A number of Services expect an array of LocaleIds which are used by a Server to determine in what language or languages LocalizedText should be returned.

The array of LocaleIds is in the preferred order the Client would like the Server to use when selecting the locale of the LocalizedText to be returned. The first LocaleId in the list is the most preferred. If the Server returns a LocalizedText to the Client, the Server shall return the translation which is the most preferred that it can. If it does not have a translation for any of the locales identified in this list, then it shall return LocalizedText in an available locale. See OPC 10000-3 for more details on LocaleIds. If the Client fails to specify at least one LocaleId, the Server shall return any one that it has.

Multi-language LocalizedText can be requested using the special ‘mul’ or ‘qst’ locales as the first entry of the list. See OPC 10000-3 for detail of the special locales and how LocalizedText is used with them. If there are no further entries, the Server shall return all languages available. If there are more languages included after ‘mul’ or ‘qst’, the Server shall return only those languages from that list. If the Server doesn’t have a translation for any of the locales included in the list, then it shall return LocalizeText in an available locale. The special ‘mul’ or ‘qst’ locales shall not be used in Write.

If a Client requests ‘mul’ it shall be prepared to receive a ‘mul’ or another locale, but not ‘qst’ depending on what the Server can provide for a particular LocalizedText.

If a Client requests ‘qst’ it shall be prepared to receive a ‘qst’, ‘mul’ or another locale depending on what the Server can provide for a particular LocalizedText.