Additional Units for Sensor Measurement Lists (SenML)
RFC 8798

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Internet Engineering Task Force (IETF)                        C. Bormann
Request for Comments: 8798                        Universität Bremen TZI
Category: Standards Track                                      June 2020
ISSN: 2070-1721

         Additional Units for Sensor Measurement Lists (SenML)

Abstract

   The Sensor Measurement Lists (SenML) media type supports the
   indication of units for a quantity represented.  This short document
   registers a number of additional unit names in the IANA registry for
   units in SenML.  It also defines a registry for secondary units that
   cannot be in SenML's main registry, as they are derived by linear
   transformation from units already in that registry.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8798.

Copyright Notice

   Copyright (c) 2020 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  New Primary Units
     2.1.  Rationale
   3.  New Registry for Secondary Units
   4.  Operational Considerations
   5.  Security Considerations
   6.  IANA Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgements
   Author's Address

1.  Introduction

   The Sensor Measurement Lists (SenML) [RFC8428] media type supports
   the indication of a unit, using the SenML field "u", for the quantity
   given as a data value in a SenML record.  For this purpose, SenML
   defines an IANA registry of defined unit names and their meanings; in
   the present document, we call the unit names registered there
   "primary unit names".

   This short document registers a number of additional units in the
   IANA registry for units in SenML that appear to be necessary for
   further adopting SenML in other Standards Development Organizations
   (SDOs).

   The document also defines a registry for secondary unit names that
   cannot be in SenML's main registry, as they are derived by linear
   transformation from units already in that registry.  Although SenML
   version 10 [RFC8428] does not provide for the direct use of these
   secondary units, future support is intended via the use of SenML
   extension mechanisms, one of which is proposed in [SENML-VERSIONS].

   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.

2.  New Primary Units

   IANA has assigned new units in the "SenML Units" subregistry of the
   "Sensor Measurement Lists (SenML)" registry [IANA.SENML] (as defined
   in [RFC8428]):

   +========+======================================+=======+===========+
   | Symbol | Description                          | Type  | Reference |
   +========+======================================+=======+===========+
   | B      | Byte (information content)           | float | RFC 8798  |
   +--------+--------------------------------------+-------+-----------+
   | VA     | volt-ampere (Apparent Power)         | float | RFC 8798  |
   +--------+--------------------------------------+-------+-----------+
   | VAs    | volt-ampere second (Apparent         | float | RFC 8798  |
   |        | Energy)                              |       |           |
   +--------+--------------------------------------+-------+-----------+
   | var    | volt-ampere reactive (Reactive       | float | RFC 8798  |
   |        | Power)                               |       |           |
   +--------+--------------------------------------+-------+-----------+
   | vars   | volt-ampere-reactive second          | float | RFC 8798  |
   |        | (Reactive Energy)                    |       |           |
   +--------+--------------------------------------+-------+-----------+