Internet-Draft sdfType for Links December 2023
Bormann Expires 5 June 2024 [Page]
Intended Status:
Standards Track
C. Bormann
Universität Bremen TZI

An sdfType for Links


This document defines and registers an sdfType "link" for the Semantic Definition Format (SDF) for Data and Interactions of Things (draft-ietf-asdf-sdf).

About This Document

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This Internet-Draft will expire on 5 June 2024.

1. Introduction

The Semantic Definition Format for Data and Interactions of Things (SDF, [I-D.ietf-asdf-sdf]) is a format for domain experts to use in the creation and maintenance of data and interaction models in the Internet of Things.

A common data type that occurs in the modeling of IoT devices is the link. [RFC8288] defines the concept of Web Linking, which complements the target URI that any link will contain, with additional parameters, such as the "link relation type" that explains the relationship expressed by the link, as well as "target attributes" that provide additional information about the target of the link (without a need to "dereference", i.e., follow, the link).

This document defines and registers an sdfType "link" for the Semantic Definition Format. This type models an abstract "serialization" [RFC8288] of a link, in a way that is compatible with the way SDF maps information models to its data modeling language.

3. Discussion

Links play an important role in SDF modeling both during definition time (for adding information to a model, such as in sdfRef) and during run time (for making links to instances into a subject of data and interaction modeling). The present document is an early attempt at addressing the run-time usage of links, in particular links that fit the Web Linking [RFC8288] abstractions. A related draft [I-D.laari-asdf-relations] addresses definition-time links, but does seem to touch modeling run-time use of links as well (e.g., by discussing "writable" link relations).

Not all links used in ecosystems are based on URIs. E.g., OMA has "object links", which are pairs of numbers (object/instance). These ecosystem links may have some structure that should be modeled in the SDF model (e.g., where the object id part of a link always has to have a specific value). This structure can be mapped into URI strings using some convention, e.g., an OMA object link could be oma-object:3303:0 (where oma-object is placeholder for a URI scheme to be defined). However, burying structural components of the ecosystem-specific link in a string syntax makes it hard to access and control those components from the model.

TODO: Examples are needed to show how the OCF collection pattern is addressed by the current specification.

4. Security Considerations

The security considerations of [RFC8288] apply in a general way, although modeling a link as a datatype does not incur all of the security considerations that will apply to actually interchanging these links.


5. IANA Considerations

// RFC Ed.: please replace RFC XXXX with this RFC number and remove this note.

IANA is requested to register the sdfType "link" in the "sdfType Values" sub-registry in the "SDF Parameters" registry, with the following completion for the registration template:

Table 1: Registration for sdfType "link"
Name Description type JSON Representation Reference
link A Web Link [RFC8288] object object members for link attributes RFCXXXX

6. References

6.1. Normative References

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-17, , <>.
Nottingham, M., "Web Linking", RFC 8288, DOI 10.17487/RFC8288, , <>.

6.2. Informative References

Bormann, C., "CoRE Target Attributes Registry", Work in Progress, Internet-Draft, draft-ietf-core-target-attr-06, , <>.
Laari, P., "Extended relation information for Semantic Definition Format (SDF)", Work in Progress, Internet-Draft, draft-laari-asdf-relations-02, , <>.
Shelby, Z., "Constrained RESTful Environments (CoRE) Link Format", RFC 6690, DOI 10.17487/RFC6690, , <>.


Discussions in the OneDM liaison organization shaped this proposal.

Author's Address

Carsten Bormann
Universität Bremen TZI
Postfach 330440
D-28359 Bremen