WG 8 - TC 65/SC 65E/WG 8

IEC 62541-100:2025 defines the information model associated with Devices. This document describes three models which build upon each other as follows:
• The (base) Device Model is intended to provide a unified view of devices and their hardware and software parts irrespective of the underlying device protocols.
• The Device Communication Model adds Network and Connection information elements so that communication topologies can be created.
• The Device Integration Host Model finally adds additional elements and rules required for host systems to manage integration for a complete system. It enables reflecting the topology of the automation system with the devices as well as the connecting communication networks.
This document also defines AddIns that can be used for the models in this document but also for models in other information models. They are:
• Locking model – a generic AddIn to control concurrent access,
• Software update model – an AddIn to manage software in a Device.
This second edition cancels and replaces the first edition published in 2015. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a a ComponentType that can be used to model any HW or SW element of a device has been defined and a SoftwareType has been added as subtype of ComponentType;
b the new OPC UA interface concept and defined interfaces for Nameplate, DeviceHealth, and SupportInfo has been added.
c) a new model for Software Update (Firmware Update) has been added;
d) a new entry point for documents where each document is represented by a FileType instance has been specified;
e) a model that provides information about the lifetime, related limits and semantic of the lifetime of things like tools, material or machines has been added.

IEC 62541-13:2025 is available as IEC 62541-13:2025 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 62541-13:2025 defines the information model associated with Aggregates. Programmatically produced aggregate examples are listed in Annex A. This third edition cancels and replaces the second edition published in 2020. This edition constitutes a technical revision.
This edition includes the following technical changes with respect to the previous edition:
a) Multiple fixes for the computation of aggregates
• The Raw status bit is always set for non-bad StatusCodes for the Start and End aggregates.
• Entries in the Interpolative examples Tables A2.2 Historian1, Historian2, and Historian3 have been changed from Good to Good, Raw status codes when the timestamp matches with the timestamp of the data source.
• Missing tables have been added for DurationInStateZero and DurationInStateNonZero.
• The value of zero has been removed for results with a StatusCode of bad.
• Data Type was listed as "Status Code" when it is "Double" for both Standard Deviation and both Variance Aggregates.
• Rounding Error in TimeAverage and TimeAverage2 have been corrected.
• The status codes have been corrected for the last two intervals and the value has been corrected in the last interval.
• The wording has been changed to be more consistent with the certification testing tool.
• UsedSlopedExtrapolation set to true for Historian2 and all examples locations needed new values or status' are modified.
• Values affected by percent good and percent bad have been updated.
• PercentGood/PercentBad are now accounted for in the calculation.
• TimeAverage uses SlopedInterpolation but the Time aggregate is incorrectly allowed to used Stepped Interpolation.
• Partial bit is now correctly calculated.
• Unclear sentence was removed.
• Examples have been moved to a CSV.
• The value and status code for Historian 3 have been updated.
• TimeAverage2 Historian1 now takes uncertain regions into account when calculating StatusCodes.
• TimeAverage2 Historian2 now takes uncertain regions into account when calculating StatusCodes.
• Total2 Historian1 now takes uncertain regions into account when calculating StatusCodes
• Total2 Historian2 now takes uncertain regions into account when calculating StatusCodes
• Maximum2 Historian1 now takes uncertain regions into account when calculating StatusCodes
• MaximumActualTime2 Historian1 now takes uncertain regions into account when calculating StatusCodes
• Minimum2 Historian1 now takes uncertain regions into account when calculating StatusCodes
• MinimumActualTime2 Historian1 now has the StatusCodes calculated while using the TreatUncertainAsBad flag.
• Range2 Historian1 now looks at TreatUncertainAsBad in the calculation of the StatusCodes.
• Clarifications have been made to the text defining how PercentGood/PercentBad are used. The table values and StatusCodes of the TimeAverage2 and Total2 aggregates have been corrected.

IEC 62541-7: 2025 specifies value and structure of Profiles in the OPC Unified Architecture.
OPC UA Profiles are used to segregate features with regard to testing of OPC UA products and the nature of the testing. The scope of this document includes defining functionality that can only be tested. The definition of actual TestCases is not within the scope of this document, but the general categories of TestCases are covered by this document.
Most OPC UA applications will conform to several, but not all of the Profiles.
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) Profiles and ConformanceUnits are not part of this document, but are solely managed in a public database as described in Clause 1.

IEC 62541-10:2025 is available as IEC 62541-10:2025 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 62541-10:2025 defines the Information Model associated with Programs in OPC Unified Architecture (OPC UA). This includes the description of the NodeClasses, standard Properties, Methods and Events and associated behaviour and information for Programs. The complete AddressSpace model including all NodeClasses and Attributes is specified in IEC 62541-3. The Services such as those used to invoke the Methods used to manage Programs are specified in IEC 62541-4. An example for a DomainDownload Program is defined in Annex A. 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:
- StateMachine table format has been aligned.

IEC 62541-4:2025 is available as IEC 62541-4:2025 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 62541-4:2025 defines the OPC Unified Architecture (OPC UA) Services. The Services defined are the collection of abstract Remote Procedure Calls (RPC) that are implemented by OPC UA Servers and called by OPC UA Clients. All interactions between OPC UA Clients and Servers occur via these Services. The defined Services are considered abstract because no particular RPC mechanism for implementation is defined in this document. IEC 62541‑6 specifies one or more concrete mappings supported for implementation. For example, one mapping in IEC 62541‑6 is to UA-TCP UA-SC UA-Binary. In that case the Services described in this document appear as OPC UA Binary encoded payload, secured with OPC UA Secure Conversation and transported via OPC UA TCP. Not all OPC UA Servers implement all of the defined Services. IEC 62541‑7 defines the Profiles that dictate which Services must be implemented in order to be compliant with a particular Profile. A BNF (Backus-Naur form) for browse path names is described in Annex A. 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 new definitions to Method Call Service to allow optional Method arguments;
b)addition of reference to SystemStatusChangeEventType for event monitored item error scenarios;
c) enhancement of the general description of how determining if a Certificate is trusted;
d) addition of support for ECC;
e) addition of revisedAggregateConfiguration to AggregateFilterResult structure;
f) addition of INVALID to the BrowseDirection enumeration data type;
g) addition of INVALID to the TimestampsToReturn enumeration data type;
h) addition of definitions that make sure the subscription functionality works if retransmission queues are optional;
i) addition of client checks has been added to be symmetric to the Server Certificate check has been added;
j) clarification that ‘local’ top level domain is not appended by server into certificate and not checked by client when returned from LDS-ME;
k) addition of a definition for expiration behaviour of IssuedIdentityTokens;
l) addition of status code Good_PasswordChangeRequired to ActivateSession;
m) restriction of AdditionalInfo to servers in debug mode;
n) addition of new status code Bad_ServerTooBusy;
o) addition of definition for cases where server certificate must be contained in GetEndpoints response.

IEC 62541-17:2025 provides a definition of AliasNames functionality. AliasNames provide a manner of configuring and exposing an alternate well-defined name for any Node in the system. This is analogous to the way domain names are used as an alias to IP addresses in IP networks. Like a DNS Server, an OPC UA Server that supports AliasNames provides a lookup Method that will translate an AliasName to a NodeId of the related Node on a Server. An aggregating Server can collect these AliasNames from multiple Servers and provide a lookup Method to allow Client applications to discover NodeIds on a system wide basis. An aggregating Server could also define AliasNames for Nodes in other Servers that do not support AliasNames. A GDS can be constructed that would automatically aggregate all AliasNames that are defined on any Server that has registered with the GDS. In this case, the GDS also provides the lookup mechanism for Clients at a well-known endpoint and address.

IEC 62541-16:2025 defines an Information Model. The Information Model describes the basic infrastructure to model state machines.
NOTE State Machines were dealt with in IEC 62541‑5:2020, Annex B. In newer versions of IEC 62541‑5 this Annex B was removed and replaced by this document

IEC 62541-19: 2025 defines an Information Model of the OPC Unified Architecture. The Information Model describes the basic infrastructure to reference from an OPC UA Information Model to external dictionaries like IEC Common Data Dictionary or ECLASS.

IEC 62541-18: 2025 defines an Information Model. The Information Model describes the basic infrastructure to model role-based security.
NOTE In the previous version, Role-Based Security was in IEC 62541-5:2020, Annex F.

IEC 62541-1:2020 presents the concepts and overview of the OPC Unified Architecture (OPC UA). Reading this document is helpful to understand the remaining parts of this multi-part document set. Each of the other parts of IEC 62451 is briefly explained along with a suggested reading order.

IEC 62541-2:2020 describes the OPC Unified Architecture (OPC UA) security model. It describes the security threats of the physical, hardware, and software environments in which OPC UA is expected to run. It describes how OPC UA relies upon other standards for security. It provides definition of common security terms that are used in this and other parts of the OPC UA specification. It gives an overview of the security features that are specified in other parts of the OPC UA specification. It references services, mappings, and Profiles that are specified normatively in other parts of the OPC UA Specification. It provides suggestions or best practice guidelines on implementing security. Any seeming ambiguity between this part and one of the other normative parts does not remove or reduce the requirement specified in the other normative part.

IEC 62541-4:2020 defines the OPC Unified Architecture (OPC UA) Services. The Services defined are the collection of abstract Remote Procedure Calls (RPC) that are implemented by OPC UA Servers and called by OPC UA Clients. All interactions between OPC UA Clients and Servers occur via these Services. The defined Services are considered abstract because no particular RPC mechanism for implementation is defined in this document. IEC 62541-6 specifies one or more concrete mappings supported for implementation. For example, one mapping in IEC 62541-6 is to XML Web Services. In that case the Services described in this document appear as the Web service methods in the WSDL contract. Not all OPC UA Servers will need to implement all of the defined Services. IEC 62541-7 defines the Profiles that dictate which Services need to be implemented in order to be compliant with a particular Profile This third edition cancels and replaces the second edition published in 2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) Added ability to resend all data of monitored items in a Subscription using the ResendData Method.
b) Added support for durable Subscriptions (lifetime of hours or days).
c) Added Register2 and FindServersOnNetwork Services to support network-wide discovery using capability filters.
d) Removed definition of software certificates. Will be defined in a future edition.
e) Extended and partially revised the redundancy definition. Added sub-range definitions for ServiceLevel and added more terms for redundancy.
f) Added a section on how to use Authorization Services to request user access tokens.
g) Added JSON Web Tokens (JWTs) as a new user token.
h) Added the concept of session-less service invocation.
i) Added a generic structure that allows passing any number of attributes to the AddNodes Service.
j) Added requirement to protect against user identity token attacks.
k) Added new EncryptedSecret format for user identity tokens.

IEC 62541-6:2020 specifies the OPC Unified Architecture (OPC UA) mapping between the security model described in IEC TR 62541-2, the abstract service definitions specified in IEC 62541-4, the data structures defined in IEC 62541-5 and the physical network protocols that can be used to implement the OPC UA specification. This third edition cancels and replaces the second edition published in 2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) Encodings:
• added JSON encoding for PubSub (non-reversible);
• added JSON encoding for Client/Server (reversible);
• added support for optional fields in structures;
• added support for Unions.
b) Transport mappings:
• added WebSocket secure connection – WSS;
• added support for reverse connectivity;
• added support for session-less service invocation in HTTPS.
c) Deprecated Transport (missing support on most platforms):
• SOAP/HTTP with WS-SecureConversation (all encodings).
d) Added mapping for JSON Web Token.
e) Added support for Unions to NodeSet Schema.
f) Added batch operations to add/delete nodes to/from NodeSet Schema.
g) Added support for multi-dimensional arrays outside of Variants.
h) Added binary representation for Decimal data types.
i) Added mapping for an OAuth2 Authorization Framework.

IEC 62541-5:2020 defines the Information Model of the OPC Unified Architecture. The Information Model describes standardized Nodes of a Server’s AddressSpace. These Nodes are standardized types as well as standardized instances used for diagnostics or as entry points to server-specific Nodes. Thus, the Information Model defines the AddressSpace of an empty OPC UA Server. However, it is not expected that all Servers will provide all of these Nodes.
This third edition cancels and replaces the second edition published in 2015. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) Added Annex F on User Authentication. Describes the Role Information Model that also allows configuration of Roles.
b) Added new data types: "Union", "Decimal", "OptionSet", "DateString", "TimeString", "DurationString", NormalizedString", "DecimalString", and "AudioDataType".
c) Added Method to request a state change in a Server.
d) Added Method to set Subscription to persistent mode.
e) Added Method to request resending of data from a Subscription.
f) Added concept allowing to temporarily create a file to write to or read from a server in C.4.
g) Added new Variable type to support Selection Lists.
h) Added optional properties to FiniteStateMachineType to expose currently available states and transitions.
i) Added UrisVersion Property to ServerType. This version information can be used for session-less service invocation.

IEC 62541-3:2020 defines the OPC Unified Architecture (OPC UA) AddressSpace and its Objects. This document is the OPC UA meta model on which OPC UA information models are based. This third edition cancels and replaces the second edition published in 2015. This edition includes the following significant technical changes with respect to the previous edition:
a) Added new improved approach for exposing structure definitions. An Attribute on the DataType Node now simply contains a binary description.
b) Added new flags for Variables to indicate atomicity when reading or writing.
c) Added Roles and Permissions to allow configuration of a role-based authorization.
d) Added new data types: “Union”, “Decimal”, “OptionSet”, “DateString”, “TimeString”, “DurationString”, NormalizedString”, “DecimalString”, and “AudioDataType”.
e) Added definition on how to use the ModellingRules OptionalPlaceHolder and MandatoryPlaceHolder for Methods.
f) Added optional Properties “MaxCharacters” and “MaxByteStringLength” to Variable Nodes.

IEC 62541-14:2020 defines the OPC Unified Architecture (OPC UA) PubSub communication model. It defines an OPC UA publish subscribe pattern which complements the client server pattern defined by the Services in IEC 62541-4. IEC TR 62541-1 gives an overview of the two models and their distinct uses.
PubSub allows the distribution of data and events from an OPC UA information source to interested observers inside a device network as well as in IT and analytics cloud systems.
This document consists of
• a general introduction of the PubSub concepts,
• a definition of the PubSub configuration parameters,
• mapping of PubSub concepts and configuration parameters to messages and transport protocols, and
• a PubSub configuration model.
Not all OPC UA Applications will need to implement all defined message and transport protocol mappings. IEC 62541-7 defines the Profile that dictates which mappings need to be implemented in order to be compliant with a particular Profile.

IEC 62541-10:2020 defines the information model associated with Programs in the OPC Unified Architecture. This includes the description of the NodeClasses, standard Properties, Methods and Events and associated behaviour and information for Programs. The complete Address Space model including all NodeClasses and Attributes is specified in IEC 62541-3. The Services such as those used to invoke the Methods used to manage Programs are specified in IEC 62541 4. This third edition cancels and replaces the second edition published in 2015. This edition includes several clarifications and in addition the following significant technical changes with respect to the previous edition:
a) Changed ProgramType to ProgramStateMachineType. This is in line with the NodeSet (and thus implementations). In ProgramDiagnosticDataType: changed the definition of lastInputArguments and lastOutputArguments and added two additional fields for the argument values. Also changed StatusResult into StatusCode. Created new version of the type to ProgramDiagnostic2DataType.
b) Changed Optional modelling rule to OptionalPlaceHolder for Program control Methods. Following the clarification in IEC 62541-3, this now allows subtypes (or instances) to add arguments.

IEC 62541-11:2020 is part of the OPC Unified Architecture standard series and defines the information model associated with Historical Access (HA). It particularly includes additional and complementary descriptions of the NodeClasses and Attributes needed for Historical Access, additional standard Properties, and other information and behaviour.
The complete AddressSpace Model including all NodeClasses and Attributes is specified in IEC 62541-3. The predefined Information Model is defined in IEC 62541-5. The Services to detect and access historical data and events, and description of the ExtensibleParameter types are specified in IEC 62541-4. This document includes functionality to compute and return Aggregates like minimum, maximum, average etc. The Information Model and the concrete working of Aggregates are defined in IEC 62541-13. This third edition cancels and replaces the second edition published in 2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) a new method for determining the first historical point has been added;
b) added clarifications on how to add, insert, modify, and delete annotations.

IEC 62541-7:2020 defines the OPC Unified Architecture (OPC UA) Profiles. The Profiles in this document are used to segregate features with regard to testing of OPC UA products and the nature of the testing (tool based or lab based). This includes the testing performed by the OPC Foundation provided OPC UA CTT (a self-test tool) and by the OPC Foundation provided Independent certification test labs. This could equally as well refer to test tools provided by another organization or a test lab provided by another organization. What is important is the concept of automated tool-based testing versus lab-based testing. The scope of this standard includes defining functionality that can only be tested in a lab and defining the grouping of functionality that is to be used when testing OPC UA products either in a lab or using automated tools. The definition of actual TestCases is not within the scope of this document, but the general categories of TestCases are within the scope of this document.
Most OPC UA applications will conform to several, but not all, of the Profiles.
This third edition cancels and replaces the second edition published in 2015. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) new functional Profiles:
• profiles for global discovery and global certificate management;
• profiles for global KeyCredential management and global access token management;
• facet for durable subscriptions;
• standard UA Client Profile;
• profiles for administration of user roles and permissions.
b) new transport Profiles:
• HTTPS with JSON encoding;
• secure WebSockets (WSS) with binary or JSON encoding;
• reverse connectivity.
c) new security Profiles:
• transportSecurity – TLS 1.2 with PFS (with perfect forward secrecy);
• securityPolicy [A] – Aes128-Sha256-RsaOaep (replaces Base128Rsa15);
• securityPolicy – Aes256-Sha256-RsaPss adds perfect forward secrecy for UA TCP);
• user Token JWT (Jason Web Token).
d) deprecated Security Profiles (due to broken algorithms):
• securityPolicy – Basic128Rsa15 (broken algorithm Sha1);
• securityPolicy – Basic256 (broken algorithm Sha1);
• transportSecurity – TLS 1.0 (broken algorithm RC4);
• transportSecurity – TLS 1.1 (broken algorithm RC4).
e) deprecated Transport (missing support on most platforms):
• SOAP/HTTP with WS-SecureConversation (all encodings).

IEC 62541-8:2020 is part of the overall OPC Unified Architecture (OPC UA) standard series and defines the information model associated with Data Access (DA). It particularly includes additional VariableTypes and complementary descriptions of the NodeClasses and Attributes needed for Data Access, additional Properties, and other information and behaviour.
The complete address space model, including all NodeClasses and Attributes is specified in IEC 62541-3. The services to detect and access data are specified in IEC 62541-4.
This third edition cancels and replaces the second edition published in 2015. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) added new VariableTypes for AnalogItems;
b) added an Annex that specifies a recommended mapping of OPC UA Dataccess to OPC COM DataAccess;
c) changed the ambiguous description of "Bad_NotConnected";
d) updated description for EUInformation to refer to latest revision of UNCEFACT units.

IEC 62541-9:2020 specifies the representation of Alarms and Conditions in the OPC Unified Architecture. Included is the Information Model representation of Alarms and Conditions in the OPC UA address space. Other aspects of alarm systems such as alarm philosophy, life cycle, alarm response times, alarm types and many other details are captured in documents such as IEC 62682 and ISA 18.2. The Alarms and Conditions Information Model in this specification is designed in accordance with IEC 62682 and ISA 18.2.
This third edition cancels and replaces the second edition published in 2015. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) added optional engineering units to the definition of RateOfChange alarms;
b) to fulfill the IEC 62682 model, the following elements have been added:
- AlarmConditionType States: Suppression, Silence, OutOfService, Latched;
- AlarmConditionType Properties: OnDelay, OffDelay, FirstInGroup, ReAlarmTime;
- New alarm types: DiscrepencyAlarm, DeviationAlarm, InstrumentDiagnosticAlarm, SystemDiagnosticAlarm.
c) added Annex that specifies how the concepts of this OPC UA part maps to IEC 62682 and ISA 18.2;
d) added new ConditionClasses: Safety, HighlyManaged, Statistical, Testing, Training;
e) added CertificateExpiration AlarmType;
f) added Alarm Metrics model.

IEC 62541-12:2020 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 Authorization Services.

IEC 62541-13:2020 is part of the overall OPC Unified Architecture specification series and defines the information model associated with Aggregates. This second edition cancels and replaces the first edition of IEC 62541-13, published in 2015. No technical changes but numerous clarifications. Also some corrections to the examples.

IEC TR 62541-2:2016(E) is a Technical Report and describes the OPC unified architecture (OPC UA) security model. It describes the security threats of the physical, hardware, and software environments in which OPC UA is expected to run. It describes how OPC UA relies upon other standards for security. It provides definition of common security terms that are used in this and other parts of the OPC UA specification. It gives an overview of the security features that are specified in other parts of the OPC UA specification. It references services, mappings, and Profiles that are specified normatively in other parts of this multi-part specification. It provides suggestions or best practice guidelines on implementing security. Any seeming ambiguity between this part of IEC 62541 and one of the normative parts of IEC 62541 does not remove or reduce the requirement specified in the normative part. This second edition cancels and replaces the first edition of IEC TR 62541-2, published in 2010. This second edition includes no technical changes with respect to the first edition but a number of clarifications and additional text for completeness.

IEC TR 62541-1:2016(E) is a Technical Report and presents the concepts and overview of the OPC Unified Architecture (OPC UA). Reading this document is helpful to understand the remaining parts of this multi-part document set. Each of the other parts is briefly explained along with a suggested reading order. This second edition cancels and replaces the first edition of IEC TR 62541-1, published in 2010. This edition includes no technical changes with respect to the previous edition but includes updates to reflect changes or additions in normative parts of IEC 62541.

IEC 62451-8:2015 is part of the overall OPC Unified Architecture (OPC UA) standard series and defines the information model associated with Data Access (DA). It particularly includes additional VariableTypes and complementary descriptions of the NodeClasses and Attributes needed for Data Access, additional Properties, and other information and behaviour. This second edition cancels and replaces the first edition published in 2011 and constitutes a technical revision. This edition includes the following changes:
- Clarified that deadband has to be between 0.0 and 100.0. Violations result in error Bad_DeadbandFilterInvalid;
- Added VariableTypes handling ArrayItems and DataTypes supporting this, including complex number types.

IEC 62541-9:2015 specifies the representation of Alarms and Conditions in the OPC Unified Architecture. Included is the Information Model representation of Alarms and Conditions in the OPC UA address space. This second edition cancels and replaces the first edition published in 2012 and constitutes a technical revision. This edition includes the following changes:
- added section to describe expect behaviour for A&C servers and the associated information model in the case of redundancy or communication faults;
- changed the DialogConditionType to be not abstract since it is expect that instance of this type will exist in the system;
- updated ConditionRefresh Method to allow the use of the well know NodeIds associated with the types for the MethodId and ConditionId instead of requiring the call to use only the MethodId and ConditionId that is part of an instance;
- Fixed ExclusiveLimitStateMachineType and ShelvedStatemachineType to be sub-types of FinitStateMachineType not StateMachineType.

IEC 62541-6:2015 specifies the OPC Unified Architecture (OPC UA) mapping between the security model described in IEC TR 62541-2, the abstract service definitions, described in IEC 62541-4, the data structures defined in IEC 62541-5 and the physical network protocols that can be used to implement the OPC UA specification. This second edition cancels and replaces the first edition published in 2011 and constitutes a technical revision. This edition includes the following changes:
- A new HTTPS transport has been defined;
- Added an additional padding byte to handle asymmetric key sizes larger than 2048 bits. Fixed errors in SOAP action URIs;
- Needed a standard way to serialize nodes in an address space. Added the UANodeSet schema defined in Annex F.

IEC 62541-4:2015 defines the OPC Unified Architecture (OPC UA) Services. The Services described are the collection of abstract Remote Procedure Calls (RPC) that are implemented by OPC UA Servers and called by OPC UA Clients. This second edition cancels and replaces the first edition published in 2011. It constitutes a technical revision. It includes the following changes:
- Update for 6.4 Redundancy.
- Clarifications for Publish and Reconnect scenarios.
- Handling of MonitoredItem changes in short network interruption scenarios.
- Update for 6.1.3 Determining if a Certificate is Trusted.
- Revised definition of parameters semaphoreFile and isOnline in Service RegisterServer.
- Services ModifySubscription and ModifyMonitoredItems.

IEC 62541-11:2015 is part of the overall OPC Unified Architecture standard series and defines the information model associated with Historical Access (HA). It particularly includes additional and complementary descriptions of the NodeClasses and Attributes needed for Historical Access, additional standard Properties, and other information and behaviour. It also includes functionality to compute and return Aggregates like minimum, maximum, average etc. The Information Model and the concrete working of Aggregates are defined in IEC 62541-13.

IEC 62541-7:2015 describes the OPC Unified Architecture (OPC UA) Profiles. The Profiles in this document are used to segregate features with regard to testing of OPC UA products and the nature of the testing (tool based or lab based). This includes the testing performed by the OPC Foundation provided OPC UA CTT (a self-test tool) and by the OPC Foundation provided Independent certification test labs. It is also defining functionality that can only be tested in an a lab and defining the grouping of functionality that is to be used when testing OPC UA products either in a lab or using automated tools. This second edition cancels and replaces the first edition published in 2012 and constitutes a technical revision. It includes the following changes:
- Added a large number of new Facets to cover additional functional areas of OPC UA. Most significantly:
- Facets for Historical Access;
- Facets for Aggregates;
- Facets for HTTPs;
- New Security Facets;
- New User Token Facet that supports anonymous access;
- Best Practice Facets as well as New Security Policy for asymmetric key length > 2048.

IEC 62541-3:2015 describes the OPC Unified Architecture (OPC UA) AddressSpace and its Objects. It is the OPC UA meta model on which OPC UA information models are based. This second edition cancels and replaces the first edition published in 2010 and constitutes a technical revision. It includes the following changes:
- Added rules for subtyping enumerations;
- Added Property EnumValues;
- Added Property ValueAsText;
- Added EventType SystemStatusChangeEventType;
- Added Properties MaxArrayLength and MaxStringLength;
- Removed the concept of ModelParent;
- Added EventType ProgressEventType;
- Stated that it is allowed to use TAI in all places where UTC time is used;
- Added Property EngineeringUnits;
- Added ModellingRules OptionalPlaceholder and MandatoryPlaceholder.

IEC 62541-13:2015 is part of the overall OPC Unified Architecture specification series and defines the information model associated with Aggregates.

IEC 62541-100:2015 is an extension of the overall OPC Unified Architecture standard series and defines the information model associated with Devices. This part of IEC 62541 describes three models which build upon each other:
- the (base) Device Model intended to provide a unified view of devices;
- the Device Communication Model which adds Network and Connection information elements so that communication topologies can be created;
- the Device Integration Host Model finally which adds additional elements and rules required for host systems to manage integration for a complete system. It allows reflecting the topology of the automation system with the devices as well as the connecting communication networks.

IEC 62541-5.2015 defines the Information Model of the OPC Unified Architecture. The Information Model describes standardised Nodes of a Server's AddressSpace. These Nodes are standardised types as well as standardised instances used for diagnostics or as entry points to server-specific Nodes. This second edition cancels and replaces the first edition published in 2011 and constitutes a technical revision. This edition includes the following changes:
- Defined ProgressEventType;
- Defined DataType called BitFieldMaskDataType;
- Delete Property SamplingRateCount in ServerDiagnosticSummaryDataType;
- Added the Property "EffectiveTransitionTime" to TransitionVariableType;
- Introduced VariableType OptionSetType;
- Added a new EventType called SystemStatusChangeEventType;
- Added properties to ServerCapabilitiesType. Added an object for operation limits. Added type OperationLimitsType containing that information;
- Added SecureChannelId to AuditActivateSessionEventType;
- Added normative Annex C defining FileType and Methods;
- Added a Method GetMonitoredItems on ServerType;
- Removed the concept of ModelParent. Added meta data for namespaces in ServerType and created types for managing that. Added representations for ModellingRules OptionalPlaceholder and MandatoryPlaceholder;
- Added new types NonTransparentNetworkRedundancyType, NetworkGroupDataType and EndpointUrlListDataType.

IEC 62541-10:2015 is part of the overall OPC Unified Architecture (OPC UA) standard series and defines the information model associated with Programs. This includes the description of the NodeClasses, standard Properties, Methods and Events and associated behaviour and information for Programs. This second edition cancels and replaces the first edition published in 2012 and constitutes a technical revision. It includes the following technical changes:
- Based on NIST review, security considerations have been included as 4.2.2;
- Fixed the definition of the Program Diagnostic Type into a data type (5.2.8) and added missing data type for the Program Diagnostic Variable in the ProgramType in Table 5;
- Corrected the BrowseName of the audit events for Program Transitions in Table 7.

IEC 62541-7:2012 describes the OPC Unified Architecture Profiles. The Profiles are used to describe the functionality that an OPC UA Server exposes or that an OPC UA Client consumes. The details of the functionality are specified in other parts of IEC 62541.

IEC 62541-9:2012 specifies the representation of Alarms and conditions in the OPC unified architecture. Included is the Information Model representation of Alarms and conditions in the OPC UA address space.

IEC 62541-10:2012 specifies the standard representation of Programs as part of the OPC Unified Architecture and its defined information model. This includes the description of the NodeClasses, standard Properties, Methods and Events and associated behaviour and information for Programs.

IEC 62541-4:2011 defines the OPC Unified Architecture (OPC UA) Services. The Services described are the collection of abstract Remote Procedure Calls (RPC) that are implemented by OPC UA Servers and called by OPC UA Clients. All interactions between OPC UA Clients and Servers occur via these Services. The defined Services are considered abstract because no particular RPC mechanism for implementation is defined in this part of IEC 62541. IEC 62541-6 specifies one or more concrete mappings supported for implementation. For example, one mapping in IEC 62541-6 is to XML Web Services. In that case the Services described in this part of IEC 62541 appear as the Web service methods in the WSDL contract.

IEC 62541-6:2011 specifies the OPC Unified Architecture (OPC UA) mapping between the security model described in IEC 62541-2, the abstract service definitions, described in IEC 62541-4, the data structures defined in IEC 62541-5 and the physical network protocols that can be used to implement the OPC UA specification.

IEC 62541-8:2011 is part of the overall OPC Unified Architecture (OPC UA) standard series and defines the information model associated with Data Access (DA). It particularly includes additional VariableTypes and complemental descriptions of the NodeClasses and Attributes needed for Data Access, additional Properties and other information and behaviour.

IEC 62541-5:2011 defines the Information Model of the OPC Unified Architecture (OPC UA). The Information Model describes standardised Nodes of a server's AddressSpace. These Nodes are standardised types as well as standardised instances used for diagnostics or as entry points to server specific Nodes. Thus, the Information Model defines the AddressSpace of an empty OPC UA server. However, it is not expected that all servers will provide all of these Nodes.

IEC 62541-3:2012 describes the OPC Unified Architecture (OPC UA) AddressSpace and its Objects. This Part is the OPC UA meta model on which OPC UA information models are based. This bilingual version (2012-10) corresponds to the monolingual English version, published in 2010-07.

IEC/TR 62541-1:2010(E) presents the concepts and overview of the Unified Architecture (OPC UA) specification produced by the OPC Foundation. Reading this report enables the reader to understand the series of IEC 62541 standards. Each of the other parts is briefly explained along with a suggested reading order.

IEC/TR 62541-2:2010(E) describes the OPC Unified Architecture (OPC UA) security model. It describes the security threats of the physical, hardware and software environments in which OPC UA is expected to run. It describes how OPC UA relies upon other standards for security. It gives an overview of the security features that are specified in other parts of the OPC UA specification. It references services, mappings, and profiles that are specified normatively in other parts of this series of standards. It is directed to readers who will develop OPC UA client or server applications or implement the OPC UA services layer.