2. The method of claim 1 wherein forming n-grams comprises: receiving at least one class definition comprising a semantic class and at least one text string associated with the semantic class; replacing a text string in a sentence with a tag for a semantic class associated with the text string to form a modified sentence; and forming n-grams from the modified sentence.
2. The method of claim 1 wherein forming n-grams comprises: receiving at least one class definition comprising a semantic class and at least one text string associated with the semantic class; replacing a text string in a sentence with a tag for a semantic class associated with the text string to form a modified sentence; and forming n-grams from the modified sentence. 4. The method of claim 2 wherein generating a rule further comprises generating a separate rule for each specific n-gram found in the modified sentence.