Patent ID: 7185008

Claim:
A method of classifying a given input document into at least one document class, the method using a machine readable code embodied in a computer readable medium and that is executable using a computer, comprising: classifying the given input document via: (a) selecting terms for use in the classification, from among terms that occur in the input document; (b) dividing the input document into document segments in predetermined units; (c) generating document segment vectors whose components are values relevant to occurrence frequencies of the selected terms occurring in the document segments, and generating a document vector in which all of the document segment vectors are added together; (d) calculating a similarity between the input document and each class using information saved for every document class; (e) correcting the similarity to each class; and (f) determining and outputting the class to which the input document belongs in accordance with the corrected similarity to each class; wherein the similarity to each class is corrected by: adding a weighted sum of squared inner products between at least one positive topic difference factor vector saved for every document class and the respective document segment vectors, to the similarity of the input document to each class; and further correcting the similarity by subtracting a weighted sum of squared inner products between at least one negative topic difference factor vector saved for every document class and the respective document segment vectors from the similarity to each class.