Semantic Definition Format (SDF): Mapping files

1.1. Terminology and Conventions

The definitions of [I-D.ietf-asdf-sdf] apply.¶

The term "byte" is used in its now-customary sense as a synonym for "octet".¶

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 [BCP14] (RFC2119) (RFC8174) when, and only when, they appear in all capitals, as shown here.¶

2.1. Example Model 1 (ecosystem: IPSO/OMA)

An example for an SDF mapping file is given in Figure 1. This mapping file is meant to attach to an SDF specification published by OneDM, and to add qualities relevant to the IPSO/OMA ecosystem.
Note that this example uses namespaces to identify elements of the referenced specification(s), but has un-namespaced quality names. These two kinds of namespaces are unrelated in SDF, and a more robust example may need to make use of Quality Name Prefixes as defined in Section 2.3.3-3 of [I-D.ietf-asdf-sdf] (independent of a potential feature to add namespace references to definitions that are not intended to go into the default namespace — these are SDF definition namespaces and not quality namespaces, which are one meta-level higher).¶

• Start of a mapping file for certain OneDM playground models:¶

{
  "info": {
    "title": "IPSO ID mapping"
  },
  "namespace": {
    "onedm": "https://onedm.org/models"
  },
  "defaultNamespace": "onedm",
  "map": {
    "#/sdfObject/Digital_Input": {
      "id": 3200
    },
    "#/sdfObject/Digital_Input/sdfProperty/Digital_Input_State": {
      "id": 5500
    },
    "#/sdfObject/Digital_Input/sdfProperty/Digital_Input_Counter": {
      "id": 5501
    }
  }
}

2.2. Example Model 2 (ecosystem: W3C WoT)

This example shows a translation of a hypothetical W3C WoT Thing Model into an SDF model plus a mapping file to catch Thing Model attributes that don't currently have SDF qualities defined.
The example probably would be more useful with, say, protocol bindings. This is left for a future version of this example, and/or a future specification that specifically addresses how to map Thing Models into SDF.
(There is also the separate requirement to transform a Thing Description into the kind of information that can be represented in SDF plus instance information, such as IP addresses or specific node names.)
Finally, namespaces are all wrong in this example.¶

• The input: WoT Thing Model¶

{
    "@context": ["http://www.w3.org/ns/td"],
    "@type" : "tm:ThingModel",
    "title": "Lamp Thing Model",
    "titles": {
      "en": "Lamp Thing Model",
      "de": "Thing Model für eine Lampe"
    },
    "properties": {
        "status": {
            "description": "Current status of the lamp",
            "descriptions": {
              "en": "Current status of the lamp",
              "de": "Aktueller Status der Lampe"
            },
            "type": "string",
            "readOnly": true
        }
    }
}

• The output: SDF model¶

{
  "info": {
    "title": "Lamp Thing Model"
  },
  "namespaces": {
    "wot": "http://www.w3.org/ns/td"
  },
  "defaultNamespace": "wot",
  "sdfObject": {
    "LampThingModel": {
      "label": "Lamp Thing Model",
      "sdfProperty": {
        "status": {
          "description": "Current status of the lamp",
          "writable": false,
          "type": "string"
        }
      }
    }
  }
}

• The other output: SDF mapping file¶

{
  "info": {
    "title": "Lamp Thing Model: WoT TM mapping"
  },
  "namespace": {
    "wot": "http://www.w3.org/ns/td"
  },
  "defaultNamespace": "wot",
  "map": {
    "#/sdfObject/LampThingModel": {
      "titles": {
        "en": "Lamp Thing Model",
        "de": "Thing Model für eine Lampe"
      }
    },
    "#/sdfObject/LampThingModel/sdfProperty/status": {
      "descriptions": {
        "en": "Current status of the lamp",
        "de": "Aktueller Status der Lampe"
      }
    }
  }
}

4.1. Media Type

IANA is requested to add the following Media-Type to the "Media Types" registry.¶

RFC Editor: please replace RFC XXXX with this RFC number and remove this note.¶

Type name:

application¶

Subtype name:

sdf-mapping+json¶

Required parameters:

none¶

Optional parameters:

none¶

Encoding considerations:

binary (JSON is UTF-8-encoded text)¶

Security considerations:

Section 5 of RFC XXXX¶

Interoperability considerations:

none¶

Published specification:

Section 4.1 of RFC XXXX¶

Applications that use this media type:

Tools for data and interaction modeling that describes Things, i.e., physical objects that are available for interaction over a network¶

Fragment identifier considerations:

A JSON Pointer fragment identifier may be used, as defined in Section 6 of [RFC6901].¶

Person & email address to contact for further information:

ASDF WG mailing list (asdf@ietf.org), or IETF Applications and Real-Time Area (art@ietf.org)¶

Intended usage:

COMMON¶

Restrictions on usage:

none¶

Author/Change controller:

IETF¶

Provisional registration:

no¶

4.2. Registries

(TBD: After any future additions, check if we need any.)¶

6.1. Normative References

[BCP14]

Best Current Practice 14, <https://www.rfc-editor.org/info/bcp14>.
At the time of writing, this BCP comprises the following:

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/info/rfc2119>.

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/info/rfc8174>.

[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, 28 February 2024, <https://datatracker.ietf.org/doc/html/draft-ietf-asdf-sdf-18>.

[RFC6901]

Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed., "JavaScript Object Notation (JSON) Pointer", RFC 6901, DOI 10.17487/RFC6901, April 2013, <https://www.rfc-editor.org/rfc/rfc6901>.

[RFC7396]

Hoffman, P. and J. Snell, "JSON Merge Patch", RFC 7396, DOI 10.17487/RFC7396, October 2014, <https://www.rfc-editor.org/rfc/rfc7396>.

[RFC8610]

Birkholz, H., Vigano, C., and C. Bormann, "Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.

6.2. Informative References

[RFC8576]

Garcia-Morchon, O., Kumar, S., and M. Sethi, "Internet of Things (IoT) Security: State of the Art and Challenges", RFC 8576, DOI 10.17487/RFC8576, April 2019, <https://www.rfc-editor.org/rfc/rfc8576>.