The LocaleIds with DataType LocaleId defines a list of locale ids in priority order for localized strings for all DataSetWriters in the WriterGroup. The first LocaleId in the list has the highest priority.
If the Publisher sends a localized String, the Publisher shall send the translation with the highest priority that it can. If it does not have a translation for any of the locales identified in this list, then it shall send the String value that it has and include the LocaleId with the String. If no locale id is configured, the Publisher shall use any that it has. See OPC 10000-3 for more detail on LocaleId.