1. A method of identifying potential novel word usage in a document, comprising: determining a part-of-speech assignment for each word in the document using a first part-of-speech tagger; determining a part-of-speech assignment for each word in the document using a second part-of-speech tagger different from the first part-of-speech tagger; comparing the part-of-speech assignment of the first and second part-of-speech taggers; and generating a differential word set having words with different part-of-speech assignment by the first and second part-of-speech taggers, the words in the differential word set being candidates of words of novel usage.