Yes, you are correct.

Hi Xiaokaoy, Your thinking is good, though you are mixing two thoughts into the one definition. Firstly future and past tense Should do=Future for something that has not yet been done (I should do more study/exercise) while Should have done=Past for something that in the past you could have done differently (I should have done more study before my exam). Secondly Should and Could Should is used when there is an action (something) that generally society accepts as (more) right or sensible to have done or do. Could is used when there are a number of acceptable possibilities or choices to have done or do.

bai fen zhi bai dui le! What you say looks quite correct. "should" matches pretty exactly with "Yinggai", even to the figurative meanings. We have a saying about "should have": Should have, could have, would have, but didn't. As to the present/future sense, it shos that the speaker is considering as real the possibility of not doing the thing. So, when I hear the word "should", I always think, "there is a 'not' hiding in here". In the past, not is fixed, cannot be changed. In the present and future it is changeable. Compare to I am going to do it, or I am doing it, to I should do it. Zhu hao, benjamin