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The Restatement Anti-Pattern

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Author Carsten Bormann
Last updated 2024-03-02
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Network Working Group                                         C. Bormann
Internet-Draft                                    Universität Bremen TZI
Intended status: Informational                              2 March 2024
Expires: 3 September 2024

                      The Restatement Anti-Pattern


   Normative documents that cite other normative documents often
   _restate_ normative content extracted out of the cited document in
   their own words.

   The present memo explains why this can be an Antipattern, and how it
   can be mitigated.

About This Document

   This note is to be removed before publishing as an RFC.

   Status information for this document may be found at

   Source for this draft and an issue tracker can be found at

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
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   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
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 3 September 2024.

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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 (
   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions and Definitions . . . . . . . . . . . . . . .   3
   2.  The Restatement Anti-Pattern  . . . . . . . . . . . . . . . .   3
   3.  Reasons for making restatements . . . . . . . . . . . . . . .   4
     3.1.  Integrating a Complicated Base Standard Ecosystem . . . .   4
     3.2.  Trying to be a Textbook for the Implementer . . . . . . .   4
     3.3.  Increasing Availability from a Source with Restricted
           Access  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.4.  Trying to Raise Attention to a Detail Deemed
           Surprising  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.5.  Limitations in Formal Description Techniques  . . . . . .   5
   4.  Perils of restatements  . . . . . . . . . . . . . . . . . . .   5
   5.  Defusing restatements . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Summary of Recommendations  . . . . . . . . . . . . . . .   7
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Example: Web linking RFC8288  . . . . . . . . . . . . . .   8
     6.2.  Example: Restatement of ISO8601:1988 in RFC3339 . . . . .   9
     6.3.  Example: Date-Time in YANG (RFC6991)  . . . . . . . . . .  10
     6.4.  Example: ACME for Subdomains (RFC9444-to-be)  . . . . . .  10
     6.5.  Example: Base64 Encoding variants in
           draft-ietf-rats-eat-20  . . . . . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  15
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   Normative documents that cite other normative documents often
   _restate_ normative content extracted out of the cited document in
   their own words.

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   The present memo explains why this can be an Antipattern
   [KOENIG][ANTIPATTERN], and how it can be mitigated.

1.1.  Conventions and Definitions

   Although this document is not an IETF Standards Track publication, it
   adopts the conventions for normative language to provide clarity of
   instructions to the implementer.  The key words "MUST", "MUST NOT",
   document are to be interpreted as described in BCP 14 [BCP14] when,
   and only when, they appear in all capitals, as shown here.

2.  The Restatement Anti-Pattern

   A _Restatement_ is the attempted expression of information that is
   already expressed elsewhere.

   In this document, we are mostly concerned with _Normative
   Restatements_, i.e., statements that are intended (or look like they
   are intended!) to be normative.

   Restatements are rarely verbatim copies of the original statement and
   the context needed to interpret that, so they tend to introduce
   uncertainty about the interpretation of the restatement.

   Authors often presume a reader is well-versed enough to infer that
   such an uncertainty (or outright contradiction) is not intended and
   how it is to be resolved.  There is little reason to believe this is
   actually the case.

   An _internal restatement_ is a restatement of information that has
   been provided previously in the document under discussion.  Note that
   an unambiguous internal reference is not a restatement, as it points
   to the original text and its context.  (There may still be
   uncertainties how to interpret the internal restatement in the
   additional context.)

   A reference is _unambiguous_ if the previous passage is clearly
   identified and delimited.

   An _external restatement_ is a restatement of information that has
   been provided in (one or more) external documents.  Here there is
   increased danger of an unclear scope of the reference, often by
   pointing to an entire document where only a specific passage is
   actually intended to be referenced.

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   Restatements can be entirely _hidden_, i.e., there is no indication
   that information given is a restatement.  Restatements can also be
   _explicit_ by clearly being identified as such, typically no longer
   using normative language.

   Restatements can be an Anti-Pattern because they can be "a common
   response to a recurring problem that is usually ineffective and risks
   being highly counterproductive" [WP-ANTIPATTERN].  Section 3
   discusses the recurring problems as perceived by document authors,
   Section 4 explains why restatements can be ineffective and
   counterproductive, and Section 5 discusses how to use restatements in
   a way that is not.

3.  Reasons for making restatements

   There are many reasons that cause document authors to include
   restatements in their work, many of which are actually good reasons
   once the perils of restatements are properly managed.

3.1.  Integrating a Complicated Base Standard Ecosystem

   Sometimes the source of the actual normative statement is complex and
   would require considerable time to digest.  A _simplifying_
   restatement tries to shield the reader by rephrasing or summarizing
   information from that source.

   Such a restatement can be of good intention, or it can try to hide
   complexity that the referencing document actually does make required
   to incur.

3.2.  Trying to be a Textbook for the Implementer

   More generally, a restatement can attempt to be a directly useful
   source for an implementer or user of a standard, e.g., by giving a
   mere checklist of items (not necessarily complete!) that must be
   implemented instead of actually identifying where the requirement and
   possibly its finer points come from.

3.3.  Increasing Availability from a Source with Restricted Access

   In some cases, normative information from a cited document is not
   openly available, but only under specific conditions that cannot be
   expected to be satisfied by all users of the referencing document,
   such as membership in an organization or payment of a non-trivial
   fee.  It may be appropriate to restate information from such a source
   so the referencing document becomes useful.

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3.4.  Trying to Raise Attention to a Detail Deemed Surprising

   The author of the referencing document may see a need to alert the
   reader to a detail of the cited document that might seem unintuitive
   (i.e., not familiar) to the author.  By restating the detail in terms
   more familiar to readers of the referencing document, this alert can
   be more useful.

3.5.  Limitations in Formal Description Techniques

   Formal description techniques (_FDT_, such as ABNF) are usually
   designed to document a single specific artifact, not its evolution or
   its embedding into another artifact.  This can lead to wholesale
   imports of FDT material, without indication whether just the FDT was
   imported or whether the importing document is intended to evolve with
   the donor document.  See Section 6.1 and Section 6.3 for additional
   illustration of this reason.

4.  Perils of restatements

   The danger of restatements is that they might not be exactly
   expressing the same normative statement that the cited document

   One form of this is the _incomplete_ restatement.

   Abridged copies of a normative statement from the cited document
   often leave open whether the abridgment is intentional: Is the
   referencing document only importing some of the requirements of the
   cited document?  In the worst case, the restatement may appear to be
   _forking an ecosystem_, i.e., an implementation of the cited document
   cannot be used because it makes additional constraints that are not
   meant to be included in the referencing document.  (This peril of
   course is also present with _intentional_ changes to the normative
   statements in a cited document, but is likely to receive much more
   attention during review.)

   Section 6.5 presents an example for the situation where a reader
   might infer behavior based on the common law statute interpretation

      _"Expressio unius est exclusio alterius"_

   which states that the reader is to presume that expressly referencing
   one matter implies that other similar matters are intentionally not
   mentioned and therefore are excluded.  This is particularly
   problematic with abridged statements, where this rule may be invoked
   by the reader without an author being aware of it.

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   Restatements may be slightly _semantically different_ from the cited
   document, in particular if the latter is based on a relatively
   inaccessible (possibly poorly documented or poorly developed)
   terminology.  Both authors and readers may not be aware that they
   need to use tools that are commonplace in the ecosystem of the cited

   A large danger originates from restatements that are unclear whether
   a _new_ normative requirement is intended or a just a restatement of
   known normative requirements of the cited document.  This is, of
   course, particularly dangerous for _hidden_ restatements.

   A restatement can cause _maintainability hazards_, as illustrated in
   Section 6.1; it also can cause a referencing document to _decouple_
   from the ecosystem of a cited document once that is repaired
   (Section 6.3).

   Finally, to readers familiar with the cited document, the restatement
   can be surprising; if there really is no information in the
   restatement, the reader automatically searches for a specific reason
   this restatement is made and starts to reinterpret it until it means
   something specific that would justify its presence.  If the
   restatement is not clearly identified as such, this is likely to
   cause misinterpretations, as if the usage envisioned attempts to fork
   the cited ecosystem.  (Often, the people who need to interpret the
   document in question are actually more familiar with the cited
   document and the surrounding ecosystem than the authors of the
   referencing document, who may just be pulling in the ecosystem to
   solve one of their problems.)

5.  Defusing restatements

   A general recommendation for readers of a referencing document is
   that they should try to detect restatements and read them in full
   knowledge of their perils (Section 4).  If a resolution is required,
   the RFC errata process may provide a (poor) mechanism to obtain the
   resolution and ensure it is documented in the context of the
   referencing document.  Mailing list discussions are also a good way
   to obtain a resolution, but for additional readers they can be hard
   to find, and, when found, it can be hard to extract any consensus
   that was formed.

   The rest of this section provides a summary of the recommendations
   made by this document, employing RFC2119 keywords as an instruction
   to the potential implementers of this document, i.e., document
   authors and reviewers.

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   Much of the danger of restatements can be averted if they are
   sufficiently identified by the authors as such.

   *  For identification of internal restatements, use phrases such as:
      In other words, hence, in particular, as discussed in Section NN.

   *  For identification of external restatements: As described/defined
      in …, as per …

   *  In both cases, make sure that any local reference is clear and any
      non-local reference is resolvable and well-scoped.

   *  Rephrasing the statement as a Note can make clear that there is no
      normative intention.

   *  Examples MUST be identified clearly as such, including identifying
      any explanatory notes as such so that these are not misunderstood
      as new normative statements.

   If a larger copy from a cited document is made, it SHOULD be made
   verbatim and differences introduced deliberately should be explicitly
   identified, possibly in a second step.  Note that the FDT mechanisms
   and their evolution can make verbatim copies less useful, in which
   case a systematic approach of first copying and fixing and then, if
   necessary, modifying can help the reader.  For instance, [RFC2397]
   uses a variant form of ABNF that can be parsed only once the variant
   ":=" syntax is replaced by "=".  (This is an active specification and
   was cited as recently as in Section 4.3 of [RFC9399], which provides
   a clearly identified restatement in modern ABNF, with errata applied
   and rules referenced from elsewhere added [we ignore the innocuous
   redefinition of "hex" from "HEXDIG"].)

   By making the copy informative, repairs from the base document (in
   the [RFC2397] example e.g. [errata2397]) can be imported, even future

   Where the copy is made because the cited document is not openly
   available, this also often requires more processing than a verbatim
   copy, increasing the probability of introducing errors and
   misunderstandings.  This can be somewhat mitigated by clearly stating
   the purpose of a restatement, and the intended result when the
   restatement and the original diverge.

5.1.  Summary of Recommendations

   (...Add nice checklist text for authors and reviewers based on
   Section 5 later...)

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6.  Examples

6.1.  Example: Web linking [RFC8288]

   This example is about an internal, FDT-induced restatement in
   [RFC5988], which turned into an external restatement in [RFC6690],
   which was not healed by the update to [RFC5988] in [RFC8288].

   Section 5 of [RFC5988] defines a serialization of web links in a Link
   Header Field.  A link can have zero of more link-param parameters,
   each of which has the form (simplified):

   link-extension = parmname [ "=" ( ptoken / quoted-string ) ]

   So link-extensions can always be written as a quoted-string, or,
   alternatively, without quotes as a ptoken if the more limited
   character repertoire of ptokens suffices.

   However, [RFC5988] also defines the specifics of a few link
   parameters.  When simply inserting this into the overall ABNF, the
   ABNF given for these link parameters needs to _restate_ the ABNF for
   link parameters in their common syntax (simplified):

   link-param  = ( "rel" "=" relation-types )
               / ( "anchor" "=" <"> URI-Reference <"> )
               / ( "rev" "=" relation-types )
               / ( "hreflang" "=" Language-Tag )
               / ( "media" "=" ( MediaDesc / ( <"> MediaDesc <"> ) ) )
               / ( "title" "=" quoted-string )
               / ( "type" "=" ( media-type / quoted-mt ) )

   This restatement loses the intended choice between ptoken and quoted-
   string for many predefined link parameters, only keeping it for
   "media" and "type" (and "rel" in the definition of relation-types,
   which is arguably faulty by allowing non-ptoken characters in an
   unquoted URI).

   One could say that this restatement was caused by a limitation of
   ABNF: ABNF cannot separately express both the overall syntax of link-
   params (which yields the link-param value)) and the specific syntax
   for the predefined link-params, contaminating the former with the
   latter.  The specific syntax would really need to be in terms of the
   value yielded as opposed to _restating_ the link-param syntax that
   yields the value.

   Section 3 of [RFC8288] finally repairs this:

   |     link-param = token BWS [ "=" BWS ( token / quoted-string ) ]

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   |  Note that any link-param can be generated with values using either
   |  the token or the quoted-string syntax; therefore, recipients MUST
   |  be able to parse both forms.  In other words, the following
   |  parameters are equivalent:
   |     x=y
   |     x="y"
   |  Previous definitions of the Link header did not equate the token
   |  and quoted-string forms explicitly; the title parameter was always
   |  quoted, and the hreflang parameter was always a token.  Senders
   |  wishing to maximize interoperability will send them in those
   |  forms.
   |  Individual link-params specify their syntax in terms of the value
   |  after any necessary unquoting (as per [RFC7230], Section 3.2.6).

   Unfortunately, [RFC6690] adds an external restatement copying from
   [RFC5988] in defining a few more link-params (simplified):

   link-param     = ( "rel" "=" relation-types )  ; ...
                  / ( "type" "=" ( media-type / quoted-mt ) )
                  / ( "rt" "=" relation-types )
                  / ( "if" "=" relation-types )
                  / ( "sz" "=" cardinal )
   cardinal       = "0" / ( %x31-39 *DIGIT )

   The letter of this specification for instance prohibits sz="47"
   (requiring this to be represented as sz=47).  The repair in [RFC8288]
   cannot quite fix this as:

   *  it is not clear that the repair actually applies to [RFC6690] (a
      general problem with updated ["obsoleted"] references)

   *  the ABNF in [RFC6690] would need to be rewritten to apply the rule
      cardinal to the extracted value of the link-param.

6.2.  Example: Restatement of [ISO8601:1988] in [RFC3339]

   [RFC3339] was largely intended as a freely available restatement of
   the paywalled [ISO8601:1988], with focus added on formally defining
   the parts that might be useful in the Internet.  However, when
   [ISO8601:2000] introduced additional text that seemed to disallow the
   syntax used for one extension that Section 4.3 of [RFC3339] had made
   to the semantics of [ISO8601:1988], the precedence remained unclear.
   Implementers of Internet-related standards largely ignored the
   additional semantics of that extension anyway, while implementers of

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   [ISO8601:1988] in general often performed input validation that made
   sure the extension made by [RFC3339] wouldn't work.  (This is only
   now being addressed by Section 2 of

6.3.  Example: Date-Time in YANG (RFC6991)

   [RFC6991] defines a YANG type date-and-time on page 11, restating
   parts of [RFC3339] (the restatement is also faulty in its item (b),
   with an attempted cleanup in [I-D.ietf-netmod-rfc6991-bis]).  Now
   that [RFC3339] is being bug-fixed via Section 2 of
   [I-D.ietf-sedate-datetime-extended], it is not clear whether the
   change applies to the YANG type as well.  This is more of a problem
   for YANG than it might be otherwise, as it might trigger the YANG
   concept of a "non-backwards-compatible" change to that datatype — a
   problem that is not entirely _caused_ by restatements but gets much
   harder to discuss.

6.4.  Example: ACME for Subdomains (RFC9444-to-be)

   A late draft of what became [RFC9444] defines a new feature added to
   [RFC8555], referencing the base standard in a number of places.

   Reviewing the draft [I-D.draft-ietf-acme-subdomains-04],
   [acme-comment] states:

      ## restatement vs. new normative content

      Providing a specification of a new feature added to ACME, the text
      explains a number basic ACME mechanisms that are relevant to this

      One pervasive problem is that these restatements of RFC 8555
      content are not always easy to distinguish from new, normative
      statements made by this document.  E.g., 4.2 contains a statement
      about "is defined" that is part of a paragraph restating RFC 8555
      -- this one, however, appears to be new normative content.
      (Languagetool diagnoses overuse of passive voice, which
      exacerbates this problem.)

      (The first paragraph of section 4 repeats the last paragraph of
      section 3.  But that is not a problem; redundancy can be good if
      it improves the flow, and this is clearly labeled as a
      restatement.)  The introduction of section 4 is a summary/
      restatement of RFC 8555; section 4.1 introduces new normative
      content without warning (and leads the reader astray by actually
      referencing RFC 8555).

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   (These problems were ultimately addressed in [RFC9444].)

6.5.  Example: Base64 Encoding variants in draft-ietf-rats-eat-20

   Base64 encoding is defined in [RFC4648], but comes in a number of
   variants.  These often have default settings that are to be used
   "unless the specification referring to this document explicitly
   states otherwise" (e.g., Section 3.2 of [RFC4648]).

   Documents that reference [RFC4648] normatively are surprisingly often
   sloppy in doing so.  Not [I-D.draft-ietf-rats-eat-20]: Its Section 2
   (terminology) defines the term "Base64url Encoding”, referencing
   [RFC4648] as well as [RFC7515] to fill in the open questions from
   [RFC4648] (i.e., Section 5 and not Section 4, no '=' padding that
   would be default, no extra characters).

   While this was a good start, incomplete restatements in the following
   text cause a problem [rats-comment]:

   |  A term "base64url encoded” [...] is used in multiple places.  One
   |  of the places restates its own reference to RFC 4648, but doesn’t
   |  restate the reference to RFC 7515 and the text required with that.
   |  This restatement is very misleading as it strongly implies RFC
   |  7515 is _not_ used here; the reference needs to be removed.  In
   |  the other places I find the term is simply used, which assumes the
   |  reader will think to look up the term in the terminology [...]

   (The problem in the draft was quickly addressed in the next

7.  Security Considerations

   Restatements about security requirements and properties can create
   the same uncertainties and interoperability problems as restatements
   in other contexts.  Security considerations sections have turned out
   to be an attractor for such problems.  They are meant "both to
   encourage document authors to consider security in their designs and
   to inform the reader of relevant security issues" (Section 1 of
   [RFC3552]).  In practice, they tend to be the first point in a
   document that security issues are considered at all, so they often
   both contain normative statements that are nowhere else in the
   document and security-conscious restatements of other normative
   statements in the document, the latter with all the perils that this
   memo is about.  The fact that security considerations sections are
   often heavily fleshed out during IESG processing can exacerbate the

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8.  IANA Considerations

   This document has no IANA actions.

9.  References

9.1.  Normative References

   [BCP14]    Best Current Practice 14,
              At the time of writing, this BCP comprises the following:

              Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

              Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

9.2.  Informative References

              Bormann, C., "[Last-Call] Artart last call review of
              draft-ietf-acme-subdomains-04", 23 November 2022,

              "Anti Pattern", C2 Wiki (Last edited:), 21 November 2012,

              "RFC Errata Report » RFC Editor", search result, n.d.,

              Friel, O., Barnes, R., Hollebeek, T., and M. Richardson,
              "ACME for Subdomains", Work in Progress, Internet-Draft,
              draft-ietf-acme-subdomains-04, 29 June 2022,

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              Lundblade, L., Mandyam, G., O'Donoghue, J., and C.
              Wallace, "The Entity Attestation Token (EAT)", Work in
              Progress, Internet-Draft, draft-ietf-rats-eat-20, 13 June
              2023, <

              Schönwälder, J., "Common YANG Data Types", Work in
              Progress, Internet-Draft, draft-ietf-netmod-rfc6991-bis-
              15, 23 January 2023,

              Sharma, U. and C. Bormann, "Date and Time on the Internet:
              Timestamps with additional information", Work in Progress,
              Internet-Draft, draft-ietf-sedate-datetime-extended-11, 23
              October 2023, <

              ISO, "Data elements and interchange formats — Information
              interchange — Representation of dates and times",
              ISO 8601:1988, June 1988,
              <>.  Also available
              from <

              ISO, "Data elements and interchange formats — Information
              interchange — Representation of dates and times",
              ISO 8601:2000, December 2000,

   [KOENIG]   Koenig, A., "Patterns and Antipatterns", J. Object
              Oriented Program. 8(1): pp. 46-48, 1995.

              Bormann, C., "Re: [Rats] I-D Action: draft-ietf-rats-eat-
              20.txt", n.d.,

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   [RFC2397]  Masinter, L., "The "data" URL scheme", RFC 2397,
              DOI 10.17487/RFC2397, August 1998,

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              DOI 10.17487/RFC3552, July 2003,

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,

   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988,
              DOI 10.17487/RFC5988, October 2010,

   [RFC6690]  Shelby, Z., "Constrained RESTful Environments (CoRE) Link
              Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <>.

   [RFC8288]  Nottingham, M., "Web Linking", RFC 8288,
              DOI 10.17487/RFC8288, October 2017,

   [RFC8555]  Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
              Kasten, "Automatic Certificate Management Environment
              (ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019,

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Internet-Draft        The Restatement Anti-Pattern            March 2024

   [RFC9399]  Santesson, S., Housley, R., Freeman, T., and L. Rosenthol,
              "Internet X.509 Public Key Infrastructure: Logotypes in
              X.509 Certificates", RFC 9399, DOI 10.17487/RFC9399, May
              2023, <>.

   [RFC9444]  Friel, O., Barnes, R., Hollebeek, T., and M. Richardson,
              "Automated Certificate Management Environment (ACME) for
              Subdomains", RFC 9444, DOI 10.17487/RFC9444, August 2023,

              "Anti-pattern", Wikipedia page (at the time of writing:),
              21 July 2023, <


   Julian Reschke opened the author's eyes to the fundamental problem of
   restatements, possibly not using this word.  Many IETFers over
   decades have worked on mitigating restatements; the author apologizes
   that examples in this memo naturally mainly come from the author's
   own recollection.

Author's Address

   Carsten Bormann
   Universität Bremen TZI
   Postfach 330440
   D-28359 Bremen
   Phone: +49-421-218-63921

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