Extended information of Semantic Definition Format (SDF) for Digital Twin
draft-lee-asdf-digital-twin-01

ASDF Working Group                                                H. Lee
Internet-Draft                                                      ETRI
Intended status: Standards Track                               J-S. Youn
Expires: 5 September 2024                                  Dong-eui Univ
                                                               Y-G. Hong
                                                      Daejeon University
                                                            4 March 2024

  Extended information of Semantic Definition Format (SDF) for Digital
                                  Twin
                     draft-lee-asdf-digital-twin-01

Abstract

   An SDF specification can describe the definition of a Things, i.e.,
   physical objects and their associated interactions and express the
   various information that be exchanged for the interactions.
   Therefore, the SDF format can be used to define the behaviour of an
   object and its associated data model and interaction model in a
   digital twin system that has an object as a component.  In a digital
   twin system, interactions between physical and virtual objects, as
   well as interactions of objects existing in the different digital
   twin systems, are performed over a network, which is important to
   provide location information of objects during interactions.  This
   document specifies the extension information of SDF to represent the
   location information of an objects.

Status of This Memo

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   This Internet-Draft will expire on 5 September 2024.

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Copyright Notice

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SDF Location Extension for Digital Twin . . . . . . . . . . .   4
     3.1.  Namespaces  . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Qualities of sdfLocation  . . . . . . . . . . . . . . . .   4
       3.2.1.  locationType  . . . . . . . . . . . . . . . . . . . .   5
       3.2.2.  target  . . . . . . . . . . . . . . . . . . . . . . .   5
       3.2.3.  description . . . . . . . . . . . . . . . . . . . . .   6
       3.2.4.  label . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Example location description with sdfType links . . . . .   6
     3.4.  Example location description with geographical
           information . . . . . . . . . . . . . . . . . . . . . . .   7
     3.5.  Example location description with relative information  .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   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,
   predictive maintenance by modelling and simulating of 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 physical asset or an object of

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   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.

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3.  SDF Location Extension 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
   digital twin.  The location definitions are on class-level, and
   describes the use of sdfLocation [I-D.ietf-laari-asdf-sdf-relations].

3.1.  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/"
       }
   }

3.2.  Qualities of sdfLocation

   This section defines the qualities of the sdfLocation.  These
   qualities are used to define the potential type of the sdfLocation.

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       +==============+========+==========+========================+
       | 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

3.2.1.  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.

3.2.2.  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.

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     "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"
           }
         }
       }
     ...
     }

3.2.3.  description

   The "description" field defines the location.  For SDF version 1.1,
   the description is a string.

3.2.4.  label

   Short text describing the location, similar to label quality in other
   SDF definitions.

3.3.  Example 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:

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     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"
           }
         }
       }
     ...

3.4.  Example location description with geographical information

   This example allows you to describe location of sdfThing or sdfObject
   with geographical information.

     sdfObject: {
       "sdfLocation": {
         "sdfData": {
           "geoLocation" : {
               "latitude": "string",
               "longitude": "string"
               "altitude": "string"
           }
             ...
           "Boat_#1": {
               "latitude": "35.5188233791372",
               "longitude": "129.37308376484913",
               "altitude": "0.0"
           }
         }
       }
     }

3.5.  Example location description with relative information

   This example allows you to describe location of sdfThing or sdfObject
   with relative information including geographical information.

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     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

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   [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, <https://datatracker.ietf.org/doc/html/I-D.bormann-
              asdf-sdftype-link>.

   [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,
              <https://datatracker.ietf.org/doc/html/draft-ietf-asdf-
              sdf-18>.

   [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, <https://datatracker.ietf.org/doc/html/I-D.ietf-
              laari-asdf-sdf-relations>.

   [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.

6.2.  Informative References

   [saref4bldg]
              Poveda-Villaln, M. and R. Garcia-Castro, "SAREF extension
              for building", 5 June 2020,
              <https://saref.etsi.org/saref4bldg>.

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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

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