1. A computer-based method of associating an unstructured object with a category, comprising: receiving an unstructured object, the unstructured object being associated with at least one concept; calculating an inverted category ratio and a concept ratio for each concept associated with the unstructured object, the inverted category ratio for a concept being exp(−Nci/Nc), Nc being the number of categories in the plurality of categories and Nci being the number of categories in which that concept occurs; the concept ratio for a concept being the ratio of the number of times that concept occurs in the unstructured object over the total number of concepts that occur in the unstructured object; calculating a category normalization ratio for each category in a plurality of categories; associating the unstructured object with at least one category in the plurality of categories based on the inverted category ratio, the concept ratio, and the category normalization ratio; and outputting, to a user display, information showing the correspondence between the unstructured object and the at least one category.