Internet DRAFT - draft-bormann-asdf-sdftype-link
draft-bormann-asdf-sdftype-link
ASDF WG C. Bormann
Internet-Draft Universität Bremen TZI
Intended status: Standards Track 3 December 2023
Expires: 5 June 2024
An sdfType for Links
draft-bormann-asdf-sdftype-link-02
Abstract
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
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-bormann-asdf-sdftype-link/.
Discussion of this document takes place on the A Semantic Definition
Format for Data and Interactions of Things Working Group mailing list
(mailto:asdf@ietf.org), which is archived at
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https://www.ietf.org/mailman/listinfo/asdf/.
Source for this draft and an issue tracker can be found at
https://github.com/cabo/sdftype-link.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on 5 June 2024.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3
2. The sdfType "link" . . . . . . . . . . . . . . . . . . . . . 3
3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
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.
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1.1. Conventions and Definitions
The definitions of [RFC6690], [RFC8288], and [I-D.ietf-asdf-sdf]
apply.
2. The sdfType "link"
The sdfType "link" is intended to be used with the SDF "type" of
"object". The members of that object are strings that are named the
same as the link parameter (attribute) names. The special parameter
name "href" is used to express the link target. (Parameter names
specific to the Constrained RESTful Environment (CoRE) are also
discussed in [I-D.ietf-core-target-attr].)
An example for the instance of a link is provided in Section 5 of
[RFC6690]:
</sensors/temp>;rt="temperature-c";if="sensor",
An sdfProperty that is used to describe an SDF affordance that is
intended to hold a link like this (without getting specific on the
actual link to the link target) could look like:
{
"sdfProperty": {
"temp-c-link": {
"type": "object",
"sdfType": "link",
"properties": {
"href": { "type": "string"},
"rt": { "type": "string", "const": "temperature-c"},
"if": { "type": "string", "const": "sensor"}
}
}
}
}
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).
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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.
(TODO)
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:
+======+=============+========+=====================+===========+
| Name | Description | type | JSON Representation | Reference |
+======+=============+========+=====================+===========+
| link | A Web Link | object | object members for | RFCXXXX |
| | [RFC8288] | | link attributes | |
+------+-------------+--------+---------------------+-----------+
Table 1: Registration for sdfType "link"
6. References
6.1. Normative References
[I-D.ietf-asdf-sdf]
Koster, M., Bormann, C., and A. Keränen, "Semantic
Definition Format (SDF) for Data and Interactions of
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Things", Work in Progress, Internet-Draft, draft-ietf-
asdf-sdf-17, 5 November 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-asdf-
sdf-17>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/rfc/rfc8288>.
6.2. Informative References
[I-D.ietf-core-target-attr]
Bormann, C., "CoRE Target Attributes Registry", Work in
Progress, Internet-Draft, draft-ietf-core-target-attr-06,
11 October 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-core-target-attr-06>.
[I-D.laari-asdf-relations]
Laari, P., "Extended relation information for Semantic
Definition Format (SDF)", Work in Progress, Internet-
Draft, draft-laari-asdf-relations-02, 13 September 2023,
<https://datatracker.ietf.org/doc/html/draft-laari-asdf-
relations-02>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/rfc/rfc6690>.
Acknowledgments
Discussions in the OneDM liaison organization shaped this proposal.
Author's Address
Carsten Bormann
Universität Bremen TZI
Postfach 330440
D-28359 Bremen
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
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