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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 August 29, 2019 5 Expires: March 1, 2020 7 Additional Units for SenML 8 draft-bormann-senml-more-units-04 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 March 1, 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. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 61 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 62 8.2. Informative References . . . . . . . . . . . . . . . . . 7 63 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 65 1. Introduction 67 The Sensor Measurement Lists (SenML, [RFC8428]) media type supports 68 the indication of a unit, using the SenML field "u", for the quantity 69 given as a data value in a SenML record. For this purpose, SenML 70 defines an IANA registry of defined Unit names and their meanings. 72 This short document registers a number of additional units in the 73 IANA registry for Units in SenML that appear to be necessary for 74 further adopting SenML in other Standards Development Organizations 75 (SDOs). 77 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 78 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 79 "OPTIONAL" in this document are to be interpreted as described in 80 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 81 capitals, as shown here. 83 2. New Units 85 IANA is requested to assign new units in the "SenML Units" 86 subregistry of the SenML registry [IANA.senml] (as defined in 87 [RFC8428]): 89 +--------+--------------------------------------+-------+-----------+ 90 | Symbol | Description | Type | Reference | 91 +--------+--------------------------------------+-------+-----------+ 92 | B | Byte (information content) | float | RFCthis | 93 | | | | | 94 | VA | volt-ampere (Apparent Power) | float | RFCthis | 95 | | | | | 96 | var | volt-ampere reactive (Reactive | float | RFCthis | 97 | | Power) | | | 98 | | | | | 99 | vars | volt-ampere reactive seconds | float | RFCthis | 100 | | (Reactive Energy) | | | 101 | | | | | 102 | J/m | joule per meter (Energy per | float | RFCthis | 103 | | distance) | | | 104 | | | | | 105 | kg/m3 | kilograms per cubic meter (mass | float | RFCthis | 106 | | concentration) | | | 107 | | | | | 108 | deg | degrees (angle)* | float | RFCthis | 109 +--------+--------------------------------------+-------+-----------+ 111 Table 1: New units registered for SenML 113 3. Rationale 115 SenML [RFC8428] takes the position that unscaled SI units should 116 always be used. However, SenML makes one exception: The degree 117 Celsius (as Cel) is allowed as an alternative to the K (Kelvin). 119 This document takes the position that the same should apply to a 120 small number of alternative units in wide use: 122 o The Byte. [IEC-80000-13] defines both the bit (item 13-9.b) and 123 the byte (item 13-9.c, also called octet) as alternative names for 124 the coherent unit one for the purpose of giving storage capacity 125 and related quantities. While the name octet is associated with 126 the symbol o, this is in wide use only in French-speaking 127 countries. Globally more wide-spread is the symbol B for byte, 128 even though B is already taken in SI for bel. [RFC8428] therefore 129 registers dB as the SenML unit for logarithmic relative power, 130 leaving B free for the usage proposed here. While this is 131 potentially confusing, the situation is widely understood in 132 engineering circles and is unlikely to cause actual problems. 134 o The Volt-Ampere. [IEC-80000-6]} item 6-57.a defines the VA (volt 135 ampere) as a unit for apparent power; items 6-59.a, 6-60.a and 136 6-61.a also use the unit for complex, reactive, and non-active 137 power. 139 o The Volt-Ampere-reactive. [IEC-80000-6] item 6-60.b defines the 140 var (volt ampere reactive) as an alternative (and fully 141 equivalent) unit to VA specifically for reactive power (with the 142 primary unit VA). It is not presently known to this author how 143 the upcoming revision of IEC 80000-6 will update this, but it has 144 became clear since that there is strong interest in using this 145 unit specifically for the imaginary content of complex power, 146 reactive power [IEEE-1459]. 148 The unit "degrees" is unit in wide use in practice for plane angle 149 (as in heading, bearing, etc.). It is marked with an asterisk 150 because the preferred coherent SI unit is radian ("rad"). 152 The Joule per meter is not a traditional electromagnetic unit. It 153 and its scaled derivatives (in particular Wh/km) are used to describe 154 the energy expended for achieving motion over a given distance, e.g., 155 as an equivalent for electrical cars of the inverse of "mileage". 157 4. New Registry 159 IANA is requested to create a "secondary units" subregistry in the 160 SenML registry [IANA.senml] defined in [RFC8428]. 162 The registry has four columns: 164 o secondary unit: a newly registered name allocated within the same 165 namespace as SenML units 167 o SenML unit: an existing SenML unit from the SenML units registry 169 o scale, offset: two rational numbers, expressed in decimal 170 (optionally, with a decimal exponent given) or as a fraction 171 divided by a "/" character. 173 Quantities expressed in the secondary unit can be converted into the 174 SenML unit by first multiplying their value with the scale number and 175 then adding the offset, yielding the value in the given SenML unit. 177 The initial content of the secondary units registry is: 179 +----------------+------------+-----------+--------+-----------+ 180 | secondary unit | SenML unit | scale | offset | Reference | 181 +----------------+------------+-----------+--------+-----------+ 182 | ms | s | 1/1000 | 0 | RFCthis | 183 | | | | | | 184 | min | s | 60 | 0 | RFCthis | 185 | | | | | | 186 | h | s | 3600 | 0 | RFCthis | 187 | | | | | | 188 | kW | W | 1000 | 0 | RFCthis | 189 | | | | | | 190 | kVA | VA | 1000 | 0 | RFCthis | 191 | | | | | | 192 | kvar | var | 1000 | 0 | RFCthis | 193 | | | | | | 194 | Ah | C | 3600 | 0 | RFCthis | 195 | | | | | | 196 | Wh | J | 3600 | 0 | RFCthis | 197 | | | | | | 198 | kWh | J | 3600000 | 0 | RFCthis | 199 | | | | | | 200 | kvar | var | 1000 | 0 | RFCthis | 201 | | | | | | 202 | varh | vars | 3600 | 0 | RFCthis | 203 | | | | | | 204 | Wh/km | J/m | 3.6 | 0 | RFCthis | 205 | | | | | | 206 | KiB | B | 1024 | 0 | RFCthis | 207 | | | | | | 208 | mV | V | 1/1000 | 0 | RFCthis | 209 | | | | | | 210 | mA | A | 1/1000 | 0 | RFCthis | 211 | | | | | | 212 | dBm | dBW | 1 | -30 | RFCthis | 213 | | | | | | 214 | ug/m3 | kg/m3 | 1e-9 | 0 | RFCthis | 215 | | | | | | 216 | mm/h | m/s | 1/3600000 | 0 | RFCthis | 217 | | | | | | 218 | ppm | / | 1e-6 | 0 | RFCthis | 219 | | | | | | 220 | hPa | Pa | 100 | 0 | RFCthis | 221 | | | | | | 222 | mm | m | 1/1000 | 0 | RFCthis | 223 +----------------+------------+-----------+--------+-----------+ 225 Example: the value of a quantity given as 100 ms is first multiplied 226 by 1/1000, yielding the number 0.1, and then the offset 0 is added, 227 yielding the number 0.1 again, leading to a quantity of 0.1 s. The 228 value of a quantity given as 10 dBm is first multiplied by 1, 229 yielding the number 10, and then the offset -30 is added, yielding 230 the number -20, leading to a quantity of -20 dBW. 232 New entries can be added to the registration by Expert Review as 233 defined in [RFC8126]. Experts should exercise their own good 234 judgment, with the same guidelines as used for SenML units 235 (Section 12.1 of [RFC8428]), but without applying the rules 4 and 5. 236 Guidelines to the difference between units (which can go into the 237 registry) and quantities are widely available, see for instance [RS]. 239 SenML packs MAY, but SHOULD NOT use secondary units in place of SenML 240 units, where the exception of the "SHOULD NOT" lies in the context of 241 specific existing data models that are based on these secondary 242 units. 244 [So does this spec update RFC 8428?] 246 5. Security Considerations 248 The security considerations of [RFC8428] apply. The introduction of 249 new measurement units poses no additional security considerations 250 except from a possible potential for additional confusion about the 251 proper unit to use. 253 6. IANA Considerations 255 See Section 2 and Section 4. 257 Acknowledgements 259 Ari Keranen pointed out the need for additional units in SenML. 261 8. References 263 8.1. Normative References 265 [IANA.senml] 266 IANA, "Sensor Measurement Lists (SenML)", 267 . 269 [IEC-80000-13] 270 "Quantities and units - Part 13: Information science and 271 technology", IEC 80000-13, Edition 1.0, March 2008. 273 [IEC-80000-6] 274 "Quantities and units - Part 6: Electromagnetism", 275 IEC 80000-6, Edition 1.0, March 2008. 277 [IEEE-1459] 278 "IEEE Standard Definitions for the Measurement of Electric 279 Power Quantities Under Sinusoidal, Nonsinusoidal, 280 Balanced, or Unbalanced Conditions", IEEE Std 1459-2010, 281 March 2010. 283 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 284 Requirement Levels", BCP 14, RFC 2119, 285 DOI 10.17487/RFC2119, March 1997, 286 . 288 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 289 Writing an IANA Considerations Section in RFCs", BCP 26, 290 RFC 8126, DOI 10.17487/RFC8126, June 2017, 291 . 293 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 294 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 295 May 2017, . 297 [RFC8428] Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C. 298 Bormann, "Sensor Measurement Lists (SenML)", RFC 8428, 299 DOI 10.17487/RFC8428, August 2018, 300 . 302 8.2. Informative References 304 [RS] Rohde&Schwarz, "Standard-compliant usage of quantities, 305 units and equations", version 4.0, November 2016, 306 . 310 Author's Address 312 Carsten Bormann 313 Universitaet Bremen TZI 314 Postfach 330440 315 Bremen D-28359 316 Germany 318 Phone: +49-421-218-63921 319 Email: cabo@tzi.org