IEC 62541-8-2025 PDF
Name in English:
St IEC 62541-8-2025
Name in Russian:
Ст IEC 62541-8-2025
Original standard IEC 62541-8-2025 in PDF full version. Additional info + preview on request
Full title and description
St IEC 62541-8-2025 — OPC unified architecture - Part 8: Data access. Defines the OPC UA information model and DA-specific VariableTypes, Properties, NodeClass/Attribute descriptions and behaviour needed to represent and exchange real‑time automation data in an OPC UA address space. This fourth edition updates and extends the previous edition (2020) with new modelling elements such as a Quantity Model and extended rules for ValuePrecision.
Abstract
IEC 62541-8:2025 specifies the Data Access (DA) information model for OPC UA: additional VariableTypes (e.g., DataItem, AnalogItem, ArrayItem and related subtypes), DA-specific Properties (EUInformation, Range, ValuePrecision, PercentDeadband, etc.), and guidance on DA-related use of OPC UA services. Annex A provides mapping rules from legacy OPC COM Data Access (DA) servers to the OPC UA DA model. The edition is a technical revision of the prior edition.
General information
- Status: Published / Current (4th edition).
- Publication date: 23 December 2025.
- Publisher: International Electrotechnical Commission (IEC).
- ICS / categories: 25.040.40, 35.100.05.
- Edition / version: 4.0 (fourth edition; cancels and replaces the 2020 edition).
- Number of pages: 92.
Scope
This part of IEC 62541 is limited to the Data Access information model for OPC UA: it defines DA-specific VariableTypes, Properties and Attribute semantics, prescribes how DA nodes are modelled in the OPC UA AddressSpace, and specifies DA-related usage of OPC UA services (reading, writing, subscriptions and deadband behaviour). It also includes normative mapping guidance for legacy OPC COM DA servers.
Key topics and requirements
- Formal DA information model: VariableType hierarchy for DataItemType, AnalogItemType, DiscreteItemType and array/multidimensional item types (ArrayItem, YArrayItem, XYArrayItem, ImageItem, CubeItem, NDimensionArrayItem).
- DA Properties and Attributes: EUInformation (engineering units), Range, ValuePrecision (expanded rules, including negative values and use with Duration/Decimal), PercentDeadband and semantics for quality/status codes.
- Quantity Model: new model for quantities and assigned units, alternative units and conversion rules (introduced in the 2025 edition).
- Support for array and complex-number data types to represent analyzer and multi-dimensional data.
- DA-specific service usage and interoperability rules, including guidance for mapping from OPC COM DA to OPC UA DA (Annex A).
These requirements affect server information modelling, client subscription/reading behaviour, and interoperability testing.
Typical use and users
Used in industrial automation, process control, SCADA/DCS integrations, device and instrument firmware that expose real‑time measurements, and gateways/historians/HMI applications that consume OPC UA DA. Typical users include control engineers, system integrators, device vendors, software developers, and test/certification labs working with OPC UA interoperability.
Related standards
Part of the IEC 62541 OPC UA series. Normative and closely related parts include IEC 62541-1 (Overview and Concepts), IEC 62541-3 (Address Space Model) and IEC 62541-4 (Services), which together define the address space and services used by the DA model; implementers should consult those parts when applying 62541-8.
Keywords
OPC UA, Data Access, DA, VariableType, DataItem, AnalogItem, EUInformation, ValuePrecision, Quantity Model, PercentDeadband, real‑time data, address space, industrial automation.
FAQ
Q: What is this standard?
A: IEC 62541-8:2025 is Part 8 of the OPC UA family specifying the Data Access information model used to represent and exchange real‑time automation data in OPC UA.
Q: What does it cover?
A: It covers DA-specific VariableTypes, Properties and Attribute semantics, rules for DA use of OPC UA services (read/write/subscriptions and deadband behaviour), array and complex-value support, and a Quantity Model plus mapping guidance from legacy OPC COM DA servers.
Q: Who typically uses it?
A: Control and automation engineers, device manufacturers implementing OPC UA servers, system integrators, HMI/historian developers, and test/certification bodies.
Q: Is it current or superseded?
A: It is the current (fourth) edition published 23 December 2025 and cancels and replaces the previous (2020) edition.
Q: Is it part of a series?
A: Yes — IEC 62541 is a multipart series (OPC UA). Part 8 works in conjunction with other parts such as Part 1 (Overview), Part 3 (Address Space Model) and Part 4 (Services).
Q: What are the key keywords?
A: OPC UA, Data Access (DA), VariableTypes, EUInformation, ValuePrecision, Quantity Model, PercentDeadband, real‑time automation data.