Internet DRAFT - draft-bormann-cbor-notable-tags
draft-bormann-cbor-notable-tags
Network Working Group C. Bormann
Internet-Draft Universität Bremen TZI
Intended status: Informational 11 February 2024
Expires: 14 August 2024
Notable CBOR Tags
draft-bormann-cbor-notable-tags-10
Abstract
The Concise Binary Object Representation (CBOR, RFC 8949) is a data
format whose design goals include the possibility of extremely small
code size, fairly small message size, and extensibility without the
need for version negotiation.
In CBOR, one point of extensibility is the definition of CBOR tags.
RFC 8949's original edition, RFC 7049, defined a basic set of 16 tags
as well as a registry that can be used to contribute additional tag
definitions [IANA.cbor-tags]. Since RFC 7049 was published, at the
time of writing some 180 definitions of tags and ranges of tags have
been added to that registry.
The present document provides a roadmap to a large subset of these
tag definitions. Where applicable, it points to a IETF standards or
standard development document that specifies the tag. Where no such
document exists, the intention is to collect specification
information from the sources of the registrations. After some more
development, the present document is intended to be useful as a
reference document for the IANA registrations of the CBOR tags the
definitions of which have been collected.
Note to Readers
This is an individual submission to the CBOR working group of the
IETF, https://datatracker.ietf.org/wg/cbor/about/
(https://datatracker.ietf.org/wg/cbor/about/). Discussion currently
takes places on the github repository https://github.com/cabo/
notable-tags (https://github.com/cabo/notable-tags). If the CBOR WG
believes this is a useful document, discussion is likely to move to
the CBOR WG mailing list and a github repository at the CBOR WG
github organization, https://github.com/cbor-wg (https://github.com/
cbor-wg).
The current version is true work in progress; some of the sections
haven't been filled in yet, and in particular, permission has not
been obtained from tag definition authors to copy over their text.
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Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 14 August 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. RFC 7049 (original CBOR specification) . . . . . . . . . . . 4
2.1. Tags Related to Those Defined in RFC 7049 . . . . . . . . 5
2.2. Tags from RFC 7049 not listed in RFC 8949 . . . . . . . . 6
3. Security . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. COSE . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1.1. Tags for Bare Hash Values . . . . . . . . . . . . . . 7
3.2. RFC 8392 (CWT) . . . . . . . . . . . . . . . . . . . . . 9
4. CBOR-based Representation Formats . . . . . . . . . . . . . . 10
4.1. YANG-CBOR . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. DOTS . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.2. RAINS . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Datatypes . . . . . . . . . . . . . . . . . . . . . . . . . . 11
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6.1. Advanced arithmetic . . . . . . . . . . . . . . . . . . . 11
6.2. Variants of undefined . . . . . . . . . . . . . . . . . . 14
6.3. Typed and Homogeneous Arrays . . . . . . . . . . . . . . 14
7. Domain-Specific . . . . . . . . . . . . . . . . . . . . . . . 15
7.1. Human-readable Text . . . . . . . . . . . . . . . . . . . 16
7.2. Extended Time Formats . . . . . . . . . . . . . . . . . . 17
8. Platform-oriented . . . . . . . . . . . . . . . . . . . . . . 18
8.1. Perl . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.2. JSON . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.3. Weird text encodings . . . . . . . . . . . . . . . . . . 20
9. Application-specific . . . . . . . . . . . . . . . . . . . . 20
9.1. Enumerated Alternative Data Items . . . . . . . . . . . . 21
9.1.1. Semantics . . . . . . . . . . . . . . . . . . . . . . 23
9.1.2. Rationale . . . . . . . . . . . . . . . . . . . . . . 23
9.1.3. Examples . . . . . . . . . . . . . . . . . . . . . . 24
10. Implementation aids . . . . . . . . . . . . . . . . . . . . . 25
10.1. Invalid Tag . . . . . . . . . . . . . . . . . . . . . . 25
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
12. Security Considerations . . . . . . . . . . . . . . . . . . . 27
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
13.1. Normative References . . . . . . . . . . . . . . . . . . 27
13.2. Informative References . . . . . . . . . . . . . . . . . 28
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 31
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction
(TO DO, expand on text from abstract here; move references here and
neuter them in the abstract as per Section 4.3 of [RFC7322].)
The selection of the tags presented here is somewhat arbitrary;
considerations such as how wide the scope and area of application of
a tag definition is combine with an assessment how "ready to use" the
tag definition is (i.e., is the tag specification in a state where it
can be used).
This document can only be a snapshot of a subset of the current
registrations. The most up to date set of registrations is always
available in the registry "CBOR Tags" [IANA.cbor-tags].
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1.1. Terminology
The definitions of [STD94] apply. Specifically: The term "byte" is
used in its now customary sense as a synonym for "octet"; "byte
strings" are CBOR data items carrying a sequence of zero or more
(binary) bytes, while "text strings" are CBOR data items carrying a
sequence of zero or more Unicode code points, encoded in UTF-8
[STD63]. Where bit arithmetic is explained, this document uses the
notation familiar from the programming language C ([C], including
C++14's 0bnnn binary literals [Cplusplus20]), except that superscript
notation (example for two to the power of 64: 2^64) denotes
exponentiation; in the plain text version of this document,
superscript notation is rendered in paragraph text by C-incompatible
surrogate notation as seen in this example. Ranges expressed using
.. are inclusive of the limits given. Type names such as "int",
"bigint" or "decfrac" are taken from Appendix D of [RFC8610], the
Concise Data Definition Language (CDDL).
2. RFC 7049 (original CBOR specification)
[RFC7049] defines a number of tags that are listed here for
convenience only.
+============+=============+=======================+============+
| Tag number | Tag content | Short Description | Section of |
| | | | RFC 7049 |
+============+=============+=======================+============+
| 0 | UTF-8 | Standard date/time | 2.4.1 |
| | string | string | |
+------------+-------------+-----------------------+------------+
| 1 | multiple | Epoch-based date/time | 2.4.1 |
+------------+-------------+-----------------------+------------+
| 2 | byte string | Positive bignum | 2.4.2 |
+------------+-------------+-----------------------+------------+
| 3 | byte string | Negative bignum | 2.4.2 |
+------------+-------------+-----------------------+------------+
| 4 | array | Decimal fraction | 2.4.3 |
+------------+-------------+-----------------------+------------+
| 5 | array | Bigfloat | 2.4.3 |
+------------+-------------+-----------------------+------------+
| 21 | multiple | Expected conversion | 2.4.4.2 |
| | | to base64url encoding | |
+------------+-------------+-----------------------+------------+
| 22 | multiple | Expected conversion | 2.4.4.2 |
| | | to base64 encoding | |
+------------+-------------+-----------------------+------------+
| 23 | multiple | Expected conversion | 2.4.4.2 |
| | | to base16 encoding | |
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+------------+-------------+-----------------------+------------+
| 24 | byte string | Encoded CBOR data | 2.4.4.1 |
| | | item | |
+------------+-------------+-----------------------+------------+
| 32 | UTF-8 | URI | 2.4.4.3 |
| | string | | |
+------------+-------------+-----------------------+------------+
| 33 | UTF-8 | base64url | 2.4.4.3 |
| | string | | |
+------------+-------------+-----------------------+------------+
| 34 | UTF-8 | base64 | 2.4.4.3 |
| | string | | |
+------------+-------------+-----------------------+------------+
| 35 | UTF-8 | Regular expression | 2.4.4.3 |
| | string | | |
+------------+-------------+-----------------------+------------+
| 36 | UTF-8 | MIME message | 2.4.4.3 |
| | string | | |
+------------+-------------+-----------------------+------------+
| 55799 | multiple | Self-describe CBOR | 2.4.5 |
+------------+-------------+-----------------------+------------+
Table 1: Tag numbers defined in RFC 7049
2.1. Tags Related to Those Defined in RFC 7049
Separately registered tags that are directly related to the tags
predefined in RFC 7049 include:
* Tag 63, registered by this document (Section 11), is a parallel to
tag 24, with the single difference that its byte string tag
content carries a CBOR Sequence [RFC8742] instead of a single CBOR
data item.
* Tag 257, registered by Peter Occil with a specification in
http://peteroupc.github.io/CBOR/binarymime.html
(http://peteroupc.github.io/CBOR/binarymime.html), is a parallel
to tag 36, except that the tag content is a byte string, which
therefore can also carry binary MIME messages as per [RFC2045].
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* Tag 21065, being registered by this document (Section 11), is a
parallel to tag 35, with the difference that its text string tag
content carries an I-Regexp regular expression [RFC9485] instead
of a regexp of a more unspecified flavor. Companion tag 21066,
being registered by Joe Hildebrand with a specification in
https://github.com/hildjj/cbor-specs/blob/main/regexp.md
(https://github.com/hildjj/cbor-specs/blob/main/regexp.md), is the
equivalent for JavaScript (ECMA262), but besides the regular
expression itself also can include the regular expression flags as
a separate item.
2.2. Tags from RFC 7049 not listed in RFC 8949
Appendix G.3 of [STD94] states:
| Tag 35 is not defined by this document; the registration based on
| the definition in RFC 7049 remains in place.
The reason for this exclusion is that the definition of Tag 35 in
Section 2.4.4.3 of [RFC7049], leaves too much open to ensure
interoperability:
| Tag 35 is for regular expressions in Perl Compatible Regular
| Expressions (PCRE) / JavaScript syntax [ECMA262].
Not only are two partially incompatible specifications given for the
semantics, JavaScript regular expressions have also developed
significantly within the decade since JavaScript 5.1 (which was
referenced as "ECMA262" by [RFC7049]), making it less reliable to
assume that a producing application will manage to stay within that
2011 subset.
Nonetheless, the registration is in place, so it is available for
applications that simply want to mark a text string as being a
regular expression roughly of the PCRE/Javascript flavor families.
See also Tag 21065 and 21066 above.
3. Security
A number of CBOR tags are defined in security specifications that
make use of CBOR.
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3.1. COSE
CBOR Object Signing and Encryption (COSE) is defined in a number of
RFCs. [RFC8152] was the initial specification, set up the
registries, and populated them with an initial set of assignments. A
revision split this specification into the data structure definitions
RFC9052, an Internet Standard [STD96], and a separate document
defining the representation for the algorithms employed [RFC9053],
which is expected to be updated more frequently than the COSE format
itself. [RFC9054] added a separate set of algorithms for
cryptographic hash functions (Hash functions have been a component of
some [RFC9053] combined algorithms but weren't assigned separate
codepoints). A revised COSE counter signature structure was defined
in RFC9338, another part of [STD96]; this also defines a tag for
these.
+============+=======================+============================+
| Tag number | Tag content | Short Description |
+============+=======================+============================+
| 16 | COSE_Encrypt0 | COSE Single Recipient |
| | | Encrypted Data Object |
+------------+-----------------------+----------------------------+
| 17 | COSE_Mac0 | COSE Mac w/o Recipients |
| | | Object |
+------------+-----------------------+----------------------------+
| 18 | COSE_Sign1 | COSE Single Signer Data |
| | | Object |
+------------+-----------------------+----------------------------+
| 19 | COSE_Countersignature | COSE standalone V2 |
| | | countersignature (RFC9338) |
+------------+-----------------------+----------------------------+
| 96 | COSE_Encrypt | COSE Encrypted Data Object |
+------------+-----------------------+----------------------------+
| 97 | COSE_Mac | COSE MACed Data Object |
+------------+-----------------------+----------------------------+
| 98 | COSE_Sign | COSE Signed Data Object |
+------------+-----------------------+----------------------------+
Table 2: Tag numbers defined in RFC9052, COSE, and RFC 9338
3.1.1. Tags for Bare Hash Values
[RFC9054] does not define CBOR tags for cryptographic Hash values; it
rightly notes that Hash values are often used in structures that are
application-specific and should be defined with those applications.
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However, there are many cases where just a bare hash value is
required, and for these cases common tags are useful. In one use
case, these tags occur in a data structure that is specified to
indicate elision by using one of these tags as an alternative to some
other data structure. To enable agility, tags need to indicate the
hash function used, preferably using the COSE algorithms registry as
populated by [RFC9054].
| (Note that there is another registry, "Named Information Hash
| Algorithm Registry" [IANA.named-information], that also defines
| numbers for some hash algorithms. We are not using this
| registry here, as more recent entries seem to have stopped
| assigning numbers. If desired, tags that employ this registry
| could be added later.)
The codepoint range available for the COSE algorithms registry is
large, but the most likely range to be used for standard Hash
functions is "Integer values between -256 and 255", which have the
registry policy "Standards Action With Expert Review" (Section 16.4
of [RFC8152], Registry "COSE Algorithms" [IANA.cose]).
To this end, the present document registers a range of 512 tags from
18300 to 18811 (inclusive), paralleling the algorithm identifier
range of -256 .. 255 (inclusive). The tag number for COSE algorithm
number N is then defined to be 18556+N, except for N = 0 (see below).
The tag value is a CBOR byte string, with the exception N = 0.
For example, in [IANA.cose] SHA-256 has the COSE algorithm identifier
-16. This is in the range -256 .. 255 (inclusive range). Therefore,
tag 18540 (= 18556 + (-16)) is the tag for a byte string containing a
SHA-256 hash.
As a special case, there is one exception: Tag 18556 (= 18556 + 0)
stands for the combination of a an explicit numeric COSE algorithm
identifier with a hash value in an array, analogous to the use of
COSE_CertHash in [RFC9360]:
Standard_COSE_Hash<alg, value> =
#6.<hashmiddle .plus (alg .within directhash)>(value)
General_COSE_Hash<alg, value> = #6.<hashmiddle>([
hashAlg: alg .within (int .ne directhash / tstr),
hashValue: value .within bstr ])
hashmiddle = 18556
directhash = (-256 .. -1) / (1 .. 255)
Figure 1: Generic CDDL for Tags for Bare Hash Values
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An example for the SHA-256 hash of "hello world" in CBOR diagnostic
notation:
18540(
h'b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9')
The same in CBOR pretty printed hex:
=============== NOTE: '\' line wrapping per RFC 8792 ================
d9 486c # tag(18540)
58 20 # bytes(32)
\
b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9
As none has been registered, no real example can be given for a hash
algorithm with an identifier not in the standard range, but if -4711
were such an identifier, a hash with an explicit algorithm number
could look like:
18556([-4711, h'1234123412341234123412341234123412341234'])
Note that not all tags assigned in this section do parallel an
algorithm that is a cryptographic hash algorithm. Where this is not
the case, there currently is not defined semantics for this tag, but
the tags are assigned anyway. The semantics of tags that parallel
algorithm assignments other than for cryptographic hash functions
could be defined by a future version of this specification.
Note also that the cryptographic hashes in the content of the tag are
not protected; any further protection (confidentiality, integrity)
needs to be provided in the surrounding data structure, storage
system, or communication channel.
3.2. RFC 8392 (CWT)
[RFC8392] defines the CBOR Web Token (CWT), making use of COSE to
define a CBOR variant of the JOSE Web Token (JWT), [RFC7519], a
standardized security token that has found use in the area of web
applications, but is not technically limited to those.
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+============+======================+======================+
| Tag number | Tag content | Short Description |
+============+======================+======================+
| 61 | CBOR Web Token (CWT) | CBOR Web Token (CWT) |
+------------+----------------------+----------------------+
Table 3: Tag number defined for RFC 8392 CBOR Web Token
(CWT)
4. CBOR-based Representation Formats
Representation formats can be built on top of CBOR.
4.1. YANG-CBOR
YANG [RFC7950] is a data modeling language originally designed in the
context of the Network Configuration Protocol (NETCONF) [RFC6241],
now widely used for modeling management and configuration
information. [RFC7950] defines an XML-based representation format,
and [RFC7951] defines a JSON-based [RFC8259] representation format
for YANG.
YANG-CBOR [RFC9254] is a representation format for YANG data in CBOR.
+========+======================+=====================+============+
| Tag | Tag content | Short Description | Section of |
| number | | | YANG-CBOR |
+========+======================+=====================+============+
| 43 | byte string | YANG bits datatype | 6.7 |
+--------+----------------------+---------------------+------------+
| 44 | unsigned integer | YANG enumeration | 6.6 |
| | | datatype | |
+--------+----------------------+---------------------+------------+
| 45 | unsigned integer or | YANG identityref | 6.10 |
| | text string | datatype | |
+--------+----------------------+---------------------+------------+
| 46 | unsigned integer or | YANG instance- | 6.13 |
| | text string or array | identifier datatype | |
+--------+----------------------+---------------------+------------+
| 47 | unsigned integer | YANG Schema Item | 3.2 |
| | | iDentifier (sid) | |
+--------+----------------------+---------------------+------------+
Table 4: Tag number defined for YANG-CBOR
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5. Protocols
Protocols may want to allocate CBOR tag numbers to identify specific
protocol elements.
5.1. DOTS
DDoS Open Threat Signaling (DOTS) defines tag number 271 for the DOTS
signal channel object in [RFC9132].
5.2. RAINS
As an example for how experimental protocols can make use of CBOR tag
definitions, the RAINS (Another Internet Naming Service) Protocol
Specification defines tag number 15309736 for a RAINS Message
[I-D.trammell-rains-protocol]. (The seemingly random tag number was
chosen so that, when represented as an encoded CBOR tag argument, it
contains the Unicode character "雨" (U+96E8) in UTF-8, which
represents rain in a number of languages.)
6. Datatypes
6.1. Advanced arithmetic
A number of tags have been registered for arithmetic representations
beyond those built into CBOR and defined by tags in [RFC7049]. These
are all documented under http://peteroupc.github.io/CBOR/; the last
pathname component for the URL is given in Table 5.
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+============+=============+=======================+===============+
| Tag number | Tag content | Short Description | Reference |
+============+=============+=======================+===============+
| 30 | array | Rational number | rational.html |
+------------+-------------+-----------------------+---------------+
| 264 | array | Decimal fraction with | bigfrac.html |
| | | arbitrary exponent | |
+------------+-------------+-----------------------+---------------+
| 265 | array | Bigfloat with | bigfrac.html |
| | | arbitrary exponent | |
+------------+-------------+-----------------------+---------------+
| 268 | array | Extended decimal | extended.html |
| | | fraction | |
+------------+-------------+-----------------------+---------------+
| 269 | array | Extended bigfloat | extended.html |
+------------+-------------+-----------------------+---------------+
| 270 | array | Extended rational | extended.html |
| | | number | |
+------------+-------------+-----------------------+---------------+
Table 5: Tags for advanced arithmetic
CBOR's basic generic data model (Section 2 of [STD94]) has a number
system with limited-range integers (major types 0 and 1:
-2^64..2^64-1) and floating point numbers that cover binary16,
binary32, and binary64 (including non-finites) from [IEEE754]. With
the tags defined with [RFC7049], the extended generic data model
(Section 2.1 of [STD94]) adds unlimited-range integers (tag numbers 2
and 3, "bigint" in CDDL) as well as floating point values using the
bases 2 (tag number 5, "bigfloat") and 10 (tag number 4, "decfrac").
This pre-defined number system has a number of limitations that are
addressed in three of the tags discussed here:
* Tag number 30 allows the representation of rational numbers as a
ratio of two integers: a numerator (usually written as the top
part of a fraction), and a denominator (the bottom part), where
both integers can be limited-range basic and unlimited-range
integers. The mathematical value of a rational number is the
numerator divided by the denominator. This tag can express all
numbers that the extended generic data model of [RFC7049] can
express, except for non-finites [IEEE754]; it also can express
rational numbers that cannot be expressed with denominators that
are a power of 2 or a power of 10.
For example, the rational number 1/3 is encoded:
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d8 1e ---- Tag 30
82 ---- Array length 2
01 ---- 1
03 ---- 3
Many programming languages have built-in support for rational
numbers or support for them is included in their standard
libraries; tag number 30 is a way for these platforms to
interchange these rational numbers in CBOR.
* Tag numbers 4 and 5 are limited in the range of the (base 10 or
base 2) exponents by the limited-range integers in the basic
generic data model. Tag numbers 264 and 265 are exactly
equivalent to 4 and 5, respectively, but also allow unlimited-
range integers as exponents. While applications for floating
point numbers with exponents outside the CBOR basic integer range
are limited, tags 264 and 265 allow unlimited roundtripping with
other formats that allow very large or very small exponents, such
as those JSON [RFC8259] can provide if the limitations of I-JSON
[RFC7493] do not apply.
The tag numbers 268..270 extend these tags further by providing a way
to express non-finites within a tag with this number. This does not
increase the expressiveness of the data model (the non-finites can
already be expressed using major type 7 floating point numbers), but
does allow both finite and non-finite values to carry the same tag.
In most applications, a choice that includes some of the three tags
30, 264, 265 for finite values and major type 7 floating point values
for non-finites (as well as possibly other parts of the CBOR number
system) will be the preferred solution.
This document suggests using the CDDL typenames defined in Figure 2
for the three most useful tag numbers in this section.
rational = #6.30([numerator: integer, denominator: integer .ne 0])
rational_of<N,D> = #6.30([numerator: N, denominator: D])
; the value 1/3 can be notated as rational_of<1, 3>
extended_decfrac = #6.264([e10: integer, m: integer])
extended_bigfloat = #6.265([e2: integer, m: integer])
Figure 2: CDDL for extended arithmetic tags
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6.2. Variants of undefined
https://github.com/svaarala/cbor-specs/blob/master/cbor-absent-
tag.rst defines tag 31 to be applied to the CBOR value Undefined
(0xf7), slightly modifying its semantics to stand for an absent value
in a CBOR Array.
(TO DO: Obtain permission to copy the definitions here.)
6.3. Typed and Homogeneous Arrays
[RFC8746] defines tags for various kinds of arrays. A summary is
reproduced in Table 6.
+======+=============+=============================================+
| Tag | Data Item | Semantics |
+======+=============+=============================================+
| 64 | byte string | uint8 Typed Array |
+------+-------------+---------------------------------------------+
| 65 | byte string | uint16, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 66 | byte string | uint32, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 67 | byte string | uint64, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 68 | byte string | uint8 Typed Array, clamped arithmetic |
+------+-------------+---------------------------------------------+
| 69 | byte string | uint16, little endian, Typed Array |
+------+-------------+---------------------------------------------+
| 70 | byte string | uint32, little endian, Typed Array |
+------+-------------+---------------------------------------------+
| 71 | byte string | uint64, little endian, Typed Array |
+------+-------------+---------------------------------------------+
| 72 | byte string | sint8 Typed Array |
+------+-------------+---------------------------------------------+
| 73 | byte string | sint16, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 74 | byte string | sint32, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 75 | byte string | sint64, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 76 | byte string | (reserved) |
+------+-------------+---------------------------------------------+
| 77 | byte string | sint16, little endian, Typed Array |
+------+-------------+---------------------------------------------+
| 78 | byte string | sint32, little endian, Typed Array |
+------+-------------+---------------------------------------------+
| 79 | byte string | sint64, little endian, Typed Array |
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+------+-------------+---------------------------------------------+
| 80 | byte string | IEEE 754 binary16, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 81 | byte string | IEEE 754 binary32, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 82 | byte string | IEEE 754 binary64, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 83 | byte string | IEEE 754 binary128, big endian, Typed Array |
+------+-------------+---------------------------------------------+
| 84 | byte string | IEEE 754 binary16, little endian, Typed |
| | | Array |
+------+-------------+---------------------------------------------+
| 85 | byte string | IEEE 754 binary32, little endian, Typed |
| | | Array |
+------+-------------+---------------------------------------------+
| 86 | byte string | IEEE 754 binary64, little endian, Typed |
| | | Array |
+------+-------------+---------------------------------------------+
| 87 | byte string | IEEE 754 binary128, little endian, Typed |
| | | Array |
+------+-------------+---------------------------------------------+
| 40 | array of | Multi-dimensional Array, row-major order |
| | two arrays* | |
+------+-------------+---------------------------------------------+
| 1040 | array of | Multi-dimensional Array, column-major order |
| | two arrays* | |
+------+-------------+---------------------------------------------+
| 41 | array | Homogeneous Array |
+------+-------------+---------------------------------------------+
Table 6: Tag numbers defined for Arrays
7. Domain-Specific
(TO DO: Obtain permission to copy the definitions here; explain how
tags 52 and 54 essentially obsolete 260/261.)
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+======+=======+=================+=================================+========+
|Tag |Tag |Short Description|Reference |Author |
|number|content| | | |
+======+=======+=================+=================================+========+
|37 |byte |Binary UUID |https://github.com/lucas- |Lucas |
| |string |(Section 4.1.2 of|clemente/cbor-specs/blob/master/ |Clemente|
| | |[RFC4122]) |uuid.md | |
+------+-------+-----------------+---------------------------------+--------+
|257 |byte |Binary MIME |http://peteroupc.github.io/CBOR/ |Peter |
| |string |message |binarymime.html |Occil |
+------+-------+-----------------+---------------------------------+--------+
|260 |byte |Network Address |http://www.employees.org/~ravir/ |Ravi |
| |string |(IPv4 or IPv6 or |cbor-network.txt |Raju |
| | |MAC Address) | | |
+------+-------+-----------------+---------------------------------+--------+
|261 |map |Network Address |https://github.com/toravir/CBOR- |Ravi |
| | |Prefix (IPv4 or |Tag-Specs/blob/master/ |Raju |
| | |IPv6 Address + |networkPrefix.md | |
| | |Mask Length) | | |
+------+-------+-----------------+---------------------------------+--------+
|263 |byte |Hexadecimal |https://github.com/toravir/CBOR- |Ravi |
| |string |string |Tag-Specs/blob/master/ |Raju |
| | | |hexString.md | |
+------+-------+-----------------+---------------------------------+--------+
|266 |text |Internationalized|https://peteroupc.github.io/CBOR/|Peter |
| |string |resource |iri.html |Occil |
| | |identifier (IRI) | | |
+------+-------+-----------------+---------------------------------+--------+
|267 |text |Internationalized|https://peteroupc.github.io/CBOR/|Peter |
| |string |resource |iri.html |Occil |
| | |identifier | | |
| | |reference (IRI | | |
| | |reference) | | |
+------+-------+-----------------+---------------------------------+--------+
Table 7
7.1. Human-readable Text
+=====+===========+========================+==============+
| Tag | Data Item | Semantics | Reference |
+=====+===========+========================+==============+
| 38 | array | Language-tagged string | Appendix A |
| | | | of [RFC9290] |
+-----+-----------+------------------------+--------------+
Table 8
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Tag 38 was originally registered by Peter Occil in
http://peteroupc.github.io/CBOR/langtags.html
(http://peteroupc.github.io/CBOR/langtags.html); it has since been
adopted and extended in Appendix A of [RFC9290], where a detailed
definition of the tag and a few simple examples for its use are
provided.
The problem that this tag was designed to solve is that text strings
often need additional information to be properly presented to a
human. While Unicode (and the UTF-8 form of Unicode used in CBOR)
define the characters, additional information about the human
language in use and the writing direction appropriate for the text
given are often required.
The need to provide language information with text has been well-
known for a while and led to a common form for this information, the
language tag, defined in [BCP47].
Less well-known is the need to provide separate directionality
information as well. The need for this information is demonstrated
in [W3C-STRINGS-BIDI], which points out that it is "actually a bad
idea to rely on language information to apply direction" and points
out further reference information on this. [W3C-BIDI-USE-CASES]
shows more examples for language tags and directionality, while
[W3C-UBA-BASICS] provides an introduction to the way browsers, where
"the order of characters in memory (logical) is not the same as the
order in which they are displayed (visual)", "produce the correct
order at the time of display" (Unicode Bidirectional Algorithm).
Tag 38 meets the requirements of its specific application in
[RFC9290], which could be summarized as: Supplying the necessary
information to present isolated, linear, comparatively small pieces
of human-readable text. It neither addresses more complex
requirements of specific languages such as [W3C-SIMPLE-RUBY], nor
does it address requirements for more complex structure in texts such
as emphasis, lists, or tables. These more complex requirements are
typically met by specific media types such as HTML [HTML].
7.2. Extended Time Formats
Additional tag definitions have been provided for date and time
values.
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+======+===========+===================+==========================+
| Tag | Data Item | Semantics | Reference |
+======+===========+===================+==========================+
| 100 | integer | date in number of | [RFC8943] |
| | | days since epoch | |
+------+-----------+-------------------+--------------------------+
| 1004 | text | RFC 3339 full- | [RFC8943] |
| | string | date string | |
+------+-----------+-------------------+--------------------------+
| 1001 | map | extended time | [I-D.ietf-cbor-time-tag] |
+------+-----------+-------------------+--------------------------+
| 1002 | map | duration | [I-D.ietf-cbor-time-tag] |
+------+-----------+-------------------+--------------------------+
| 1003 | map | period | [I-D.ietf-cbor-time-tag] |
+------+-----------+-------------------+--------------------------+
Table 9: Tag numbers for date and time
Note that tags 100 and 1004 are for calendar dates that are not
anchored to a specific time zone; they are meant to specify calendar
dates as perceived by humans, e.g. for use in personal identification
documents. Converting such a calendar date into a specific point in
time needs the addition of a time-of-day (for which a CBOR tag is
outstanding) and timezone information (also outstanding).
Alternatively, a calendar date plus timezone information can be
converted into a time period (range of time values given by the
starting and the ending time); note that these time periods are not
always exactly 24 h (86400 s) long.
[RFC8943] does not suggest CDDL [RFC8610] type names for the two
tags. We suggest copying the definitions in Figure 3 into
application-specific CDDL as needed.
caldate = #6.100(int); calendar date as # of days from 1970-01-01
tcaldate = #6.1004(tstr); calendar date as RFC 3339 full-date string
Figure 3: CDDL for calendar date tags (RFC8943)
Tag 1001 extends tag 1 by additional information (such as picosecond
resolution) and allows the use of Decimal and Bigfloat numbers for
the time.
8. Platform-oriented
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8.1. Perl
(These are actually not as Perl-specific as the title of this section
suggests. See also the penultimate paragraph of Section 3.4 of
[STD94].)
These are all documented under http://cbor.schmorp.de/; the last
pathname component is given in Table 10.
(TO DO: Obtain permission to copy the definitions here.)
+=======+==========+========================+================+
| Tag | Data | Semantics | Reference |
| | Item | | |
+=======+==========+========================+================+
| 256 | multiple | mark value as having | stringref |
| | | string references | |
+-------+----------+------------------------+----------------+
| 25 | unsigned | reference the nth | stringref |
| | integer | previously seen string | |
+-------+----------+------------------------+----------------+
| 26 | array | Serialized Perl object | perl-object |
| | | with classname and | |
| | | constructor arguments | |
+-------+----------+------------------------+----------------+
| 27 | array | Serialized language- | generic-object |
| | | independent object | |
| | | with type name and | |
| | | constructor arguments | |
+-------+----------+------------------------+----------------+
| 28 | multiple | mark value as | value-sharing |
| | | (potentially) shared | |
+-------+----------+------------------------+----------------+
| 29 | unsigned | reference nth marked | value-sharing |
| | integer | value | |
+-------+----------+------------------------+----------------+
| 22098 | multiple | hint that indicates an | indirection |
| | | additional level of | |
| | | indirection | |
+-------+----------+------------------------+----------------+
Table 10: Tag numbers that aid the Perl platform
8.2. JSON
(TO DO: Obtain permission to copy the definitions here.)
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Tag number 262 has been registered to identify byte strings that
carry embedded JSON text (https://github.com/toravir/CBOR-Tag-
Specs/blob/master/embeddedJSON.md).
Tag number 275 can be used to identify maps that contain keys that
are all of type Text String, as they would occur in JSON
(https://github.com/ecorm/cbor-tag-text-key-map).
8.3. Weird text encodings
(TO DO: Obtain permission to copy the definitions here.)
Some variants of UTF-8 are in use in specific areas of application.
Tags have been registered to be able to carry around strings in these
variants in case they are not also valid UTF-8 and can therefore not
be represented as a CBOR text string (https://github.com/svaarala/
cbor-specs/blob/master/cbor-nonutf8-string-tags.rst).
+============+=============+=========================+
| Tag Number | Data Item | Semantics |
+============+=============+=========================+
| 272 | byte string | Non-UTF-8 CESU-8 string |
+------------+-------------+-------------------------+
| 273 | byte string | Non-UTF-8 WTF-8 string |
+------------+-------------+-------------------------+
| 274 | byte string | Non-UTF-8 MUTF-8 string |
+------------+-------------+-------------------------+
Table 11: Tag numbers for UTF-8 variants
9. Application-specific
(TO DO: Obtain permission to copy the definitions here.)
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+======+========+========================+===================================================+========+
|Tag |Tag |Short Description |Reference |Author |
|number|content | | | |
+======+========+========================+===================================================+========+
|39 |multiple|Identifier |https://github.com/lucas-clemente/cbor- |Lucas |
| | | |specs/blob/master/id.md (https://github.com/lucas- |Clemente|
| | | |clemente/cbor-specs/blob/master/id.md) | |
+------+--------+------------------------+---------------------------------------------------+--------+
|42 |byte |IPLD content identifier |https://github.com/ipld/cid-cbor/ |Volker |
| |string | |(https://github.com/ipld/cid-cbor/) |Mische |
+------+--------+------------------------+---------------------------------------------------+--------+
|103 |array |Geographic Coordinates |https://github.com/allthingstalk/cbor/blob/master/ |Danilo |
| | | |CBOR-Tag103-Geographic-Coordinates.md |Vidovic |
| | | |(https://github.com/allthingstalk/cbor/blob/master/| |
| | | |CBOR-Tag103-Geographic-Coordinates.md) | |
+------+--------+------------------------+---------------------------------------------------+--------+
|104 |multiple|Geographic Coordinate |[I-D.clarke-cbor-crs] | |
| | |Reference System WKT or | | |
| | |EPSG number | | |
+------+--------+------------------------+---------------------------------------------------+--------+
|120 |multiple|Internet of Things Data |https://github.com/allthingstalk/cbor/blob/master/ |Danilo |
| | |Point |CBOR-Tag120-Internet-of-Things-Data-Points.md |Vidovic |
| | | |(https://github.com/allthingstalk/cbor/blob/master/| |
| | | |CBOR-Tag120-Internet-of-Things-Data-Points.md) | |
+------+--------+------------------------+---------------------------------------------------+--------+
|258 |array |Mathematical finite set |https://github.com/input-output-hk/cbor-sets- |Alfredo |
| | | |spec/blob/master/CBOR_SETS.md (https://github.com/ |Di |
| | | |input-output-hk/cbor-sets-spec/blob/master/ |Napoli |
| | | |CBOR_SETS.md) | |
+------+--------+------------------------+---------------------------------------------------+--------+
|259 |map |Map datatype with key- |https://github.com/shanewholloway/js-cbor- |Shane |
| | |value operations (e.g. |codec/blob/master/docs/CBOR-259-spec--explicit- |Holloway|
| | |.get()/.set()/.delete())|maps.md (https://github.com/shanewholloway/js-cbor-| |
| | | |codec/blob/master/docs/CBOR-259-spec--explicit- | |
| | | |maps.md) | |
+------+--------+------------------------+---------------------------------------------------+--------+
Table 12
9.1. Enumerated Alternative Data Items
(Original Text for this section was contributed by Duncan Coutts and
Michael Peyton Jones; all errors are the author's.)
A set of CBOR tag numbers has been allocated (Section 11) for
encoding data composed of enumerated alternatives:
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+============+=============+===================================+
| Tags | Data Item | Meaning |
+============+=============+===================================+
| 121..127 | any | alternatives 0..6, 1+1 encoding |
+------------+-------------+-----------------------------------+
| 1280..1400 | any | alternatives 7..127, 1+2 encoding |
+------------+-------------+-----------------------------------+
| 101 | array | alternatives as given by the uint |
| | [uint, any] | + 128 |
+------------+-------------+-----------------------------------+
Table 13: Tags for Enumerated Alternative Data Items
The tags defined in this section are for encoding data that can be in
one of a number of different enumerated forms.
For example data representing the result of some action might be
either a failure with some failure detail, or a success with some
result. In this example there are two cases, the failure case and
the success case, and we can enumerate them as 0 and 1.
In general the number of alternatives, and what data is expected in
each alternative case is entirely application dependent.
The tags defined in this specification allow the encoding of any
number of alternatives, but provide compact encoding for the common
cases of low numbers of alternatives:
* Alternatives 0..6 can be encoded in 2 bytes;
* Alternatives 7..127 can be encoded in 3 bytes;
* Alternatives 128+ can be encoded in 3-12 bytes.
There are no special considerations for deterministic encoding
Section 4.2 of [STD94]: The case numbers covered by each tag do not
overlap; particularly, tag 101 encoding starts where the more compact
special encodings for 0..6 and 7..127 end.
For cases 0..6 and 7..127, the tag value indicates the value of the
alternative. For cases 128+, a single tag number is used with an
enclosed two-element array that contains the case number and the
value of the alternative.
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9.1.1. Semantics
The value consists of a case number and a case body. The case number
is an unsigned integer that indicates which case out of the set of
alternatives is used. The case body is any CBOR data value.
In a setting where the application uses a schema (formally or
informally), then there will be an appropriate sub-schema for each
case in the set of alternatives. The representation of the case body
should comply with the schema corresponding to the case number used.
To continue the example above about representing failure or success,
suppose that the failure detail consists of an integer code and a
string, and suppose that the successful result is a byte string. A
failure value will use case 0 and the case body will be a CBOR list
containing an integer and a text string. Alternatively, a success
value will use case 1 and the body will be a single CBOR byte string.
Decoders that enforce a schema must check the case number is within
the range of cases allowed, and that the case body follows the schema
for the supplied case number. Generic decoders should allow any case
number and any CBOR data value for the case body.
9.1.2. Rationale
CBOR has direct support for _combinations_ of multiple values but not
for _alternatives_ of multiple values. Combinations are expressed in
CBOR using lists or maps.
Most programming languages have a notion of data consisting of
combinations of data values, often called records, structs or
objects. Many programming languages also have a notion of data
consisting of multiple alternative data values. For example C has
unions, and other languages have "tagged" unions (where it is always
clear which alternative is in use).
Crucially for this set of tags, the set of alternatives must be
closed and ordered. This allows encoding using an unsigned number to
distinguish each case.
Note that this does _not_ correspond to the notion in some
programming languages of classes and subclasses since in that context
the set of alternatives is open and unordered. Alternatives of this
kind are well-supported by tag 27 "Serialized language-independent
object with type name and constructor arguments".
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In functional programming languages, the primary way of forming new
data types is to enumerate a set of alternatives (each of which may
be a record). Such forms of data are also supported in hybrid
functional languages or languages with functional features.
Thus, in some applications, it is very common to have data making use
of alternatives, and it is worth finding a compact encoding, at least
for the common cases. Just as most records are small, most
alternatives are also small.
In this specification we reserve 7 values in the 2-byte part of the
available tag encoding space for alternatives 0..6 which are by far
the most common. We reserve a range of 121 values in the 3-bytes tag
encoding space. To cover the general case we use an encoding using a
pair consisting of an unsigned integer and the case body, the first
24 of which also result in a 3-byte encoding.
9.1.3. Examples
To elaborate on the example from the introduction, we have a "result"
that is a failure or success, where:
* the failure detail consists of an integer code and a string;
* the successful result is a byte string.
This corresponds to the following schema, in CDDL notation:
result = #6.121([int, text])
/ #6.122(bytes)
Example values:
121([3, "the printer is on fire"])
122(h'ff00')
As a second example, here is one based on a data type defined within
the Haskell programming language, representing a simple expression
tree.
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-- A data type representing simple arithmetic expressions
data Expr = Lit Int -- integer literal
| Add Expr Expr -- addition
| Sub Expr Expr -- subtraction
| Neg Expr -- unary negation
| Mul Expr Expr -- multiplication
| Div Expr Expr -- integer division
In CDDL notation, and using the tags in this specification, such data
could be encoded using this schema:
; A data type representing simple arithmetic expressions
expr = 121(int) ; integer literal
/ 122([expr, expr]) ; addition
/ 123([expr, expr]) ; subtraction
/ 124(expr) ; unary negation
/ 125([expr, expr]) ; multiplication
/ 126([expr, expr]) ; integer division
10. Implementation aids
10.1. Invalid Tag
The present document registers tag numbers 65535, 4294967295, and
18446744073709551615 (16-bit 0xffff, 32-bit 0xffffffff, and 64-bit
0xffffffffffffffff) as Invalid Tags, tags that are always invalid,
independent of the tag content provided. The purpose of these tag
number registrations is to enable the tag numbers to be reserved for
internal use by implementations to note the absence of a tag on a
data item where a tag could also be expected with that data item as
tag content.
The Invalid Tags are not intended to ever occur in interchanged CBOR
data items. Generic CBOR decoder implementations are encouraged to
raise an error if an Invalid Tag occurs in a CBOR data item even if
there is no validity checking implemented otherwise.
11. IANA Considerations
In the registry "CBOR Tags" [IANA.cbor-tags], IANA has allocated the
first to third tag in Table 14 from the FCFS space, with the present
document as the specification reference. IANA has allocated the tags
in the next two rows, and is requested to allocate the tags in the
next three rows, from the Specification Required space, with the
present document as the specification reference.
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+======================+========+=============+====================+
| Tag | Data | Semantics | Reference |
| | Item | | |
+======================+========+=============+====================+
| 65535 | (none | always | draft-bormann- |
| | valid) | invalid | cbor-notable-tags, |
| | | | Section 10.1 |
+----------------------+--------+-------------+--------------------+
| 4294967295 | (none | always | draft-bormann- |
| | valid) | invalid | cbor-notable-tags, |
| | | | Section 10.1 |
+----------------------+--------+-------------+--------------------+
| 18446744073709551615 | (none | always | draft-bormann- |
| | valid) | invalid | cbor-notable-tags, |
| | | | Section 10.1 |
+----------------------+--------+-------------+--------------------+
| 63 | byte | Encoded | draft-bormann- |
| | string | CBOR | cbor-notable-tags, |
| | | Sequence | Section 2.1 |
| | | [RFC8742] | |
+----------------------+--------+-------------+--------------------+
| 21065 | text | I-Regexp | draft-bormann- |
| | string | | cbor-notable-tags, |
| | | | Section 2.1; |
| | | | [RFC9485] |
+----------------------+--------+-------------+--------------------+
| 18300 to 18555 | byte | Bare Hash | draft-bormann- |
| (inclusive) | string | value (COSE | cbor-notable-tags, |
| | | algorithm | Section 3.1.1 |
| | | -256 to -1) | |
+----------------------+--------+-------------+--------------------+
| 18556 | array | [COSE | draft-bormann- |
| | | algorithm | cbor-notable-tags, |
| | | identifier, | Section 3.1.1 |
| | | Bare Hash | |
| | | value] | |
+----------------------+--------+-------------+--------------------+
| 18557 to 18811 | byte | Bare Hash | draft-bormann- |
| (inclusive) | string | value (COSE | cbor-notable-tags, |
| | | algorithm 1 | Section 3.1.1 |
| | | to 255) | |
+----------------------+--------+-------------+--------------------+
Table 14: Values for Tags
In addition, IANA is requested to allocate the tags from Table 13,
with a reference to the present document.
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12. Security Considerations
The security considerations of [STD94] apply; the tags discussed here
may also have specific security considerations that are mentioned in
their specific sections above.
13. References
13.1. Normative References
[IANA.cbor-tags]
IANA, "Concise Binary Object Representation (CBOR) Tags",
<https://www.iana.org/assignments/cbor-tags>.
[IANA.cose]
IANA, "CBOR Object Signing and Encryption (COSE)",
<https://www.iana.org/assignments/cose>.
[IANA.named-information]
IANA, "Named Information",
<https://www.iana.org/assignments/named-information>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/rfc/rfc8392>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.
[RFC8746] Bormann, C., Ed., "Concise Binary Object Representation
(CBOR) Tags for Typed Arrays", RFC 8746,
DOI 10.17487/RFC8746, February 2020,
<https://www.rfc-editor.org/rfc/rfc8746>.
[RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053,
August 2022, <https://www.rfc-editor.org/rfc/rfc9053>.
[RFC9054] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Hash Algorithms", RFC 9054, DOI 10.17487/RFC9054, August
2022, <https://www.rfc-editor.org/rfc/rfc9054>.
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[RFC9132] Boucadair, M., Ed., Shallow, J., and T. Reddy.K,
"Distributed Denial-of-Service Open Threat Signaling
(DOTS) Signal Channel Specification", RFC 9132,
DOI 10.17487/RFC9132, September 2021,
<https://www.rfc-editor.org/rfc/rfc9132>.
[RFC9360] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Header Parameters for Carrying and Referencing X.509
Certificates", RFC 9360, DOI 10.17487/RFC9360, February
2023, <https://www.rfc-editor.org/rfc/rfc9360>.
[STD63] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/rfc/rfc3629>.
[STD94] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>.
[STD96] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052, August 2022.
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Countersignatures", STD 96, RFC 9338, December 2022.
<https://www.rfc-editor.org/info/std96>
13.2. Informative References
[BCP47] Phillips, A., Ed. and M. Davis, Ed., "Matching of Language
Tags", BCP 47, RFC 4647, September 2006.
Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
Languages", BCP 47, RFC 5646, September 2009.
<https://www.rfc-editor.org/info/bcp47>
[C] International Organization for Standardization,
"Information technology — Programming languages — C", ISO/
IEC 9899:2018, June 2018,
<https://www.iso.org/standard/74528.html>.
[Cplusplus20]
International Organization for Standardization,
"Programming languages — C++", ISO/IEC ISO/IEC JTC1 SC22
WG21 N 4860, March 2020,
<https://isocpp.org/files/papers/N4860.pdf>.
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[HTML] WHATWG, "HTML — Living Standard",
<https://html.spec.whatwg.org>.
[I-D.clarke-cbor-crs]
Clarke, T., "Concise Binary Object Representation (CBOR)
Tag for Coordinate Reference System (CRS) Specification",
Work in Progress, Internet-Draft, draft-clarke-cbor-crs-
02, 17 March 2020, <https://datatracker.ietf.org/doc/html/
draft-clarke-cbor-crs-02>.
[I-D.ietf-cbor-time-tag]
Bormann, C., Gamari, B., and H. Birkholz, "Concise Binary
Object Representation (CBOR) Tags for Time, Duration, and
Period", Work in Progress, Internet-Draft, draft-ietf-
cbor-time-tag-12, 30 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-cbor-
time-tag-12>.
[I-D.trammell-rains-protocol]
Trammell, B. and C. Fehlmann, "RAINS (Another Internet
Naming Service) Protocol Specification", Work in Progress,
Internet-Draft, draft-trammell-rains-protocol-05, 29
January 2019, <https://datatracker.ietf.org/doc/html/
draft-trammell-rains-protocol-05>.
[IEEE754] IEEE, "IEEE Standard for Floating-Point Arithmetic", IEEE
Std 754-2019, DOI 10.1109/IEEESTD.2019.8766229,
<https://ieeexplore.ieee.org/document/8766229>.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
<https://www.rfc-editor.org/rfc/rfc2045>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/rfc/rfc4122>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/rfc/rfc6241>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/rfc/rfc7049>.
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[RFC7322] Flanagan, H. and S. Ginoza, "RFC Style Guide", RFC 7322,
DOI 10.17487/RFC7322, September 2014,
<https://www.rfc-editor.org/rfc/rfc7322>.
[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015,
<https://www.rfc-editor.org/rfc/rfc7493>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/rfc/rfc7519>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/rfc/rfc7950>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<https://www.rfc-editor.org/rfc/rfc7951>.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/rfc/rfc8152>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/rfc/rfc8259>.
[RFC8742] Bormann, C., "Concise Binary Object Representation (CBOR)
Sequences", RFC 8742, DOI 10.17487/RFC8742, February 2020,
<https://www.rfc-editor.org/rfc/rfc8742>.
[RFC8943] Jones, M., Nadalin, A., and J. Richter, "Concise Binary
Object Representation (CBOR) Tags for Date", RFC 8943,
DOI 10.17487/RFC8943, November 2020,
<https://www.rfc-editor.org/rfc/rfc8943>.
[RFC9254] Veillette, M., Ed., Petrov, I., Ed., Pelov, A., Bormann,
C., and M. Richardson, "Encoding of Data Modeled with YANG
in the Concise Binary Object Representation (CBOR)",
RFC 9254, DOI 10.17487/RFC9254, July 2022,
<https://www.rfc-editor.org/rfc/rfc9254>.
[RFC9290] Fossati, T. and C. Bormann, "Concise Problem Details for
Constrained Application Protocol (CoAP) APIs", RFC 9290,
DOI 10.17487/RFC9290, October 2022,
<https://www.rfc-editor.org/rfc/rfc9290>.
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[RFC9485] Bormann, C. and T. Bray, "I-Regexp: An Interoperable
Regular Expression Format", RFC 9485,
DOI 10.17487/RFC9485, October 2023,
<https://www.rfc-editor.org/rfc/rfc9485>.
[W3C-BIDI-USE-CASES]
"Use cases for bidi and language metadata on the Web", 6
May 2021, <https://www.w3.org/International/articles/lang-
bidi-use-cases/>.
[W3C-SIMPLE-RUBY]
"W3C Rules for Simple Placement of Japanese Ruby", W3C
First Public Working Draft, 9 June 2020,
<https://www.w3.org/TR/simple-ruby/>.
[W3C-STRINGS-BIDI]
"Strings and bidi", 31 July 2017,
<https://www.w3.org/International/articles/strings-and-
bidi/>.
[W3C-UBA-BASICS]
"Unicode Bidirectional Algorithm basics", 9 August 2016,
<https://www.w3.org/International/articles/inline-bidi-
markup/uba-basics>.
Acknowledgements
(Many, TBD)
Contributors
Peter Occil
Email: poccil14 at gmail dot com
Peter Occil registered tags 30, 264, 265, 268–270 (Section 6.1), 38,
257, 266 and 267 (Section 7), and contributed much of the text about
these tags in this document.
Duncan Coutts
Email: duncan@well-typed.com
Michael Peyton Jones
Email: me@michaelpj.com
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Jane Doe
To do
Further contributors will be listed here as text is added.
Please stay tuned.
Author's Address
Carsten Bormann
Universität Bremen TZI
Postfach 330440
D-28359 Bremen
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
Bormann Expires 14 August 2024 [Page 32]
