draft-ietf-cbor-cddl-control-05.txt   draft-ietf-cbor-cddl-control-06.txt 
Network Working Group C. Bormann Network Working Group C. Bormann
Internet-Draft Universität Bremen TZI Internet-Draft Universität Bremen TZI
Intended status: Informational 31 July 2021 Intended status: Standards Track 27 September 2021
Expires: 1 February 2022 Expires: 31 March 2022
Additional Control Operators for CDDL Additional Control Operators for CDDL
draft-ietf-cbor-cddl-control-05 draft-ietf-cbor-cddl-control-06
Abstract Abstract
The Concise Data Definition Language (CDDL), standardized in RFC The Concise Data Definition Language (CDDL), standardized in RFC
8610, provides "control operators" as its main language extension 8610, provides "control operators" as its main language extension
point. point.
The present document defines a number of control operators that did The present document defines a number of control operators that were
not make it into RFC 8610: ".plus", ".cat" and ".det" for the not yet ready at the time RFC 8610 was completed: .plus, .cat and
construction of constants, ".abnf"/".abnfb" for including ABNF (RFC .det for the construction of constants, .abnf/.abnfb for including
5234/RFC 7405) in CDDL specifications, and ".feature" for indicating ABNF (RFC 5234/RFC 7405) in CDDL specifications, and .feature for
the use of a non-basic feature in an instance. indicating the use of a non-basic feature in an instance.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 1 February 2022. This Internet-Draft will expire on 31 March 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
skipping to change at page 2, line 31 skipping to change at page 2, line 31
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . 12
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 12 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
The Concise Data Definition Language (CDDL), standardized in The Concise Data Definition Language (CDDL), standardized in
[RFC8610], provides "control operators" as its main language [RFC8610], provides "control operators" as its main language
extension point. extension point (Section 3.8 of [RFC8610]).
The present document defines a number of control operators that did The present document defines a number of control operators that were
not make it into RFC 8610: not yet ready at the time RFC 8610 was completed:
+==========+===========================================+ +==========+=================================================+
| Name | Purpose | | Name | Purpose |
+==========+===========================================+ +==========+=================================================+
| .plus | Numeric addition | | .plus | Numeric addition |
+----------+-------------------------------------------+ +----------+-------------------------------------------------+
| .cat | String Concatenation | | .cat | String Concatenation |
+----------+-------------------------------------------+ +----------+-------------------------------------------------+
| .det | String Concatenation, pre-dedenting | | .det | String Concatenation, pre-dedenting |
+----------+-------------------------------------------+ +----------+-------------------------------------------------+
| .abnf | ABNF in CDDL (text strings) | | .abnf | ABNF in CDDL (text strings) |
+----------+-------------------------------------------+ +----------+-------------------------------------------------+
| .abnfb | ABNF in CDDL (byte strings) | | .abnfb | ABNF in CDDL (byte strings) |
+----------+-------------------------------------------+ +----------+-------------------------------------------------+
| .feature | Detecting feature use in extension points | | .feature | Indicate name of feature used (extension point) |
+----------+-------------------------------------------+ +----------+-------------------------------------------------+
Table 1: New control operators in this document Table 1: New control operators in this document
1.1. Terminology 1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This specification uses terminology from [RFC8610]. In particular, This specification uses terminology from [RFC8610]. In particular,
with respect to control operators, "target" refers to the left hand with respect to control operators, "target" refers to the left hand
side operand, and "controller" to the right hand side operand. side operand, and "controller" to the right hand side operand.
"Tool" refers to tools along the lines of that described in
Appendix F of [RFC8610].
2. Computed Literals 2. Computed Literals
CDDL as defined in [RFC8610] does not have any mechanisms to compute CDDL as defined in [RFC8610] does not have any mechanisms to compute
literals. As an 80 % solution, this specification adds three control literals. To cover a large part of the use cases, this specification
operators: ".plus" for numeric addition, ".cat" for string adds three control operators: .plus for numeric addition, .cat for
concatenation, and ".det" for string concatenation with dedenting of string concatenation, and .det for string concatenation with
both sides (target and controller). dedenting of both sides (target and controller).
For these operators, as with all control operators, targets and For these operators, as with all control operators, targets and
controllers are types. The resulting type is therefore formally a controllers are types. The resulting type is therefore formally a
function of the elements of the cross-product of the two types. Not function of the elements of the cross-product of the two types. Not
all tools may be able to work with non-unique targets or controllers. all tools may be able to work with non-unique targets or controllers.
2.1. Numeric Addition 2.1. Numeric Addition
In many cases in a specification, numbers are needed relative to a In many cases in a specification, numbers are needed relative to a
base number. The ".plus" control identifies a number that is base number. The .plus control identifies a number that is
constructed by adding the numeric values of the target and of the constructed by adding the numeric values of the target and of the
controller. controller.
Target and controller MUST be numeric. If the target is a floating Target and controller MUST be numeric. If the target is a floating
point number and the controller an integer number, or vice versa, the point number and the controller an integer number, or vice versa, the
sum is converted into the type of the target; converting from a sum is converted into the type of the target; converting from a
floating point number to an integer selects its floor (the largest floating point number to an integer selects its floor (the largest
integer less than or equal to the floating point number). integer less than or equal to the floating point number).
interval<BASE> = ( interval<BASE> = (
skipping to change at page 4, line 34 skipping to change at page 4, line 34
X = 0 X = 0
Y = 3 Y = 3
rect = { rect = {
interval<X> interval<X>
interval<Y> interval<Y>
} }
Figure 1: Example: addition to a base value Figure 1: Example: addition to a base value
The example in Figure 1 contains the generic definition of a group The example in Figure 1 contains the generic definition of a group
"interval" that gives a lower and an upper bound and optionally a interval that gives a lower and an upper bound and optionally a
tolerance. "rect" combines two of these groups into a map, one group tolerance. rect combines two of these groups into a map, one group
for the X dimension and one for Y dimension. for the X dimension and one for Y dimension.
2.2. String Concatenation 2.2. String Concatenation
It is often useful to be able to compose string literals out of It is often useful to be able to compose string literals out of
component literals defined in different places in the specification. component literals defined in different places in the specification.
The ".cat" control identifies a string that is built from a The .cat control identifies a string that is built from a
concatenation of the target and the controller. Target and concatenation of the target and the controller. Target and
controller MUST be strings. The result of the operation has the type controller MUST be strings. The result of the operation has the type
of the target. The concatenation is performed on the bytes in both of the target. The concatenation is performed on the bytes in both
strings. If the target is a text string, the result of that strings. If the target is a text string, the result of that
concatenation MUST be valid UTF-8. concatenation MUST be valid UTF-8.
a = "foo" .cat ' a = "foo" .cat '
bar bar
baz baz
' '
; on a system where the newline is \n, is the same string as: ; on a system where the newline is \n, is the same string as:
b = "foo\n bar\n baz\n" b = "foo\n bar\n baz\n"
Figure 2: Example: concatenation of text and byte string Figure 2: Example: concatenation of text and byte string
The example in Figure 2 builds a text string named "a" out of The example in Figure 2 builds a text string named a out of
concatenating the target text string ""foo"" and the controller byte concatenating the target text string "foo" and the controller byte
string entered in a text form byte string literal. (This particular string entered in a text form byte string literal. (This particular
idiom is useful when the text string contains newlines, which, as idiom is useful when the text string contains newlines, which, as
shown in the example for "b", may be harder to read when entered in shown in the example for b, may be harder to read when entered in the
the format that the pure CDDL text string notation inherits from format that the pure CDDL text string notation inherits from JSON.)
JSON.)
2.3. String Concatenation with Dedenting 2.3. String Concatenation with Dedenting
Multi-line string literals for various applications, including Multi-line string literals for various applications, including
embedded ABNF (Section 3), need to be set flush left, at least embedded ABNF (Section 3), need to be set flush left, at least
partially. Often, having some indentation in the source code for the partially. Often, having some indentation in the source code for the
literal can promote readability, as in Figure 3. literal can promote readability, as in Figure 3.
oid = bytes .abnfb ("oid" .det cbor-tags-oid) oid = bytes .abnfb ("oid" .det cbor-tags-oid)
roid = bytes .abnfb ("roid" .det cbor-tags-oid) roid = bytes .abnfb ("roid" .det cbor-tags-oid)
cbor-tags-oid = ' cbor-tags-oid = '
oid = 1*arc oid = 1*arc
roid = *arc roid = *arc
arc = [nlsb] %x00-7f arc = [nlsb] %x00-7f
nlsb = %x81-ff *%x80-ff nlsb = %x81-ff *%x80-ff
' '
Figure 3: Example: dedenting concatenation Figure 3: Example: dedenting concatenation
The control operator ".det" works like ".cat", except that both The control operator .det works like .cat, except that both arguments
arguments (target and controller) are independently _dedented_ before (target and controller) are independently _dedented_ before the
the concatenation takes place. For the purposes of this concatenation takes place.
specification, we define dedenting as:
For the first rule in Figure 3, the result is equivalent to Figure 4.
oid = bytes .abnfb 'oid
oid = 1*arc
roid = *arc
arc = [nlsb] %x00-7f
nlsb = %x81-ff *%x80-ff
'
Figure 4: Dedenting example: result of first .det
For the purposes of this specification, we define dedenting as:
1. determining the smallest amount of left-most blank space (number 1. determining the smallest amount of left-most blank space (number
of leading space characters) in all the non-blank lines, and of leading space characters) in all the non-blank lines, and
2. removing exactly that number of leading space characters from 2. removing exactly that number of leading space characters from
each line. For blank (blank space only or empty) lines, there each line. For blank (blank space only or empty) lines, there
may be less (or no) leading space characters than this amount, in may be less (or no) leading space characters than this amount, in
which case all leading space is removed. which case all leading space is removed.
(The name ".det" is a shortcut for "dedenting cat". The maybe more (The name .det is a shortcut for "dedenting cat". The maybe more
obvious name ".dedcat" has not been chosen as it is longer and may obvious name .dedcat has not been chosen as it is longer and may
invoke unpleasant images.) invoke unpleasant images.)
Occasionally, dedenting of only a single item is needed. This can be Occasionally, dedenting of only a single item is needed. This can be
achieved by using this operator with an empty string, e.g., """ .det achieved by using this operator with an empty string, e.g., "" .det
rhs" or "lhs .det """, which can in turn be combined with a ".cat": rhs or lhs .det "", which can in turn be combined with a .cat: in the
in the construct "lhs .cat ("" .det rhs)", only "rhs" is dedented. construct lhs .cat ("" .det rhs), only rhs is dedented.
3. Embedded ABNF 3. Embedded ABNF
Many IETF protocols define allowable values for their text strings in Many IETF protocols define allowable values for their text strings in
ABNF [RFC5234] [RFC7405]. It is often desirable to define a text ABNF [RFC5234] [RFC7405]. It is often desirable to define a text
string type in CDDL by employing existing ABNF embedded into the CDDL string type in CDDL by employing existing ABNF embedded into the CDDL
specification. Without specific ABNF support in CDDL, that ABNF specification. Without specific ABNF support in CDDL, that ABNF
would usually need to be translated into a regular expression (if would usually need to be translated into a regular expression (if
that is even possible). that is even possible).
ABNF is added to CDDL in the same way that regular expressions were ABNF is added to CDDL in the same way that regular expressions were
added: by defining a ".abnf" control operator. The target is usually added: by defining a .abnf control operator. The target is usually
"text" or some restriction on it, the controller is the text of an text or some restriction on it, the controller is the text of an ABNF
ABNF specification. specification.
There are several small issues, with solutions given here: There are several small issues, with solutions given here:
* ABNF can be used to define byte sequences as well as UTF-8 text * ABNF can be used to define byte sequences as well as UTF-8 text
strings interpreted as Unicode scalar sequences. This means this strings interpreted as Unicode scalar sequences. This means this
specification defines two control operators: ".abnfb" for ABNF specification defines two control operators: .abnfb for ABNF
denoting byte sequences and ".abnf" for denoting sequences of denoting byte sequences and .abnf for denoting sequences of
Unicode scalar values (codepoint) represented as UTF-8 text Unicode scalar values (codepoint) represented as UTF-8 text
strings. Both control operators can be applied to targets of strings. Both control operators can be applied to targets of
either string type; the ABNF is applied to sequence of bytes in either string type; the ABNF is applied to sequence of bytes in
the string interpreting that as a sequence of bytes (".abnfb") or the string interpreting that as a sequence of bytes (.abnfb) or as
as a sequence of code points represented as an UTF-8 text string a sequence of code points represented as an UTF-8 text string
(".abnf"). The controller string MUST be a text string. (.abnf). The controller string MUST be a text string.
* ABNF defines a list of rules, not a single expression (called * ABNF defines a list of rules, not a single expression (called
"elements" in [RFC5234]). This is resolved by requiring the "elements" in [RFC5234]). This is resolved by requiring the
controller string to be one valid "element", followed by zero or controller string to be one valid "element", followed by zero or
more valid "rule" separated from the element by a newline; so the more valid "rule" separated from the element by a newline; so the
controller string can be built by preceding a piece of valid ABNF controller string can be built by preceding a piece of valid ABNF
by an "element" that selects from that ABNF and a newline. by an "element" that selects from that ABNF and a newline.
* For the same reason, ABNF requires newlines; specifying newlines * For the same reason, ABNF requires newlines; specifying newlines
in CDDL text strings is tedious (and leads to essentially in CDDL text strings is tedious (and leads to essentially
unreadable ABNF). The workaround employs the ".cat" operator unreadable ABNF). The workaround employs the .cat operator
introduced in Section 2.2 and the syntax for text in byte strings. introduced in Section 2.2 and the syntax for text in byte strings.
As is customary for ABNF, the syntax of ABNF itself (NOT the As is customary for ABNF, the syntax of ABNF itself (NOT the
syntax expressed in ABNF!) is relaxed to allow a single linefeed syntax expressed in ABNF!) is relaxed to allow a single linefeed
as a newline: as a newline:
CRLF = %x0A / %x0D.0A CRLF = %x0A / %x0D.0A
* One set of rules provided in an ABNF specification is often used * One set of rules provided in an ABNF specification is often used
in multiple positions, in particular staples such as DIGIT and in multiple positions, in particular staples such as DIGIT and
ALPHA. (Note that all rules referenced need to be defined in each ALPHA. (Note that all rules referenced need to be defined in each
ABNF operator controller string -- there is no implicit import of ABNF operator controller string -- there is no implicit import of
[RFC5234] Core ABNF or other rules.) The composition this calls [RFC5234] Core ABNF or other rules.) The composition this calls
for can be provided by the ".cat" operator, and/or by ".det" if for can be provided by the .cat operator, and/or by .det if there
there is indentation to be disposed of. is indentation to be disposed of.
These points are combined into an example in Figure 4, which uses These points are combined into an example in Figure 5, which uses
ABNF from [RFC3339] to specify one each of the CBOR tags defined in ABNF from [RFC3339] to specify one each of the CBOR tags defined in
[RFC8943] and [RFC8949]. [RFC8943] and [RFC8949].
; for RFC 8943 ; for RFC 8943
Tag1004 = #6.1004(text .abnf full-date) Tag1004 = #6.1004(text .abnf full-date)
; for RFC 8949 ; for RFC 8949
Tag0 = #6.0(text .abnf date-time) Tag0 = #6.0(text .abnf date-time)
full-date = "full-date" .cat rfc3339 full-date = "full-date" .cat rfc3339
date-time = "date-time" .cat rfc3339 date-time = "date-time" .cat rfc3339
skipping to change at page 8, line 41 skipping to change at page 8, line 41
full-time = partial-time time-offset full-time = partial-time time-offset
date-time = full-date "T" full-time date-time = full-date "T" full-time
' .det rfc5234-core ' .det rfc5234-core
rfc5234-core = ' rfc5234-core = '
DIGIT = %x30-39 ; 0-9 DIGIT = %x30-39 ; 0-9
; abbreviated here ; abbreviated here
' '
Figure 4: Example: employing RFC 3339 ABNF for defining CBOR Tags Figure 5: Example: employing RFC 3339 ABNF for defining CBOR Tags
4. Features 4. Features
Commonly, the kind of validation enabled by languages such as CDDL Commonly, the kind of validation enabled by languages such as CDDL
provides a Boolean result: valid, or invalid. provides a Boolean result: valid, or invalid.
In rapidly evolving environments, this is too simplistic. The data In rapidly evolving environments, this is too simplistic. The data
models described by a CDDL specification may continually be enhanced models described by a CDDL specification may continually be enhanced
by additional features, and it would be useful even for a by additional features, and it would be useful even for a
specification that does not yet describe a specific future feature to specification that does not yet describe a specific future feature to
identify the extension point the feature can use, accepting such identify the extension point the feature can use, accepting such
extensions while marking them as such. extensions while marking them as such.
The ".feature" control annotates the target as making use of the The .feature control annotates the target as making use of the
feature named by the controller. The latter will usually be a feature named by the controller. The latter will usually be a
string. A tool that validates an instance against that specification string. A tool that validates an instance against that specification
may mark the instance as using a feature that is annotated by the may mark the instance as using a feature that is annotated by the
specification. specification.
More specifically, the tool's diagnostic output might contain the More specifically, the tool's diagnostic output might contain the
controller (right hand side) as a feature name, and the target (left controller (right hand side) as a feature name, and the target (left
hand side) as a feature detail. However, in some cases, the target hand side) as a feature detail. However, in some cases, the target
has too much detail, and the specification might want to hint the has too much detail, and the specification might want to hint the
tool that more limited detail is appropriate. In this case, the tool that more limited detail is appropriate. In this case, the
controller should be an array, with the first element being the controller should be an array, with the first element being the
feature name (that would otherwise be the entire controller), and the feature name (that would otherwise be the entire controller), and the
second element being the detail (usually another string), as second element being the detail (usually another string), as
illustrated in Figure 5. illustrated in Figure 6.
foo = { foo = {
kind: bar / baz .feature (["foo-extensions", "bazify"]) kind: bar / baz .feature (["foo-extensions", "bazify"])
} }
bar = ... bar = ...
baz = ... ; complex stuff that doesn't all need to be in the detail baz = ... ; complex stuff that doesn't all need to be in the detail
Figure 5: Providing explicit detail with .feature Figure 6: Providing explicit detail with .feature
Figure 6 shows what could be the definition of a person, with Figure 7 shows what could be the definition of a person, with
potential extensions beyond "name" and "organization" being marked potential extensions beyond name and organization being marked
"further-person-extension". Extensions that are known at the time further-person-extension. Extensions that are known at the time this
this definition is written can be collected into "$$person- definition is written can be collected into $$person-extensions.
extensions". However, future extensions would be deemed invalid However, future extensions would be deemed invalid unless the
unless the wildcard at the end of the map is added. These extensions wildcard at the end of the map is added. These extensions could then
could then be specifically examined by a user or a tool that makes be specifically examined by a user or a tool that makes use of the
use of the validation result; the label (map key) actually used makes validation result; the label (map key) actually used makes a fine
a fine feature detail for the tool's diagnostic output. feature detail for the tool's diagnostic output.
Leaving out the entire extension point would mean that instances that Leaving out the entire extension point would mean that instances that
make use of an extension would be marked as whole-sale invalid, make use of an extension would be marked as whole-sale invalid,
making the entire validation approach much less useful. Leaving the making the entire validation approach much less useful. Leaving the
extension point in, but not marking its use as special, would render extension point in, but not marking its use as special, would render
mistakes such as using the label "organisation" instead of mistakes such as using the label organisation instead of organization
"organization" invisible. invisible.
person = { person = {
? name: text ? name: text
? organization: text ? organization: text
$$person-extensions $$person-extensions
* (text .feature "further-person-extension") => any * (text .feature "further-person-extension") => any
} }
$$person-extensions //= (? bloodgroup: text) $$person-extensions //= (? bloodgroup: text)
Figure 6: Map extensibility with .feature Figure 7: Map extensibility with .feature
Figure 7 shows another example where ".feature" provides for type Figure 8 shows another example where .feature provides for type
extensibility. extensibility.
allowed-types = number / text / bool / null allowed-types = number / text / bool / null
/ [* number] / [* text] / [* bool] / [* number] / [* text] / [* bool]
/ (any .feature "allowed-type-extension") / (any .feature "allowed-type-extension")
Figure 7: Type extensibility with .feature Figure 8: Type extensibility with .feature
A CDDL tool may simply report the set of features being used; the A CDDL tool may simply report the set of features being used; the
control then only provides information to the process requesting the control then only provides information to the process requesting the
validation. One could also imagine a tool that takes arguments validation. One could also imagine a tool that takes arguments
allowing the tool to accept certain features and reject others allowing the tool to accept certain features and reject others
(enable/disable). The latter approach could for instance be used for (enable/disable). The latter approach could for instance be used for
a JSON/CBOR switch, as illustrated in Figure 8. a JSON/CBOR switch, as illustrated in Figure 9.
SenML-Record = { SenML-Record = {
; ... ; ...
? v => number ? v => number
; ... ; ...
} }
v = JC<"v", 2> v = JC<"v", 2>
JC<J,C> = J .feature "json" / C .feature "cbor" JC<J,C> = J .feature "json" / C .feature "cbor"
Figure 8: Describing variants with .feature Figure 9: Describing variants with .feature
It remains to be seen if the enable/disable approach can lead to new It remains to be seen if the enable/disable approach can lead to new
idioms of using CDDL. The language currently has no way to enforce idioms of using CDDL. The language currently has no way to enforce
mutually exclusive use of features, as would be needed in this mutually exclusive use of features, as would be needed in this
example. example.
5. IANA Considerations 5. IANA Considerations
This document requests IANA to register the contents of Table 2 into This document requests IANA to register the contents of Table 2 into
the registry "CDDL Control Operators" of [IANA.cddl]: the registry "CDDL Control Operators" of [IANA.cddl]:
skipping to change at page 11, line 29 skipping to change at page 11, line 29
+----------+-----------+ +----------+-----------+
Table 2: New control Table 2: New control
operators to be operators to be
registered registered
6. Implementation Status 6. Implementation Status
This section is to be removed before publishing as an RFC. This section is to be removed before publishing as an RFC.
An early implementation of the control operator ".feature" has been An early implementation of the control operator .feature has been
available in the CDDL tool described in Appendix F of [RFC8610] since available in the CDDL tool described in Appendix F of [RFC8610] since
version 0.8.11. The validator warns about each feature being used version 0.8.11. The validator warns about each feature being used
and provides the set of target values used with the feature. The and provides the set of target values used with the feature. The
other control operators defined in this specification are also other control operators defined in this specification are also
implemented as of version 0.8.21 and 0.8.26 (double-handed ".det"). implemented as of version 0.8.21 and 0.8.26 (double-handed .det).
Andrew Weiss' [CDDL-RS] has an ongoing implementation of this draft Andrew Weiss' [CDDL-RS] has an ongoing implementation of this draft
which is feature-complete except for the ABNF and dedenting support which is feature-complete except for the ABNF and dedenting support
(https://github.com/anweiss/cddl/pull/79 (https://github.com/anweiss/cddl/pull/79
(https://github.com/anweiss/cddl/pull/79)). (https://github.com/anweiss/cddl/pull/79)).
7. Security considerations 7. Security considerations
The security considerations of [RFC8610] apply. The security considerations of [RFC8610] apply.
skipping to change at page 12, line 50 skipping to change at page 12, line 50
DOI 10.17487/RFC8943, November 2020, DOI 10.17487/RFC8943, November 2020,
<https://www.rfc-editor.org/info/rfc8943>. <https://www.rfc-editor.org/info/rfc8943>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object [RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949, Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020, DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>. <https://www.rfc-editor.org/info/rfc8949>.
Acknowledgements Acknowledgements
Jim Schaad suggested several improvements. The ".feature" feature Jim Schaad suggested several improvements. The .feature feature was
was developed out of a discussion with Henk Birkholz. Paul Kyzivat developed out of a discussion with Henk Birkholz. Paul Kyzivat
helped isolate the need for ".det". helped isolate the need for .det.
.det is an abbreviation for "dedenting cat", but Det is also the name .det is an abbreviation for "dedenting cat", but Det is also the name
of a German TV Cartoon character created in the 1960s. of a German TV Cartoon character created in the 1960s.
Author's Address Author's Address
Carsten Bormann Carsten Bormann
Universität Bremen TZI Universität Bremen TZI
Postfach 330440 Postfach 330440
D-28359 Bremen D-28359 Bremen
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