Network Working Group C. Bormann
Internet-Draft Universitaet Bremen TZI
Intended status: Standards Track February 27, 2019
Expires: August 31, 2019
Additional Units for SenML
draft-bormann-senml-more-units-00
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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. New Units . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 4
7. Normative References . . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
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.
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).
2. New Units
IANA is requested to assign new units in the "SenML Units"
subregistry of the SenML registry [IANA.senml] (as defined in
[RFC8428]):
+--------+--------------------------------------+-------+-----------+
| Symbol | Description | Type | Reference |
+--------+--------------------------------------+-------+-----------+
| B | Byte (information content) | float | RFCthis |
| | | | |
| VA | volt-ampere (Apparent Power) | float | RFCthis |
| | | | |
| var | volt-ampere reactive (Reactive | float | RFCthis |
| | Power) | | |
| | | | |
| J/m | joule per meter (Energy per | float | RFCthis |
| | distance) | | |
+--------+--------------------------------------+-------+-----------+
Table 1: New units registered for SenML
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3. Rationale
SenML [RFC8428] takes the position that unscaled SI units should
always be used. However, SenML makes one exception: The degree
Celsius (as Cel) is allowed as an alternative to the K (Kelvin).
This document takes the position that the same should apply to a
small number of alternative units in wide use:
o The Byte. [IEC-80000-13] defines both the bit (item 13-9.b) and
the byte (item 13-9.c, also called octet) as alternative names for
the coherent unit one for the purpose of giving storage capacity
and related quantities. While the name octet is associated with
the symbol o, this is in wide use only in French-speaking
countries. Globally more wide-spread is the symbol B for byte,
even though B is already taken in SI for bel. [RFC8428] therefore
registers dB as the SenML unit for logarithmic relative power,
leaving B free for the usage proposed here. While this is
potentially confusing, the situation is widely understood in
engineering circles and is unlikely to cause actual problems.
o The Volt-Ampere. [IEC-80000-6]} item 6-57.a defines the VA (volt
ampere) as a unit for apparent power; items 6-59.a, 6-60.a and
6-61.a also use the unit for complex, reactive, and non-active
power.
o The Volt-Ampere-reactive. [IEC-80000-6] item 6-60.b defines the
var (volt ampere reactive) as an alternative (and fully
equivalent) unit to VA specifically for reactive power (with the
primary unit VA). It is not presently known to this author how
the upcoming revision of IEC 80000-6 will update this, but it has
became clear since that there is strong interest in using this
unit specifically for the imaginary content of complex power,
reactive power [IEEE-1459].
The Joule per meter is not a traditional electromagnetic unit. It
and its scaled derivatives (in particular Wh/km) are used to describe
the energy expended for achieving motion over a given distance, e.g.
as an equivalent for electrical cars of the inverse of "mileage".
4. Security Considerations
The security considerations of [RFC8428] apply. The introduction of
new measurement units poses no additional security considerations
except from a possible potential for additional confusion about the
proper unit to use.
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5. IANA Considerations
See Section 2.
Acknowledgements
Ari Keranen pointed out the need for additional units in SenML.
7. Normative References
[IANA.senml]
IANA, "Sensor Measurement Lists (SenML)",
<http://www.iana.org/assignments/senml>.
[IEC-80000-13]
"Quantities and units - Part 13: Information science and
technology", IEC 80000-13, Edition 1.0, March 2008.
[IEC-80000-6]
"Quantities and units - Part 6: Electromagnetism",
IEC 80000-6, Edition 1.0, March 2008.
[IEEE-1459]
"IEEE Standard Definitions for the Measurement of Electric
Power Quantities Under Sinusoidal, Nonsinusoidal,
Balanced, or Unbalanced Conditions", IEEE Std 1459-2010,
March 2010.
[RFC8428] Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
Bormann, "Sensor Measurement Lists (SenML)", RFC 8428,
DOI 10.17487/RFC8428, August 2018,
<https://www.rfc-editor.org/info/rfc8428>.
Author's Address
Carsten Bormann
Universitaet Bremen TZI
Postfach 330440
Bremen D-28359
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
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