The base class in the Thread-compatible Exception package is RWTHRxmsg, which derives from the class RWxmsg, from the Essential Tools Module. A thread-compatible exception can be copied and stored, so that it can be rethrown in the future. This capability, which makes passing across thread boundaries possible, comes from the RWTHRxmsg member functions clone() and raise(). For more information about passing exceptions across thread boundaries, see Catching and Rethrowing Exceptions.