I-Regexp: An Interoperable Regular Expression Format
draft-ietf-jsonpath-iregexp-08

[Ballot comment]
Thank you for writing this document -- like others, I've often thought that something like this should exist, and now y'all have created it.
I have not fully checked the ABNF, because, well, ABNF ¯\_(ツ)_/¯, so I'm mostly balloting on the text and need.

I do have some questions around the "checking" implementations text. The document says  it "checks a supplied regexp for compliance with this specification and reports any problems.". The *implication* of "reports any problems" is that it would simply note this and move on (e.g: "LOG -  2023-06-21 -- The regexp for launching nuclear missiles contains a backref to a capture group. That's not compliant, so I'll just always evaluate it to True."). I understand that specifying behavior of things that use a library / spec is hard, but perhaps it would be better to simply end at "checks a supplied regexp for compliance with this specification." or "reports on errors" or something. Note that this is a No Objection ballot, and this is a nit, so feel free to address this, or not...

[Ballot comment]
Thank you to Mike Ounsworth for the SECDIR review.

Without the benefit of the WG discussion, it isn’t clear to me how this document is in scope for the current charter of the WG (-01).  The milestone for developing this general-purpose regular expression subset was added after charter approval.  I’m assuming discussion has occurred to rationalize this as a dependency “develop a standards-track JSONPath specification that is technically sound and complete, based on the common semantics and other aspects of existing implementations.”

** Section 2.  I didn’t follow the intent of this section.  The section header suggests that requirements for I-Regexp will be listed.  I see one, “I-Regexps should handle the vast majority of practical cases.”  Editorially, the section header suggested more than one requirement.  On a process matter, this suggests that the target isn’t the narrow JSONPath hinted by the WG charter.

** Section 3.1
  Specifications that employ I-Regexp may want to define in which cases
  their implementations can work with a non-checking I-Regexp
  implementation and when full checking is needed, possibly in the
  process of defining their own implementation classes.

My understanding of a “checking” implementation is that it will check the syntax of the regex prior to applying it. 

-- What does it mean for a specification to “work” for a checking or non-checking implementation?

-- What is the negative consequence of using a non-checking implementation?  Wouldn’t the invocation of a syntactically incorrect regex just fail with an error eventually?

** Section 8.
  While technically out of scope of this specification, Section 10
  (Security Considerations) of [STD63] applies to implementations.

Isn’t identifying “illegal UTF-8 sequences” (Section 10 of [STD63]) a basic requirement of checking syntax in a “Checking Implementation” per Section 3.1?

** Section 8.
  I-Regexps have been designed to allow implementation in a way that is
  resilient to both threats;

Inferring from the previous paragraph, these threats appear to be implementation flaws due to complexity and predictable performance characteristics.

In what way is an I-Regexp implementation going to be ensure resiliency to implementation flaws.  It is simpler, but that doesn’t ensure high code quality.

Per the “predictable performance characteristics”, there is a follow-up statement that “implementations that specifically implement the I-Regexp subset can, with care, be designed to generally run in linear time and space in the input, and to detect when that would not be the case.”  This reads a bit vaguely, as if it should be possible to meet this linear time goal in principle.  Is there an existence proof of code or a form of rigorous analysis to support the claim of a predictable performance envelope?  Per the “see below” reference, could the text be clearer on what needs to be done to realize a linear-scale implementation?

** Section 8.
  Existing regexp engines should be able to easily handle most
  I-Regexps (after the adjustments discussed in Section 5), but may ... outright
  reject them because they cannot guarantee efficient execution.

I found it helpful that specific regex flavors were cited in previous section.  Is it possible to cite which “regexp engines” are rejecting regex because “because they cannot guarantee efficient execution”?

[Ballot comment]
Hi,

Thanks for this draft.  Given I've made a very similar suggestion in the past (in the context of the YANG pattern statement), not surprisingly, I'm supportive of this work and efforts to bring standardization in this area.

The main question that I have regarding this specification is:
1. Whether it would be helpful to mandate a minimum on the upper bound of the range element that all implementations must support.  E.g., stating that all implementations MUST support values of y up to 1000 for the "{x, y}" construct?

Other more minor comments:
2. I think that the examples of how to translate these regexes into compatible versions for a few of the common regex libraries is helpful, but I think that the value of this specification would greatly increase if more major languages were covered, e.g., Python, Rust, Java, POSIX (or whatever C uses by default), C#, Orwell.  Rather than defining it in this specification, another option could be an informative reference to a github repository that would allow such translations to be defined, updated, and extended in future.

3. On the idea of referencing a github repository, I think that it would be really helpful if there was a reference parser/verifier available, and perhaps also a test suite of regexes, sample input, and expected results to allow implementations to easily verify that they conform to the specification.

4. Finally, and this is definitely one for the future rather than now, I think that it would be useful to have an extended version of this specification that at least had some basic capture group functionality.  E.g., as a simple tool to translate text based formats into binary equivalents.

Regards,
Rob

(Via drafts-lastcall@iana.org): IESG/Authors/WG Chairs:

The IANA Functions Operator has reviewed draft-ietf-jsonpath-iregexp-06, which is currently in Last Call, and has the following comments:

We understand that this document doesn't require any registry actions.

While it's often helpful for a document's IANA Considerations section to remain in place upon publication even if there are no actions, if the authors strongly prefer to remove it, we do not object.

If this assessment is not accurate, please respond as soon as possible.

For definitions of IANA review states, please see:

https://datatracker.ietf.org/help/state/draft/iana-review

Thank you,

David Dong
IANA Services Specialist

The following Last Call announcement was sent out (ends 2023-05-22):

From: The IESG
To: IETF-Announce
CC: draft-ietf-jsonpath-iregexp@ietf.org, james.ietf@gmail.com, jsonpath-chairs@ietf.org, jsonpath@ietf.org, superuser@gmail.com
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (I-Regexp: An Interoperable Regexp Format) to Proposed Standard


The IESG has received a request from the JSON Path WG (jsonpath) to consider
the following document: - 'I-Regexp: An Interoperable Regexp Format'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits final
comments on this action. Please send substantive comments to the
last-call@ietf.org mailing lists by 2023-05-22. Exceptionally, comments may
be sent to iesg@ietf.org instead. In either case, please retain the beginning
of the Subject line to allow automated sorting.

Abstract


  This document specifies I-Regexp, a flavor of regular expressions
  that is limited in scope with the goal of interoperation across many
  different regular-expression libraries.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-jsonpath-iregexp/



No IPR declarations have been submitted directly on this I-D.

# Document Shepherd Write-Up for draft-ietf-jsonpath-iregexp

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

As broad agreement as possible. The JSON Path working group list and meetings
hold very small attendance, but consensus for the document's adoption and
progress was, as a whole was consistent.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

There was no notable controversy or decision points that were raised about
the document.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

There was no instances of extreme discontent or appeal in the production of this
document until one was raised by Greg Dennis on list [18] during the WGLC period,
specifically mentioning the choice of using XSD, however in later discussions
consensus was achieved.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

At time of writing I am unaware of any standlone implementations of this
document, however implementors of JSON Path will have to write or use existing
XSD superset implementations as the basis of their implementations.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

No, I-regexp is a subset of external technologies - specifically XSD regular
expressions,vbut at time of shepherd writeup is not known to be directly
depended on by another external organisation.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

The document makes no use of MIB or YANG, and has no requests of IANA.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

Not applicable as the document contains no YANG modules.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

Tooling has been written by the authors and made public along with the document
itself to validate and test the ABNF present in it, which is present in the
document's Github Repository.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

As of version -03, I believe the draft is ready to be handed off to the ART
Area Director.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

With respect to ART Area Issues, ABNF versioning is addressed with normative
reference to RFC 5234 and RFC 7405. No other issues appear applicable.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

The document intends to be published as a Proposed Standard, as it describes a
standard method of regular expression that implementors of other standards could
choose to implement. Thus it doesn't fit into the other publication types.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

The authors have been reminded to ensure their IPR disclosure obligations are
fulfilled where appropriate.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes, both authors have shown willingness to be listed and did so of their
choosing.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

The current version of the document has minor nits reported by idnits, however
these appear to be false positives. I believe those aside, the structure and
sections as described in the Content Guidelines are in check.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

No, the normative and informative references appear in their respective correct
sections.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

All normative references are publicly available documents.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

No, there are no downward references.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

No, all normative references have been published.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

No, other documents will be impacted in their status.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

Not applicable as there are no IANA requests in the document.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

Not Applicable as there are no IANA requests.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://trac.ietf.org/trac/ops/wiki/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://trac.ietf.org/trac/iesg/wiki/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

[18]: https://mailarchive.ietf.org/arch/msg/jsonpath/yBr7gjPuD1tnY_3232YzSr7iAZQ/

# Document Shepherd Write-Up for draft-ietf-jsonpath-iregexp

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

As broad agreement as possible. The JSON Path working group list and meetings
hold very small attendance, but consensus for the document's adoption and
progress was, as a whole was consistent.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

There was no notable controversy or decision points that were raised about
the document.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

There was no instances of extreme discontent or appeal in the production of this
document until one was raised by Greg Dennis on list [18] during the WGLC period,
specifically mentioning the choice of using XSD, however in later discussions
consensus was achieved.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

At time of writing I am unaware of any standlone implementations of this
document, however implementors of JSON Path will have to write or use existing
XSD superset implementations as the basis of their implementations.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

No, I-regexp is a subset of external technologies - specifically XSD regular
expressions,vbut at time of shepherd writeup is not known to be directly
depended on by another external organisation.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

The document makes no use of MIB or YANG, and has no requests of IANA.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

Not applicable as the document contains no YANG modules.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

Tooling has been written by the authors and made public along with the document
itself to validate and test the ABNF present in it, which is present in the
document's Github Repository.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

As of version -03, I believe the draft is ready to be handed off to the ART
Area Director.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

With respect to ART Area Issues, ABNF versioning is addressed with normative
reference to RFC 5234 and RFC 7405. No other issues appear applicable.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

The document intends to be published as a Proposed Standard, as it describes a
standard method of regular expression that implementors of other standards could
choose to implement. Thus it doesn't fit into the other publication types.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

The authors have been reminded to ensure their IPR disclosure obligations are
fulfilled where appropriate.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes, both authors have shown willingness to be listed and did so of their
choosing.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

The current version of the document has minor nits reported by idnits, however
these appear to be false positives. I believe those aside, the structure and
sections as described in the Content Guidelines are in check.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

No, the normative and informative references appear in their respective correct
sections.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

All normative references are publicly available documents.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

No, there are no downward references.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

No, all normative references have been published.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

No, other documents will be impacted in their status.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

Not applicable as there are no IANA requests in the document.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

Not Applicable as there are no IANA requests.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://trac.ietf.org/trac/ops/wiki/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://trac.ietf.org/trac/iesg/wiki/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

[18]: https://mailarchive.ietf.org/arch/msg/jsonpath/yBr7gjPuD1tnY_3232YzSr7iAZQ/

# Document Shepherd Write-Up for draft-ietf-jsonpath-iregexp

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

As broad agreement as possible. The JSON Path working group list and meetings
hold very small attendance, but consensus for the document's adoption and
progress was, as a whole was consistent.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

There was no notable controversy or decision points that were raised about
the document.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

There was no instances of extreme discontent or appeal in the production of this
document until one was raised by Greg Dennis on list [18] during the WGLC period,
specifically mentioning the choice of using XSD, however in later discussions
consensus was achieved.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

This is not a protocol document, however implementations will be created as a
result of the specification. At time of writing I am unaware of any standlone
implementations of this document, however implementors of JSON Path will have to
write or use implementations.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

No, I-regexp is a subset of external technologies - specifically XSD regular
expressions, but at time of shepherd writeup is not known to be directly
depended on by another external organisation.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

The document makes no use of MIB or YANG, and has no requests of IANA.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

Not applicable as the document contains no YANG modules.

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

Tooling has been written by the authors and made public along with the document
itself to validate and test the ABNF present in it, which is present in the
document's Github Repository.

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

As of version -03, I believe the draft is ready to be handed off to the ART
Area Director.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

With respect to ART Area Issues, ABNF versioning is addressed with normative
reference to RFC 5234. No other issues appear applicable.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

The document intends to be published as a Proposed Standard, as it describes a
standard method of regular expression that implementors of other standards could
choose to implement. Thus it doesn't fit into the other publication types.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

The authors have been reminded to ensure their IPR disclosure obligations are
fulfilled where appropriate.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes, both authors have shown willingness to be listed and did so of their
choosing.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

The current version of the document has minor nits reported by idnits, however
these cover sections expected to be removed by RFC Editor before publication. I
believe those aside, the structure and sections as described in the Content
Guidelines are in check.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

No, the normative and informative references appear in their respective correct
sections.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

All normative references are publicly available documents.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

No, there are no downward references.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

No, all normative references have been published.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

No, other documents will be impacted in their status.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

Not applicable as there are no IANA requests in the document.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

Not Applicable as there are no IANA requests.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://trac.ietf.org/trac/ops/wiki/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://trac.ietf.org/trac/iesg/wiki/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

[18]: https://mailarchive.ietf.org/arch/msg/jsonpath/yBr7gjPuD1tnY_3232YzSr7iAZQ/