Message

Value MUST be part of code list 'Recommendation 20, including Recommendation 21 codes - prefixed with X (UN/ECE)'.

Context
/ubl:OrderResponse/cac:OrderLine/cac:LineItem/cbc:Quantity
Test
not(@unitCode) or (some $code in $clUNECERec20 satisfies $code = @unitCode)
Code lists
Recommendation 20, including Recommendation 21 codes - prefixed with X (UN/ECE)
Usage
/ ubl:OrderResponse / cac:OrderLine / cac:LineItem / cbc:Quantity / @unitCode