SIST EN IEC 62541-11:2026

SLOVENSKI STANDARD
01-maj-2026
Enotna arhitektura OPC - 11. del: Zgodovinski dostop (IEC 62541-11:2025)
OPC Unified Architecture - Part 11: Historical Access (IEC 62541-11:2025)
OPC Unified Architecture - Teil 11: Zugang zu historischen Daten (IEC 62541-11:2025)
Architecture unifiée OPC - Partie 11: Accès à l'historique (IEC 62541-11:2025)
Ta slovenski standard je istoveten z: EN IEC 62541-11:2026
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
35.240.50 Uporabniške rešitve IT v IT applications in industry
industriji
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 62541-11

NORME EUROPÉENNE
EUROPÄISCHE NORM February 2026
ICS 25.040.40; 35.100.05 Supersedes EN IEC 62541-11:2020
English Version
OPC Unified Architecture - Part 11: Historical Access
(IEC 62541-11:2025)
Architecture unifiée OPC - Partie 11: Accès à l'historique OPC Unified Architecture - Teil 11: Zugang zu historischen
(IEC 62541-11:2025) Daten
(IEC 62541-11:2025)
This European Standard was approved by CENELEC on 2026-01-27. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62541-11:2026 E

European foreword
The text of document 65E/1058/CDV, future edition 3 of IEC 62541-11, prepared by SC 65E "Devices
and integration in enterprise systems" of IEC/TC 65 "Industrial-process measurement, control and
automation" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2027-02-28
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2029-02-28
document have to be withdrawn
This document supersedes EN IEC 62541-11:2020 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a standardization request addressed to CENELEC by the
European Commission. The Standing Committee of the EFTA States subsequently approves these
requests for its Member States.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 62541-11:2025 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 62541-6 NOTE Approved as EN IEC 62541-6
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 62541-1 - OPC Unified Architecture - Part 1: EN IEC 62541-1 -
Overview and concepts
IEC 62541-3 - OPC Unified Architecture - Part 3: Address EN IEC 62541-3 -
Space Model
IEC 62541-4 - OPC unified architecture - Part 4: Services EN IEC 62541-4 -
IEC 62541-5 - OPC Unified architecture - Part 5: EN IEC 62541-5 -
Information Model
IEC 62541-7 - OPC Unified Architecture - Part 7: Profiles EN IEC 62541-7 -
IEC 62541-8 - OPC unified architecture - Part 8: Data EN IEC 62541-8 -
access
IEC 62541-13 - OPC Unified Architecture - Part 13: EN IEC 62541-13 -
Aggregates
IEC 62541-11 ®
Edition 3.0 2025-12
INTERNATIONAL
STANDARD
OPC unified architecture -
Part 11: Historical Access
ICS 25.040.40; 35.100.05 ISBN 978-2-8327-0846-0

IEC 62541-11:2025-12(en)
IEC 62541-11:2025 © IEC 2025
CONTENTS
FOREWORD. 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviations . 7
3.1 Terms and definitions . 7
3.2 Abbreviated terms . 9
4 Concepts . 10
4.1 General . 10
4.2 Data architecture. 10
4.3 Historians and interruption of data collection . 11
4.4 Modification of Historical Data/Events . 11
4.5 Timestamps . 12
4.6 Bounding Values and time domain . 12
4.7 Changes in AddressSpace over time . 14
5 Historical Information Model . 15
5.1 HistoricalNodes . 15
5.1.1 General . 15
5.1.2 Annotations Property . 15
5.2 HistoricalDataNodes . 16
5.2.1 General . 16
5.2.2 HistoricalDataConfigurationType . 16
5.2.3 Attributes . 18
5.2.4 Historical Data Configuration Object . 18
5.3 References . 19
5.3.1 Overview . 19
5.3.2 HasHistoricalConfiguration ReferenceType . 19
5.3.3 HasCurrentData ReferenceType . 20
5.3.4 HasCurrentEvent ReferenceType . 20
5.4 HistoricalEventNodes . 21
5.4.1 General . 21
5.4.2 HistoricalEventFilter Property . 21
5.4.3 HistoricalEventConfigurationType . 22
5.4.4 HistoricalEventNode Attributes . 22
5.5 External History sources. 23
5.5.1 General . 23
5.5.2 External Historical Event Node . 23
5.6 Example Object Models in Historian Servers (informative) . 24
5.6.1 Overview . 24
5.6.2 HistoricalDataNodes Address Space Model . 24
5.6.3 Historical data . 25
5.6.4 HistoricalEventNodes Address Space Model . 26
5.6.5 Historical Events . 27
5.7 Exposing supported functions and capabilities . 28
5.7.1 General . 28
5.7.2 HistoryServerCapabilitiesType . 29
5.7.3 Default configuration . 32
5.8 Historical Audit Events . 33
IEC 62541-11:2025 © IEC 2025
5.8.1 General . 33
5.8.2 AuditHistoryEventUpdateEventType . 33
5.8.3 AuditHistoryValueUpdateEventType . 34
5.8.4 AuditHistoryAnnotationUpdateEventType . 34
5.8.5 AuditHistoryDeleteEventType . 35
5.8.6 AuditHistoryRawModifyDeleteEventType . 36
5.8.7 AuditHistoryAtTimeDeleteEventType . 37
5.8.8 AuditHistoryEventDeleteEventType . 37
5.8.9 AuditHistoryConfigurationChangeEventType . 38
5.8.10 AuditHistoryBulkInsertEventType . 38
6 Historical Access specific usage of Services . 39
6.1 General . 39
6.2 Historical Nodes StatusCodes . 40
6.2.1 Overview . 40
6.2.2 Operation level result codes . 40
6.2.3 Semantics changed . 42
6.3 Continuation Points . 42
6.4 Arrays, index ranges and substrings . 42
6.5 HistoryReadDetails parameters . 44
6.5.1 Overview . 44
6.5.2 ReadEventDetails structure . 46
6.5.3 ReadRawModifiedDetails structure . 49
6.5.4 ReadProcessedDetails structure . 51
6.5.5 ReadAtTimeDetails structure . 53
6.5.6 ReadAnnotationDataDetails structure . 54
6.6 HistoryData parameters returned . 55
6.6.1 Overview . 55
6.6.2 HistoryData type . 55
6.6.3 HistoryModifiedData type . 55
6.6.4 HistoryEvent DataType . 56
6.6.5 HistoryModifiedEvent DataType . 56
6.6.6 Annotation DataType . 57
6.7 HistoryUpdateType Enumeration . 58
6.8 PerformUpdateType Enumeration . 58
6.9 HistoryUpdateDetails parameter . 59
6.9.1 Overview . 59
6.9.2 UpdateDataDetails structure . 61
6.9.3 UpdateStructureDataDetails structure . 63
6.9.4 UpdateEventDetails structure . 64
6.9.5 DeleteRawModifiedDetails structure . 67
6.9.6 DeleteAtTimeDetails structure . 68
6.9.7 DeleteEventDetails structure . 68
Annex A (informative) Client conventions . 70
A.1 How clients can request timestamps . 70
A.2 Determining the first or last historical data point . 71
Bibliography . 73

Figure 1 – Possible OPC UA Server supporting Historical Access . 10
IEC 62541-11:2025 © IEC 2025
Figure 2 – ReferenceType hierarchy . 19
Figure 3 – Historical Variable with Historical Data Configuration and Annotations . 25
Figure 4 – Historical Variable with Historical Data Configuration and Annotations . 26
Figure 5 – Representation of an Event with History in the AddressSpace . 27
Figure 6 – Event History configuration example . 28
Figure 7 – Server and HistoryServer Capabilities . 29
Figure 8 – History Array example . 43
Figure 9 – Historian Array Illustration 2 . 44

Table 1 – Bounding Value examples . 13
Table 2 – Annotations Property . 15
Table 3 – HistoricalDataConfigurationType definition . 16
Table 4 – ExceptionDeviationFormat Items . 18
Table 5 – ExceptionDeviationFormat definition . 18
Table 6 – Historical Access configuration definition . 19
Table 7 – HasHistoricalConfiguration ReferenceType . 20
Table 8 – HasCurrentData ReferenceType . 20
Table 9 – HasCurrentEvent ReferenceType . 21
Table 10 – Standard Historical Events Properties . 22
Table 11 – HistoricalEventConfigurationType definition . 22
Table 12 – HistoricalExternalEventSourceType definition . 23
Table 13 – HistoryServerCapabilitiesType Definition . 30
Table 14 – DefaultHAConfiguration definition . 32
Table 15 – DefaultHEConfiguration definition . 32
Table 16 – AuditHistoryEventUpdateEventType definition . 33
Table 17 – AuditHistoryValueUpdateEventType definition . 34
Table 18 – AuditHistoryAnnotationUpdateEventType definition . 35
Table 19 – AuditHistoryDeleteEventType definition . 36
Table 20 – AuditHistoryRawModifyDeleteEventType definition . 36
Table 21 – AuditHistoryAtTimeDeleteEventType definition . 37
Table 22 – AuditHistoryEventDeleteEventType definition . 38
Table 23 – AuditHistoryConfigurationChangeEventType definition . 38
Table 24 – AuditHistoryBulkInsertEventType definition . 39
Table 25 – Bad operation level result codes . 40
Table 26 – Good operation level result codes . 41
Table 27 – HistoryReadDetails parameter Symbolic Names . 45
Table 28 – HistoryReadDetails definition . 46
Table 29 – ReadEventDetails Structure . 46
Table 30 – ReadEventDetails definition . 46
Table 31 – ReadEventDetails2 Structure . 47
Table 32 – ReadEventDetails2 definition . 48
Table 33 – ReadRawModifiedDetails structure . 49
Table 34 – ReadRawModifiedDetails definition . 49
IEC 62541-11:2025 © IEC 2025
Table 35 – ReadProcessedDetails structure . 51
Table 36 – ReadProcessedDetails definition . 52
Table 37 – ReadAtTimeDetails structure . 53
Table 38 – ReadAtTimeDetails definition . 53
Table 39 – ReadAnnotationDataDetails Structure . 54
Table 40 – ReadAnnotationDataDetails definition . 54
Table 41 – HistoryData structure . 55
Table 42 – HistoryData definition . 55
Table 43 – HistoryModifiedData structure . 55
Table 44 – HistoryModifiedData definition . 56
Table 45 – HistoryEvent structure . 56
Table 46 – HistoryEvent definition . 56
Table 47 – HistoryModifiedEvent structure. 57
Table 48 – HistoryModifiedEvent definition . 57
Table 49 – Annotation Structure . 57
Table 50 – Annotation definition . 58
Table 51 – HistoryUpdateType Items . 58
Table 52 – HistoryUpdateType definition . 58
Table 53 – PerformUpdateType Items . 58
Table 54 – PerformUpdateType definition . 59
Table 55 – HistoryUpdateDetails parameter Symbolic Names . 60
Table 56 – HistoryUpdateDetails Structure . 61
Table 57 – HistoryUpdateDetails definition . 61
Table 58 – UpdateDataDetails Structure . 61
Table 59 – UpdateDataDetails definition . 62
Table 60 – UpdateStructureDataDetails Structure . 63
Table 61 – UpdateStructureDataDetails definition . 63
Table 62 – UpdateEventDetails Structure . 65
Table 63 – UpdateEventDetails definition . 65
Table 64 – DeleteRawModifiedDetails Structure . 67
Table 65 – DeleteRawModifiedDetails definition . 67
Table 66 – DeleteAtTimeDetails Structure . 68
Table 67 – DeleteAtTimeDetails definition . 68
Table 68 – DeleteEventDetails Structure . 68
Table 69 – DeleteEventDetails definition . 69
Table A.1 – Time keyword definitions . 71
Table A.2 – Time offset definitions . 71

IEC 62541-11:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPC unified architecture -
Part 11: Historical Access
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 62541-11 has been prepared by subcommittee 65E: Devices and integration in enterprise
systems, of IEC technical committee 65: Industrial-process measurement, control and
automation. It is an International Standard.
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) a functionality has been added to support retrieving of modified events;
b) an Event has been added to indicate when a backfill occurred;
c) a new ReferenceType that can be used to indicate an external node has been defined;
d) the text has been improved to better explain the concept of annotation and remove
conflicting explanations;
IEC 62541-11:2025 © IEC 2025
e) a default historian configuration (and where to find it) has been defined;
f) HistoricalEventConfigurationType, which provides general configuration information about
the historical Event storage, has been added;
g) the text has been updated and optional fields have been added to HA configuration object
to allow configuration to be defined for periodic data collection, not just for exception-based
collection;
h) an ObjectType that can be used for external event collection has been provided as well as
an example how historians can be configured.
The text of this International Standard is based on the following documents:
Draft Report on voting
65E/1058/CDV 65E/1096/RVC
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
Throughout this document and the other parts of the IEC 62541 series, certain document
conventions are used:
Italics are used to denote a defined term or definition that appears in the "Terms and definitions"
clause in one of the parts of the IEC 62541 series.
Italics are also used to denote the name of a service input or output parameter or the name of
a structure or element of a structure that are usually defined in tables.
The italicized terms and names are, with a few exceptions, written in camel-case (the practice
of writing compound words or phrases in which the elements are joined without spaces, with
each element's initial letter capitalized within the compound). For example, the defined term is
AddressSpace instead of Address Space. This makes it easier to understand that there is a
single definition for AddressSpace, not separate definitions for Address and Space.
A list of all parts in the IEC 62541 series, published under the general title OPC Unified
Architecture, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
– reconfirmed,
– withdrawn, or
– revised.
IEC 62541-11:2025 © IEC 2025
1 Scope
This part of IEC 62541 belongs to the OPC Unified Architecture standards 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.
Conventions for Historical Access Clients are informatively provided in Annex A.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 62541-1, OPC Unified Architecture - Part 1: Overview and Concepts
IEC 62541-3, OPC Unified Architecture - Part 3: Address Space Model
IEC 62541-4, OPC Unified Architecture - Part 4: Services
IEC 62541-5, OPC Unified Architecture - Part 5: Information Model
IEC 62541-7, OPC Unified Architecture - Part 7: Profiles
IEC 62541-8, OPC Unified Architecture - Part 8: Data Access
IEC 62541-13, OPC Unified Architecture - Part 13: Aggregates
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62541-1,
IEC 62541-3, IEC 62541-4, IEC 62541-13 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
IEC 62541-11:2025 © IEC 2025
3.1.1
Annotation
metadata associated with an item at a given instance in time
Note 1 to entry: An Annotation is metadata that is associated with an item at a given instance in time.
3.1.2
BoundingValues
values associated with the starting and ending time
Note 1 to entry: BoundingValues are the values that are associated with the starting and ending time of a
ProcessingInterval specified when reading from the historian. BoundingValues can be required by Clients to
determine the starting and ending values when requesting RawData over a time range. If a RawData value exists at
the start or end point, it is considered the bounding value even though it is part of the data request. If no RawData
value exists at the start or end point, then the Server will determine the boundary value, which possibly requires data
from a data point outside of the requested range. See 4.6 for details on using BoundingValues.
3.1.3
Historian
application storing time series data and/or time series events
3.1.4
HistoricalNode
Object, Variable, Property or View in the AddressSpace where a Client can access historical
data or Events
Note 1 to entry: A HistoricalNode is a term used in this document to represent any Object, Variable, Property or
View in the AddressSpace for which a Client can read and/or update historical data or Events. The terms
"HistoricalNodes's history" or "history of a HistoricalNodes" will refer to the time series data or Events stored for this
HistoricalNode. The term HistoricalNode refers to both HistoricalDataNodes and HistoricalEventNodes.
3.1.5
HistoricalDataNode
Variable or Property in the AddressSpace where a Client can access historical data
Note 1 to entry: A HistoricalDataNode represents any Variable or Property in the AddressSpace for which a Client
can read and/or update historical data. "HistoricalDataNode history" or "history of a HistoricalDataNode" refers to
the time series data stored for this HistoricalNode. Examples of such data are:
• device data (like temperature sensors)
• calculated data
• status information (open/closed, moving)
• dynamically changing system data (like stock quotes)
• diagnostic data
The term HistoricalDataNodes is used when referencing aspects of the standard that apply to accessing historical
data only.
3.1.6
HistoricalEventNode
Object or View in the AddressSpace for which a Client can access historical Events
Note 1 to entry: "HistoricalEventNode's history" or "history of a HistoricalEventNode" refers to the time series
Events stored in some historical system. Examples of such data are:
• Notifications
• system Alarms
• operator action Events
• system triggers (such as new orders to be processed)
The term HistoricalEventNode is used when referencing aspects of the standard that apply to accessing historical
Events only.
IEC 62541-11:2025 © IEC 2025
3.1.7
ModifiedValues
HistoricalDataNode's value that has been changed (or manually inserted or deleted) after it was
stored in the historian
Note 1 to entry: For some Servers, a lab data entry value is not a modified value, but if a user corrects a lab value,
the original value would be considered a modified value, and would be returned during a request for ModifiedValues.
Also manually inserting a value that was missed by a standard collection system can be considered a modified value.
Unless specified otherwise, all historical Services operate on the current, or most recent, value for the specified
HistoricalDataNode at the specified timestamp. Requests for ModifiedValues are used to access values that have
been superseded, deleted or inserted. It is up to a system to determine what is considered a modified value.
Whenever a Server has modified data available for an entry in the historical collection it shall set the ExtraData bit
in the StatusCode.
3.1.8
RawData
data that is stored within the historian for a HistoricalDataNode
Note 1 to entry: The data can be all data collected for the DataValue or it can be some subset of the data depending
on the historian and the storage rules invoked when the item's values were saved.
3.1.9
StartTime/EndTime
bounds of a history request which define the time domain
Note 1 to entry: For all requests, a value falling at the end time of the time domain is not included in the domain,
so that requests made for successive, contiguous time domains will include every value in the historical collection
exactly once.
3.1.10
TimeDomain
interval of time covered by a particular request, or response
Note 1 to entry: In general, if the start time is earlier than or the same as the end time, the time domain is considered
to begin at the start time and end just before the end time; if the end time is earlier than the start time, the time
domain still begins at the start time and ends just before the end time, with time "running backward" for the particular
request and response. In both cases, any value which falls exactly at the end time of the TimeDomain is not included
in the TimeDomain. See the examples in 4.6. BoundingValues effect the time domain as described in 4.6.
All timestamps which can legally be represented in a UtcTime DataType are valid timestamps, and the Server has
the choice to, or not to return an invalid argument result code due to the timestamp being outside of the range for
which the Server has data. See IEC 62541-3 for a description of the range and granularity of this DataType. Servers
are expected to handle out-of-bounds timestamps gracefully and return the proper StatusCodes to the Client.
3.1.11
StructuredHistoryData
structured data stored in a history collection where parts of the structure are used to uniquely
identify the data within the data collection
Note 1 to entry: Most historical data applications assume only one current value per timestamp. Therefore, the
timestamp of the data is considered the unique identifier for that value. Some data or meta data such as Annotations
can permit multiple values to exist at a single timestamp. In such cases the Server would use one or more parameters
of the StructuredHistoryData entry to uniquely identify each element within the history collection. Annotations are
examples of StructuredHistoryData.
3.2 Abbreviated terms
DA Data Access
HA Historical Access
HDA Historical Data Access
UA Unified Architecture
IEC 62541-11:2025 © IEC 2025
4 Concepts
4.1 General
This document defines the handling of historical time series data and historical Event data in
the OPC Unified Architecture (in a Historian). Included is the specification of the representation
of historical data and Events in the AddressSpace.
4.2 Data architecture
A Server supporting Historical Access provides Clients with transparent access to different
historical data and/or historical Event sources (e.g., process Historians, event Historians, etc.).
The historical data or Events can be in a proprietary data collection, database or a short-term
buffer within memory. A Server supporting Historical Access will provide historical data and
Events for all or a subset of the available Variables, Objects, Properties or Views within the
Server AddressSpace.
Figure 1 illustrates how the AddressSpace of a UA Server can consist of a broad range of
different historical data and/or historical Event sources.

Figure 1 – Possible OPC UA Server supporting Historical Access
The Historian can be implemented as a standalone OPC UA Server that collects data from
another OPC UA Server or another data source. The Historian can also just aggregate historical
data from underlying Historians. The Client that references the OPC UA Server supporting
Historical Access for historical data can be simple trending packages that desire values over a
given time frame or they can be complex reports that require data in multip
...