[BR-110-SG]-Order references in an Invoice shall be provided on either Invoice Line level or on Document level, not both.
BR-110-SG
/ubl:Invoice | /cn:CreditNote
not(exists(cac:OrderReference/cbc:ID[text()!= 'NA']) and exists((cac:InvoiceLine | cac:CreditNoteLine)/cac:OrderLineReference/cac:OrderReference/cbc:ID))