EN IEC 62541-13:2020
(Main)OPC Unified Architecture - Part 13: Aggregates
OPC Unified Architecture - Part 13: Aggregates
IEC 62541-13:2020 is available as IEC 62541-13:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 62541-13:2020 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.
OPC Unified Architecture – Teil 13: Aggregation von Daten
Architecture unifiée OPC - Partie 13: Agrégats
IEC 62541-13:2020 est disponible sous forme de IEC 62541-13:2020 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.L'IEC 62541-13:2020 fait partie de la série de spécifications générales sur l'Architecture unifiée OPC (OPC UA) globale. Elle définit le modèle d'information associé aux Agrégats. Cette deuxième édition annule et remplace la première édition parue en 2015. Aucune modification technique n'a été apportée, mais de nombreuses explications ont été introduites. Des corrections ont été apportées aux exemples.
Enotna arhitektura OPC - 13. del: Agregati (IEC 62541-13:2020)
General Information
- Status
- Published
- Publication Date
- 30-Jul-2020
- Technical Committee
- CLC/TC 65X - Industrial-process measurement, control and automation
- Drafting Committee
- IEC/SC 65E - IEC_SC_65E
- Current Stage
- 6060 - Document made available - Publishing
- Start Date
- 31-Jul-2020
- Completion Date
- 31-Jul-2020
Relations
- Effective Date
- 03-Aug-2020
- Effective Date
- 07-Feb-2023
Overview
EN IEC 62541-13:2020 - OPC Unified Architecture (OPC UA) Part 13: Aggregates defines the OPC UA information model and behavior for aggregated data. Published as IEC 62541-13:2020 (RLV) and adopted by CLC/CENELEC, this second edition replaces the 2015 edition. There are no technical changes to the model, but the edition provides numerous clarifications and corrections (including examples). The document is part of the OPC UA specification series and focuses on how aggregate functions and related metadata are represented, requested and returned by OPC UA servers for processed and historical data.
Key topics and technical requirements
- Aggregate information model: object types and nodes used to represent aggregate functions and their metadata (Aggregate Objects, AggregateFunction Object).
- Aggregate functions catalog: formalization of supported aggregates (e.g., average, min, max, count, totals, range, time-based aggregates) and how servers expose capabilities.
- MonitoredItem AggregateFilter: filter parameters and defaults for monitored and processed data, including bounding values and handling for MonitoredItem requests.
- ReadProcessedDetails & AggregateFilter structures: request/response structures used by services to read processed/historical aggregates.
- Service usage and data handling: guidance on how OPC UA services (Read, HistoryRead, Monitoring, etc.) interact with aggregate requests and responses.
- Status codes & information bits: standardized Aggregate-related StatusCodes, operation-level result codes, and flags indicating aggregate quality and applicability.
- Annex with examples: informative examples for historical access and numerous aggregate-specific examples demonstrating expected data, formats and edge-case behavior.
Applications and who uses it
This standard is essential for implementers and users working with time-series and processed data in industrial automation:
- OPC UA product developers implementing servers/clients (historian vendors, PLC/RTU vendors).
- System integrators and automation engineers building SCADA, DCS, MES and IIoT solutions that require server-side or client-side aggregation.
- Data historians, analytics and reporting platforms that consume aggregated process data (averages, totals, counts, durations).
- Architects defining data models and interoperability profiles for process measurement, control and industrial IT applications.
Practical uses include server-side historical aggregation, on-the-fly aggregation for monitoring dashboards, alarm/event correlation using aggregated metrics, and standardized exchange of processed time-series for analytics.
Related standards
- IEC/TR 62541-1 - OPC UA Overview and Concepts
- IEC 62541-3 - Address Space Model
- IEC 62541-4 - Services
- IEC 62541-5 - Information Model
- IEC 62541-8 - Data Access
- IEC 62541-11 - Historical Access
Keywords: OPC Unified Architecture, OPC UA Aggregates, IEC 62541-13:2020, aggregate functions, historical data aggregation, industrial automation, SCADA, IIoT, data analytics.
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Frequently Asked Questions
EN IEC 62541-13:2020 is a standard published by CLC. Its full title is "OPC Unified Architecture - Part 13: Aggregates". This standard covers: IEC 62541-13:2020 is available as IEC 62541-13:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 62541-13:2020 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 62541-13:2020 is available as IEC 62541-13:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 62541-13:2020 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.
EN IEC 62541-13:2020 is classified under the following ICS (International Classification for Standards) categories: 25.040.40 - Industrial process measurement and control; 35.100 - Open systems interconnection (OSI); 35.100.05 - Multilayer applications. The ICS classification helps identify the subject area and facilitates finding related standards.
EN IEC 62541-13:2020 has the following relationships with other standards: It is inter standard links to EN 62541-13:2015, EN IEC 62541-13:2026. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
EN IEC 62541-13:2020 is associated with the following European legislation: Standardization Mandates: M/490. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
EN IEC 62541-13:2020 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2020
Nadomešča:
SIST EN 62541-13:2015
Enotna arhitektura OPC - 13. del: Agregati (IEC 62541-13:2020)
OPC Unified Architecture - Part 13: Aggregates (IEC 62541-13:2020)
OPC Unified Architecture - Teil 13: Aggregation von Daten (IEC 62541-13:2020)
Architecture unifiée OPC - Partie 13: Agrégats (IEC 62541-13:2020)
Ta slovenski standard je istoveten z: EN IEC 62541-13:2020
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 62541-13
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2020
ICS 35.100.05; 25.040.40 Supersedes EN 62541-13:2015 and all of its
amendments and corrigenda (if any)
English Version
OPC Unified Architecture - Part 13: Aggregates
(IEC 62541-13:2020)
Architecture unifiée OPC - Partie 13: Agrégats OPC Unified Architecture - Teil 13: Aggregation von Daten
(IEC 62541-13:2020) (IEC 62541-13:2020)
This European Standard was approved by CENELEC on 2020-07-16. 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,
Turkey 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
© 2020 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62541-13:2020 E
European foreword
The text of document 65E/697/FDIS, future edition 2 of IEC 62541-13, 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) 2021-04-16
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2023-07-16
document have to be withdrawn
This document supersedes EN 62541-13:2015 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 mandate given to CENELEC by the European Commission
and the European Free Trade Association.
Endorsement notice
The text of the International Standard IEC 62541-13:2020 was approved by CENELEC as a European
Standard without any modification.
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.cenelec.eu.
Publication Year Title EN/HD Year
IEC/TR 62541-1 - OPC unified architecture - Part 1: Overview CLC/TR 62541-1 -
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 62541-8 - OPC Unified Architecture - Part 8: Data - -
Access
IEC 62541-11 - OPC Unified Architecture - Part 11: - -
Historical Access
IEC 62541-13 ®
Edition 2.0 2020-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
OPC Unified Architecture –
Part 13: Aggregates
Architecture unifiée OPC –
Partie 13: Agrégats
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40; 35.100.05 ISBN 978-2-8322-8296-0
– 2 – IEC 62541-13:2020 © IEC 2020
CONTENTS
FOREWORD . 7
1 Scope . 9
2 Normative references . 9
3 Terms, definitions, and abbreviated terms . 9
3.1 Terms and definitions . 9
3.2 Abbreviated terms . 12
4 Aggregate information model . 13
4.1 General . 13
4.2 Aggregate Objects . 13
4.2.1 General . 13
4.2.2 AggregateFunction Object . 14
4.3 MonitoredItem AggregateFilter . 16
4.3.1 MonitoredItem AggregateFilter Defaults . 16
4.3.2 MonitoredItem Aggregates and Bounding Values . 16
4.4 Exposing Supported Functions and Capabilities . 16
5 Aggregate specific usage of Services . 17
5.1 General . 17
5.2 Aggregate data handling . 18
5.2.1 Overview . 18
5.2.2 ReadProcessedDetails structure overview . 18
5.2.3 AggregateFilter structure overview . 18
5.3 Aggregates StatusCodes . 19
5.3.1 Overview . 19
5.3.2 Operation level result codes . 19
5.3.3 Aggregate Information Bits . 20
5.4 Aggregate details . 21
5.4.1 General . 21
5.4.2 Common characteristics . 21
5.4.3 Specific aggregated data handling . 24
Annex A (informative) Aggregate Specific examples – Historical Access . 67
A.1 Historical Aggregate specific characteristics . 67
A.1.1 Example Aggregate data – Historian 1 . 67
A.1.2 Example Aggregate data – Historian 2 . 68
A.1.3 Example Aggregate data – Historian 3 . 69
A.1.4 Example Aggregate data – Historian 4 . 70
A.2 Interpolative . 71
A.2.1 Description . 71
A.2.2 Interpolative data . 71
A.3 Average . 73
A.3.1 Description . 73
A.3.2 Average data . 73
A.4 TimeAverage . 74
A.4.1 Description . 74
A.4.2 TimeAverage data . 75
A.5 TimeAverage2. 76
A.5.1 Description . 76
IEC 62541-13:2020 © IEC 2020 – 3 –
A.5.2 TimeAverage2 data . 76
A.6 Total . 78
A.6.1 Description . 78
A.6.2 Total data . 78
A.7 Total2 . 80
A.7.1 Description . 80
A.7.2 Total2 data . 80
A.8 Minimum . 81
A.8.1 Description . 81
A.8.2 Minimum data . 82
A.9 Maximum . 82
A.9.1 Description . 82
A.9.2 Maximum data . 83
A.10 MininumActualTime . 83
A.10.1 Description . 83
A.10.2 MinimumActualTime data . 84
A.11 MaximumActualTime . 84
A.11.1 Description . 84
A.11.2 MaximumActualTime data . 85
A.12 Range . 85
A.12.1 Description . 85
A.12.2 Range data . 86
A.13 Minimum2 . 86
A.13.1 Description . 86
A.13.2 Minimum2 data . 87
A.14 Maximum2 . 87
A.14.1 Description . 87
A.14.2 Maximum2 data . 88
A.15 MinimumActualTime2 . 88
A.15.1 Description . 88
A.15.2 MinimumActualTime2 data . 89
A.16 MaximumActualTime2 . 89
A.16.1 Description . 89
A.16.2 MaximumActualTime2 data . 90
A.17 Range2 . 90
A.17.1 Description . 90
A.17.2 Range2 data . 91
A.18 AnnotationCount . 91
A.18.1 Description . 91
A.18.2 AnnotationCount data . 91
A.19 Count . 92
A.19.1 Description . 92
A.19.2 Count data . 92
A.20 DurationInStateZero . 93
A.20.1 Description . 93
A.20.2 DurationInStateZero data . 93
A.21 DurationInStateNonZero . 93
A.21.1 Description . 93
A.21.2 DurationInStateNonZero data . 93
– 4 – IEC 62541-13:2020 © IEC 2020
A.22 NumberOfTransitions . 94
A.22.1 Description . 94
A.22.2 NumberOfTransitions data . 94
A.23 Start . 95
A.23.1 Description . 95
A.23.2 Start data . 95
A.24 End . 95
A.24.1 Description . 95
A.24.2 End data . 96
A.25 StartBound . 96
A.25.1 Description . 96
A.25.2 StartBound data . 97
A.26 EndBound . 97
A.26.1 Description . 97
A.26.2 EndBound data . 98
A.27 Delta . 98
A.27.1 Description . 98
A.27.2 Delta data . 99
A.28 DeltaBounds . 99
A.28.1 Description . 99
A.28.2 DeltaBounds data . 100
A.29 DurationGood . 100
A.29.1 Description . 100
A.29.2 DurationGood data . 101
A.30 DurationBad . 102
A.30.1 Description . 102
A.30.2 DurationBad data . 102
A.31 PercentGood . 103
A.31.1 Description . 103
A.31.2 PercentGood data . 103
A.32 PercentBad . 104
A.32.1 Description . 104
A.32.2 PercentBad data . 104
A.33 WorstQuality . 105
A.33.1 Description . 105
A.33.2 WorstQuality data . 105
A.34 WorstQuality2 . 106
A.34.1 Description . 106
A.34.2 WorstQuality2 data . 106
A.35 StandardDeviationSample . 107
A.35.1 Description . 107
A.35.2 StandardDeviationSample data . 107
A.36 VarianceSample . 107
A.36.1 Description . 107
A.36.2 VarianceSample data . 108
A.37 StandardDeviationPopulation . 108
A.37.1 Description . 108
A.37.2 StandardDeviationPopulation data . 108
A.38 VariancePopulation . 109
IEC 62541-13:2020 © IEC 2020 – 5 –
A.38.1 Description . 109
A.38.2 VariancePopulation data . 109
Figure 1 – Representation of Aggregate Configuration information in the AddressSpace . 17
Figure 2 – Variable with Stepped = False and Simple Bounding Values . 25
Figure 3 – Variable with Stepped = True and Interpolated Bounding Values . 26
Figure A.1 – Historian 1 . 68
Figure A.2 – Historian 2 . 69
Figure A.3 – Historian 3 . 70
Table 1 – Interpolation examples . 10
Table 2 – AggregateConfigurationType Definition . 13
Table 3 – Aggregate Functions Definition . 14
Table 4 – AggregateFunctionType Definition . 14
Table 5 – Standard AggregateType Nodes . 15
Table 6 – ReadProcessedDetails . 18
Table 7 – AggregateFilter structure . 19
Table 8 – Bad operation level result codes . 19
Table 9 – Uncertain operation level result codes . 20
Table 10 – Data location . 20
Table 11 – Additional information . 20
Table 12 – History Aggregate interval information . 22
Table 13 – Standard History Aggregate Data Type information . 23
Table 14 – Aggregate table description . 27
Table 15 – Interpolative Aggregate summary . 30
Table 16 – Average Aggregate summary . 31
Table 17 – TimeAverage Aggregate summary . 32
Table 18 – TimeAverage2 Aggregate summary . 33
Table 19 – Total Aggregate summary . 34
Table 20 – Total2 Aggregate summary . 35
Table 21 – Minimum Aggregate summary . 36
Table 22 – Maximum Aggregate summary. 37
Table 23 – MinimumActualTime Aggregate summary . 38
Table 24 – MaximumActualTime Aggregate summary . 39
Table 25 – Range Aggregate summary . 40
Table 26 – Minimum2 Aggregate summary. 41
Table 27 – Maximum2 Aggregate summary . 42
Table 28 – MinimumActualTime2 Aggregate summary . 43
Table 29 – MaximumActualTime2 Aggregate summary . 44
Table 30 – Range2 Aggregate summary . 45
Table 31 – AnnotationCount Aggregate summary. 46
Table 32 – Count Aggregate summary . 47
Table 33 – DurationInStateZero Aggregate summary . 48
– 6 – IEC 62541-13:2020 © IEC 2020
Table 34 – DurationInStateNonZero Aggregate Summary . 49
Table 35 – NumberOfTransitions Aggregate summary . 50
Table 36 – Start Aggregate summary . 51
Table 37 – End Aggregate summary . 52
Table 38 – Delta Aggregate summary . 53
Table 39 – StartBound Aggregate summary . 54
Table 40 – EndBound Aggregate summary . 55
Table 41 – DeltaBounds Aggregate summary . 56
Table 42 – DurationGood Aggregate summary . 57
Table 43 – DurationBad Aggregate summary . 58
Table 44 – PercentGood Aggregate summary . 59
Table 45 – PercentBad Aggregate summary . 60
Table 46 – WorstQuality Aggregate summary . 61
Table 47 – WorstQuality2 Aggregate summary. 62
Table 48 – StandardDeviationSample Aggregate summary . 63
Table 49 – VarianceSample Aggregate summary . 64
Table 50 – StandardDeviationPopulation Aggregate summary . 65
Table 51 – VariancePopulation Aggregate summary . 66
IEC 62541-13:2020 © IEC 2020 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPC UNIFIED ARCHITECTURE –
Part 13: Aggregates
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, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their 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) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 62541-13 has been prepared by subcommittee 65E: Devices and integration in enterprise
systems, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This second edition cancels and replaces the first edition of IEC 62541-13, published in 2015.
This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) no technical changes but numerous clarifications. Also some corrections to the examples.
– 8 – IEC 62541-13:2020 © IEC 2020
The text of this standard is based on the following documents:
FDIS Report on voting
65E/697/FDIS 65E/712/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
Throughout this document and the other Parts of the series, certain document conventions
are used:
Italics are used to denote a defined term or definition that appears in the “Terms and
definition” clause in one of the parts of the 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 also often 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 of 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 publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
IEC 62541-13:2020 © IEC 2020 – 9 –
OPC UNIFIED ARCHITECTURE –
Part 13: Aggregates
1 Scope
This part of IEC 62541 is part of the overall OPC Unified Architecture specification series and
defines the information model associated with Aggregates.
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 TR 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 62541-8, OPC Unified Architecture – Part 8: Data Access
IEC 62541-11, OPC Unified Architecture – Part 11: Historical Access
3 Terms, definitions, and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TR 62541-1,
IEC 62541-3, IEC 62541-4, and IEC 62541-11 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1.1
ProcessingInterval
timespan for which derived values are produced based on a specified Aggregate
Note 1 to entry: The total time domain specified for ReadProcessed is divided by the ProcessingInterval. For
example, performing a 10-minute Average over the time range 12:00 to 12:30 would result in a set of three
intervals of ProcessingInterval length, with each interval having a start time of 12:00, 12:10 and 12:20 respectively.
The rules used to determine the interval Bounds are discussed in 5.4.2.2.
3.1.2
interpolated data
data that is calculated from data samples
– 10 – IEC 62541-13:2020 © IEC 2020
Note 1 to entry: Data samples may be historical data or buffered real time data. An interpolated value is
calculated from the data points on either side of the requested timestamp.
3.1.3
EffectiveEndTime
time immediately before endTime
Note 1 to entry: All Aggregate calculations include the startTime but exclude the endTime. However, it is
sometimes necessary to return an Interpolated End Bound as the value for an Interval with a timestamp that is in
the interval. Servers are expected to use the time immediately before endTime where the time resolution of the
Server determines the exact value (do not confuse this with hardware or operating system time resolution). For
example, if the endTime is 12:01:00, the time resolution is 1 second, then the EffectiveEndTime is 12:00:59. See
5.4.2.4.
If time is flowing backwards, Servers are expected to use the time immediately after endTime where the time
resolution of the Server determines the exact value.
3.1.4
extrapolated data
data constructed from a discrete data set but is outside of the discrete data set
Note 1 to entry: It is similar to the process of interpolation, which constructs new points between known points,
but its result is subject to greater uncertainty. Extrapolated data is used in cases where the requested time period
falls farther into the future than the data available in the underlying system. See example in Table 1.
3.1.5
SlopedInterpolation
simple linear interpolation
Note 1 to entry: Compare to curve fitting using linear polynomials. See example in Table 1.
3.1.6
SteppedInterpolation
interpolation holding the last data point constant or interpolating the value based on a
horizontal line fit
Note 1 to entry: Consider the following Table 1 of raw and Interpolated/Extrapolated values:
Table 1 – Interpolation examples
Timestamp Raw Value Sloped Interpolation Stepped Interpolation
12:00:00 10
12:00:05 15 10
12:00:08 18 10
12:00:10 20
12:00:15 25 20
12:00:20 30
SlopedExtrapolation SteppedExtrapolation
12:00:25 35 30
12:00:27 37 30
3.1.7
bounding values
values at the startTime and endTime needed for Aggregates to compute the result
IEC 62541-13:2020 © IEC 2020 – 11 –
Note 1 to entry: If Raw data does not exist at the startTime and endTime a value shall be estimated. There are
two ways to determine Bounding Values for an interval. One way (called Interpolated Bounding Values) uses the
first non-Bad data points found before and after the timestamp to estimate the bound. The other (called Simple
Bounding Values) uses the data points immediately before and after the boundary timestamps to estimate the
bound even if these points are Bad. Subclauses 3.1.8 and 3.1.9 describe the two different approaches in more
detail.
In all cases the TreatUncertainAsBad (see 4.2.1.2) flag is used to determine whether Uncertain values are Bad or
non-Bad.
If a Raw value was not found and a non-Bad bounding value exists the Aggregate Bits (see 5.3.3) are set to
‘Interpolated’.
When calculating bounding values, the value portion of Raw data that has Bad status is set to null. This means the
value portion is not used in any calculation and a null is returned if the raw value is returned. The status portion is
determined by the rules specified by the bound or Aggregate.
The Interpolated Bounding Values approach (see 3.1.8) is the same as what is used in Classic OPC Historical Data
Access (HDA) and is important for applications such as advanced process control where having useful values at all
times is important. The Simple Bounding Values approach (see 3.1.9) is new in this standard and is important for
applications which shall produce regulatory reports and cannot use estimated values in place of Bad data.
3.1.8
interpolated bounding values
bounding values determined by a calculation using the nearest Good value
Note 1 to entry: Interpolated Bounding Values using SlopedInterpolation are calculated as follows:
• if a non-Bad Raw value exists at the timestamp then it is the bounding value;
• find the first non-Bad Raw value before the timestamp;
• find the first non-Bad Raw value after the timestamp;
• draw a line between before value and after value;
• use point where the line crosses the timestamp as an estimate of the bounding value.
The calculation can be expressed with the following formula:
V = (T – T ) × ( V – V )/( T – T ) + V
bound bound before after before after before before
where V is a value at ‘x’ and T is the timestamp associated with V .
x x x
If no non-Bad values exist before the timestamp the StatusCode is Bad_NoData. The StatusCode is
Uncertain_DataSubNormal if any Bad values exist between the before value and after value. If either the before
value or the after value are Uncertain the StatusCode is Uncertain_DataSubNormal. If the after value does not
exist the before value shall be extrapolated using SlopedExtrapolation or Steppe
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