Message

FileName values MUST be unique.

Context
ubl:Tender
Test
count(distinct-values(cac:DocumentReference/cac:Attachment/cac:ExternalReference/cbc:FileName)) = count(cac:DocumentReference/cac:Attachment/cac:ExternalReference/cbc:FileName)
Usage
/ t005:Tender / cac:DocumentReference / cac:Attachment / cac:ExternalReference / cbc:FileName