A special interface to denote an exception is expectable -- it means
the exception is not caused by programming error.
It also implies the exception can be resolved by user by retrying
(e.g, for deadlock), correcting (e.g., typo), or fixing (e.g., network
broken).
It is mainly used to denote no to log the message, if possible,
and only shows up a brief description about the exception, and so on.