Patent ID: 6965898

Claim:
An information retrieval system for retrieving documents added to a database with respect to time, said documents being converted into a document-attribute matrix and stored within said information retrieval system, and said document-attribute matrix being constituted by document-attribute submatrices added in order with respect to time, said information retrieval system comprising: means for generating and storing a predetermined type matrix from said document-attribute matrix, means for executing QR decomposition of said document-attribute matrix and using only a matrix R as said predetermined matrix, wherein the matrix R is an upper triangular matrix obtained by said QR decomposition, means for generating a document-attribute submatrix from said documents being added to said database during a specific time period, means for updating said predetermined type matrix using knowledge with respect to said document-attribute submatrix and for executing a singular value decomposition on said updated predetermined type matrix to execute dimension reduction of all document-attribute matrices stored within said database, and means for retrieving information with respect to a user input query using said dimension reduced document-attribute matrices.