prSSH IEC 62541-12:2025 ED2:2026

OPC unified architecture - Part 12: Discovery and global services

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.