#What is the return value to consider SUCCESS /FAILURE of calling an appian pro

#What is the return value to consider SUCCESS /FAILURE of calling an appian process model which is published as a web service.
This below url does not tell the process to call or what is considered a successfull start.
I know to some extent that a pid is returned, it could be bot +ve or -ve
is a ZERO return value considered failure? and any other integer considered a success.
forum.appian.com/.../Publishing_Process_Models_as_Web_Services...

OriginalPostID-99510

OriginalPostID-99510