19. A method of classifying a document comprising: using a processor (or computer) to perform the steps of: determining one or more metrics for each classifier engine; using said metrics to determine how to use said classifier engines to classify said document; classifying said document accordingly; using said metrics to rank said classifier engines from best to worst, and wherein classifying said document includes: generating, for each classifier engine, a list of probabilities of said document being classified by each classifier engine into each one of a group of possible classes; determining if the best classifier engine has a highest probability that is greater than the highest probability of each other classifier engine by a predetermined amount; if so, using output from said best classifier engine to classify said document; and if not, summing said probabilities for each class, and classifying said document into the class with the largest sum of probabilities.
21. The method of claim 19 wherein said classifier engines are ranked from best to worst based on engine accuracy.