what mean is ~Who is this guy supposed to be?~?

supposed=應該

Who is this guy supposed to be? = 呢個人應該係邊個呀﹖

Example﹕ I am supposed to be home by 8pm, but I don't think I can make it now.

我應該8點就返到家﹐但我諗我趕唔到啦。

2008-01-28 00:00:00 補充：
Example﹕你去睇一套歷事重演嘅戲﹐有一個主角你唔知係扮演邊個﹐ 你會用英文問﹕ Who is this guy supposed to be?如果個演員係扮演算孫中山先生﹐你會用英文答﹕ This guy is supposed to be Dr. Sun Yat Sen.

suppose to be =以為
他以為他是誰?