Message

Value added tax point date (BT-7) and Value added tax point date code (BT-8) are mutually exclusive.

Context
/ubl:Invoice | /cn:CreditNote
Test
(exists(cbc:TaxPointDate) and not(cac:InvoicePeriod/cbc:DescriptionCode)) or (not(cbc:TaxPointDate) and exists(cac:InvoicePeriod/cbc:DescriptionCode)) or (not(cbc:TaxPointDate) and not(cac:InvoicePeriod/cbc:DescriptionCode))
Usage
/ ubl:Invoice / cbc:TaxPointDate
/ ubl:Invoice / cac:InvoicePeriod / cbc:DescriptionCode
/ ubl:CreditNote / cbc:TaxPointDate
/ ubl:CreditNote / cac:InvoicePeriod / cbc:DescriptionCode