HC001 error when running federated SPARQL on endpoint with IDN URL

[jakubklimek]

Try to run this query on any Virtuoso endpoint:

PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT *
WHERE {
  SERVICE <https://slovník.gov.cz/sparql> {
    ?s skos:prefLabel ?termLabel .
  }
}
LIMIT 10

It returns:

Virtuoso HTCLI Error HC001: Connection Error in HTTP Client

SPARQL query:

#output-format:text/html
define sql:signal-void-variables 1 PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT *
WHERE {
  SERVICE <https://slovník.gov.cz/sparql> {
    ?s skos:prefLabel ?termLabel .
  }
}
LIMIT 10

The URL must be punycoded for it to work:

PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
SELECT *
WHERE {
  SERVICE <https://xn--slovnk-7va.gov.cz/sparql> {
    ?s skos:prefLabel ?termLabel .
  }
}
LIMIT 10

[HughWilliams]

@jakubklimek I have been able to recreate this issue and reported to development to look into ...