This driver depends on GDAL/OGR being built with the Xerces XML parsing library.
This driver was implemented within the context of the PostNAS project which has more information on it's use.
The driver looks for "opengis.net/gml" and one of the strings semicolon separated strings listed in the option NAS_INDICATOR (which defaults to "NAS-Operationen.xsd;NAS-Operationen_optional.xsd;AAA-Fachschema.xsd") to determine if a input is a NAS file and ignores all files without any matches.