[ibr-159-ae]-Currency exchange rate [BTAE-04] is MUST when then Invoice currency code [IBT-005] is different from 'AED'.
ibr-159-ae/ubl:Invoice | /cn:CreditNote(cbc:DocumentCurrencyCode != "AED" and (exists(//cbc:CalculationRate))) or cbc:DocumentCurrencyCode = "AED"