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2 Network Working Group C. Jennings
3 Internet-Draft Cisco
4 Intended status: Standards Track Z. Shelby
5 Expires: June 17, 2018 ARM
6 J. Arkko
7 A. Keranen
8 Ericsson
9 C. Bormann
10 Universitaet Bremen TZI
11 December 14, 2017
13 Media Types for Sensor Measurement Lists (SenML)
14 draft-ietf-core-senml-12
16 Abstract
18 This specification defines media types for representing simple sensor
19 measurements and device parameters in the Sensor Measurement Lists
20 (SenML). Representations are defined in JavaScript Object Notation
21 (JSON), Concise Binary Object Representation (CBOR), eXtensible
22 Markup Language (XML), and Efficient XML Interchange (EXI), which
23 share the common SenML data model. A simple sensor, such as a
24 temperature sensor, could use this media type in protocols such as
25 HTTP or CoAP to transport the measurements of the sensor or to be
26 configured.
28 Status of This Memo
30 This Internet-Draft is submitted in full conformance with the
31 provisions of BCP 78 and BCP 79.
33 Internet-Drafts are working documents of the Internet Engineering
34 Task Force (IETF). Note that other groups may also distribute
35 working documents as Internet-Drafts. The list of current Internet-
36 Drafts is at http://datatracker.ietf.org/drafts/current/.
38 Internet-Drafts are draft documents valid for a maximum of six months
39 and may be updated, replaced, or obsoleted by other documents at any
40 time. It is inappropriate to use Internet-Drafts as reference
41 material or to cite them other than as "work in progress."
43 This Internet-Draft will expire on June 17, 2018.
45 Copyright Notice
47 Copyright (c) 2017 IETF Trust and the persons identified as the
48 document authors. All rights reserved.
50 This document is subject to BCP 78 and the IETF Trust's Legal
51 Provisions Relating to IETF Documents
52 (http://trustee.ietf.org/license-info) in effect on the date of
53 publication of this document. Please review these documents
54 carefully, as they describe your rights and restrictions with respect
55 to this document. Code Components extracted from this document must
56 include Simplified BSD License text as described in Section 4.e of
57 the Trust Legal Provisions and are provided without warranty as
58 described in the Simplified BSD License.
60 Table of Contents
62 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
63 2. Requirements and Design Goals . . . . . . . . . . . . . . . . 4
64 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
65 4. SenML Structure and Semantics . . . . . . . . . . . . . . . . 6
66 4.1. Base Fields . . . . . . . . . . . . . . . . . . . . . . . 6
67 4.2. Regular Fields . . . . . . . . . . . . . . . . . . . . . 6
68 4.3. SenML Labels . . . . . . . . . . . . . . . . . . . . . . 7
69 4.4. Considerations . . . . . . . . . . . . . . . . . . . . . 8
70 4.5. Resolved Records . . . . . . . . . . . . . . . . . . . . 10
71 4.6. Associating Meta-data . . . . . . . . . . . . . . . . . . 10
72 4.7. Configuration and Actuation usage . . . . . . . . . . . . 10
73 5. JSON Representation (application/senml+json) . . . . . . . . 11
74 5.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . 12
75 5.1.1. Single Datapoint . . . . . . . . . . . . . . . . . . 12
76 5.1.2. Multiple Datapoints . . . . . . . . . . . . . . . . . 12
77 5.1.3. Multiple Measurements . . . . . . . . . . . . . . . . 13
78 5.1.4. Resolved Data . . . . . . . . . . . . . . . . . . . . 14
79 5.1.5. Multiple Data Types . . . . . . . . . . . . . . . . . 15
80 5.1.6. Collection of Resources . . . . . . . . . . . . . . . 15
81 5.1.7. Setting an Actuator . . . . . . . . . . . . . . . . . 15
82 6. CBOR Representation (application/senml+cbor) . . . . . . . . 16
83 7. XML Representation (application/senml+xml) . . . . . . . . . 18
84 8. EXI Representation (application/senml+exi) . . . . . . . . . 20
85 9. Fragment Identification Methods . . . . . . . . . . . . . . . 23
86 9.1. Fragment Identification Examples . . . . . . . . . . . . 23
87 10. Usage Considerations . . . . . . . . . . . . . . . . . . . . 24
88 11. CDDL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
89 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
90 12.1. Units Registry . . . . . . . . . . . . . . . . . . . . . 26
91 12.2. SenML Label Registry . . . . . . . . . . . . . . . . . . 30
92 12.3. Media Type Registration . . . . . . . . . . . . . . . . 31
93 12.3.1. senml+json Media Type Registration . . . . . . . . . 32
94 12.3.2. sensml+json Media Type Registration . . . . . . . . 33
95 12.3.3. senml+cbor Media Type Registration . . . . . . . . . 34
96 12.3.4. sensml+cbor Media Type Registration . . . . . . . . 35
97 12.3.5. senml+xml Media Type Registration . . . . . . . . . 36
98 12.3.6. sensml+xml Media Type Registration . . . . . . . . . 37
99 12.3.7. senml+exi Media Type Registration . . . . . . . . . 38
100 12.3.8. sensml+exi Media Type Registration . . . . . . . . . 40
101 12.4. XML Namespace Registration . . . . . . . . . . . . . . . 41
102 12.5. CoAP Content-Format Registration . . . . . . . . . . . . 41
103 13. Security Considerations . . . . . . . . . . . . . . . . . . . 41
104 14. Privacy Considerations . . . . . . . . . . . . . . . . . . . 42
105 15. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 42
106 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 42
107 16.1. Normative References . . . . . . . . . . . . . . . . . . 42
108 16.2. Informative References . . . . . . . . . . . . . . . . . 44
109 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45
111 1. Overview
113 Connecting sensors to the Internet is not new, and there have been
114 many protocols designed to facilitate it. This specification defines
115 new media types for carrying simple sensor information in a protocol
116 such as HTTP or CoAP. This format was designed so that processors
117 with very limited capabilities could easily encode a sensor
118 measurement into the media type, while at the same time a server
119 parsing the data could relatively efficiently collect a large number
120 of sensor measurements. SenML can be used for a variety of data flow
121 models, most notably data feeds pushed from a sensor to a collector,
122 and the web resource model where the sensor is requested as a
123 resource representation (e.g., "GET /sensor/temperature").
125 There are many types of more complex measurements and measurements
126 that this media type would not be suitable for. SenML strikes a
127 balance between having some information about the sensor carried with
128 the sensor data so that the data is self describing but it also tries
129 to make that a fairly minimal set of auxiliary information for
130 efficiency reason. Other information about the sensor can be
131 discovered by other methods such as using the CoRE Link Format
132 [RFC6690].
134 SenML is defined by a data model for measurements and simple meta-
135 data about measurements and devices. The data is structured as a
136 single array that contains a series of SenML Records which can each
137 contain fields such as an unique identifier for the sensor, the time
138 the measurement was made, the unit the measurement is in, and the
139 current value of the sensor. Serializations for this data model are
140 defined for JSON [RFC7159], CBOR [RFC7049], XML, and Efficient XML
141 Interchange (EXI) [W3C.REC-exi-20140211].
143 For example, the following shows a measurement from a temperature
144 gauge encoded in the JSON syntax.
146 [
147 {"n":"urn:dev:ow:10e2073a01080063","u":"Cel","v":23.1}
148 ]
150 In the example above, the array has a single SenML Record with a
151 measurement for a sensor named "urn:dev:ow:10e2073a01080063" with a
152 current value of 23.1 degrees Celsius.
154 2. Requirements and Design Goals
156 The design goal is to be able to send simple sensor measurements in
157 small packets from large numbers of constrained devices. Keeping the
158 total size of payload small makes it easy to use SenML also in
159 constrained networks, e.g., in a 6LoWPAN [RFC4944]. It is always
160 difficult to define what small code is, but there is a desire to be
161 able to implement this in roughly 1 KB of flash on a 8 bit
162 microprocessor. Experience with power meters and other large scale
163 deployments has indicated that the solution needs to support allowing
164 multiple measurements to be batched into a single HTTP or CoAP
165 request. This "batch" upload capability allows the server side to
166 efficiently support a large number of devices. It also conveniently
167 supports batch transfers from proxies and storage devices, even in
168 situations where the sensor itself sends just a single data item at a
169 time. The multiple measurements could be from multiple related
170 sensors or from the same sensor but at different times.
172 The basic design is an array with a series of measurements. The
173 following example shows two measurements made at different times.
174 The value of a measurement is given by the "v" field, the time of a
175 measurement is in the "t" field, the "n" field has a unique sensor
176 name, and the unit of the measurement is carried in the "u" field.
178 [
179 {"n":"urn:dev:ow:10e2073a01080063","u":"Cel","t":1.276020076e+09,
180 "v":23.5},
181 {"n":"urn:dev:ow:10e2073a01080063","u":"Cel","t":1.276020091e+09,
182 "v":23.6}
183 ]
185 To keep the messages small, it does not make sense to repeat the "n"
186 field in each SenML Record so there is a concept of a Base Name which
187 is simply a string that is prepended to the Name field of all
188 elements in that record and any records that follow it. So a more
189 compact form of the example above is the following.
191 [
192 {"bn":"urn:dev:ow:10e2073a01080063","u":"Cel","t":1.276020076e+09,
193 "v":23.5},
194 {"u":"Cel","t":1.276020091e+09,
195 "v":23.6}
196 ]
198 In the above example the Base Name is in the "bn" field and the "n"
199 fields in each Record are the empty string so they are omitted.
201 Some devices have accurate time while others do not so SenML supports
202 absolute and relative times. Time is represented in floating point
203 as seconds and values greater than zero represent an absolute time
204 relative to the Unix epoch while values of 0 or less represent a
205 relative time in the past from the current time. A simple sensor
206 with no absolute wall clock time might take a measurement every
207 second, batch up 60 of them, and then send the batch to a server. It
208 would include the relative time each measurement was made compared to
209 the time the batch was sent in each SenML Record. The server might
210 have accurate NTP time and use the time it received the data, and the
211 relative offset, to replace the times in the SenML with absolute
212 times before saving the SenML Pack in a document database.
214 3. Terminology
216 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
217 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
218 "OPTIONAL" in this document are to be interpreted as described in
219 [RFC2119].
221 This document also uses the following terms:
223 SenML Record: One measurement or configuration instance in time
224 presented using the SenML data model.
226 SenML Pack: One or more SenML Records in an array structure.
228 SenML Label: A short name used in SenML Records to denote different
229 SenML fields (e.g., "v" for "value").
231 SenML Field: A component of a record that associates a value to a
232 SenML Label for this record.
234 This document uses the terms "attribute" and "tag" where they occur
235 with the underlying technologies (XML, CBOR [RFC7049], and Link
236 Format [RFC6690]), not for SenML concepts per se. Note that
237 "attribute" has been widely used previously as a synonym for SenML
238 "field", though.
240 4. SenML Structure and Semantics
242 Each SenML Pack carries a single array that represents a set of
243 measurements and/or parameters. This array contains a series of
244 SenML Records with several fields described below. There are two
245 kinds of fields: base and regular. The base fields can be included
246 in any SenML Record and they apply to the entries in the Record.
247 Each base field also applies to all Records after it up to, but not
248 including, the next Record that has that same base field. All base
249 fields are optional. Regular fields can be included in any SenML
250 Record and apply only to that Record.
252 4.1. Base Fields
254 Base Name: This is a string that is prepended to the names found in
255 the entries.
257 Base Time: A base time that is added to the time found in an entry.
259 Base Unit: A base unit that is assumed for all entries, unless
260 otherwise indicated. If a record does not contain a Unit value,
261 then the Base Unit is used. Otherwise the value found in the Unit
262 (if any) is used.
264 Base Value: A base value is added to the value found in an entry,
265 similar to Base Time.
267 Base Sum: A base sum is added to the sum found in an entry, similar
268 to Base Time.
270 Version: Version number of media type format. This field is an
271 optional positive integer and defaults to 5 if not present. [RFC
272 Editor: change the default value to 10 when this specification is
273 published as an RFC and remove this note]
275 4.2. Regular Fields
277 Name: Name of the sensor or parameter. When appended to the Base
278 Name field, this must result in a globally unique identifier for
279 the resource. The name is optional, if the Base Name is present.
280 If the name is missing, Base Name must uniquely identify the
281 resource. This can be used to represent a large array of
282 measurements from the same sensor without having to repeat its
283 identifier on every measurement.
285 Unit: Unit for a measurement value. Optional.
287 Value: Value of the entry. Optional if a Sum value is present,
288 otherwise required. Values are represented using basic data
289 types. This specification defines floating point numbers ("v"
290 field for "Value"), booleans ("vb" for "Boolean Value"), strings
291 ("vs" for "String Value") and binary data ("vd" for "Data Value").
292 Exactly one value field MUST appear unless there is Sum field in
293 which case it is allowed to have no Value field.
295 Sum: Integrated sum of the values over time. Optional. This field
296 is in the unit specified in the Unit value multiplied by seconds.
298 Time: Time when value was recorded. Optional.
300 Update Time: Period of time in seconds that represents the maximum
301 time before this sensor will provide an updated reading for a
302 measurement. Optional. This can be used to detect the failure of
303 sensors or communications path from the sensor.
305 4.3. SenML Labels
307 Table 1 provides an overview of all SenML fields defined by this
308 document with their respective labels and data types.
310 +---------------+-------+------------+------------+------------+
311 | Name | Label | CBOR Label | JSON Type | XML Type |
312 +---------------+-------+------------+------------+------------+
313 | Base Name | bn | -2 | String | string |
314 | Base Time | bt | -3 | Number | double |
315 | Base Unit | bu | -4 | String | string |
316 | Base Value | bv | -5 | Number | double |
317 | Base Sum | bs | -6 | Number | double |
318 | Version | bver | -1 | Number | int |
319 | Name | n | 0 | String | string |
320 | Unit | u | 1 | String | string |
321 | Value | v | 2 | Number | double |
322 | String Value | vs | 3 | String | string |
323 | Boolean Value | vb | 4 | Boolean | boolean |
324 | Data Value | vd | 8 | String (*) | string (*) |
325 | Value Sum | s | 5 | Number | double |
326 | Time | t | 6 | Number | double |
327 | Update Time | ut | 7 | Number | double |
328 +---------------+-------+------------+------------+------------+
330 Table 1: SenML Labels
332 Data Value is base64 encoded string with URL safe alphabet as defined
333 in Section 5 of [RFC4648], with padding omitted.
335 For details of the JSON representation see Section 5, for the CBOR
336 Section 6, and for the XML Section 7.
338 4.4. Considerations
340 The SenML format can be extended with further custom fields. Both
341 new base and regular fields are allowed. See Section 12.2 for
342 details. Implementations MUST ignore fields they don't recognize
343 unless that field has a label name that ends with the '_' character
344 in which case an error MUST be generated.
346 All SenML Records in a Pack MUST have the same version number. This
347 is typically done by adding a Base Version field to only the first
348 Record in the Pack.
350 Systems reading one of the objects MUST check for the Version field.
351 If this value is a version number larger than the version which the
352 system understands, the system SHOULD NOT use this object. This
353 allows the version number to indicate that the object contains
354 structure or semantics that is different from what is defined in the
355 present document beyond just making use of the extension points
356 provided here. New version numbers can only be defined in an RFC
357 that updates this specification or it successors.
359 The Name value is concatenated to the Base Name value to yield the
360 name of the sensor. The resulting concatenated name needs to
361 uniquely identify and differentiate the sensor from all others. The
362 concatenated name MUST consist only of characters out of the set "A"
363 to "Z", "a" to "z", "0" to "9", "-", ":", ".", "/", and "_";
364 furthermore, it MUST start with a character out of the set "A" to
365 "Z", "a" to "z", or "0" to "9". This restricted character set was
366 chosen so that concatenated names can be used directly within various
367 URI schemes (including segments of an HTTP path with no special
368 encoding) and can be used directly in many databases and analytic
369 systems. [RFC5952] contains advice on encoding an IPv6 address in a
370 name. See Section 14 for privacy considerations that apply to the
371 use of long-term stable unique identifiers.
373 Although it is RECOMMENDED that concatenated names are represented as
374 URIs [RFC3986] or URNs [RFC8141], the restricted character set
375 specified above puts strict limits on the URI schemes and URN
376 namespaces that can be used. As a result, implementers need to take
377 care in choosing the naming scheme for concatenated names, because
378 such names both need to be unique and need to conform to the
379 restricted character set. One approach is to include a bit string
380 that has guaranteed uniqueness (such as a 1-wire address). Some of
381 the examples within this document use the device URN namespace as
382 specified in [I-D.arkko-core-dev-urn]. UUIDs [RFC4122] are another
383 way to generate a unique name. However, the restricted character set
384 does not allow the use of many URI schemes in names as such. The use
385 of URIs with characters incompatible with this set, and possible
386 mapping rules between the two, are outside of the scope of the
387 present document.
389 If the Record has no Unit, the Base Unit is used as the Unit. Having
390 no Unit and no Base Unit is allowed.
392 If either the Base Time or Time value is missing, the missing field
393 is considered to have a value of zero. The Base Time and Time values
394 are added together to get the time of measurement. A time of zero
395 indicates that the sensor does not know the absolute time and the
396 measurement was made roughly "now". A negative value is used to
397 indicate seconds in the past from roughly "now". A positive value is
398 used to indicate the number of seconds, excluding leap seconds, since
399 the start of the year 1970 in UTC.
401 If only one of the Base Sum or Sum value is present, the missing
402 field is considered to have a value of zero. The Base Sum and Sum
403 values are added together to get the sum of measurement. If neither
404 the Base Sum or Sum are present, then the measurement does not have a
405 sum value.
407 If the Base Value or Value is not present, the missing field(s) are
408 considered to have a value of zero. The Base Value and Value are
409 added together to get the value of the measurement.
411 Representing the statistical characteristics of measurements, such as
412 accuracy, can be very complex. Future specification may add new
413 fields to provide better information about the statistical properties
414 of the measurement.
416 In summary, the structure of a SenML record is laid out to support a
417 single measurement per record. If multiple data values are measured
418 at the same time (e.g., air pressure and altitude), they are best
419 kept as separate records linked through their Time value; this is
420 even true where one of the data values is more "meta" than others
421 (e.g., describes a condition that influences other measurements at
422 the same time).
424 4.5. Resolved Records
426 Sometimes it is useful to be able to refer to a defined normalized
427 format for SenML records. This normalized format tends to get used
428 for big data applications and intermediate forms when converting to
429 other formats.
431 A SenML Record is referred to as "resolved" if it does not contain
432 any base values, i.e., labels starting with the character 'b', except
433 for Version fields (see below), and has no relative times. To
434 resolve the records, the base values of the SenML Pack (if any) are
435 applied to the Record. That is, name and base name are concatenated,
436 base time is added to the time of the Record, if the Record did not
437 contain Unit the Base Unit is applied to the record, etc. In
438 addition the records need to be in chronological order. An example
439 of this is show in Section 5.1.4.
441 The Version field MUST NOT be present in resolved records if the
442 SenML version defined in this document is used and MUST be present
443 otherwise in all the resolved SenML Records.
445 Future specification that defines new base fields need to specify how
446 the field is resolved.
448 4.6. Associating Meta-data
450 SenML is designed to carry the minimum dynamic information about
451 measurements, and for efficiency reasons does not carry significant
452 static meta-data about the device, object or sensors. Instead, it is
453 assumed that this meta-data is carried out of band. For web
454 resources using SenML Packs, this meta-data can be made available
455 using the CoRE Link Format [RFC6690]. The most obvious use of this
456 link format is to describe that a resource is available in a SenML
457 format in the first place. The relevant media type indicator is
458 included in the Content-Type (ct=) link attribute (which is defined
459 for the Link Format in Section 7.2.1 of [RFC7252]).
461 4.7. Configuration and Actuation usage
463 SenML can also be used for configuring parameters and controlling
464 actuators. When a SenML Pack is sent (e.g., using a HTTP/CoAP POST
465 or PUT method) and the semantics of the target are such that SenML is
466 interpreted as configuration/actuation, SenML Records are interpreted
467 as a request to change the values of given (sub)resources (given as
468 names) to given values at the given time(s). The semantics of the
469 target resource supporting this usage can be described, e.g., using
470 [I-D.ietf-core-interfaces]. Examples of actuation usage are shown in
471 Section 5.1.7.
473 5. JSON Representation (application/senml+json)
475 For the SenML fields shown in Table 2, the SenML labels are used as
476 the JSON object member names within JSON objects representing the
477 JSON SenML Records.
479 +---------------+-------+---------+
480 | Name | label | Type |
481 +---------------+-------+---------+
482 | Base Name | bn | String |
483 | Base Time | bt | Number |
484 | Base Unit | bu | String |
485 | Base Value | bv | Number |
486 | Base Sum | bs | Number |
487 | Version | bver | Number |
488 | Name | n | String |
489 | Unit | u | String |
490 | Value | v | Number |
491 | String Value | vs | String |
492 | Boolean Value | vb | Boolean |
493 | Data Value | vd | String |
494 | Value Sum | s | Number |
495 | Time | t | Number |
496 | Update Time | ut | Number |
497 +---------------+-------+---------+
499 Table 2: JSON SenML Labels
501 The root JSON value consists of an array with one JSON object for
502 each SenML Record. All the fields in the above table MAY occur in
503 the records with member values of the type specified in the table.
505 Only the UTF-8 form of JSON is allowed. Characters in the String
506 Value are encoded using the escape sequences defined in [RFC7159].
507 Octets in the Data Value are base64 encoded with URL safe alphabet as
508 defined in Section 5 of [RFC4648], with padding omitted.
510 Systems receiving measurements MUST be able to process the range of
511 floating point numbers that are representable as an IEEE double
512 precision floating point numbers [IEEE.754.1985]. The number of
513 significant digits in any measurement is not relevant, so a reading
514 of 1.1 has exactly the same semantic meaning as 1.10. If the value
515 has an exponent, the "e" MUST be in lower case. The mantissa SHOULD
516 be less than 19 characters long and the exponent SHOULD be less than
517 5 characters long. This allows time values to have better than micro
518 second precision over the next 100 years.
520 5.1. Examples
522 5.1.1. Single Datapoint
524 The following shows a temperature reading taken approximately "now"
525 by a 1-wire sensor device that was assigned the unique 1-wire address
526 of 10e2073a01080063:
528 [
529 {"n":"urn:dev:ow:10e2073a01080063","u":"Cel","v":23.1}
530 ]
532 5.1.2. Multiple Datapoints
534 The following example shows voltage and current now, i.e., at an
535 unspecified time.
537 [
538 {"bn":"urn:dev:ow:10e2073a01080063:","n":"voltage","u":"V","v":120.1},
539 {"n":"current","u":"A","v":1.2}
540 ]
542 The next example is similar to the above one, but shows current at
543 Tue Jun 8 18:01:16.001 UTC 2010 and at each second for the previous 5
544 seconds.
546 [
547 {"bn":"urn:dev:ow:10e2073a0108006:","bt":1.276020076001e+09,
548 "bu":"A","bver":5,
549 "n":"voltage","u":"V","v":120.1},
550 {"n":"current","t":-5,"v":1.2},
551 {"n":"current","t":-4,"v":1.3},
552 {"n":"current","t":-3,"v":1.4},
553 {"n":"current","t":-2,"v":1.5},
554 {"n":"current","t":-1,"v":1.6},
555 {"n":"current","v":1.7}
556 ]
558 Note that in some usage scenarios of SenML the implementations MAY
559 store or transmit SenML in a stream-like fashion, where data is
560 collected over time and continuously added to the object. This mode
561 of operation is optional, but systems or protocols using SenML in
562 this fashion MUST specify that they are doing this. SenML defines a
563 separate media type to indicate Sensor Streaming Measurement Lists
564 (SensML) for this usage (see Section 12.3.2). In this situation the
565 SensML stream can be sent and received in a partial fashion, i.e., a
566 measurement entry can be read as soon as the SenML Record is received
567 and not have to wait for the full SensML Stream to be complete.
569 For instance, the following stream of measurements may be sent via a
570 long lived HTTP POST from the producer of a SensML to the consumer of
571 that, and each measurement object may be reported at the time it was
572 measured:
574 [
575 {"bn":"urn:dev:ow:10e2073a01080063","bt":1.320067464e+09,
576 "bu":"%RH","v":21.2},
577 {"t":10,"v":21.3},
578 {"t":20,"v":21.4},
579 {"t":30,"v":21.4},
580 {"t":40,"v":21.5},
581 {"t":50,"v":21.5},
582 {"t":60,"v":21.5},
583 {"t":70,"v":21.6},
584 {"t":80,"v":21.7},
585 ...
587 5.1.3. Multiple Measurements
589 The following example shows humidity measurements from a mobile
590 device with a 1-wire address 10e2073a01080063, starting at Mon Oct 31
591 13:24:24 UTC 2011. The device also provides position data, which is
592 provided in the same measurement or parameter array as separate
593 entries. Note time is used to for correlating data that belongs
594 together, e.g., a measurement and a parameter associated with it.
595 Finally, the device also reports extra data about its battery status
596 at a separate time.
598 [
599 {"bn":"urn:dev:ow:10e2073a01080063","bt":1.320067464e+09,
600 "bu":"%RH","v":20},
601 {"u":"lon","v":24.30621},
602 {"u":"lat","v":60.07965},
603 {"t":60,"v":20.3},
604 {"u":"lon","t":60,"v":24.30622},
605 {"u":"lat","t":60,"v":60.07965},
606 {"t":120,"v":20.7},
607 {"u":"lon","t":120,"v":24.30623},
608 {"u":"lat","t":120,"v":60.07966},
609 {"u":"%EL","t":150,"v":98},
610 {"t":180,"v":21.2},
611 {"u":"lon","t":180,"v":24.30628},
612 {"u":"lat","t":180,"v":60.07967}
613 ]
615 The size of this example represented in various forms, as well as
616 that form compressed with gzip is given in the following table.
618 +----------+------+-----------------+
619 | Encoding | Size | Compressed Size |
620 +----------+------+-----------------+
621 | JSON | 573 | 206 |
622 | XML | 649 | 235 |
623 | CBOR | 254 | 196 |
624 | EXI | 161 | 184 |
625 +----------+------+-----------------+
627 Table 3: Size Comparisons
629 5.1.4. Resolved Data
631 The following shows the example from the previous section show in
632 resolved format.
634 [
635 {"n":"urn:dev:ow:10e2073a01080063","u":"%RH","t":1.320067464e+09,
636 "v":20},
637 {"n":"urn:dev:ow:10e2073a01080063","u":"lon","t":1.320067464e+09,
638 "v":24.30621},
639 {"n":"urn:dev:ow:10e2073a01080063","u":"lat","t":1.320067464e+09,
640 "v":60.07965},
641 {"n":"urn:dev:ow:10e2073a01080063","u":"%RH","t":1.320067524e+09,
642 "v":20.3},
643 {"n":"urn:dev:ow:10e2073a01080063","u":"lon","t":1.320067524e+09,
644 "v":24.30622},
645 {"n":"urn:dev:ow:10e2073a01080063","u":"lat","t":1.320067524e+09,
646 "v":60.07965},
647 {"n":"urn:dev:ow:10e2073a01080063","u":"%RH","t":1.320067584e+09,
648 "v":20.7},
649 {"n":"urn:dev:ow:10e2073a01080063","u":"lon","t":1.320067584e+09,
650 "v":24.30623},
651 {"n":"urn:dev:ow:10e2073a01080063","u":"lat","t":1.320067584e+09,
652 "v":60.07966},
653 {"n":"urn:dev:ow:10e2073a01080063","u":"%EL","t":1.320067614e+09,
654 "v":98},
655 {"n":"urn:dev:ow:10e2073a01080063","u":"%RH","t":1.320067644e+09,
656 "v":21.2},
657 {"n":"urn:dev:ow:10e2073a01080063","u":"lon","t":1.320067644e+09,
658 "v":24.30628},
659 {"n":"urn:dev:ow:10e2073a01080063","u":"lat","t":1.320067644e+09,
660 "v":60.07967}
661 ]
663 5.1.5. Multiple Data Types
665 The following example shows a sensor that returns different data
666 types.
668 [
669 {"bn":"urn:dev:ow:10e2073a01080063:","n":"temp","u":"Cel","v":23.1},
670 {"n":"label","vs":"Machine Room"},
671 {"n":"open","vb":false},
672 {"n":"nfv-reader","vd":"aGkgCg"}
673 ]
675 5.1.6. Collection of Resources
677 The following example shows the results from a query to one device
678 that aggregates multiple measurements from another devices. The
679 example assumes that a client has fetched information from a device
680 at 2001:db8::2 by performing a GET operation on http://[2001:db8::2]
681 at Mon Oct 31 16:27:09 UTC 2011, and has gotten two separate values
682 as a result, a temperature and humidity measurement as well as the
683 results from another device at http://[2001:db8::1] that also had a
684 temperature and humidity. Note that the last record would use the
685 Base Name from the 3rd record but the Base Time from the first
686 record.
688 [
689 {"bn":"2001:db8::2/","bt":1.320078429e+09,
690 "n":"temperature","u":"Cel","v":25.2},
691 {"n":"humidity","u":"%RH","v":30},
692 {"bn":"2001:db8::1/","n":"temperature","u":"Cel","v":12.3},
693 {"n":"humidity","u":"%RH","v":67}
694 ]
696 5.1.7. Setting an Actuator
698 The following example show the SenML that could be used to set the
699 current set point of a typical residential thermostat which has a
700 temperature set point, a switch to turn on and off the heat, and a
701 switch to turn on the fan override.
703 [
704 {"bn":"urn:dev:ow:10e2073a01080063:"},
705 {"n":"temp","u":"Cel","v":23.1},
706 {"n":"heat","u":"/","v":1},
707 {"n":"fan","u":"/","v":0}
708 ]
709 In the following example two different lights are turned on. It is
710 assumed that the lights are on a network that can guarantee delivery
711 of the messages to the two lights within 15 ms (e.g. a network using
712 802.1BA [IEEE802.1ba-2011] and 802.1AS [IEEE802.1as-2011] for time
713 synchronization). The controller has set the time of the lights
714 coming on to 20 ms in the future from the current time. This allows
715 both lights to receive the message, wait till that time, then apply
716 the switch command so that both lights come on at the same time.
718 [
719 {"bt":1.320078429e+09,"bu":"/","n":"2001:db8::3","v":1},
720 {"n":"2001:db8::4","v":1}
721 ]
723 The following shows two lights being turned off using a non
724 deterministic network that has a high odds of delivering a message in
725 less than 100 ms and uses NTP for time synchronization. The current
726 time is 1320078429. The user has just turned off a light switch
727 which is turning off two lights. Both lights are dimmed to 50%
728 brightness immediately to give the user instant feedback that
729 something is changing. However given the network, the lights will
730 probably dim at somewhat different times. Then 100 ms in the future,
731 both lights will go off at the same time. The instant but not
732 synchronized dimming gives the user the sensation of quick responses
733 and the timed off 100 ms in the future gives the perception of both
734 lights going off at the same time.
736 [
737 {"bt":1.320078429e+09,"bu":"/","n":"2001:db8::3","v":0.5},
738 {"n":"2001:db8::4","v":0.5},
739 {"n":"2001:db8::3","t":0.1,"v":0},
740 {"n":"2001:db8::4","t":0.1,"v":0}
741 ]
743 6. CBOR Representation (application/senml+cbor)
745 The CBOR [RFC7049] representation is equivalent to the JSON
746 representation, with the following changes:
748 o For JSON Numbers, the CBOR representation can use integers,
749 floating point numbers, or decimal fractions (CBOR Tag 4); however
750 a representation SHOULD be chosen such that when the CBOR value is
751 converted back to an IEEE double precision floating point value,
752 it has exactly the same value as the original Number. For the
753 version number, only an unsigned integer is allowed.
755 o Characters in the String Value are encoded using a definite length
756 text string (type 3). Octets in the Data Value are encoded using
757 a definite length byte string (type 2).
759 o For compactness, the CBOR representation uses integers for the
760 labels, as defined in Table 4. This table is conclusive, i.e.,
761 there is no intention to define any additional integer map keys;
762 any extensions will use string map keys. This allows translators
763 converting between CBOR and JSON representations to convert also
764 all future labels without needing to update implementations.
766 +---------------+-------+------------+
767 | Name | Label | CBOR Label |
768 +---------------+-------+------------+
769 | Version | bver | -1 |
770 | Base Name | bn | -2 |
771 | Base Time | bt | -3 |
772 | Base Unit | bu | -4 |
773 | Base Value | bv | -5 |
774 | Base Sum | bs | -6 |
775 | Name | n | 0 |
776 | Unit | u | 1 |
777 | Value | v | 2 |
778 | String Value | vs | 3 |
779 | Boolean Value | vb | 4 |
780 | Value Sum | s | 5 |
781 | Time | t | 6 |
782 | Update Time | ut | 7 |
783 | Data Value | vd | 8 |
784 +---------------+-------+------------+
786 Table 4: CBOR representation: integers for map keys
788 o For streaming SensML in CBOR representation, the array containing
789 the records SHOULD be a CBOR indefinite length array while for
790 non-streaming SenML, a definite length array MUST be used.
792 The following example shows a dump of the CBOR example for the same
793 sensor measurement as in Section 5.1.2.
795 0000 87 a7 21 78 1b 75 72 6e 3a 64 65 76 3a 6f 77 3a |..!x.urn:dev:ow:|
796 0010 31 30 65 32 30 37 33 61 30 31 30 38 30 30 36 3a |10e2073a0108006:|
797 0020 22 fb 41 d3 03 a1 5b 00 10 62 23 61 41 20 05 00 |".A...[..b#aA ..|
798 0030 67 76 6f 6c 74 61 67 65 01 61 56 02 fb 40 5e 06 |gvoltage.aV..@^.|
799 0040 66 66 66 66 66 a3 00 67 63 75 72 72 65 6e 74 06 |fffff..gcurrent.|
800 0050 24 02 fb 3f f3 33 33 33 33 33 33 a3 00 67 63 75 |$..?.333333..gcu|
801 0060 72 72 65 6e 74 06 23 02 fb 3f f4 cc cc cc cc cc |rrent.#..?......|
802 0070 cd a3 00 67 63 75 72 72 65 6e 74 06 22 02 fb 3f |...gcurrent."..?|
803 0080 f6 66 66 66 66 66 66 a3 00 67 63 75 72 72 65 6e |.ffffff..gcurren|
804 0090 74 06 21 02 f9 3e 00 a3 00 67 63 75 72 72 65 6e |t.!..>...gcurren|
805 00a0 74 06 20 02 fb 3f f9 99 99 99 99 99 9a a3 00 67 |t. ..?.........g|
806 00b0 63 75 72 72 65 6e 74 06 00 02 fb 3f fb 33 33 33 |current....?.333|
807 00c0 33 33 33 |333|
808 00c3
810 In CBOR diagnostic notation (Section 6 of [RFC7049]), this is:
812 [{-2: "urn:dev:ow:10e2073a0108006:",
813 -3: 1276020076.001, -4: "A", -1: 5, 0: "voltage", 1: "V", 2: 120.1},
814 {0: "current", 6: -5, 2: 1.2}, {0: "current", 6: -4, 2: 1.3},
815 {0: "current", 6: -3, 2: 1.4}, {0: "current", 6: -2, 2: 1.5},
816 {0: "current", 6: -1, 2: 1.6}, {0: "current", 6: 0, 2: 1.7}]
818 7. XML Representation (application/senml+xml)
820 A SenML Pack or Stream can also be represented in XML format as
821 defined in this section.
823 Only the UTF-8 form of XML is allowed. Characters in the String
824 Value are encoded using the escape sequences defined in [RFC7159].
825 Octets in the Data Value are base64 encoded with URL safe alphabet as
826 defined in Section 5 of [RFC4648].
828 The following example shows an XML example for the same sensor
829 measurement as in Section 5.1.2.
831
832
834
835
836
837
838
839
840
841 The SenML Stream is represented as a sensml element that contains a
842 series of senml elements for each SenML Record. The SenML fields are
843 represented as XML attributes. For each field defined in this
844 document, the following table shows the SenML labels, which are used
845 for the XML attribute name, as well as the according restrictions on
846 the XML attribute values ("type") as used in the XML senml elements.
848 +---------------+-------+---------+
849 | Name | Label | Type |
850 +---------------+-------+---------+
851 | Base Name | bn | string |
852 | Base Time | bt | double |
853 | Base Unit | bu | string |
854 | Base Value | bv | double |
855 | Base Sum | bs | double |
856 | Base Version | bver | int |
857 | Name | n | string |
858 | Unit | u | string |
859 | Value | v | double |
860 | String Value | vs | string |
861 | Data Value | vd | string |
862 | Boolean Value | vb | boolean |
863 | Value Sum | s | double |
864 | Time | t | double |
865 | Update Time | ut | double |
866 +---------------+-------+---------+
868 Table 5: XML SenML Labels
870 The RelaxNG schema for the XML is:
872 default namespace = "urn:ietf:params:xml:ns:senml"
873 namespace rng = "http://relaxng.org/ns/structure/1.0"
875 senml = element senml {
876 attribute bn { xsd:string }?,
877 attribute bt { xsd:double }?,
878 attribute bv { xsd:double }?,
879 attribute bs { xsd:double }?,
880 attribute bu { xsd:string }?,
881 attribute bver { xsd:int }?,
883 attribute n { xsd:string }?,
884 attribute s { xsd:double }?,
885 attribute t { xsd:double }?,
886 attribute u { xsd:string }?,
887 attribute ut { xsd:double }?,
889 attribute v { xsd:double }?,
890 attribute vb { xsd:boolean }?,
891 attribute vs { xsd:string }?,
892 attribute vd { xsd:string }?
893 }
895 sensml =
896 element sensml {
897 senml+
898 }
900 start = sensml
902 8. EXI Representation (application/senml+exi)
904 For efficient transmission of SenML over e.g. a constrained network,
905 Efficient XML Interchange (EXI) can be used. This encodes the XML
906 Schema structure of SenML into binary tags and values rather than
907 ASCII text. An EXI representation of SenML SHOULD be made using the
908 strict schema-mode of EXI. This mode however does not allow tag
909 extensions to the schema, and therefore any extensions will be lost
910 in the encoding. For uses where extensions need to be preserved in
911 EXI, the non-strict schema mode of EXI MAY be used.
913 The EXI header MUST include an "EXI Options", as defined in
914 [W3C.REC-exi-20140211], with an schemaId set to the value of "a"
915 indicating the schema provided in this specification. Future
916 revisions to the schema can change the value of the schemaId to allow
917 for backwards compatibility. When the data will be transported over
918 CoAP or HTTP, an EXI Cookie SHOULD NOT be used as it simply makes
919 things larger and is redundant to information provided in the
920 Content-Type header.
922 The following is the XSD Schema to be used for strict schema guided
923 EXI processing. It is generated from the RelaxNG.
925
926
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
958 The following shows a hexdump of the EXI produced from encoding the
959 following XML example. Note this example is the same information as
960 the first example in Section 5.1.2 in JSON format.
962
963
965
966
967 Which compresses with EXI to the following displayed in hexdump:
969 0000 a0 30 0d 84 80 f3 ab 93 71 d3 23 2b b1 d3 7b b9 |.0......q.#+..{.|
970 0010 d1 89 83 29 91 81 b9 9b 09 81 89 81 c1 81 81 b1 |...)............|
971 0020 99 d2 84 bb 37 b6 3a 30 b3 b2 90 1a b1 58 84 c0 |....7.:0.....X..|
972 0030 33 04 b1 ba b9 39 32 b7 3a 10 1a 09 06 40 38 |3....92.:....@8|
973 003f
975 The above example used the bit packed form of EXI but it is also
976 possible to use a byte packed form of EXI which can makes it easier
977 for a simple sensor to produce valid EXI without really implementing
978 EXI. Consider the example of a temperature sensor that produces a
979 value in tenths of degrees Celsius over a range of 0.0 to 55.0. It
980 would produce an XML SenML file such as:
982
983
984
986 The compressed form, using the byte alignment option of EXI, for the
987 above XML is the following:
989 0000 a0 00 48 80 6c 20 01 06 1d 75 72 6e 3a 64 65 76 |..H.l ...urn:dev|
990 0010 3a 6f 77 3a 31 30 65 32 30 37 33 61 30 31 30 38 |:ow:10e2073a0108|
991 0020 30 30 36 33 02 05 43 65 6c 01 00 e7 01 01 00 03 |0063..Cel.......|
992 0030 01 |.|
993 0031
995 A small temperature sensor device that only generates this one EXI
996 file does not really need an full EXI implementation. It can simply
997 hard code the output replacing the 1-wire device ID starting at byte
998 0x20 and going to byte 0x2F with it's device ID, and replacing the
999 value "0xe7 0x01" at location 0x37 and 0x38 with the current
1000 temperature. The EXI Specification [W3C.REC-exi-20140211] contains
1001 the full information on how floating point numbers are represented,
1002 but for the purpose of this sensor, the temperature can be converted
1003 to an integer in tenths of degrees (231 in this example). EXI stores
1004 7 bits of the integer in each byte with the top bit set to one if
1005 there are further bytes. So the first bytes at is set to low 7 bits
1006 of the integer temperature in tenths of degrees plus 0x80. In this
1007 example 231 & 0x7F + 0x80 = 0xE7. The second byte is set to the
1008 integer temperature in tenths of degrees right shifted 7 bits. In
1009 this example 231 >> 7 = 0x01.
1011 9. Fragment Identification Methods
1013 A SenML Pack typically consists of multiple SenML Records and for
1014 some applications it may be useful to be able to refer with a
1015 Fragment Identifier to a single record, or a set of records, in a
1016 Pack. The fragment identifier is only interpreted by a client and
1017 does not impact retrieval of a representation. The SenML Fragment
1018 Identification is modeled after CSV Fragment Identifiers [RFC7111].
1020 To select a single SenML Record, the "rec" scheme followed by a
1021 single number is used. For the purpose of numbering records, the
1022 first record is at position 1. A range of records can be selected by
1023 giving the first and the last record number separated by a '-'
1024 character. Instead of the second number, the '*' character can be
1025 used to indicate the last SenML Record in the Pack. A set of records
1026 can also be selected using a comma separated list of record positions
1027 or ranges.
1029 (We use the term "selecting a record" for identifying it as part of
1030 the fragment, not in the sense of isolating it from the Pack -- the
1031 record still needs to be interpreted as part of the Pack, e.g., using
1032 the base values defined in earlier records)
1034 9.1. Fragment Identification Examples
1036 The 3rd SenML Record from "coap://example.com/temp" resource can be
1037 selected with:
1039 coap://example.com/temp#rec=3
1041 Records from 3rd to 6th can be selected with:
1043 coap://example.com/temp#rec=3-6
1045 Records from 19th to the last can be selected with:
1047 coap://example.com/temp#rec=19-*
1049 The 3rd and 5th record can be selected with:
1051 coap://example.com/temp#rec=3,5
1053 To select the Records from third to fifth, the 10th record, and all
1054 from 19th to the last:
1056 coap://example.com/temp#rec=3-5,10,19-*
1058 10. Usage Considerations
1060 The measurements support sending both the current value of a sensor
1061 as well as the an integrated sum. For many types of measurements,
1062 the sum is more useful than the current value. For example, an
1063 electrical meter that measures the energy a given computer uses will
1064 typically want to measure the cumulative amount of energy used. This
1065 is less prone to error than reporting the power each second and
1066 trying to have something on the server side sum together all the
1067 power measurements. If the network between the sensor and the meter
1068 goes down over some period of time, when it comes back up, the
1069 cumulative sum helps reflect what happened while the network was
1070 down. A meter like this would typically report a measurement with
1071 the unit set to watts, but it would put the sum of energy used in the
1072 "s" field of the measurement. It might optionally include the
1073 current power in the "v" field.
1075 While the benefit of using the integrated sum is fairly clear for
1076 measurements like power and energy, it is less obvious for something
1077 like temperature. Reporting the sum of the temperature makes it easy
1078 to compute averages even when the individual temperature values are
1079 not reported frequently enough to compute accurate averages.
1080 Implementers are encouraged to report the cumulative sum as well as
1081 the raw value of a given sensor.
1083 Applications that use the cumulative sum values need to understand
1084 they are very loosely defined by this specification, and depending on
1085 the particular sensor implementation may behave in unexpected ways.
1086 Applications should be able to deal with the following issues:
1088 1. Many sensors will allow the cumulative sums to "wrap" back to
1089 zero after the value gets sufficiently large.
1091 2. Some sensors will reset the cumulative sum back to zero when the
1092 device is reset, loses power, or is replaced with a different
1093 sensor.
1095 3. Applications cannot make assumptions about when the device
1096 started accumulating values into the sum.
1098 Typically applications can make some assumptions about specific
1099 sensors that will allow them to deal with these problems. A common
1100 assumption is that for sensors whose measurement values are always
1101 positive, the sum should never get smaller; so if the sum does get
1102 smaller, the application will know that one of the situations listed
1103 above has happened.
1105 11. CDDL
1107 For reference, the JSON and CBOR representations can be described
1108 with the common CDDL [I-D.ietf-cbor-cddl] specification in Figure 1.
1110 SenML-Pack = [1* record]
1112 record = {
1113 ? bn => tstr, ; Base Name
1114 ? bt => numeric, ; Base Time
1115 ? bu => tstr, ; Base Units
1116 ? bv => numeric, ; Base Value
1117 ? bs => numeric, ; Base Sum
1118 ? bver => uint, ; Base Version
1119 ? n => tstr, ; Name
1120 ? u => tstr, ; Units
1121 ? s => numeric, ; Value Sum
1122 ? t => numeric, ; Time
1123 ? ut => numeric, ; Update Time
1124 ? ( v => numeric // ; Numeric Value
1125 vs => tstr // ; String Value
1126 vb => bool // ; Boolean Value
1127 vd => binary-value ) ; Data Value
1128 * key-value-pair
1129 }
1131 ; now define the generic versions
1132 key-value-pair = ( label => value )
1134 label = non-b-label / b-label
1135 non-b-label = tstr .regexp "[A-Zac-z0-9][-_:.A-Za-z0-9]*" / uint
1136 b-label = tstr .regexp "b[-_:.A-Za-z0-9]+" / nint
1138 value = tstr / binary-value / numeric / bool
1139 numeric = number / decfrac
1141 Figure 1: Common CDDL specification for CBOR and JSON SenML
1143 For JSON, we use text labels and base64url-encoded binary data
1144 (Figure 2).
1146 bver = "bver" n = "n" s = "s"
1147 bn = "bn" u = "u" t = "t"
1148 bt = "bt" v = "v" ut = "ut"
1149 bu = "bu" vs = "vs" vd = "vd"
1150 bv = "bv" vb = "vb"
1151 bs = "bs"
1153 binary-value = tstr ; base64url encoded
1155 Figure 2: JSON-specific CDDL specification for SenML
1157 For CBOR, we use integer labels and native binary data (Figure 3).
1159 bver = -1 n = 0 s = 5
1160 bn = -2 u = 1 t = 6
1161 bt = -3 v = 2 ut = 7
1162 bu = -4 vs = 3 vd = 8
1163 bv = -5 vb = 4
1164 bs = -6
1166 binary-value = bstr
1168 Figure 3: CBOR-specific CDDL specification for SenML
1170 12. IANA Considerations
1172 Note to RFC Editor: Please replace all occurrences of "RFC-AAAA" with
1173 the RFC number of this specification.
1175 12.1. Units Registry
1177 IANA will create a registry of SenML unit symbols. The primary
1178 purpose of this registry is to make sure that symbols uniquely map to
1179 give type of measurement. Definitions for many of these units can be
1180 found in location such as [NIST811] and [BIPM]. Units marked with an
1181 asterisk are NOT RECOMMENDED to be produced by new implementations,
1182 but are in active use and SHOULD be implemented by consumers that can
1183 use the related base units.
1185 +----------+------------------------------------+-------+-----------+
1186 | Symbol | Description | Type | Reference |
1187 +----------+------------------------------------+-------+-----------+
1188 | m | meter | float | RFC-AAAA |
1189 | kg | kilogram | float | RFC-AAAA |
1190 | g | gram* | float | RFC-AAAA |
1191 | s | second | float | RFC-AAAA |
1192 | A | ampere | float | RFC-AAAA |
1193 | K | kelvin | float | RFC-AAAA |
1194 | cd | candela | float | RFC-AAAA |
1195 | mol | mole | float | RFC-AAAA |
1196 | Hz | hertz | float | RFC-AAAA |
1197 | rad | radian | float | RFC-AAAA |
1198 | sr | steradian | float | RFC-AAAA |
1199 | N | newton | float | RFC-AAAA |
1200 | Pa | pascal | float | RFC-AAAA |
1201 | J | joule | float | RFC-AAAA |
1202 | W | watt | float | RFC-AAAA |
1203 | C | coulomb | float | RFC-AAAA |
1204 | V | volt | float | RFC-AAAA |
1205 | F | farad | float | RFC-AAAA |
1206 | Ohm | ohm | float | RFC-AAAA |
1207 | S | siemens | float | RFC-AAAA |
1208 | Wb | weber | float | RFC-AAAA |
1209 | T | tesla | float | RFC-AAAA |
1210 | H | henry | float | RFC-AAAA |
1211 | Cel | degrees Celsius | float | RFC-AAAA |
1212 | lm | lumen | float | RFC-AAAA |
1213 | lx | lux | float | RFC-AAAA |
1214 | Bq | becquerel | float | RFC-AAAA |
1215 | Gy | gray | float | RFC-AAAA |
1216 | Sv | sievert | float | RFC-AAAA |
1217 | kat | katal | float | RFC-AAAA |
1218 | m2 | square meter (area) | float | RFC-AAAA |
1219 | m3 | cubic meter (volume) | float | RFC-AAAA |
1220 | l | liter (volume)* | float | RFC-AAAA |
1221 | m/s | meter per second (velocity) | float | RFC-AAAA |
1222 | m/s2 | meter per square second | float | RFC-AAAA |
1223 | | (acceleration) | | |
1224 | m3/s | cubic meter per second (flow rate) | float | RFC-AAAA |
1225 | l/s | liter per second (flow rate)* | float | RFC-AAAA |
1226 | W/m2 | watt per square meter (irradiance) | float | RFC-AAAA |
1227 | cd/m2 | candela per square meter | float | RFC-AAAA |
1228 | | (luminance) | | |
1229 | bit | bit (information content) | float | RFC-AAAA |
1230 | bit/s | bit per second (data rate) | float | RFC-AAAA |
1231 | lat | degrees latitude (note 1) | float | RFC-AAAA |
1232 | lon | degrees longitude (note 1) | float | RFC-AAAA |
1233 | pH | pH value (acidity; logarithmic | float | RFC-AAAA |
1234 | | quantity) | | |
1235 | dB | decibel (logarithmic quantity) | float | RFC-AAAA |
1236 | dBW | decibel relative to 1 W (power | float | RFC-AAAA |
1237 | | level) | | |
1238 | Bspl | bel (sound pressure level; | float | RFC-AAAA |
1239 | | logarithmic quantity)* | | |
1240 | count | 1 (counter value) | float | RFC-AAAA |
1241 | / | 1 (Ratio e.g., value of a switch, | float | RFC-AAAA |
1242 | | note 2) | | |
1243 | % | 1 (Ratio e.g., value of a switch, | float | RFC-AAAA |
1244 | | note 2)* | | |
1245 | %RH | Percentage (Relative Humidity) | float | RFC-AAAA |
1246 | %EL | Percentage (remaining battery | float | RFC-AAAA |
1247 | | energy level) | | |
1248 | EL | seconds (remaining battery energy | float | RFC-AAAA |
1249 | | level) | | |
1250 | 1/s | 1 per second (event rate) | float | RFC-AAAA |
1251 | 1/min | 1 per minute (event rate, "rpm")* | float | RFC-AAAA |
1252 | beat/min | 1 per minute (Heart rate in beats | float | RFC-AAAA |
1253 | | per minute)* | | |
1254 | beats | 1 (Cumulative number of heart | float | RFC-AAAA |
1255 | | beats)* | | |
1256 | S/m | Siemens per meter (conductivity) | float | RFC-AAAA |
1257 +----------+------------------------------------+-------+-----------+
1259 Table 6
1261 o Note 1: Assumed to be in WGS84 unless another reference frame is
1262 known for the sensor.
1264 o Note 2: A value of 0.0 indicates the switch is off while 1.0
1265 indicates on and 0.5 would be half on. The preferred name of this
1266 unit is "/". For historical reasons, the name "%" is also
1267 provided for the same unit - but note that while that name
1268 strongly suggests a percentage (0..100) -- it is however NOT a
1269 percentage, but the absolute ratio!
1271 New entries can be added to the registration by Expert Review as
1272 defined in [RFC8126]. Experts should exercise their own good
1273 judgment but need to consider the following guidelines:
1275 1. There needs to be a real and compelling use for any new unit to
1276 be added.
1278 2. Each unit should define the semantic information and be chosen
1279 carefully. Implementers need to remember that the same word may
1280 be used in different real-life contexts. For example, degrees
1281 when measuring latitude have no semantic relation to degrees
1282 when measuring temperature; thus two different units are needed.
1284 3. These measurements are produced by computers for consumption by
1285 computers. The principle is that conversion has to be easily be
1286 done when both reading and writing the media type. The value of
1287 a single canonical representation outweighs the convenience of
1288 easy human representations or loss of precision in a conversion.
1290 4. Use of SI prefixes such as "k" before the unit is not
1291 recommended. Instead one can represent the value using
1292 scientific notation such a 1.2e3. The "kg" unit is exception to
1293 this rule since it is an SI base unit; the "g" unit is provided
1294 for legacy compatibility.
1296 5. For a given type of measurement, there will only be one unit
1297 type defined. So for length, meters are defined and other
1298 lengths such as mile, foot, light year are not allowed. For
1299 most cases, the SI unit is preferred.
1301 (Note that some amount of judgment will be required here, as
1302 even SI itself is not entirely consistent in this respect. For
1303 instance, for temperature [ISO-80000-5] defines a quantity, item
1304 5-1 (thermodynamic temperature), and a corresponding unit 5-1.a
1305 (Kelvin), and then goes ahead to define another quantity right
1306 besides that, item 5-2 ("Celsius temperature"), and the
1307 corresponding unit 5-2.a (degree Celsius). The latter quantity
1308 is defined such that it gives the thermodynamic temperature as a
1309 delta from T0 = 275.15 K. ISO 80000-5 is defining both units
1310 side by side, and not really expressing a preference. This
1311 level of recognition of the alternative unit degree Celsius is
1312 the reason why Celsius temperatures exceptionally seem
1313 acceptable in the SenML units list alongside Kelvin.)
1315 6. Symbol names that could be easily confused with existing common
1316 units or units combined with prefixes should be avoided. For
1317 example, selecting a unit name of "mph" to indicate something
1318 that had nothing to do with velocity would be a bad choice, as
1319 "mph" is commonly used to mean miles per hour.
1321 7. The following should not be used because the are common SI
1322 prefixes: Y, Z, E, P, T, G, M, k, h, da, d, c, n, u, p, f, a, z,
1323 y, Ki, Mi, Gi, Ti, Pi, Ei, Zi, Yi.
1325 8. The following units should not be used as they are commonly used
1326 to represent other measurements Ky, Gal, dyn, etg, P, St, Mx, G,
1327 Oe, Gb, sb, Lmb, mph, Ci, R, RAD, REM, gal, bbl, qt, degF, Cal,
1328 BTU, HP, pH, B/s, psi, Torr, atm, at, bar, kWh.
1330 9. The unit names are case sensitive and the correct case needs to
1331 be used, but symbols that differ only in case should not be
1332 allocated.
1334 10. A number after a unit typically indicates the previous unit
1335 raised to that power, and the / indicates that the units that
1336 follow are the reciprocal. A unit should have only one / in the
1337 name.
1339 11. A good list of common units can be found in the Unified Code for
1340 Units of Measure [UCUM].
1342 12.2. SenML Label Registry
1344 IANA will create a new registry for SenML labels. The initial
1345 content of the registry is:
1347 +--------------+-------+----+-----------+----------+----+-----------+
1348 | Name | Label | CL | JSON Type | XML Type | EI | Reference |
1349 +--------------+-------+----+-----------+----------+----+-----------+
1350 | Base Name | bn | -2 | String | string | a | RFCXXXX |
1351 | Base Time | bt | -3 | Number | double | a | RFCXXXX |
1352 | Base Unit | bu | -4 | String | string | a | RFCXXXX |
1353 | Base Value | bv | -5 | Number | double | a | RFCXXXX |
1354 | Base Sum | bs | -6 | Number | double | a | RFCXXXX |
1355 | Base Version | bver | -1 | Number | int | a | RFCXXXX |
1356 | Name | n | 0 | String | string | a | RFCXXXX |
1357 | Unit | u | 1 | String | string | a | RFCXXXX |
1358 | Value | v | 2 | Number | double | a | RFCXXXX |
1359 | String Value | vs | 3 | String | string | a | RFCXXXX |
1360 | Boolean | vb | 4 | Boolean | boolean | a | RFCXXXX |
1361 | Value | | | | | | |
1362 | Data Value | vd | 8 | String | string | a | RFCXXXX |
1363 | Value Sum | s | 5 | Number | double | a | RFCXXXX |
1364 | Time | t | 6 | Number | double | a | RFCXXXX |
1365 | Update Time | ut | 7 | Number | double | a | RFCXXXX |
1366 +--------------+-------+----+-----------+----------+----+-----------+
1368 Table 7: IANA Registry for SenML Labels, CL = CBOR Label, EI = EXI ID
1370 This is the same table as Table 1, with notes removed, and with
1371 columns added for the information that is all the same for this
1372 initial set of registrations, but will need to be supplied with a
1373 different value for new registrations.
1375 Note to RFC Editor. Please replace RFCXXXX with the number for this
1376 RFC.
1378 All new entries must define the Label Name, Label, and XML Type but
1379 the CBOR labels SHOULD be left empty as CBOR will use the string
1380 encoding for any new labels. The EI column contains the EXI schemaId
1381 value of the first Schema which includes this label or is empty if
1382 this label was not intended for use with EXI. The Note field SHOULD
1383 contain information about where to find out more information about
1384 this label.
1386 The JSON, CBOR, and EXI types are derived from the XML type. All XML
1387 numeric types such as double, float, integer and int become a JSON
1388 Number. XML boolean and string become a JSON Boolean and String
1389 respectively. CBOR represents numeric values with a CBOR type that
1390 does not lose any information from the JSON value. EXI uses the XML
1391 types.
1393 New entries can be added to the registration by Expert Review as
1394 defined in [RFC8126]. Experts should exercise their own good
1395 judgment but need to consider that shorter labels should have more
1396 strict review. New entries should not be made that counteract the
1397 advice at the end of Section 4.4.
1399 All new SenML labels that have "base" semantics (see Section 4.1)
1400 MUST start with the character 'b'. Regular labels MUST NOT start
1401 with that character.
1403 Extensions that add a label that is intended for use with XML need to
1404 create a new RelaxNG scheme that includes all the labels in the IANA
1405 registry.
1407 Extensions that add a label that is intended for use with EXI need to
1408 create a new XSD Schema that includes all the labels in the IANA
1409 registry and then allocate a new EXI schemaId value. Moving to the
1410 next letter in the alphabet is the suggested way to create the new
1411 value for the EXI schemaId. Any labels with previously blank ID
1412 values SHOULD be updated in the IANA table to have their ID set to
1413 this new schemaId value.
1415 Extensions that are mandatory to understand to correctly process the
1416 Pack MUST have a label name that ends with the '_' character.
1418 12.3. Media Type Registration
1420 The following registrations are done following the procedure
1421 specified in [RFC6838] and [RFC7303]. Clipboard formats are defined
1422 for the JSON and XML form of lists but do not make sense for streams
1423 or other formats.
1425 Note to RFC Editor - please remove this paragraph. Note that a
1426 request for media type review for senml+json was sent to the media-
1427 types@iana.org on Sept 21, 2010. A second request for all the types
1428 was sent on October 31, 2016. Please change all instances of RFC-
1429 AAAA with the RFC number of this document.
1431 12.3.1. senml+json Media Type Registration
1433 Type name: application
1435 Subtype name: senml+json
1437 Required parameters: none
1439 Optional parameters: none
1441 Encoding considerations: Must be encoded as using a subset of the
1442 encoding allowed in [RFC7159]. See RFC-AAAA for details. This
1443 simplifies implementation of very simple system and does not impose
1444 any significant limitations as all this data is meant for machine to
1445 machine communications and is not meant to be human readable.
1447 Security considerations: See Section 13 of RFC-AAAA.
1449 Interoperability considerations: Applications should ignore any JSON
1450 key value pairs that they do not understand. This allows backwards
1451 compatibility extensions to this specification. The "bver" field can
1452 be used to ensure the receiver supports a minimal level of
1453 functionality needed by the creator of the JSON object.
1455 Published specification: RFC-AAAA
1457 Applications that use this media type: The type is used by systems
1458 that report e.g., electrical power usage and environmental
1459 information such as temperature and humidity. It can be used for a
1460 wide range of sensor reporting systems.
1462 Fragment identifier considerations: Fragment identification for
1463 application/senml+json is supported by using fragment identifiers as
1464 specified by RFC-AAAA.
1466 Additional information:
1468 Magic number(s): none
1470 File extension(s): senml
1472 Windows Clipboard Name: "JSON Sensor Measurement List"
1474 Macintosh file type code(s): none
1476 Macintosh Universal Type Identifier code: org.ietf.senml-json
1477 conforms to public.text
1478 Person & email address to contact for further information: Cullen
1479 Jennings
1481 Intended usage: COMMON
1483 Restrictions on usage: None
1485 Author: Cullen Jennings
1487 Change controller: IESG
1489 12.3.2. sensml+json Media Type Registration
1491 Type name: application
1493 Subtype name: sensml+json
1495 Required parameters: none
1497 Optional parameters: none
1499 Encoding considerations: Must be encoded as using a subset of the
1500 encoding allowed in [RFC7159]. See RFC-AAAA for details. This
1501 simplifies implementation of very simple system and does not impose
1502 any significant limitations as all this data is meant for machine to
1503 machine communications and is not meant to be human readable.
1505 Security considerations: See Section 13 of RFC-AAAA.
1507 Interoperability considerations: Applications should ignore any JSON
1508 key value pairs that they do not understand. This allows backwards
1509 compatibility extensions to this specification. The "bver" field can
1510 be used to ensure the receiver supports a minimal level of
1511 functionality needed by the creator of the JSON object.
1513 Published specification: RFC-AAAA
1515 Applications that use this media type: The type is used by systems
1516 that report e.g., electrical power usage and environmental
1517 information such as temperature and humidity. It can be used for a
1518 wide range of sensor reporting systems.
1520 Fragment identifier considerations: Fragment identification for
1521 application/senml+json is supported by using fragment identifiers as
1522 specified by RFC-AAAA.
1524 Additional information:
1526 Magic number(s): none
1528 File extension(s): sensml
1530 Macintosh file type code(s): none
1532 Person & email address to contact for further information: Cullen
1533 Jennings
1535 Intended usage: COMMON
1537 Restrictions on usage: None
1539 Author: Cullen Jennings
1541 Change controller: IESG
1543 12.3.3. senml+cbor Media Type Registration
1545 Type name: application
1547 Subtype name: senml+cbor
1549 Required parameters: none
1551 Optional parameters: none
1553 Encoding considerations: Must be encoded as using [RFC7049]. See
1554 RFC-AAAA for details.
1556 Security considerations: See Section 13 of RFC-AAAA.
1558 Interoperability considerations: Applications should ignore any key
1559 value pairs that they do not understand. This allows backwards
1560 compatibility extensions to this specification. The "bver" field can
1561 be used to ensure the receiver supports a minimal level of
1562 functionality needed by the creator of the CBOR object.
1564 Published specification: RFC-AAAA
1566 Applications that use this media type: The type is used by systems
1567 that report e.g., electrical power usage and environmental
1568 information such as temperature and humidity. It can be used for a
1569 wide range of sensor reporting systems.
1571 Fragment identifier considerations: Fragment identification for
1572 application/senml+cbor is supported by using fragment identifiers as
1573 specified by RFC-AAAA.
1575 Additional information:
1577 Magic number(s): none
1579 File extension(s): senmlc
1581 Macintosh file type code(s): none
1583 Macintosh Universal Type Identifier code: org.ietf.senml-cbor
1584 conforms to public.data
1586 Person & email address to contact for further information: Cullen
1587 Jennings
1589 Intended usage: COMMON
1591 Restrictions on usage: None
1593 Author: Cullen Jennings
1595 Change controller: IESG
1597 12.3.4. sensml+cbor Media Type Registration
1599 Type name: application
1601 Subtype name: sensml+cbor
1603 Required parameters: none
1605 Optional parameters: none
1607 Encoding considerations: Must be encoded as using [RFC7049]. See
1608 RFC-AAAA for details.
1610 Security considerations: See Section 13 of RFC-AAAA.
1612 Interoperability considerations: Applications should ignore any key
1613 value pairs that they do not understand. This allows backwards
1614 compatibility extensions to this specification. The "bver" field can
1615 be used to ensure the receiver supports a minimal level of
1616 functionality needed by the creator of the CBOR object.
1618 Published specification: RFC-AAAA
1620 Applications that use this media type: The type is used by systems
1621 that report e.g., electrical power usage and environmental
1622 information such as temperature and humidity. It can be used for a
1623 wide range of sensor reporting systems.
1625 Fragment identifier considerations: Fragment identification for
1626 application/senml+cbor is supported by using fragment identifiers as
1627 specified by RFC-AAAA.
1629 Additional information:
1631 Magic number(s): none
1633 File extension(s): sensmlc
1635 Macintosh file type code(s): none
1637 Person & email address to contact for further information: Cullen
1638 Jennings
1640 Intended usage: COMMON
1642 Restrictions on usage: None
1644 Author: Cullen Jennings
1646 Change controller: IESG
1648 12.3.5. senml+xml Media Type Registration
1650 Type name: application
1652 Subtype name: senml+xml
1654 Required parameters: none
1656 Optional parameters: none
1658 Encoding considerations: Must be encoded as using
1659 [W3C.REC-xml-20081126]. See RFC-AAAA for details.
1661 Security considerations: See Section 13 of RFC-AAAA.
1663 Interoperability considerations: Applications should ignore any XML
1664 tags or attributes that they do not understand. This allows
1665 backwards compatibility extensions to this specification. The "bver"
1666 attribute in the senml XML tag can be used to ensure the receiver
1667 supports a minimal level of functionality needed by the creator of
1668 the XML.
1670 Published specification: RFC-AAAA
1672 Applications that use this media type: The type is used by systems
1673 that report e.g., electrical power usage and environmental
1674 information such as temperature and humidity. It can be used for a
1675 wide range of sensor reporting systems.
1677 Fragment identifier considerations: Fragment identification for
1678 application/senml+xml is supported by using fragment identifiers as
1679 specified by RFC-AAAA.
1681 Additional information:
1683 Magic number(s): none
1685 File extension(s): senmlx
1687 Windows Clipboard Name: "XML Sensor Measurement List"
1689 Macintosh file type code(s): none
1691 Macintosh Universal Type Identifier code: org.ietf.senml-xml conforms
1692 to public.xml
1694 Person & email address to contact for further information: Cullen
1695 Jennings
1697 Intended usage: COMMON
1699 Restrictions on usage: None
1701 Author: Cullen Jennings
1703 Change controller: IESG
1705 12.3.6. sensml+xml Media Type Registration
1707 Type name: application
1709 Subtype name: sensml+xml
1711 Required parameters: none
1713 Optional parameters: none
1715 Encoding considerations: Must be encoded as using
1716 [W3C.REC-xml-20081126]. See RFC-AAAA for details.
1718 Security considerations: See Section 13 of RFC-AAAA.
1720 Interoperability considerations: Applications should ignore any XML
1721 tags or attributes that they do not understand. This allows
1722 backwards compatibility extensions to this specification. The "bver"
1723 attribute in the senml XML tag can be used to ensure the receiver
1724 supports a minimal level of functionality needed by the creator of
1725 the XML.
1727 Published specification: RFC-AAAA
1729 Applications that use this media type: The type is used by systems
1730 that report e.g., electrical power usage and environmental
1731 information such as temperature and humidity. It can be used for a
1732 wide range of sensor reporting systems.
1734 Fragment identifier considerations: Fragment identification for
1735 application/senml+xml is supported by using fragment identifiers as
1736 specified by RFC-AAAA.
1738 Additional information:
1740 Magic number(s): none
1742 File extension(s): sensmlx
1744 Macintosh file type code(s): none
1746 Person & email address to contact for further information: Cullen
1747 Jennings
1749 Intended usage: COMMON
1751 Restrictions on usage: None
1753 Author: Cullen Jennings
1755 Change controller: IESG
1757 12.3.7. senml+exi Media Type Registration
1759 Type name: application
1761 Subtype name: senml+exi
1763 Required parameters: none
1765 Optional parameters: none
1766 Encoding considerations: Must be encoded as using
1767 [W3C.REC-exi-20140211]. See RFC-AAAA for details.
1769 Security considerations: See Section 13 of RFC-AAAA.
1771 Interoperability considerations: Applications should ignore any XML
1772 tags or attributes that they do not understand. This allows
1773 backwards compatibility extensions to this specification. The "bver"
1774 attribute in the senml XML tag can be used to ensure the receiver
1775 supports a minimal level of functionality needed by the creator of
1776 the XML. Further information on using schemas to guide the EXI can
1777 be found in RFC-AAAA.
1779 Published specification: RFC-AAAA
1781 Applications that use this media type: The type is used by systems
1782 that report e.g., electrical power usage and environmental
1783 information such as temperature and humidity. It can be used for a
1784 wide range of sensor reporting systems.
1786 Fragment identifier considerations: Fragment identification for
1787 application/senml+exi is supported by using fragment identifiers as
1788 specified by RFC-AAAA.
1790 Additional information:
1792 Magic number(s): none
1794 File extension(s): senmle
1796 Macintosh file type code(s): none
1798 Macintosh Universal Type Identifier code: org.ietf.senml-exi conforms
1799 to public.data
1801 Person & email address to contact for further information: Cullen
1802 Jennings
1804 Intended usage: COMMON
1806 Restrictions on usage: None
1808 Author: Cullen Jennings
1810 Change controller: IESG
1812 12.3.8. sensml+exi Media Type Registration
1814 Type name: application
1816 Subtype name: sensml+exi
1818 Required parameters: none
1820 Optional parameters: none
1822 Encoding considerations: Must be encoded as using
1823 [W3C.REC-exi-20140211]. See RFC-AAAA for details.
1825 Security considerations: See Section 13 of RFC-AAAA.
1827 Interoperability considerations: Applications should ignore any XML
1828 tags or attributes that they do not understand. This allows
1829 backwards compatibility extensions to this specification. The "bver"
1830 attribute in the senml XML tag can be used to ensure the receiver
1831 supports a minimal level of functionality needed by the creator of
1832 the XML. Further information on using schemas to guide the EXI can
1833 be found in RFC-AAAA.
1835 Published specification: RFC-AAAA
1837 Applications that use this media type: The type is used by systems
1838 that report e.g., electrical power usage and environmental
1839 information such as temperature and humidity. It can be used for a
1840 wide range of sensor reporting systems.
1842 Fragment identifier considerations: Fragment identification for
1843 application/senml+exi is supported by using fragment identifiers as
1844 specified by RFC-AAAA.
1846 Additional information:
1848 Magic number(s): none
1850 File extension(s): sensmle
1852 Macintosh file type code(s): none
1854 Person & email address to contact for further information: Cullen
1855 Jennings
1857 Intended usage: COMMON
1859 Restrictions on usage: None
1860 Author: Cullen Jennings
1862 Change controller: IESG
1864 12.4. XML Namespace Registration
1866 This document registers the following XML namespaces in the IETF XML
1867 registry defined in [RFC3688].
1869 URI: urn:ietf:params:xml:ns:senml
1871 Registrant Contact: The IESG.
1873 XML: N/A, the requested URIs are XML namespaces
1875 12.5. CoAP Content-Format Registration
1877 IANA is requested to assign CoAP Content-Format IDs for the SenML
1878 media types in the "CoAP Content-Formats" sub-registry, within the
1879 "CoRE Parameters" registry [RFC7252]. All IDs are assigned from the
1880 "Expert Review" (0-255) range. The assigned IDs are show in Table 8.
1882 +-------------------------+-----+
1883 | Media type | ID |
1884 +-------------------------+-----+
1885 | application/senml+json | TBD |
1886 | application/sensml+json | TBD |
1887 | application/senml+cbor | TBD |
1888 | application/sensml+cbor | TBD |
1889 | application/senml+xml | TBD |
1890 | application/sensml+xml | TBD |
1891 | application/senml+exi | TBD |
1892 | application/sensml+exi | TBD |
1893 +-------------------------+-----+
1895 Table 8: CoAP Content-Format IDs
1897 13. Security Considerations
1899 Sensor data can contain a wide range of information ranging from
1900 information that is very public, such as the outside temperature in a
1901 given city, to very private information that requires integrity and
1902 confidentiality protection, such as patient health information. The
1903 SenML format does not provide any security and instead relies on the
1904 protocol that carries it to provide security. Applications using
1905 SenML need to look at the overall context of how this media type will
1906 be used to decide if the security is adequate.
1908 See also Section 14.
1910 14. Privacy Considerations
1912 Sensor data can range from information with almost no security
1913 considerations, such as the current temperature in a given city, to
1914 highly sensitive medical or location data. This specification
1915 provides no security protection for the data but is meant to be used
1916 inside another container or transport protocol such as S/MIME or HTTP
1917 with TLS that can provide integrity, confidentiality, and
1918 authentication information about the source of the data.
1920 The name fields need to uniquely identify the sources or destinations
1921 of the values in a SenML Pack. However, the use of long-term stable
1922 unique identifiers can be problematic for privacy reasons [RFC6973],
1923 depending on the application and the potential of these identifiers
1924 to be used in correlation with other information. They should be
1925 used with care or avoided as for example described for IPv6 addresses
1926 in [RFC7721].
1928 15. Acknowledgement
1930 We would like to thank Alexander Pelov, Andrew McClure, Andrew
1931 McGregor, Bjoern Hoehrmann, Christian Amsuess, Christian Groves,
1932 Daniel Peintner, Jan-Piet Mens, Jim Schaad, Joe Hildebrand, John
1933 Klensin, Karl Palsson, Lennart Duhrsen, Lisa Dusseault, Lyndsay
1934 Campbell, Martin Thomson, Michael Koster, Peter Saint-Andre, and
1935 Stephen Farrell, for their review comments.
1937 16. References
1939 16.1. Normative References
1941 [BIPM] Bureau International des Poids et Mesures, "The
1942 International System of Units (SI)", 8th edition, 2006.
1944 [IEEE.754.1985]
1945 Institute of Electrical and Electronics Engineers,
1946 "Standard for Binary Floating-Point Arithmetic", IEEE
1947 Standard 754, August 1985.
1949 [NIST811] Thompson, A. and B. Taylor, "Guide for the Use of the
1950 International System of Units (SI)", NIST Special
1951 Publication 811, 2008.
1953 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
1954 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
1955 RFC2119, March 1997, .
1958 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
1959 DOI 10.17487/RFC3688, January 2004, .
1962 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
1963 Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
1964 .
1966 [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
1967 Specifications and Registration Procedures", BCP 13, RFC
1968 6838, DOI 10.17487/RFC6838, January 2013,
1969 .
1971 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
1972 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
1973 October 2013, .
1975 [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
1976 Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
1977 2014, .
1979 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
1980 Application Protocol (CoAP)", RFC 7252, DOI 10.17487/
1981 RFC7252, June 2014, .
1984 [RFC7303] Thompson, H. and C. Lilley, "XML Media Types", RFC 7303,
1985 DOI 10.17487/RFC7303, July 2014, .
1988 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
1989 Writing an IANA Considerations Section in RFCs", BCP 26,
1990 RFC 8126, DOI 10.17487/RFC8126, June 2017,
1991 .
1993 [W3C.REC-exi-20140211]
1994 Schneider, J., Kamiya, T., Peintner, D., and R. Kyusakov,
1995 "Efficient XML Interchange (EXI) Format 1.0 (Second
1996 Edition)", World Wide Web Consortium Recommendation REC-
1997 exi-20140211, February 2014,
1998 .
2000 [W3C.REC-xml-20081126]
2001 Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
2002 F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
2003 Edition)", World Wide Web Consortium Recommendation REC-
2004 xml-20081126, November 2008,
2005 .
2007 16.2. Informative References
2009 [I-D.arkko-core-dev-urn]
2010 Arkko, J., Jennings, C., and Z. Shelby, "Uniform Resource
2011 Names for Device Identifiers", draft-arkko-core-dev-urn-05
2012 (work in progress), October 2017.
2014 [I-D.ietf-cbor-cddl]
2015 Birkholz, H., Vigano, C., and C. Bormann, "Concise data
2016 definition language (CDDL): a notational convention to
2017 express CBOR data structures", draft-ietf-cbor-cddl-00
2018 (work in progress), July 2017.
2020 [I-D.ietf-core-interfaces]
2021 Shelby, Z., Vial, M., Koster, M., Groves, C., Zhu, J., and
2022 B. Silverajan, "Reusable Interface Definitions for
2023 Constrained RESTful Environments", draft-ietf-core-
2024 interfaces-10 (work in progress), September 2017.
2026 [IEEE802.1as-2011]
2027 IEEE, "IEEE Standard for Local and Metropolitan Area
2028 Networks - Timing and Synchronization for Time-Sensitive
2029 Applications in Bridged Local Area Networks", 2011.
2031 [IEEE802.1ba-2011]
2032 IEEE, "IEEE Standard for Local and metropolitan area
2033 networks--Audio Video Bridging (AVB) Systems", 2011.
2035 [ISO-80000-5]
2036 "Quantities and units - Part 5: Thermodynamics", ISO
2037 80000-5, Edition 1.0, May 2007.
2039 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
2040 Resource Identifier (URI): Generic Syntax", STD 66, RFC
2041 3986, DOI 10.17487/RFC3986, January 2005,
2042 .
2044 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
2045 Unique IDentifier (UUID) URN Namespace", RFC 4122, DOI
2046 10.17487/RFC4122, July 2005, .
2049 [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
2050 "Transmission of IPv6 Packets over IEEE 802.15.4
2051 Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
2052 .
2054 [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
2055 Address Text Representation", RFC 5952, DOI 10.17487/
2056 RFC5952, August 2010, .
2059 [RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
2060 Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
2061 .
2063 [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
2064 Morris, J., Hansen, M., and R. Smith, "Privacy
2065 Considerations for Internet Protocols", RFC 6973, DOI
2066 10.17487/RFC6973, July 2013, .
2069 [RFC7111] Hausenblas, M., Wilde, E., and J. Tennison, "URI Fragment
2070 Identifiers for the text/csv Media Type", RFC 7111, DOI
2071 10.17487/RFC7111, January 2014, .
2074 [RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
2075 Considerations for IPv6 Address Generation Mechanisms",
2076 RFC 7721, DOI 10.17487/RFC7721, March 2016,
2077 .
2079 [RFC8141] Saint-Andre, P. and J. Klensin, "Uniform Resource Names
2080 (URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,
2081 .
2083 [UCUM] Schadow, G. and C. McDonald, "The Unified Code for Units
2084 of Measure (UCUM)", Regenstrief Institute and Indiana
2085 University School of Informatics, 2013,
2086 .
2088 Authors' Addresses
2090 Cullen Jennings
2091 Cisco
2092 400 3rd Avenue SW
2093 Calgary, AB T2P 4H2
2094 Canada
2096 Email: fluffy@iii.ca
2097 Zach Shelby
2098 ARM
2099 150 Rose Orchard
2100 San Jose 95134
2101 USA
2103 Phone: +1-408-203-9434
2104 Email: zach.shelby@arm.com
2106 Jari Arkko
2107 Ericsson
2108 Jorvas 02420
2109 Finland
2111 Email: jari.arkko@piuha.net
2113 Ari Keranen
2114 Ericsson
2115 Jorvas 02420
2116 Finland
2118 Email: ari.keranen@ericsson.com
2120 Carsten Bormann
2121 Universitaet Bremen TZI
2122 Postfach 330440
2123 Bremen D-28359
2124 Germany
2126 Phone: +49-421-218-63921
2127 Email: cabo@tzi.org