Message

GLN must have a valid format according to GS1 rules.

Context
cbc:EndpointID[@schemeID = '0088'] | cac:PartyIdentification/cbc:ID[@schemeID = '0088'] | cbc:CompanyID[@schemeID = '0088']
Test
matches(normalize-space(), '^[0-9]+$') and u:gln(normalize-space())