5. A computer executable method for information clustering, said method making a computer having a central processing unit (CPU) execute the steps of; accumulating and clustering documents in a document repository, said documents including loosely related clusters between said documents being time sliced so as to define chunks of said documents; generating document-keyword vectors, said document-keyword vectors consisting of sparse numeral values depending on presence of keywords in said documents; reducing dimensions of said keywords to create a dimension reduction matrix of said document-keyword matrix; and generating a centroid vector of said cluster, said cluster being retrieved from said document-keyword vector using a principal component in a same line of said dimension reduction matrix, said centroid vectors being defined from keywords and weight of documents within said cluster; and storing said centroid vectors in an item repository together with said keywords and said weights of said centroid vector.
7. The method of claim 5 , said method further comprising the steps of; executing dimension reduction to each of said chunks of said dimension reduction matrix and generating clusters for every chunk of said dimension reduction matrix.