References 1. Book Principles of Information Science> BUPT Press, 1988(Ist Edition),1996(2nd) 20023rd edition) 2. Web-site http://www.bupt.edu.cn/camnet/zyxdoc2/index.htmlReferences 1. Book <Principles of Information Science> BUPT Press, 1988 (1st Edition), 1996 (2nd) 2002(3rd Edition) 2. Web-site http://www.bupt.edu.cn/camnet/zyxdoc2/index.html