This Simple DataTypeis specified as a string that is composed of a language component and a country/region component as specified by

IETF RFC 5646. The <country/region> component is always preceded by a hyphen. The format of the LocaleIdstring is shown below:

<language>[-<country/region>], where <language> is the two letter OPC 10000-18, OPC Unified Architecture - Part 18: Role-Based SecurityRole-Based Security

ISO 639 code for a language, <country/region> is the two letter ISO 3166code for the country/region.

The rules for constructing LocaleIdsdefined by

IETF RFC 5646 are restricted as follows:

  1. this specification permits only zero or one <country/region> component to follow the <language> component;
  2. this specification also permits the “-CHS” and “-CHT” three-letter <country/region> codes for “Simplified” and “Traditional” Chinese locales;
  3. this specification also allows the use of other <country/region> codes as deemed necessary by the Clientor the Server.

Table 25shows examples of OPC UA LocaleIds. Clientsand Serversalways provide LocaleIdsthat explicitly identify the language and the country/region.

Table 25– LocaleId Examples


OPC UA LocaleId



English (US)




German (Germany)


German (Austrian)


An empty or null string indicates that the LocaleId is unknown.