EN 62541-8:2011

SLOVENSKI STANDARD
01-februar-2012
Poenotena arhitektura OPC - 8. del: Dostop do podatkov (IEC 62541-8:2011)
OPC unified architecture - Part 8: Data access (IEC 62541-8:2011)
OPC Unified Architecture - Teil 8: Zugriff auf Automatisierungsdaten (IEC 62541-8:2011)
Architecture unifiée OPC - Partie 8: Accès aux données (CEI 62541-8:2011)
Ta slovenski standard je istoveten z: EN 62541-8:2011
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 62541-8
NORME EUROPÉENNE
December 2011
EUROPÄISCHE NORM
ICS 25.040.40; 25.100.01
English version
OPC unified architecture -
Part 8: Data Access
(IEC 62541-8:2011)
Architecture unifiée OPC -  OPC Unified Architecture -
Partie 8: Accès aux données Teil 8: Zugriff auf Automatisierungsdaten
(CEI 62541-8:2011) (IEC 62541-8:2011)

This European Standard was approved by CENELEC on 2011-11-22. 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, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2011 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62541-8:2011 E
Foreword
The text of document 65E/194/FDIS, future edition 1 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
The following dates are fixed:
(dop) 2012-08-22
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2014-11-22
• latest date by which the national
standards conflicting with the
document have to be withdrawn
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.
Endorsement notice
The text of the International Standard IEC 62541-8:2011 was approved by CENELEC as a European
Standard without any modification.

- 3 - EN 62541-8:2011
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application 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  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
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
IEC 62541-8 ®
Edition 1.0 2011-10
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
PRICE CODE
INTERNATIONALE
CODE PRIX Q
ICS 25.040.40; 25.100.01 ISBN 978-2-88912-727-6

– 2 – 62541-8 © IEC:2011
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviations . 6
3.1 Terms and definitions . 6
3.2 Abbreviations . 7
4 Concepts . 7
5 Model . 8
5.1 General . 8
5.2 Variable Types . 9
5.2.1 DataItemType . 9
5.2.2 AnalogItemType . 10
5.2.3 DiscreteItemType . 11
5.3 AddressSpace Model . 12
5.4 Attributes of DataItems . 13
5.5 Property DataTypes. 14
5.5.1 Overview . 14
5.5.2 Range . 14
5.5.3 EUInformation . 14
6 Data Access specific usage of Services . 15
6.1 General . 15
6.2 PercentDeadband . 15
6.3 Data Access Status Codes . 15
6.3.1 Overview . 15
6.3.2 Operation level result codes . 15
6.3.3 LimitBits . 17
6.3.4 SemanticsChanged . 17

Figure 1 – OPC DataItems are linked to automation data . 8
Figure 2 – DataItem VariableType Hierarchy . 9
Figure 3 – Representation of DataItems in the AddressSpace . 13

Table 1 – DataItemType Definition . 9
Table 2 – AnalogItemType Definition . 10
Table 3 – DiscreteItemType Definition . 11
Table 4 – TwoStateDiscreteType Definition . 11
Table 5 – MultiStateDiscreteType Definition . 12
Table 6 – Range Data Type Structure . 14
Table 7 – Range Definition. 14
Table 8 – EUInformation Data Type Structure . 14
Table 9 – EUInformation Definition . 15
Table 10 – Operation level result codes for BAD data quality . 16
Table 11 – Operation level result codes for UNCERTAIN data quality . 16
Table 12 – Operation level result codes for GOOD data quality . 17

62541-8 © IEC:2011 – 3 –
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.
The text of this standard is based on the following documents:
FDIS Report on voting
65E/194/FDIS 65E/216/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.

– 4 – 62541-8 © IEC:2011
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.
62541-8 © IEC:2011 – 5 –
INTRODUCTION
This International Standard is the specification for developers of OPC UA applications. The
specification is a result of an analysis and design process to develop a standard interface to
facilitate the development of applications by multiple vendors that will inter-operate
seamlessly together.
– 6 – 62541-8 © IEC:2011
OPC UNIFIED ARCHITECTURE –
Part 8: Data Access
1 Scope
This part of IEC 62541 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 complemental 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 referenced documents are indispensable for the application 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, OPCUnified architecture – Part 5: Information Model
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 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 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.
3.1.2
AnalogItem
DataItems that represent continuously-variable physical quantities
NOTE 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.

62541-8 © IEC:2011 – 7 –
3.1.3
DiscreteItem
DataItems that represent data that may take on only a certain number of possible values
NOTE 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
EngineeringUnits
units of measurement for AnalogItems that represent continuously-variable physical quantities
(e.g., length, mass, time, temperature)
NOTE 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
DA Data Access
EU Engineering Unit
UA Unified Architecture
4 Concepts
Data Access deals with the representation and use of automation data in OPC UA Servers.
Automation data can be located inside the OPC UA Server or on I/O cards directly connected
to the OPC UA 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
an OPC UA server might consist of a broad range of different DataItems.

– 8 – 62541-8 © IEC:2011
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 Part 4. Cha
...