus of claim 10 , further comprising: a pre-processing unit, configured to process the word in the mass categorized data in advance; and/or a quality determining unit, configured to determine the quality of the word according to the importance weight of the word.
16. The apparatus of claim 15 , wherein the quality determining unit comprises: a threshold configuring module, configured to configure an importance threshold and a constantly-used threshold for each level, wherein the level is obtained according to the DFs of the words in all the categorized data; a level quality determining module, configured to determine the quality of the word in the level according to a relationship between the two thresholds and the importance weight of the word in the corresponding level; a normalization processing module, configured to normalize the importance weight of the word in each level to obtain an integrated importance weight of the word; an integrated classifying module, configured to perform an integrated quality classification to words of the same quality in different levels based on the integrated importance weight of the word; or, the quality determining unit comprises: a normalization module, configured to normalize the importance weight of the word in each level to obtain an integrated importance weight of the word, wherein the levels are divided according to the DFs of the words in all the categorized data; a threshold configuring module, configured to configure an important threshold and a constantly-used threshold; and an integrated classifying module, configured to perform an integrated quality classification to all words based on a relationship between the two thresholds and the integrated importance weight of the word.