A message shall be first controlled at system level (CONTRL) to detect syntax errors and to acknowledge its receipt. It shall be then transmitted to the application process to be processed.
If an error is detected at the application level, which prevents its complete processing, an APERAK message shall be sent to the original message issuer providing details of the error(s) encountered. In case of application error, the APERAK message processed manually, e.g. when the underlying reason is a programming error. If no error has been detected and when an acknowledgement is necessary (when no dedicated answer to the original message exists) an APERAK message shall be sent specifying the reasons of acknowledgement.
In case of acknowledgement the APERAK message shall be automatically or manually processed at recipient’s discretion.