Semantic Definition Format (SDF) modeling for Digital Twin
draft-ietf-asdf-digital-twin-02
| Document | Type | Active Internet-Draft (asdf WG) | |
|---|---|---|---|
| Authors | Hyunjeong Lee , Jungha Hong | ||
| Last updated | 2025-10-17 | ||
| Replaces | draft-lee-asdf-digital-twin | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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| Additional resources | Mailing list discussion | ||
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draft-ietf-asdf-digital-twin-02
ASDF H. Lee, Ed.
Internet-Draft J. Hong
Intended status: Informational ETRI
Expires: 20 April 2026 17 October 2025
Semantic Definition Format (SDF) modeling for Digital Twin
draft-ietf-asdf-digital-twin-02
Abstract
This memo specifies SDF modeling for a digital twin, i.e. a digital
twin system, and its Things. An SDF is a format that is used to
create and maintain data and interaction, and to represent the
various kinds of data that is exchanged for these interactions. The
SDF format can be used to model the characteristics, behavior and
interactions of Things, i.e. physical objects, in a digital twin that
contain Things as components.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 20 April 2026.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. SDF structure for digital twin . . . . . . . . . . . . . . . 3
4. Motivation and design rationale . . . . . . . . . . . . . . . 4
4.1. Introduction of sdfContext . . . . . . . . . . . . . . . 5
4.2. Digital Twin Modeling using elements of an SDF model . . 5
4.3. Relationship modeling . . . . . . . . . . . . . . . . . . 6
5. Examples of digital twin system . . . . . . . . . . . . . . . 8
5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 9
5.2. Marine system . . . . . . . . . . . . . . . . . . . . . . 9
5.3. Healthcare system . . . . . . . . . . . . . . . . . . . . 13
6. Requirements for implenmenting digital twin . . . . . . . . . 15
7. Procedure for digital twin implementation . . . . . . . . . . 15
7.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 15
7.2. Procedure . . . . . . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . 19
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 19
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
A digital twin is defined as a digital representation of an object of
interest and may require different capabilities, for example,
synchronization and real-time support, according to the specific
domain of application. [Y.4600]. Digital twin help organizations
improve important functional objectives, including real-time control,
off-line analytics, and predictive maintenance, by modeling and
simulating objects in the real world. Therefore, it is important for
a digital twin to represent as much real-world information about the
object as possible when digitally representing the object.
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Nowadays, digital twin technologies are applied in various domains
including manufacturing, energy, medical, farm, transportation, etc.
And a common format is needed to represent the objects in the domains
as digital twins. SDF [I-D.ietf-asdf-sdf] can be used for modeling
objects as digital twins.
This document specifies the modeling and guidance on how to use SDF
to represent objects as digital twins.
2. Terminology
This specification uses the terminology specified in
[I-D.ietf-asdf-sdf] in particular "Class Name Keyword", "Object", and
"Affordance".
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. SDF structure for digital twin
This section describes SDF structure with the new Class Name Keyword,
sdfContext, to represent a thing or an object as a digital twin. The
architecture of a digital twin based on the SDF model is illustrated
in Figure 1, , following the guidelines of [ISO23247-3].
The Physical Layer comprises affordance and non-affordance objects.
From the real-world objects, only those deemed relevant are selected
for representation as digital twins. The Digital Twin Layer is
structured into three sublayers: the Device Communication Sublayer,
the Digital Twin Sublayer, and the Application Sublayer. The Device
Communication Sublayer is responsible for monitoring and collecting
data from both affordance and non-affordance objects. This sublayer
provides the necessary data to synchronize the physical objects with
their digital twin counterparts. The Digital Twin Sublayer ensures
synchronization between the affordance and non-affordance objects and
their respective digital twins using the data provided by the Device
Communication Sublayer. The Application Sublayer presents the
synchronized values of the digital twins to users, facilitating
informed decision-making.
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+---------------------------------------------+ - - - - - - - - - - -
| Application Sublayer |
| +----------+ +------+ +--------+ +--------+ |
| | Human | | HMI | | Apps | | Peers | |
| +----------+ +------+ +--------+ +--------+ |
+---------------------------------------------+
| Digital Twin Sublayer |
| +----------+ +-------------+ +------------+ |
| | Operation| | Application | | Resource | |
| | and | | and | | access and | |
| |management| | service | |interchange | |
| +----------+ +-------------+ +------------+ |
| +-----------------------------------------+ | Digital twin Layer
| | Digital representation of objects | |
| | +-------------+ +----------------+ | |
| | | Affordance | | Non-affordance | | |
| | | objects | | objects | | |
| | +-------------+ +----------------+ | |
| +-----------------------------------------+ |
+---------------------------------------------+
| Device Communication Sublayer |
| +-------------+ +----------------+ |
| | Data | | Object | |
| | collection | | control | |
| +-------------+ +----------------+ |
+---------------------------------------------+ - - - - - - - - - - -
| +-------------+ +----------------+ |
| | Affordance | | sdfContext | |
| | objects | | objects | | Physical Layer
| +-------------+ +----------------+ |
+---------------------------------------------+ - - - - - - - - - - -
Figure 1: Basic Architecture of digital twin
4. Motivation and design rationale
The document is based on the underlying structure defined in
[I-D.ietf-asdf-sdf], which which standardizes the semantic definition
format (SDF) for representing IoT affordance. This specification
provides a strong basis for representing individual devices and their
features (sdfProperty, sdfAction, sdfEvent, etc.), but additional
mechanisms are needed to address the unique requirements of digital
twin modeling.
Digital twin systems defined in [ISO23247-3] often have to describe
virtual representations of various physical assets, including
metadata, identity, contextual relationships, historical data, as
well as device interfaces.
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4.1. Introduction of sdfContext
A new SDF keyword sdfContext described in
[I-D.draft-ietf-asdf-sdf-nonaffordance] is introduced to represent
non-functional or metadata elements that describe a device or
component without implying direct interaction:
* Identifier (e.g., UUID, URN)
* Location (e.g. site, zone, GPS tag)
* Owner (e.g., representative, ,anufacturer)
These field can appear in both sdfObject and sdfThing contexts and
follow the same structural pattern as sdfData and is designed for
scalability.
4.2. Digital Twin Modeling using elements of an SDF model
To support hierarchical representations (e.g., a boat composed of
heater, GPS, and battery subsystems), this document encourages use of
sdfThing to aggregate related sdfObject components, along with
metadata.
The example mapping of digital twin attributes to SDF elements is
shown in Table 1.
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+================+==============+==================================+
| Attribute | Recommended | Description |
| | Mapping | |
+================+==============+==================================+
| Identifier | sdfContext | Globally unique digital twin ID |
| | | (e.g., URN) |
+----------------+--------------+----------------------------------+
| Characteristic | sdfProperty | General description or domain |
| | or sdfData | properties |
+----------------+--------------+----------------------------------+
| Schedule | sdfEvent or | Time-based actions, |
| | sdfData | availability, or maintenance |
+----------------+--------------+----------------------------------+
| Status | sdfAction or | Actual or calculated operating |
| | sdfProperty | conditions |
+----------------+--------------+----------------------------------+
| Location | sdfContext | Physical or logical location |
| | | information |
+----------------+--------------+----------------------------------+
| Report | sdfData | Measurement summaries, |
| | | analytics, or logs |
+----------------+--------------+----------------------------------+
| owner | sdfContext | Organization or entity |
| | | responsible for the digital twin |
+----------------+--------------+----------------------------------+
| Relationship | sdfRelation | Inter-object/inter-twin |
| | | relationships |
+----------------+--------------+----------------------------------+
Table 1: Digital Twin Modeling using elements of an SDF model
4.3. Relationship modeling
The sdfRelation, defined in [I-D.draft-laari-asdf-relations], is a
structure for specifying logical or physical relationships between
objects within an SDF model. If conventional sdfThing, sdfObject,
and sdfProperty focus on defining the properties of individual
digital twins, sdfRelation is a means of expressing interactions and
structural links between them. Since these relationships go beyond a
single digital twin definition, they must be managed in a separate
structure, where sdfRelation is used. The sdfRelation keyword allows
describing complex relationships beyond just the parent-child
hierarchy. These relationships can include:
* Physical relations (e.g., "inside", "next to")
* Functional relations (e.g., "controls", "is controlled by")
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* Semantic relations (e.g., "similar to", "same as")
The sdfRelation definition can include the following fields as
defined in [I-D.draft-laari-asdf-relations]:
* relType: Specifies the type of relationship that can an external
ontologies (e.g., SAREF[saref4bldg]) can refer to.
* target: Points to the SDF object or an external ontology term that
is the target of the relationship.
* description: Provides a detailed textual explanation of the
relationship.
* label: A short human-readable label for the relationship.
* property: Additional properties describing the relationship
context.
* $comment: Optional properties including implementers notes.
An example of sdfRelation is shown in Figure 2. The sdfProtocolMap
in this example is defined in [I-D.draft-ietf-asdf-nipc] and
[I-D.draft-ietf-asdf-protocol-mapping]
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{
"sdfThing": {
"Room001": {
"description": "Contains lightbult and thermostat"
"sdfObject": {
"lightbulb": {
"description": "A smart lightbulb",
"sdfProperty": {
"adjacent-node": { "type": "object", "sdfType": "link"}
},
"sdfRelation": {
"sameRoomAsThermostat": {
"relType": "saref:isLocatedIn",
"target": "#/sdfObject/thermostat",
"description": "This lightbulb is located in the same room as the thermostat.",
"label": "Located together"
}
}
},
"thermostat": {
"description": "A thermostat is in the same room as the lightbulb",
"sdfProperty": {
"adjacent-node": {"type": "object","sdfType": "link"}
}
},
"sdfProtocolMap": {
"description": "Protocol between the lightbulb and thermostat",
"ble": {
"services":
[{"serviceID": "361c9c4f-22d7-4a1e-824b-8b61045a566a"}],
"cached": false,
"cacheIdlePurge": 3600,
"unit": "Second",
"autoUpdate": true,
"bonding": "default"
}
}
}
}
}
}
Figure 2: An example of sdfRelation
5. Examples of digital twin system
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5.1. Overview
Domain-specific examples are provided to illustrates how SDF-based
Digital Twin representations can be modeled across various
application areas. Each example is structured using the sdfThing
construct to represent the physical entity, with associated
sdfObject, sdfProperty, sdfAction, sdfEvent, and optional sdfContext
or sdfRelation entries. These examples cover multiple domains such
as maritime, smart building, healthcare, and energy systems, enabling
standardized modeling and interoperability across diverse use cases.
5.2. Marine system
Table 2 illustrates how various components of a maritime
vessel—specifically Boat007—can be represented as a structured
Digital Twin using the Semantic Definition Format (SDF) model. Each
physical component, such as a heater or battery, is abstracted as an
sdfObject, while the overall vessel is modeled as an sdfThing.
For each component, key SDF elements such as sdfProperty, sdfAction,
or sdfEvent are defined to describe the operational and contextual
aspects of the system. Relationships such as sdfRelation are used to
express functional connections (e.g., the battery is connectedTo the
controller), enabling richer modeling of interactions between
components.
This structure allows developers and systems integrators to:
* Seamlessly capture and communicate device capabilities and states.
* Integrate operational data for real-time monitoring and analysis.
* Enable interoperability with other domains through standardized
semantics.
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+=======================+=============+============================+
| Attribute | SDF element | Example properties |
+=======================+=============+============================+
| Boat007 | sdfThing | id, name, model, includes |
| | | heater1 and battery1 |
+-----------------------+-------------+----------------------------+
| Heater1 | sdfObject | status (sdfProperty), |
| | | temperature (sdfProperty), |
| | | turnOn (sdfAction) |
+-----------------------+-------------+----------------------------+
| Thermostat1 | sdfObject | setPoint, mode |
| | | (sdfProperty) |
+-----------------------+-------------+----------------------------+
| Battery1 | sdfObject | voltage (sdfProperty), |
| | | chargeLevel (sdfProperty), |
| | | battery-to-controller |
| | | (sdfRelation) |
+-----------------------+-------------+----------------------------+
| Controller | sdfObject | status (sdfProperty), |
| | | controlMode (sdfProperty) |
+-----------------------+-------------+----------------------------+
| Temp-to-Thermostat | sdfRelation | source: |
| | | heater1.temperature, |
| | | target: |
| | | thermostat1.setPoint, |
| | | relationType: regulatedBy |
+-----------------------+-------------+----------------------------+
| Battery-to-Controller | sdfRelation | source: batterySensor, |
| | | target: powerController, |
| | | relationType: connectedTo |
+-----------------------+-------------+----------------------------+
| Location | sdfContext | latitude, longitude, |
| | | dockedAt (e.g., port007) |
+-----------------------+-------------+----------------------------+
Table 2: Components and SDF elements of a marine system
In the context of Boat007, shown in Figure 3, such a Digital Twin can
support various applications, including predictive maintenance,
energy optimization, and fleet-level coordination, demonstrating the
practicality and scalability of SDF-based Digital Twin modeling for
mobility and transportation systems.
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{
"sdfThing": {
"boat007": {
"label": "Boat #007 with a heater",
"description": "Contains heaters, fans, battery, etc."
"sdfProperty": {
"status": {
"type": "boolean",
"description": "Indicates if the boat is powered"
}
},
"sdfObject": {
"heater1": {
"description": "A heater ",
"identityManifest": {
"manufacturer": "HeaterTech Inc.",
"model": "HEATER-2025-V1",
"firmwareVersion": "1.4.3",
"dateOfManufacture": "2025-04-20T09:00:00Z",
"certifications": [
{ "scheme": "KS", "certId": "KS123", "region": "KR" } ]
},
"contextSnapshot": {
"thingId": "heater:unit5689",
"timestamp": "2025-05-23T10:20:00Z",
"installationInfo": {
"room": "kitchen",
"floor": 1,
"mountType": "freestanding",
"installationDate": "2025-06-01"
},
"usageProfile": {
"type": "residential",
"powerCircuit": "230V@60Hz",
"energyRating": "A++"
},
"location": {"lat": 35.1796, "lon": 129.0756 }
},
"sdfProperty": {
"status": {
"type": "boolean"
"description":"Whether the heater is powered"
},
"temperature": {
"type": "number",
"unit": "degreeCelsius",
"description": "Temperature of the heater"
}
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},
"sdfAction": {
"turnOn": { "description": "Activate the heater" },
"turnOff": { "description": "Deactivate the heater" }
},
"contextPatch": {
"thingId": "heater:unit5689",
"timestamp": "2025-06-20T09:00:00Z",
"location": {"lat": "35.2988", "lon": "129.2547" },
"installationInfo": {"floor": 1, "mountType": "wall" }
}
},
"thermostat": {
"maintenanceSchedule": {
"timestamp": "2025-05-20T10:00:00Z"
"description": "Last maintained date"
}
},
"batterySensor1": {
"sdfProperty": {
"chargeLevel": {
"type": "number",
"unit": "percent",
"description": "Battery charge level"
},
"voltage": {
"type": "number",
"unit": "volt",
"description": "Battery voltage"
}
}
},
"powerController1": {
"sdfAction": {
"connect": {"description": "Connect power from the battery" },
"disconnect": {"description": "Disconn power from the battery"}
}
}
},
"sdfRelation": {
"temperature-control": {
"source": "#/sdfObject/heater1/sdfProperty/temperature",
"target": "#/sdfObject/thermostat1/sdfProperty/setPoint",
"relationType": "regulatedBy",
"directionality": "unidirectional",
"description": "The current temperature of the heater is regulated by the thermostat's setPoint value."
},
"battery-to-controller": {
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"source": "#/sdfObject/batterySensor",
"target": "#/sdfObject/powerController",
"relationType": "connectedTo",
"directionality": "unidirectional"
}
}
}
}
}
Figure 3: An example of marine system
5.3. Healthcare system
This example represents a digital twin for a patient health monitor
system (patientMonitor001) assigned to a patient. The system reports
real-time health properties while referencing contextual patient
information with the components and elements shown in Table 3.
+===========+==================+============================+
| Attribute | SDF element | Example properties |
+===========+==================+============================+
| Patient | sdfThing | patientMonitor001 as a |
| Monitor | | digital twin |
+-----------+------------------+----------------------------+
| ECG | sdfObject | heartRate, rhythmType, |
| Module | | signalStrength |
+-----------+------------------+----------------------------+
| Infusion | sdfObject | flowRate, volumeRemaining, |
| Pump | | alarmStatus |
+-----------+------------------+----------------------------+
| Property | sdfProperty | e.g., temperature, |
| | | bloodPressureSystolic, |
| | | oxygenSaturation |
+-----------+------------------+----------------------------+
| Context | sdfContext | bedNumber, wardLocation, |
| Info | | patientID, usageScenario |
+-----------+------------------+----------------------------+
| Identity | identityManifest | systemType, |
| Info | | firmwareVersion, |
| | | hospitalAssetTag |
+-----------+------------------+----------------------------+
| Relations | sdfRelation | ECG → AlarmSystem |
| | | (relationType: |
| | | monitoredBy) |
+-----------+------------------+----------------------------+
Table 3: Components and SDF elements of a healthcare system
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A digital twin example of a patient monitoring system with ECG and
infusion pump components is illustated in Figure 4. in the
healthcare domain, where a biosensor measuring the heart rate is
functionally connected to an alert system that emits a high heart
rate warning. This enables real-time patient monitoring in medical
environments.
{
"sdfThing": {
"patientMonitor001": {
"sdfObject": {
"ecg": {
"sdfProperty": {
"heartRate": { "type": "number", "unit": "bpm" },
"rhythmType": { "type": "string" }
}
},
"infusionPump": {
"sdfProperty": {
"flowRate": { "type": "number", "unit": "ml/h" },
"volumeRemaining": { "type": "number", "unit": "ml" }
}
}
},
"sdfContext": {
"wardLocation": { "const": "ICU-5A" },
"patientID": { "const": "PT123456" }
},
"identityManifest": {
"manufacturer": "MediTech",
"model": "IM-500",
"serialNumber": "MT-IM500-00789"
},
"sdfRelation": {
"heartRate-to-alertSystem": {
"description": "The heart rate data from the biosensor is monitored by the alert system, which triggers a warning event when a high heart rate is detected.",
"source": "#/sdfObject/biosensor/sdfProperty/heartRate",
"target": "#/sdfObject/alertSystem/sdfEvent/highHeartRateAlert",
"relationType": "monitoredBy",
"directionality": "unidirectional"
}
}
}
}
}
Figure 4: An example of healthcare
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6. Requirements for implenmenting digital twin
A digital twin is a partial representation of sdfThing or sdfObject
that contains attributes such as sdfProperty, sdfAction and
sdfEvent[ISO23247-1]. By representing sdfThing as a digital twin,
crucial events that require appropriate action can be quickly
detected and controlled. The requirements defined in [ISO23247-1]
are applied to represent sdfThings and sdfObjects as digital twins.
* Identification: sdfThings and sdfObjects should contain data that
uniquely identify them as digital twins.
* Data acquisition: data related to sdfThing and sdfObject, such as
sdfProperty, sdfEvent, and sdfAction, should be collected from IP
and non-IP systems.
* Data analysis: collected data needs to be analyzed to understand
the state of sdfThing and sdfObject.
* Accuracy: The sdfThings and sdfObjects should be represented as
digital twins with appropriate levels of detail and accuracy,
depending on the application.
* Synchronization: sdfThings and sdfObjects should be synchronized
with the digital twin at intervals appropriate to the requirements
of each application. Newly added or deleted sdfThings and
sdfObjects should be recognized and reflected in the digital twin.
7. Procedure for digital twin implementation
7.1. Overview
It is essential to define a standardized implementation procedure to
ensure interoperability, scalability, and effective lifecycle
management across digital twin systems. This section outlines a
step-by-step approach aligned with the Semantic Definition Format
(SDF) model and its architecture, enabling consistent modeling,
integration, and operation of digital twins in IoT environments. A
general principles for representing an sdfThing as a digital twin
within a specific domain is outlined as follows:
* defining a purpose for expressing the observable object as a
digital twin in the domain
* collecting and mapping data based on the roles of the observable
object in the domain
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* configuring the observable object into the digital twin based on
the data for the purposes
* interworking among digital twins reflecting various roles of the
observable object
* synchronizing the observable object and the digital twin
7.2. Procedure
The procedure of digitally twinning the space and the objects
contained in it is described.
* Identifying and scoping physical assets: The first step is to
clearly identify the physical assets that will be represented as
digital twins. This step includes assigning a globally unique
identifier, such as a URN or UUID, and determining the extent of
modeling. It also involves deciding whether the unique identifier
will cover the entire system or focus on a specific subsystem or
component. Although all assets in space can be represented by
digital twins, it is cost-effective to select assets for
implementation purposes and configure them as digital twins.
* Defining a digital twin: A detailed digital twin should be defined
using SDF structures, including sdfThing and sdfObject. This step
requires specifying affordances such as sdfProperty, sdfAction,
and sdfEvent, as well as non-affordance metadata like location,
owner, and other descriptive elements through sdfContext.
* Metadata and contextualization: This step adds metadata that
enriches the context of the digital twin, such as geographic
location, ownership details, manufacturing information, and
feature summaries. It can also support advanced analytics and
management, including contextual attributes such as production
schedules or maintenance periods.
* Binding interfaces and communications: Digital twins are bound to
real-world communication interfaces and protocols such as MQTT,
CoAP, and HTTP. This allows affordance of SDF models to interact
with real-world data sources, APIs, and physical assets in a
smooth and reliable manner.
* Verification and compliance: Once an asset is defined and bound as
a digital twin, it should be validated against syntax and semantic
rules using tools such as JSON schema validators or CDDL
definitions. Compliance with specific SDF profiles or domain-
specific standards must also be verified to ensure
interoperability.
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* Deployment and registration: After verification, the digital twins
are deployed in a digital twin registry, edge system, or cloud
infrastructure. This step involves registering the model with the
discovery service for integration and use by other systems or
stakeholders.
* Runtime monitoring and updating: During operations, digital twins
need to continuously monitor real data and update their status
accordingly. Properties updates, event processing, and partial
updates using contextPatch messages should be supported for
efficient and lightweight synchronization.
* Lifecycle and governance management: The life cycle of the digital
twin is managed through version tracking, audit logs, and
compliance documents. This step ensures safe and transparent
governance and enables proper disposal and deregistration when
assets are no longer available.
8. Security Considerations
Only authorized users should have the authority to manage digital
twins, sdfThings and sdfObjects. Also, Secure communication and
metadata integrity are essential when implementing digital twins.
All context messages, including contextPatch and identityManifest,
must have mechanisms such as authentication and authorization
applied.
9. IANA Considerations
This document has no IANA actions.
10. References
10.1. Normative References
[I-D.draft-ietf-asdf-nipc]
Brinckman, B., Mohan, R., and B. Sanford, "An Application
Layer Interface for Non-IP device control (NIPC)", Work in
Progress, Internet-Draft, I-D.draft-ietf-asdf-nipc-13, 20
September 2025, <https://datatracker.ietf.org/doc/html/I-
D.draft-ietf-asdf-nipc-13>.
[I-D.draft-ietf-asdf-protocol-mapping]
Mohan, R., Brinckman, B., and L. Corneo, "Protocol Mapping
for SDF", Work in Progress, Internet-Draft, I-D.draft-
ietf-asdf-protocol-mapping-01, 16 October 2025,
<https://datatracker.ietf.org/doc/html/I-D.draft-ietf-
asdf-protocol-mapping-01>.
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[I-D.draft-ietf-asdf-sdf-nonaffordance]
Hong, J. and H. Lee, "Semantic Definition Format (SDF)
Extension for Non-Affordance Information", Work in
Progress, Internet-Draft, I-D.draft-ietf-asdf-sdf-
nonaffordance-01, 21 September 2025,
<https://datatracker.ietf.org/doc/html/I-D.draft-ietf-
asdf-sdf-nonaffordance-01>.
[I-D.draft-laari-asdf-relations]
Laari, P., "Extended relation information for Semantic
Definition Format (SDF)", Work in Progress, Internet-
Draft, I-D.draft-laari-asdf-relations-04, 28 January 2025,
<https://datatracker.ietf.org/doc/html/I-D.draft-laari-
asdf-relations-04>.
[I-D.ietf-asdf-sdf]
Koster, M., Bormann, C., and A. Keränen, "Semantic
Definition Format (SDF) for Data and Interactions of
Things", Work in Progress, Internet-Draft, draft-ietf-
asdf-sdf-25, 13 October 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-asdf-
sdf-25>.
[ISO23247-1]
"Automation systems and integration Digital twin framework
for manufacturing - Part 1: Overview and general
principles, ISO 23247-1.", October 2021,
<https://www.iso.org/standard/75066.html>.
[ISO23247-3]
"Automation systems and integration Digital twin framework
for manufacturing - Part 3: Digital representation of
manufacturing elements, ISO 23247-3.", October 2021,
<https://www.iso.org/standard/78744.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[Y.4600] Union, I. T., ""Recommendation ITU-T Y.4600 (2022),
Requirements and capabilities of a digital twin system for
smart cities.", August 2022.
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10.2. Informative References
[saref4bldg]
Poveda-Villaln, M. and R. Garcia-Castro, "SAREF extension
for building", 5 June 2020,
<https://saref.etsi.org/saref4bldg>.
Acknowledgements
This specification is based on work by the One Data Model group.
Contributors
Joo-Sang Youn
DONG-EUI University
176 Eomgwangno Busan_jin_gu
Busan
47340
South Korea
Phone: +82 51 890 1993
Email: joosang.youn@gmail.com
Yong-Geun Hong
Daejeon University
62 Daehak-ro, Dong-gu
Daejeon
34520
South Korea
Phone: +82 42 280 4841
Email: yonggeun.hong@gmail.com
Authors' Addresses
Hyunjeong Lee (editor)
Electronics and Telecommunications Research Institute
218 Gajeong-ro, Yuseong-gu
Daejeon
34129
South Korea
Phone: +82 42 860 1213
Email: hjlee294@etri.re.kr
Jungha Hong
Electronics and Telecommunications Research Institute
218 Gajeong-ro, Yuseong-gu
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Daejeon
34129
South Korea
Phone: +82 42 860 0926
Email: jhong@etri.re.kr
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