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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'IEC-80000-13' -- Possible downref: Non-RFC (?) normative reference: ref. 'IEC-80000-6' -- Possible downref: Non-RFC (?) normative reference: ref. 'IEEE-1459' Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group C. Bormann 3 Internet-Draft Universitaet Bremen TZI 4 Intended status: Standards Track July 25, 2019 5 Expires: January 26, 2020 7 Additional Units for SenML 8 draft-bormann-senml-more-units-02 10 Abstract 12 The Sensor Measurement Lists (SenML) media type supports the 13 indication of units for a quantity represented. This short document 14 registers a number of additional unit names in the IANA registry for 15 Units in SenML. It also defines a registry for secondary units that 16 cannot be in SenML's main registry as they are derived by linear 17 transformation from units already in that registry. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at https://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on January 26, 2020. 36 Copyright Notice 38 Copyright (c) 2019 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (https://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. New Units . . . . . . . . . . . . . . . . . . . . . . . . . . 2 55 3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 4. New Registry . . . . . . . . . . . . . . . . . . . . . . . . 4 57 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 58 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 59 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6 60 8. Normative References . . . . . . . . . . . . . . . . . . . . 6 61 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 63 1. Introduction 65 The Sensor Measurement Lists (SenML, [RFC8428]) media type supports 66 the indication of a unit, using the SenML field "u", for the quantity 67 given as a data value in a SenML record. For this purpose, SenML 68 defines an IANA registry of defined Unit names and their meanings. 70 This short document registers a number of additional units in the 71 IANA registry for Units in SenML that appear to be necessary for 72 further adopting SenML in other Standards Development Organizations 73 (SDOs). 75 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 76 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 77 "OPTIONAL" in this document are to be interpreted as described in 78 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 79 capitals, as shown here. 81 2. New Units 83 IANA is requested to assign new units in the "SenML Units" 84 subregistry of the SenML registry [IANA.senml] (as defined in 85 [RFC8428]): 87 +--------+--------------------------------------+-------+-----------+ 88 | Symbol | Description | Type | Reference | 89 +--------+--------------------------------------+-------+-----------+ 90 | B | Byte (information content) | float | RFCthis | 91 | | | | | 92 | VA | volt-ampere (Apparent Power) | float | RFCthis | 93 | | | | | 94 | var | volt-ampere reactive (Reactive | float | RFCthis | 95 | | Power) | | | 96 | | | | | 97 | vars | volt-ampere reactive seconds | float | RFCthis | 98 | | (Reactive Energy) | | | 99 | | | | | 100 | J/m | joule per meter (Energy per | float | RFCthis | 101 | | distance) | | | 102 | | | | | 103 | deg | degrees (angle)* | float | RFCthis | 104 +--------+--------------------------------------+-------+-----------+ 106 Table 1: New units registered for SenML 108 3. Rationale 110 SenML [RFC8428] takes the position that unscaled SI units should 111 always be used. However, SenML makes one exception: The degree 112 Celsius (as Cel) is allowed as an alternative to the K (Kelvin). 114 This document takes the position that the same should apply to a 115 small number of alternative units in wide use: 117 o The Byte. [IEC-80000-13] defines both the bit (item 13-9.b) and 118 the byte (item 13-9.c, also called octet) as alternative names for 119 the coherent unit one for the purpose of giving storage capacity 120 and related quantities. While the name octet is associated with 121 the symbol o, this is in wide use only in French-speaking 122 countries. Globally more wide-spread is the symbol B for byte, 123 even though B is already taken in SI for bel. [RFC8428] therefore 124 registers dB as the SenML unit for logarithmic relative power, 125 leaving B free for the usage proposed here. While this is 126 potentially confusing, the situation is widely understood in 127 engineering circles and is unlikely to cause actual problems. 129 o The Volt-Ampere. [IEC-80000-6]} item 6-57.a defines the VA (volt 130 ampere) as a unit for apparent power; items 6-59.a, 6-60.a and 131 6-61.a also use the unit for complex, reactive, and non-active 132 power. 134 o The Volt-Ampere-reactive. [IEC-80000-6] item 6-60.b defines the 135 var (volt ampere reactive) as an alternative (and fully 136 equivalent) unit to VA specifically for reactive power (with the 137 primary unit VA). It is not presently known to this author how 138 the upcoming revision of IEC 80000-6 will update this, but it has 139 became clear since that there is strong interest in using this 140 unit specifically for the imaginary content of complex power, 141 reactive power [IEEE-1459]. 143 The unit "degrees" is unit in wide use in practice for plane angle 144 (as in heading, bearing, etc.). It is marked with an asterisk 145 because the preferred coherent SI unit is radian ("rad"). 147 The Joule per meter is not a traditional electromagnetic unit. It 148 and its scaled derivatives (in particular Wh/km) are used to describe 149 the energy expended for achieving motion over a given distance, e.g. 150 as an equivalent for electrical cars of the inverse of "mileage". 152 4. New Registry 154 IANA is requested to create a "secondary units" subregistry in the 155 SenML registry [IANA.senml] defined in [RFC8428]. 157 The registry has four columns: 159 o secondary unit: a newly registered name allocated within the same 160 namespace as SenML units 162 o SenML unit: an existing SenML unit from the SenML units registry 164 o scale, offset: two rational numbers, expressed in decimal or as a 165 fraction divided by a "/" character. 167 Quantities expressed in the secondary unit can be converted into the 168 SenML unit by first multiplying their value with the scale number and 169 then adding the offset, yielding the value in the given SenML unit. 171 The initial content of the secondary units registry is: 173 +----------------+------------+---------+--------+-----------+ 174 | secondary unit | SenML unit | scale | offset | Reference | 175 +----------------+------------+---------+--------+-----------+ 176 | ms | s | 1/1000 | 0 | RFCthis | 177 | | | | | | 178 | min | s | 60 | 0 | RFCthis | 179 | | | | | | 180 | h | s | 3600 | 0 | RFCthis | 181 | | | | | | 182 | kW | W | 1000 | 0 | RFCthis | 183 | | | | | | 184 | kVA | VA | 1000 | 0 | RFCthis | 185 | | | | | | 186 | kvar | var | 1000 | 0 | RFCthis | 187 | | | | | | 188 | Ah | C | 3600 | 0 | RFCthis | 189 | | | | | | 190 | Wh | J | 3600 | 0 | RFCthis | 191 | | | | | | 192 | kWh | J | 3600000 | 0 | RFCthis | 193 | | | | | | 194 | kvar | var | 1000 | 0 | RFCthis | 195 | | | | | | 196 | varh | vars | 3600 | 0 | RFCthis | 197 | | | | | | 198 | Wh/km | J/m | 3.6 | 0 | RFCthis | 199 | | | | | | 200 | KiB | B | 1024 | 0 | RFCthis | 201 | | | | | | 202 | mV | V | 1/1000 | 0 | RFCthis | 203 | | | | | | 204 | dBm | dBW | 1 | -30 | RFCthis | 205 +----------------+------------+---------+--------+-----------+ 207 Example: the value of a quantity given as 100 ms is first multiplied 208 by 1/1000, yielding the number 0.1, and then the offset 0 is added, 209 yielding the number 0.1 again, leading to a quantity of 0.1 s. The 210 value of a quantity given as 10 dBm is first multiplied by 1, 211 yielding the number 10, and then the offset -30 is added, yielding 212 the number -20, leading to a quantity of -20 dBW. 214 New entries can be added to the registration by Expert Review as 215 defined in [RFC8126]. Experts should exercise their own good 216 judgment, with the same guidelines as used for SenML units 217 (Section 12.1 of [RFC8428]), but without applying the rules 4 and 5. 219 SenML packs MAY, but SHOULD NOT use scaled units in place of SenML 220 units, where the exception lies in the context of specific data 221 models that are based on these scaled units. 223 [So does this spec update RFC 8428?] 225 5. Security Considerations 227 The security considerations of [RFC8428] apply. The introduction of 228 new measurement units poses no additional security considerations 229 except from a possible potential for additional confusion about the 230 proper unit to use. 232 6. IANA Considerations 234 See Section 2 and Section 4. 236 Acknowledgements 238 Ari Keranen pointed out the need for additional units in SenML. 240 8. Normative References 242 [IANA.senml] 243 IANA, "Sensor Measurement Lists (SenML)", 244 . 246 [IEC-80000-13] 247 "Quantities and units - Part 13: Information science and 248 technology", IEC 80000-13, Edition 1.0, March 2008. 250 [IEC-80000-6] 251 "Quantities and units - Part 6: Electromagnetism", 252 IEC 80000-6, Edition 1.0, March 2008. 254 [IEEE-1459] 255 "IEEE Standard Definitions for the Measurement of Electric 256 Power Quantities Under Sinusoidal, Nonsinusoidal, 257 Balanced, or Unbalanced Conditions", IEEE Std 1459-2010, 258 March 2010. 260 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 261 Requirement Levels", BCP 14, RFC 2119, 262 DOI 10.17487/RFC2119, March 1997, 263 . 265 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 266 Writing an IANA Considerations Section in RFCs", BCP 26, 267 RFC 8126, DOI 10.17487/RFC8126, June 2017, 268 . 270 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 271 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 272 May 2017, . 274 [RFC8428] Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C. 275 Bormann, "Sensor Measurement Lists (SenML)", RFC 8428, 276 DOI 10.17487/RFC8428, August 2018, 277 . 279 Author's Address 281 Carsten Bormann 282 Universitaet Bremen TZI 283 Postfach 330440 284 Bremen D-28359 285 Germany 287 Phone: +49-421-218-63921 288 Email: cabo@tzi.org