1. A method comprising: updating, by a predictive coding system, a set of training documents based on a selected portion of a training document of the set to obtain an updated set of training documents; searching, by the predictive coding system, content within other training documents in the updated set using a machine learning engine based on the selected portion and variations of the selected portion; determining a probability measure for the content; and classifying, by the predictive coding system, a second training document containing the content based on the probability measure.