You can use supposed to suggest that something that people talk about or believe in may not in fact exist, happen, or be as it is described.
Not all developing countries are willing to accept the supposed benefits of free trade.
并非所有发展中国家都愿意接受那些所谓的自由贸易的好处。
be supposed to
If you say that something is supposed to happen, you mean that it is planned or expected. Sometimes this use suggests that the thing does not really happen in this way.
He produced a hand-written list of nine men he was supposed to kill.
他拿出一份手写的名单,上面列了要他杀的九个人。
If something was supposed to happen, it was planned or intended to happen, but did not in fact happen.
He was supposed to go back to Bergen on the last bus, but of course the accident prevented him.
他本应坐最后一班公共汽车回卑尔根,而当然,这场意外拦住了他。
If you say that something is supposed to be true, you mean that people say it is true but you do not know for certain that it is true.
'The Whipping Block' has never been published, but it's supposed to be a really good poem.
《鞭笞刑具》从未发表,但据说是一首相当好的诗。
You can use 'be supposed to' to express annoyance at someone's ideas, or because something is not happening in the right way.
You're supposed to be my friend!
你还是我的朋友呢!