IEC 62541-3-2025 PDF

Full title and description

St IEC 62541-3-2025 — OPC Unified Architecture (OPC UA) — Part 3: Address Space Model. This publication is the fourth edition that defines the OPC UA AddressSpace meta‑model used to describe Nodes, NodeClasses, References, Attributes, Types, Variables, Objects, Methods and Events for OPC UA information models, servers and clients.

Abstract

This edition (2025) is a technical revision of Part 3 that updates and extends the Address Space Model. It introduces modelling elements such as Interfaces and AddIns, expands data and access semantics (e.g., Currency, Method metadata, AccessLevelEx bits), adjusts the View NodeClass and ReferenceTypes, and deprecates some previous modelling rules while clarifying instantiation and type definitions. It cancels and replaces IEC 62541-3:2020.

General information

• Status: Published / Current edition (4.0).
• Publication date: 22 December 2025.
• Publisher: International Electrotechnical Commission (IEC), TC 65/SC 65E.
• ICS / categories: 25.040.40 (Industrial process measurement and control); 35.100.05 (Multilayer applications).
• Edition / version: 4.0 (fourth edition; replaces 2020 edition).
• Number of pages: 138 pages.

Key bibliographic and edition facts above are based on the IEC publication record for IEC 62541-3:2025.

Scope

Specifies the OPC UA AddressSpace meta‑model: the structure and semantics of Nodes, NodeClasses (Object, Variable, Method, DataType, ReferenceType, View, etc.), Attributes, References, ModellingRules, TypeDefinitions and the rules for subtyping and instantiation that information models and OPC UA servers/clients must follow. The scope covers how Variables, DataTypes, Methods and Events are modeled and how access, roles/permissions and restrictions are expressed in the AddressSpace. This edition adds specific modelling elements and access flags to support richer information modelling.

Key topics and requirements

• AddressSpace fundamentals: Node model, NodeClasses, Attributes, References, ModellingRules, subtyping and instantiation semantics.
• Variables and DataTypes: Variable nodes, Properties, encodings and standard data types (QualifiedName, LocalizedText, NodeId, etc.).
• Methods and Method metadata: argument metadata and enhanced method description capabilities added in this edition.
• Events and EventTypes: Event modeling, EventNotifier semantics and changes to View NodeClass event notifier handling.
• Access control and restrictions: RolePermissions/UserRolePermissions, AccessRestrictionType enhancements (ApplyRestrictionToBrowse) and AccessLevelEx extensions (Non‑Volatile Storage, Constant and ConfigurationConstant bits).
• Interfaces and AddIns: new modelling constructs to support reusable interface definitions and object AddIns for composition and reuse.
• ReferenceTypes and naming: additions such as AssociatedWith ReferenceType and deprecation/clarification of certain previous NamingRules.

Typical use and users

Used by information model authors, OPC UA server and client implementers, device and equipment manufacturers, integration architects, system integrators, OT/IT engineers and certification/test labs. The standard is applied when designing or verifying OPC UA servers, creating information models for devices or systems, and ensuring interoperability between OPC UA applications.

Related standards

Part of the IEC 62541 (OPC UA) multi‑part family. Related and frequently referenced parts include: Part 1 (Overview and concepts), Part 2 (Security model), Part 4 (Services), Part 5 (Information model), Part 6 (Mappings), Part 7 (Profiles), Part 8 (Data Access), Part 9 (Alarms & Conditions), Part 10 (Programs), Part 11 (Historical Access), Part 12 (Discovery) and Part 14 (PubSub), among others in the series. Users should consult the other Parts for Services, mappings and domain‑specific models that work together with Part 3.

Keywords

OPC UA, Address Space, NodeClass, NodeId, ModellingRules, Information Model, Interfaces, AddIns, AccessLevelEx, EventNotifier, Method metadata, IEC 62541-3, industrial automation, IIoT.

FAQ

Q: What is this standard?

A: IEC 62541-3:2025 (Part 3 of the OPC UA series) is the international standard that defines the OPC UA AddressSpace meta‑model used to describe nodes, types, relationships and behaviour for OPC UA information models and servers.

Q: What does it cover?

A: It specifies the structure and semantics of the AddressSpace: NodeClasses (Objects, Variables, Methods, DataTypes, ReferenceTypes, Views), Attributes, References, TypeDefinitions, ModellingRules, events, methods and access semantics (roles, permissions, access restrictions), including several updates introduced in the 2025 edition.

Q: Who typically uses it?

A: OPC UA implementers (server/client stack developers), device manufacturers, information model designers, system integrators, OT/IT engineers and conformity test laboratories. It is essential for anyone building interoperable OPC UA systems or defining standard information models.

Q: Is it current or superseded?

A: The 2025 edition (4.0) is the current published edition and it cancels and replaces IEC 62541-3:2020 (third edition). The 2020 edition is therefore superseded by the 2025 revision.

Q: Is it part of a series?

A: Yes — IEC 62541 is a multi‑part standard (OPC UA). Part 3 works together with other Parts (Part 1, Part 4, Part 5, etc.) that define overview, services, information models and mappings for OPC UA.

Q: What are the key keywords?

A: OPC UA, AddressSpace, Node, NodeClass, Reference, ModellingRule, DataType, Method, Event, Interface, AddIn, AccessLevelEx, AccessRestriction.