When Supplier is Greek, the Invoice Id in the fourth segment must be a valid greek document type
GR-R-001-5/pxs-taxdata:TaxData/pxs-taxdata:ReportedTransaction/pxs-taxdata:ReportedDocument/cbc:ID[$isGreekSender]string-length(normalize-space($IdSegments[4]))>0 and (some $c in $greekDocumentType satisfies $IdSegments[4] = $c)