SIST EN ISO 16757-4:2026

SLOVENSKI STANDARD
01-januar-2026
Podatkovne strukture digitalnih knjižnic gradnikov stavbnih sistemov - 4. del:
Strukture podatkovnega slovarja za kataloge izdelkov (ISO 16757-4:2025)
Data structures for electronic product catalogues for building services - Part 4: Data
Dictionary structures for product catalogues (ISO 16757-4:2025)
Datenstrukturen für elektronische Produktkataloge der Technischen Gebäudeausrüstung
- Teil 4: Datenwörterbücher für Produktkataloge (ISO 16757-4:2025)
Structures de données pour catalogues électroniques de produits pour les services du
bâtiment - Partie 4: Titre manque (ISO 16757-4:2025)
Ta slovenski standard je istoveten z: EN ISO 16757-4:2025
ICS:
35.240.67 Uporabniške rešitve IT v IT applications in building
gradbeništvu and construction industry
91.010.01 Gradbeništvo na splošno Construction industry in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 16757-4
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2025
EUROPÄISCHE NORM
ICS 91.010.01
English Version
Data structures for electronic product catalogues for
building services - Part 4: Data Dictionary structures for
product catalogues (ISO 16757-4:2025)
Structures de données pour catalogues électroniques Datenstrukturen für elektronische Produktkataloge
de produits pour les services du bâtiment - Partie 4: der Technischen Gebäudeausrüstung - Teil 4:
Structures des dictionnaires de données pour les Datenwörterbücher für Produktkataloge (ISO 16757-
catalogues de produits (ISO 16757-4:2025) 4:2025)
This European Standard was approved by CEN on 29 September 2025.

CEN 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 CEN
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 CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16757-4:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 16757-4:2025) has been prepared by Technical Committee ISO/TC 59
"Buildings and civil engineering works" in collaboration with Technical Committee CEN/TC 442
“Building Information Modelling (BIM)” the secretariat of which is held by SN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2026, and conflicting national standards shall be
withdrawn at the latest by April 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 16757-4:2025 has been approved by CEN as EN ISO 16757-4:2025 without any
modification.
International
Standard
ISO 16757-4
First edition
Data structures for electronic
2025-10
product catalogues for building
services —
Part 4:
Data dictionary structures for
product catalogues
Structures de données pour catalogues électroniques de produits
pour les services du bâtiment —
Partie 4: Structures des dictionnaires de données pour les
catalogues de produits
Reference number
ISO 16757-4:2025(en) © ISO 2025

ISO 16757-4:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 16757-4:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Modelling of required kinds of data . 3
4.1 General .3
4.2 Overall model .3
4.3 Subject kinds of the overall model .4
4.3.1 Product .4
4.3.2 Catalogue . .5
4.3.3 Block .6
4.3.4 Ports and in/outlets .7
4.4 Relationship types .9
4.4.1 isSubtypeOf .9
4.4.2 hasPart .10
4.4.3 hasBlock .11
4.4.4 isDependentOn .11
4.4.5 isSubkindOf .11
4.5 Property kinds and their representation in the overall model . 12
4.5.1 General . 12
4.5.2 What does a property describe . 12
4.5.3 Representation of the property kinds using the overall model . 13
4.6 Relationship to data templates . 15
5 Representation of the overall model by means of ISO 12006-3 .15
5.1 General . 15
5.2 Relationships in ISO 12006-3 .16
5.2.1 Overview .16
5.2.2 Property relationships .16
5.2.3 Subject relationships .16
5.3 Dictionary meta level to define subject kinds and relationship types .17
5.4 Kinds of subjects at the dictionary meta level . 20
5.5 Subject relationship types at the dictionary meta level . 20
5.6 Property relationships . 22
6 Specific rules and recommendations .22
6.1 General . 22
6.2 Rules for specific situations . 22
6.2.1 Cardinality properties for hasPart and hasBlock relationships . 22
6.2.2 References to literature . 22
6.2.3 Positioning in space . 23
6.2.4 Predefined calculation functions for dynamic properties . 23
6.2.5 Relationships to classifications or other dictionaries . 23
6.3 Recommendations for dealing with controlled value lists .24
6.3.1 Problem description .24
6.3.2 Property value list with subject contextual filtering .24
Bibliography .25

iii
ISO 16757-4:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 59, Buildings and civil engineering works],
Subcommittee SC 13, Organization and digitization of information about buildings and civil engineering
works, including building information modelling (BIM), in collaboration with the European Committee
for Standardization (CEN) Technical Committee CEN/TC 442, Building Information Modelling (BIM), in
accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
A list of all parts in the ISO 16757 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO 16757-4:2025(en)
Introduction
Building information modelling (BIM) provides a means for describing and displaying information required
throughout the asset life cycle. Increasingly this modelling approach is expanding to encompass all aspects
of the built environment, including civil infrastructure, utilities and public space.
The ISO 16757 series provides the structure of a product catalogue model for data sharing and data exchange
of product models in product catalogues. It contains specifications for:
— selection of products from different product classes and product variants;
— combining product components and accessories to products;
— geometrical representation in technical systems;
— connectivity to other products in models of technical systems;
— calculation of dynamic property values in accordance with the product behaviour in technical systems.
This document outlines the requirements for data dictionaries to support both semantic definitions and
data modelling in product catalogues. ISO 12006-3 defines the underlying data model for related data
dictionaries and serves as the foundation of this document.
Tools are used to define, simulate and operate building services systems (including e.g. HVAC systems and
building automation systems). To build such a system basically means to interconnect different products
in a way that the resulting system fits into the building and works in accordance with the functional
requirements. The products are selected from product catalogues of manufacturers or distributors.
Important aspects of these products are their connection points and information on their behaviour in
different situations.
The goal of this document is to support the engineering tools by enabling them to identify the relevant
information easily in different data dictionaries. In the area of building services, a few generic concepts are
widely used:
— dynamic properties describing the behaviour of products in different situations and load cases that are
dependent on external properties describing external conditions;
— a distinction of data dictionary entries representing products, meta data of catalogues, and specific
features of products like subfunctions or ports.
This document defines common kinds of data dictionary elements that provide a way to identify the basic
structures across data dictionaries.
Besides this document, the ISO 16757 series contains the following documents:
— ISO 16757-1 describes the fundamental concepts and assumptions about the creation of manufacturer-
related product catalogues as BIM data exchange models. It describes the content of product catalogues
and the mapping of the content to a data format.
This data format provides the opportunity to search and select product data together with accessory
data which can be read into software applications for planning, designing, calculating and simulating as
well as for facility management.
— ISO 16757-2 describes the concept of geometry of the building services product data of a product
catalogue in form of 2D symbols and 3D shape models and specifies the required spaces and ports.
It contains the fundamental concepts and assumptions about the parametric geometry of special
products, used in planning software applications e.g. for air condition systems such as ducts and
transitions between different forms. It also contains a concept for representing products as 3D solid
models, which are made from thin sheet metal.

v
ISO 16757-4:2025(en)
— ISO 16757-5 specifies the organization of product catalogues on the basis of ISO 16739-1 (Industry
Foundation Classes, IFC) and EN 17549-2. These product catalogues get the semantics of their properties
from data dictionaries that are described in this document.
It contains an overview about the representation of important elements of product catalogues and gives
detailed specifications of the usage of IFC structures in the product catalogues.

vi
International Standard ISO 16757-4:2025(en)
Data structures for electronic product catalogues for building
services —
Part 4:
Data dictionary structures for product catalogues
1 Scope
This document specifies requirements for data dictionaries that are used by product catalogues for building
services to provide the semantics of their definitions and data modelling. For this purpose, it defines an
overall model that contains:
— subject kinds that allow to distinguish:
— product subjects representing products in product catalogues;
— catalogue subjects comprising meta data of product catalogues;
— various kinds of blocks that collect properties of complex product features, including ports and in/
outlets;
— relationship types that allow to distinguish between different kinds of relationships like isSubtypeOf,
hasPart, or hasBlock;
— property kinds to distinguish between:
— static properties describing products by providing property values in product catalogues;
— dynamic properties that describe the behaviour of products;
— external properties that represent external conditions that influence the behaviour of the product
by influencing the values of dynamic properties.
This document also describes a mapping of the overall model to the data dictionary model of ISO 12006-3 by
introducing a dictionary meta level.
Finally, to overcome deficiencies of the standards underlying ISO 16757-5 in capturing all aspects of product
catalogues, this document provides some rules and recommendations for required data dictionary elements.
This document does not describe how product catalogues have to be organized, and it does not describe any
formats for the exchange of product catalogues. Product catalogues are described in ISO 16757-5.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 12006-3, Building construction — Organization of information about construction works — Part 3:
Framework for object-oriented information
ISO 23386, Building information modelling and other digital processes used in construction — Methodology to
describe, author and maintain properties in interconnected data dictionaries

ISO 16757-4:2025(en)
ISO 23387:2025, Building information modelling (BIM) – Data templates for objects used in the life cycle of assets
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
property
defined characteristic suitable for the description and differentiation of the objects in a class
[SOURCE: ISO 22274:2013, 3.25, modified — Example has been removed.]
3.2
product property
property (3.1) that describes a product in a product catalogue
EXAMPLE In case of a radiator, examples of product properties are length, width and depth.
3.3
external property
property (3.1) that describes an aspect that is external to a product but influences the behaviour of the product
EXAMPLE In case of a radiator, examples of external properties are the temperature of the incoming medium and
the room temperature.
Note 1 to entry: External properties do not describe the product itself.
3.4
static property
product property (3.2) that is not influenced by external conditions
EXAMPLE In case of a radiator, examples of static properties are length, width and depth that do not depend on
other properties and volume that depends on length, width and depth.
3.5
dynamic property
product property (3.2) that depends on at least one external property (3.3)
EXAMPLE In case of a radiator, an example of a dynamic property is the temperature of the outgoing medium that
depends, among others, on the temperature of the incoming medium and the room temperature.
3.6
in/outlet
interface of a technical unit to its environment for the transfer of substances, energy or signals
3.7
port
interface of a technical unit that can be connected to such an interface of another technical unit for the
transfer of substances, signals, energy or forces
3.8
block
composed property
group of properties (3.1) corresponding to a feature needing multiple properties to be defined
[SOURCE: ISO 23386:2020, 3.8, modified — The preferred term "block" has been added; "category of" has
been removed from the beginning of the definition; note 1 to entry and example have been removed.]

ISO 16757-4:2025(en)
4 Modelling of required kinds of data
4.1 General
For data exchange, both the provider and the recipient should have the same understanding of the data; the
data should be provided on a common basis. The goal is to create this common basis in an open, online data
dictionary. In this clause the necessary kinds of data for that purpose are examined. A data dictionary that
conforms to this document shall provide the necessary structures to support these kinds of data.
The focus of this document is the description of products in a product catalogue. This is in some aspects a
view different from that of a designed building where the products are installed in systems in the building.
The manufacturer does not know how and where the products will be installed within a specific system.
Nevertheless, to describe the behaviour of a product, the manufacturer must provide information on
how the product reacts on different external conditions and how dynamic properties are influenced by
environmental and system-specific factors.
4.2 Overall model
The overall model shows the kinds of data that are required for the description of building services products
in manufacturer’s product catalogues (see Figure 1). It contains a number of subject kinds, a number of
relationship types, and it describes a number of property kinds. In a data dictionary, the subjects shall be
related to their subject kind (see 5.3).
Figure 1 — Overall model
The overall model contains the following subject kinds:
— product: subjects that represent the products in a product catalogue;
— catalogue: subjects that represent the meta data of product catalogues;
— block: subjects representing a feature of an object that is described by more than one property;
— port: specialization of block, representing connection points where ports of other products can
connect to;
— in/outlet: specialization of block, representing interfaces of a product to its environment;

ISO 16757-4:2025(en)
— external: specialization of block, collecting external properties (see 4.5.3.2).
The following relationship types have been defined in the overall model, and the following kinds of line
types and arrow shapes have been used to represent the relationship types in graphical representations:
isSubtypeOf relationship, relating a subject to a more general subject of the same kind;
hasPart relationship, relating a subject to its parts;
hasBlock relationship, relating a product or a catalogue to their blocks;
hasProperty, relating a subject to its properties;
isDependentOn, relating a dependent property to the properties that determine its value;
isSubkindOf, relating subkinds to their more general subject kind.
A data dictionary that conforms to this document shall contain subjects of these subject kinds and
relationships of these relationship types. In the following, subjects will be called in accordance with their
kind and relationships will be called in accordance with their type.
EXAMPLE A subject of kind block is called block subject, a subject of kind product is called product subject, and a
relationship of type hasPart is called hasPart relationship.
NOTE The subject kind external is described in 4.5.3.2.
4.3 Subject kinds of the overall model
4.3.1 Product
Properties are used to describe products. The data dictionary, however, does not contain concrete products.
Products are contained in product catalogues (and databases) that assign the products to product subjects
in a data dictionary. A product subject shall define the properties that can be used to describe products.
These properties are related to that product subject by means of the hasProperty relationship.
A product subject P can be involved in various types of relationships:
— isSubtypeOf: relating it to another product subject that provides a more abstract view of P (see 4.4.1);
— hasPart: relating it to other product subjects that represent the parts or components of P (see 4.4.2);
— hasBlock: relating it to block subjects that represent complex features of P (see 4.4.3).
Product subjects can be independently instantiated, that means, in a product catalogue a product can exist
independently of any other objects. That is different to blocks (see 4.3.3): Blocks shall only exist in a product
catalogue in the context of another object (a product, a block or a catalogue).
EXAMPLE 1 In Figure 2, two product subjects, called “convector” and “radiator”, are specializations of a more
generic product subject “heater”. They are related to it by isSubtypeOf relationships. That means that both convector
and radiator have implicitly also the properties length and height because they inherit them from heater. This is shown
in Figure 2 by the grey repetition of the inherited properties.

ISO 16757-4:2025(en)
Figure 2 — Product subjects related by isSubtypeOf relationships
EXAMPLE 2 A central heating system can be defined as a system that consists of some components: for instance,
it can contain a burner, a boiler and a pump. In a data dictionary, such a central heating system is represented by a
product subject. In the same way, the burner, the boiler and the pump are represented by product subjects. Then the
product subject “central heating system” is related to its components by means of hasPart relationships (see Figure 3).
Figure 3 — System “central heating system” with hasPart relationships
4.3.2 Catalogue
Properties are also used to add meta data to product catalogues. The data about product catalogues
comprise, for instance, the name, version and date of creation of a product catalogue, the validity time, the
software by which the product catalogue has been generated. It can also contain data about the product
catalogue provider, the manufacturer, and in some cases also of the recipient of the product catalogue. To
distinguish product catalogue meta data from product data, a specific subject kind “catalogue” shall be used
to define properties specifying the meta data for product catalogues.
A catalogue subject C can be involved in the following types of relationships:
— isSubtypeOf: relating it to catalogue subjects that provide a more abstract view of C;
— hasPart: relating it to other catalogue subjects that represent the parts or components of C (see 4.4.2);
— hasBlock: relating it to block subjects that represent complex features of C.
Similar to product subjects, catalogue subjects can be independently instantiated.
EXAMPLE 3 The meta data of a product catalogue can consist of a name, a creation date and the name and the
phone number of the provider of the product catalogue. This can be represented in a data dictionary by a catalogue
subject with the properties “name” and “creation_date” and a block containing the data about the product catalogue
provider (see Figure 4).
ISO 16757-4:2025(en)
Figure 4 — Example of a catalogue subject with hasBlock relationship
4.3.3 Block
Properties are often collected in groups.
EXAMPLE 1 Often, sets of properties are combined because they are describing different aspects of one topic. For
instance, length, width, height, etc. can be grouped under the topic dimension.
Often, several properties describe a feature of a product. For understanding a data dictionary, this feature
should be represented by a subject that collects all properties of that feature.
EXAMPLE 2 Connections and ports are inherent parts of a product but each of them is described by a number of
properties.
EXAMPLE 3 In ISO 16739-1, properties are grouped in property sets.
To support such a grouping, the subject kind block is used. A block subject B can be involved in various types
of relationships:
— isSubtypeOf: relating it to a block subject that provides a more abstract view of B (see 4.4.1);
— hasPart: relating it to block subjects that build the parts or components of B (see 4.4.2).
Different to product subjects and catalogue subjects, a block subject shall only be instantiated in relationship
to a product or catalogue subject. It shall always be part of a product or catalogue subject, represented by a
hasBlock or a hasPart relationship.
EXAMPLE 4 Figure 5 extends Figure 2: The product subject “heater” gets a block subject “performance”, and this
block subject comprises performance related properties of a heater. The block subject is related to the product subject
“heater” by means of a hasBlock relationship.

ISO 16757-4:2025(en)
Figure 5 — Product subject “heater” with the block subject “performance” that collects performance
related properties
The following rules apply for blocks:
— any block subject in a data dictionary is part of another block subject, of a catalogue subject or of a
product subject, that means, any block shall be the target of a hasBlock relationship or it shall be the
target of a hasPart relationship;
— block subjects can belong to more than one block subject or product subject; that means, a block subject
can be the target of several hasBlock and hasPart relationships;
— block subjects in a data dictionary can be instantiated several times in a product catalogue.
EXAMPLE 5 A block subject “pin connector” can appear in a chip several times, describing each pin with a number
of properties.
4.3.4 Ports and in/outlets
4.3.4.1 Overview
Two features are important for any engineering system in the area of building services systems and are
used in practically any product in that area:
— ports are the interfaces of building services products to other building services products; any connection
of products in a system is made by means of the connection of ports of the two products;
— in/outlets are the interfaces of building services products that allow an interaction with the environment.
It is not the intention to describe ports and in/outlets with all its semantics in this document, but because
these features play such an important role for engineering tools, two special kinds of blocks have been
defined for them.
4.3.4.2 Ports
In the system model, product ports can be connected to ports of other products. They are used from and to
the product for the transfer of:

ISO 16757-4:2025(en)
— Substances (media)
— Solid (e.g. dust, fibres)
— Viscous (e.g. fire extinguishing foam)
— Liquid (e.g. potable water)
— Gaseous (e.g. natural gas)
— Energy
— Electrical (e.g. at power socket)
— Media bound (e.g. heat, compressed air, any enthalpy)
— Forces
— Fastening (e.g. for connection with wall mounting units)
— Power transmission (e.g. for connection with a joint lever)
— Signals
— Electrical (e.g. through alarm cable)
— Acoustic (e.g. through speaking tube)
— Optical (e.g. through glass fibre optics)
— Media bound (e.g. by pressure surge)
— Operation and control (e.g. by switch, by control panel)
In product catalogues, only the connectable ports of the product to ports of other products are relevant.
Internally connected ports are not of interest. This also applies to ports that have been connected by
combination with components or accessories.
For automated system planning, it is important to specify for each product port the possible matching
mating ports. This avoids incorrect connections or triggers warnings. Product ports that have no connection
to matching mating ports in the system model are to be assumed to have no function.
4.3.4.3 In/outlets
In the building services system model, there are products that have in/outlets to the rooms or the building
environment.
The in/outlets are used to transmit substances, energy or signals.
Unlike ports, which must each be connected to mating ports, the in/outlets are usually free. While ports
do not have calculatable dynamic properties, in/outlets have a direct influence on technical and geometric
properties of the media and signals due to their shape and dimensions. Figure 6 shows an example of a
device with several different in/outlets.

ISO 16757-4:2025(en)
Figure 6 — Example: different in/outlets at a single product
Openings are used for the transfer of:
— Substances (media)
— Solid (e.g. dust, fibres)
— Viscous (e.g. fire extinguishing foam)
— Liquid (e.g. potable water)
— Gaseous (e.g. ventilation air)
— Energy
— Media bound (e.g. heated air or water)
— Electromagnetic radiation (e.g. heat, UV-light)
— Signals
— Operation and control (e.g. by switch, by control panel)
— Acoustic (e.g. alarm siren)
— Optical (e.g. warning light)
4.4 Relationship types
4.4.1 isSubtypeOf
Relationships of type isSubtypeOf relate a subject to a more generic subject of the same kind.

ISO 16757-4:2025(en)
isSubtypeOf relationships build tree structures: A subject can be the root of a tree (it is not a subtype) or it
is a node in the tree (it is subtype of exactly one other subject). The cardinality of this relationship type is
therefore n : (0.1).
The isSubtypeOf relationship type includes property inheritance: If a subject S has a property P, then its
subtypes have also this property P.
EXAMPLE In Figure 2, two product subjects, called “convector” and “radiator”, are subtypes of a more generic
product subject “heater”. They are related to it by “is subtype of” relationships. That means that both convector and
radiator have implicitly also the properties length and height because they inherit them from heater. This is shown in
Figure 2 by the grey repetition of the inherited properties.
NOTE A relationship of type isSubtypeOf is normally not instantiated in a product catalogue. Subjects are normally
instantiated on the lowest level of the isSubtypeOf hierarchy, but their relationship to their more general subjects is
not instatiated. Thus, the isSubtypeOf relationship type is mostly relevant for the data dictionary level itself.
4.4.2 hasPart
Relationships of the type hasPart relate subjects to their parts or components. They can only be used
between subjects of the same kind.
The cardinality is n:m. A subject can have 0 parts, 1 part or several parts. It can be part of 0 or many other
subjects.
EXAMPLE 1 A central heating system can be defined as a system that consists of some components: for instance, it
can contain a burner, a boiler and a pump. In a data dictionary, such a central heating system is defined as a product
subject. In the same way, the burner, the boiler and the pump are product subjects. Then the subject “central heating
system” is related to its components by means of the hasPart relationship (see Figure 3).
EXAMPLE 2 Another example for a hasPart relationship is illustrated in Figure 7: The block subject “dimensions”
has two parts, the “inner dimensions” and the “outer dimensions”.
Figure 7 — hasPart relationship to relate a block to its parts
EXAMPLE 3 Many manufacturers provide cascades as products. A cascade consists of a number of products
of the same type (e.g. a set of burners) that are or can be connected in different ways in accordance with specific
requirements. In the data dictionary, the cascade of burners is represented by a subject “cascade of burners” that has
the subject “burner” as its part [see Figure 8 a)]. In a product catalogue, several burners are related to the instance of
the “cascade of burners” [see Figure 8 b)], and the way how these burners are connected can be defined by values of
respective properties of the “cascade of burners”.

ISO 16757-4:2025(en)
a) In the data dictionary b) In the product catalogue
Figure 8 — Cascades
NOTE It is important to understand the difference between the isSubtypeOf relationship and the hasPart
relationship. In an instance of the data dictionary, for example, in a product catalogue, the hasPart relationship must
be instantiated to connect the instances of the composite object with instances of the components (see Figure 8). The
isSubtypeOf relationship is never instantiated; normally only the leaves of the isSubtypeOf hierarchy are instantiated.
4.4.3 hasBlock
The hasBlock relationship relates a product subject or a catalogue subject to a block subject
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