1 ) A system for information clustering, said system comprising; a data accumulation part for 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; a vector space generation part for generating document-keyword vectors, said document-keyword vectors consisting of sparse numeral values depending on presence of keywords in said documents; a dimension reduction part for reducing dimensions of said keywords to create a dimension reduction matrix of said document-keyword matrix; a centroid vector determination part for 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 an item repository for storing said centroid vectors together with said keywords and said weights of said centroid vector.