Unclear error description when validation by schema

When using the Xerces to validate the xml by schema, for example, the content model is '((msisdn,imsi),region)', as you know, the msisdn and imsi is mandatory parameters, if the xml is missing the msisdn element, Xerces will report the error
"Message: Element 'imsi' is not valid for content model:'((msisdn,imsi),region)'"!!

I understand that the 'msisdn' is the first expected mandatory parameter, but xerces get the 'imsi' as the first parameter, so it complain the 'imsi' is not valid.

But could it be possible to change the error description to make it more clear? like "msisdn is missing" something like that...

thanks,
//woods