IEC 62541-3:2025

OPC Unified Architecture - Part 3: Address Space Model

IEC 62541-3: 2025 describes the OPC Unified Architecture (OPC UA) AddressSpace and its Objects. This specification is the OPC UA meta model on which OPC UA information models are based. This fourth edition cancels and replaces the third 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 the concept and modelling elements for Interfaces and AddIns;
b) addition of Currency;
c) addition of Method Meta Data to define additional attributes for Method Arguments;
d) addition of ApplyRestrictionToBrowse bit to AccessRestrictionType;
e) addition of a Non-Volatile Storage bit to AccessLevelExType;
f) addition of a Constant bit and ConfigurationConstant bit to AccessLevelExType;
g) the View NodeClass has been changed to define the EventNotifier as an EventNotifierType in the same way the Object NodeClass defines it;
h) correctition of HasNotifier, HasEventSource, and Organizes, to include ObjectType as valid source node;
i) NamingRules have become deprecated;
j) addition of AssociatedWith ReferenceType.

Architecture unifiée OPC - Partie 3: Modèle d'espace d'adressage

IEC 62541-3: 2025 décrit l'AddressSpace de l'Architecture unifiée OPC (OPC UA) et ses Objets. La présente spécification correspond au métamodèle OPC UA sur lequel se fondent les modèles d'information OPC UA. Cette quatrième édition annule et remplace la troisième édition parue en 2020. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) ajout du concept et des éléments de modélisation pour les Interfaces et AddIns;
b) ajout de Currency;
c) ajout des Métadonnées de Méthode afin de définir des attributs supplémentaires pour les Arguments de Méthode;
d) ajout du bit ApplyRestrictionToBrowse à AccessRestrictionType;
e) ajout d'un bit de mémoire rémanente à AccessLevelExType;
f) ajout d'un bit Constant et d'un bit ConfigurationConstant à AccessLevelExType;
g) modification de la NodeClass View pour définir l'EventNotifier comme un EventNotifierType de la même manière que la NodeClass Object le définit;
h) correction de HasNotifier, HasEventSource et Organizes afin d'inclure ObjectType comme nœud source valide;
i) dépréciation de NamingRules;
j) ajout du ReferenceType AssociatedWith.

General Information

• Status: Published
• Publication Date: 21-Dec-2025
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.100.05 - Multilayer applications
• Technical Committee: SC 65E - Devices and integration in enterprise systems
• Drafting Committee: WG 8 - TC 65/SC 65E/WG 8
• Current Stage: PPUB - Publication issued
• Start Date: 22-Dec-2025
• Completion Date: 10-Dec-2025

Relations

• Revises: IEC 62541-3:2020 - OPC Unified Architecture - Part 3: Address Space Model
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 62541-3 ®
Edition 4.0 2025-12
INTERNATIONAL
STANDARD
REDLINE VERSION
OPC unified architecture -
Part 3: Address Space Model
ICS 25.040.40; 35.100.05 ISBN 978-2-8327-0972-6
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CONTENTS
FOREWORD. 10
1 Scope . 13
2 Normative references . 13
3 Terms, definitions, abbreviations and conventions . 14
3.1 Terms and definitions . 14
3.2 Abbreviated terms . 15
3.3 Conventions . 16
3.3.1 Conventions for AddressSpace figures . 16
3.3.2 Conventions for defining NodeClasses . 16
4 AddressSpace concepts. 17
4.1 Overview . 17
4.2 URIs . 18
4.3 Object Model . 19
4.4 Node Model . 19
4.4.1 General . 19
4.4.2 NodeClasses . 20
4.4.3 Attributes . 20
4.4.4 References . 20
4.5 Variables . 21
4.5.1 General . 21
4.5.2 Properties . 21
4.5.3 DataVariables . 21
4.6 TypeDefinitionNodes . 22
4.6.1 General . 22
4.6.2 Complex TypeDefinitionNodes and their InstanceDeclarations . 22
4.6.3 Subtyping . 23
4.6.4 Instantiation of complex TypeDefinitionNodes . 24
4.7 Event Model . 25
4.7.1 General . 25
4.7.2 EventTypes . 25
4.7.3 Event Categorization . 26
4.8 Methods . 26
4.9 Roles . 26
4.9.1 Overview . 26
4.9.2 Well Known Roles . 27
4.9.3 Evaluating Permissions with Roles . 28
4.10 Interfaces and AddIns for Objects . 30
4.10.1 Overview . 30
4.10.2 Interface Model . 30
4.10.3 AddIn model . 34
5 Standard NodeClasses . 35
5.1 Overview . 35
5.2 Base NodeClass . 36
5.2.1 General . 36
5.2.2 NodeId . 36
5.2.3 NodeClass . 36
5.2.4 BrowseName . 36
5.2.5 DisplayName . 37
5.2.6 Description . 37
5.2.7 WriteMask . 37
5.2.8 UserWriteMask . 37
5.2.9 RolePermissions . 38
5.2.10 UserRolePermissions . 39
5.2.11 AccessRestrictions . 39
5.3 ReferenceType NodeClass . 39
5.3.1 General . 39
5.3.2 Attributes . 40
5.3.3 References . 42
5.4 View NodeClass . 42
5.5 Objects . 44
5.5.1 Object NodeClass . 44
5.5.2 ObjectType NodeClass . 46
5.5.3 Standard ObjectType FolderType . 48
5.5.4 Client-side creation of Objects of an ObjectType . 48
5.6 Variables . 49
5.6.1 General . 49
5.6.2 Variable NodeClass . 49
5.6.3 Properties . 53
5.6.4 DataVariable . 54
5.6.5 VariableType NodeClass . 55
5.6.6 Client-side creation of Variables of an VariableType . 57
5.7 Methods . 57
5.7.1 Method NodeClass . 57
5.7.2 HasArgumentDescription ReferenceType . 61
5.7.3 HasOptionalInputArgumentDescription ReferenceType . 61
5.8 DataTypes . 61
5.8.1 DataType Model . 61
5.8.2 Encoding Rules for different kinds of DataTypes . 62
5.8.3 DataType NodeClass . 63
5.8.4 DataTypeEncoding and Encoding Information . 66
5.9 Summary of Attributes of the NodeClasses . 66
6 Type Model for ObjectTypes and VariableTypes . 67
6.1 Overview . 67
6.2 Definitions . 68
6.2.1 InstanceDeclaration . 68
6.2.2 Instances without ModellingRules . 68
6.2.3 InstanceDeclarationHierarchy . 68
6.2.4 Similar Node of InstanceDeclaration . 68
6.2.5 BrowsePath . 68
6.2.6 BrowseName within a TypeDefinitionNode . 68
6.2.7 Attribute Handling of InstanceDeclarations . 69
6.2.8 Attribute Handling of Variable and VariableTypes . 69
6.2.9 NodeIds of InstanceDeclarations . 69
6.3 Subtyping of ObjectTypes and VariableTypes . 69
6.3.1 Overview . 69
6.3.2 Attributes . 69
6.3.3 InstanceDeclarations . 69
6.4 Instances of ObjectTypes and VariableTypes . 74
6.4.1 Overview . 74
6.4.2 Creating an Instance . 74
6.4.3 Constraints on an Instance . 75
6.4.4 ModellingRules . 76
6.5 Changing Type Definitions that are already used . 85
7 Standard ReferenceTypes . 86
7.1 General . 86
7.2 References ReferenceType . 86
7.3 HierarchicalReferences ReferenceType . 87
7.4 NonHierarchicalReferences ReferenceType . 87
7.5 HasChild ReferenceType . 87
7.6 Aggregates ReferenceType . 87
7.7 HasComponent ReferenceType . 88
7.8 HasProperty ReferenceType . 88
7.9 HasOrderedComponent ReferenceType . 88
7.10 HasSubtype ReferenceType . 88
7.11 Organizes ReferenceType . 89
7.12 HasModellingRule ReferenceType . 89
7.13 HasTypeDefinition ReferenceType . 89
7.14 HasEncoding ReferenceType . 89
7.15 GeneratesEvent . 90
7.16 AlwaysGeneratesEvent . 90
7.17 HasEventSource . 90
7.18 HasNotifier . 91
7.19 HasInterface ReferenceType . 92
7.20 HasAddIn ReferenceType . 92
7.21 IsDeprecated ReferenceType . 93
7.22 HasStructuredComponent ReferenceType . 93
7.22.1 Overview . 93
7.22.2 Differences between HasStructuredComponent and ExposesItsArray . 94
7.23 AssociatedWith ReferenceType . 95
8 Standard DataTypes . 95
8.1 General . 95
8.2 NodeId . 95
8.2.1 General . 95
8.2.2 NamespaceIndex . 96
8.2.3 IdentifierTypeIdType . 96
8.2.4 Identifier value . 97
8.3 QualifiedName . 97
8.4 LocaleId . 98
8.5 LocalizedText . 98
8.6 Argument . 99
8.7 BaseDataType . 99
8.8 Boolean . 100
8.9 Byte . 100
8.10 ByteString . 100
8.11 DateTime . 100
8.12 Double . 100
8.13 Duration . 100
8.14 Enumeration . 100
8.15 Float . 100
8.16 Guid . 100
8.17 Sbyte . 100
8.18 IdType . 101
8.19 Image . 101
8.20 ImageBMP . 101
8.21 ImageGIF . 101
8.22 ImageJPG . 101
8.23 ImagePNG . 101
8.24 Integer . 101
8.25 Int16 . 101
8.26 Int32 . 101
8.27 Int64 . 101
8.28 TimeZoneDataType . 101
8.29 NamingRuleType .
8.29 NodeClass . 102
8.30 Number . 103
8.31 String . 103
8.32 Structure . 103
8.33 Uinteger . 103
8.34 Uint16 . 103
8.35 Uint32 . 103
8.36 Uint64 . 103
8.37 UtcTime . 103
8.38 XmlElement . 104
8.39 EnumValueType . 104
8.40 OptionSet . 104
8.41 Union . 105
8.42 DateString . 106
8.43 DecimalString . 106
8.44 DurationString . 106
8.45 NormalizedString . 106
8.46 TimeString . 107
8.47 DataTypeDefinition . 107
8.48 StructureDefinition . 107
8.49 StructureType . 108
8.50 EnumDefinition . 108
8.51 StructureField . 108
8.52 EnumField . 109
8.53 AudioDataType . 110
8.54 Decimal . 110
8.55 PermissionType . 110
8.56 AccessRestrictionType . 111
8.57 AccessLevelType . 112
8.58 AccessLevelExType . 112
8.59 EventNotifierType . 114
8.60 AttributeWriteMask . 114
8.61 CurrencyUnitType . 115
9 Standard EventTypes . 116
9.1 General . 116
9.2 BaseEventType . 117
9.3 SystemEventType . 117
9.4 ProgressEventType . 117
9.5 AuditEventType . 118
9.6 AuditSecurityEventType . 119
9.7 AuditChannelEventType . 119
9.8 AuditOpenSecureChannelEventType . 119
9.9 AuditSessionEventType . 119
9.10 AuditCreateSessionEventType . 120
9.11 AuditUrlMismatchEventType . 120
9.12 AuditActivateSessionEventType . 120
9.13 AuditCancelEventType . 120
9.14 AuditCertificateEventType . 120
9.15 AuditCertificateDataMismatchEventType . 120
9.16 AuditCertificateExpiredEventType . 120
9.17 AuditCertificateInvalidEventType . 120
9.18 AuditCertificateUntrustedEventType . 120
9.19 AuditCertificateRevokedEventType . 121
9.20 AuditCertificateMismatchEventType . 121
9.21 AuditNodeManagementEventType . 121
9.22 AuditAddNodesEventType . 121
9.23 AuditDeleteNodesEventType . 121
9.24 AuditAddReferencesEventType . 121
9.25 AuditDeleteReferencesEventType . 121
9.26 AuditUpdateEventType . 121
9.27 AuditWriteUpdateEventType . 121
9.28 AuditHistoryUpdateEventType . 121
9.29 AuditUpdateMethodEventType. 121
9.30 DeviceFailureEventType . 122
9.31 SystemStatusChangeEventType . 122
9.32 ModelChangeEvents . 122
9.32.1 General . 122
9.32.2 NodeVersion Property . 122
9.32.3 Views . 122
9.32.4 Event compression . 122
9.32.5 BaseModelChangeEventType . 123
9.32.6 GeneralModelChangeEventType . 123
9.32.7 Guidelines for ModelChangeEvents . 123
9.33 SemanticChangeEventType . 123
9.33.1 General . 123
9.33.2 ViewVersion and NodeVersion Properties . 123
9.33.3 Views . 124
9.33.4 Event compression . 124
Annex A (informative) How to use the Address Space Model . 125
A.1 Overview . 125
A.2 Type definitions . 125
A.3 ObjectTypes . 125
A.4 VariableTypes . 126
A.4.1 General . 126
A.4.2 Properties or DataVariables . 126
A.4.3 Many Variables and / or Structured DataTypes . 126
A.5 Views . 127
A.6 Methods . 127
A.7 Defining ReferenceTypes . 127
A.8 Defining ModellingRules . 127
Annex B (informative) OPC UA Meta Model in UML . 128
B.1 Background . 128
B.2 Notation . 128
B.3 Meta Model . 129
B.3.1 Base . 129
B.3.2 ReferenceType . 130
B.3.3 Predefined ReferenceTypes . 131
B.3.4 Attributes . 131
B.3.5 Object and ObjectType . 132
B.3.6 EventNotifier . 133
B.3.7 Variable and VariableType . 133
B.3.8 Method . 134
B.3.9 DataType . 135
B.3.10 View . 136
Annex C (normative) Graphical notation . 137
C.1 General . 137
C.2 Notation . 137
C.2.1 Overview . 137
C.2.2 Simple notation . 137
C.2.3 Extended notation . 139
Bibliography . 142

Figure 1 – AddressSpace Node diagrams . 16
Figure 2 – OPC UA Object Model . 19
Figure 3 – AddressSpace Node Model . 20
Figure 4 – Reference Model . 21
Figure 5 – Example of a Variable defined by a VariableType . 22
Figure 6 – Example of a Complex TypeDefinition . 23
Figure 7 – Object and its Components defined by an ObjectType . 24
Figure 8 – Examples of Interfaces . 32
Figure 9 – Example: Interface application to an ObjectType . 32
Figure 10 – Example: One Interface applied to an ObjectType another one to the
instance . 33
Figure 11 – Example: Interface Hierarchy . 33
Figure 12 – Example of AddIn with default BrowseName . 34
Figure 13 – Example of AddIn applied to an instance . 35
Figure 14 – Permissions in the Address Space . 39
Figure 15 – Symmetric and Non-Symmetric References . 41
Figure 16 – Method Metadata Example . 60
Figure 17 – Variables, VariableTypes and their DataTypes . 61
Figure 18 – DataType Model . 62
Figure 19 – Example of DataType Modelling . 66
Figure 20 – Subtyping TypeDefinitionNodes . 70
Figure 21 – The Fully-Inherited InstanceDeclarationHierarchy for BetaType . 73
Figure 22 – An Instance and its TypeDefinitionNode . 74
Figure 23 – Example for several References between InstanceDeclarations . 76
Figure 24 – Example on changing instances based on InstanceDeclarations . 78
Figure 25 – Example on changing InstanceDeclarations based on an
InstanceDeclaration . 79
Figure 26 – Use of the Standard ModellingRule Mandatory . 80
Figure 27 – Example using the Standard ModellingRules Optional and Mandatory . 81
Figure 28 – Example on using ExposesItsArray . 82
Figure 29 – Complex example on using ExposesItsArray . 82
Figure 30 – Example using OptionalPlaceholder with an Object and Variable . 83
Figure 31 – Example using OptionalPlaceholder with a Method . 84
Figure 32 – Example on using MandatoryPlaceholder for Object and Variable . 85
Figure 33 – Standard ReferenceType Hierarchy . 86
Figure 34 – Event Reference Example. 91
Figure 35 – Complex Event Reference Example . 92
Figure 36 – Example of using HasStructuredComponent ReferencyType . 94
Figure 37 – Difference between HasStructuredComponent and ExposesItsArray . 95
Figure 38 – Standard EventType Hierarchy . 117
Figure 39 – Audit Behaviour of a Server . 118
Figure 40 – Audit Behaviour of an Aggregating Server . 119
Figure B.1 – Background of OPC UA Meta Model . 128
Figure B.2 – Notation (I). 128
Figure B.3 – Notation (II). 129
Figure B.4 – Base . 130
Figure B.5 – Reference and ReferenceType . 130
Figure B.6 – Predefined ReferenceTypes . 131
Figure B.7 – Attributes . 132
Figure B.8 – Object and ObjectType . 133
Figure B.9 – EventNotifier . 133
Figure B.10 – Variable and VariableType. 134
Figure B.11 – Method . 135
Figure B.12 – DataType . 135
Figure B.13 – View . 136
Figure C.1 – Example of a Reference connecting two Nodes . 138
Figure C.2 – Example of using a TypeDefinition inside a Node . 140
Figure C.3 – Example of exposing Attributes . 140
Figure C.4 – Example of exposing Properties inline . 141

Table 1 – NodeClass Table Conventions . 16
Table 2 – Well-Known Roles . 27
Table 3 – Example Roles . 28
Table 4 – Example Nodes . 29
Table 5 – Example Role Assignment . 29
Table 6 – Examples of Evaluating Access . 29
Table 7 – Base NodeClass . 36
Table 8 – RolePermissionType . 38
Table 9 – ReferenceType NodeClass . 40
Table 10 – View NodeClass . 43
Table 11 – Object NodeClass . 45
Table 12 – ObjectType NodeClass . 47
Table 13 – Variable NodeClass . 49
Table 14 – VariableType NodeClass . 55
Table 15 – Method NodeClass . 58
Table 16 – DataType NodeClass . 64
Table 17 – Overview of Attributes .
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