IEC 62541-3:2025

Overview

IEC 62541-3:2025 - OPC Unified Architecture (OPC UA) Part 3: Address Space Model defines the OPC UA meta‑model used to create interoperable OPC UA information models. Edition 4.0 (2025) replaces the 2020 edition and constitutes a technical revision. It specifies the AddressSpace concepts: NodeClasses, Attributes, References, Variables, Objects, DataTypes, Methods, Events and TypeDefinitions that form the foundation for OPC UA servers, clients and information models used in industrial automation and IIoT.

Key topics and technical changes

This edition documents the Address Space Model and introduces several significant technical updates and requirements:

• AddressSpace fundamentals: Node model, Object model, NodeClasses, Attributes, References, ModellingRules, subtyping and instantiation.
• Variables and DataTypes: DataVariable, Property handling, encodings and standard DataTypes (NodeId, QualifiedName, LocalizedText).
• Events and Methods: EventTypes, event categorization, Methods and argument metadata.
• Security & access controls: RolePermissions, UserRolePermissions, AccessRestrictions and the new ApplyRestrictionToBrowse bit.
• Interfaces and AddIns: New modelling elements to support reusable interface definitions and AddIns for objects.
• Method Meta Data: Additional attributes for method arguments to improve metadata and interoperability.
• New attributes:
  • Currency for monetary contexts.
  • Non‑Volatile Storage bit in AccessLevelExType to indicate persisted values.
  • Constant and ConfigurationConstant bits for AccessLevelExType for static/configuration data.
• NodeClass and Reference updates:
  • View NodeClass now defines EventNotifier as an EventNotifierType.
  • Corrections to HasNotifier, HasEventSource and Organizes to include ObjectType as valid sources.
  • AssociatedWith ReferenceType added.
• Deprecation: NamingRules have been deprecated.

Applications and who should use it

IEC 62541-3:2025 is essential for professionals designing, implementing or integrating OPC UA systems:

• System architects & information model designers: to define consistent, reusable OPC UA information models (digital twins, asset models).
• Industrial automation vendors & integrators: to ensure server/client interoperability across PLCs, SCADA, MES and cloud platforms.
• Software developers: implementing OPC UA stacks, SDKs and tools that serialize NodeIds, handle References, Methods, Events and DataTypes.
• Cybersecurity and operations teams: to understand AccessLevel/AccessRestriction semantics and role-based permissions.

Practical uses include building interoperable IIoT solutions, standardized asset representations, secure data exchange for monitoring, control, analytics and lifecycle management.

Related standards

• IEC 62541 series (OPC UA) - other parts define architecture, services, information model mapping and profiles. Use IEC 62541-3:2025 together with the rest of the OPC UA specification set for full implementation guidance.

Keywords: OPC UA, Address Space Model, IEC 62541-3:2025, information models, NodeClasses, Interfaces, AddIns, Method Meta Data, AccessLevelExType, industrial automation, IIoT.