ISO 23247-6:2026

• Abstract:

  This document specifies digital twin compositions in manufacturing by defining principles, describing methodologies and providing use-case examples of digital twin communication, aggregation and interoperation. This document identifies three kinds of digital twin composition (integrated, unified, and federated) and specifies requirements and step-by-step implementation guidelines for each kind. It provides structured approaches for composing multiple digital twins to support interoperability among digital twins developed by different parties, such as vendors, solution providers, and in-house developers. The document also includes illustrative use cases to demonstrate the practical application of the specified composition approaches.

• Status: Published
• Publication Date: 13-Jul-2026
• ICS: 25.040.40 - Industrial process measurement and control
• ICS: 35.240.50 - IT applications in industry
• Technical Committee: ISO/TC 184/SC 4 - Industrial data
• Drafting Committee: ISO/TC 184/SC 4 - Industrial data
• Current Stage: 6060 - International Standard published
• Start Date: 14-Jul-2026
• Due Date: 28-Sep-2026
• Completion Date: 14-Jul-2026

ISO 23247-6:2026 is an International Standard from ISO for automation systems and integration. It specifies digital twin composition for manufacturing - how multiple digital twins can be selected, connected, combined and coordinated so they work together as integrated, unified or federated composed digital twins. It is aimed at people who design, deploy and operate manufacturing digital twins across equipment, processes and supply chains.

What does ISO 23247-6:2026 specify?

ISO 23247-6:2026 specifies principles, methods and use-case examples for digital twin communication, aggregation and interoperation in manufacturing. Its focus is the composition of multiple digital twins developed by different parties, such as vendors, solution providers and in-house developers.

The document is organized into scope, normative references, terms and definitions, an overview of benefits, classification of composition kinds, lifecycle stages, requirements, a deployment procedure, and three informative annexes. As a framework document, it stays at the composition level and does not prescribe a single data format or communication protocol.

Annex	What it covers
Annex A	Integrated digital twin composition use case - robot arm with end effector
Annex B	Unified digital twin composition use case - cutting process
Annex C	Federated digital twin composition use case - using an AGV to deliver parts between automated assembly lines

What are the key requirements of ISO 23247-6:2026?

ISO 23247-6:2026 separates digital twin composition into three kinds and then ties each kind to a lifecycle and deployment procedure. In practice, the document helps you choose a composition style, define the data and interfaces, and plan how to test and operate the composed digital twin.

How does the standard classify digital twin composition?

Clause 5 classifies digital twin composition into integrated, unified and federated kinds. The choice matters because it drives how tightly the component digital twins are coupled and what kind of interoperability work is needed.

• Integrated DTC uses a common data model and centralized control. This suits cases where one composed digital twin needs a single, consolidated view and common protocols.
• Unified DTC keeps the individual models and schemas of the component digital twins, but connects them through an interoperability layer. This is useful when twins come from different sources and need translation or mapping between their data.
• Federated DTC lets component digital twins communicate directly with each other through peer to peer coordination. This fits decentralized environments where autonomy and dynamic joining or leaving are important.

Table 1 compares these kinds by compatibility, reliability, visualization, state monitoring, security, complexity and implementation challenges. For a reader, that comparison helps decide whether the system should be centralized, layered or peer based.

What lifecycle does the document use?

Clause 6 divides the lifecycle of a digital twin composition into specification, design, development and operation. That structure matters because the standard links each requirement to a stage, so teams can plan work in a practical sequence instead of treating composition as a one-step integration task.

• Specification defines the purpose, objectives, functional needs, non-functional needs, metadata and candidate digital twins.
• Design sets the composition strategy, including system architecture, data standards, communication protocols and deployment planning.
• Development identifies and connects component digital twins, creates interfaces, deploys middleware or APIs, tests, documents and stores the composed digital twin.
• Operation runs the composed digital twin alongside manufacturing, keeps data streams synchronized, updates the composition and establishes monitoring and maintenance.

What requirements does the standard set?

Clause 7 gives a checklist of requirements for the three composition kinds and maps them to lifecycle stages and functional entities in ISO 23247-2. In practice, this is the part to use when turning a concept into an implementation plan.

• Metadata shall describe the composed digital twin’s purpose, kind and functions. This helps teams catalogue and select the right twins.
• A catalogue shall include the functions, data models, technologies and interfaces of existing digital twins. This supports reuse and plug and play selection.
• Integrated DTC shall use a common data model across component digital twins. That keeps data formats, structure and semantics consistent.
• Unified DTC shall use an interoperability layer, data translation and mapping. That allows different models to work together without forcing one shared schema.
• Federated DTC shall use a decentralized network topology and standard peer to peer communication. That supports direct interaction and dynamic connection.
• Data synchronization, data governance, encryption, testing, documentation and maintenance are required across the lifecycle. These are the practical controls that keep the composed digital twin consistent, secure and maintainable.

How is deployment handled?

Clause 8 gives step-by-step deployment procedures for integrated, unified and federated digital twin composition. Each procedure follows the same broad pattern: define the representation of exchanged data, define the architecture for interoperability, then implement and validate the configuration.

For an engineer or buyer, this means the standard is not only conceptual. It also explains how to move from requirements to architecture, mappings, APIs, communication testing and operational monitoring.

What terms does ISO 23247-6:2026 define?

• Digital twin composition (DTC) - the process of selecting, connecting and combining digital twins to create a composed digital twin.
• Integrated digital twin composition - composition that uses a common schema and centralized control to combine component digital twins.
• Unified digital twin composition - composition that connects component digital twins while keeping their individual models and schemas.
• Federated digital twin composition - composition in which component digital twins communicate directly through peer to peer coordination.
• Component digital twin - a digital twin that takes part in a DTC.
• Composed digital twin - the digital twin produced by a DTC.
• Observable manufacturing element (OME) - an element with an observable physical presence or operation in manufacturing, such as personnel, equipment, material, process, facility, environment, product or supporting documentation.

Who uses ISO 23247-6:2026?

ISO 23247-6:2026 is used by manufacturing engineers, automation engineers, system integrators, production managers, IT specialists, process engineers and maintenance personnel who need multiple digital twins to work together. It is also relevant to vendors and solution providers building twins for robots, tools, processes, automated guided vehicles and production lines.

In practice, these roles use the document to decide how to combine existing digital twins, what data exchange strategy to adopt, how to map interfaces, and how to plan testing, monitoring and maintenance. Buyers and quality managers can use it to check whether a proposed digital twin architecture is centralized, layered or federated, and whether it matches the intended manufacturing use case.

Which standards are used with ISO 23247-6:2026?

ISO 23247-6:2026 is part of the ISO 23247 series and works with the other parts of that framework.

• ISO 23247-1:2021 - provides the overview, general principles, and the base terms and definitions used here.
• ISO 23247-2:2021 - provides the reference architecture and the functional entities used in Table 2.
• ISO 23247-3 - covers the list of basic information attributes for observable manufacturing elements.
• ISO 23247-4 - covers technical requirements for information exchange between entities within the reference architecture.
• ISO 23247-5 - covers requirements and guidance for using digital threads to connect lifecycle data to digital twins.
• ISO 11354-1 - is used in Clause 5 as the basis for the interoperability approaches behind the three composition kinds.

What does the ISO 23247-6:2026 document contain?

The document contains a classification of composition kinds, a lifecycle model, a requirements table and three deployment procedures. It also includes a comparison table for integrated, unified and federated DTC, which helps readers see trade-offs such as central control, interoperability layering and peer to peer coordination.

Figures 5, 6 and 7 show deployment procedures for the three composition kinds, while Figure 4 shows the lifecycle stages and Figure 3 summarizes the three kinds of composition. The informative annexes give worked use cases for a robot arm with end effector, a cutting process, and AGVs delivering parts between automated assembly lines, which makes the guidance easier to apply in design, testing and operational planning.

International
Standard
ISO 23247-6
First edition
Automation systems and
2026-07
integration — Digital twin
framework for manufacturing —
Part 6:
Digital twin composition
Systèmes d'automatisation et intégration — Cadre technique de
jumeau numérique dans un contexte de fabrication —
Partie 6: Composition d'un jumeau numérique
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviations . 1
3.1 Terms and definitions .1
3.2 Abbreviations .3
4 Overview and benefits of digital twin composition . 3
4.1 Concept of digital twin composition .3
4.2 Benefits of digital twin composition .5
5 Classification of digital twin composition . 5
5.1 General .5
5.2 Integrated digital twin composition .6
5.3 Unified digital twin composition .6
5.4 Federated digital twin composition .7
5.5 Summary of digital twin composition kinds .8
6 Lifecycle of a digital twin composition . 9
6.1 General .9
6.2 Specification stage of a digital twin composition .10
6.3 Design stage of a digital twin composition .10
6.4 Development stage of a digital twin composition .11
6.5 Operation stage of a digital twin composition .11
7 Requirements of digital twin compositions .11
8 Development procedure for digital twin composition .13
8.1 Overview . 13
8.2 Deployment procedure for integrated digital twin composition . 13
8.3 Deployment procedure for unified digital twin composition.16
8.4 Deployment procedure for federated digital twin composition .18
Annex A (informative) Integrated digital twin composition use case — Robot arm with end
effector .20
Annex B (informative) Unified digital twin composition use case — Cutting process .24
Annex C (informative) Federated digital twin composition use case — Using an AGV to deliver
parts between automated assembly lines .27
Bibliography .31

iii
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,
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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 documents 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 184, Automation systems and integration,
Subcommittee SC 4, Industrial data.
A list of all parts in the ISO 23247 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
Introduction
The ISO 23247 series defines a framework to support digital twins in manufacturing. A digital twin assists
with detecting events in manufacturing processes to achieve functional objectives such as real-time control,
predictive maintenance, in-process adaptation, big data analytics, process and manufactured component
validation, and machine learning. A digital twin monitors its observable manufacturing elements by
constantly updating and analysing relevant operational and environmental data as process/part changes.
This visibility into process and execution enabled by a digital twin enhances manufacturing operations and
business cooperation.
Manufacturing supported by implementing the ISO 23247 framework depends on the standards and
technologies available to model the observable manufacturing elements. Different manufacturing domains
can use different data standards. As a framework, this document does not prescribe specific data formats or
communication protocols.
The subject areas of the six parts of this series are defined below:
— ISO 23247-1: General principles and requirements for developing digital twins in manufacturing;
— ISO 23247-2: Reference architecture with functional views;
— ISO 23247-3: List of basic information attributes for the observable manufacturing elements;
— ISO 23247-4: Technical requirements for information exchange between entities within the reference
architecture;
— ISO 23247-5: Requirements and guidance to use digital threads for connecting manufacturing lifecycle
data to digital twins;
— ISO 23247-6: Requirements and guidance for performing digital twin composition.
Figure 1 shows how the six parts of the series are related.
Figure 1 — ISO 23247 series structure
Digital manufacturing involves many complex systems. One approach to managing manufacturing is to
create a digital twin encompassing all related assets. However, in practice, it is often impossible to build a
single digital twin that meets all the requirements for a factory floor or a supply chain. The digital twins of
each element in a complex system will need to be built independently and then integrated together using a

v
digital twin composition. With digital twin composition, individual digital twins can collaborate to enable
reusability and scalability, enabling individual digital twins to be used multiple times for various purposes,
rather than creating them from scratch every time.

vi
International Standard ISO 23247-6:2026(en)
Automation systems and integration — Digital twin
framework for manufacturing —
Part 6:
Digital twin composition
1 Scope
This document specifies digital twin compositions in manufacturing by defining principles, describing
methodologies and providing use-case examples of digital twin communication, aggregation and
interoperation.
This document identifies three kinds of digital twin composition (integrated, unified, and federated) and
specifies requirements and step-by-step implementation guidelines for each kind. It provides structured
approaches for composing multiple digital twins to support interoperability among digital twins developed
by different parties, such as vendors, solution providers, and in-house developers. The document also includes
illustrative use cases to demonstrate the practical application of the specified composition approaches.
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 23247-1:2021, Automation systems and integration — Digital twin framework for manufacturing — Part 1:
Overview and general principles
ISO 23247-2:2021, Automation systems and integration — Digital twin framework for manufacturing — Part 2:
Reference architecture
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in the ISO 23247-1, and the following
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/
3.1.1
digital twin composition
DTC
process of selecting, connecting and combining digital twins
Note 1 to entry: Digital twin composition produces a composed digital twin (3.1.6) using component digital twins (3.1.5)

3.1.2
integrated digital twin composition
integration of component digital twins (3.1.5) using a common schema
3.1.3
unified digital twin composition
unification of component digital twins (3.1.5) while maintaining individual models and schemas
3.1.4
federated digital twin composition
federated communication between component digital twins (3.1.5) with peer-to-peer coordination
3.1.5
component digital twin
digital twin that participates in a digital twin composition (DTC) (3.1.1)
3.1.6
composed digital twin
digital twin produced by a digital twin composition (DTC) (3.1.1)
Note 1 to entry: The composed digital twin can be integrated, unified or federated.
Note 2 to entry: A composed digital twin can be a component digital twin for another DTC which can be a different
kind.
3.1.7
observable manufacturing element
OME
element that has an observable physical presence or operation in manufacturing
Note 1 to entry: Observable manufacturing elements include personnel, equipment, material, process, facility,
environment, product and supporting documentation.
[SOURCE: ISO 23247-1:2021, 3.2.5, modified — “item” was replaced by “element”.]
3.1.8
data exchange
exchange of machine-interpretable files
[SOURCE: ISO 10303-2:2024, 3.1.212, modified — Note 1 to entry deleted.]
3.1.9
data translation
conversion of a data value from one code set to another
[SOURCE: ISO/IEC 5207:2024, 3.12, modified — EXAMPLE 1, EXAMPLE 2 and Note 1 to entry deleted.]
3.1.10
data model
graphical, lexical or combined representation of data, specifying their properties, structure, and
interrelationships
[SOURCE: ISO/IEC 11179-1:2023, 3.2.24]

3.2 Abbreviations
P2P peer to peer
API application protocol interface
KPI key performance indicator
MQTT message queue telemetry transport
HTTP hypertext transfer protocol
OPC-UA open platform communications unified architecture
FE functional entity
TCP transmission control protocol
OMG object management group
IDL Interface definition language
ROS robot operating system
URDF unified robot description format
DDS data distribution service
PLM product lifecycle management
AGV automatic guided vehicle
4 Overview and benefits of digital twin composition
4.1 Concept of digital twin composition
Digital twin composition (DTC) refers to the process of selecting, connecting and combining digital twins to
achieve a new goal with complex tasks through cooperation, as shown in Figure 2.

Figure 2 — Concept of digital twin composition
In manufacturing, thousands of OMEs can be connected in various ways to achieve specific purposes and
capabilities. Different DTC approaches address different interoperability needs of digital twins, which also
reflect interoperability across physical elements. These DTC approaches can include combining physical
elements into a single piece of equipment, managing complex processes involving multiple OMEs, establishing
manufacturing hierarchies, and enabling dynamic communication through peer-to-peer networks.
To enhance the reusability and development efficiency of digital twins, a DTC leverages a digital twin
repository containing various types of digital twins, which can be selected and combined based on
specific manufacturing use-case needs. By utilising existing digital twins from shop floors or suppliers, a
DTC reduces the need to create new digital twins from scratch. The availability of composed digital twins
accelerates application development and minimizes redundant effort, enabling manufacturers to benefit
from existing resources and expertise.

4.2 Benefits of digital twin composition
DTC enables the efficient development of composed digital twins with the following benefits.
— Improving efficiency:
A composed digital twin enables efficient monitoring and analysis of system performance by identifying
how changes in individual components affect the overall system.
— Increasing flexibility:
A composed digital twin allows easy testing and evaluation of various scenarios and configurations by
modifying its components without significant changes to the entire system.
— Enhanced decision-making:
A composed digital twin facilitates the identification and analysis of interactions among different
system components.
— Reusability:
A composed digital twin enhances the reusability of component digital twins by minimizing constraints
related to modelling languages, application platforms and operating environments.
— Cost reduction:
A composed digital twin reduces the cost associated with designing, developing and operating digital
twins by leveraging existing digital twins rather than creating new ones from scratch.
— Rapid deployment:
A composed digital twin supports fast instantiation and interconnection of digital twins for
manufacturing systems, thereby reducing deployment time.
— Customisation:
A composed digital twin supports plug-and-play capabilities, enabling digital twin components to be
formulated through simplified interfacing and configuration.
— Scalability and extensibility:
A composed digital twin supports scalable and extensible designs using individual digital twins as
modular building blocks to represent complex manufacturing systems.
5 Classification of digital twin composition
5.1 General
The DTC is classified into three kinds based on the interoperability approaches defined in ISO 11354-1:
a) integrated DTC: a kind of DTC that supports the integrated interoperability approach;
b) unified DTC: a kind of DTC that supports the unified interoperability approach;
c) federated DTC: a kind of DTC that supports the federated interoperability approach.
Figure 3 illustrates the three kinds of DTCs.

Key
fixed connection with a common data format
data exchanges with translation
dynamic connection over a P2P network
Figure 3 — Three kinds of digital twin compositions
5.2 Integrated digital twin composition
An integrated DTC consolidates all data and functionalities from its component digital twins. The
component digital twins shall conform to a common data model and meet standardized protocols. This kind
of composed digital twin employs a centralized control to manage data and processes, ensuring consistency
and uniformity. However, the implementation process for integrated DTC can become complex and less
flexible as the number of component digital twins increases.
This kind of DTC is suitable for scenarios requiring centralised control, such as a robot digital twin composed
of a robot arm digital twin and an end-effector digital twin.
The characteristics of an integrated DTC are listed below.
— Interoperability design:
Data and processes are combined and controlled in a centralized manner.
— Representation format:
Uniform representation using common data models and standardised protocols.
— Identification:
Local identifiers are assigned to component digital twins within the composed digital twin.
— Dependency:
Component digital twins are tightly coupled by using the same data model and control logic, aligned
with the same system to ensure consistency throughout the operation.
— Data exchanges:
Fully supported through a common data model and information system, enabling standardized and
consistent data flow across the component digital twins.
— Digital thread connection:
Digital threads of the component digital twin are merged into the composed digital twin.
5.3 Unified digital twin composition
A unified DTC makes connections between multiple component digital twins while allowing each to maintain
its individual model and schema. Middleware, application programming interfaces (APIs), or data integration
platforms facilitate data exchange and interoperability between component digital twins. Interoperability is
achieved through centralised coordination called an interoperability layer, that supports data mapping and
translation, enabling diverse digital twins to communicate without forcing a single standard data model.

This kind of DTC is ideal for cases where digital twins are developed independently but require data
sharing. For example, a process digital twin is composed of a product digital twin, a machine digital twin,
tooling digital twins and a material digital twin that are developed by various vendors and using different
standards.
NOTE In this example, ISO 10303-238 can be used for data exchange between the various vendors in the
interoperability layer.
Characteristics of a unified DTC are listed below.
— Interoperability design:
An interoperability layer supports centralised coordination for data mapping, translation and facilitates
communication between component digital twins.
— Representation format:
A composed digital twin is represented as independent component digital twins and an interoperability
layer that coordinates data exchanges component digital twins.
— Identification:
Shared identification services or protocols across component digital twins shall be used. Identifiers
should be unique at least across the shared services or protocols.
— Dependency:
Component digital twins are loosely coupled with centralised coordination enabled through shared
interfaces and common data models.
— Data exchanges:
Efficient and compatible data exchange is supported through an interoperability layer that handles data
translation and mapping between shared models.
— Digital thread connection:
Digital threads of component digital twins are connected via an interoperability layer while each digital
thread is independently maintained.
5.4 Federated digital twin composition
In a federated DTC, component digital twins interact directly with each other without the need for a
coordinating entity that manages data exchange in a centralised manner. Each component digital twin can
request or provide services and data to or from other digital twins in the network. Due to the absence of
central control, decentralised coordination is achieved among component digital twins, which operates
independently while communicating directly with others, enabling dynamic and flexible interactions.
In this kind of DTC, adding a new digital twin in composed digital twin can be easy if the new component
digital twin was anticipated or difficult if the existing component digital twins need modification.
This kind of DTC is well suited to decentralized environments where autonomy and direct interaction are
essential, such as automatic guided vehicles coordinating tasks across multiple worksites.
Characteristics of federated DTCs are listed below.
— Interoperability design:
Interoperability is achieved by decentralised coordination through flexible interfaces and mutual
adjustments between component digital twins.

— Representation format:
Component digital twins retain their independent formats, and a composed digital twin is represented
as a set of connections between these digital twins with distributed control logic across the network.
— Identification:
A unique identifier is assigned to each component digital twin, enabling discovery and connection with
specified peers.
— Dependency:
Each component digital twin controls its corresponding OME using its own data, models and control
logic for a specific system or application.
— Data exchanges:
Data is exchanged peer-to-peer based on agreements through standard interfaces.
NOTE These agreements include contracts information such as service interface, data schemas for inputs and
outputs, expected quality of service, and security policies.
— Digital thread connection:
Each component digital twin connects its own independent digital thread and updates data in response
to changes by the federated digital twin.
5.5 Summary of digital twin composition kinds
Table 1 summarises aspects for each kind of DTC.
Table 1 — Summary of digital twin composition kinds
Aspects Integrated DTC Unified DTC Federated DTC
Description Integration of component Unification of component Federated communication
digital twins using a common digital twins while maintain- between component digital
schema. ing individual models and twins that meet service re-
schemas. quirements.
Compatibility with Limited Moderate High
other digital twins
Integration is based on com- Allows component digital New component digital twins
mon data models. If a com- twins with different data can freely join the network
ponent digital twin does not models, but the composed without significant changes to
share a common data model, digital twin must be reconfig- the existing systems.
then an integrated DTC is very ured.
difficult to accomplish.
Reliability High Moderate Low
This is due to the centralized The interoperability layer Depends on peer-to-peer
control and common proto- manages interactions and interactions and network
cols. failures across digital twins in capabilities.
a centralized manner.
Visualization Provides a consolidated view Requires visualising the Difficult to provide a holistic
of the system since all compo- component digital twins and view as each component op-
nents are tightly integrated their interactions through the erates independently with no
into a single digital twin. interoperability layer. centralized control.
State monitoring A centralized system allows Monitoring relies on the Requires monitoring of in-
easy monitoring of all compo- implementation quality of dependent digital twins and
nents and their interactions. the interoperability layer and aggregating data dynamically
middleware to collect and dis- from peer-to-peer interac-
play the status of component tions.
digital twins.
TTaabbllee 11 ((ccoonnttiinnueuedd))
Aspects Integrated DTC Unified DTC Federated DTC
Security Centralized control ensures The interoperability layer Decentralized security pro-
robust protection within the ensures data protection and tocols focus on peer-to-peer
composed system. access control across the con- encryption and access control
nected digital twins. to protect data integrity.
Complexity High; Low; High;
Centralised control system Central management is less Ensuring consistent peer-to-
required. complex. peer communications requires
complex solutions
Challenges Ensuring new components can Ensuring seamless connectiv- Ensuring robust peer-to-peer
be integrated into the com- ity through the interoperabil- communication for new com-
posed digital twin. ity layer. ponents.
Examples Robot integrated with its end Automated process unified Production line federated
effector for process monitor- with a cutter to optimize per- with multiple AGVs for sched-
ing. formance. ule optimization and resource
allocation.
NOTE Annex A describes a DTC using the integration method. Annex B describes a DTC using the unified method.
Annex C describes a DTC using the federation method.
Composed digital twin implementations can use any combination of the three, including multi-level and
hierarchical structures. In such cases, a single kind of DTC can be applied consistently across all levels, or
different DTC kinds can be mixed, depending on the purpose, structure and interoperability characteristics
of each component digital twin.
6 Lifecycle of a digital twin composition
6.1 General
The lifecycle of a DTC is divided into four stages in this document as following:
— Stage 1, specification;
— Stage 2, design;
— Stage 3, development; and
— Stage 4, operation.
The four stages are shown in Figure 4. These stages do not cover the entire lifecycle. For example, additional
stages can address decommissioning and the reuse of digital twins.

Key
operation flow
information flow
connection between digital twins
interface between entities
Figure 4 — Lifecycle stages of a digital twin composition
6.2 Specification stage of a digital twin composition
This stage defines the purpose and objectives of DTC. The appropriate kind of DTC can be selected based on
specific requirements and constraints. This stage consists of the following sub-steps.
— Define purposes and objectives to be achieved through the DTC.
— Establish requirements based on the defined purposes and objectives. These include:
— functional requirements such as target functionalities, data types, interfaces;
— non-functional requirements such as performance criteria, key performance indicators (KPIs),
energy efficiency or physical location of the composed and component digital twins.
NOTE The physical location (e.g. on-site, edge computing or in the cloud) of a composed digital twin is not the only
factor in determining the kind of DTC. Modern communication technology can transfer large quantities of data very
rapidly. Other factors such as security and firewalls can be as important.
— Select the appropriate kind of DTC (integrated, unified or federated) to fulfil the requirements and meet
the objectives.
— Create metadata for the composed digital twin that specifies its purpose and associated requirements.
— Examine the catalogue of the existing digital twins, including their functionalities, data formats,
technologies and interfaces.
6.3 Design stage of a digital twin composition
This stage defines the composition strategy for digital twins, based on the requirements, and the selected
DTC kind identified in the previous stage. It consists of the following sub-steps.
— Define DTC methods based on the composed digital twin metadata, which describe the functional
requirements and selected the DTC kind. These include:
— a system architecture to support composed digital twin(s);
— common data standards and formats; and

— communication protocols for data exchange between digital twins.
— Establish a plan for deploying the composed digital twin. The plan should define implementation
sequences for deploying the composed digital twin, and include a testing and evaluation plan for each
deployment step.
6.4 Development stage of a digital twin composition
This stage identifies and selects appropriate component digital twins that align with the established
composed digital twin design. It consists of the following sub-steps.
— Establish data exchanges and data mappings.
— Create interfaces needed.
— Deploy component digital twins that will be joined to the composed digital twin.
— Deploy middleware and APIs to interconnect component digital twins.
— Conduct testing, verification, and validation.
— Complete documentation of the DTC.
— Store the composed digital twin in a repository and catalogue of digital twins.
6.5 Operation stage of a digital twin composition
This stage deploys and executes the composed digital twin in parallel with the corresponding manufacturing
operation. It includes the following sub-steps.
— Connect or combine the component digital twins with shared data models, simulation algorithms and
user interfaces based on the previously defined plan.
— Configure data streams between component digital twins and synchronize between corresponding
OMEs.
— Update the composed digital twin continuously during operation.
— Establish a monitoring and maintenance process.
7 Requirements of digital twin compositions
Composition of multiple digital twins has several requirements to ensure seamless integration, consistency
and functionality. Table 2 provides a checklist of requirements for the DTC kinds. In the table, each
requirement shall be mapped to relevant DTC lifecycle stages and the applicable functional entities of the
digital twin framework as defined in ISO 23247-2.
Table 2 — Requirements of digital twin composition
Requirements
Integrated Unified Federated
Related stage
DTC DTC DTC
Mapping to FEs defined in ISO 23247-2
Metadata shall be used to describe DTC requirements,
such as the DTC kinds and functionalities of the composed
  
Specification
digital twin.
Digital representation FE, user interface FE
A catalogue shall be deployed in the system to include
functionalities, data models, technologies and interfaces of
Design   
existing digital twins.
Interoperability support FE, plug and play support FE

TTaabbllee 22 ((ccoonnttiinnueuedd))
Requirements
Integrated Unified Federated
Related stage
DTC DTC DTC
Mapping to FEs defined in ISO 23247-2
A common data model shall be adhered to by all compo-
nent digital twins, ensuring consistency in data formats,
Design 
structures and semantics.
Presentation FE, digital representation FE
Data sharing policies shall be defined for data sharing
and access control to manage how data is shared between
  
Design
component digital twins.
Access control FE, data assurance FE
Standard communication protocols and APIs shall be im-
plemented to facilitate communication between compo-
Design, develop-
  
nent digital twins.
ment
Peer interface FE
A scalable architecture should be designed and developed
to allow for the composition of additional digital twins
Design, develop-
 
without significant reconfiguration.
ment
Plug and Play support FE
An interoperability layer solution such as middleware
shall be used to implement an interoperability layer that
Design, develop-
facilitates data integration and communication between

ment
different digital twins.
Interoperability support FE, data translation FE
A decentralized network topology shall be designed and
developed to allow digital twins to communicate directly
Design, develop-

with each other without a central coordinating entity.
ment
Peer interface FE
Standard communication frameworks or protocols for
Design, develop-
peer-to-peer messaging shall be used.

ment
Peer interface FE
Mechanisms for data mapping and transformation shall be
identified or developed to translate data from component
  
Development
digital twins into a common format.
Data translation FE
Data synchronization mechanisms shall be implemented
to ensure timely data updates in all component digital
Development   
twins.
Synchronization FE
Peer discovery mechanisms shall be implemented so that
the component digital twins can dynamically discover
Development 
each other.
Peer interface FE, plug and play support FE
A graphical user interface shall be developed to provide a
comprehensive system view.
Development   
User interface FE, digital representation FE
Testing and evaluation shall be used to ensure seamless
data exchanges and operation between the component
Development   
digital twins.
Maintenance FE, reporting FE
The composed digital twin shall be documented and
stored in a repository.
Development   
Presentation FE
TTaabbllee 22 ((ccoonnttiinnueuedd))
Requirements
Integrated Unified Federated
Related stage
DTC DTC DTC
Mapping to FEs defined in ISO 23247-2
The component digital twins should be updated or re-
placed with minimum impact on the composed digital
Operation   
twin.
Synchronization FE, plug and play support FE
Data governance policies shall be established to manage
data quality, ownership and lifecycle.
Operation   
Data assurance FE
Flexible interaction models should be used to allow com-
ponent digital twins to dynamically form and dissolve
Operation 
connections based on the needs and conditions.
Peer interface FE
Data encryption shall be used to protect data, ensuring
privacy and security.
Operation   
Security support FE
Processes for supporting data consistency and quality
across the component digital twins shall be implemented.
Operation   
Data assurance FE
Maintenance procedures shall be established to monitor
the performance of digital twin systems and regularly
update, improve and optimize the system addressing any
  
Operation
issues that arise.
Maintenance FE, analytic service FE
The network should be resilient to failures, ensuring that
the failure of one or more component digital twins does
Operation   
not disrupt the entire system.
Maintenance FE, Peer interface FE
8 Development procedure for digital twin composition
8.1 Overview
In this section, detailed deployment procedures for each kind of DTC are described based on defined
requirements. Deployment procedures are illustrated with swimlane diagram, which shows process flows
by separating development stages. In these diagrams, the blocks in each stage represent functional steps
associated with different interoperability aspects in the lifecycle process described in Figure 4.
These steps generally include:
— defining the representation of exchanged data such as common data models, standardised protocols, or
semantic mappings;
— design the architectural basis that enables interoperability such as integrated architecture,
interoperability layer, or peer-to-peer coordination design; and
— implementing and validating the configuration through data mapping, functional integration, and
communication testing.
8.2 Deployment procedure for integrated digital twin composition
The implementation of an integrated DTC is shown in Figure 5. The procedure begins by defining
requirements and cataloguing existing digital twins during the specification stage. The DTC design
stage focuses on the definition of a common data model, creation of integrated ontologies, and design of

an architecture for the integrated digital twin. The DTC deployment stage establishes data exchange
mechanisms between component digital twins and implements an integration method by creating data
mapping rules and integrating functional modules. As a result, the composed digital twin is deployed. In
the DTC operation stage, the composed digital twin is running with continuous updates and a structured
maintenance process to ensure reliability and performance. By following these steps, a composed digital
twin can be implemented to consolidate the strengths and capabilities of multiple digital twins into a single,
larger digital twin that provides comprehensive, consistent, and real-time insights and functionalities.
It is challenging that extending an integrated DTC requires development of new functionalities to support the
new digital twin component. These functionalities can include data integration logic, interface adaptation,
or reconfiguration of the central control system to accommodate the added component. Such development
efforts can be challenging when the new component has different data models, communication protocols, or
operational behaviours.
Depending on the specific purpose and requirements, certain steps may be omitted, such as integration of a
user interface when it is not required.

Key
control flow
information flow
Figure 5 — Deployment procedure for integrated digital twin composition

8.3 Deployment procedure for unified digital twin composition
Implementation of unified DTC is shown in Figure 6. Unifying multiple digital twins involves a structured
approach to ensure interoperability, consistency and efficient data exchange among different digital twins.
The process begins with defining requirements and cataloguing existing digital twins. In the design stage,
a system architecture of the interoperability layers with standard communication protocols is defined.
Also, since the interoperability layer is needed to coordinate between component digital twins, integration
plans in the DTC design stage are established. The DTC deployment stage focuses on developing the
interoperability layer, including middleware and data mapping schemas. By attaching component digital
twins to the interoperability layer and testing and evaluating the system, the composed digital twin can
be deployed with monitoring tools. In the DTC operation stage, the composed digital twin is updated to
adapt to changes and supported with a maintenance process to ensure long-term functionality. Following
these steps, a composed digital twin can be developed by leveraging the combined capabilities of individual
component digital twins for enhanced operational efficiency and decision-making.
It is challenging that extending a unified DTC requires the interoperability layer to support data translations,
schema mappings, and interface adjustments for the newly added component. This can be challenging
when the new component uses different data models, semantic structures, or communication proto
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