Message

Only references to an attachment are allowed.

Context
ubl:EnquiryResponse/cac:AdditionalDocumentReference/cbc:XPath
Test
matches(./text(), '^/EnquiryResponse/([a-zA-Z]+:)?Attachment\[\d?\]')
Usage
/ t008:EnquiryResponse / cac:AdditionalDocumentReference / cbc:XPath