1. A computer-implemented method, comprising: (a) receiving a first set of elements, each element in the first set being assigned to one of a plurality of categories and having one of a plurality of word-stem profiles associated therewith; (b) receiving a second set of elements, each element in the second set having one of the word-stem profiles associated therewith; and (c) using a processor to calculate, based on the word-stem profiles associated with and the categories assigned to elements in the first set and the word-stem profiles associated with the elements of the second set, a distribution of elements of the second set over the categories, which distribution is not constrained to be the same as a distribution of elements of the first set over the categories, wherein a distribution of elements of the second set over the word-stem profiles is not constrained to be the same as a distribution of elements of the first set over the word-stem profiles.