IEC 81346-1:2022

FINAL
INTERNATIONAL IEC/FDIS
DRAFT
STANDARD 81346-1
ISO/TC 10
Industrial systems, installations and
Secretariat: SIS
equipment and industrial products —
Voting begins on:
2021-12-21 Structuring principles and reference
designations —
Voting terminates on:
2022-02-15
Part 1:
Basic rules
Systèmes industriels, installations et appareils, et produits
industriels — Principes de structuration et désignations de
référence —
Partie 1: Règles de base
This draft is submitted to a parallel vote in ISO and in IEC.
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
IEC/FDIS 81346-1:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © IEC 2021

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CONTENTS
FOREWORD . 8
INTRODUCTION . 11
1 Scope . 13
2 Normative references . 13
3 Terms and definitions . 14
4 Concepts . 16
4.1 Object . 16
4.2 Aspect . 17
4.3 Systems . 19
4.4 Structuring . 19
4.5 Function . 19
4.6 Products and components . 20
4.7 Location . 21
4.8 Types. 21
4.9 Object occurrences and product individuals . 21
4.10 Relations between concepts . 22
5 Structuring principles . 23
5.1 General . 23
5.2 Forming structures . 26
5.3 Function-oriented structure . 28
5.4 Product-oriented structure. 29
5.5 Location-oriented structure . 30
5.6 Type-oriented structure . 31
5.7 Structures based on "other aspects" . 31
5.8 Structures based on more than one aspect . 33
6 Construction of reference designations . 34
6.1 General . 34
6.2 Format of reference designations . 35
6.2.1 Single level . 35
6.2.2 Multi-level . 36
6.2.3 Use of letter codes . 36
6.3 Different structures within the same aspect . 37
7 Reference designation set . 37
8 Designation of locations . 39
8.1 General . 39
8.2 Assemblies . 39
9 Presentation of reference designations . 41
9.1 Reference designations . 41
9.2 Reference designation set . 42
9.3 Presentation of identifiers for the top-node . 43
10 Labelling . 44
11 Presentation of properties for an object . 45
12 Application of the reference designation system . 46
Annex A (informative) Information model on the reference designation system . 47

IEC FDIS 81346-1 © IEC 2021 – 3 –
A.1 General . 47
A.2 EXPRESS-G model . 47
A.3 Entity descriptions . 48
A.3.1 object . 48
A.3.2 aspect . 48
A.3.3 object_occurrence . 48
A.3.4 function_occurrence . 48
A.3.5 product_occurrence . 49
A.3.6 location_occurrence. 49
A.3.7 type_occurrence . 49
A.3.8 other_aspect_occurrence. 49
A.3.9 reference_designation . 49
A.3.10 single_level_reference_designation . 49
A.3.11 multi_level_reference_designation . 50
A.3.12 reference_designation_set . 50
A.3.13 classification_scheme . 50
A.3.14 class . 50
A.3.15 top_node_identifier . 51
A.3.16 product_individual . 51
A.4 Enumerations . 51
A.4.1 aspect_kind . 51
A.4.2 81346_classification_domain . 51
A.5 EXPRESS code . 52
Annex B (informative) Establishment and life cycle of objects . 54
B.1 Establishment and validity of objects . 54
B.2 Life cycle story of an object. 55
B.2.1 Overview . 55
B.2.2 Function aspect and function based on a function-oriented structure (A). 55
B.2.3 Functional requirement specification FR1 (B) . 57
B.2.4 Location aspect and reference designation based on a location-oriented
structure (C) . 57
B.2.5 Component type specification CT1 (D) . 57
B.2.6 Function list for system design FL1 and location list for physical design

LL1 (E) . 58
B.2.7 Product specification PS1 (F) . 58
B.2.8 Parts list for manufacturing/installation PL1 (G) . 58
B.2.9 Transport specification (H) . 59
B.2.10 Installation (J) . 59
B.2.11 Commissioning (K) . 59
B.2.12 Acceptance and individual log IL1 (L) . 59
B.2.13 Operation and maintenance (M) . 59
B.2.14 Alternative motor product individual (N) . 60
B.2.15 Alternative motor type and supplier CT2, PS2 (P) . 60
B.2.16 Process modification (R) . 60
B.2.17 Location extension (S) . 60
B.2.18 Etc. (T) . 60
B.2.19 Closing down (U) . 60
B.2.20 Dismantling (V) . 60
B.2.21 Life cycle end (X) . 61

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B.3 Discussion on the concept "object" . 61
B.3.1 Different meanings of "motor" . 61
B.3.2 Definition of "object" . 61
B.4 Discussion on different life cycles . 62
Annex C (informative) Manipulation of objects . 63
C.1 General . 63
C.2 Establishment and validity of objects . 63
C.2.1 Structuring . 63
C.2.2 Ending the structuring . 64
C.2.3 Relations between closely related objects . 64
C.2.4 The roles of the reference designations set . 66
C.2.5 Example . 66
C.3 Life cycle situations . 72
C.3.1 One object for all aspects . 72
C.3.2 One object for each aspect . 73
Annex D (informative) Interpretation of reference designations using different aspects . 75
Annex E (normative) Object represented with several top nodes in an aspect . 78
E.1 General . 78
E.2 Example using aspect shift in structures . 78
E.3 Example using aspect-oriented structures . 79
Annex F (informative) Examples of multiple structures based on the same aspect . 81
F.1 Different function-oriented structures for a process plant . 81
F.2 Topographical location of a system versus locations within an assembly. 82
F.3 Different structuring for different needs . 83
Annex G (normative) Incorporating sub-objects in object structures . 85
G.1 General . 85
G.2 Example. 85
Annex H (informative) Example of reference designations within a system . 89
Annex I (normative) Designation of relations between objects . 95
I.1 General . 95
I.2 Basic principles . 95
I.3 Designation of associative relations . 95
I.4 Classification of relation kinds . 96
I.5 Example of designation of associative relations . 96
Annex J (normative) Requirements for developing sector-specific parts of the

International Standard 81346 series . 98
J.1 General . 98
J.2 81346 framework information model. 98
J.2.1 EXPRESS-G model . 98
J.2.2 Entity descriptions . 99
J.2.3 Enumerations – 81346_classification_domain . 101
J.2.4 EXPRESS code . 103
Annex K (informative) Metadata resource for structure management . 104
Annex L (informative) Recommendations for documentation of the application of the
reference designation system . 106
Annex M (informative) Fundamental ideas for this document. 112
M.1 General . 112
M.2 Basic requirements for a reference designation system . 112

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M.3 Required properties for a reference designation system . 112
Annex N (informative) Relationship to other standards . 113
N.1 General . 113
N.2 Use together with ISO/IEC/IEEE 42010:2011 . 113
N.2.1 General . 113
N.2.2 Architecture description and architecture description language . 113
N.3 Use together with IEC 61355-1:2008 . 114
N.3.1 General . 114
N.3.2 Document designation . 114
N.4 Use together with IEC 61175-1:2015 . 115
N.4.1 General . 115
N.4.2 Signal designation . 115
N.5 Use together with IEC 61666:2010 . 116
N.5.1 General . 116
N.5.2 Terminal designation . 116
Bibliography . 117

Figure 1 – International Standards providing a consistent system for designation,
documentation and presentation of information . 12
Figure 2 – Illustration of an object . 17
Figure 3 – Aspects of an object . 18
Figure 4 – Generic relation between the functionality of a technical system and a
technical process . 19
Figure 5 – Example of functionality of a technical system and a technical process . 20
Figure 6 – Illustration of the concept’s product, component, type, individual and

occurrence . 22
Figure 7 – Illustration of structural decomposition of an object from different aspects . 24
Figure 8 – Illustration of a function-oriented decomposition and product-oriented
composition . 25
Figure 9 – Structure tree of object A (alternative 1) . 26
Figure 10 – Structure tree of object A (alternative 2) . 26
Figure 11 – Constituents in one aspect of object type 1 . 27
Figure 12 – Constituents in one aspect of object type 2 . 27
Figure 13 – Constituents in one aspect of object type 5 . 27
Figure 14 – Structure tree of object type 1 . 28
Figure 15 – Illustration of a function-oriented structure . 29
Figure 16 – Illustration of a product-oriented structure . 30
Figure 17 – Illustration of a location-oriented structure . 31
Figure 18 – Example of the use of "other aspect" . 32
Figure 19 – Example of the use of "other aspect" . 33
Figure 20 – Illustration of an object accessible from three aspects, and where these
aspects are used also for internal structuring . 33
Figure 21 – Illustration of an object identified by means of one aspect and with sub-

objects identified by means of another aspect . 34
Figure 22 – Relation between a multi-level reference designation and its single-level
reference designations . 36
Figure 23 – Example of reference designation sets . 38

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Figure 24 – Example of designation of mounting planes inside a factory build assembly . 40
Figure 25 – Examples of designation of locations inside a factory build assembly . 41
Figure 26 – Different objects on a site identified with top node identifiers . 44
Figure 27 – The common initial portion of reference designations . 44
Figure 28 – Labelling of reference designations . 45
Figure 29 – Presentation of a property in combination with a reference designation . 45
Figure A.1 – EXPRESS-G model of the reference designation system . 47
Figure B.1 – Development situations of objects . 54
Figure B.2 – The object’s life cycle . 56
Figure C.1 – Three independently defined objects . 65
Figure C.2 – Three separate objects with mutual relations . 65
Figure C.3 – The three objects are merged into one . 66
Figure C.4 – Overview of the process system . 67
Figure C.5 – Tree-like structures of the system . 67
Figure C.6 – Completed structures of the system . 68
Figure C.7 – Structures with designated sub-objects . 69
Figure C.8 – Structures with some merged-and-shared objects . 69
Figure C.9 – Relations expressed by reference designation sets in which both
designations are unambiguous . 70
Figure C.10 – Relations expressed by reference designation sets in which one
designation is ambiguous . 71
Figure C.11 – Situations in the beginning of an object's life cycle accessible from three
aspects . 72
Figure C.12 – Situations in the beginning of the life cycle of closely related objects,
each accessible from one aspect . 73
Figure D.1 – Shift from function to product aspect . 75
Figure D.2 – Shift from product to function aspect . 75
Figure D.3 – Shift from product to location aspect . 76
Figure D.4 – Shift from location to product aspect . 76
Figure D.5 – Shift from function to location aspect . 77
Figure D.6 – Shift from location to function aspect . 77
Figure E.1 – Object represented with several independent top nodes in one aspect . 78
Figure E.2 – Example of multi-level reference designations using different aspects of

an object with several independent top nodes in one aspect . 79
Figure E.3 – Object represented with several independent top nodes in one aspect
using aspect-oriented structures . 80
Figure F.1 – Illustration of the concept of additional functional views of an industrial
process plant . 81
Figure F.2 – Location-oriented structure of a plant . 82
Figure F.3 – Location-oriented structure within an assembly unit . 82
Figure F.4 – Location-oriented structures of the plant . 83
Figure F.5 – Example of additional product-oriented structures . 84
Figure G.1 – Sub-contractor's design . 86
Figure G.2 – Receiving organization's design . 86
Figure G.3 – Full structure of the receiving organization's design . 87

IEC FDIS 81346-1 © IEC 2021 – 7 –
Figure H.1 – Process flow diagram for a material handling plant . 89
Figure H.2 – Overview diagram of part of the process system (=V1) and part of the
power supply system (=Q1). 90
Figure H.3 – Structure tree for parts of the material handling plant . 91
Figure H.4 – Layout drawing of the components of the MCC =Q1=W1 . 92
Figure H.5 – Layout drawing indicating the location of the MCC . 92
Figure H.6 – Layout drawing of the locations of the MCC =Q1=W1 . 93
Figure H.7 – Motor starter . 93
Figure H.8 – Product- and location-oriented structure trees for the MCC . 94
Figure I.1 – Structure of a relation designation . 96
Figure J.1 – International Standard 81346 framework – An EXPRESS-G model . 99
Figure N.1 – Principle of document designation . 114
Figure N.2 – Signal designation and signal connection identification . 115
Figure N.3 – Principle of terminal designation . 116

Table 1 – Identification of types, occurrences and individuals within different contexts . 23
Table 2 – Examples of single-level reference designations . 35
Table 3 – Examples of multi-level reference designations with multiple prefix signs . 37
Table 4 – Examples of presentations of multi-level reference designations . 42
Table 5 – Presentation of reference designations of a reference designation set . 43
Table C.1 – Possible reference designation sets . 70
Table G.1 – Reference designations in the receiver's design . 88
Table H.1 – Reference designation set for the constituents of the products MCC and

motor starter . 94
Table I.1 – Example of classification scheme for associative relations . 97
Table I.2 – Examples of relation designations . 97
Table K.1 – Metadata elements for reference designation systems . 105
Table L.1 – Documentation on the application of the rules . 106

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL SYSTEMS, INSTALLATIONS
AND EQUIPMENT AND INDUSTRIAL PRODUCTS –
STRUCTURING PRINCIPLES AND REFERENCE DESIGNATIONS –

Part 1: Basic rules
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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consensus of opinion on the relevant subjects since each technical committee has representation from all
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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 81346-1 has been prepared by IEC technical committee 3: Documentation, graphical
symbols and representations of technical information, in close cooperation with ISO technical
committee 10: Technical product documentation. It is an International Standard.
It is published as a double logo standard and has the status of a horizontal publication in
accordance with IEC Guide 108.
This second edition cancels and replaces the first edition published in 2009. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the scope includes a reference to IEC Guide 108 for being a horizontal publication;
b) synchronization with IEC 81346-2:2019 and ISO 81346-12:2018;

IEC FDIS 81346-1 © IEC 2021 – 9 –
c) the introduction of the type aspect;
d) introduction of an information model of the reference designation system;
e) introduction of an information model for the framework of reference designation system to
comply with International Standard 81346 series;
f) introduction of recommendation for metadata for design structure management;
g) introduction of rules and method for designation of relations between objects;
h) introduction of requirements for development of sector-specific parts of the International
Standard 81346 series;
i) introduction of requirements for incorporation of sub-object in object structures;
j) introduction of recommendations for documentation of the application of the International
Standard 81346 series;
k) introduced definition of new terms used;
l) new rules added and existing rules modified;
m) notes related to rules are converted to normative text as "Comment to Rule nn".
The text of this International Standard is based on the following documents:
Draft Report on voting
3/XX/FDIS 3/XX/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table. In ISO, the standard has been approved by xx members out of xx having cast
a vote.
The language used for the development of this International Standard is English.
A list of parts of the 81346 International Standard, published under the general title Industrial
systems, installations and equipment and industrial products – Structuring principles and
reference designations, can be found on the IEC website.
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/standardsdev/publications.
In this document, italic type is used as follows:
• terms defined in Clause 3 (applies to the text of Clause 3 only);
• in the description of the EXPRESS model, entity names and attribute identifiers;
• commenting on the story from a structuring and reference designation perspective in
Clause B.2.
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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,
• 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 publication using a colour printer.

IEC FDIS 81346-1 © IEC 2021 – 11 –
INTRODUCTION
This document establishes a further development of earlier and withdrawn standards on item
designation. It provides the basics for establishing models of plants, machines, buildings,
infrastructure, etc.
This document specifies:
• principles for structuring of objects including associated information;
• rules on forming of reference designations based on the resulting structure.
By applying the structuring principles, even very large sets of information describing a complex
system can be handled efficiently. In Annex B, the life-cycle story of an object shows how
different structures and aspects are related to the sets of information.
The structuring principles and the rules for reference designations:
• are applicable to objects of both physical and non-physical character;
• provide a system that is easy to navigate within and easy to maintain;
• provide an excellent overview on a technical system since composite structures are simple
to establish and understand;
• support alternative design and engineering processes in the life cycle of an object since
they are based on the successively established results of this process and not on how the
engineering process itself is carried out;
• allow, by accepting more than one aspect, that more than one coding principle can be
applied;
• allow "old structures" to be handled together with "new structures" by using multiple
unambiguous identifiers;
• support individual management for the establishment of reference designations and enable
subsequent integration of modules into larger constructs;
• support the establishment of reusable modules, either as functional specifications or as
physical deliverables;
NOTE The concept of reusable modules encompasses for example, for manufacturers: the establishment of
contract independent modules, and, for operators of complex assemblies: the description of requirements in
terms of supplier independent modules.
• support concurrent work and allow different partners within a project to add and/or remove
data to the structured project result as it proceeds; and
• recognize time factor within the life cycle as important for the application of different
structures based on different views on the considered technical system.
The rules for structuring of information and for the construction of reference designations forms
the basis for creating a reference designation system (RDS) complying with the International
Standard 81346 series. Such systems are used for structuring and designating objects based
on the needs of the organization using them.
The rules listed above are based on the fundamental ideas provided in Annex M that were
defined for the development of the predecessor document for this document.
Annex A provides an information model of the framework described in this document and in
IEC 81346-2. Annex A includes also elements related to other publications where the
application of the reference designation in accordance with International Standard 81346 is
considered.
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Figure 1 provides an overview on International Standards providing a consistent system for
designation, documentation, and presentation of information. Annex A provides more
information on the relations between the International Standard 81346 series and other
publications applying reference designations.

Figure 1 – International Standards providing a consistent system
for designation, documentation and presentation of information
This document describes the fundamental rules and methods for structuring of information and
for the definition of reference designation of objects within buildings, infrastructure, industrial
systems, installations and equipment and industrial products. These rules form a basis for the
establishment of specific reference designation systems (RDS) for use by industries,
enterprises, projects or other organizational contexts.
IEC 81346-2 establishes classification schemes with defined object classes and their
associated letter codes. It is primarily intended for use in reference designations and for
designation of generic types. Classes can also be used for other purposes, for example, by
manufacturers to show multiple potential use of a product. In this way, the classification can
enhance searchability.
Used in combination, this document and IEC 81346-2 define a fundamental framework for
reference designations that is independent of the context in which reference designations are
applied. This is applicable for objects in all technical disciplines and all branches of industry,
and is applicable through the whole life-cycle of objects.
The International Standard 81346 series additionally includes parts that define sector-specific
reference designation frameworks that tailor the fundamental reference designation framework
of this document and IEC 81346-2 to the needs of specific sectors. Requirements for developing
sector-specific parts of the International Standard 81346 series are given in Annex J.

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INDUSTRIAL SYSTEMS, INSTALLATIONS
AND EQUIPMENT AND INDUSTRIAL PRODUCTS –
STRUCTURING PRINCIPLES AND REFERENCE DESIGNATIONS –

Part 1: Basic rules
1 Scope
This part of 81346 International Standard, published jointly by IEC and ISO, establishes general
principles for the structuring of systems including structuring of information about systems.
Based on these principles, rules and guidance are given for the formulation of unambiguous
reference designations for objects in any system.
The reference designation identifies objects for the purpose of creation and retrieval of
information about an object and, where realized, about its corresponding component.
A reference designation labelled at a component is the k
...