9. The method as claimed in claim 4 wherein said step of applying a grouping function g comprises: i. creating groupings of contexts from said initial set of contexts; ii. calculating a conditional entropy for each grouping of contexts; iii. selecting a grouping with a lowest conditional entropy; iv. reducing a size of said set of contexts by replacing elements which comprise the selected grouping with said grouping; and v. repeating steps (i)-(iv) until a size of said set of contexts equals the predetermined number of contexts.
9. The method as claimed in claim 4 wherein said step of applying a grouping function g comprises: i. creating groupings of contexts from said initial set of contexts; ii. calculating a conditional entropy for each grouping of contexts; iii. selecting a grouping with a lowest conditional entropy; iv. reducing a size of said set of contexts by replacing elements which comprise the selected grouping with said grouping; and v. repeating steps (i)-(iv) until a size of said set of contexts equals the predetermined number of contexts. 10. The method as claimed in claim 9 wherein step (c) comprises determining joint, conditional, and unconditional probabilities from a large set of data files having the same file categorization criteria as the determined file categorization.