以缺席为标志

The teacher marked him down as absent.───这位老师把他作为缺席者记下来。

Three of the pupils were marked absent.───三名注明缺席。

For one thing, missing data is not explicitly indicated, but is simply marked by an absent line and time stamp.───一方面，没有显式地标明丢失的数据，而只是通过不存在的行和时间戳进行了简单的标记。