1. A storage medium readable by a computer, the storage medium storing a program for causing a computer connected to a document database where document files are categorized and stored into any of predefined category bins to perform a process comprising: selecting at least some of document files stored on the document database and categorized in object category bins as representative document files for each of the object category bins, the document files being selected as representative document files based on similarity to a document file to be categorized, the object category bins being at least part of the category bins, the representative document files comprising a proper subset of the document files categorized in each respective object category bin associated with the representative document files; and presenting information extracted from the selected representative document files to a user when the user queries contents of an object category bin of the object category bins without entering the object category bin, wherein a guide caption is presented describing keywords extracted from a file and obtained by a document summarizing process, and a highlight contrast to a background for guide captions of files having greater weights regarding access histories is increased.