It was built in 1420 in the early ming dynasty and renovated in 1977 . in the old days , watchtowers placed at regular intervals around the perimeter guarded the wall . the double gate system played an important role in repulsing enemy attacks 明清时期正阳门城楼与箭楼之间原有一个巨大的瓮城，南端呈弧形抹角，箭楼坐落在顶端，瓮城南北长108米，东西宽88米，内有空场，四向均有门。
2.
At first , information security in internet environment is analyzed in this paper , under the situation of an enterprise in jiangxi , in which the implement of supply chain management information system is carried out . then based on some approaches in common use for resolving information security , and based on the fact of this enterprise , this paper from point of view of physical isolation brings a new way named " wengcheng " strategy to resolve this problem 本文首先就江西某企业实施网络环境下的供应链管理信息系统带来的信息安全问题作了一定的分析，并在比较目前常用的几种信息安全解决方案的基础上，根据企业实际应用背景，从物理隔离的角度出发，提出了“瓮城”信息安全解决总体架构模型。
