1. Introduction
With the rapid development of the Internet technology, information on the Internet has been growing explosively. Locating relevant information on the Internet is time-consuming and expensive. To help people overcome the difficulty of information overload, various personalized information filtering system have emerged [3], [4], [7], [11], [12]. However, most of them represent documents as a set of key words of mutual independent, and thus the intrinsic structures of the documents and the semantic information embodied in them are neglected. The information filtering mainly depended on the matching of simple key word or bag of words. That is to say, the traditional information filtering system can not very well describe and depict document information, user interests and the similarity between them, which results in the users being surrounded and puzzled by vast irrelevant information and failing to find their interested information.