Reference

The IEC 62541 parts, explained

OPC UA is specified in numbered parts published by the OPC Foundation as PDFs behind registration. These pages explain what each part governs, whether you need to read it, and which practical traps trace back to it.

Three numbering schemes, one document. OPC 10000-4, IEC 62541-4 and "Part 4" are the same thing. Companion specifications use different series entirely (OPC 40001-1, OPC 40010-1, OPC 30270) and live under companion models. Note also that 1.05 is a release family: the fourth digit is an errata level, so "supports 1.05" is not a precise interoperability statement. Core is at 1.05.07.

Core parts 9

Part 1: Overview and ConceptsPart 1 is the map of the standard. It sets out what OPC UA is, defines the vocabulary every other part assumes, and shows how client/server and PubSub Part 2: Security ModelPart 2 defines the security architecture: the threats OPC UA is designed to resist, the split between application and user identity, and the mechanism Part 3: Address Space ModelPart 3 defines the meta-model: the eight NodeClasses, the attributes every node carries, typed references, the reference-type hierarchy, and the model Part 4: ServicesPart 4 defines every OPC UA service - the request and response structures, the parameters and the error behaviour - grouped into service sets from Dis Part 5: Information ModelPart 5 defines the standard nodes that exist in every server: namespace 0. That means the base type hierarchies, the Server object with its status, ca Part 6: MappingsPart 6 turns the abstract services of Part 4 into bytes. It defines the encodings - UA Binary, UA JSON and UA XML - the secure conversation and chunki Part 7: ProfilesPart 7 defines how OPC UA is subsetted for real products: conformance units group individual testable requirements, facets group conformance units, an Part 22: Base Network ModelWe have not confirmed this one. Our understanding is that Part 22 is the Base Network Model and that it is grouped with the core parts, but neither th Parts 23-27: Titles not confirmedThe core part numbering continues past 22, and we have not confirmed the titles of Parts 23 to 27. Rather than guess at them, this page exists to reco

Access type parts 5

Part 8: Data AccessPart 8 defines the VariableTypes that turn a raw number into a process value: AnalogItemType with its range and engineering unit, the discrete item ty Part 9: Alarms and ConditionsPart 9 defines the condition and alarm model: stateful conditions layered on the event system, the acknowledge and confirm lifecycle, shelving and sup Part 10: ProgramsPart 10 defines how a server exposes an invocable program - a batch, a recipe, a self-test - as a state machine a client can start, suspend, resume, h Part 11: Historical AccessPart 11 defines historical access: the HistoryRead and HistoryUpdate services with their raw, modified, at-time, processed and event variants, annotat Part 13: Aggregate FunctionsPart 13 defines the server-side aggregate functions - average, time average, minimum, maximum, count, delta, standard deviation, duration and percent

Utility parts 10

Part 12: Discovery and Global ServicesPart 12 defines how applications find each other and how their certificates are managed at scale: the Local Discovery Server, the Global Discovery Ser Part 14: PubSubPart 14 defines publish/subscribe: how a publisher packages selected values into datasets and emits them as network messages over UDP, Ethernet, MQTT Part 15: SafetyPart 15 defines OPC UA Safety: a functional-safety protocol carried inside ordinary OPC UA traffic. A safety provider and a safety consumer exchange a Part 16: State MachinesPart 16 defines how a state machine is represented in an address space: state and transition nodes, a CurrentState variable, a LastTransition variable Part 17: Alias NamesPart 17 defines a way to reach nodes by an external name - a plant designation, a KKS code, a legacy tag - instead of by browse path. A server publish Part 18: Role-Based SecurityPart 18 defines authorisation: named roles published in the address space, rules mapping authenticated identities to those roles, and per-node permiss Part 19: Dictionary ReferencePart 19 defines how a node points at an entry in an external semantic dictionary - an IRDI from the IEC Common Data Dictionary or eCl@ss, or a URI-ide Part 20: File TransferPart 20 defines how files move over OPC UA: a FileType object with open, read, write and seek methods, a directory type for creating and deleting file Part 21: Device OnboardingPart 21 defines how a device gets from factory state into a plant's trust domain without anyone hand-installing certificates. The device authenticates Scheduler: Scheduler information modelThe Scheduler information model is a released OPC UA model at version 1.05.02, published 2022-11-01, in the namespace http://opcfoundation.org/UA/Sche

UAFX parts 4

Part 80: UAFX Overview and ConceptsPart 80 is our understanding of the overview part of the UA Field eXchange series - the extension of OPC UA down to controller-to-controller and contr Part 81: UAFX Information ModelPart 81 defines the UAFX information models: the automation component model, the connection manager model and the data model. All three namespaces are Part 82: UAFX NetworkingPart 82 is our understanding of the networking part of the UAFX series - the layer covering how field-level traffic is carried and how the network is Part 83: UAFX Offline EngineeringPart 83 is our understanding of the offline-engineering part of the UAFX series - engineering a field-exchange system before the devices are on the ne

Domain parts 4

Part 100: Device Information Model (DI)Part 100 defines the device information model: a standard way to represent a device, its identification nameplates, its health, its parameters grouped Part 200: Industrial Automation (IA)Industrial Automation is a base-layer information model that sector companion specifications build on, in the namespace http://opcfoundation.org/UA/IA Part 210: Relative Spatial Location (RSL)Part 210 defines how to express where something is relative to something else: spatial objects, the attach points that connect them, and the position Part 211: Global Positioning (GPOS)Part 211 adds absolute geographic position to OPC UA: where a machine is on the earth, and which zone it is in. It builds directly on the relative spa

Last verified 7 September 2026 against OPC UA 1.05.07. OPC UA Connect is an educational resource and is not affiliated with the OPC Foundation.