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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group C. Jennings 3 Internet-Draft Cisco 4 Intended status: Standards Track Z. Shelby 5 Expires: September 21, 2016 ARM 6 J. Arkko 7 A. Keranen 8 Ericsson 9 March 20, 2016 11 Media Types for Sensor Markup Language (SenML) 12 draft-jennings-core-senml-05 14 Abstract 16 This specification defines media types for representing simple sensor 17 measurements and device parameters in the Sensor Markup Language 18 (SenML). Representations are defined in JavaScript Object Notation 19 (JSON), Concise Binary Object Representation (CBOR), eXtensible 20 Markup Language (XML), and Efficient XML Interchange (EXI), which 21 share the common SenML data model. A simple sensor, such as a 22 temperature sensor, could use this media type in protocols such as 23 HTTP or CoAP to transport the measurements of the sensor or to be 24 configured. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on September 21, 2016. 43 Copyright Notice 45 Copyright (c) 2016 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 2. Requirements and Design Goals . . . . . . . . . . . . . . . . 3 62 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 63 4. Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . 5 64 5. Associating Meta-data . . . . . . . . . . . . . . . . . . . . 7 65 6. JSON Representation (application/senml+json) . . . . . . . . 8 66 6.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . 9 67 6.1.1. Single Datapoint . . . . . . . . . . . . . . . . . . 9 68 6.1.2. Multiple Datapoints . . . . . . . . . . . . . . . . . 9 69 6.1.3. Multiple Measurements . . . . . . . . . . . . . . . . 10 70 6.1.4. Collection of Resources . . . . . . . . . . . . . . . 11 71 7. CBOR Representation (application/senml+cbor) . . . . . . . . 12 72 8. XML Representation (application/senml+xml) . . . . . . . . . 13 73 9. EXI Representation (application/senml-exi) . . . . . . . . . 15 74 10. Usage Considerations . . . . . . . . . . . . . . . . . . . . 18 75 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 76 11.1. Units Registry . . . . . . . . . . . . . . . . . . . . . 19 77 11.2. Media Type Registration . . . . . . . . . . . . . . . . 21 78 11.2.1. senml+json Media Type Registration . . . . . . . . . 22 79 11.2.2. senml+cbor Media Type Registration . . . . . . . . . 23 80 11.2.3. senml+xml Media Type Registration . . . . . . . . . 24 81 11.2.4. senml-exi Media Type Registration . . . . . . . . . 24 82 11.3. XML Namespace Registration . . . . . . . . . . . . . . . 25 83 11.4. CoAP Content-Format Registration . . . . . . . . . . . . 26 84 12. Security Considerations . . . . . . . . . . . . . . . . . . . 26 85 13. Privacy Considerations . . . . . . . . . . . . . . . . . . . 26 86 14. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 26 87 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 88 15.1. Normative References . . . . . . . . . . . . . . . . . . 27 89 15.2. Informative References . . . . . . . . . . . . . . . . . 28 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 92 1. Overview 94 Connecting sensors to the internet is not new, and there have been 95 many protocols designed to facilitate it. This specification defines 96 new media types for carrying simple sensor information in a protocol 97 such as HTTP or CoAP called the Sensor Markup Language (SenML). This 98 format was designed so that processors with very limited capabilities 99 could easily encode a sensor measurement into the media type, while 100 at the same time a server parsing the data could relatively 101 efficiently collect a large number of sensor measurements. The 102 markup language can be used for a variety of data flow models, most 103 notably data feeds pushed from a sensor to a collector, and the web 104 resource model where the sensor is requested as a resource 105 representation (e.g., "GET /sensor/temperature"). 107 There are many types of more complex measurements and measurements 108 that this media type would not be suitable for. SenML strikes a 109 balance between having some information about the sensor carried with 110 the sensor data so that the data is self describing but it also tries 111 to make that a fairly minimal set of auxiliary information for 112 efficiency reason. Other information about the sensor can be 113 discovered by other methods such as using the CoRE Link Format 114 [RFC6690]. 116 SenML is defined by a data model for measurements and simple meta- 117 data about measurements and devices. The data is structured as a 118 single array that contains a series of SenML Records which can each 119 contain attributes such as an unique identifier for the sensor, the 120 time the measurement was made, the unit the measurement is in, and 121 the current value of the sensor. Serializations for this data model 122 are defined for JSON [RFC7159], CBOR [RFC7049], XML, and Efficient 123 XML Interchange (EXI) [W3C.REC-exi-20110310]. 125 For example, the following shows a measurement from a temperature 126 gauge encoded in the JSON syntax. 128 [{ "n": "urn:dev:ow:10e2073a01080063", "v":23.1, "u":"Cel" }] 130 In the example above, the array has a single SenML record with a 131 measurement for a sensor named "urn:dev:ow:10e2073a01080063" with a 132 current value of 23.5 degrees Celsius. 134 2. Requirements and Design Goals 136 The design goal is to be able to send simple sensor measurements in 137 small packets on mesh networks from large numbers of constrained 138 devices. Keeping the total size of payload under 80 bytes makes this 139 easy to use on a wireless mesh network. It is always difficult to 140 define what small code is, but there is a desire to be able to 141 implement this in roughly 1 KB of flash on a 8 bit microprocessor. 142 Experience with Google power meter and large scale deployments has 143 indicated that the solution needs to support allowing multiple 144 measurements to be batched into a single HTTP or CoAP request. This 145 "batch" upload capability allows the server side to efficiently 146 support a large number of devices. It also conveniently supports 147 batch transfers from proxies and storage devices, even in situations 148 where the sensor itself sends just a single data item at a time. The 149 multiple measurements could be from multiple related sensors or from 150 the same sensor but at different times. 152 The basic design is an array with a series of measurements. The 153 following example shows two measurements made at different times. 154 The value of a measurement is in the "v" tag, the time of a 155 measurement is in the "t" tag, the "n" tag has a unique sensor name, 156 and the unit of the measurement is carried in the "u" tag. 158 [ 159 { "n": "urn:dev:ow:10e2073a01080063", 160 "t": 1276020076, "v":23.5, "u":"Cel" }, 161 { "n": "urn:dev:ow:10e2073a01080063", 162 "t": 1276020091, "v":23.6, "u":"Cel" } 163 ] 165 To keep the messages small, it does not make sense to repeat the "n" 166 tag in each SenML Record so there is a concept of a Base Name which 167 is simply a string that is prepended to the Name field of all 168 elements in that record and any records that follow it. So a more 169 compact form of the example above is the following. 171 [ 172 { "bn": "urn:dev:ow:10e2073a01080063", 173 "t": 1276020076, "v":23.5, "u":"Cel" }, 174 { "t": 1276020091, "v":23.6, "u":"Cel" } 175 ] 177 In the above example the Base Name is in the "bn" tag and the "n" 178 tags in each Record are the empty string so they are omitted. The 179 Base Name also could be put in a separate Record such as in the 180 following example. 182 [ 183 { "bn": "urn:dev:ow:10e2073a01080063" }, 184 { "t": 1276020076, "v":23.5, "u":"Cel" }, 185 { "t": 1276020091, "v":23.6, "u":"Cel" } 186 ] 187 Some devices have accurate time while others do not so SenML supports 188 absolute and relative times. Time is represented in floating point 189 as seconds and values greater than zero represent an absolute time 190 relative to the unix epoch while values of 0 or less represent a 191 relative time in the past from the current time. A simple sensor 192 with no absolute wall clock time might take a measurement every 193 second and batch up 60 of them then send it to a server. It would 194 include the relative time the measurement was made to the time the 195 batch was send in the SenML. The server might have accurate NTP time 196 and use the time it received the data, and the relative offset, to 197 replace the times in the SenML with absolute times before saving the 198 SenML in a document database. 200 3. Terminology 202 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 203 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 204 "OPTIONAL" in this document are to be interpreted as described in 205 [RFC2119]. 207 4. Semantics 209 Each SenML representation carries a single array that represents a 210 set of measurements and/or parameters. This array contains a series 211 of objects with several optional attributes described below: 213 Base Name: This is a string that is prepended to the names found in 214 the entries. This attribute is optional. This applies to the 215 entries in all Records. A Base Name can only be included in the 216 first Record of the array. 218 Base Time: A base time that is added to the time found in an entry. 219 This attribute is optional. This applies to the entries in all 220 Records. A Base Time can only be included in the first Record of 221 the array. 223 Base Unit: A base unit that is assumed for all entries, unless 224 otherwise indicated. This attribute is optional. If a record 225 does not contain a unit value, then the base unit is used 226 otherwise the value of found in the Unit is used. This applies to 227 the entries in all Records. A Base Unit can only be included in 228 the first object of the array. 230 Links: An array of objects that can be used for additional 231 information. A Links element can only be included in the first 232 object of the array. Each object in the Link array is constrained 233 to being a map of strings to strings with unique keys. 235 Version: Version number of media type format. This attribute is 236 optional positive integer and defaults to 5 if not present. A 237 Version can only be included in the first object of the array. 239 Name: Name of the sensor or parameter. When appended to the Base 240 Name attribute, this must result in a globally unique identifier 241 for the resource. The name is optional, if the Base Name is 242 present. If the name is missing, Base Name must uniquely identify 243 the resource. This can be used to represent a large array of 244 measurements from the same sensor without having to repeat its 245 identifier on every measurement. 247 Unit: Units for a measurement value. Optional. If the Record has 248 not Unit, the Base Unit is used as the Unit. Having no Unit and 249 no Base Unit is allowed. 251 Value Value of the entry. Optional if a Sum value is present, 252 otherwise required. Values are represented using three basic data 253 types, Floating point numbers ("v" field for "Value"), Booleans 254 ("vb" for "Boolean Value"), Strings ("vs" for "String Value") and 255 Data ("vd" for "Binary Data Value") . Exactly one of these three 256 fields MUST appear unless there is Sum field in which case it is 257 allowed to have no Value field or to have "v" field. 259 Sum: Integrated sum of the values over time. Optional. This 260 attribute is in the units specified in the Unit value multiplied 261 by seconds. 263 Time: Time when value was recorded. Optional. 265 Update Time: An optional time in seconds that represents the maximum 266 time before this sensor will provide an updated reading for a 267 measurement. This can be used to detect the failure of sensors or 268 communications path from the sensor. 270 The SenML format can be extended with further custom attributes. 271 TODO - describe what extensions are possible and how to do them. 273 Systems reading one of the objects MUST check for the Version 274 attribute. If this value is a version number larger than the version 275 which the system understands, the system SHOULD NOT use this object. 276 This allows the version number to indicate that the object contains 277 mandatory to understand attributes. New version numbers can only be 278 defined in an RFC that updates this specification or it successors. 280 The Name value is concatenated to the Base Name value to get the name 281 of the sensor. The resulting name needs to uniquely identify and 282 differentiate the sensor from all others. If the object is a 283 representation resulting from the request of a URI [RFC3986], then in 284 the absence of the Base Name attribute, this URI is used as the 285 default value of Base Name. Thus in this case the Name field needs 286 to be unique for that URI, for example an index or subresource name 287 of sensors handled by the URI. 289 Alternatively, for objects not related to a URI, a unique name is 290 required. In any case, it is RECOMMENDED that the full names are 291 represented as URIs or URNs [RFC2141]. One way to create a unique 292 name is to include some bit string that has guaranteed uniqueness 293 (such as a 1-wire address) that is assigned to the device. Some of 294 the examples in this draft use the device URN type as specified in 295 [I-D.arkko-core-dev-urn]. UUIDs [RFC4122] are another way to 296 generate a unique name. TODO - discuss privacy implications of 297 stable hardware addresses. 299 The resulting concatenated name MUST consist only of characters out 300 of the set "A" to "Z", "a" to "z", "0" to "9", "-", ":", ".", or "_" 301 and it MUST start with a character out of the set "A" to "Z", "a" to 302 "z", or "0" to "9". This restricted character set was chosen so that 303 these names can be directly used as in other types of URI including 304 segments of an HTTP path with no special encoding and can be directly 305 used in many databases and analytic systems. [RFC5952] contains 306 advice on encoding an IPv6 address in a name. 308 If either the Base Time or Time value is missing, the missing 309 attribute is considered to have a value of zero. The Base Time and 310 Time values are added together to get the time of measurement. A 311 time of zero indicates that the sensor does not know the absolute 312 time and the measurement was made roughly "now". A negative value is 313 used to indicate seconds in the past from roughly "now". A positive 314 value is used to indicate the number of seconds, excluding leap 315 seconds, since the start of the year 1970 in UTC. 317 Representing the statistical characteristics of measurements, such as 318 accuracy, can be very complex. Future specification may add new 319 attributes to provide better information about the statistical 320 properties of the measurement. 322 5. Associating Meta-data 324 SenML is designed to carry the minimum dynamic information about 325 measurements, and for efficiency reasons does not carry significant 326 static meta-data about the device, object or sensors. Instead, it is 327 assumed that this meta-data is carried out of band. For web 328 resources using SenML representations, this meta-data can be made 329 available using the CoRE Link Format [RFC6690]. The most obvious use 330 of this link format is to describe that a resource is available in a 331 SenML format in the first place. The relevant media type indicator 332 is included in the Content-Type (ct=) attribute. 334 6. JSON Representation (application/senml+json) 336 Record atributes: 338 +---------------+------+------------------+ 339 | SenML | JSON | Type | 340 +---------------+------+------------------+ 341 | Base Name | bn | String | 342 | Base Time | bt | Number | 343 | Base Unit | bu | Number | 344 | Version | ver | Number | 345 | Name | n | String | 346 | Unit | u | String | 347 | Value | v | Floating point | 348 | String Value | vs | String | 349 | Boolean Value | vb | Boolean | 350 | Data Value | vd | String | 351 | Value Sum | s | Floating point | 352 | Time | t | Number | 353 | Update Time | ut | Number | 354 | Links | l | Array of objects | 355 +---------------+------+------------------+ 357 The root content consists of an array with and JSON objects for each 358 SenML Record. All the fields in the above table MAY occur in the 359 records with the type specified in the table. 361 Only the UTF-8 form of JSON is allowed. Characters in the String 362 Value are encoded using the escape sequences defined in [RFC4627]. 363 Characters in the Data Value are base64 encoded with URL safe 364 alphabet as defined in Section 5 of [RFC4648]. 366 Systems receiving measurements MUST be able to process the range of 367 floating point numbers that are representable as an IEEE double- 368 precision floating-point numbers [IEEE.754.1985]. The number of 369 significant digits in any measurement is not relevant, so a reading 370 of 1.1 has exactly the same semantic meaning as 1.10. If the value 371 has an exponent, the "e" MUST be in lower case. The mantissa SHOULD 372 be less than 19 characters long and the exponent SHOULD be less than 373 5 characters long. This allows time values to have better than micro 374 second precision over the next 100 years. 376 6.1. Examples 378 TODO - simplify examples 380 TODO - Examples are messed up on if time is an integer or float 382 TODO - Add example with string , data , boolean 384 6.1.1. Single Datapoint 386 The following shows a temperature reading taken approximately "now" 387 by a 1-wire sensor device that was assigned the unique 1-wire address 388 of 10e2073a01080063: 390 [{ "n": "urn:dev:ow:10e2073a01080063", "v":23.1, "u":"Cel" }] 392 6.1.2. Multiple Datapoints 394 The following example shows voltage and current now, i.e., at an 395 unspecified time. The device has an EUI-64 MAC address of 396 0024befffe804ff1. 398 [{"bn": "urn:dev:mac:0024befffe804ff1/"}, 399 { "n": "voltage", "t": 0, "u": "V", "v": 120.1 }, 400 { "n": "current", "t": 0, "u": "A", "v": 1.2 } 401 ] 403 The next example is similar to the above one, but shows current at 404 Tue Jun 8 18:01:16 UTC 2010 and at each second for the previous 5 405 seconds. 407 [{"bn": "urn:dev:mac:0024befffe804ff1/", 408 "bt": 1276020076, 409 "bu": "A", 410 "ver": 5}, 411 { "n": "voltage", "u": "V", "v": 120.1 }, 412 { "n": "current", "t": -5, "v": 1.2 }, 413 { "n": "current", "t": -4, "v": 1.30 }, 414 { "n": "current", "t": -3, "v": 0.14e1 }, 415 { "n": "current", "t": -2, "v": 1.5 }, 416 { "n": "current", "t": -1, "v": 1.6 }, 417 { "n": "current", "t": 0, "v": 1.7 } 418 ] 420 Note that in some usage scenarios of SenML the implementations MAY 421 store or transmit SenML in a stream-like fashion, where data is 422 collected over time and continuously added to the object. This mode 423 of operation is optional, but systems or protocols using SenML in 424 this fashion MUST specify that they are doing this. SenML defines a 425 separate mime type (TODO) to indicate Sensor Streaming Markup 426 Language (SensML) for this usage. In this situation the SensML 427 stream can be sent and received in a partial fashion, i.e., a 428 measurement entry can be read as soon as the SenML Record is received 429 and not have to wait for the full SensML Stream to be complete. 431 For instance, the following stream of measurements may be sent via a 432 long lived HTTP POST from the producer of a SensML to the consumer of 433 that, and each measurement object may be reported at the time it 434 measured: 436 [ {"bn": "http://[2001:db8::1]", 437 "bt": 1320067464, 438 "bu": "%RH"}, 439 { "v": 21.2, "t": 0 }, 440 { "v": 21.3, "t": 10 }, 441 { "v": 21.4, "t": 20 }, 442 { "v": 21.4, "t": 30 }, 443 { "v": 21.5, "t": 40 }, 444 { "v": 21.5, "t": 50 }, 445 { "v": 21.5, "t": 60 }, 446 { "v": 21.6, "t": 70 }, 447 { "v": 21.7, "t": 80 }, 448 { "v": 21.5, "t": 90 }, 449 ... 451 6.1.3. Multiple Measurements 453 The following example shows humidity measurements from a mobile 454 device with an IPv6 address 2001:db8::1, starting at Mon Oct 31 455 13:24:24 UTC 2011. The device also provides position data, which is 456 provided in the same measurement or parameter array as separate 457 entries. Note time is used to for correlating data that belongs 458 together, e.g., a measurement and a parameter associated with it. 459 Finally, the device also reports extra data about its battery status 460 at a separate time. 462 [{"bn": "http://[2001:db8::1]", 463 "bt": 1320067464, 464 "bu": "%RH"}, 465 { "v": 20.0, "t": 0 }, 466 { "v": 24.30621, "u": "lon", "t": 0 }, 467 { "v": 60.07965, "u": "lat", "t": 0 }, 468 { "v": 20.3, "t": 60 }, 469 { "v": 24.30622, "u": "lon", "t": 60 }, 470 { "v": 60.07965, "u": "lat", "t": 60 }, 471 { "v": 20.7, "t": 120 }, 472 { "v": 24.30623, "u": "lon", "t": 120 }, 473 { "v": 60.07966, "u": "lat", "t": 120 }, 474 { "v": 98.0, "u": "%EL", "t": 150 }, 475 { "v": 21.2, "t": 180 }, 476 { "v": 24.30628, "u": "lon", "t": 180 }, 477 { "v": 60.07967, "u": "lat", "t": 180 } 478 ] 480 The size of this example represented in various forms, as well as 481 that form compressed with gzip is given in the following table. 483 +----------+------+-----------------+ 484 | Encoding | Size | Compressed Size | 485 +----------+------+-----------------+ 486 | JSON | 567 | 200 | 487 | XML | 656 | 232 | 488 | CBOR | 292 | 192 | 489 | EXI | 160 | 183 | 490 +----------+------+-----------------+ 492 Table 1: Size Comparisons 494 Note the CBOR and EXI sizes are not using the schema guidance so the 495 could be a bit smaller. 497 6.1.4. Collection of Resources 499 The following example shows how to query one device that can provide 500 multiple measurements. The example assumes that a client has fetched 501 information from a device at 2001:db8::2 by performing a GET 502 operation on http://[2001:db8::2] at Mon Oct 31 16:27:09 UTC 2011, 503 and has gotten two separate values as a result, a temperature and 504 humidity measurement. 506 This example also shows a possible use of the link extension. 508 [{"bn": "http://[2001:db8::2]/", 509 "bt": 1320078429, 510 "ver": 5, 511 "l": [{"href":"humidity","foo":"bar1"}, 512 {"href":"temperature","foo":"bar2","bar":"foo3"}] 513 }, 514 { "n": "temperature", "v": 27.2, "u": "Cel" }, 515 { "n": "humidity", "v": 80, "u": "%RH" } 516 ] 518 7. CBOR Representation (application/senml+cbor) 520 The CBOR [RFC7049] representation is equivalent to the JSON 521 representation, with the following changes: 523 o For compactness, the CBOR representation uses integers for the map 524 keys defined in Table 2. This table is conclusive, i.e., there is 525 no intention to define any additional integer map keys; any 526 extensions will use string map keys. 528 o For JSON Numbers, the CBOR representation can use integers, 529 floating point numbers, or decimal fractions (CBOR Tag 4); the 530 common limitations of JSON implementations are not relevant for 531 these. For the version number, however, only an unsigned integer 532 is allowed. 534 +---------------+------------+------------+ 535 | Name | JSON label | CBOR label | 536 +---------------+------------+------------+ 537 | Version | ver | -1 | 538 | Base Name | bn | -2 | 539 | Base Time | bt | -3 | 540 | Base Units | bu | -4 | 541 | Links | l | -5 | 542 | Name | n | 0 | 543 | Units | u | 1 | 544 | Value | v | 2 | 545 | String Value | vs | 3 | 546 | Boolean Value | vb | 4 | 547 | Value Sum | s | 5 | 548 | Time | t | 6 | 549 | Update Time | ut | 7 | 550 | Data Value | vd | 8 | 551 +---------------+------------+------------+ 553 Table 2: CBOR representation: integers for map keys 555 The following example shows an hexdump of the CBOR example for the 556 same sensor measurement as in Section 6.1.2. 558 0000 88 a4 62 62 6e 78 1d 75 72 6e 3a 64 65 76 3a 6d |..bbnx.urn:dev:m| 559 0010 61 63 3a 30 30 32 34 62 65 66 66 66 65 38 30 34 |ac:0024befffe804| 560 0020 66 66 31 2f 62 62 74 1a 4c 0e 85 6c 62 62 75 61 |ff1/bbt.L..lbbua| 561 0030 41 63 76 65 72 05 a3 61 6e 67 76 6f 6c 74 61 67 |Acver..angvoltag| 562 0040 65 61 75 61 56 61 76 fb 40 5e 06 66 66 66 66 66 |eauaVav.@^.fffff| 563 0050 a3 61 6e 67 63 75 72 72 65 6e 74 61 74 24 61 76 |.angcurrentat$av| 564 0060 fb 3f f3 33 33 33 33 33 33 a3 61 6e 67 63 75 72 |.?.333333.angcur| 565 0070 72 65 6e 74 61 74 23 61 76 fb 3f f4 cc cc cc cc |rentat#av.?.....| 566 0080 cc cd a3 61 6e 67 63 75 72 72 65 6e 74 61 74 22 |...angcurrentat"| 567 0090 61 76 fb 3f f6 66 66 66 66 66 66 a3 61 6e 67 63 |av.?.ffffff.angc| 568 00a0 75 72 72 65 6e 74 61 74 21 61 76 fb 3f f8 00 00 |urrentat!av.?...| 569 00b0 00 00 00 00 a3 61 6e 67 63 75 72 72 65 6e 74 61 |.....angcurrenta| 570 00c0 74 20 61 76 fb 3f f9 99 99 99 99 99 9a a2 61 6e |t av.?........an| 571 00d0 67 63 75 72 72 65 6e 74 61 76 fb 3f fb 33 33 33 |gcurrentav.?.333| 572 00e0 33 33 33 0a |333.| 573 00e4 575 8. XML Representation (application/senml+xml) 577 A SenML Stream can also be represented in XML format as defined in 578 this section. The following example shows an XML example for the 579 same sensor measurement as in Section 6.1.2. 581 582 584 585 586 587 588 589 590 591 593 The SenML Stream is represented as a sensml tag that contains a 594 series of senml tags for each SenML Record. The SenML Fields are 595 represents as XML attributes. The following table shows the mapping 596 the SenML Field names to the attribute used in the XML senml tag. 598 +---------------+-----+---------+ 599 | SenML Field | XML | Type | 600 +---------------+-----+---------+ 601 | Base Name | bn | string | 602 | Base Time | bt | int | 603 | Base Unit | bu | int | 604 | Links | l | XML tag | 605 | Version | ver | int | 606 | Name | n | string | 607 | Unit | u | string | 608 | Value | v | float | 609 | String Value | vs | string | 610 | Data Value | vd | string | 611 | Boolean Value | vb | boolean | 612 | Value Sum | s | float | 613 | Time | t | int | 614 | Update Time | ut | int | 615 +---------------+-----+---------+ 617 TODO - Discuss encoding of String and Data 619 The RelaxNG schema for the XML is: 621 default namespace = "urn:ietf:params:xml:ns:senml" 622 namespace rng = "http://relaxng.org/ns/structure/1.0" 624 link = element l { 625 attribute * { xsd:string }* 626 } 628 senml = element senml { 629 attribute bn { xsd:string }?, 630 attribute bt { xsd:int }?, 631 attribute bu { xsd:string }?, 632 attribute n { xsd:string }?, 633 attribute s { xsd:float }?, 634 attribute t { xsd:int }?, 635 attribute u { xsd:string }?, 636 attribute ut { xsd:int }?, 637 attribute v { xsd:float }?, 638 attribute vb { xsd:boolean }?, 639 attribute ver { xsd:int }?, 640 attribute vs { xsd:string }?, 642 link* 643 } 645 sensml = 646 element sensml { 647 senml+ 648 } 650 start = sensml 652 9. EXI Representation (application/senml-exi) 654 For efficient transmission of SenML over e.g. a constrained network, 655 Efficient XML Interchange (EXI) can be used. This encodes the XML 656 Schema structure of SenML into binary tags and values rather than 657 ASCII text. An EXI representation of SenML SHOULD be made using the 658 strict schema-mode of EXI. This mode however does not allow tag 659 extensions to the schema, and therefore any extensions will be lost 660 in the encoding. For uses where extensions need to be preserved in 661 EXI, the non-strict schema mode of EXI MAY be used. 663 The EXI header option MUST be included. An EXI schemaID options MUST 664 be set to the value of "a" indicating the scheme provided in this 665 specification. Future revisions to the schema can change this 666 schemaID to allow for backwards compatibility. When the data will be 667 transported over CoAP or HTTP, an EXI Cookie SHOULD NOT be used as it 668 simply makes things larger and is redundant to information provided 669 in the Content-Type header. 671 TODO - examples probably have the wrong setting the schemaID 673 The following is the XSD Schema to be used for strict schema guided 674 EXI processing. It is generated from the RelaxNG. 676 677 681 682 683 684 685 686 687 688 689 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 The following shows a hexdump of the EXI produced from encoding the 715 following XML example. Note this example is the same information as 716 the first example in Section 6.1.2 in JSON format. 718 719 720 721 722 724 Which compresses with EXI to the following displayed in hexdump: 726 0000 a0 30 41 cd 95 b9 b5 b0 d4 b9 9d 95 b8 b9 e1 cd |.0A.............| 727 0010 91 00 fb ab 93 71 d3 23 2b b1 d3 6b 0b 19 d1 81 |.....q.#+..k....| 728 0020 81 91 a3 13 2b 33 33 33 29 c1 81 a3 33 31 89 7e |....+333)...31.~| 729 0030 0c 25 d9 bd b1 d1 85 9d 94 80 d5 8a c4 26 01 06 |.%...........&..| 730 0040 12 c6 ea e4 e4 ca dc e8 40 68 24 19 00 90 |........@h$...| 731 004e 733 The above example used the bit packed form of EXI but it is also 734 possible to use a byte packed form of EXI which can makes it easier 735 for a simple sensor to produce valid EXI without really implementing 736 EXI. Consider the example of a temperature sensor that produces a 737 value in tenths of degrees Celsius over a range of 0.0 to 55.0. It 738 would produce an XML SenML file such as: 740 741 742 744 The compressed form, using the byte alignment option of EXI, for the 745 above XML is the following: 747 0000 a0 00 48 82 0e 6c ad cd ad 86 a5 cc ec ad c5 cf |..H..l..........| 748 0010 0e 6c 80 02 03 1d 75 72 6e 3a 64 65 76 3a 6f 77 |.l....urn:dev:ow| 749 0020 3a 31 30 65 32 30 37 33 61 30 31 30 38 30 30 36 |:10e2073a0108006| 750 0030 33 02 05 43 65 6c 01 00 e7 01 01 00 04 01 |3..Cel........| 751 003e 753 A small temperature sensor devices that only generates this one EXI 754 file does not really need an full EXI implementation. It can simple 755 hard code the output replacing the one wire device ID starting at 756 byte 0x16 and going to byte 0x31 with it's device ID, and replacing 757 the value "0xe7 0x01" at location 0x38 to 0x39 with the current 758 temperature. The EXI Specification [W3C.REC-exi-20110310] contains 759 the full information 'on how floating point numbers are represented, 760 but for the purpose of this sensor, the temperature can be converted 761 to an integer in tenths of degrees (231 in this example). EXI stores 762 7 bits of the integer in each byte with the top bit set to one if 763 there are further bytes. So the first bytes at is set to low 7 bits 764 of the integer temperature in tenths of degrees plus 0x80. In this 765 example 231 & 0x7F + 0x80 = 0xE7. The second byte is set to the 766 integer temperature in tenths of degrees right shifted 7 bits. In 767 this example 231 >> 7 = 0x01. 769 10. Usage Considerations 771 The measurements support sending both the current value of a sensor 772 as well as the an integrated sum. For many types of measurements, 773 the sum is more useful than the current value. For example, an 774 electrical meter that measures the energy a given computer uses will 775 typically want to measure the cumulative amount of energy used. This 776 is less prone to error than reporting the power each second and 777 trying to have something on the server side sum together all the 778 power measurements. If the network between the sensor and the meter 779 goes down over some period of time, when it comes back up, the 780 cumulative sum helps reflect what happened while the network was 781 down. A meter like this would typically report a measurement with 782 the units set to watts, but it would put the sum of energy used in 783 the "s" attribute of the measurement. It might optionally include 784 the current power in the "v" attribute. 786 While the benefit of using the integrated sum is fairly clear for 787 measurements like power and energy, it is less obvious for something 788 like temperature. Reporting the sum of the temperature makes it easy 789 to compute averages even when the individual temperature values are 790 not reported frequently enough to compute accurate averages. 791 Implementors are encouraged to report the cumulative sum as well as 792 the raw value of a given sensor. 794 Applications that use the cumulative sum values need to understand 795 they are very loosely defined by this specification, and depending on 796 the particular sensor implementation may behave in unexpected ways. 797 Applications should be able to deal with the following issues: 799 1. Many sensors will allow the cumulative sums to "wrap" back to 800 zero after the value gets sufficiently large. 802 2. Some sensors will reset the cumulative sum back to zero when the 803 device is reset, loses power, or is replaced with a different 804 sensor. 806 3. Applications cannot make assumptions about when the device 807 started accumulating values into the sum. 809 Typically applications can make some assumptions about specific 810 sensors that will allow them to deal with these problems. A common 811 assumption is that for sensors whose measurement values are always 812 positive, the sum should never get smaller; so if the sum does get 813 smaller, the application will know that one of the situations listed 814 above has happened. 816 11. IANA Considerations 818 Note to RFC Editor: Please replace all occurrences of "RFC-AAAA" with 819 the RFC number of this specification. 821 11.1. Units Registry 823 IANA will create a registry of unit symbols. The primary purpose of 824 this registry is to make sure that symbols uniquely map to give type 825 of measurement. Definitions for many of these units can be found in 826 location such as [NIST811] and [BIPM]. 828 +--------+--------------------------------------+-------+-----------+ 829 | Symbol | Description | Type | Reference | 830 +--------+--------------------------------------+-------+-----------+ 831 | m | meter | float | RFC-AAAA | 832 | g | gram | float | RFC-AAAA | 833 | s | second | float | RFC-AAAA | 834 | A | ampere | float | RFC-AAAA | 835 | K | kelvin | float | RFC-AAAA | 836 | cd | candela | float | RFC-AAAA | 837 | mol | mole | float | RFC-AAAA | 838 | Hz | hertz | float | RFC-AAAA | 839 | rad | radian | float | RFC-AAAA | 840 | sr | steradian | float | RFC-AAAA | 841 | N | newton | float | RFC-AAAA | 842 | Pa | pascal | float | RFC-AAAA | 843 | J | joule | float | RFC-AAAA | 844 | W | watt | float | RFC-AAAA | 845 | C | coulomb | float | RFC-AAAA | 846 | V | volt | float | RFC-AAAA | 847 | F | farad | float | RFC-AAAA | 848 | Ohm | ohm | float | RFC-AAAA | 849 | S | siemens | float | RFC-AAAA | 850 | Wb | weber | float | RFC-AAAA | 851 | T | tesla | float | RFC-AAAA | 852 | H | henry | float | RFC-AAAA | 853 | Cel | degrees Celsius | float | RFC-AAAA | 854 | lm | lumen | float | RFC-AAAA | 855 | lx | lux | float | RFC-AAAA | 856 | Bq | becquerel | float | RFC-AAAA | 857 | Gy | gray | float | RFC-AAAA | 858 | Sv | sievert | float | RFC-AAAA | 859 | kat | katal | float | RFC-AAAA | 860 | pH | pH acidity | float | RFC-AAAA | 861 | % | Value of a switch (note 1) | float | RFC-AAAA | 862 | count | counter value | float | RFC-AAAA | 863 | %RH | Relative Humidity | float | RFC-AAAA | 864 | m2 | area | float | RFC-AAAA | 865 | l | volume in liters | float | RFC-AAAA | 866 | m/s | velocity | float | RFC-AAAA | 867 | m/s2 | acceleration | float | RFC-AAAA | 868 | l/s | flow rate in liters per second | float | RFC-AAAA | 869 | W/m2 | irradiance | float | RFC-AAAA | 870 | cd/m2 | luminance | float | RFC-AAAA | 871 | Bspl | bel sound pressure level | float | RFC-AAAA | 872 | bit/s | bits per second | float | RFC-AAAA | 873 | lat | degrees latitude (note 2) | float | RFC-AAAA | 874 | lon | degrees longitude (note 2) | float | RFC-AAAA | 875 | %EL | remaining battery energy level in | float | RFC-AAAA | 876 | | percents | | | 877 | EL | remaining battery energy level in | float | RFC-AAAA | 878 | | seconds | | | 879 | beat/m | Heart rate in beats per minute | float | RFC-AAAA | 880 | beats | Cumulative number of heart beats | float | RFC-AAAA | 881 +--------+--------------------------------------+-------+-----------+ 883 Table 3 885 o Note 1: A value of 0.0 indicates the switch is off while 1.0 886 indicates on and 0.5 would be half on. 888 o Note 2: Assumed to be in WGS84 unless another reference frame is 889 known for the sensor. 891 New entries can be added to the registration by either Expert Review 892 or IESG Approval as defined in [RFC5226]. Experts should exercise 893 their own good judgment but need to consider the following 894 guidelines: 896 1. There needs to be a real and compelling use for any new unit to 897 be added. 899 2. Units should define the semantic information and be chosen 900 carefully. Implementors need to remember that the same word may 901 be used in different real-life contexts. For example, degrees 902 when measuring latitude have no semantic relation to degrees 903 when measuring temperature; thus two different units are needed. 905 3. These measurements are produced by computers for consumption by 906 computers. The principle is that conversion has to be easily be 907 done when both reading and writing the media type. The value of 908 a single canonical representation outweighs the convenience of 909 easy human representations or loss of precision in a conversion. 911 4. Use of SI prefixes such as "k" before the unit is not allowed. 912 Instead one can represent the value using scientific notation 913 such a 1.2e3. TODO - Open Issue. Some people would like to 914 have SI prefixes to improve human readability. 916 5. For a given type of measurement, there will only be one unit 917 type defined. So for length, meters are defined and other 918 lengths such as mile, foot, light year are not allowed. For 919 most cases, the SI unit is preferred. 921 6. Symbol names that could be easily confused with existing common 922 units or units combined with prefixes should be avoided. For 923 example, selecting a unit name of "mph" to indicate something 924 that had nothing to do with velocity would be a bad choice, as 925 "mph" is commonly used to mean miles per hour. 927 7. The following should not be used because the are common SI 928 prefixes: Y, Z, E, P, T, G, M, k, h, da, d, c, n, u, p, f, a, z, 929 y, Ki, Mi, Gi, Ti, Pi, Ei, Zi, Yi. 931 8. The following units should not be used as they are commonly used 932 to represent other measurements Ky, Gal, dyn, etg, P, St, Mx, G, 933 Oe, Gb, sb, Lmb, ph, Ci, R, RAD, REM, gal, bbl, qt, degF, Cal, 934 BTU, HP, pH, B/s, psi, Torr, atm, at, bar, kWh. 936 9. The unit names are case sensitive and the correct case needs to 937 be used, but symbols that differ only in case should not be 938 allocated. 940 10. A number after a unit typically indicates the previous unit 941 raised to that power, and the / indicates that the units that 942 follow are the reciprocal. A unit should have only one / in the 943 name. 945 11. A good list of common units can be found in the Unified Code for 946 Units of Measure [UCUM]. 948 11.2. Media Type Registration 950 The following registrations are done following the procedure 951 specified in [RFC6838] and [RFC7303]. 953 11.2.1. senml+json Media Type Registration 955 Type name: application 957 Subtype name: senml+json and sensml+json 959 Required parameters: none 961 Optional parameters: none 963 Encoding considerations: Must be encoded as using a subset of the 964 encoding allowed in [RFC7159]. See RFC-AAAA for details. This 965 simplifies implementation of very simple system and does not impose 966 any significant limitations as all this data is meant for machine to 967 machine communications and is not meant to be human readable. 969 Security considerations: Sensor data can contain a wide range of 970 information ranging from information that is very public, such the 971 outside temperature in a given city, to very private information that 972 requires integrity and confidentiality protection, such as patient 973 health information. This format does not provide any security and 974 instead relies on the transport protocol that carries it to provide 975 security. Given applications need to look at the overall context of 976 how this media type will be used to decide if the security is 977 adequate. 979 Interoperability considerations: Applications should ignore any JSON 980 key value pairs that they do not understand. This allows backwards 981 compatibility extensions to this specification. The "ver" field can 982 be used to ensure the receiver supports a minimal level of 983 functionality needed by the creator of the JSON object. 985 Published specification: RFC-AAAA 987 Applications that use this media type: The type is used by systems 988 that report electrical power usage and environmental information such 989 as temperature and humidity. It can be used for a wide range of 990 sensor reporting systems. 992 Additional information: 994 Magic number(s): none 996 File extension(s): senml 998 Macintosh file type code(s): none 999 Person & email address to contact for further information: Cullen 1000 Jennings 1002 Intended usage: COMMON 1004 Restrictions on usage: None 1006 Author: Cullen Jennings 1008 Change controller: IESG 1010 11.2.2. senml+cbor Media Type Registration 1012 Type name: application 1014 Subtype name: senml+cbor 1016 Required parameters: none 1018 Optional parameters: none 1020 Encoding considerations: TBD 1022 Security considerations: TBD 1024 Interoperability considerations: TBD 1026 Published specification: RFC-AAAA 1028 Applications that use this media type: The type is used by systems 1029 that report electrical power usage and environmental information such 1030 as temperature and humidity. It can be used for a wide range of 1031 sensor reporting systems. 1033 Additional information: 1035 Magic number(s): none 1037 File extension(s): senml 1039 Macintosh file type code(s): none 1041 Person & email address to contact for further information: Cullen 1042 Jennings 1044 Intended usage: COMMON 1046 Restrictions on usage: None 1047 Author: Cullen Jennings 1049 Change controller: IESG 1051 11.2.3. senml+xml Media Type Registration 1053 Type name: application 1055 Subtype name: senml+xml and sensml+xml 1057 Required parameters: none 1059 Optional parameters: none 1061 Encoding considerations: TBD 1063 Security considerations: TBD 1065 Interoperability considerations: TBD 1067 Published specification: RFC-AAAA 1069 Applications that use this media type: TBD 1071 Additional information: 1073 Magic number(s): none 1075 File extension(s): senml 1077 Macintosh file type code(s): none 1079 Person & email address to contact for further information: Cullen 1080 Jennings 1082 Intended usage: COMMON 1084 Restrictions on usage: None 1086 Author: Cullen Jennings 1088 Change controller: IESG 1090 11.2.4. senml-exi Media Type Registration 1092 Type name: application 1094 Subtype name: senml-exi 1095 Required parameters: none 1097 Optional parameters: none 1099 Encoding considerations: TBD 1101 Security considerations: TBD 1103 Interoperability considerations: TBD 1105 Published specification: RFC-AAAA 1107 Applications that use this media type: TBD 1109 Additional information: 1111 Magic number(s): none 1113 File extension(s): senml 1115 Macintosh file type code(s): none 1117 Person & email address to contact for further information: Cullen 1118 Jennings 1120 Intended usage: COMMON 1122 Restrictions on usage: None 1124 Author: Cullen Jennings 1126 Change controller: IESG 1128 11.3. XML Namespace Registration 1130 This document registers the following XML namespaces in the IETF XML 1131 registry defined in [RFC3688]. 1133 URI: urn:ietf:params:xml:ns:senml 1135 Registrant Contact: The IESG. 1137 XML: N/A, the requested URIs are XML namespaces 1139 11.4. CoAP Content-Format Registration 1141 IANA is requested to assign CoAP Content-Format IDs for the SenML 1142 media types in the "CoAP Content-Formats" sub-registry, within the 1143 "CoRE Parameters" registry [RFC7252]. All IDs are assigned from the 1144 "Expert Review" (0-255) range. The assigned IDs are show in Table 4. 1146 +-------------------------+-----+ 1147 | Media type | ID | 1148 +-------------------------+-----+ 1149 | application/senml+json | TBD | 1150 | application/sensml+json | TBD | 1151 | application/senml+cbor | TBD | 1152 | application/senml+xml | TBD | 1153 | application/sensml+xml | TBD | 1154 | application/senml-exi | TBD | 1155 +-------------------------+-----+ 1157 Table 4: CoAP Content-Format IDs 1159 12. Security Considerations 1161 See Section 13. Further discussion of security properties can be 1162 found in Section 11.2. 1164 13. Privacy Considerations 1166 Sensor data can range from information with almost no security 1167 considerations, such as the current temperature in a given city, to 1168 highly sensitive medical or location data. This specification 1169 provides no security protection for the data but is meant to be used 1170 inside another container or transport protocol such as S/MIME or HTTP 1171 with TLS that can provide integrity, confidentiality, and 1172 authentication information about the source of the data. 1174 14. Acknowledgement 1176 We would like to thank Lisa Dusseault, Joe Hildebrand, Lyndsay 1177 Campbell, Martin Thomson, John Klensin, Bjoern Hoehrmann, Carsten 1178 Bormann, and Christian Amsuess for their review comments. 1180 The CBOR Representation text was contributed by Carsten Bormann. 1182 15. References 1183 15.1. Normative References 1185 [BIPM] Bureau International des Poids et Mesures, "The 1186 International System of Units (SI)", 8th edition, 2006. 1188 [IEEE.754.1985] 1189 Institute of Electrical and Electronics Engineers, 1190 "Standard for Binary Floating-Point Arithmetic", IEEE 1191 Standard 754, August 1985. 1193 [NIST811] Thompson, A. and B. Taylor, "Guide for the Use of the 1194 International System of Units (SI)", NIST Special 1195 Publication 811, 2008. 1197 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1198 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 1199 RFC2119, March 1997, 1200 . 1202 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 1203 DOI 10.17487/RFC3688, January 2004, 1204 . 1206 [RFC4627] Crockford, D., "The application/json Media Type for 1207 JavaScript Object Notation (JSON)", RFC 4627, DOI 1208 10.17487/RFC4627, July 2006, 1209 . 1211 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 1212 Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, 1213 . 1215 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1216 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1217 DOI 10.17487/RFC5226, May 2008, 1218 . 1220 [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type 1221 Specifications and Registration Procedures", BCP 13, RFC 1222 6838, DOI 10.17487/RFC6838, January 2013, 1223 . 1225 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 1226 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 1227 October 2013, . 1229 [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1230 Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 1231 2014, . 1233 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 1234 Application Protocol (CoAP)", RFC 7252, DOI 10.17487/ 1235 RFC7252, June 2014, 1236 . 1238 [RFC7303] Thompson, H. and C. Lilley, "XML Media Types", RFC 7303, 1239 DOI 10.17487/RFC7303, July 2014, 1240 . 1242 [W3C.REC-exi-20110310] 1243 Schneider, J. and T. Kamiya, "Efficient XML Interchange 1244 (EXI) Format 1.0", World Wide Web Consortium 1245 Recommendation REC-exi-20110310, March 2011, 1246 . 1248 15.2. Informative References 1250 [I-D.arkko-core-dev-urn] 1251 Arkko, J., Jennings, C., and Z. Shelby, "Uniform Resource 1252 Names for Device Identifiers", draft-arkko-core-dev-urn-03 1253 (work in progress), July 2012. 1255 [RFC2141] Moats, R., "URN Syntax", RFC 2141, DOI 10.17487/RFC2141, 1256 May 1997, . 1258 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1259 Resource Identifier (URI): Generic Syntax", STD 66, RFC 1260 3986, DOI 10.17487/RFC3986, January 2005, 1261 . 1263 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 1264 Unique IDentifier (UUID) URN Namespace", RFC 4122, DOI 1265 10.17487/RFC4122, July 2005, 1266 . 1268 [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 1269 Address Text Representation", RFC 5952, DOI 10.17487/ 1270 RFC5952, August 2010, 1271 . 1273 [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link 1274 Format", RFC 6690, DOI 10.17487/RFC6690, August 2012, 1275 . 1277 [UCUM] Schadow, G. and C. McDonald, "The Unified Code for Units 1278 of Measure (UCUM)", Regenstrief Institute and Indiana 1279 University School of Informatics, 2013, 1280 . 1282 Authors' Addresses 1284 Cullen Jennings 1285 Cisco 1286 400 3rd Avenue SW 1287 Calgary, AB T2P 4H2 1288 Canada 1290 Phone: +1 408 421-9990 1291 Email: fluffy@cisco.com 1293 Zach Shelby 1294 ARM 1295 150 Rose Orchard 1296 San Jose 95134 1297 USA 1299 Phone: +1-408-203-9434 1300 Email: zach.shelby@arm.com 1302 Jari Arkko 1303 Ericsson 1304 Jorvas 02420 1305 Finland 1307 Email: jari.arkko@piuha.net 1309 Ari Keranen 1310 Ericsson 1311 Jorvas 02420 1312 Finland 1314 Email: ari.keranen@ericsson.com