EN 61346-1:1996

SLOVENSKI STANDARD
01-december-1997
Industrial systems, installations and equipment and industrial products -
Structuring principles and reference designations - Part 1: Basic rules (IEC 1346-
1:1996)
Industrial systems, installations and equipment and industrial products - Structuring
principles and reference designations -- Part 1: Basic rules
Industrielle Systeme, Anlagen und Ausrüstungen und Industrieprodukte -
Strukturierungsprinzipien und Referenzkennzeichnung -- Teil 1: Allgemeine Regeln
Systèmes industriels, installations et appareils, et produits industriels - Principes de
structuration et désignation de référence -- Partie 1: Règles de base
Ta slovenski standard je istoveten z: EN 61346-1:1996
ICS:
01.110 7HKQLþQDGRNXPHQWDFLMD]D Technical product
L]GHONH documentation
29.020 Elektrotehnika na splošno Electrical engineering in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME
CEI
INTERNATIONALE
IEC
1346-1
INTERNATIONAL
Première édition
STAN DARD
First edition
1996-03
Systèmes industriels, installations et appareils, et
produits industriels — Principes de structuration et
désignations de référence
Partie 1:
Règles de base
Industrial systems, installations and equipment and
industrial products — Structuring principles and
reference designations
Part 1:
Basic rules
© CEI 1996 Droits
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1346-1 © I EC:1996 - 3 -
CONTENTS
Page
FOREWORD
INTRODUCTION 7
Clauses
1 Scope
2 Normative references
3 Definitions
4 Structuring principles
4.1 General
4.2 Function-oriented structure
4.3 Product-oriented structure
4.4 Location-oriented structure
4.5 Object description and object occurrence in forming structures
5 Construction of reference designation
5.1 General
5.2 Format of reference designations
5.2.1 Single-level reference designation
5.2.2 Letter codes
5.2.3 Multi-level reference designation
5.2.4 Examples of structures and reference designations
5.3 Additional aspects of the same type
5.4 Identifying objects using different aspects
5.5 Reference designation set
5.6 Reference designation group 53
6 Location designation 55
Annexes
A Basic requirements and required properties of the reference designation system 57
B Examples of transitions from one aspect to another aspect 63
C Example of transition from one aspect to another aspect where the la tter aspect
has independent representations
D Example of reference designations within a system 75
E Letter codes of IEC 750
F Differences and similarities between the designation system defined in this standard,
IEC 750, ISO 3511 and ISO/DIS 1219-2
G Bibliography
1346-1 © IEC:1996 - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
INDUSTRIAL SYSTEMS, INSTALLATIONS AND EQUIPMENT
AND INDUSTRIAL PRODUCTS -
STRUCTURING PRINCIPLES AND REFERENCE DESIGNATIONS -
Part 1: Basic rules
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3)
The documents produced have the form of recommendations for international use and are published in the
form of standards, technical reports or guides and they are accepted by the National Committees in that
sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
5)
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the
subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 1346-1 has been prepared by subcommittee 3B: Documentation, of
IEC technical committee 3: Documentation and graphical symbols, and ISO technical
committee 10: Technical drawings, product definitions and related documentation. Formal
voting has taken place within IEC SC3B only. However, ISO TC10 has no objection to the
publishing of this International Standard.
This standard cancels and replaces IEC 750 published in 1983.
The text of this standard is based on the following documents:
FDIS Report on voting
3B/144/FDIS 3B/159/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.
IEC 1346 consists of the following parts under the general title: Structuring principles and
reference designations:
- Part 1: Basic rules
- Part 2: Classification of objects and codes for classes (under consideration)
- Part 3: Application guidelines (under consideration)
- Part 4: Discussion of some concepts used in the reference designation system
(technical report) (under consideration)
Annexes A, B, C, D, E, F and G are for information only.

1346-1 ©IEC:1996 – 7 –
INTRODUCTION
In connection with the design, engineering, realization, operation, maintenance and demolition, i.e. the
life-cycle of a system, it is necessary to employ a number of identification systems for different purposes,
for example:
- product (article) numbering system used for identification of types of products;
serial number system used for identification of product individuals;
order number system used for identification of orders/contracts;
-
- reference designation system used for identification of objects within a system/plant.
rt of IEC 1346 deals only with the reference designation system.
This pa
The following table relates the identification systems to theircontexts. The shaded areas show the context
of the reference designation system and the classification provided by the letter codes. The reference
designation system is also used in manufacturing or operating companies for identification of
occurrences of types.
Identifications and their contexts
Occurrences 2)
3)
1)
Individuals
Types
Context
of types
•
The technical
Letter codes
Not applicable
for generic Not applicable
area in
types. .
general
Type designations,
Manufacturing Re erence
g
article (parts) Serial Number
designation
company
number.
/
Plants Serial number,
Reference
Identity No.
Order number,
systems
designation
of typicals
Inventory number.
project
Operating Reference Inventory number
Internal pa rts
designation (serial number)
number
company
characteristics.
1) Type: a class of objects having the same set of
2) Occurrence: the use of a type in a specific position in a plant or system.
3) Individual: one specimen of a type irrespective of where it is being used.
It should be noted that this standard provides a number of possibilities for the construction of reference
designations. For most applications, however, only a subset of the possibilities given need be used.
The basic requirements and the required properties of a reference designation system that form the basis
for the reference designation system described in this standard are given in annex A. It is recommended
to study this annex before reading the normative clauses of this standard. The annex contains a
description of the properties of the reference designation system of this standard in a comparison with the
required properties. A more comprehensive discussion of the basic concepts of the reference designation
system can be found in IEC 1346-4 [3]1.
Annex E contains a reproduction of the letter codes defined in table 1 of IEC 750 [1]. This annex will be
removed in later editions of this standard when IEC 1346-2 is issued.
description of the differences and similarities between the reference
rt
Annex F contains a sho
designation system defined in this standard and those of IEC 750 [1], ISO 3511 [4] [5], and
ISO DIS 1219-2 [6]. This annex will be removed in later editions of this standard.
1 Figures in square brackets refer to the bibliography given in annex G.

1346-1
©
IEC:1996 - 9 -
INDUSTRIAL SYSTEMS, INSTALLATIONS AND EQUIPMENT
AND INDUSTRIAL PRODUCTS -
STRUCTURING PRINCIPLES AND REFERENCE DESIGNATIONS -
Part 1: Basic rules
1 Scope
This part of IEC 1346 establishes general principles for describing the structure of information about
systems and of the systems themselves.
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 correlating information about an object
among different kinds of documents and the products implementing the system. For manufacturing,
installation and maintenance purposes, the reference designation or pa rt of it may also be shown on or
near the physical part corresponding to the object.
The principles laid down are general and are intended to be applicable to all technical areas. They can be
used for systems based on different technologies or for systems combining several technologies.
2 Normative references
The following normative documents contain provisions, which through reference in this text, constitute
provisions of this pa rt of IEC 1346. At the time of publication, the editions indicated were valid. All
normative documents are subject to revision, and pa rties to agreements based on this part of IEC 1346
are encouraged to investigate the possibility of applying the most recent editions of the normative
documents indicated below. Members of IEC and ISO maintain registers of currently valid normative
documents.
IEC 1346-2 : 199x Structuring Principles and Reference Designations.
Part 2: Classification of objects and codes for classes (under consideration)
ISO/IEC 646 : 1991, Information technology - ISO 7-bit coded character set for information interchange
ISO 3166 : 1993, Codes for the representation of names of countries
ISO 4157-1 : 1980, Building drawings - Part 1: Designation of buildings and parts of buildings
ISO 4157-2 : 1982, Technical drawings - Construction drawings - Designation of buildings and parts of buildings -
Part 2: Designation of moms and other areas

1346-1 © IEC:1996 - 11 -
3 Definitions
of IEC 1346, the following definitions apply.
For the purposes of this pa rt
3.1 object: Entity treated in the process of design, engineering, realization, operation, maintenance
and demolition.
NOTES
1 The entity may refer to a physical or non-physical "thing", or to a set of information associated with it.
2 Depending on its purpose, an object may be viewed in different ways called "aspects" (see 3.3).
3.2 system:
Set of interrelated objects.
NOTES
1 Examples of a system: a drive system, a water supply system, a stereo system, a computer.
2 When a system is pa rt of another system, it may be considered as an object.
3.3 aspect: Specific way of selecting information on or describing a system or an object of a system.
NOTE - Such ways may be:
- what the system or object is doing (function viewpoint);
- how the system or object is constructed (product viewpoint);
- where the system or object is located (location viewpoint).
3.4 function: Purpose related to an object.
3.5 product: Intended or accomplished result of labour, or of a natural or artificial process.
NOTES
1 A product usually has a pa rt number, order number, type designation, and/or a name.
2 A technical system or plant can be considered as a product.
3.6 structure: Organization of relations among objects of a system describing constituency-relations
(consist of / is a pa rt of).
3.7 reference designation: Identifier of a specific object with respect to the system of which the object
is a constituent, based on one or more aspects of that system.
3.8 single-level reference designation: Reference designation assigned with respect to the object of
which the specific object is a direct constituent.
3.9 multi-level reference designation: Reference designation derived from a structural path through
an overall system.
Set of reference designations of which at least one unambiguously
3.10 reference designation set:
identifies the object of interest.
a constituent.
NOTE - Other members of the set need not necessarily identify the object of interest but other objects of wh ich it is
Set of reference designations that as a whole unambiguously
3.11 reference designation group:
identify the object of interest and where none of the reference designations in the set by themselves
unambiguously identifies that object.

1346-1 © IEC:1996 - 13 -
4 Structuring principles
4.1 General
In order for a system to be efficiently designed, manufactured, serviced or operated the system and the
s can be further divided.
information about the system are normally divided into pa rts. Each of these pa rt
This successive subdivision into parts and the organization of those parts is called structuring.
An established structure is reflected in:
- the structure of the information about the system, i.e. how the information is distributed among different
documents and/or information systems;
- the structure of the contents within each document (see for example IEC 1082-1 [2]);
- the construction of reference designations (see clause 5).
It is, of course, also reflected in the system or installation itself.
A system, as well as each constituent object, can be viewed in many ways called aspects, as shown in
figure 1, such as:
- what it does;
- how it is constructed;
- where it is located.
Figure 1 - Aspects of an object
The information of relevance and the structuring of objects within a system may differ considerably
depending on the aspect applied. Each aspect will therefore require a separate structure.

– 15 –
1346-1 © IEC:1996
With respect to the three types of aspects considered, this standard describes the corresponding
structures:
- function-oriented structure (see 4.2);
- product-oriented structure (see 4.3);
- location-oriented structure (see 4.4).
Other types of aspects and structures exist, such as for project management and material classification,
which may be the basis for other designation systems. These are not treated in this standard.

- 17 -
1346-1 © IEC:1996
4.2 Function-oriented structure
A function-oriented structure is based on the purpose of a system. A function-oriented structure shows the
subdivision of the system into constituent objects with respect to the function aspect, without necessarily
taking into account the location and/or the products implementing the functions.
Documents giving information based upon a function-oriented structure describe, graphically and/or
textually, how the functions of the system are divided into subfunctions that are combined to fulfil the
intended purpose.
Figure 2 illustrates a function-oriented structure.
Figure 2 - Illustration of a function -oriented structure

1346-1 © IEC:1996 - 19 --
4.3 Product-oriented structure
A product-oriented structure is based on the way a system is implemented, constructed or delivered using
intermediate or final products. A product-oriented structure shows the subdivision of the system into
constituent objects with respect to the product aspect without necessarily taking into account functions
and/or locations. A product can implement one or more independent functions. A product can reside,
alone or together with others, in one location. One product can also reside in more than one location (for
example a stereo system, including its load-speakers).
Documents giving information based upon a product-oriented structure describe, graphically and/or
textually, how a product is divided into subproducts that are manufactured, assembled, or packaged
together to implement or deliver the product.
Figure 3 illustrates a product-oriented structure.
Figure 3 - Illustration of a product-oriented structure

1346-1 ©IEC:1996 - 21 -
4.4 Location-oriented structure
A location-oriented structure is based on the topographical layout of the system, and/or the environment
in which the system is situated. A location-oriented structure shows the subdivision of the system into
constituent objects with respect to the location aspect without necessarily taking into account products
and/or functions. A location can contain any number of products.
In a location-oriented structure, locations may be subdivided successively, for example:
- ground area;
building;
floor;
room / coordinates;
location of an assembly or row of cubicles;
location of a cubicle;
location of a panel;
-
printed circuit board slot;
position on a board.
Documents giving information based upon a location-oriented structure describe, graphically and/or
textually, where the products implementing a system are physically located.
Figure 4 illustrates a location-oriented structure.
Location of a row of cubicles
in a room
Location of a cubicle
in a row of cubicles
Figure 4 - Illustration of a location-oriented structure

1346-1 ©IEC:1996 - 23 -
4.5 Object description and object occurrence in forming structures
Any aspect of an object can be described in terms of the same aspect of other objects. These other
objects become subobjects of the described object. The result from the successive subdivisions of the
same aspect of the objects identified can be represented as a tree as shown in figure 5 .
object type A
(object type B)
(object type B) (object type C)
(object type D) (object type E) (object type D) (object type E)
object type I)
pe I)
(object ty
(object type F) (object type F)
(object type G) (object type H) (object type G) (object type H)
Figure 5 - Structure tree in one aspect of object type A
Another form for this structure tree is shown in figure 6.
object type A
(object type B)
(object type D)
(object type E)
(object type F)
(object type G)
(object type H)
(object ty
pe C) (object type I)
pe B) (object ty
(object type D)
(object type E)
(object type F)
(object type G)
(object type H)
(object type I)
Figure 6 - Structure tree in one aspect of object type A

- 25 -
1346-1 ©IEC:1996
The procedure to achieve the structure tree as shown in figure 5 is normally performed stepwise. The
following is an example of the procedure giving the structure tree shown in figure 5.
Figure 7 shows the subdivision of one aspect of the object type A. In the considered aspect, the
object type A has three constituents. Two of these constituents are identical, referring to the same
object type B.
object type A
Symbol representing the
description of an aspect of an object
O
• Symbol representing the
•
occurrence of an aspect of an object
Constituent 1 Constituent 2 Constituent 3
(object type B) (object type C) (object type B)
Figure 7 - Constituents in one aspect of object type A
Figure 8 shows the subdivision of the same aspect of the object type B. Object type B has two constituents
in the considered aspect, one referring to the object type D and the other referring to the object type E.
object type B
Symbol representing the
O description of an aspect of an object
• Symbol representing the
occurrence of an aspect of an object
Constituent 1 Constituent 2
(object type D) (object type E)
Figure 8 - Constituents in one aspect of object type B
The object type D has no constituents in the considered aspect, while object type E has four constituents
as shown in figure 9.
Symbol representing the
description of an aspect of an object
O
Constituent 1
Constituent 4
• Symbol representing the
(object ty
(object type I)
pe F) Constituent 2 Constituent 3
occurrence of an aspect of an object
(object type G) (object type H)
Figure 9 - Constituents in one aspect of object type E
The complete structure tree for an aspect of the object type A can then be constructed by concatenating
the structure trees for the same aspect of object types identified, as shown in figure 10, and abbreviated
shown in figure 5.
type A
object
Symbol representing the
description of an aspect of an object
O
• Symbol representing the
occurrence of an aspect of an object
object type I)
(object type I)
(object type F)
(object ty ty
pe G) (object type H) (object pe G) (object type H)
Figure 10 - Structure tree in one aspect of object type A

1346-1 ©IEC:1996 - 27 -
5 Construction of reference designation
5.1 General
A reference designation shall unambiguously identify an object of interest within the considered system.
The nodes in tree-like structures such as the one shown in figure 5 represent these objects. The branches
represent the subdivision of these objects into other objects (i.e. subobjects). Each object that occurs
within another object shall be assigned a single-level reference designation unique with respect to the
object in which it occurs. The object represented by the top node shall not be assigned a single-level
reference designation.
number, order number, type number, or a
NOTE - The object represented by the top node may have identifiers such as pa rt
name. See the introduction. The object represented by the top node is assigned a reference designation only when the system is
integrated into a larger system.
5.2 Format of reference designations
5.2.1 Single-level reference designation
A single-level reference designation assigned to an object shall consist of a prefix sign followed either by:
- a letter code, or
- a letter code followed by a number, or
- a number.
For the types of aspects referred to in 4.1, the characters used in the prefix signs to be used to indicate a
reference designation shall be:
when relating to the function aspect of the object;
- when relating to the product aspect of the object;
+ when relating to the location aspect of the object.
For computer implementations, the prefix signs shall be chosen from the GO-set of ISO/IEC 646 or
equivalent international standards.
If both a letter code and a number are used, the number shall follow the letter code. In that case, the
number shall distinguish between objects with the same letter code that are constituents of the same
object.
If numbers by themselves or in combination with a letter code have significant meaning, the meaning shall
be explained in the document or in supporting documentation.
Numbers may contain leading zeros. If leading zeros have significant meaning, the meaning shall be
explained in the document or in supporting documentation.
In order to aid readability it is recommended that numbers and letter codes are kept as sho rt as
practicable.
Figure 11 show examples of single-level reference designations.
Location-oriented
Function-oriented Product-oriented
reference designation
reference designation reference designation
of an object of an object
of an object
=A1 –Al +G1
+RM
=ABC –RELAY
–561 +101
=123
=TXT12 –LET12 +RM101
Figure 11 - Examples of single-level reference designations

1346-1 CD IEC:1996 - 29 -
5.2.2 Letter codes
As described in 5.2.1 a single-level reference designation may consist of a letter code. For the object
being designated, such a letter code may:
indicate the object (as is the case when a count ry code is used for the designation of a location that is
a country);
indicate the class of object.
For letter codes describing the class of object the following applies:
- a letter code shall classify the object regardless of how the object is being used in a specific case;
a letter code may consist of any number of letters. In a letter code consisting of multiple letters, the
second (third etc.) letter shall indicate a subclass of the class indicated by the first (second etc.) letter.
NOTE 1 - The structure of such a classification scheme is independent of the structure of a system.
Letter codes shall be formed using capital Latin letters A to Z (excluding special national letters). Letters I
and O shall not be used if confusion with the digits 1 (one) and 0 (zero) is likely.
Letter codes indicating the class of objects shall be chosen in accordance with IEC 1346-2.
NOTE 2 - Until IEC 1346-2 is published, reference is made to table I of IEC 750 [1], reproduced in annex E.

1346-1 © IEC:1996 - 31 -
5.2.3
Multi-level reference designation
A multi-level reference designation shall be a coded representation of the path from the top of a structure
tree down to the object of interest. The path will include a number of nodes. The multi-level reference
designation shall be constructed by concatenating the single-level reference designation for each object
represented in the path beginning with the top-most. The number of nodes within a path depends on the
actual needs and complexity of the system considered.
rt number, order number, type number, or a
NOTE - The object represented by the top node may have identifiers such as pa
name. Seethe introduction. The object represented by the top node is assigned a reference designation only when the system is
integrated into a larger system.
If the prefix sign for a single-level reference designation is the same as for the preceding single-level
reference designation:
the prefix sign may be omitted if the preceding single-level reference designation ends with a number
and the following starts with a letter code;
the prefix sign may be replaced by "." (period/full stop).
Only one of these methods shall be used within one multi-level reference designation.
Figure 12 illustrates the relation between single-level reference designations and a multi-level reference
designation.
Multi-level reference designation Single-level reference designations
Figure 12 - Relation between a multi-level reference designation
and its single-level reference designations
(one multi-level reference designation with
six single-level reference designations)
Figure 13 show examples of multi-level reference designations and the way they can be written down.
+G1+111+2
=Al=B2=C3 –A1-1–C–D4 A1–B2–C-04 +G1+H2+3+S4
=A1 B2C3 –A1-1C–D4 –Al B2C–D4 +G1.111.2 +G1 H2+3S4
=A1.B2.C3 A1.1.C.D4 –Al.B2.C.D4 +G1.H2.3.S4
Figure 13 - Examples of multi-level reference designations
In the presentation of a multi-level reference designation, a blank space may be used to separate the
different single-level reference designations. The blank space has no significant meaning and shall only
be used for readability reasons.

1346-1 © IEC:1996 - 33 -
5.2.4 Examples of structures and reference designations
Figures 14, 15 and 16 show the same tree-like structures as in figures 7, 8 and 9 with function-oriented
single-level reference designations indicated. Figure 17 shows the concatenated tree as in figure 5 with
the function-oriented multi-level reference designations indicated.
object type A
Symbol representing the
description of an aspect of an object
O
Symbol representing the
•
occurrence of an aspect of an object
=B1 =C1 =B2
(object type B) (object type C) (object type B)
Figure 14 - Function-oriented structure of object type A
object type B
Symbol representing the
description of an aspect of an object
O
• Symbol representing the
=A1 =F1
occurrence of an aspect of an object
(object type D) (object type E)
Figure 15 - Function-oriented structure of object type B
object type E
Symbol representing the
description of an aspect of an object
O
Symbol representing the
-F1 1 =F2
occurrence of an aspect of an object
(object type F) (object type I)
=U1 =U2
(object ty
pe G) (object type H)
Figure 16 - Function-oriented structure of object type E
object type A
Reference
designations
=C1
=B2A1
=B2F1
Reference Reference
designations designations
=F1 =F1 =U1 =U2 =F2
=U1 =U2 =F2
_l'
t =B1F1 F1 -B2F1 F2
t Î Î
=B1 F1 U1 -B2F1U2
B1 F1U2 -B2F1U1
=B1F1F2 -B2F1F1
Figure 17 - Concatenated function-oriented structure tree of object type A

1346-1 © IEC:1996 - 35 -
5.3 Additional aspects of the same type
If additional views of an aspect type are required, the designation of objects within these views shall be
formed by doubling (tripling etc.) the character used in the prefix sign. The meaning and the application of
the additional views shall be explained in the document or in supporting documentation.
Figure 18 shows some examples of multi-level reference designations using multiple prefix signs.
++B1++2++D++G1++H2
——Al— —B2— —3— —D
++Bl++2D++G1H2
==A==B==W ——Al B2--3D
==A.B.W ——Al .B2.3.D ++B1 .2.D.G1 .H2
Figure 18 - Examples of multi-level reference designations
with multiple prefix signs
Example 1: In figure 19, the same printed circuit board assembly (PCBA) is produced by different
manufacturing and assembly processes, and may therefore be associated with different
product-oriented structures. The PCBA produced by the different processes are completely
interchangeable. A single prefix sign is used to designate the constituent products in the
product documentation related to one manufacturing and assembly process. If the user of
the product (i.e. the PCBA) needs to distinguish among the different product-oriented
structures in his/her documentation, this shall be done by employing "-", "- -", "- - -" and
„
•
The printed circuit board assembly
(PCBA) consists of the board itself
PCBA PCBA
Object x
(object x) and two other products
(object y and object z).
i1 —A3
Object y
Object z
(x) (Y) (z)
—A1A1 —A1A2
(x) (Y)
PCBA PCBA
a) Arrangement drawing of the PCBA
Designation of object y in the documents prepared —A2 —Al
by the user (buyer) of the product PCBA: (x+z) \ —A2
—Al / (Y+z)
(x) (y)
—A2
—
A1A2
—— —A2A1
A2A1 —A2A2 A1A1 A1A2
(x) (z)
(Y) (z)
c) Designation of the same object in the b) Four possible product-oriented
user-prepared documentation structures
Figure 19 - Example of additional product-oriented structures
Example 2: A product may be structured differently with regard to the different use of the
product-oriented structures, i.e. for engineering, for construction, for operation, for
maintenance, etc. The example shown in figure 19 may illustrate this method too.

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Example 3: Figure 20 illustrates how an industrial-process plant may be described with additional
function-oriented structures. One function-oriented structure is organized according to the
process functions. A second function-oriented structure is based on the controlling
functions, and a third function-oriented structure is based on the energy supply system.
A motor may be identified according to all three structures as indicated in the figure.
Energy supply
function view
Process function view Control function view
High-voltage
Function of Overall process
supply function
VIIINLrocess control function
Coordination control Voltage transforming
Function of
process sections functions level A functions
Low-voltage
Function of process Coordination control
supply functions
section parts functions level B
•
Individual measuring and
actuating functions
is
MO = process-actuating object = controlled object = energy-consuming object
O
Figure 20 - Illustration of the concept of additional functional
views of an industrial-process plant

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Example 4: In connection with the engineering of assembly units, it may be advantageous to make use
of two location-oriented structures:
- one based on a topography of the plant (system);
- the other based on the locations within the assembly units.
For a particular plant, three assembly units are required. However, at the time of engineering
it is not suitable/possible to base the reference designations for the location aspect of the
objects within the units on the topography of the plant. Unambiguous reference designations
are therefore defined for the location of the units in relation to the plant as a whole,
irrespective of plant topography as shown in figure 21.
The plant as a whole,
identified by name,
order number, etc.
f • • Px : reference designation
P1 P2 P3 for the location of unit no. x
Figure 21 - Location-oriented structure of a plant
Using P1, P2 and P3 as starting points, the location-oriented structures for the respective
assembly units can be described by dividing each unit into sections, mounting location within
a section, etc. (see figure 22), which in turn can be assigned suitable reference designations.
The assembly unit as a
whole, identified by name,
E— order number., etc.
Sections
Mounting location
within sections
Figure 22 - Location-oriented structure within an assembly unit
Later in the engineering process when all the necessary information is available, the
respective assembly units can be assigned a reference designation based on the
topography of the plant. These latter reference designations may not necessarily be
unambiguous, for example locations P1 and P2 may be located in the same room.
In our case the single plus (+) could be used for the reference designations based on the
location-oriented structure for the assembly units, while double plus (++) could be used for
reference designations based on the plant topography. See figure 23.
Building
++B1 ++B
Storey (floor) ++F1
Location of assembly units
Room ++R1
Sections
Mounting location
within sections
Locations +P1 and +P2
are in the same room ++R2
Figure 23 - Location-oriented structures of the plant

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5.4
Identifying objects using different aspects
It is not always possible, nor suitable, to identify an object in the considered system by one aspect only.
Different aspects of successive objects may be used by making a transition from one aspect to another
aspect.
Example 1: The location aspect is used to identify the location of a product (e.g. a printed circuit board
assembly, PCBA) and a product aspect is used to identify subproducts (e.g. a resistor) within
that product.
A transition shall be made from one aspect of an object to another aspect of the same object. A transition
can only be performed at an object having more than one aspect. Each of the aspects may have one or
several independent representations (i.e. nodes in a structure tree).
Example 2: An integrated circuit with four independent NAND-functions will have one representation in
the product aspect and four representations in the function aspect.
Example 3: A valve block with three independent valves will have one representation in the product
aspect and three representations in the function aspect.
Figure 24 illustrates an object with several independent representations in one aspect.

Aspect X Aspect Y
Figure 24 - Object with several independent representations in one aspect
The object at which the transition is performed shall be designated according to the aspect from which the
transition is made. The constituent objects in the aspect to which the transition is made shall be given a
single-level reference designation according to that aspect. See figure 25.
If the object at which the transition is performed has several independent representations in the aspect to
which the transition is made, these representations shall be uniquely identified within that aspect of the
object. See figure 26.
NOTE - These unique identifications can be pre-defined or be consecutive numbers.
In order to unambiguously identify the used representation and/or the constituent objects in the aspect to
which the transition is made within the considered system, the following applies:
a) take the reference designation of the object at which the transition is performed;
b) if the object at which the transition is performed has several independent representations in the
aspect to which the transition is made, add the identification of the used representation enclosed in
parenthesis;
c) if the constituent object shall be identified, add the single-level reference designation of the
constituent object.
1346-1 © IEC:1996 - 43 -
The overall system
Location aspect
th two aspects
and product)
roduct aspect
Transition from location
to product aspect
Single-level reference designations

Multi-level reference designation: Multi-level reference designation:

+B1 F2+3D–K1
+B1F2+3D–F10
Figure 25 - Example of multi-level reference designation using different aspects
Object with two aspects
Transition from product to
(product and function)
function aspect
Multi-level reference designation: Multi-level reference designation:
–D2(2)=E2C1 –D2(2)=E2C2
Figure 26 - Example of multi-level reference designations using different aspects
of an object with several independent representations in one aspect

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The following illustrates transitions where the aspect of the object to which the transition is made has only
one representation:
from a function aspect to a product aspect when a function is completely implemented by a product,
and there is no subproduct that by itself completely implements the function;
from a product aspect to a function aspect when a product completely implements exactly one
function;
from a product aspect to a location aspect when a product exists in one location only, and there is no
sublocation that by itself completely contains the product.
from a location aspect to a product aspect when a product completely occupies a location , and there
is no subproduct that completely occupies that location.
NOTES
1 A product may consist of many constructional units not necessarily located at one location.
2 A product does not necessarily need to be designated by a reference designation based on a product-oriented structure, but
can be designated with a reference designation based on a function-oriented or a location-oriented structure.
In order to improve the understanding for the reader of a multi-level reference designation which includes
a transition, the following are given.
A transition from the function aspect to the product aspect implies that the object designated with the
first product-oriented reference designation (i.e. -B1 in figure 27) is a subproduct of the product that
implements the function indicated with the last function-oriented reference designation (i.e. =A2 in
figure 27).
Object with two aspects
(function and product)
Product-oriented structure
Multi-level reference designation =A2–B1
implies:
Transition from function
Subproduct –B1 of the product that implements the function =A2
to product aspect
Figure 27 - Transition from function to product aspect
-
A transition from the product aspect to the function aspect implies that the object designated with the
first function-oriented reference designation (i.e. =B1 in figure 28) is a subfunction of the function
performed by the product indicated with the last product-oriented reference designation (i.e. -A2 in
figure 28).
Object with two aspects
^
(function and product)
Function-oriented structure
A1
L.
Multi-level reference designation –A2=B1
implies:
Subfunction =B1 of the function performed by the product –A2
Transition from product
to function aspe
ct
Figure 28 - Transition from product to function aspect

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A transition from the product aspect to the location aspect implies that the object designated with the
first location-oriented reference designation (i.e. +B1 in figure 29) is a sublocation of the location
wherein the product indicated with the last product-oriented reference designation (i.e. -A2 in figure
29) is completely located.
Product-oriented structure
Object with two aspects
(product and location)
Location-oriented structure
–Al
L.
Multi-level reference designation –A2+B1
implies:
Transition from product
Sublocation +B1 of the location wherein the
to location aspect product–A2 is completely located
Figure 29 - Transition from product to location aspect
- A transition from the location aspect to the product aspect implies that the object designated with the
first product-oriented reference designation (i.e. -B1 in figure 30) is a subproduct of the product that
completely occupies the location indicated with the last location-oriented reference designation (i.e.
+A2 in figure 30).
Object with two aspects
(product and location)
Product-oriented structure
+A2–B1
61 –B2 multi-level reference designation
_ implies:
Transition from location
Subproduct –B1 of the product that completely
to product aspect
occupies the location +A2
Figure 30 - Transition from location to product aspect
Annex B shows more comprehensive examples of transition performed at objects with only one
representation in the aspect to which the transition is made. Annex C shows a more comprehensive
example of a transition performed at an object with several independent representations in the aspect to
which the transition is made.
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5.5
Reference designation set
An object might be considered from different aspects, and might therefore be associated with different
tree-like structures, each structure representing the subdiv
...