1. A computer-implemented method of constructing a personalized category tree, said method comprising: using an information processing device to perform steps of: allowing semantic inconsistencies in the personalized category tree, wherein each node is independent of each other node; receiving, at an input device, from a user an arbitrarily defined personalized category tree used for categorizing and storing documents for a computer search, wherein the category tree comprises a plurality of category nodes, a label for each of the category nodes, a keyword used in searching, and a user-introduced inconsistency in semantics introduced into the category tree, wherein each of the category nodes is equal to and independent of each other thereby allowing the semantic inconsistencies; wherein generating each of said at least one category nodes independently comprises using an information processing device to perform steps of: defining a label for said category node; specifying at least one keyword for said category node; storing in a storage device the arbitrarily defined personalized category tree said user creating said personalized category tree to be similar to said user's file folder hierarchy; said user freely mapping a semantic structure that meets said user's demands onto said personalized category tree, without said user being limited by traditional semantic consistency; satisfying said user's personal needs without said user manually specifying a large amount of training samples; and realizing said user's personalized document categorization.