2.2.2 Messages
In the event of an application error, the protocol server returns a soap fault as a response to the operation, as specified in [SOAP1.1] section 4.4 or [SOAP1.2/1] section 5.4.
The protocol client MUST ignore all elements of the soap fault, except for the SOAP fault detail element.
The soap fault detail element MUST contain the protocol server alert, as specified in section 2.2.4.24.