2. The method of claim 1 , wherein extracting the first set of knowledge relevant to the document comprises deriving a set of words or phrases relevant to each document.
2. The method of claim 1 , wherein extracting the first set of knowledge relevant to the document comprises deriving a set of words or phrases relevant to each document. 3. The method of claim 2 , wherein deriving the set of words or phrases further comprises determining a term-frequency inverse-document-frequency (TF.IDF) weight for a word or phrase contained in the document.