In the 21 century, with the rapid development of the Web and the computer technology,the traditional information services could not meet the information requirement of the user,and the Network Information Service(NIS) is getting more and more attention.

• 21世纪,伴随着网络技术和计算机技术的飞速发展,传统的信息服务已经不能满足信息环境下用户的信息需求,网络信息服务以其独有的优势吸引着人们对它的关注。