ISO/DIS 23247-5:2025(en)

ISO/TC 184/SC 4/WG 15

Secretariat: ANSI

Date: 2025-06-10

Automation systems and integration — Digital twin framework for manufacturing — Part 5: Digital thread for digital twin

Systèmes d'automatisation et intégration — Cadre technique de jumeau numérique dans un contexte de fabrication — Partie 5: Continuité numérique pour un jumeau numérique

© ISO 2025

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Contents

Foreword v

Introduction vi

1 Scope 1

2 Normative references 1

3 Terms and definitions 1

4 General 2

4.1 Concept of digital thread for digital twins 2

4.2 Digital twin utilisation of digital thread 3

4.3 Structure of a digital thread 5

4.4 Data flows enabled by digital threads 6

5 Digital thread entity 7

5.1 General 7

5.2 Digital thread ledger 7

5.3 Digital thread management 8

5.4 Digital thread metadata 8

5.5 Digital thread query and response 9

6 Digital thread life cycle 9

6.1 General 9

6.2 Digital thread creation 10

6.3 Digital thread maintenance 11

6.4 Digital thread obsolescence 12

7 Requirements on Digital Threads 13

7.1 Defining digital threads 13

7.2 Publishing digital threads 13

7.3 Searching for digital twins and digital threads 13

7.4 Support for accessing digital twin 14

7.5 Updating digital thread links 14

7.6 Digital thread management 14

7.7 Digital thread interoperability 15

Annex A (informative) Digital twin prototype, digital twin instance, and digital twin aggregate 16

A.1 Overview 16

A.2 Digital twin prototype 16

A.3 Digital twin instance 16

A.4 Digital twin aggregate 17

Annex B (informative) Scenarios between digital twin and digital thread 18

B.1 Finding digital twin from data store 18

B.2 Finding active digital twin 19

B.3 Adding new digital thread link to digital thread 20

B.4 Deprecating digital thread link from digital thread 21

B.5 Adding digital thread link across domains 21

B.6 Finding digital twin from different domain 23

Bibliography 24

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 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, Industrial 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.

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: Digital thread for digital twin;

— ISO 23247-6: Digital twin composition.

Figure 1 shows how the six parts of the series are related.

Figure 1 — ISO 23247 series relationships

This document describes how the digital thread supports the generation, implementation and transformation of digital twins in manufacturing.

In manufacturing, without digital threads, data from various stages of the product life cycle, such as design, production, quality management, and maintenance, usually remains isolated within individual digital twins. Such isolation causes data and information to be fragmented, leading to inefficiencies such as processing delays, information duplications, and disruption. These problems hinder manufacturers in conducting simulations and analyses with digital twins, as these functions depend on a continuous and integrated data flow. The absence of digital threads makes it difficult to associate various events and complicates time series analysis. The disconnection of information can cause delays or inhibitions in retrieving and processing data, leading to poor decision-making and difficulty in addressing issues as they arise.

Digital threads connect digital twins representing different aspects of the product life cycle. The scalability and adaptability of manufacturing are enhanced by digital threads that support seamless connections between digital twins for manufacturing processes across the life cycle, and production facilities across the extended enterprise.

This document defines the concept, requirements and operational characteristics of digital threads for digital twins in manufacturing.

Automation systems and integration — Digital twin framework for manufacturing — Part 5: Digital thread for digital twin

This document specifies how a digital thread enables the creation, connectivity, management, and maintenance of manufacturing digital twins across the product life cycle, including design, planning, production, and testing by defining principles, presenting methodologies, and providing use case examples.

There are no normative references in this document.

For the purposes of this document, the terms and definitions given in the ISO 23247 series, 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

digital thread

digital thread for digital twins

bidirectional, dependable, and trustworthy information that links digital twins with multiple data dimensions, including structure, behaviour, space, time, and lifecycle stages

Note 1 to entry: The linked digital twins can model design requirements, product models, manufacturing processes, inspection results, and verification data.

Note 2 to entry: This definition was derived from a definition developed by the Digital Twin Consortium.

3.2

digital thread entity

component that manages the digital thread for digital twins (3.1)

3.3

digital thread link

<digital twin> reference or pointer that connects one digital twin to another with digital thread metadata (3.6) to establish a relationship

Note 1 to entry: Depending on performance constraints, a digital thread entity (3.2) can link digital twins using data structure, URL, Universally Unique Identifier (UUID), DB query, or other mechanisms.

3.4

data store

<digital twin> repository that collects, organises, and manages content for the digital twin(s)

Note 1 to entry: Multiple data stores can be used for the digital twins depending on their roles (e.g., design, engineering, manufacturing, verification).

Note 2 to entry: Depending on system architecture, a data store can be implemented as a relational database, a graph database, cloud storage, a distributed ledger, or other suitable solutions.

3.5

digital thread ledger

<digital twin> repository of digital thread links (3.3) that identifies digital twins and their relationships with other digital twins

Note 1 to entry: In the simplest case, a digital thread ledger (3.5) contains a list of digital thread links (3.3) for the life cycle stages of one digital twin.

3.6

digital thread metadata

<digital twin> information about the digital thread link (3.3) between two digital twins

Note 1 to entry: The information can describe the purpose of the link, the date of the link, summarize an aspect of the digital twins in the link, etc.

Note 2 to entry: When the term “metadata” is not further qualified, then it is assumed to be digital thread metadata (3.6).

3.7

digital twin prototype

DTP

informational sets necessary to describe and produce a digital twin instance (3.8) that duplicates or “twins” the corresponding OME, including, but is not limited to, requirements, fully annotated 3D model, bill of materials (with material specifications), bill of processes, bill of services, and bill of disposal

Note 1 to entry: A digital twin prototype (3.7) is not linked to an OME

3.8

digital twin instance

DTI

fit for purpose digital representation of an observable manufacturing element (3.9) with synchronisation between the element and its digital representation

Note 1 to entry: When the term “digital twin” is not further qualified, then it is assumed to be a digital twin instance (3.8).

3.9

observable manufacturing elements

OME

element that has an observable physical presence or operation in manufacturing

Note 1 to entry: Observable manufacturing elements (3.9) include personnel, equipment, material, process, facility, environment, product, and supporting document.

[SOURCE: ISO 23247-1:2021(en), 3.2.5, modified — item changed to element]

The digital thread tracks the life cycle of digital twins over time. In manufacturing, a digital twin is a digital representation of an observable manufacturing element (OME). Before a digital twin exists, a product to be manufactured (product OME) is designed to meet requirements through a digital twin prototype. When the OME is in place, plans are made for its manufacture. When the necessary equipment has been allocated, the plans are applied to the OME. At this stage, the digital twin prototype becomes a digital twin instance. When manufacturing is finished, the product is tested and inspected. If it is judged ready, the product is delivered to a customer.

NOTE Detailed descriptions of digital twin prototype, digital twin instance, and digital twin aggregate are in Annex A.

As the product OME moves from design idea to delivery, the digital twins made at each stage are linked together. These links enable upstream processes to observe their impact on the final product and allow downstream processes to access information that affected the upstream processes. The linked digital twins can model requirement data, product data, manufacturing process data, inspection data, and verification data. The digital thread establishes a chain of custody for the digital twins so that users and applications can inspect their evolution from design through planning, manufacturing, and inspection. With this information, manufacturers can optimise their processes, reduce waste, and adapt effectively to changes, ultimately driving innovation and competitiveness.

The digital thread enables diverse applications to access information within the context of the appropriate digital twin, ensuring seamless data flow across the product life cycle. In the engineering stage, the digital thread connects design digital twins with simulation results, enabling validation and optimisation before production starts. In the manufacturing stage, the digital thread links the design digital twins and the manufacturing digital twins to ensure products are manufactured as designed. In the validation stage, the digital thread integrates testing, manufacturing, and design digital twins to facilitate problem analysis and quality improvements. Beyond production, the digital thread supports predictive maintenance by combining multiple digital twins into digital twin aggregates that model operational performance and historical trends for proactive decision making. The digital thread facilitates multi-manufacturer collaboration and supply chain optimisation through digital twin sharing.

The content of a digital twin is derived from information systems that support and enable the OME. This content is contextualised for traceability, allowing users to monitor the status of the product OMEs and thereby enhancing the visibility of the production process.

Figure 2 shows how digital twins utilise digital threads to integrate and interpret manufacturing data from various sources. Life cycle data and information are often siloed, logically or physically separated. The digital thread enables connection to digital twins from disparate data sources. Digital twins use digital threads to obtain base information about the manufacturing process and model components. This allows data analysis and optimisation to represent the characteristics of the target OME. By connecting and contextualising life cycle data, the digital thread facilitates continuous monitoring and improvement of the OME. This process enhances decision-making, optimises production processes, and fosters collaboration throughout the supply chain, ultimately driving improvements in product design, innovation, and overall visibility.

In Figure 2, the lower left box (i.e., life cycle data of digital twins) shows the existing information system, and the upper left box (i.e., digital thread of life cycle data) shows that digital twins are realised from those systems and linked by the digital thread. The middle figure (i.e., digital twins in manufacturing) shows a subset of the digital twins in a digital twin entity for various life cycle stages. Changes to the OME are mirrored in the digital twins using the infrastructure described in ISO 23247-1 to ISO 23247-4. Some of the information is aggregated for further analysis. New digital twins are linked to the digital thread for usage by subsequent manufacturing processes.

Figure 2 — Digital twin utilisation of digital threads

The following are different kinds of the life cycle data shown on the lower left of Figure 2.

— Contract data are data from agreements, terms, and conditions between stakeholders or partners. This data is the foundation for initiating the life cycle by establishing project goals and expectations.

— Requirement data are data from the functional and technical requirements of the product or system. It serves as a base for design, development, and testing.

— Design and engineering data are the physical and functional characteristics of the product, including CAD models, schematics, and engineering specifications used during the design and development stages.

— Supplier data is information related to external suppliers, including materials, components, and supply chain logistics. This data is essential for coordinating with external vendors.

— Production data are data from manufacturing processes, which include assembly instructions, machine parameters, and real-time production performance metrics.

— Test data are the results from product testing, validation, and quality assurance. It specifies whether the product meets its specifications and identifies any defects or issues.

— Operation and maintenance include usage statistics, performance monitoring, failure analysis, and maintenance logs.

— Legacy data is the historical data from previous projects, systems, or versions.

The use of a digital thread by the digital twin has many benefits shown on the right panel of Figure 2. The primary benefit is to support continuous enhancement and innovation within manufacturing, which leads to the enhancement of efficiency in product design and development and improved decision-making. Furthermore, the digital thread allows for a comprehensive view of the product life cycle, which results in better traceability, quality control, and the ability to predict and address issues proactively. The digital thread can provide information for the digital twin to enhance visibility, which leads to an enhancement in cooperation and supply chain collaboration, and overall productivity in manufacturing.

Figure 3 depicts the structure of a digital thread that consists of a series of digital twins and digital thread links. Each digital twin has units of data with a unique identifier and other descriptive information that represents an OME. These unique identifiers serve as the building block of the digital thread, as they are the means for identifying digital twins. A digital thread link is a reference or pointer that connects one digital twin to another to establish a relationship. Organising these links constitutes a digital thread that enable traceability of data flow and transformation across different stages of the product life cycle.

Key

Figure 3 — Representative example of a structure of digital threads for digital twins

The digital thread links shown in Figure 3 include the following:

— D1 E1 is a link between the digital twin prototype in the design stage (D1) and the digital twin prototype in the engineering stage (E1), representing the relationship between the digital twins of the initial design and the engineering specification;

— E1 M1 is a link between E1 and the digital twin instance in the manufacturing stage (M1), representing the relationship between the digital twins of the engineering specification and the product in the manufacturing stage, with OME1 assigned to M1 for synchronisation;

— E1 M2 is a link between E1 and the digital twin instance in the manufacturing stage (M2), representing the relationship between the digital twins of the engineering specification and the product in the manufacturing stage, with OME2 assigned to M2 for synchronisation.

The digital threads shown in Figure 3 are as follows:

— D1 E1 M1 V1 is a digital thread that is used to trace the life cycle of OME1 from design to validation;

— D1 E1 M2 V2 is a digital thread that is used to trace the life cycle of OME2 from design to validation;

— D2 E2 is a digital thread that ends at the engineering stage, which means the design has not yet moved to manufacturing.

Figure 4 illustrates the possible data flow facilitated by the digital thread in Figure 3. The digital thread enables seamless utilisation of information across the design, engineering, manufacturing, and validation stages between digital twin prototypes, digital twin instances, and observable manufacturing elements.

Key

D₁, D₂ digital twin prototypes in the design stage

E₁, E₂ digital twin prototypes in the engineering stage

M₁, M₂ digital twin instances in the manufacturing stage

V₁, V₂ digital twin instances in the validation stage

possible data flow

Figure 4 — Examples of data flows enabled by digital thread

Many flows are possible because each digital twin can be a composite of many other digital twins. For example, a manufacturing process digital twin can be composed of a workpiece, fixture and cutting tools, but for simplicity, they are shown as one twin in this introduction. The following are some examples of data flows that are possible from Figure 4.

— For data flow from D1 to M1, a digital twin in the manufacturing stage (M1) uses D1 to understand assembly constraints or critical dimensions that needs to be maintained during production. This is implied by a digital thread D1 E1 M1. A similar use case can be applied to the data flow from D1 to M2.

— For data flow from M1 to D1, a digital twin in the design stage (D1) uses M1 to detect production efficiency, CNC tool wear, or machining error to improve design for manufacturability and reduce production cost. This is implied by a digital thread D1 E1 M1. A similar use case can be applied to the data flow from M2 to D1.

— For data flow between D1 and OMEs, D1 communicates with OMEs to acquire operational data such as actual machining performance or detect production efficiency. This is implied by a digital thread D1 E1 M1 or D1 E1 M1 V1.

The digital thread entity consists of two components:

1) a digital thread ledger consisting of logical digital thread link attributes defining the data relationship between digital twins and

2) an agent that facilitates access to the digital twins, and provides for a historical record of digital thread activity in response to service requests.

Key

D₁, D₂ digital twins of design prototypes

E₁, E₂ digital twins of engineering prototypes

M₁, M₂ digital twins of product OMEs in manufacturing

V₁, V₂ digital twins of product OMEs in testing

digital thread link that connects digital twins

digital thread

S_D data store for the design digital twins

S_E data store for the engineering digital twins

S_M data store for the manufacturing digital twins

S_V data store for the validation digital twins

digital thread query and response

{-} digital thread metadata

Figure 5 — Digital thread and digital twin entities

Figure 5 shows the elements and the interactions within the framework of the digital thread shown in Figure 3. Each digital twin (D₁, D₂, E₁, E₂, M₁, M₂, V₁, V₂) is a representation related to the product OME in a specific stage of the product life cycle, including design, engineering, manufacturing, and validation. Corresponding to each stage, digital twins are stored in designated data stores (S_D, S_E, S_M, S_V) as shown in Figure 5.

The digital thread connects these digital twins through digital thread link that establish a logical relationship across the product life cycle stages. These links enable end-to-end digital thread traceability and continuity of information as the digital twins are transitioned, evolved, or composed.

The digital thread ledger is a repository that stores digital thread links that identify digital twins and their relationship with other digital twins. It maintains entries for each digital thread including the sequence of digital twins represented by the digital twin identifiers, references to the corresponding data stores, and digital thread metadata that describes contextual and operational meaning to each digital thread link. It is managed by the digital thread entity.

The digital threads stored in the digital thread ledger enable traceability of digital twin interactions and serves as a foundation for the digital thread entity to process and respond to queries from digital twins.

The digital thread ledger can be implemented using various technologies, including relational databases, graph models, distributed ledgers, or other data structures capable of supporting relationship-based queries.

The digital thread entity facilitates the definition, operational use, and management of digital threads used by digital twins. It provides an administration function to support a historical registry of the digital thread usage.

The digital thread entity enables:

— receiving and processing of queries from digital twins seeking related digital twins;

— searching the digital thread ledger to identify relevant digital twins and the associated digital thread links;

— responding to queries by providing digital twin identifiers and corresponding access paths to the requesting digital twin;

— updating the digital thread ledger when changes occur to the digital thread links between digital twins.

Digital thread metadata (metadata) enhances the traceability, interpretability, and usability of the digital thread. It is possible to construct a digital thread using only the source and destination digital twin identifiers. However, including the metadata provides additional contextual and operational meaning to each digital thread link. This facilitates efficient query responses and improved traceability through identifying, filtering, and selecting the most relevant digital twins for a given query.

Advantages of using metadata include:

— assist selecting the required digital twin;

— prevent applications from loading irrelevant digital twins;

— enable intelligent searching and large language training;

— determine the utilisation of a digital twin;

— add enterprise specific information.

The metadata can include, but is not limited to, the following:

— digital thread link type;

NOTE Link type is a relationship between digital twins such as transition, composition, or evolution.

— descriptive information explaining the purpose of the digital thread link;

— identifiers of the source and destination digital twins;

— timestamp, versioning, and other administrative data;

— relevant attributes of domain-specific data.

The following examples describe metadata for the digital twins Figure 3 and Figure 5.

— D₂E₂{-}: metadata from D₂ to E₂ to capture the updated version number of the design modification.

— E₁M₂{-}: metadata from E₁ to M₂ to document the serial number of the manufactured part.

— M₂V₂{-}: metadata from M₂ to V₂ to indicate successful completion of the quality control validation.

A digital thread query and response is an operational interface between a digital twin entity and a digital thread entity. This interaction enables a digital twin to retrieve relevant information about other digital twins that are connected through a digital thread, supporting traceability, decision-making, and contextual awareness throughout the product life cycle.

A digital thread query and response consists of the following steps:

— query initiation: the digital twin entity sends a query to the digital thread entity to search for related digital twins;

— query processing: the digital thread entity searches the digital thread ledger to find the digital twin requested by the digital twin entity;

— response: the digital thread entity provides a response containing the identifier(s) of the discovered digital twins.

NOTE 1 Queries are submitted through API, database interface, web portal, or messaging protocol such as MQTT.

NOTE 2 Scenarios on how the digital threads are used by the digital twin are in Annex B.

The digital thread facilitates seamless access and exchange of information between manufacturing digital twins. This enables a continuous data flow across the product life cycle, as shown in Figure 6.

Key

digital thread link in digital thread ledger

data or information as part of the product life cycle

standard as an enabler for the digital twin

data store interface

AP ISO 10303

Figure 6 — An illustrative example of digital threads for a product life cycle

The need for a digital thread increases with the number of diverse and distributed systems working together. In many cases, a digital twin is composed of component digital twins that are designed and maintained by suppliers. Therefore, an integrated system of systems approach is needed to understand, design, produce, and sustain digital twins.

The digital thread entity shall create a digital thread by following procedures that include, but are not limited to:

1) define structure: select or develop the data model for the metadata, and reference methods for implementing the digital thread links to ensure traceability and interconnectivity;

2) set access and utilisation control: to regulate who can read, write, and modify digital thread data to ensure secure data exchange and maintain integrity of the digital thread;

3) adopt usage control rights: inherit security permissions and ownership rights from the source digital twin to prevent unauthorised modification and misuse of digital twin data;

4) register digital thread: assign unique identifiers and classify threads based on various factors, such as life cycle stages, product or components, process types, time-based versions, compositions, etc.;

5) add to digital thread ledger: digital thread links are added to the digital thread ledger in response to application requests. Digital threads are constructed on demand from the links by the digital thread entity in response to application queries.

The digital thread entity facilitates the definition and utilisation of digital thread links and relationships by applications. Graph models can represent the characteristics and nature of these digital thread links. Digital thread links are assessed based on qualitative attributes such as adherence to data standards, retention of data integrity, accuracy of the data, timeliness of data interface and interaction, and digital thread link associations.

Based on these attributes, the digital thread ledger is an aggregate of various factors such as standardisation, efficiency, data quality, elasticity and complication of the digital twin and its links. A standardisation factor represents the percentage adherence of data standards for each digital twin and digital thread link. Whereas an efficiency factor measures the digital twin data and the link transfer either from one life cycle stage to another, or digital twin to digital twin interactions. The elasticity factor signifies the architectural scalability of the digital thread, whereas the complication factor embodies the number of digital twins.

There are many different ways and means of representing a digital thread. One of the approaches is visualising a digital thread by using a dimensional graph model. A notional digital thread is described as a network of digital twins and digital thread links as shown in Figure 6. Geometrically, a digital twin is represented as a circle with relevant industry standards applicable to a particular life cycle stage. The digital thread link is the red double line that connects the digital twins to establish a relationship between the digital twin that traces the flow of data, process, and decisions. A digital thread is represented by the trace formed by the digital thread links that illustrate how data and processes evolve and interact throughout the product life cycle.

The relevant industry standard(s) identified are the best practices, data models, and interoperability standards that enable digital twins. The standards ensure that digital twins adhere to consistent formats, terminology, and structure.

The following subsections describe product life cycle stages and identify standards in example as possible enablers.

This stage defines the project objective and performance expectation of a new product by focusing on market needs, customer requirements, functional requirements identified, project plan, etc.

NOTE Standards that can be used in this stage include ISO 10303-1 and ISO 23247-1.

This stage defines the initial design and feasibility, such as a 3D model, sketches, and prototypes.

NOTE Standards that can be used in this stage include ISO 10303-209, ISO 10303-242, and ISO 14306.

This stage finalises the engineering specification of the product, including material selection, tolerance definitions, and manufacturing constraints, etc. It ensures that the design is prepared for production.

NOTE Standards that can be used in this stage include ISO 10303-210, ISO 10303-233, and ISO 13584.

This stage builds prototypes for functional testing to validate the design against requirements using test data and simulations. It ensures that the product meets design and functional requirements.

NOTE Standards that can be used in this stage are ISO/IEC 17025 and ISO 13399.

This stage develops the manufacturing process, including the process plan, supply chain logistics, quality control parameters, CNC programming, and factory setup.

NOTE Standards that can be used in this stage include ISO 10303-235 and ISO 23247-4.

This stage manufactures products through process execution, quality control, and performance tracking.

NOTE Standards that can be used in this stage include ISO 10303-238, IEC 62264 series, and ISO 22400 series.

This stage inspects manufactured products before being delivered to the customers.

NOTE Standards that can be used in this stage include ISO 10303-239, ISO 23952, and ISO/IEC 17360.

This stage tracks and monitors how products are used and their performance in the field. Performance of the product is enhanced through feedback, software updates, and remote diagnosis.

NOTE Standards that can be used in this stage include ISO/IEC 30141 and IEC 62541 series.

This stage provides customer support, troubleshooting, and predictive and preventive maintenance.

NOTE Standards that can be used in this stage include ISO 13374 and ISO 55000.

A digital thread for digital twins becomes obsolete when all its connected digital twins are missing, or discontinued because their OMEs are no longer being tracked for synchronisation.

The following are considerations that contribute to the persistence of a digital thread:

— reusability;

— regulatory or contractual retention requirements;

— inter- and intra-enterprise utilisation;

— functional integration with one or more processes or systems.

Additional consideration must be taken into account for the intended use and anticipated persistence of the digital thread.

The following rules can be used for determining how to handle obsolete digital threads:

— retain if: the digital thread is expected to be used for future reference, regulatory retention, collaboration, or has dependencies with other systems;

— archive if: the digital thread has historical value but is no longer actively used;

— terminate if: the digital thread is obsolete, redundant, or has no ongoing dependencies.

The following are the requirements for defining digital threads.

1) The digital thread entity shall maintain the digital threads’ information.

2) The digital thread information shall include, but is not limited to, the following:

— thread ID;

— timestamp of creation;

— timestamp of each modification;

— digital twin identifiers for each digital thread link;

— data store identifiers that can locate the digital twin;

— digital thread metadata for each digital thread link.

3) The digital threads’ information shall be kept in a digital thread ledger.

4) The digital thread entity shall update the digital thread ledger when a link is updated.

5) The digital thread entity shall log all modifications made to the digital thread ledger, including creation, updates, and deletions.

6) The digital thread entity shall maintain the integrity of the digital thread ledger by applying mechanisms such as digital signatures, cryptographic hashes, checksums, or other appropriate technologies.

The following is the requirement for the publication of digital threads.

1) The digital thread entity shall publish information about the digital threads it manages.

2) The digital thread entity shall publish identifiers for the digital twins it manages.

3) A digital twin shall use the published information to find digital twins and digital threads.

NOTE Publication can be made using webpages, messaging protocols such as MQTT, database access services, and cloud storage services.

The following are the requirements for searching.

1) The digital thread entity shall provide a method to find relevant digital twins and digital threads.

NOTE 1 Methods used can include an API, web portal, database query interface, messaging protocols, etc.

2) The digital thread entity shall process the query and search the digital thread ledger to locate the requested digital threads or digital twins.

3) The digital thread entity shall use the digital thread metadata to identify the most relevant digital twin that satisfies the request criteria.

4) The digital thread entity shall validate a requestor to ensure it has the authority to access the requested digital twin and its relevant data store.

5) The digital thread entity shall return to the requestor identifier(s) for the requested digital twin.

NOTE 2 Identifying mechanisms such as UUID, GUID (Globally Unique Identifier), and IRDI (International Registration Data Identifier) can be used.

6) The digital thread entity shall return status codes, or error messages for failed queries, or unauthorised access attempts.

7) The digital thread entity shall log all requests and corresponding responses related to digital twin queries.

NOTE 3 The recorded log information can support the analysis of query patterns, improve digital thread configuration, increase retrieval effectiveness, optimise query processing, and enhance traceability.

The following are requirements for supporting access to digital twins.

1) The digital thread entity shall provide a method for digital twins to access the data store of other digital twins or to communicate with other digital twins.

2) The digital thread entity shall enable digital twins to access additional information on other digital twins.

3) The digital thread entity shall implement security measures to ensure information about the digital thread is not provided to unauthorised digital twins.

The following are the requirements for updating digital thread links.

1) The digital thread entity shall create, delete, and update the digital thread links between digital twins.

2) The digital thread entity shall ensure that the source digital twin is newer than the destination digital twin.

3) The digital thread entity shall be notified by the connected digital twins of any changes to the digital thread link.

The following are the requirements for digital thread management.

1) Upon creation of a new link, the digital thread entity shall decide whether to create a new digital thread or add a new link to an existing digital thread.

2) Upon deletion, the digital thread entity shall decide whether to delete the digital thread link or deprecate the digital thread link.

3) Upon deletion of the digital thread link, the digital thread entity shall decide whether to split the digital thread into two separate digital threads or disconnect the digital twin from the digital thread.

4) The digital thread entity shall ensure timely data interactions and maintain accurate association in the digital thread links.

The following are the requirements for digital thread distribution between digital thread entities.

1) Traceability across digital twin entities shall be enabled without requiring centralised control.

2) Each digital thread entity shall support interoperability with other digital thread entities to enable traceability across a supply chain.

1. 
   (informative)
   
   Digital twin prototype, digital twin instance, and digital twin aggregate
   1. Overview

According to Grieves and Vickers,^[28] digital twins are categorised into digital twin prototype (DTP), digital twin instance (DTI), and digital twin aggregate (DTA). All of them can utilise digital threads.

• 1. Digital twin prototype

A DTP is an informational set necessary to describe and produce a DTI that duplicates or “twins” the corresponding physical counterpart. It is a conceptual design for the DTI and can include, but is not limited to, requirements, a fully annotated 3D model, a bill of materials (with material specifications), a bill of processes, a bill of services, and a bill of disposal. The DTP includes necessary parameters and characteristics that describe the intended OME. However, it is not linked to a specific OME. It enables rapid replication of digital twins as corresponding physical instances are created in production. The DTP represents the intended functionality, behaviour, and characteristics of the OME in the design stage. It enables stakeholders to observe and analyse how the DTP responds to different conditions, inputs, and use cases. It is used in testing and validating the design concept or digital model. It helps to identify potential problems or improvements of the design model at the early stage of manufacturing or development.

The DTP uses the digital thread to acquire information from the downstream life cycle stages, enabling design improvement and ensuring manufacturing feasibility. The digital thread links simulation, test results, and design requirements to ensure all modifications remain traceable and propagated throughout the product life cycle.

• 1. Digital twin instance

A DTI is a digital representation of an OME with synchronisation between the element and its digital representation. It is derived from the DTP. The DTI represents the design features, manufacturing details, operational behaviour, and performance of its corresponding OME. The DTI collects and integrates operational data from sensors or other sources to make available accurate and up-to-date views of the OME. The DTI monitors its OME by actively tracking the updates. The DTI is aligned with the entire life cycle of the OME it represents, which means it is no longer needed when its counterpart is decommissioned. However, it is possible to maintain some information on the DTI, which is needed as a reference for the future development of the new OME.

By presenting the current status of the OME, the DTI can include detailed simulations for use to predict future behaviour, analyse potential problems, or optimisation in supporting decision-making processes related to the management, maintenance, and disposition of the connected OME.

The DTI uses digital threads to inherit information from DTP to ensure that DTI accurately reflects the OME specification and intended design functionalities of the OME. The DTI continuously updates the digital thread to reflect any changes to the OME, ensuring synchronisation with the OME. The accurate representation of the OME is essential for predictive maintenance, performance optimisation, and fault detection. The DTI provides prompt operational data and performance metrics back to the digital threads. The DTI communicates with other digital twins through the digital thread to ensure that the DTI follows the quality requirements and operational criteria of the intended OME.

• 1. Digital twin aggregate

A DTA is an accumulation of digital information gathered from one or more DTIs at specific intervals or event-based either synchronously or asynchronously. The DTA provides a comprehensive view of the collective behaviour and performance of multiple DTIs.

NOTE Digital twin aggregate is different from digital twin aggregation. Digital twin aggregation is a process of integrating multiple DTIs of different DTPs. It is also known as digital twin composition. See ISO 23247-6.

A DTA represents the collective behaviour and operation of the DTIs. The gathered data are combined to identify patterns, correlations, and performance of the DTIs. The DTIs can be from different vendors or systems, and DTAs can get an aggregated view of the multiple DTIs, enabling analysis of the performance and interaction as a group. The DTA provides a detailed understanding of DTIs, which can be used to support decision-making.

A DTA uses digital threads to acquire aggregated data from multiple DTIs to capture operational trends and failure patterns to be fed back for design and manufacturing improvements. The digital thread serves as a single source of truth, ensuring consistency, accuracy, and reliability of data collected from DTIs. By analysing aggregated data, the DTA generates analytics for performance analysis, predictive maintenance, and future design improvements, enabling enhanced decision-making. The digital thread provides a continuous flow of digital twin data across an OME’s life cycle, ensuring that the DTA can access all necessary information for effective decision support.

1. 
   (informative)
   
   Scenarios between digital twin and digital thread
   1. Finding digital twin from data store

Key

digital twins of stage A

digital twin of stage I

digital twins of stage N

23247- digital thread

S_A data store for the digital twins of stage A

S_I data store for the digital twin of stage I

S_N data store for the digital twin of stage N

{-} digital thread metadata

Figure B.1 — Finding information about the digital twin from the data store

Figure B.1 is an operational scenario for finding information about the digital twin from the data store.

The scenario is as follows.

Step 1. Query request: a digital twin () initiates a query to the digital thread entity to locate a specific digital twin that has the details of its model design. The digital twins already know about the digital thread entity. The methods of querying digital threads depend on the technology implemented.

Step 2. Search: the digital thread entity searches the digital thread metadata in the digital thread ledger to locate the digital twin that has the information of the model design of the digital twin (). Digital thread entity identifies the digital twin () as the requested digital twin.

Step 3. Query response: the digital thread entity responds with identifier(s) of the requested digital twin () and other information corresponding to the data store. The response can be one or more identifiers of digital twins.

Step 4. Retrieve digital twin from data store: using the query response, the digital twin () retrieves necessary information of the digital twin () from the selected data store. The digital twin () needs to have appropriate permissions to access the requested digital twin ().

• 1. Finding active digital twin

Key

Figure B.2 — Finding information from an active digital twin

Figure B.2 is an operational scenario for finding digital twin to make direct communication.

The scenario is as follows.

Step 1. Query request: a digital twin () initiates a query to the digital thread entity to locate a specific digital twin that has the details about the colouring options.

Step 2. Search: the digital thread entity searches the digital thread metadata in the digital thread ledger to locate the digital twin that has the information of the colouring details of the digital twin (). Digital thread entity identifies digital twin () as the requested digital twin.

Step 3. Query response: the digital thread entity responds with identifier(s) of the requested digital twin () and other information for direct communication.

Step 4. Communicate with digital twin: using the query response, the digital twin () communicates with digital twin ().

• 1. Adding new digital thread link to digital thread

Key

Figure B.3 — Adding new digital thread link

Figure B.3 is an operational scenario for adding new links between digital twin () and digital twin (). Note that a new link of digital twin () is added in the digital thread ledger.

The scenario is as follows.

Step 1. Reference made: the digital twin () references or is created from digital twin ().

Step 2. Link created: a link is created between the digital twin () and the digital twin ().

Step 3. Updates to digital thread: the digital twin () informs the digital thread entity that a new link has been created with digital twin (). Identifiers for both digital twin () and digital twin (), digital thread metadata indicated as {#j} are sent to the digital twin entity.

Step 4. Updates to the digital thread ledger: the digital thread entity updates the digital thread ledger to add a new link between the digital twin () and the digital twin () along with the digital thread metadata {#j}. The addition of a new link can result in the extension of an existing digital thread or the initiation of a new digital thread.

• 1. Deprecating digital thread link from digital thread

Key

Figure B.4 — Deprecating unnecessary digital thread link

Figure B.4 is an operational scenario for deprecating unnecessary digital thread link.

The scenario is as follows.

Step 1. Reference not needed: the digital twin () and digital twin () determine that the existing link is no longer valid. An example of such a case is a change of business partners, replacement of parts, etc.

Step 2. Remove digital thread link: the digital thread link between digital twin () and digital twin () is removed.

Step 3. Updates to the digital thread: the digital twin () or digital twin () informs the digital thread entity that the digital thread link is no longer needed.

Step 4. Updates to the digital thread ledger: the digital thread entity updates the digital thread ledger to deprecate the digital thread link between digital twin () and digital twin () by updating the digital thread metadata to show it is deprecated.

• 1. Adding digital thread link across domains

The digital thread entity manages digital twins in a specific scope or domain, so it does not cover every digital twin across an enterprise or supply chain. For example, a supplier operates its own digital thread entity independently. This digital thread entity manages the digital twins relevant to its manufacturing process. Thus, digital twins from different domains (e.g., manufacturer and supplier) are managed by separate digital thread entities. To establish traceability in a different domain, a digital thread link across the domains can be created between digital twins.

Key

Figure B.5 — Adding a new digital thread link between digital twins of different domains

Figure B.5 is an operational scenario for adding a new digital thread link between digital twins managed by different digital thread entities operating in different domains.

The scenario is as follows.

Step 1. Reference made: a digital twin () of domain A (manufacturer) references or is created from digital twin () in domain X (supplier).

Step 2. Digital thread link created: new link is created between digital twin () and digital twin ().

Step 3. Updates to the digital thread in domain A: the digital twin () informs the digital thread entity of domain A that a new digital thread link has been created with digital twin () in domain X.

Step 4. Updates to the digital thread ledger in domain A: the digital thread entity in domain A updates the digital thread ledger to add a new digital thread link between the digital twin () and the digital twin (). A metadata of “{supplier}” is added to the digital thread link to indicate a manufacturer-supplier relationship.

Step 5. Updates to the digital thread in domain X: the digital twin () informs the digital thread entity of domain X that a new digital thread link has been created with digital twin () in domain A.

Step 6. Updates to digital thread ledger in domain X: the digital thread entity in domain X updates the digital thread ledger to add a new digital thread link between digital twin () and digital twin (). To domain X (supplier), domain A (manufacturer) is a customer; therefore, a digital thread metadata “{customer}” is added to the digital thread link.

• 1. Finding digital twin from different domain

Key

Figure B.6 — Finding a digital twin from a different domain

Figure B.6 shows a scenario where a digital twin in one domain (domain A) searches and locates a digital twin in a different domain (domain X), typically in a different organisation, such as suppliers, partners, or other departments. This scenario shows how the cross-domain discovery and linkage are managed using separate digital thread entities and digital thread ledgers in each domain.

The scenario is as follows.

Step 1. Query initiation: a digital twin () in domain A (manufacturer) sends a request to its local digital thread entity to search for a related digital twin ().

Step 2. Search: the digital thread entity searches the digital thread ledger to locate the requested digital twin. It finds out that the digital twin () is in another domain from the digital thread metadata.

Step 3. Query response: the digital thread entity responds with identifier(s) and other information for the digital twin () to communicate with digital twin () in domain X (supplier).

Step 4. Communicate with the digital twin: using the query response, the digital twin () communicates with digital twin ().

Bibliography

[1] IEC 62264 (all parts), — Enterprise-control system integration

[2] IEC 62443 (all parts), Security for industrial automation and control systems

[3] IEC 62541 (all parts), OPC Unified Architecture

[4] ISO 10303‑1, Industrial automation systems and integration — Product data representation and exchange — Part 1: Overview and fundamental principles

[5] ISO 10303‑209, Industrial automation systems and integration — Product data representation and exchange — Part 209: Application protocol: Multidisciplinary analysis and design

[6] ISO 10303‑210, Industrial automation systems and integration — Product data representation and exchange — Part 210: Application protocol: Electronic assembly, interconnect and packaging design

[7] ISO 10303‑233, Industrial automation systems and integration — Product data representation and exchange — Part 233: Application protocol: Systems engineering

[8] ISO 10303‑235, Industrial automation systems and integration — Product data representation and exchange — Part 235: Application protocol: Engineering properties and materials information

[9] ISO 10303‑238, Industrial automation systems and integration — Product data representation and exchange — Part 238: Application protocol: Model based integrated manufacturing

[10] ISO 10303‑239, Industrial automation systems and integration — Product data representation and exchange — Part 239: Application protocol: Product life cycle support

[11] ISO 10303‑242, Industrial automation systems and integration — Product data representation and exchange — Part 242: Application protocol: Managed model-based 3D engineering, 2022

[12] ISO 13374 (all parts), Condition monitoring and diagnostics of machine systems — Data processing, communication and presentation

[13] ISO 13399 (all parts), — Cutting tool data representation and exchange

[14] ISO 13584 (all parts), Industrial automation systems and integration — Parts library

[15] ISO 14306 (all parts), Industrial automation systems and integration — JT file format specification for 3D visualization

[16] ISO 22400 (all parts), Automation systems and integration — Key performance indicators (KPIs) for manufacturing operations management

[17] ISO 23247 (all parts), Automation systems and integration — Digital twin framework for manufacturing

[18] ISO 23952, Automation systems and integration — Quality information framework (QIF) — An integrated model for manufacturing quality information

[19] ISO 55000, Asset management — Vocabulary, overview and principles

[20] ISO/IEC 11179‑6, Information technology — Metadata registries (MDR) — Part 6: Registration

[21] ISO/IEC 20922, Information technology — Message Queuing Telemetry Transport (MQTT) v3.1.1

[22] ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

[23] ISO/IEC 17360, Automatic identification and data capture techniques — Supply chain applications of RFID — Product tagging, product packaging, transport units, returnable transport units and returnable packaging items

[24] ISO/IEC 30141, Internet of Things (IoT) — Reference architecture

[25] SAE International AIR 7161, “Guidance in Digital Thread data standards Enablement, Monitoring and Quantification with Digital thread Index”, Venkata and Rencher, 2024.

[26] Grieves, M. and J. Vickers, “Digital Twin: Mitigating Unpredictable, Undesirable Emergent Behavior in Complex Systems, in Trans-Disciplinary Perspectives on System Complexity”, 2016.

[27] IETF RFC 4122, A Universally Unique IDentifier (UUID) URN Namespace, 2005.

[28] https://www.digitaltwinconsortium.org/