EN IEC 62541-12:2026

OPC unified architecture - Part 12: Discovery and global services

Publication date:   Mar 17, 2026

Scope

IEC 62541-12:2025 specifies how OPC Unified Architecture (OPC UA) Clients and Servers interact with DiscoveryServers when used in different scenarios. It specifies the requirements for the LocalDiscoveryServer, LocalDiscoveryServer-ME and GlobalDiscoveryServer. It also defines information models for Certificate management, KeyCredential management and AuthorizationServices.

Annex A informatively discusses deployment and configuration aspects.

Annex B defines NodeSet and numeric NodeIds.

Annex F provides installation rules for the LDS.

Annex H compares the Certificate management defined in this document with IETF RFC 7030.

This second edition cancels and replaces the first edition published in 2020. This edition constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous edition:

a) addition of a "Quantity Model" which can be referenced from EngineeringUnit Properties. The model defines quantities and assigned units. In addition it provides alternative units and the conversion to them;

b) addition of rules for ValuePrecision Property:

• can also be used for other subtypes like Duration and Decimal.

• additional rules when ValuePrecision has negative values.