ASDF Working Group H. Lee Internet-Draft ETRI Intended status: Standards Track J-S. Youn Expires: 3 January 2025 Dong-eui Univ Y-G. Hong Daejeon University 2 July 2024 Extended information of Semantic Definition Format (SDF) for Digital Twin draft-lee-asdf-digital-twin-02 Abstract An SDF specification can describe the definition of Things, i.e., physical objects and their associated interactions, and express the various information that is exchanged for these interactions. Therefore, the SDF format can be used to define the behavior of an object and its associated data model and interaction model in a digital twin system that includes the object as a component. In a digital twin system, interactions between physical and virtual objects, as well as interactions of objects existing in different digital twin systems, are performed over a network, making it important to provide location information of objects during interactions. This document specifies the extension of SDF to represent the location information of objects. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 3 January 2025. Lee, et al. Expires 3 January 2025 [Page 1] Internet-Draft SDF for Digital Twin July 2024 Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. 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 extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Location Extension of SDF for Digital Twin . . . . . . . . . 4 3.1. SDF Location Extension in an SDF Model . . . . . . . . . 4 3.2. Namespaces . . . . . . . . . . . . . . . . . . . . . . . 5 3.3. Qualities of sdfLocation . . . . . . . . . . . . . . . . 5 3.3.1. locationType . . . . . . . . . . . . . . . . . . . . 6 3.3.2. target . . . . . . . . . . . . . . . . . . . . . . . 6 3.3.3. description . . . . . . . . . . . . . . . . . . . . . 6 3.3.4. label . . . . . . . . . . . . . . . . . . . . . . . . 6 3.4. Location description with sdfType links . . . . . . . . . 7 3.5. Location description with geographical information . . . 7 3.6. Location description with relative information . . . . . 8 4. Security Considerations . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Normative References . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction A digital twin is a digital representation of an object of interest and may require different capabilities (e.g., synchronization, real- time support) according to the specific domain of application. [Y.4600]. Digital twin systems 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 system to represent as much real-world information about the object as possible when digitally representing the object. A procedure for representing an observable Thing, as known as a Lee, et al. Expires 3 January 2025 [Page 2] Internet-Draft SDF for Digital Twin July 2024 physical asset or an object of interest, as a digital twin in a domain is as follows: * defining a purpose for expressing the observable object as a digital twin in the domain * organizing data based on the roles of the observable object in the domain * configuring the observable object into the digital twin based on the data for the purposes * interworking with a digital twin of each of other domains in which the observable object performs a different role * synchronizing the observable object and the digital twin Nowadays, digital twin systems are applied in various domains including medical, manufacturing, farm, transportation, etc. And a common format is needed to represent the objects in the domains as digital twins. An SDF specification [I-D.ietf-asdf-sdf] can be used for the purpose of digital representation of objects in a digital twin system. However, because the SDF specification only provides a basic model for digital representation, it cannot represent objects location information. The location information of the object is the important information to digitally representation of the object. This document extends the basic SDF specification by adding a new keyword "location" to represent an object as a digital twin. This new keyword is needed to adequately represent the current location of the object, which is helpful for users to manage the domain efficiently. 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. Lee, et al. Expires 3 January 2025 [Page 3] Internet-Draft SDF for Digital Twin July 2024 3. Location Extension of SDF for Digital Twin This section defines a new SDF Class Name Keyword, sdfLocation, that can be used to represent the location of a thing or an object as a digital twin. The location definitions are at the class level and describe the use of sdfLocation. [I-D.ietf-laari-asdf-sdf-relations]. 3.1. SDF Location Extension in an SDF Model The SDF language uses seven predefined Class Name Keywords, including sdfLocation, for modeling connected Things, as illustrated in Figure 1. The sdfLocation is a new Class Name Keyword and is used to describe physical or logical location of sdfThing or sdfObject. The sdfLocation is described using conventional GPS coordinates or postal addresses for physical locations, which enable extensive reuse and interoperability. The sdfLocation is also described by strings or integers for relative locations. For example, in a boat model, a specific sdfObjects, such as a heater, can be described as being on a "boat" using GPS coordinates or in a "specific location on the boat" using relative locations. ,--------. |sdfThing| |--------| `--------' ,---------. |sdfObject| |---------| `---------' ,-----------. ,---------. ,--------. ,-----------. |sdfProperty| |sdfAction| |sdfEvent| |sdfLocation| |-----------| |---------| |--------| |-----------| `-----------' `---------' `--------' `-----------' | ,-------. |sdfData| |-------| `-------' Figure 1: SDF Location Extension of an SDF Model Lee, et al. Expires 3 January 2025 [Page 4] Internet-Draft SDF for Digital Twin July 2024 3.2. Namespaces The SDF namespace block can be used to provide CURIE prefixes for external ontologies for use with sdfLocation extension. For example, in case of SAREF (Smart Applications REFerence ontology) ontology extension for buildings [saref4bldg], we can use the following namespace definition:. { "namespace": { "saref": "https://saref.etsi.org/saref4bldg/v1.1.2/" } } 3.3. Qualities of sdfLocation This section defines the qualities of the sdfLocation. These qualities are used to define the potential type of the sdfLocation. A named definition entry in an sdfProperty may be associated with some protocol affordance to enable the application to obtain the location of sdfThing or sdfObject. +==============+========+==========+========================+ | Quality | Type | Required | Description | +==============+========+==========+========================+ | locationType | string | yes | What kind of location | | | | | these definitions have | +--------------+--------+----------+------------------------+ | target | string | no | Target model for the | | | | | location | +--------------+--------+----------+------------------------+ | description | string | no | Description of the | | | | | location | +--------------+--------+----------+------------------------+ | label | string | no | Short text describing | | | | | the location | +--------------+--------+----------+------------------------+ | property | object | no | Additional properties | | | | | for this location | +--------------+--------+----------+------------------------+ | $comment | string | no | Additional comments | | | | | for implementors | +--------------+--------+----------+------------------------+ Table 1: Qualities of sdfLocation Lee, et al. Expires 3 January 2025 [Page 5] Internet-Draft SDF for Digital Twin July 2024 3.3.1. locationType The locationType quality describes the type of location including geographical or relative information [ISO23247-3]. This can use different descriptions, such as GPS, postal address, relative location. The purpose of the locationType is to represent the current location of an sdfThing or an sdfObject. For example, the locationType can be defined as "218 Gajeong-ro, 7th building in ETRI, WorkUnit #3 in ETRI branch #2" and so on. 3.3.2. target The "target" field defines to which definition or ontology term this definition with sdfLocation has a location to. For example, this can be #/sdfObject/location, when the target location of an object is defined in the same SDF model. "namespace": { "exont": "https://example.com/relationOntology", "saref": "https://saref.etsi.org/core/v3.1.1/" }, sdfObject: { "Humidity": { "description": "Example Humidity object", "sdfProperty": { ... }, "sdfLocation": { "postalAddr": { "locationType": "exont:postal-addr", "target": "saref:PostalAddress", "description": "address of object", "label":"postcode" } } } ... } 3.3.3. description The "description" field defines the location. For SDF version 1.1, the description is a string. 3.3.4. label Short text describing the location, similar to label quality in other SDF definitions. Lee, et al. Expires 3 January 2025 [Page 6] Internet-Draft SDF for Digital Twin July 2024 3.4. Location description with sdfType links This extension allows you to describe location from the SDF model to various (SDF or other) definitions. For link data types for affordance, for example, for link properties that can be accessed and modified during runtime, the "sdfType for links" extension [I-D.bormann-asdf-sdftype-link] can be used instead. In the following example, we have a definition for location with the postal address format: sdfObject: { "example-object": { "description": "example object", "sdfProperty": { ... }, "sdfLocation": { "postalAddr": { "locationType": "exont:postal-addr", "target": "saref:PostalAddress", "description": "Postal address of a company", "218 Gajeong-ro ...", "label":"34129", "property":"company address" } } } ... 3.5. Location description with geographical information This description allows you to describe location of sdfThing or sdfObject with geographical information. Lee, et al. Expires 3 January 2025 [Page 7] Internet-Draft SDF for Digital Twin July 2024 sdfObject: { "sdfLocation": { "sdfData": { "geoLocation" : { "latitude": "string", "longitude": "string" "altitude": "string" } ... "Boat_#1": { "latitude": "35.5188233791372", "longitude": "129.37308376484913", "altitude": "0.0" } } } } 3.6. Location description with relative information This description allows you to describe location of sdfThing or sdfObject with relative information including geographical information. Lee, et al. Expires 3 January 2025 [Page 8] Internet-Draft SDF for Digital Twin July 2024 sdfObject: { "sdfLocation": { "sdfData": { "geoLocation" : { "latitude": "string", "longitude": "string" "altitude": "string" } "relativeLocation" : { "relative-x": "integer", "relative-y": "integer" "relative-z": "integer" "unit":"cm" } ... "Boat_#1": { "latitude": "35.5188233791372", "longitude": "129.37308376484913", "altitude": "0.0" } "Heater_A_in_the_Boat_#1": { "latitude": "35.5188233791372", "longitude": "129.37308376484913", "altitude": "0.0" "relative-x": "7215", "relative-y": "1324" "relative-z": "217" } } } } 4. Security Considerations TODO Security 5. IANA Considerations This document has no IANA actions. 6. References 6.1. Normative References Lee, et al. Expires 3 January 2025 [Page 9] Internet-Draft SDF for Digital Twin July 2024 [I-D.bormann-asdf-sdftype-link] Bormann, C., "An sdfType for Links", Work in Progress, Internet-Draft, I-D.bormann-asdf-sdftype-link, 3 December 2023, . [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-18, 29 February 2024, . [I-D.ietf-laari-asdf-sdf-relations] Laari, P., "Extended relation information for Semantic Definition Format (SDF)", Work in Progress, Internet- Draft, I-D.ietf-laari-asdf-sdf-relations, 13 September 2023, . [ISO23247-3] "Automation systems and integration Digital twin framework for manufacturing - Part 3: Digital representation of manufacturing elements, ISO 23247-3.", October 2021, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [Y.4600] Union, I. T., ""Recommendation ITU-T Y.4600 (2022), Requirements and capabilities of a digital twin system for smart cities.", August 2022. 6.2. Informative References [saref4bldg] Poveda-Villaln, M. and R. Garcia-Castro, "SAREF extension for building", 5 June 2020, . Lee, et al. Expires 3 January 2025 [Page 10] Internet-Draft SDF for Digital Twin July 2024 Authors' Addresses Hyunjeong Lee Electronics and Telecommunications Research Institute 218 Gajeong-ro, Yuseong-gu Daejeon 34129 South Korea Phone: +82 42 860 1213 Email: hjlee294@etri.re.kr 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 Lee, et al. Expires 3 January 2025 [Page 11]