From the point of structure features, SIS is an open-loop system, that is, the input of SIS comes from DCS, and output is to display the operation results.

• 从SIS结构特征看,它的输入来自分散控制系统(DCS),输出仅是运行结果的显示,而其功能还在不断发展,因此说SIS是“开环”系统。