EN 62541-8:2015

OPC unified architecture - Part 8: Data Access

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.

OPC Unified Architecture - Teil 8: Zugriff auf Automatisierungsdaten

Architecture unifiée OPC - Partie 8: Accès aux données

L'IEC 62541-8:2015 fait partie intégrante de la série de normes générales sur l'Architecture Unifiée OPC (OPC UA). Elle définit le modèle d'informations associé à l'Accès aux Données (DA). Elle comporte notamment des Types de Variables (VariableTypes) supplémentaires et des descriptions complémentaires des Classes de Noeuds (NodeClasses) et des Attributs (Attributes), nécessaires pour l'Accès aux Données, des Propriétés (Properties) supplémentaires ainsi que d'autres paramètres relatifs aux informations et au comportement. Cette deuxième édition annule et remplace la première édition parue en 2011. Elle constitue une révision technique. Cette édition inclut les modifications suivantes: - Clarification précisant qu'il faut que la bande morte soit comprise entre 0,0 et 100,0. Les violations génèrent l'erreur Bad_DeadbandFilterInvalid; - Ajout de VariableTypes (Types de Variables) gérant les ArrayItems (éléments de matrices) et les DataTypes (Types de Données) les prenant en charge, y compris les types de nombres complexes. Ces types de données sont exigés pour les dispositifs d'analyses complexes mais semblent également utiles.

Enotna arhitektura OPC - 8. del: Dostop do podatkov (IEC 62541-8:2015)

Ta del standarda IEC 62451 je del niza standardov enotne arhitekture OPC (OPC UA) in določa informacijski model, povezan z dostopom do podatkov. Zajema še zlasti dodatne vrste spremenljivk in dopolnilne opise razredov vozlišč ter atributov, ki so potrebni za dostop do podatkov, dodatne lastnosti in druge informacije in delovanja.
Celoten model naslovnega prostora z vsemi razredi vozlišč in atributi je naveden v standardu IEC 62541-3. Opravila za zaznavanje podatkov in dostop do njih so določena v standardu IEC 62541-4.

General Information

• Status: Published
• Publication Date: 14-May-2015
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.100 - Open systems interconnection (OSI)
• Technical Committee: CLC/TC 65CX - Fieldbus
• Drafting Committee: IEC/SC 65E - IEC_SC_65E
• Current Stage: 6060 - Document made available
• Due Date: 15-May-2015
• Completion Date: 15-May-2015
• Mandate: M/490 - Standardisation mandate to the European Standardisation Organisations (ESOs) to support European Smart Grid deployment
• Ref Project: SIST EN 62541-8:2015 - OPC Unified Architecture - Part 8: Data Access (IEC 62541-8:2015)

RELATIONS

• Replaces: EN 62541-8:2011 - OPC unified architecture - Part 8: Data Access
• Effective Date: 10-Dec-2013
• Revised: EN 62541-8:2011 - OPC unified architecture - Part 8: Data Access
• Effective Date: 06-May-2014
• Revised: EN IEC 62541-8:2020 - OPC Unified Architecture - Part 8: Data Access
• Effective Date: 10-Jul-2018
• Replaced By: EN IEC 62541-8:2020 - OPC Unified Architecture - Part 8: Data Access
• Effective Date: 11-Aug-2020

Standards Content (sample)

SLOVENSKI STANDARD
SIST EN 62541-8:2015
01-september-2015
1DGRPHãþD
SIST EN 62541-8:2012
Enotna arhitektura OPC - 8. del: Dostop do podatkov (IEC 62541-8:2015)
OPC Unified Architecture - Part 8: Data Access (IEC 62541-8:2015)

OPC Unified Architecture - Teil 8: Zugriff auf Automatisierungsdaten (IEC 62541-8:2015)

Architecture unifiée OPC - Partie 8: Accès aux données (IEC 62541-8:2015)
Ta slovenski standard je istoveten z: EN 62541-8:2015
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
SIST EN 62541-8:2015 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 62541-8:2015
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SIST EN 62541-8:2015
EUROPEAN STANDARD EN 62541-8
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2015
ICS 25.040.40; 35.100 Supersedes EN 62541-8:2011
English Version
OPC unified architecture - Part 8: Data Access
(IEC 62541-8:2015)

Architecture unifiée OPC - Partie 8: Accès aux données OPC Unified Architecture - Teil 8: Zugriff auf

(IEC 62541-8:2015) Automatisierungsdaten
(IEC 62541-8:2015)

This European Standard was approved by CENELEC on 2015-04-29. 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, 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: Avenue Marnix 17, B-1000 Brussels

© 2015 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 62541-8:2015 E
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SIST EN 62541-8:2015
EN 62541-8:2015 - 2 -
Foreword

The text of document 65E/381/CDV, future edition 2 of IEC 62541-8, 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

EN 62541-8:2015.
The following dates are fixed:
• latest date by which the document has to be implemented at (dop) 2016-01-29
national level by publication of an identical national
standard or by endorsement
(dow) 2018-04-29
• latest date by which the national standards conflicting with
the document have to be withdrawn
This document supersedes EN 62541-8:2011.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC [and/or CEN] 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, and supports essential requirements of EU Directive(s).

Endorsement notice

The text of the International Standard IEC 62541-8:2015 was approved by CENELEC as a European

Standard without any modification.
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SIST EN 62541-8:2015
- 3 - EN 62541-8:2015
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

NOTE 1 When 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 - CLC/TR 62541-1 -
Part 1: Overview and concepts
IEC 62541-3 - OPC unified architecture - EN 62541-3 -
Part 3: Address Space Model
IEC 62541-4 - OPC Unified Architecture - EN 62541-4 -
Part 4: Services
IEC 62541-5 - OPC unified architecture - EN 62541-5 -
Part 5: Information Model
UNECE 20 - Codes for Units of Measure Used in - -
International Trade
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SIST EN 62541-8:2015
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SIST EN 62541-8:2015
IEC 62541-8
Edition 2.0 2015-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
OPC Unified Architecture –
Part 8: Data Access
Architecture unifiée OPC –
Partie 8: Accès aux données
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 25.040.40; 35.100 ISBN 978-2-8322-2273-7

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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SIST EN 62541-8:2015
– 2 – IEC 62541-8:2015 © IEC 2015
CONTENTS

FOREWORD ......................................................................................................................... 4

1 Scope ............................................................................................................................ 6

2 Normative references..................................................................................................... 6

3 Terms, definitions and abbreviations .............................................................................. 6

3.1 Terms and definitions ............................................................................................ 6

3.2 Abbreviations and symbols .................................................................................... 7

4 Concepts ....................................................................................................................... 7

5 Model ............................................................................................................................ 8

5.1 General ................................................................................................................. 8

5.2 SemanticsChanged ............................................................................................... 9

5.3 Variable Types ...................................................................................................... 9

5.3.1 DataItemType .............................................................................................. 9

5.3.2 AnalogItemType ......................................................................................... 10

5.3.3 DiscreteItemType ....................................................................................... 11

5.3.4 ArrayItemType ........................................................................................... 13

5.4 Address Space model ......................................................................................... 18

5.5 Attributes of DataItems ........................................................................................ 19

5.6 DataTypes .......................................................................................................... 20

5.6.1 Overview .................................................................................................... 20

5.6.2 Range ........................................................................................................ 20

5.6.3 EUInformation ............................................................................................ 20

5.6.4 ComplexNumberType ................................................................................. 21

5.6.5 DoubleComplexNumberType ...................................................................... 22

5.6.6 AxisInformation .......................................................................................... 22

5.6.7 AxisScaleEnumeration ................................................................................ 23

5.6.8 XVType ...................................................................................................... 23

6 Data Access specific usage of Services ....................................................................... 23

6.1 General ............................................................................................................... 23

6.2 PercentDeadband ............................................................................................... 24

6.3 Data Access status codes ................................................................................... 24

6.3.1 Overview .................................................................................................... 24

6.3.2 Operation level result codes ....................................................................... 24

6.3.3 LimitBits ..................................................................................................... 26

Figure 1 – OPC DataItems are linked to automation data ....................................................... 8

Figure 2 – DataItem VariableType hierarchy .......................................................................... 9

Figure 3 – Graphical view of a YArrayItem ........................................................................... 15

Figure 4 – Representation of DataItems in the AddressSpace .............................................. 19

Table 1 – DataItemType definition ......................................................................................... 9

Table 2 – AnalogItemType definition ................................................................................... 10

Table 3 – DiscreteItemType definition ................................................................................. 11

Table 4 – TwoStateDiscreteType definition .......................................................................... 12

Table 5 – MultiStateDiscreteType definition ......................................................................... 12

Table 6 – MultiStateValueDiscreteType definition ................................................................ 13

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SIST EN 62541-8:2015
IEC 62541-8:2015 © IEC 2015 – 3 –

Table 7 – ArrayItemType definition ...................................................................................... 14

Table 8 – YArrayItemType definition .................................................................................... 14

Table 9 – YArrayItem item description ................................................................................. 15

Table 10 – XYArrayItemType definition ................................................................................ 16

Table 11 – ImageItemType definition ................................................................................... 17

Table 12 – CubeItemType definition .................................................................................... 17

Table 13 – NDimensionArrayItemType definition .................................................................. 18

Table 14 – Range DataType structure ................................................................................. 20

Table 15 – Range definition ................................................................................................ 20

Table 16 – EUInformation DataType structure ..................................................................... 20

Table 17 – EUInformation definition ..................................................................................... 20

Table 18 – Examples from the UNECE Recommendation ..................................................... 21

Table 19 – ComplexNumberType DataType structure .......................................................... 22

Table 20 – ComplexNumberType definition .......................................................................... 22

Table 21 – DoubleComplexNumberType DataType structure ................................................ 22

Table 22 – DoubleComplexNumberType definition ............................................................... 22

Table 23 – AxisInformation DataType structure .................................................................... 22

Table 24 – AxisScaleEnumeration values ............................................................................ 23

Table 25 – AxisScaleEnumeration definition ........................................................................ 23

Table 26 – XVType DataType structure ............................................................................... 23

Table 27 – XVType definition .............................................................................................. 23

Table 28 – Operation level result codes for BAD data quality ............................................... 25

Table 29 – Operation level result codes for UNCERTAIN data quality .................................. 25

Table 30 – Operation level result codes for GOOD data quality ............................................ 25

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SIST EN 62541-8:2015
– 4 – IEC 62541-8:2015 © IEC 2015
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPC UNIFIED ARCHITECTURE –
Part 8: Data 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, 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.

International Standard IEC 62541-8 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 published in 2011. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:

a) Clarified that deadband has to be between 0.0 and 100.0. Violations result in error

Bad_DeadbandFilterInvalid (6.2)

b) Added VariableTypes handling ArrayItems and DataTypes supporting this, including

complex number types. These data types are required for complex analyzer devices but

seem useful for other domains as well.
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SIST EN 62541-8:2015
IEC 62541-8:2015 © IEC 2015 – 5 –
The text of this standard is based on the following documents:
CDV Report on voting
65E/381/CDV 65E/407/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.

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.
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SIST EN 62541-8:2015
– 6 – IEC 62541-8:2015 © IEC 2015
OPC UNIFIED ARCHITECTURE –
Part 8: Data Access
1 Scope

This part of IEC 62451 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.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. 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
UN/CEFACT: UNECE Recommendation N° 20, Codes for Units of Measure Used in

International Trade, available at http://www.unece.org/cefact/recommendations/rec_index.htm

3 Terms, definitions and abbreviations
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC TR 62541-1,

IEC 62541-3, and IEC 62541-4 as well as the following apply.
3.1.1
DataItem

link to arbitrary, live automation data, that is, data that represents currently valid information

Note 1 to entry: Examples of such data are
• device data (such as temperature sensors),
• calculated data,
• status information (open/closed, moving),
• dynamically-changing system data (such as stock quotes),
• diagnostic data.
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SIST EN 62541-8:2015
IEC 62541-8:2015 © IEC 2015 – 7 –
3.1.2
AnalogItem

DataItems that represent continuously-variable physical quantities (e.g., length, temperature),

in contrast to the digital representation of data in discrete items

Note 1 to entry: Typical examples are the values provided by temperature sensors or pressure sensors. OPC UA

defines a specific VariableType to identify an AnalogItem. Properties describe the possible ranges of AnalogItems.

3.1.3
DiscreteItem

DataItems that represent data that may take on only a certain number of possible values (e.g.,

OPENING, OPEN, CLOSING, CLOSED)

Note 1 to entry: Specific VariableTypes are used to identify DiscreteItems with two states or with multiple states.

Properties specify the string values for these states.
3.1.4
ArrayItem

DataItems that represent continuously-variable physical quantities and where each individual

data point consists of multiple values represented by an array (e.g., the spectral response of

a digital filter)

Note 1 to entry: Typical examples are the data provided by analyser devices. Specific VariableTypes are used to

identify ArrayItem variants.
3.1.5
EngineeringUnits

units of measurement for AnalogItems that represent continuously-variable physical quantities

(e.g., length, mass, time, temperature)

Note 1 to entry: This standard defines Properties to inform about the unit used for the DataItem value and about

the highest and lowest value likely to be obtained in normal operation.
3.2 Abbreviations and symbols
DA Data Access
EU Engineering Unit
UA Unified Architecture
4 Concepts
Data Access deals with the representation and use of automation data in Servers.

Automation data can be located inside the Server or on I/O cards directly connected to the

Server. It can also be located in sub-servers or on other devices such as controllers and

input/output modules, connected by serial links via field buses or other communication links.

OPC UA Data Access Servers provide one or more OPC UA Data Access Clients with
transparent access to their automation data.

The links to automation data instances are called DataItems. Which categories of automation

data are provided is completely vendor-specific. Figure 1 illustrates how the AddressSpace of

a Server might consist of a broad range of different DataItems.
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SIST EN 62541-8:2015
– 8 – IEC 62541-8:2015 © IEC 2015
OPC UA Server
Root
Adressspace
with DataItems
IEC
Figure 1 – OPC DataItems are linked to automation data

Clients may read or write DataItems, or monitor them for value changes. The Services needed

for these operations are specified in IEC 62541-4. Changes are defined as a change in status

(quality) or a change in value that exceeds a client-defined range called a Deadband. To

detect the value change, the difference between the current value and the last reported value

is compared to the Deadband.
5 Model
5.1 General
The DataAccess model extends the variable model by defining VariableTypes. The

DataItemType is the base type. ArrayItemType, AnalogItemType and DiscreteItemType (and

its TwoState and MultiState subtypes) are specializations. See Figure 2. Each of these

VariableTypes can be further extended to form domain or server specific DataItems.

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SIST EN 62541-8:2015
IEC 62541-8:2015 © IEC 2015 – 9 –
BaseDataVariableType
Defined in
IEC 62541-5
Type DataItemType
ArrayItemType AnalogItemType DiscreteItemType
TwoState MultiState MultiStateValue
DiscreteType DiscreteType DiscreteType
IEC
Figure 2 – DataItem VariableType hierarchy
5.2 SemanticsChanged
The StatusCode also contains an informational bit called SemanticsChanged.

Servers that implement Data Access shall set this Bit in notifications if certain Properties

defined in this standard change. The corresponding Properties are specified individually for

each VariableType.

Clients that use any of these Properties should re-read them before they process the data

value.
5.3 Variable Types
5.3.1 DataItemType

This VariableType defines the general characteristics of a DataItem. All other DataItem Types

derive from it. The DataItemType derives from the BaseDataVariableType and therefore

shares the variable model as described in IEC 62541-3 and IEC 62541-5. It is formally defined

in Table 1.
Table 1 – DataItemType definition
Attribute Value
BrowseName DataItemType
IsAbstract False
ValueRank −2 (−2 = ‘Any’)
DataType BaseDataType
References NodeClass BrowseName DataType TypeDefinition ModellingRule

Subtype of the BaseDataVariableType defined in IEC 62541-5; i.e the Properties of that type are inherited.

HasSubtype VariableType AnalogItemType Defined in 5.3.2
HasSubtype VariableType DiscreteItemType Defined in 5.3.3
HasSubtype VariableType ArrayItemType Defined in 5.3.4
HasProperty Variable Definition String PropertyType Optional
HasProperty Variable ValuePrecision Double PropertyType Optional
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SIST EN 62541-8:2015
– 10 – IEC 62541-8:2015 © IEC 2015

Definition is a vendor-specific, human readable string that specifies how the value of this

DataItem is calculated. Definition is non-localized and will often contain an equation that can

be parsed by certain clients.
Example: Definition::= “(TempA – 25) + TempB”

ValuePrecision specifies the maximum precision that the Server can maintain for the item

based on restrictions in the target environment.
ValuePrecision can be used for the following DataTypes:

• For Float and Double values it specifies the number of digits after the decimal place.

• For DateTime values it indicates the minimum time difference in nanoseconds. For

example, a ValuePrecision of 20 000 000 defines a precision of 20 ms.

The ValuePrecision Property is an approximation that is intended to provide guidance to a

Client. A Server is expected to silently round any value with more precision that it supports.

This implies that a Client may encounter cases where the value read back from a Server

differs from the value that it wrote to the Server. This difference shall be no more than the

difference suggested by this Property.
5.3.2 AnalogItemType

This VariableType defines the general characteristics of an AnalogItem. All other AnalogItem

Types derive from it. The AnalogItemType derives from the DataItemType. It is formally

defined in Table 2.
Table 2 – AnalogItemType definition
Attribute Value
BrowseName AnalogItemType
IsAbstract False
ValueRank −2 (−2 = ‘Any’)
DataType Number
References NodeClass BrowseName DataType TypeDefinition ModellingRule

Subtype of the DataItemType defined in 5.3.1 i.e the Properties of that type are inherited.

HasProperty Variable InstrumentRange Range PropertyType Optional
HasProperty Variable EURange Range PropertyType Mandatory
HasProperty Variable EngineeringUnits EUInformation PropertyType Optional

The following paragraphs describe the Properties of this VariableType. If the analog item’s

Value contains an array, the Properties shall apply to all elements in the array.

InstrumentRange defines the value range that can be returned by the instrument.
Example: InstrumentRange::= {-9999.9, 9999.9}

Although defined as optional, it is strongly recommended for Servers to support this Property.

Without an InstrumentRange being provided, Clients will commonly assume the full range

according to the DataType.
The Range Data Type is specified in 5.6.2.

EURange defines the value range likely to be obtained in normal operation. It is intended for

such use as automatically scaling a bar grap
...