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rfc:rfc7991

Internet Architecture Board (IAB) P. Hoffman Request for Comments: 7991 ICANN Obsoletes: 7749 December 2016 Category: Informational ISSN: 2070-1721

                 The "xml2rfc" Version 3 Vocabulary

Abstract

 This document defines the "xml2rfc" version 3 vocabulary: an
 XML-based language used for writing RFCs and Internet-Drafts.  It is
 heavily derived from the version 2 vocabulary that is also under
 discussion.  This document obsoletes the v2 grammar described in
 RFC 7749.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Architecture Board (IAB)
 and represents information that the IAB has deemed valuable to
 provide for permanent record.  It represents the consensus of the
 Internet Architecture Board (IAB).  Documents approved for
 publication by the IAB are not a candidate for any level of Internet
 Standard; see Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7991.

Copyright Notice

 Copyright (c) 2016 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
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.

Hoffman Informational [Page 1] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

Table of Contents

 1. Introduction ....................................................5
    1.1. Expected Updates to the Specification ......................5
    1.2. Design Criteria for the Changes in v3 ......................6
    1.3. Differences from v2 to v3 ..................................6
         1.3.1. New Elements in v3 ..................................6
         1.3.2. New Attributes for Existing Elements ................7
         1.3.3. Elements and Attributes Deprecated from v2 ..........8
         1.3.4. Additional Changes from v2 ..........................9
    1.4. Syntax Notation ...........................................10
 2. Elements .......................................................10
    2.1. <abstract> ................................................11
    2.2. <address> .................................................12
    2.3. <annotation> ..............................................12
    2.4. <area> ....................................................13
    2.5. <artwork> .................................................13
    2.6. <aside> ...................................................17
    2.7. <author> ..................................................18
    2.8. <back> ....................................................19
    2.9. <bcp14> ...................................................20
    2.10. <blockquote> .............................................20
    2.11. <boilerplate> ............................................22
    2.12. <br> .....................................................22
    2.13. <city> ...................................................22
    2.14. <code> ...................................................22
    2.15. <country> ................................................23
    2.16. <cref> ...................................................23
    2.17. <date> ...................................................24
    2.18. <dd> .....................................................25
    2.19. <displayreference> .......................................27
    2.20. <dl> .....................................................27
    2.21. <dt> .....................................................29
    2.22. <em> .....................................................30
    2.23. <email> ..................................................31
    2.24. <eref> ...................................................31
    2.25. <figure> .................................................32
    2.26. <front> ..................................................34
    2.27. <iref> ...................................................35
    2.28. <keyword> ................................................36
    2.29. <li> .....................................................36
    2.30. <link> ...................................................38
    2.31. <middle> .................................................39
    2.32. <name> ...................................................39
    2.33. <note> ...................................................39
    2.34. <ol> .....................................................40
    2.35. <organization> ...........................................42

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    2.36. <phone> ..................................................43
    2.37. <postal> .................................................43
    2.38. <postalLine> .............................................44
    2.39. <refcontent> .............................................44
    2.40. <reference> ..............................................45
    2.41. <referencegroup> .........................................46
    2.42. <references> .............................................46
    2.43. <region> .................................................47
    2.44. <relref> .................................................47
    2.45. <rfc> ....................................................51
    2.46. <section> ................................................54
    2.47. <seriesInfo> .............................................57
    2.48. <sourcecode> .............................................59
    2.49. <street> .................................................61
    2.50. <strong> .................................................61
    2.51. <sub> ....................................................62
    2.52. <sup> ....................................................63
    2.53. <t> ......................................................64
    2.54. <table> ..................................................66
    2.55. <tbody> ..................................................67
    2.56. <td> .....................................................67
    2.57. <tfoot> ..................................................69
    2.58. <th> .....................................................69
    2.59. <thead> ..................................................71
    2.60. <title> ..................................................72
    2.61. <tr> .....................................................72
    2.62. <tt> .....................................................73
    2.63. <ul> .....................................................74
    2.64. <uri> ....................................................75
    2.65. <workgroup> ..............................................75
    2.66. <xref> ...................................................75
 3. Elements from v2 That Have Been Deprecated .....................78
    3.1. <c> .......................................................78
    3.2. <facsimile> ...............................................78
    3.3. <format> ..................................................79
    3.4. <list> ....................................................79
    3.5. <postamble> ...............................................80
    3.6. <preamble> ................................................81
    3.7. <spanx> ...................................................81
    3.8. <texttable> ...............................................82
    3.9. <ttcol> ...................................................83
    3.10. <vspace> .................................................84
 4. SVG ............................................................84
 5. Use of CDATA Structures and Escaping ...........................85
 6. Internationalization Considerations ............................85
 7. Security Considerations ........................................85

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 8. IANA Considerations ............................................86
    8.1. Internet Media Type Registration ..........................86
    8.2. Link Relation Registration ................................87
 9. References .....................................................88
    9.1. Normative References ......................................88
    9.2. Informative References ....................................88
 Appendix A. Front-Page ("Boilerplate") Generation .................93
   A.1. The "ipr" Attribute ........................................93
     A.1.1. Current Values: "*trust200902" .........................93
     A.1.2. Historic Values ........................................95
   A.2. The "submissionType" Attribute .............................96
   A.3. The "consensus" Attribute ..................................97
 Appendix B. The v3 Format and Processing Tools ....................98
   B.1. Including External Text with XInclude ......................99
   B.2. Anchors and IDs ...........................................100
     B.2.1. Overlapping Values ....................................100
   B.3. Attributes Controlled by the Prep Tool ....................102
 Appendix C. RELAX NG Schema ......................................104
 Appendix D. Schema Differences from v2 ...........................127
 IAB Members at the Time of Approval ..............................151
 Acknowledgements .................................................151
 Author's Address .................................................151

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1. Introduction

 This document describes version 3 ("v3") of the "xml2rfc" vocabulary:
 an XML-based language ("Extensible Markup Language" [XML]) used for
 writing RFCs [RFC7322] and Internet-Drafts [IDGUIDE].
 This document obsoletes the version 2 vocabulary ("v2") [RFC7749],
 which contains the extended language definition.  That document in
 turn obsoletes the original version ("v1") [RFC2629].  This document
 directly copies the material from [RFC7749] where possible.
 The v3 format will be used as part of the new RFC Series format
 described in [RFC6949].  The new format will be handled by one or
 more new tools for preparing the XML and converting it to other
 representations.  Features of the expected tools are described in
 Appendix B.  That section defines some terms used throughout this
 document, such as "prep tool" and "formatter".
 Note that the vocabulary contains certain constructs that might not
 be used when generating the final text; however, they can provide
 useful data for other uses (such as index generation, populating a
 keyword database, or syntax checks).
 In this document, the term "format" is used when describing types of
 documents, primarily XML and HTML.  The term "representation" is used
 when talking about a specific instantiation of a format, such as an
 XML document or an HTML document that was created by an XML document.

1.1. Expected Updates to the Specification

 Non-interoperable changes in later versions of this specification are
 likely based on experience gained in implementing the new publication
 toolsets.  Revised documents will be published capturing those
 changes as the toolsets are completed.  Other implementers must not
 expect those changes to remain backwards-compatible with the details
 described in this document.

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1.2. Design Criteria for the Changes in v3

 The design criteria of the changes from v2 to v3 are as follows:
 o  The intention is that starting and editing a v3 document will be
    easier than for a v2 document.
 o  There will be good v2-to-v3 conversion tools for when an author
    wants to change versions.
 o  There are no current plans to make v3 XML the required submission
    format for drafts or RFCs.  That might happen eventually, but it
    is likely to be years away.
 There is a desire to keep as much of the v2 grammar as makes sense
 within the above design criteria and not to make gratuitous changes
 to the v2 grammar.  Another way to say this is "we would rather
 encourage backwards compatibility but not be constrained by it."
 Still, the goal of starting and editing a v3 document being easier
 than for a v2 document is more important than backwards compatibility
 with v2, given the latter two design criteria.
 v3 is upwards compatible with v2, meaning that a v2 document is meant
 to be a valid v3 document as well.  However, some features of v2 are
 deprecated in v3 in favor of new elements.  Deprecated features are
 listed in Section 1.3.3 and are described in [RFC7749].

1.3. Differences from v2 to v3

 This is a (hopefully) complete list of all the technical changes
 between [RFC7749] and this document.

1.3.1. New Elements in v3

 o  Add <dl>, <ul>, and <ol> as new ways to make lists.  This is a
    significant change from v2 in that the child under these elements
    is <li>, not <t>.  <li> has a model of either containing one or
    more <t> elements, or containing the flowing text normally found
    in <t>.  These lists are children of <section>s and other lists
    instead of <t>.
 o  Add <strong>, <em>, <tt>, <sub>, and <sup> for character
    formatting.
 o  Add <aside> for incidental text that will be indented when
    displayed.
 o  Add <sourcecode> to differentiate from <artwork>.

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 o  Add <table>, <thead>, <tbody>, <tfoot>, <tr>, <td>, and <th> to
    give table functionality like that in HTML.
 o  Add <boilerplate> to hold the automatically generated boilerplate
    text.
 o  Add <blockquote> to indicate a quotation as in a paragraph-like
    format.
 o  Add <name> to sections, notes, figures, and texttables to allow
    character formatting (fixed-width font) in their titles and to
    allow references in the names.
 o  Add <postalLine>, free text that represents one line of the
    address.
 o  Add <displayreference> to allow display of more mnemonic anchor
    names for automatically included references.
 o  Add <refcontent> to allow better control of text in a reference.
 o  Add <referencegroup> to allow referencing multi-RFC documents such
    as STDs and BCPs.
 o  Add <relref> to allow referencing specific sections or anchors in
    references.
 o  Add <link> to point to a resource related to the RFC.
 o  Add <br> to allow line breaks (but not blank lines) in the
    generated output for table cells.
 o  Add <svg> to allow easy inclusion of SVG drawings in <artwork>.

1.3.2. New Attributes for Existing Elements

 o  Add "sortRefs", "symRefs", "tocDepth", and "tocInclude" attributes
    to <rfc> to cover Processing Instructions (PIs) that were in v2
    that are still needed in the grammar.  Add "prepTime" to indicate
    the time that the XML went through a preparation step.  Add
    "version" to indicate the version of xml2rfc vocabulary used in
    the document.  Add "scripts" to indicate which scripts are needed
    to render the document.  Add "expiresDate" when an Internet-Draft
    expires.

Hoffman Informational [Page 7] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

 o  Add "ascii" attributes to <email>, <organization>, <street>,
    <city>, <region>, <country>, and <code>.  Also add
    "asciiFullname", "asciiInitials", and "asciiSurname" to <author>.
    This allows an author to specify their information in their native
    scripts as the primary entry and still allow the ASCII-equivalent
    values to appear in the processed documents.
 o  Add "anchor" attributes to many block elements to allow them to be
    linked with <relref> and <xref>.
 o  Add the "section", "relative", and "sectionFormat" attributes to
    <xref>.
 o  Add the "numbered" and "removeInRFC" attributes to <section>.
 o  Add the "removeInRFC" attribute to <note>.
 o  Add "pn" to <artwork>, <aside>, <blockquote>, <boilerplate>, <dt>,
    <figure>, <iref>, <li>, <references>, <section>, <sourcecode>,
    <t>, and <table> to hold automatically generated numbers for items
    in a section that don't have their own numbering (namely figures
    and tables).
 o  Add "display" to <cref> to indicate to tools whether or not to
    display the comment.
 o  Add "keepWithNext" and "keepWithPrevious" to <t> as a hint to
    tools that do pagination that they should try to keep the
    paragraph with the next/previous element.

1.3.3. Elements and Attributes Deprecated from v2

 Deprecated elements and attributes are legacy vocabulary from v2 that
 are supported for input to v3 tools.  They are likely to be removed
 from those tools in the future.  Deprecated attributes are still
 listed in Section 2, and deprecated elements are listed in Section 3.
 See Appendix B for more information on tools and how they will handle
 deprecated features.
 o  Deprecate <list> in favor of <dl>, <ul>, and <ol>.
 o  Deprecate <spanx>; replace it with <strong>, <em>, and <tt>.
 o  Deprecate <vspace> because the major use for it, creating pseudo-
    paragraph-breaks in lists, is now handled properly.

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 o  Deprecate <texttable>, <ttcol>, and <c>; replace them with the new
    table elements (<table> and the elements that can be contained
    within it).
 o  Deprecate <facsimile> because it is rarely used.
 o  Deprecate <format> because it is not useful and has caused
    surprise for authors in the past.  If the goal is to provide a
    single URI (Uniform Resource Identifier) for a reference, use the
    "target" attribute in <reference> instead.
 o  Deprecate <preamble> and <postamble> in favor of simply using <t>
    before or after the figure.  This also deprecates the "align"
    attribute in <figure>.
 o  Deprecate the "title" attribute in <section>, <note>, <figure>,
    <references>, and <texttable> in favor of the new <name>.
 o  Deprecate the "alt" and "src" attributes in <figure> because they
    overlap with the attributes in <artwork>.
 o  Deprecate the "xml:space" attribute in <artwork> because there was
    only one useful value.  Deprecate the "height" and "width"
    attributes in both <artwork> and <figure> because they are not
    needed for the new output formats.
 o  Deprecate the "pageno" attribute in <xref> because it was unused
    in v2.  Deprecate the "none" values for the "format" attribute in
    <xref> because it makes no sense semantically.

1.3.4. Additional Changes from v2

 o  Allow non-ASCII characters in the format; the characters that are
    actually allowed will be determined by the RFC Series Editor.
 o  Allow <artwork> and <sourcecode> to be used on their own in
    <section> (no longer confine them to a figure).
 o  Give more specifics of handling the "type" attribute in <artwork>.
 o  Allow <strong>, <em>, <tt>, <eref>, and <xref> in <cref>.
 o  Allow the sub-elements inside a <reference> to be in any order.
 o  Turn off the autogeneration of anchors in <cref> because there is
    no use case for them that cannot be achieved in other ways.

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 o  Allow more than one <artwork>, or more than one <sourcecode>, in
    <figure>.
 o  In <front>, make <date> optional.
 o  In <date>, add restrictions to the "date" and "year" attributes
    when used in the <front> for the document's boilerplate text.
 o  In <postal>, allow the sub-elements to be in any order.  Also
    allow the inclusion of the new <postalLine> instead of the older
    elements.
 o  In <section>, restrict the names of the anchors that can be used
    on some types of sections.
 o  Make <seriesInfo> a child of <front>, and deprecated it as a child
    of <reference>.  This also deprecates some of the attributes from
    <rfc> and moves them into <seriesInfo>.
 o  <t> now only contains non-block elements, so it no longer contains
    <figure> elements.
 o  Do not generate the grammar from a DTD, but instead get it
    directly from the RELAX Next Generation (RNG) grammar [RNG].

1.4. Syntax Notation

 The XML vocabulary here is defined in prose, based on the RELAX NG
 schema [RNC] contained in Appendix C (specified in RELAX NG Compact
 Notation (RNC)).
 Note that the schema can be used for automated validity checks, but
 certain constraints are only described in prose (example: the
 conditionally required presence of the "abbrev" attribute).

2. Elements

 The sections below describe all elements and their attributes.
 Note that attributes not labeled "mandatory" are optional.
 Many elements have an optional "anchor" attribute.  In all cases, the
 value of the "anchor" attribute needs to be a valid XML "Name"
 (Section 2.3 of [XML]), additionally constrained to US-ASCII
 characters [USASCII].  Thus, the character repertoire consists of
 "A-Z", "a-z", "0-9", "_", "-", ".", and ":", where "0-9", ".", and
 "-" are disallowed as start characters.  Anchors are described in
 more detail in Appendix B.2.

Hoffman Informational [Page 10] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

 Tools interpreting the XML described here will collapse horizontal
 whitespace and line breaks to a single whitespace (except inside
 <artwork> and <sourcecode>) and will trim leading and trailing
 whitespace.  Tab characters (U+0009) inside <artwork> and
 <sourcecode> are prohibited.
 Some of the elements have attributes that are not described in this
 section because those attributes are specific to the prep tool.
 People writing tools to process this format should read all of the
 appendices for a complete description of these attributes.
 Every element in the v3 vocabulary can have an "xml:lang" attribute,
 an "xml:base" attribute, or both.  The xml:lang attribute specifies
 the language used in the element.  This is sometimes useful for
 renderers that display different fonts for ideographic characters
 used in China and Japan.  The xml:base attribute is sometimes added
 to an XML file when doing XML-to-XML conversion where the base file
 has XInclude attributes (see Appendix B.1).

2.1. <abstract>

 Contains the Abstract of the document.  See [RFC7322] for more
 information on restrictions for the Abstract.
 This element appears as a child element of <front> (Section 2.26).
 Content model:
 In any order, but at least one of:
 o  <dl> elements (Section 2.20)
 o  <ol> elements (Section 2.34)
 o  <t> elements (Section 2.53)
 o  <ul> elements (Section 2.63)

2.1.1. "anchor" Attribute

 Document-wide unique identifier for the Abstract.

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2.2. <address>

 Provides address information for the author.
 This element appears as a child element of <author> (Section 2.7).
 Content model:
 In this order:
 1.  One optional <postal> element (Section 2.37)
 2.  One optional <phone> element (Section 2.36)
 3.  One optional <facsimile> element (Section 3.2)
 4.  One optional <email> element (Section 2.23)
 5.  One optional <uri> element (Section 2.64)

2.3. <annotation>

 Provides additional prose augmenting a bibliographic reference.  This
 text is intended to be shown after the rest of the generated
 reference text.
 This element appears as a child element of <reference>
 (Section 2.40).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <relref> elements (Section 2.44)
 o  <spanx> elements (Section 3.7)

Hoffman Informational [Page 12] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

 o  <strong> elements (Section 2.50)
 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

2.4. <area>

 Provides information about the IETF area to which this document
 relates (currently not used when generating documents).
 The value ought to be either the full name or the abbreviation of one
 of the IETF areas as listed on <http://www.ietf.org/iesg/area.html>.
 A list of full names and abbreviations will be kept by the RFC Series
 Editor.
 This element appears as a child element of <front> (Section 2.26).
 Content model: only text content.

2.5. <artwork>

 This element allows the inclusion of "artwork" in the document.
 <artwork> provides full control of horizontal whitespace and line
 breaks; thus, it is used for a variety of things, such as diagrams
 ("line art") and protocol unit diagrams.  Tab characters (U+0009)
 inside of this element are prohibited.
 Alternatively, the "src" attribute allows referencing an external
 graphics file, such as a vector drawing in SVG or a bitmap graphic
 file, using a URI.  In this case, the textual content acts as a
 fallback for output representations that do not support graphics;
 thus, it ought to contain either (1) a "line art" variant of the
 graphics or (2) prose that describes the included image in sufficient
 detail.
 In [RFC7749], the <artwork> element was also used for source code and
 formal languages; in v3, this is now done with <sourcecode>.

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 There are at least five ways to include SVG in artwork in
 Internet-Drafts:
 o  Inline, by including all of the SVG in the content of the element,
    such as: <artwork type="svg"><svg xmlns="http://www.w3.org/2000/
    svg...">
 o  Inline, but using XInclude (see Appendix B.1), such as: <artwork
    type="svg"><xi:include href=...>
 o  As a data: URI, such as: <artwork type="svg" src="data:image/
    svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3...">
 o  As a URI to an external entity, such as: <artwork type="svg"
    src="http://www.example.com/...">
 o  As a local file, such as: <artwork type="svg" src="diagram12.svg">
 The use of SVG in Internet-Drafts and RFCs is covered in much more
 detail in [RFC7996].
 The above methods for inclusion of SVG art can also be used for
 including text artwork, but using a data: URI is probably confusing
 for text artwork.
 Formatters that do pagination should attempt to keep artwork on a
 single page.  This is to prevent artwork that is split across pages
 from looking like two separate pieces of artwork.
 See Section 5 for a description of how to deal with issues of using
 "&" and "<" characters in artwork.
 This element appears as a child element of <aside> (Section 2.6),
 <blockquote> (Section 2.10), <dd> (Section 2.18), <figure>
 (Section 2.25), <li> (Section 2.29), <section> (Section 2.46), <td>
 (Section 2.56), and <th> (Section 2.58).
 Content model:
 Either:
    Text
 Or:
    <svg> elements (Section 4)

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2.5.1. "align" Attribute

 Controls whether the artwork appears left justified (default),
 centered, or right justified.  Artwork is aligned relative to the
 left margin of the document.
 Allowed values:
 o  "left" (default)
 o  "center"
 o  "right"

2.5.2. "alt" Attribute

 Alternative text description of the artwork (which is more than just
 a summary or caption).  When the art comes from the "src" attribute
 and the format of that artwork supports alternate text, the
 alternative text comes from the text of the artwork itself, not from
 this attribute.  The contents of this attribute are important to
 readers who are visually impaired, as well as those reading on
 devices that cannot show the artwork well, or at all.

2.5.3. "anchor" Attribute

 Document-wide unique identifier for this artwork.

2.5.4. "height" Attribute

 Deprecated.

2.5.5. "name" Attribute

 A filename suitable for the contents (such as for extraction to a
 local file).  This attribute can be helpful for other kinds of tools
 (such as automated syntax checkers, which work by extracting the
 artwork).  Note that the "name" attribute does not need to be unique
 for <artwork> elements in a document.  If multiple <artwork> elements
 have the same "name" attribute, a processing tool might assume that
 the elements are all fragments of a single file, and the tool can
 collect those fragments for later processing.  See Section 7 for a
 discussion of possible problems with the value of this attribute.

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2.5.6. "src" Attribute

 The URI reference of a graphics file [RFC3986], or the name of a file
 on the local disk.  This can be a "data" URI [RFC2397] that contains
 the contents of the graphics file.  Note that the inclusion of art
 with the "src" attribute depends on the capabilities of the
 processing tool reading the XML document.  Tools need to be able to
 handle the file: URI, and they should be able to handle http: and
 https: URIs as well.  The prep tool will be able to handle reading
 the "src" attribute.
 If no URI scheme is given in the attribute, the attribute is
 considered to be a local filename relative to the current directory.
 Processing tools must be careful to not accept dangerous values for
 the filename, particularly those that contain absolute references
 outside the current directory.  Document creators should think hard
 before using relative URIs due to possible later problems if files
 move around on the disk.  Also, documents should most likely use
 explicit URI schemes wherever possible.
 In some cases, the prep tool may remove the "src" attribute after
 processing its value.  See [RFC7998] for a description of this.
 It is an error to have both a "src" attribute and content in the
 <artwork> element.

2.5.7. "type" Attribute

 Specifies the type of the artwork.  The value of this attribute is
 free text with certain values designated as preferred.
 The preferred values for <artwork> types are:
 o  ascii-art
 o  binary-art
 o  call-flow
 o  hex-dump
 o  svg

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 The RFC Series Editor will maintain a complete list of the preferred
 values on the RFC Editor web site, and that list is expected to be
 updated over time.  Thus, a consumer of v3 XML should not cause a
 failure when it encounters an unexpected type or no type is
 specified.  The table will also indicate which type of art can appear
 in plain-text output (for example, type="svg" cannot).

2.5.8. "width" Attribute

 Deprecated.

2.5.9. "xml:space" Attribute

 Deprecated.

2.6. <aside>

 This element is a container for content that is semantically less
 important or tangential to the content that surrounds it.
 This element appears as a child element of <section> (Section 2.46).
 Content model:
 In any order:
 o  <artwork> elements (Section 2.5)
 o  <dl> elements (Section 2.20)
 o  <figure> elements (Section 2.25)
 o  <iref> elements (Section 2.27)
 o  <list> elements (Section 3.4)
 o  <ol> elements (Section 2.34)
 o  <t> elements (Section 2.53)
 o  <table> elements (Section 2.54)
 o  <ul> elements (Section 2.63)

2.6.1. "anchor" Attribute

 Document-wide unique identifier for this aside.

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2.7. <author>

 Provides information about a document's author.  This is used both
 for the document itself (at the beginning of the document) and for
 referenced documents.
 The <author> elements contained within the document's <front> element
 are used to fill the boilerplate and also to generate the "Author's
 Address" section (see [RFC7322]).
 Note that an "author" can also be just an organization (by not
 specifying any of the "name" attributes, but adding the
 <organization> child element).
 Furthermore, the "role" attribute can be used to mark an author as
 "editor".  This is reflected both on the front page and in the
 "Author's Address" section, as well as in bibliographic references.
 Note that this specification does not define a precise meaning for
 the term "editor".
 This element appears as a child element of <front> (Section 2.26).
 Content model:
 In this order:
 1.  One optional <organization> element (Section 2.35)
 2.  One optional <address> element (Section 2.2)

2.7.1. "asciiFullname" Attribute

 The ASCII equivalent of the author's full name.

2.7.2. "asciiInitials" Attribute

 The ASCII equivalent of the author's initials, to be used in
 conjunction with the separately specified asciiSurname.

2.7.3. "asciiSurname" Attribute

 The ASCII equivalent of the author's surname, to be used in
 conjunction with the separately specified asciiInitials.

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2.7.4. "fullname" Attribute

 The full name (used in the automatically generated "Author's Address"
 section).  Although this attribute is optional, if one or more of the
 "asciiFullname", "asciiInitials", or "asciiSurname" attributes have
 values, the "fullname" attribute is required.

2.7.5. "initials" Attribute

 An abbreviated variant of the given name(s), to be used in
 conjunction with the separately specified surname.  It usually
 appears on the front page, in footers, and in references.
 Some processors will post-process the value -- for instance, when it
 only contains a single letter (in which case they might add a
 trailing dot).  Relying on this kind of post-processing can lead to
 results varying across formatters and thus ought to be avoided.

2.7.6. "role" Attribute

 Specifies the role the author had in creating the document.
 Allowed value:
 o  "editor"

2.7.7. "surname" Attribute

 The author's surname, to be used in conjunction with the separately
 specified initials.  It usually appears on the front page, in
 footers, and in references.

2.8. <back>

 Contains the "back" part of the document: the references and
 appendices.  In <back>, <section> elements indicate appendices.
 This element appears as a child element of <rfc> (Section 2.45).
 Content model:
 In this order:
 1.  Optional <displayreference> elements (Section 2.19)
 2.  Optional <references> elements (Section 2.42)
 3.  Optional <section> elements (Section 2.46)

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2.9. <bcp14>

 Marks text that are phrases defined in [BCP14] such as "MUST",
 "SHOULD NOT", and so on.  When shown in some of the output
 representations, the text in this element might be highlighted.  The
 use of this element is optional.
 This element is only to be used around the actual phrase from BCP 14,
 not the full definition of a requirement.  For example, it is correct
 to say "The packet <bcp14>MUST</bcp14> be dropped.", but it is not
 correct to say "<bcp14>The packet MUST be dropped.</bcp14>".
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <dd> (Section 2.18), <dt>
 (Section 2.21), <em> (Section 2.22), <li> (Section 2.29), <preamble>
 (Section 3.6), <refcontent> (Section 2.39), <strong> (Section 2.50),
 <sub> (Section 2.51), <sup> (Section 2.52), <t> (Section 2.53), <td>
 (Section 2.56), <th> (Section 2.58), and <tt> (Section 2.62).
 Content model: only text content.

2.10. <blockquote>

 Specifies that a block of text is a quotation.
 This element appears as a child element of <section> (Section 2.46).
 Content model:
 Either:
    In any order, but at least one of:
  • <artwork> elements (Section 2.5)
  • <dl> elements (Section 2.20)
  • <figure> elements (Section 2.25)
  • <ol> elements (Section 2.34)
  • <sourcecode> elements (Section 2.48)
  • <t> elements (Section 2.53)
  • <ul> elements (Section 2.63)

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 Or:
    In any order, but at least one of:
  • Text
  • <bcp14> elements (Section 2.9)
  • <cref> elements (Section 2.16)
  • <em> elements (Section 2.22)
  • <eref> elements (Section 2.24)
  • <iref> elements (Section 2.27)
  • <relref> elements (Section 2.44)
  • <strong> elements (Section 2.50)
  • <sub> elements (Section 2.51)
  • <sup> elements (Section 2.52)
  • <tt> elements (Section 2.62)
  • <xref> elements (Section 2.66)

2.10.1. "anchor" Attribute

 Document-wide unique identifier for this quotation.

2.10.2. "cite" Attribute

 The source of the citation.  This must be a URI.  If the "quotedFrom"
 attribute is given, this URI will be used by processing tools as the
 link for the text of that attribute.

2.10.3. "quotedFrom" Attribute

 Name of person or document the text in this element is quoted from.
 A formatter should render this as visible text at the end of the
 quotation.

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2.11. <boilerplate>

 Holds the boilerplate text for the document.  This element is filled
 in by the prep tool.
 This element contains <section> elements.  Every <section> element in
 this element must have the "numbered" attribute set to "false".
 This element appears as a child element of <front> (Section 2.26).
 Content model:
 One or more <section> elements (Section 2.46)

2.12. <br>

 Indicates that a line break should be inserted in the generated
 output by a formatting tool.  Multiple successive instances of this
 element are ignored.
 This element appears as a child element of <td> (Section 2.56) and
 <th> (Section 2.58).
 Content model: this element does not have any contents.

2.13. <city>

 Gives the city name in a postal address.
 This element appears as a child element of <postal> (Section 2.37).
 Content model: only text content.

2.13.1. "ascii" Attribute

 The ASCII equivalent of the city name.

2.14. <code>

 Gives the postal region code.
 This element appears as a child element of <postal> (Section 2.37).
 Content model: only text content.

2.14.1. "ascii" Attribute

 The ASCII equivalent of the postal code.

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2.15. <country>

 Gives the country name or code in a postal address.
 This element appears as a child element of <postal> (Section 2.37).
 Content model: only text content.

2.15.1. "ascii" Attribute

 The ASCII equivalent of the country name.

2.16. <cref>

 Represents a comment.
 Comments can be used in a document while it is work in progress.
 They might appear either inline and visually highlighted, at the end
 of the document, or not at all, depending on the formatting tool.
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <c> (Section 3.1), <dd>
 (Section 2.18), <dt> (Section 2.21), <em> (Section 2.22), <li>
 (Section 2.29), <name> (Section 2.32), <postamble> (Section 3.5),
 <preamble> (Section 3.6), <strong> (Section 2.50), <sub>
 (Section 2.51), <sup> (Section 2.52), <t> (Section 2.53), <td>
 (Section 2.56), <th> (Section 2.58), <tt> (Section 2.62), and <ttcol>
 (Section 3.9).
 Content model:
 In any order:
 o  Text
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <relref> elements (Section 2.44)
 o  <strong> elements (Section 2.50)

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 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

2.16.1. "anchor" Attribute

 Document-wide unique identifier for this comment.

2.16.2. "display" Attribute

 Suggests whether or not the comment should be displayed by formatting
 tools.  This might be set to "false" if you want to keep a comment in
 a document after the contents of the comment have already been dealt
 with.
 Allowed values:
 o  "true" (default)
 o  "false"

2.16.3. "source" Attribute

 Holds the "source" of a comment, such as the name or the initials of
 the person who made the comment.

2.17. <date>

 Provides information about the publication date.  This element is
 used for two cases: the boilerplate of the document being produced,
 and inside bibliographic references that use the <front> element.
 Boilerplate for Internet-Drafts and RFCs:  This element defines the
    date of publication for the current document (Internet-Draft or
    RFC).  When producing Internet-Drafts, the prep tool uses this
    date to compute the expiration date (see [IDGUIDE]).  When one or
    more of "year", "month", or "day" are left out, the prep tool will
    attempt to use the current system date if the attributes that are
    present are consistent with that date.
    In dates in <rfc> elements, the month must be a number or a month
    in English.  The prep tool will silently change text month names
    to numbers.  Similarly, the year must be a four-digit number.

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    When the prep tool is used to create Internet-Drafts, it will
    reject a submitted Internet-Draft that has a <date> element in the
    boilerplate for itself that is anything other than today.  That
    is, the tool will not allow a submitter to specify a date other
    than the day of submission.  To avoid this problem, authors might
    simply not include a <date> element in the boilerplate.
 Bibliographic references:  In dates in <reference> elements, the date
    information can have prose text for the month or year.  For
    example, vague dates (year="ca. 2000"), date ranges
    (year="2012-2013"), non-specific months (month="Second quarter"),
    and so on are allowed.
 This element appears as a child element of <front> (Section 2.26).
 Content model: this element does not have any contents.

2.17.1. "day" Attribute

 The day of publication.

2.17.2. "month" Attribute

 The month or months of publication.

2.17.3. "year" Attribute

 The year or years of publication.

2.18. <dd>

 The definition part of an entry in a definition list.
 This element appears as a child element of <dl> (Section 2.20).
 Content model:
 Either:
    In any order, but at least one of:
  • <artwork> elements (Section 2.5)
  • <dl> elements (Section 2.20)
  • <figure> elements (Section 2.25)
  • <ol> elements (Section 2.34)

Hoffman Informational [Page 25] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

  • <sourcecode> elements (Section 2.48)
  • <t> elements (Section 2.53)
  • <ul> elements (Section 2.63)
 Or:
    In any order, but at least one of:
  • Text
  • <bcp14> elements (Section 2.9)
  • <cref> elements (Section 2.16)
  • <em> elements (Section 2.22)
  • <eref> elements (Section 2.24)
  • <iref> elements (Section 2.27)
  • <relref> elements (Section 2.44)
  • <strong> elements (Section 2.50)
  • <sub> elements (Section 2.51)
  • <sup> elements (Section 2.52)
  • <tt> elements (Section 2.62)
  • <xref> elements (Section 2.66)

2.18.1. "anchor" Attribute

 Document-wide unique identifier for this definition.

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2.19. <displayreference>

 This element gives a mapping between the anchor of a reference and a
 name that will be displayed instead.  This allows authors to display
 more mnemonic anchor names for automatically included references.
 The mapping in this element only applies to <xref> elements whose
 format is "default".  For example, if the reference uses the anchor
 "RFC6949", the following would cause that anchor in the body of
 displayed documents to be "RFC-dev":
 <displayreference target="RFC6949" to="RFC-dev"/>
 If a reference section is sorted, this element changes the sort
 order.
 It is expected that this element will only be valid in input
 documents.  It will likely be removed by prep tools when preparing a
 final version after those tools have replaced all of the associated
 anchors, targets, and "derivedContent" attributes.
 This element appears as a child element of <back> (Section 2.8).
 Content model: this element does not have any contents.

2.19.1. "target" Attribute (Mandatory)

 This attribute must be the name of an anchor in a <reference> or
 <referencegroup> element.

2.19.2. "to" Attribute (Mandatory)

 This attribute is a name that will be displayed as the anchor instead
 of the anchor that is given in the <reference> element.  The string
 given must start with one of the following characters: 0-9, a-z, or
 A-Z.  The other characters in the string must be 0-9, a-z, A-Z, "-",
 ".", or "_".

2.20. <dl>

 A definition list.  Each entry has a pair of elements: a term (<dt>)
 and a definition (<dd>).  (This is slightly different and simpler
 than the model used in HTML, which allows for multiple terms for a
 single definition.)
 This element appears as a child element of <abstract> (Section 2.1),
 <aside> (Section 2.6), <blockquote> (Section 2.10), <dd>
 (Section 2.18), <li> (Section 2.29), <note> (Section 2.33), <section>
 (Section 2.46), <td> (Section 2.56), and <th> (Section 2.58).

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 Content model:
 One or more sequences of:
 1.  One <dt> element
 2.  One <dd> element

2.20.1. "anchor" Attribute

 Document-wide unique identifier for the list.

2.20.2. "hanging" Attribute

 The "hanging" attribute defines whether or not the term appears on
 the same line as the definition.  hanging="true" indicates that the
 term is to the left of the definition, while hanging="false"
 indicates that the term will be on a separate line.
 Allowed values:
 o  "false"
 o  "true" (default)

2.20.3. "spacing" Attribute

 Defines whether or not there is a blank line between entries.
 spacing="normal" indicates a single blank line, while
 spacing="compact" indicates no space between.
 Allowed values:
 o  "normal" (default)
 o  "compact"

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2.21. <dt>

 The term being defined in a definition list.
 This element appears as a child element of <dl> (Section 2.20).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <relref> elements (Section 2.44)
 o  <strong> elements (Section 2.50)
 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

2.21.1. "anchor" Attribute

 Document-wide unique identifier for this term.

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2.22. <em>

 Indicates text that is semantically emphasized.  Text enclosed within
 this element will be displayed as italic after processing.  This
 element can be combined with other character formatting elements, and
 the formatting will be additive.
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <cref> (Section 2.16),
 <dd> (Section 2.18), <dt> (Section 2.21), <li> (Section 2.29),
 <preamble> (Section 3.6), <refcontent> (Section 2.39), <strong>
 (Section 2.50), <sub> (Section 2.51), <sup> (Section 2.52), <t>
 (Section 2.53), <td> (Section 2.56), <th> (Section 2.58), and <tt>
 (Section 2.62).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <relref> elements (Section 2.44)
 o  <strong> elements (Section 2.50)
 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

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2.23. <email>

 Provides an email address.
 The value is expected to be the addr-spec defined in Section 2 of
 [RFC6068].
 This element appears as a child element of <address> (Section 2.2).
 Content model: only text content.

2.23.1. "ascii" Attribute

 The ASCII equivalent of the author's email address.  This is only
 used if the email address has any internationalized components.

2.24. <eref>

 Represents an "external" link (as specified in the "target"
 attribute).  This is useful for embedding URIs in the body of a
 document.
 If the <eref> element has non-empty text content, formatters should
 use the content as the displayed text that is linked.  Otherwise, the
 formatter should use the value of the "target" attribute as the
 displayed text.  Formatters will link the displayed text to the value
 of the "target" attribute in a manner appropriate for the output
 format.
 For example, with an input of:
       This is described at
       <eref target="http://www.example.com/reports/r12.html"/>.
 An HTML formatter might generate:
       This is described at
       <a href="http://www.example.com/reports/r12.html">
       http://www.example.com/reports/r12.html</a>.

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 With an input of:
       This is described
       <eref target="http://www.example.com/reports/r12.html">
       in this interesting report</eref>.
 An HTML formatter might generate:
       This is described
       <a href="http://www.example.com/reports/r12.html">
       in this interesting report</a>.
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <c> (Section 3.1), <cref>
 (Section 2.16), <dd> (Section 2.18), <dt> (Section 2.21), <em>
 (Section 2.22), <li> (Section 2.29), <name> (Section 2.32),
 <postamble> (Section 3.5), <preamble> (Section 3.6), <strong>
 (Section 2.50), <sub> (Section 2.51), <sup> (Section 2.52), <t>
 (Section 2.53), <td> (Section 2.56), <th> (Section 2.58), <tt>
 (Section 2.62), and <ttcol> (Section 3.9).
 Content model: only text content.

2.24.1. "target" Attribute (Mandatory)

 URI of the link target [RFC3986].  This must begin with a scheme name
 (such as "https://") and thus not be relative to the URL of the
 current document.

2.25. <figure>

 Contains a figure with a caption with the figure number.  If the
 element contains a <name> element, the caption will also show that
 name.
 This element appears as a child element of <aside> (Section 2.6),
 <blockquote> (Section 2.10), <dd> (Section 2.18), <li>
 (Section 2.29), <section> (Section 2.46), <td> (Section 2.56), and
 <th> (Section 2.58).

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 Content model:
 In this order:
 1.  One optional <name> element (Section 2.32)
 2.  Optional <iref> elements (Section 2.27)
 3.  One optional <preamble> element (Section 3.6)
 4.  In any order, but at least one of:
  • <artwork> elements (Section 2.5)
  • <sourcecode> elements (Section 2.48)
 5.  One optional <postamble> element (Section 3.5)

2.25.1. "align" Attribute

 Deprecated.
 Note: does not affect title or <artwork> alignment.
 Allowed values:
 o  "left" (default)
 o  "center"
 o  "right"

2.25.2. "alt" Attribute

 Deprecated.  If the goal is to provide a single URI for a reference,
 use the "target" attribute in <reference> instead.

2.25.3. "anchor" Attribute

 Document-wide unique identifier for this figure.

2.25.4. "height" Attribute

 Deprecated.

2.25.5. "src" Attribute

 Deprecated.

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2.25.6. "suppress-title" Attribute

 Deprecated.
 Allowed values:
 o  "true"
 o  "false" (default)

2.25.7. "title" Attribute

 Deprecated.  Use <name> instead.

2.25.8. "width" Attribute

 Deprecated.

2.26. <front>

 Represents the "front matter": metadata (such as author information),
 the Abstract, and additional notes.
 A <front> element may have more than one <seriesInfo> element.  A
 <seriesInfo> element determines the document number (for RFCs) or
 name (for Internet-Drafts).  Another <seriesInfo> element determines
 the "maturity level" (defined in [RFC2026]), using values of "std"
 for "Standards Track", "bcp" for "BCP", "info" for "Informational",
 "exp" for "Experimental", and "historic" for "Historic".  The "name"
 attributes of those multiple <seriesInfo> elements interact as
 described in Section 2.47.
 This element appears as a child element of <reference> (Section 2.40)
 and <rfc> (Section 2.45).
 Content model:
 In this order:
 1.   One <title> element (Section 2.60)
 2.   Optional <seriesInfo> elements (Section 2.47)
 3.   One or more <author> elements (Section 2.7)
 4.   One optional <date> element (Section 2.17)
 5.   Optional <area> elements (Section 2.4)

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 6.   Optional <workgroup> elements (Section 2.65)
 7.   Optional <keyword> elements (Section 2.28)
 8.   One optional <abstract> element (Section 2.1)
 9.   Optional <note> elements (Section 2.33)
 10.  One optional <boilerplate> element (Section 2.11)

2.27. <iref>

 Provides terms for the document's index.
 Index entries can be either regular entries (when just the "item"
 attribute is given) or nested entries (by specifying "subitem" as
 well), grouped under a regular entry.
 Index entries generally refer to the exact place where the <iref>
 element occurred.  An exception is the occurrence as a child element
 of <section>, in which case the whole section is considered to be
 relevant for that index entry.  In some formats, index entries of
 this type might be displayed as ranges.
 When the prep tool is creating index content, it collects the items
 in a case-sensitive fashion for both the item and subitem level.
 This element appears as a child element of <annotation>
 (Section 2.3), <aside> (Section 2.6), <blockquote> (Section 2.10),
 <c> (Section 3.1), <dd> (Section 2.18), <dt> (Section 2.21), <em>
 (Section 2.22), <figure> (Section 2.25), <li> (Section 2.29),
 <postamble> (Section 3.5), <preamble> (Section 3.6), <section>
 (Section 2.46), <strong> (Section 2.50), <sub> (Section 2.51), <sup>
 (Section 2.52), <t> (Section 2.53), <table> (Section 2.54), <td>
 (Section 2.56), <th> (Section 2.58), <tt> (Section 2.62), and <ttcol>
 (Section 3.9).
 Content model: this element does not have any contents.

2.27.1. "item" Attribute (Mandatory)

 The item to include.

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2.27.2. "primary" Attribute

 Setting this to "true" declares the occurrence as "primary", which
 might cause it to be highlighted in the index.  There is no
 restriction on the number of occurrences that can be "primary".
 Allowed values:
 o  "true"
 o  "false" (default)

2.27.3. "subitem" Attribute

 The subitem to include.

2.28. <keyword>

 Specifies a keyword applicable to the document.
 Note that each element should only contain a single keyword; for
 multiple keywords, the element can simply be repeated.
 Keywords are used both in the RFC Index and in the metadata of
 generated document representations.
 This element appears as a child element of <front> (Section 2.26).
 Content model: only text content.

2.29. <li>

 A list element, used in <ol> and <ul>.
 This element appears as a child element of <ol> (Section 2.34) and
 <ul> (Section 2.63).
 Content model:
 Either:
    In any order, but at least one of:
  • <artwork> elements (Section 2.5)
  • <dl> elements (Section 2.20)
  • <figure> elements (Section 2.25)

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  • <ol> elements (Section 2.34)
  • <sourcecode> elements (Section 2.48)
  • <t> elements (Section 2.53)
  • <ul> elements (Section 2.63)
 Or:
    In any order, but at least one of:
  • Text
  • <bcp14> elements (Section 2.9)
  • <cref> elements (Section 2.16)
  • <em> elements (Section 2.22)
  • <eref> elements (Section 2.24)
  • <iref> elements (Section 2.27)
  • <relref> elements (Section 2.44)
  • <strong> elements (Section 2.50)
  • <sub> elements (Section 2.51)
  • <sup> elements (Section 2.52)
  • <tt> elements (Section 2.62)
  • <xref> elements (Section 2.66)

2.29.1. "anchor" Attribute

 Document-wide unique identifier for this list item.

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2.30. <link>

 A link to an external document that is related to the RFC.
 The following are the supported types of external documents that can
 be pointed to in a <link> element:
 o  The current International Standard Serial Number (ISSN) for the
    RFC Series.  The value for the "rel" attribute is "item".  The
    link should use the form "urn:issn:".
 o  The Digital Object Identifier (DOI) for this document.  The value
    for the "rel" attribute is "describedBy".  The link should use the
    form specified in [RFC7669]; this is expected to change in the
    future.
 o  The Internet-Draft that was submitted to the RFC Editor to become
    the published RFC.  The value for the "rel" attribute is
    "convertedFrom".  The link should be to an IETF-controlled web
    site that retains copies of Internet-Drafts.
 o  A representation of the document offered by the document author.
    The value for the "rel" attribute is "alternate".  The link can be
    to a personally run web site.
 In RFC production mode, the prep tool needs to check the values for
 <link> before an RFC is published.  In draft production mode, the
 prep tool might remove some <link> elements during the draft
 submission process.
 This element appears as a child element of <rfc> (Section 2.45).
 Content model: this element does not have any contents.

2.30.1. "href" Attribute (Mandatory)

 The URI of the external document.

2.30.2. "rel" Attribute

 The relationship of the external document to this one.  The
 relationships are taken from the "Link Relations" registry maintained
 by IANA [LINKRELATIONS].

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2.31. <middle>

 Represents the main content of the document.
 This element appears as a child element of <rfc> (Section 2.45).
 Content model:
 One or more <section> elements (Section 2.46)

2.32. <name>

 The name of the section, note, figure, or texttable.  This name can
 indicate markup of flowing text (for example, including references or
 making some characters use a fixed-width font).
 This element appears as a child element of <figure> (Section 2.25),
 <note> (Section 2.33), <references> (Section 2.42), <section>
 (Section 2.46), <table> (Section 2.54), and <texttable>
 (Section 3.8).
 Content model:
 In any order:
 o  Text
 o  <cref> elements (Section 2.16)
 o  <eref> elements (Section 2.24)
 o  <relref> elements (Section 2.44)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

2.33. <note>

 Creates an unnumbered, titled block of text that appears after the
 Abstract.
 It is usually used for additional information to reviewers (Working
 Group information, mailing list, ...) or for additional publication
 information such as "IESG Notes".
 This element appears as a child element of <front> (Section 2.26).

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 Content model:
 In this order:
 1.  One optional <name> element (Section 2.32)
 2.  In any order, but at least one of:
  • <dl> elements (Section 2.20)
  • <ol> elements (Section 2.34)
  • <t> elements (Section 2.53)
  • <ul> elements (Section 2.63)

2.33.1. "removeInRFC" Attribute

 If set to "true", this note is marked in the prep tool with text
 indicating that it should be removed before the document is published
 as an RFC.  That text will be "This note is to be removed before
 publishing as an RFC."
 Allowed values:
 o  "true"
 o  "false" (default)

2.33.2. "title" Attribute

 Deprecated.  Use <name> instead.

2.34. <ol>

 An ordered list.  The labels on the items will be either a number or
 a letter, depending on the value of the style attribute.
 This element appears as a child element of <abstract> (Section 2.1),
 <aside> (Section 2.6), <blockquote> (Section 2.10), <dd>
 (Section 2.18), <li> (Section 2.29), <note> (Section 2.33), <section>
 (Section 2.46), <td> (Section 2.56), and <th> (Section 2.58).
 Content model:
 One or more <li> elements (Section 2.29)

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2.34.1. "anchor" Attribute

 Document-wide unique identifier for the list.

2.34.2. "group" Attribute

 When the prep tool sees an <ol> element with a "group" attribute that
 has already been seen, it continues the numbering of the list from
 where the previous list with the same group name left off.  If an
 <ol> element has both a "group" attribute and a "start" attribute,
 the group's numbering is reset to the given start value.

2.34.3. "spacing" Attribute

 Defines whether or not there is a blank line between entries.
 spacing="normal" indicates a single blank line, while
 spacing="compact" indicates no space between.
 Allowed values:
 o  "normal" (default)
 o  "compact"

2.34.4. "start" Attribute

 The ordinal value at which to start the list.  This defaults to "1"
 and must be an integer of 0 or greater.

2.34.5. "type" Attribute

 The type of the labels on list items.  If the length of the type
 value is 1, the meaning is the same as it is for HTML:
 a  Lowercase letters (a, b, c, ...)
 A  Uppercase letters (A, B, C, ...)
 1  Decimal numbers (1, 2, 3, ...)
 i  Lowercase Roman numerals (i, ii, iii, ...)
 I  Uppercase Roman numerals (I, II, III, ...)
 For types "a" and "A", after the 26th entry, the numbering starts at
 "aa"/"AA", then "ab"/"AB", and so on.

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 If the length of the type value is greater than 1, the value must
 contain a percent-encoded indicator and other text.  The value is a
 free-form text that allows counter values to be inserted using a
 "percent-letter" format.  For instance, "[REQ%d]" generates labels of
 the form "[REQ1]", where "%d" inserts the item number as a decimal
 number.
 The following formats are supported:
 %c Lowercase letters (a, b, c, ...)
 %C Uppercase letters (A, B, C, ...)
 %d Decimal numbers (1, 2, 3, ...)
 %i Lowercase Roman numerals (i, ii, iii, ...)
 %I Uppercase Roman numerals (I, II, III, ...)
 %% Represents a percent sign
 Other formats are reserved for future use.  Only one percent encoding
 other than "%%" is allowed in a type string.
 It is an error for the type string to be empty.  For bulleted lists,
 use the <ul> element.  For lists that have neither bullets nor
 numbers, use the <ul> element with the 'empty="true"' attribute.
 If no type attribute is given, the default type is the same as
 "type='%d.'".

2.35. <organization>

 Specifies the affiliation [RFC7322] of an author.
 This information appears both in the "Author's Address" section and
 on the front page (see [RFC7322] for more information).  If the value
 is long, an abbreviated variant can be specified in the "abbrev"
 attribute.
 This element appears as a child element of <author> (Section 2.7).
 Content model: only text content.

2.35.1. "abbrev" Attribute

 Abbreviated variant.

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2.35.2. "ascii" Attribute

 The ASCII equivalent of the organization's name.

2.36. <phone>

 Represents a phone number.
 The value is expected to be the scheme-specific part of a "tel" URI
 (and so does not include the prefix "tel:"), using the
 "global-number-digits" syntax.  See Section 3 of [RFC3966] for
 details.
 This element appears as a child element of <address> (Section 2.2).
 Content model: only text content.

2.37. <postal>

 Contains optional child elements providing postal information.  These
 elements will be displayed in an order that is specific to
 formatters.  A postal address can contain only a set of <street>,
 <city>, <region>, <code>, and <country> elements, or only an ordered
 set of <postalLine> elements, but not both.
 This element appears as a child element of <address> (Section 2.2).
 Content model:
 Either:
    In any order:
  • <city> elements (Section 2.13)
  • <code> elements (Section 2.14)
  • <country> elements (Section 2.15)
  • <region> elements (Section 2.43)
  • <street> elements (Section 2.49)
 Or:
    One or more <postalLine> elements (Section 2.38)

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2.38. <postalLine>

 Represents one line of a postal address.  When more than one
 <postalLine> is given, the prep tool emits them in the order given.
 This element appears as a child element of <postal> (Section 2.37).
 Content model: only text content.

2.38.1. "ascii" Attribute

 The ASCII equivalent of the text in the address line.

2.39. <refcontent>

 Text that should appear between the title and the date of a
 reference.  The purpose of this element is to prevent the need to
 abuse <seriesInfo> to get such text in a reference.
 For example:
 <reference anchor="April1">
   <front>
     <title>On Being A Fool</title>
     <author initials="K." surname="Phunny" fullname="Knot Phunny"/>
     <date year="2000" month="April"/>
   </front>
   <refcontent>Self-published pamphlet</refcontent>
 </reference>
 would render as:
    [April1]     Phunny, K., "On Being A Fool", Self-published
                 pamphlet, April 2000.
 This element appears as a child element of <reference>
 (Section 2.40).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <em> elements (Section 2.22)

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 o  <strong> elements (Section 2.50)
 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)

2.40. <reference>

 Represents a bibliographic reference.
 This element appears as a child element of <referencegroup>
 (Section 2.41) and <references> (Section 2.42).
 Content model:
 In this order:
 1.  One <front> element (Section 2.26)
 2.  In any order:
  • <annotation> elements (Section 2.3)
  • <format> elements (Section 3.3)
  • <refcontent> elements (Section 2.39)
  • <seriesInfo> elements (Section 2.47; deprecated in this

context)

2.40.1. "anchor" Attribute (Mandatory)

 Document-wide unique identifier for this reference.  Usually, this
 will be used both to "label" the reference in the "References"
 section and as an identifier in links to this reference entry.

2.40.2. "quoteTitle" Attribute

 Specifies whether or not the title in the reference should be quoted.
 This can be used to prevent quoting, such as on errata.
 Allowed values:
 o  "true" (default)
 o  "false"

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2.40.3. "target" Attribute

 Holds the URI for the reference.

2.41. <referencegroup>

 Represents a list of bibliographic references that will be
 represented as a single reference.  This is most often used to
 reference STDs and BCPs, where a single reference (such as "BCP 9")
 may encompass more than one RFC.
 This element appears as a child element of <references>
 (Section 2.42).
 Content model:
 One or more <reference> elements (Section 2.40)

2.41.1. "anchor" Attribute (Mandatory)

 Document-wide unique identifier for this reference group.  Usually,
 this will be used both to "label" the reference group in the
 "References" section and as an identifier in links to this reference
 entry.

2.42. <references>

 Contains a set of bibliographic references.
 In the early days of the RFC Series, there was only one "References"
 section per RFC.  This convention was later changed to group
 references into two sets, "Normative" and "Informative", as described
 in [RFC7322].  This vocabulary supports the split with the <name>
 child element.  In general, the title should be either "Normative
 References" or "Informative References".
 This element appears as a child element of <back> (Section 2.8).

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 Content model:
 In this order:
 1.  One optional <name> element (Section 2.32)
 2.  In any order:
  • <reference> elements (Section 2.40)
  • <referencegroup> elements (Section 2.41)

2.42.1. "anchor" Attribute

 An optional user-supplied identifier for this set of references.

2.42.2. "title" Attribute

 Deprecated.  Use <name> instead.

2.43. <region>

 Provides the region name in a postal address.
 This element appears as a child element of <postal> (Section 2.37).
 Content model: only text content.

2.43.1. "ascii" Attribute

 The ASCII equivalent of the region name.

2.44. <relref>

 Represents a link to a specific part of a document that appears in a
 <reference> element.  Formatters that have links (such as HTML and
 PDF) render <relref> elements as external hyperlinks to the specified
 part of the reference, creating the link target by combining the base
 URI from the <reference> element with the "relative" attribute from
 this element.  The "target" attribute is required, and it must be the
 anchor of a <reference> element.
 The "section" attribute is required, and the "relative" attribute is
 optional.  If the reference is not an RFC or Internet-Draft that is
 in the v3 format, the element needs to have a "relative" attribute;
 in this case, the value of the "section" attribute is ignored.

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 An example of the <relref> element with text content might be:
       See
       <relref section="2.3" target="RFC9999" displayFormat="bare">
       the protocol overview</relref>
       for more information.
 An HTML formatter might generate:
       See
       <a href="http://www.rfc-editor.org/rfc/rfc9999.html#s-2.3">
       the protocol overview</a>
       for more information.
 Note that the URL in the above example might be different when the
 RFC Editor deploys the v3 format.
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <cref> (Section 2.16),
 <dd> (Section 2.18), <dt> (Section 2.21), <em> (Section 2.22), <li>
 (Section 2.29), <name> (Section 2.32), <preamble> (Section 3.6),
 <strong> (Section 2.50), <sub> (Section 2.51), <sup> (Section 2.52),
 <t> (Section 2.53), <td> (Section 2.56), <th> (Section 2.58), and
 <tt> (Section 2.62).
 Content model: only text content.

2.44.1. "displayFormat" Attribute

 This attribute is used to signal formatters what the desired format
 of the relative reference should be.  Formatters for document types
 that have linking capability should wrap each part of the displayed
 text in hyperlinks.  If there is content in the <relref> element,
 formatters will ignore the value of this attribute.
 "of"
    A formatter should display the relative reference as the word
    "Section" followed by a space, the contents of the "section"
    attribute followed by a space, the word "of", another space, and
    the value from the "target" attribute enclosed in square brackets.
    For example, with an input of:
       See
       <relref section="2.3" target="RFC9999" displayFormat="of"/>
       for an overview.

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    An HTML formatter might generate:
       See
       <a href="http://www.rfc-editor.org/info/rfc9999#s-2.3">
       Section 2.3</a> of
       [<a href="#RFC9999">RFC9999</a>]
       for an overview.
    Note that "displayFormat='of'" is the default for <relref>, so it
    does not need to be given in a <relref> element if that format is
    desired.
 "comma"
    A formatter should display the relative reference as the value
    from the "target" attribute enclosed in square brackets, a comma,
    a space, the word "Section" followed by a space, and the "section"
    attribute.
    For example, with an input of:
       See
       <relref section="2.3" target="RFC9999" displayFormat="comma"/>,
       for an overview.
    An HTML formatter might generate:
       See
       [<a href="#RFC9999">RFC9999</a>],
       <a href="http://www.rfc-editor.org/info/rfc9999#s-2.3">
       Section 2.3</a>, for an overview.
 "parens"
    A formatter should display the relative reference as the value
    from the "target" attribute enclosed in square brackets, a space,
    a left parenthesis, the word "Section" followed by a space, the
    "section" attribute, and a right parenthesis.
    For example, with an input of:
       See
       <relref section="2.3" target="RFC9999" displayFormat="parens"/>
       for an overview.

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    An HTML formatter might generate:
       See
       [<a href="#RFC9999">RFC9999</a>]
       (<a href="http://www.rfc-editor.org/info/rfc9999#s-2.3">
       Section 2.3</a>)
       for an overview.
 "bare"
    A formatter should display the relative reference as the contents
    of the "section" attribute and nothing else.  This is useful when
    there are multiple relative references to a single base reference.
    For example:
       See Sections
       <relref section="2.3" target="RFC9999" displayFormat="bare"/>
       and
       <relref section="2.4" target="RFC9999" displayFormat="of"/>
       for an overview.
    An HTML formatter might generate:
       See Sections
       <a href="http://www.rfc-editor.org/info/rfc9999#s-2.3">
       2.3</a>
       and
       <a href="http://www.rfc-editor.org/info/rfc9999#s-2.4">
       Section 2.4</a> of
       [<a href="#RFC9999">RFC9999</a>]
       for an overview.
 Allowed values:
 o  "of" (default)
 o  "comma"
 o  "parens"
 o  "bare"

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2.44.2. "relative" Attribute

 Specifies a relative reference from the URI in the target reference.
 This value must include whatever leading character is needed to
 create the relative reference; typically, this is "#" for HTML
 documents.

2.44.3. "section" Attribute (Mandatory)

 Specifies a section of the target reference.  If the reference is not
 an RFC or Internet-Draft in the v3 format, it is an error.

2.44.4. "target" Attribute (Mandatory)

 The anchor of the reference for this element.  If this value is not
 an anchor to a <reference> or <referencegroup> element, it is an
 error.  If the reference at the target has no URI, it is an error.

2.45. <rfc>

 This is the root element of the xml2rfc vocabulary.
 Content model:
 In this order:
 1.  Optional <link> elements (Section 2.30)
 2.  One <front> element (Section 2.26)
 3.  One <middle> element (Section 2.31)
 4.  One optional <back> element (Section 2.8)

2.45.1. "category" Attribute

 Deprecated; instead, use the "name" attribute in <seriesInfo>.

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2.45.2. "consensus" Attribute

 Affects the generated boilerplate.  Note that the values of "no" and
 "yes" are deprecated and are replaced by "false" (the default) and
 "true".
 See [RFC7841] for more information.
 Allowed values:
 o  "no"
 o  "yes"
 o  "false" (default)
 o  "true"

2.45.3. "docName" Attribute

 Deprecated; instead, use the "value" attribute in <seriesInfo>.

2.45.4. "indexInclude" Attribute

 Specifies whether or not a formatter is requested to include an index
 in generated files.  If the source file has no <iref> elements, an
 index is never generated.  This option is useful for generating
 documents where the source document has <iref> elements but the
 author no longer wants an index.
 Allowed values:
 o  "true" (default)
 o  "false"

2.45.5. "ipr" Attribute

 Represents the Intellectual Property status of the document.  See
 Appendix A.1 for details.

2.45.6. "iprExtract" Attribute

 Identifies a single section within the document for which extraction
 "as is" is explicitly allowed (only relevant for historic values of
 the "ipr" attribute).

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2.45.7. "number" Attribute

 Deprecated; instead, use the "value" attribute in <seriesInfo>.

2.45.8. "obsoletes" Attribute

 A comma-separated list of RFC numbers or Internet-Draft names.
 The prep tool will parse the attribute value so that incorrect
 references can be detected.

2.45.9. "prepTime" Attribute

 The date that the XML was processed by a prep tool.  This is included
 in the XML file just before it is saved to disk.  The value is
 formatted using the "date-time" format defined in Section 5.6 of
 [RFC3339].  The "time-offset" should be "Z".

2.45.10. "seriesNo" Attribute

 Deprecated; instead, use the "value" attribute in <seriesInfo>.

2.45.11. "sortRefs" Attribute

 Specifies whether or not the prep tool will sort the references in
 each reference section.
 Allowed values:
 o  "true"
 o  "false" (default)

2.45.12. "submissionType" Attribute

 The document stream, as described in [RFC7841].  (The RFC Series
 Editor may change the list of allowed values in the future.)
 Allowed values:
 o  "IETF" (default)
 o  "IAB"
 o  "IRTF"
 o  "independent"

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2.45.13. "symRefs" Attribute

 Specifies whether or not a formatter is requested to use symbolic
 references (such as "[RFC2119]").  If the value for this is "false",
 the references come out as numbers (such as "[3]").
 Allowed values:
 o  "true" (default)
 o  "false"

2.45.14. "tocDepth" Attribute

 Specifies the number of levels of headings that a formatter is
 requested to include in the table of contents; the default is "3".

2.45.15. "tocInclude" Attribute

 Specifies whether or not a formatter is requested to include a table
 of contents in generated files.
 Allowed values:
 o  "true" (default)
 o  "false"

2.45.16. "updates" Attribute

 A comma-separated list of RFC numbers or Internet-Draft names.
 The prep tool will parse the attribute value so that incorrect
 references can be detected.

2.45.17. "version" Attribute

 Specifies the version of xml2rfc syntax used in this document.  The
 only expected value (for now) is "3".

2.46. <section>

 Represents a section (when inside a <middle> element) or an appendix
 (when inside a <back> element).
 Subsections are created by nesting <section> elements inside
 <section> elements.  Sections are allowed to be empty.

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 This element appears as a child element of <back> (Section 2.8),
 <boilerplate> (Section 2.11), <middle> (Section 2.31), and <section>
 (Section 2.46).
 Content model:
 In this order:
 1.  One optional <name> element (Section 2.32)
 2.  In any order:
  • <artwork> elements (Section 2.5)
  • <aside> elements (Section 2.6)
  • <blockquote> elements (Section 2.10)
  • <dl> elements (Section 2.20)
  • <figure> elements (Section 2.25)
  • <iref> elements (Section 2.27)
  • <ol> elements (Section 2.34)
  • <sourcecode> elements (Section 2.48)
  • <t> elements (Section 2.53)
  • <table> elements (Section 2.54)
  • <texttable> elements (Section 3.8)
  • <ul> elements (Section 2.63)
 3.  Optional <section> elements (Section 2.46)

2.46.1. "anchor" Attribute

 Document-wide unique identifier for this section.

2.46.2. "numbered" Attribute

 If set to "false", the formatter is requested to not display a
 section number.  The prep tool will verify that such a section is not
 followed by a numbered section in this part of the document and will
 verify that the section is a top-level section.

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 Allowed values:
 o  "true" (default)
 o  "false"

2.46.3. "removeInRFC" Attribute

 If set to "true", this note is marked in the prep tool with text
 indicating that it should be removed before the document is published
 as an RFC.  That text will be "This note is to be removed before
 publishing as an RFC."
 Allowed values:
 o  "true"
 o  "false" (default)

2.46.4. "title" Attribute

 Deprecated.  Use <name> instead.

2.46.5. "toc" Attribute

 Indicates to a formatter whether or not the section is to be included
 in a table of contents, if such a table of contents is produced.
 This only takes effect if the level of the section would have
 appeared in the table of contents based on the "tocDepth" attribute
 of the <rfc> element, and of course only if the table of contents is
 being created based on the "tocInclude" attribute of the <rfc>
 element.  If this is set to "exclude", any section below this one
 will be excluded as well.  The "default" value indicates inclusion of
 the section if it would be included by the tocDepth attribute of the
 <rfc> element.
 Allowed values:
 o  "include"
 o  "exclude"
 o  "default" (default)

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2.47. <seriesInfo>

 Specifies the document series in which this document appears, and
 also specifies an identifier within that series.
 A processing tool determines whether it is working on an RFC or an
 Internet-Draft by inspecting the "name" attribute of a <seriesInfo>
 element inside the <front> element inside the <rfc> element, looking
 for "RFC" or "Internet-Draft".  (Specifying neither value in any of
 the <seriesInfo> elements can be useful for producing other types of
 documents but is out of scope for this specification.)
 It is invalid to have multiple <seriesInfo> elements inside the same
 <front> element containing the same "name" value.  Some combinations
 of <seriesInfo> "name" attribute values make no sense, such as having
 both <seriesInfo name="rfc"/> and <seriesInfo name="Internet-Draft"/>
 in the same <front> element.
 This element appears as a child element of <front> (Section 2.26) and
 <reference> (Section 2.40; deprecated in this context).
 Content model: this element does not have any contents.

2.47.1. "asciiName" Attribute

 The ASCII equivalent of the name field.

2.47.2. "asciiValue" Attribute

 The ASCII equivalent of the value field.

2.47.3. "name" Attribute (Mandatory)

 The name of the series.  The currently known values are "RFC",
 "Internet-Draft", and "DOI".  The RFC Series Editor may change this
 list in the future.
 Some of the values for "name" interact as follows:
 o  If a <front> element contains a <seriesInfo> element with a name
    of "Internet-Draft", it can also have at most one additional
    <seriesInfo> element with a "status" attribute whose value is of
    "standard", "full-standard", "bcp", "fyi", "informational",
    "experimental", or "historic" to indicate the intended status of
    this Internet-Draft, if it were to be later published as an RFC.
    If such an additional <seriesInfo> element has one of those
    statuses, the name needs to be "".

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 o  If a <front> element contains a <seriesInfo> element with a name
    of "RFC", it can also have at most one additional <seriesInfo>
    element with a "status" attribute whose value is of
    "full-standard", "bcp", or "fyi" to indicate the current status of
    this RFC.  If such an additional <seriesInfo> element has one of
    those statuses, the "value" attribute for that name needs to be
    the number within that series.  That <front> element might also
    contain an additional <seriesInfo> element with the status of
    "info", "exp", or "historic" and a name of "" to indicate the
    status of the RFC.
 o  A <front> element that has a <seriesInfo> element that has the
    name "Internet-Draft" cannot also have a <seriesInfo> element that
    has the name "RFC".
 o  The <seriesInfo> element can contain the DOI for the referenced
    document.  This cannot be used when the <seriesInfo> element is an
    eventual child element of an <rfc> element -- only as an eventual
    child of a <reference> element.  The "value" attribute should use
    the form specified in [RFC7669].

2.47.4. "status" Attribute

 The status of this document.  The currently known values are
 "standard", "informational", "experimental", "bcp", "fyi", and
 "full-standard".  The RFC Series Editor may change this list in the
 future.

2.47.5. "stream" Attribute

 The stream (as described in [RFC7841]) that originated the document.
 (The RFC Series Editor may change this list in the future.)
 Allowed values:
 o  "IETF" (default)
 o  "IAB"
 o  "IRTF"
 o  "independent"

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2.47.6. "value" Attribute (Mandatory)

 The identifier within the series specified by the "name" attribute.
 For BCPs, FYIs, RFCs, and STDs, this is the number within the series.
 For Internet-Drafts, it is the full draft name (ending with the
 two-digit version number).  For DOIs, the value is given, such as
 "10.17487/rfc1149", as described in [RFC7669].
 The name in the value should be the document name without any file
 extension.  For Internet-Drafts, the value for this attribute should
 be "draft-ietf-somewg-someprotocol-07", not
 "draft-ietf-somewg-someprotocol-07.txt".

2.48. <sourcecode>

 This element allows the inclusion of source code into the document.
 When rendered, source code is always shown in a monospace font.  When
 <sourcecode> is a child of <figure> or <section>, it provides full
 control of horizontal whitespace and line breaks.  When formatted, it
 is indented relative to the left margin of the enclosing element.  It
 is thus useful for source code and formal languages (such as ABNF
 [RFC5234] or the RNC notation used in this document).  (When
 <sourcecode> is a child of other elements, it flows with the text
 that surrounds it.)  Tab characters (U+0009) inside of this element
 are prohibited.
 For artwork such as character-based art, diagrams of message layouts,
 and so on, use the <artwork> element instead.
 Output formatters that do pagination should attempt to keep source
 code on a single page.  This is to prevent source code that is split
 across pages from looking like two separate pieces of code.
 See Section 5 for a description of how to deal with issues of using
 "&" and "<" characters in source code.
 This element appears as a child element of <blockquote>
 (Section 2.10), <dd> (Section 2.18), <figure> (Section 2.25), <li>
 (Section 2.29), <section> (Section 2.46), <td> (Section 2.56), and
 <th> (Section 2.58).
 Content model: only text content.

2.48.1. "anchor" Attribute

 Document-wide unique identifier for this source code.

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2.48.2. "name" Attribute

 A filename suitable for the contents (such as for extraction to a
 local file).  This attribute can be helpful for other kinds of tools
 (such as automated syntax checkers, which work by extracting the
 source code).  Note that the "name" attribute does not need to be
 unique for <artwork> elements in a document.  If multiple
 <sourcecode> elements have the same "name" attribute, a formatter
 might assume that the elements are all fragments of a single file,
 and such a formatter can collect those fragments for later
 processing.

2.48.3. "src" Attribute

 The URI reference of a source file [RFC3986].
 It is an error to have both a "src" attribute and content in the
 <sourcecode> element.

2.48.4. "type" Attribute

 Specifies the type of the source code.  The value of this attribute
 is free text with certain values designated as preferred.
 The preferred values for <sourcecode> types are:
 o  abnf
 o  asn.1
 o  bash
 o  c++
 o  c
 o  cbor
 o  dtd
 o  java
 o  javascript
 o  json
 o  mib

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 o  perl
 o  pseudocode
 o  python
 o  rnc
 o  xml
 o  yang
 The RFC Series Editor will maintain a complete list of the preferred
 values on the RFC Editor web site, and that list is expected to be
 updated over time.  Thus, a consumer of v3 XML should not cause a
 failure when it encounters an unexpected type or no type is
 specified.

2.49. <street>

 Provides a street address.
 This element appears as a child element of <postal> (Section 2.37).
 Content model: only text content.

2.49.1. "ascii" Attribute

 The ASCII equivalent of the street address.

2.50. <strong>

 Indicates text that is semantically strong.  Text enclosed within
 this element will be displayed as bold after processing.  This
 element can be combined with other character formatting elements, and
 the formatting will be additive.
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <cref> (Section 2.16),
 <dd> (Section 2.18), <dt> (Section 2.21), <em> (Section 2.22), <li>
 (Section 2.29), <preamble> (Section 3.6), <refcontent>
 (Section 2.39), <sub> (Section 2.51), <sup> (Section 2.52), <t>
 (Section 2.53), <td> (Section 2.56), <th> (Section 2.58), and <tt>
 (Section 2.62).

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 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <relref> elements (Section 2.44)
 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

2.51. <sub>

 Causes the text to be displayed as subscript, approximately half a
 letter-height lower than normal text.  This element can be combined
 with other character formatting elements, and the formatting will be
 additive.
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <cref> (Section 2.16),
 <dd> (Section 2.18), <dt> (Section 2.21), <em> (Section 2.22), <li>
 (Section 2.29), <preamble> (Section 3.6), <refcontent>
 (Section 2.39), <strong> (Section 2.50), <t> (Section 2.53), <td>
 (Section 2.56), <th> (Section 2.58), and <tt> (Section 2.62).

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 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <relref> elements (Section 2.44)
 o  <strong> elements (Section 2.50)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

2.52. <sup>

 Causes the text to be displayed as superscript, approximately half a
 letter-height higher than normal text.  This element can be combined
 with other character formatting elements, and the formatting will be
 additive.
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <cref> (Section 2.16),
 <dd> (Section 2.18), <dt> (Section 2.21), <em> (Section 2.22), <li>
 (Section 2.29), <preamble> (Section 3.6), <refcontent>
 (Section 2.39), <strong> (Section 2.50), <t> (Section 2.53), <td>
 (Section 2.56), <th> (Section 2.58), and <tt> (Section 2.62).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)

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 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <relref> elements (Section 2.44)
 o  <strong> elements (Section 2.50)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

2.53. <t>

 Contains a paragraph of text.
 This element appears as a child element of <abstract> (Section 2.1),
 <aside> (Section 2.6), <blockquote> (Section 2.10), <dd>
 (Section 2.18), <li> (Section 2.29), <list> (Section 3.4), <note>
 (Section 2.33), <section> (Section 2.46), <td> (Section 2.56), and
 <th> (Section 2.58).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <list> elements (Section 3.4)
 o  <relref> elements (Section 2.44)
 o  <spanx> elements (Section 3.7)
 o  <strong> elements (Section 2.50)

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 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)
 o  <vspace> elements (Section 3.10)
 o  <xref> elements (Section 2.66)

2.53.1. "anchor" Attribute

 Document-wide unique identifier for this paragraph.

2.53.2. "hangText" Attribute

 Deprecated.  Instead, use <dd> inside of a definition list (<dl>).

2.53.3. "keepWithNext" Attribute

 Acts as a hint to the output formatters that do pagination to do a
 best-effort attempt to keep the paragraph with the next element,
 whatever that happens to be.  For example, the HTML output @media
 print CSS ("CSS" refers to Cascading Style Sheets) might translate
 this to page-break-after: avoid.  For PDF, the paginator could
 attempt to keep the paragraph with the next element.  Note: this
 attribute is strictly a hint and not always actionable.
 Allowed values:
 o  "false" (default)
 o  "true"

2.53.4. "keepWithPrevious" Attribute

 Acts as a hint to the output formatters that do pagination to do a
 best-effort attempt to keep the paragraph with the previous element,
 whatever that happens to be.  For example, the HTML output @media
 print CSS might translate this to page-break-before: avoid.  For PDF,
 the paginator could attempt to keep the paragraph with the previous
 element.  Note: this attribute is strictly a hint and not always
 actionable.

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 Allowed values:
 o  "false" (default)
 o  "true"

2.54. <table>

 Contains a table with a caption with the table number.  If the
 element contains a <name> element, the caption will also show that
 name.
 Inside the <table> element is, optionally, a <thead> element to
 contain the rows that will be the table's heading and, optionally, a
 <tfoot> element to contain the rows of the table's footer.  If the
 XML is converted to a representation that has page breaks (such as
 PDFs or printed HTML), the header and footer are meant to appear on
 each page.
 This element appears as a child element of <aside> (Section 2.6) and
 <section> (Section 2.46).
 Content model:
 In this order:
 1.  One optional <name> element (Section 2.32)
 2.  Optional <iref> elements (Section 2.27)
 3.  One optional <thead> element (Section 2.59)
 4.  One or more <tbody> elements (Section 2.55)
 5.  One optional <tfoot> element (Section 2.57)

2.54.1. "anchor" Attribute

 Document-wide unique identifier for this table.

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2.55. <tbody>

 A container for a set of body rows for a table.
 This element appears as a child element of <table> (Section 2.54).
 Content model:
 One or more <tr> elements (Section 2.61)

2.55.1. "anchor" Attribute

 Document-wide unique identifier for the tbody.

2.56. <td>

 A cell in a table row.
 This element appears as a child element of <tr> (Section 2.61).
 Content model:
 Either:
    In any order, but at least one of:
  • <artwork> elements (Section 2.5)
  • <dl> elements (Section 2.20)
  • <figure> elements (Section 2.25)
  • <ol> elements (Section 2.34)
  • <sourcecode> elements (Section 2.48)
  • <t> elements (Section 2.53)
  • <ul> elements (Section 2.63)

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 Or:
    In any order:
  • Text
  • <bcp14> elements (Section 2.9)
  • <br> elements (Section 2.12)
  • <cref> elements (Section 2.16)
  • <em> elements (Section 2.22)
  • <eref> elements (Section 2.24)
  • <iref> elements (Section 2.27)
  • <relref> elements (Section 2.44)
  • <strong> elements (Section 2.50)
  • <sub> elements (Section 2.51)
  • <sup> elements (Section 2.52)
  • <tt> elements (Section 2.62)
  • <xref> elements (Section 2.66)

2.56.1. "align" Attribute

 Controls whether the content of the cell appears left justified
 (default), centered, or right justified.  Note that "center" or
 "right" will probably only work well in cells with plain text; any
 other elements might make the contents render badly.
 Allowed values:
 o  "left" (default)
 o  "center"
 o  "right"

2.56.2. "anchor" Attribute

 Document-wide unique identifier for the cell.

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2.56.3. "colspan" Attribute

 The number of columns that the cell is to span.  For example, setting
 "colspan='3'" indicates that the cell occupies the same horizontal
 space as three cells of a row without any "colspan" attributes.

2.56.4. "rowspan" Attribute

 The number of rows that the cell is to span.  For example, setting
 "rowspan='3'" indicates that the cell occupies the same vertical
 space as three rows.

2.57. <tfoot>

 A container for a set of footer rows for a table.
 This element appears as a child element of <table> (Section 2.54).
 Content model:
 One or more <tr> elements (Section 2.61)

2.57.1. "anchor" Attribute

 Document-wide unique identifier for the tfoot.

2.58. <th>

 A cell in a table row.  When rendered, this will normally come out in
 boldface; other than that, there is no difference between this and
 the <td> element.
 This element appears as a child element of <tr> (Section 2.61).
 Content model:
 Either:
    In any order, but at least one of:
  • <artwork> elements (Section 2.5)
  • <dl> elements (Section 2.20)
  • <figure> elements (Section 2.25)
  • <ol> elements (Section 2.34)

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  • <sourcecode> elements (Section 2.48)
  • <t> elements (Section 2.53)
  • <ul> elements (Section 2.63)
 Or:
    In any order:
  • Text
  • <bcp14> elements (Section 2.9)
  • <br> elements (Section 2.12)
  • <cref> elements (Section 2.16)
  • <em> elements (Section 2.22)
  • <eref> elements (Section 2.24)
  • <iref> elements (Section 2.27)
  • <relref> elements (Section 2.44)
  • <strong> elements (Section 2.50)
  • <sub> elements (Section 2.51)
  • <sup> elements (Section 2.52)
  • <tt> elements (Section 2.62)
  • <xref> elements (Section 2.66)

2.58.1. "align" Attribute

 Controls whether the content of the cell appears left justified
 (default), centered, or right justified.  Note that "center" or
 "right" will probably only work well in cells with plain text; any
 other elements might make the contents render badly.

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 Allowed values:
 o  "left" (default)
 o  "center"
 o  "right"

2.58.2. "anchor" Attribute

 Document-wide unique identifier for the row.

2.58.3. "colspan" Attribute

 The number of columns that the cell is to span.  For example, setting
 "colspan='3'" indicates that the cell occupies the same horizontal
 space as three cells of a row without any "colspan" attributes.

2.58.4. "rowspan" Attribute

 The number of rows that the cell is to span.  For example, setting
 "rowspan='3'" indicates that the cell occupies the same vertical
 space as three rows.

2.59. <thead>

 A container for a set of header rows for a table.
 This element appears as a child element of <table> (Section 2.54).
 Content model:
 One or more <tr> elements (Section 2.61)

2.59.1. "anchor" Attribute

 Document-wide unique identifier for the thead.

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2.60. <title>

 Represents the document title.
 When this element appears in the <front> element of the current
 document, the title might also appear in page headers or footers.  If
 it is long (~40 characters), the "abbrev" attribute can be used to
 specify an abbreviated variant.
 This element appears as a child element of <front> (Section 2.26).
 Content model: only text content.

2.60.1. "abbrev" Attribute

 Specifies an abbreviated variant of the document title.

2.60.2. "ascii" Attribute

 The ASCII equivalent of the title.

2.61. <tr>

 A row of a table.
 This element appears as a child element of <tbody> (Section 2.55),
 <tfoot> (Section 2.57), and <thead> (Section 2.59).
 Content model:
 In any order, but at least one of:
 o  <td> elements (Section 2.56)
 o  <th> elements (Section 2.58)

2.61.1. "anchor" Attribute

 Document-wide unique identifier for the row.

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2.62. <tt>

 Causes the text to be displayed in a constant-width font.  This
 element can be combined with other character formatting elements, and
 the formatting will be additive.
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <cref> (Section 2.16),
 <dd> (Section 2.18), <dt> (Section 2.21), <em> (Section 2.22), <li>
 (Section 2.29), <name> (Section 2.32), <preamble> (Section 3.6),
 <refcontent> (Section 2.39), <strong> (Section 2.50), <sub>
 (Section 2.51), <sup> (Section 2.52), <t> (Section 2.53), <td>
 (Section 2.56), and <th> (Section 2.58).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <relref> elements (Section 2.44)
 o  <strong> elements (Section 2.50)
 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <xref> elements (Section 2.66)

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2.63. <ul>

 An unordered list.  The labels on the items will be symbols picked by
 the formatter.
 This element appears as a child element of <abstract> (Section 2.1),
 <aside> (Section 2.6), <blockquote> (Section 2.10), <dd>
 (Section 2.18), <li> (Section 2.29), <note> (Section 2.33), <section>
 (Section 2.46), <td> (Section 2.56), and <th> (Section 2.58).
 Content model:
 One or more <li> elements (Section 2.29)

2.63.1. "anchor" Attribute

 Document-wide unique identifier for the list.

2.63.2. "empty" Attribute

 Defines whether or not the label is empty.  empty="true" indicates
 that no label will be shown.
 Allowed values:
 o  "false" (default)
 o  "true"

2.63.3. "spacing" Attribute

 Defines whether or not there is a blank line between entries.
 spacing="normal" indicates a single blank line, while
 spacing="compact" indicates no space between.
 Allowed values:
 o  "normal" (default)
 o  "compact"

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2.64. <uri>

 Contains a web address associated with the author.
 The contents should be a valid URI; this most likely will be an
 "http:" or "https:" URI.
 This element appears as a child element of <address> (Section 2.2).
 Content model: only text content.

2.65. <workgroup>

 This element is used to specify the Working Group (IETF) or Research
 Group (IRTF) from which the document originates, if any.  The
 recommended format is the official name of the Working Group (with
 some capitalization).
 In Internet-Drafts, this is used in the upper left corner of the
 boilerplate, replacing the "Network Working Group" string.
 Formatting software can append the words "Working Group" or "Research
 Group", depending on the "submissionType" property of the <rfc>
 element (Section 2.45.12).
 This element appears as a child element of <front> (Section 2.26).
 Content model: only text content.

2.66. <xref>

 A reference to an anchor in this document.  Formatters that have
 links (such as HTML and PDF) are likely to render <xref> elements as
 internal hyperlinks.  This element is useful for referring to
 references in the "References" section, to specific sections of this
 document, to specific figures, and so on.  The "target" attribute is
 required.
 This element appears as a child element of <annotation>
 (Section 2.3), <blockquote> (Section 2.10), <c> (Section 3.1), <cref>
 (Section 2.16), <dd> (Section 2.18), <dt> (Section 2.21), <em>
 (Section 2.22), <li> (Section 2.29), <name> (Section 2.32),
 <postamble> (Section 3.5), <preamble> (Section 3.6), <strong>
 (Section 2.50), <sub> (Section 2.51), <sup> (Section 2.52), <t>
 (Section 2.53), <td> (Section 2.56), <th> (Section 2.58), <tt>
 (Section 2.62), and <ttcol> (Section 3.9).
 Content model: only text content.

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2.66.1. "format" Attribute

 This attribute signals to formatters what the desired format of the
 reference should be.  Formatters for document types that have linking
 capability should wrap the displayed text in hyperlinks.
 "counter"
    The "derivedContent" attribute will contain just a counter.  This
    is used for targets that are <section>, <figure>, <table>, or
    items in an ordered list.  Using "format='counter'" where the
    target is any other type of element is an error.
    For example, with an input of:
       <section anchor="overview">Protocol Overview</section>
       . . .
       See Section <xref target="overview" format="counter"/>
       for an overview.
    An HTML formatter might generate:
       See Section <a href="#overview">1.7</a> for an overview.
 "default"
    If the element has no content, the "derivedContent" attribute will
    contain a text fragment that describes the referenced part
    completely, such as "XML" for a target that is a <reference>, or
    "Section 2" or "Table 4" for a target to a non-reference.  (If the
    element has content, the "derivedContent" attribute is filled with
    the content.)
    For example, with an input of:
       <section anchor="overview">Protocol Overview</section>
       . . .
       See <xref target="overview"/> for an overview.
    An HTML formatter might generate:
       See <a href="#overview">Section 1.7</a> for an overview.
 "none"
    Deprecated.

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 "title"
    If the target is a <reference> element, the "derivedContent"
    attribute will contain the name of the reference, extracted from
    the <title> child of the <front> child of the reference.  Or, if
    the target element has a <name> child element, the
    "derivedContent" attribute will contain the text content of that
    <name> element concatenated with the text content of each
    descendant node of <name> (that is, stripping out all of the XML
    markup, leaving only the text).  Or, if the target element does
    not contain a <name> child element, the "derivedContent" attribute
    will contain the name of the "anchor" attribute of that element
    with no other adornment.
 Allowed values:
 o  "default" (default)
 o  "title"
 o  "counter"
 o  "none"

2.66.2. "pageno" Attribute

 Deprecated.
 Allowed values:
 o  "true"
 o  "false" (default)

2.66.3. "target" Attribute (Mandatory)

 Identifies the document component being referenced.  The value needs
 to match the value of the "anchor" attribute of an element in the
 document; otherwise, it is an error.

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3. Elements from v2 That Have Been Deprecated

 This section lists the elements from v2 that have been deprecated.
 Note that some elements in v3 have attributes from v2 that are
 deprecated; those are not listed here.

3.1. <c>

 Deprecated.  Instead, use <tr>, <td>, and <th>.
 This element appears as a child element of <texttable> (Section 3.8).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <spanx> elements (Section 3.7)
 o  <strong> elements (Section 2.50)
 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

3.2. <facsimile>

 Deprecated.  The <email> element is a much more useful way to get in
 touch with authors.
 This element appears as a child element of <address> (Section 2.2).
 Content model: only text content.

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3.3. <format>

 Deprecated.  If the goal is to provide a single URI for a reference,
 use the "target" attribute in <reference> instead.
 This element appears as a child element of <reference>
 (Section 2.40).
 Content model: this element does not have any contents.

3.3.1. "octets" Attribute

 Deprecated.

3.3.2. "target" Attribute

 Deprecated.

3.3.3. "type" Attribute (Mandatory)

 Deprecated.

3.4. <list>

 Deprecated.  Instead, use <dl> for list/@style "hanging"; <ul> for
 list/@style "empty" or "symbols"; and <ol> for list/@style "letters",
 "numbers", "counter", or "format".
 This element appears as a child element of <t> (Section 2.53).
 Content model:
 One or more <t> elements (Section 2.53)

3.4.1. "counter" Attribute

 Deprecated.  The functionality of this attribute has been replaced
 with <ol>/@start.

3.4.2. "hangIndent" Attribute

 Deprecated.  Use <dl> instead.

3.4.3. "style" Attribute

 Deprecated.

Hoffman Informational [Page 79] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

3.5. <postamble>

 Deprecated.  Instead, use a regular paragraph after the figure or
 table.
 This element appears as a child element of <figure> (Section 2.25)
 and <texttable> (Section 3.8).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <spanx> elements (Section 3.7)
 o  <strong> elements (Section 2.50)
 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

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3.6. <preamble>

 Deprecated.  Instead, use a regular paragraph before the figure or
 table.
 This element appears as a child element of <figure> (Section 2.25)
 and <texttable> (Section 3.8).
 Content model:
 In any order:
 o  Text
 o  <bcp14> elements (Section 2.9)
 o  <cref> elements (Section 2.16)
 o  <em> elements (Section 2.22)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <spanx> elements (Section 3.7)
 o  <strong> elements (Section 2.50)
 o  <sub> elements (Section 2.51)
 o  <sup> elements (Section 2.52)
 o  <tt> elements (Section 2.62)
 o  <xref> elements (Section 2.66)

3.7. <spanx>

 Deprecated.
 This element appears as a child element of <annotation>
 (Section 2.3), <c> (Section 3.1), <postamble> (Section 3.5),
 <preamble> (Section 3.6), and <t> (Section 2.53).
 Content model: only text content.

Hoffman Informational [Page 81] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

3.7.1. "style" Attribute

 Deprecated.  Instead of <spanx style="emph">, use <em>; instead of
 <spanx style="strong">, use <strong>; instead of <spanx
 style="verb">, use <tt>.

3.7.2. "xml:space" Attribute

 Deprecated.
 Allowed values:
 o  "default"
 o  "preserve" (default)

3.8. <texttable>

 Deprecated.  Use <table> instead.
 This element appears as a child element of <aside> (Section 2.6) and
 <section> (Section 2.46).
 Content model:
 In this order:
 1.  One optional <name> element (Section 2.32)
 2.  One optional <preamble> element (Section 3.6)
 3.  One or more <ttcol> elements (Section 3.9)
 4.  Optional <c> elements (Section 3.1)
 5.  One optional <postamble> element (Section 3.5)

3.8.1. "align" Attribute

 Deprecated.
 Allowed values:
 o  "left"
 o  "center" (default)
 o  "right"

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3.8.2. "anchor" Attribute

 Deprecated.

3.8.3. "style" Attribute

 Deprecated.

3.8.4. "suppress-title" Attribute

 Deprecated.
 Allowed values:
 o  "true"
 o  "false" (default)

3.8.5. "title" Attribute

 Deprecated.

3.9. <ttcol>

 Deprecated.  Instead, use <tr>, <td>, and <th>.
 This element appears as a child element of <texttable> (Section 3.8).
 Content model:
 In any order:
 o  Text
 o  <cref> elements (Section 2.16)
 o  <eref> elements (Section 2.24)
 o  <iref> elements (Section 2.27)
 o  <xref> elements (Section 2.66)

Hoffman Informational [Page 83] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

3.9.1. "align" Attribute

 Deprecated.
 Allowed values:
 o  "left" (default)
 o  "center"
 o  "right"

3.9.2. "width" Attribute

 Deprecated.

3.10. <vspace>

 Deprecated.  In earlier versions of this format, <vspace> was often
 used to get an extra blank line in a list element; in the v3
 vocabulary, that can be done instead by using multiple <t> elements
 inside the <li> element.  Other uses have no direct replacement.
 This element appears as a child element of <t> (Section 2.53).
 Content model: this element does not have any contents.

3.10.1. "blankLines" Attribute

 Deprecated.

4. SVG

 The discussion of the use of SVG can be found in [RFC7996].  This
 element is part of the namespace "http://www.w3.org/2000/svg".

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5. Use of CDATA Structures and Escaping

 A common problem authors have with <artwork> and <sourcecode>
 elements is that the XML processor returns errors if the text in the
 artwork contains either the "&" or "<" character, or the string
 "]]>".  To avoid these problems, the "&" and "<" characters may be
 escaped using the strings "&amp;" and "&lt;", respectively; the "]]>"
 string can be represented as "]]&gt;".  Alternatively, they may be
 surrounded in a CDATA structure: "<![CDATA[]]>".  For example:
 Desired output:
    allowed-chars = "." | "," | "&" | "<" | ">" | "|"
 Using escaping:
 <sourcecode>
    allowed-chars = "." | "," | "&amp;" | "&lt;" | "&gt;" | "|"
 </sourcecode>
 Using CDATA:
 <sourcecode>
 <![CDATA[   allowed-chars = "." | "," | "&" | "<" | ">" | "|"]]>
 </sourcecode>
 Using CDATA is not a panacea, but it does help prevent having to use
 escapes in places where using escapes can cause other problems, such
 as difficulty of inclusion from other documents.

6. Internationalization Considerations

 This format is based on [XML] and thus does not have any issues
 representing arbitrary Unicode [UNICODE] characters in text content.
 The RFC Series Editor may restrict some of the characters that can be
 used in a particular RFC; the rules for such restrictions are covered
 in [RFC7997].

7. Security Considerations

 The "name" attribute of the <artwork> element (Section 2.5.5) can be
 used to derive a filename for saving to a local file system.
 Trusting this kind of information without pre-processing is a known
 security risk; see Section 4.3 of [RFC6266] for more information.
 The "src" attribute of the <artwork> element can be used to read
 files from the local system.  Processing tools must be careful to not
 accept dangerous values for the filename, particularly those that
 contain absolute references outside the current directory.

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 The "type" attribute of the <artwork> and <sourcecode> elements is
 meant to encourage formatters to automatically extract known types of
 content from an RFC or Internet-Draft.  While extraction is probably
 safe, those tools might also think that they could further process
 the extracted content, such as by rendering artwork or executing
 code.  Doing so without first sanity-checking the extracted content
 is clearly a terrible idea from a security perspective.  More
 generally, a tool that is reading XML input needs to be suspicious of
 any content that it intends to post-process.
 When there is an external reference to a URL, a processor or renderer
 should fetch the content into a sandbox and should have only a
 localized impact on the document processing and rendering.
 All security considerations related to XML processing are relevant as
 well (see Section 7 of [RFC3470]).

8. IANA Considerations

8.1. Internet Media Type Registration

 IANA maintains the registry of Internet Media Types [RFC6838] at
 <https://www.iana.org/assignments/media-types>.
 This document updates the specification for the Internet Media Type
 "application/rfc+xml" from the one in [RFC7749].  The following has
 been registered with IANA.
 Type name:  application
 Subtype name:  rfc+xml
 Required parameters:  There are no required parameters.
 Optional parameters:  "charset": This parameter has identical
    semantics to the charset parameter of the "application/xml" Media
    Type specified in Section 9.1 of [RFC7303].
 Encoding considerations:  Identical to those of "application/xml" as
    described in Section 9.1 of [RFC7303].
 Security considerations:  As defined in Section 7.  In addition, as
    this Media Type uses the "+xml" convention, it inherits the
    security considerations described in Section 10 of [RFC7303].

Hoffman Informational [Page 86] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

 Interoperability considerations:  Different implementations of this
    format have had interoperability issues.  It is not expected that
    publication of this application will cause those implementations
    to be fixed.
 Published specification:  This specification.
 Applications that use this Media Type:  Applications that transform
    xml2rfc to output representations such as plain text or HTML, plus
    additional analysis tools.
 Fragment identifier considerations:  The "anchor" attribute is used
    for assigning document-wide unique identifiers that can be used as
    shorthand pointers, as described in [XPOINTER].
 Additional information:
    Deprecated alias names for this type:  None
    Magic number(s):  As specified for "application/xml" in [RFC7303].
    File extension(s):  .xml or .rfcxml when disambiguation from other
       XML files is needed
    Macintosh file type code(s):  TEXT
 Person & email address to contact for further information:  See the
    Author's Address section of RFC 7991.
 Intended usage:  COMMON
 Restrictions on usage:  None
 Author:  See the Author's Address section of RFC 7991.
 Change controller:  RFC Series Editor (rse@rfc-editor.org)

8.2. Link Relation Registration

 IANA has registered "convertedFrom" in the "Link Relation Types"
 registry [LINKRELATIONS].
 Relation Name: convertedFrom
 Description: The document linked to was later converted to the
 document that contains this link relation.  For example, an RFC can
 have a link to the Internet-Draft that became the RFC; in that case,
 the link relation would be "convertedFrom".

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 Reference: This document.
 Notes: This relation is different than "predecessor-version" in that
 "predecessor-version" is for items in a version control system.  It
 is also different than "previous" in that this relation is used for
 converted resources, not those that are part of a sequence of
 resources.
 Application Data: None

9. References

9.1. Normative References

 [BCP14]    Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <http://www.rfc-editor.org/info/bcp14>.
 [XML]      Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E.,
            and F. Yergeau, "Extensible Markup Language (XML) 1.0
            (Fifth Edition)", W3C Recommendation REC-xml-20081126,
            November 2008,
            <https://www.w3.org/TR/2008/REC-xml-20081126/>.
            Latest version available at <http://www.w3.org/TR/xml>.

9.2. Informative References

 [IDGUIDE]  Housley, R., "Guidelines to Authors of Internet-Drafts",
            December 2010, <https://www.ietf.org/id-info/
            guidelines.html>.
 [LINKRELATIONS]
            IANA, "Link Relations", <https://www.iana.org/assignments/
            link-relations/>.
 [RFC2026]  Bradner, S., "The Internet Standards Process --
            Revision 3", BCP 9, RFC 2026, DOI 10.17487/RFC2026,
            October 1996, <http://www.rfc-editor.org/info/rfc2026>.
 [RFC2397]  Masinter, L., "The "data" URL scheme", RFC 2397,
            DOI 10.17487/RFC2397, August 1998,
            <http://www.rfc-editor.org/info/rfc2397>.
 [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
            DOI 10.17487/RFC2629, June 1999,
            <http://www.rfc-editor.org/info/rfc2629>.

Hoffman Informational [Page 88] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

 [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
            Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
            <http://www.rfc-editor.org/info/rfc3339>.
 [RFC3470]  Hollenbeck, S., Rose, M., and L. Masinter, "Guidelines for
            the Use of Extensible Markup Language (XML) within IETF
            Protocols", BCP 70, RFC 3470, DOI 10.17487/RFC3470,
            January 2003, <http://www.rfc-editor.org/info/rfc3470>.
 [RFC3667]  Bradner, S., "IETF Rights in Contributions", RFC 3667,
            DOI 10.17487/RFC3667, February 2004,
            <http://www.rfc-editor.org/info/rfc3667>.
 [RFC3966]  Schulzrinne, H., "The tel URI for Telephone Numbers",
            RFC 3966, DOI 10.17487/RFC3966, December 2004,
            <http://www.rfc-editor.org/info/rfc3966>.
 [RFC3978]  Bradner, S., Ed., "IETF Rights in Contributions",
            RFC 3978, DOI 10.17487/RFC3978, March 2005,
            <http://www.rfc-editor.org/info/rfc3978>.
 [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
            Resource Identifier (URI): Generic Syntax", STD 66,
            RFC 3986, DOI 10.17487/RFC3986, January 2005,
            <http://www.rfc-editor.org/info/rfc3986>.
 [RFC5234]  Crocker, D., Ed., and P. Overell, "Augmented BNF for
            Syntax Specifications: ABNF", STD 68, RFC 5234,
            DOI 10.17487/RFC5234, January 2008,
            <http://www.rfc-editor.org/info/rfc5234>.
 [RFC5378]  Bradner, S., Ed., and J. Contreras, Ed., "Rights
            Contributors Provide to the IETF Trust", BCP 78, RFC 5378,
            DOI 10.17487/RFC5378, November 2008,
            <http://www.rfc-editor.org/info/rfc5378>.
 [RFC6068]  Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto'
            URI Scheme", RFC 6068, DOI 10.17487/RFC6068, October 2010,
            <http://www.rfc-editor.org/info/rfc6068>.
 [RFC6266]  Reschke, J., "Use of the Content-Disposition Header Field
            in the Hypertext Transfer Protocol (HTTP)", RFC 6266,
            DOI 10.17487/RFC6266, June 2011,
            <http://www.rfc-editor.org/info/rfc6266>.

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 [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
            Specifications and Registration Procedures", BCP 13,
            RFC 6838, DOI 10.17487/RFC6838, January 2013,
            <http://www.rfc-editor.org/info/rfc6838>.
 [RFC6949]  Flanagan, H. and N. Brownlee, "RFC Series Format
            Requirements and Future Development", RFC 6949,
            DOI 10.17487/RFC6949, May 2013,
            <http://www.rfc-editor.org/info/rfc6949>.
 [RFC7303]  Thompson, H. and C. Lilley, "XML Media Types", RFC 7303,
            DOI 10.17487/RFC7303, July 2014,
            <http://www.rfc-editor.org/info/rfc7303>.
 [RFC7322]  Flanagan, H. and S. Ginoza, "RFC Style Guide", RFC 7322,
            DOI 10.17487/RFC7322, September 2014,
            <http://www.rfc-editor.org/info/rfc7322>.
 [RFC7669]  Levine, J., "Assigning Digital Object Identifiers to
            RFCs", RFC 7669, DOI 10.17487/RFC7669, October 2015,
            <http://www.rfc-editor.org/info/rfc7669>.
 [RFC7749]  Reschke, J., "The "xml2rfc" Version 2 Vocabulary",
            RFC 7749, DOI 10.17487/RFC7749, February 2016,
            <http://www.rfc-editor.org/info/rfc7749>.
 [RFC7841]  Halpern, J., Ed., Daigle, L., Ed., and O. Kolkman, Ed.,
            "RFC Streams, Headers, and Boilerplates", RFC 7841,
            DOI 10.17487/RFC7841, May 2016,
            <http://www.rfc-editor.org/info/rfc7841>.
 [RFC7996]  Brownlee, N., "SVG Drawings for RFCs: SVG 1.2 RFC",
            RFC 7996, DOI 10.17487/RFC7996, December 2016,
            <http://www.rfc-editor.org/info/rfc7996>.
 [RFC7997]  Flanagan, H., Ed., "The Use of Non-ASCII Characters in
            RFCs", RFC 7997, DOI 10.17487/RFC7997, December 2016,
            <http://www.rfc-editor.org/info/rfc7997>.
 [RFC7998]  Hoffman, P. and J. Hildebrand, ""xml2rfc" Version 3
            Preparation Tool Description", RFC 7998,
            DOI 10.17487/RFC7998, December 2016,
            <http://www.rfc-editor.org/info/rfc7998>.

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 [RNC]      Clark, J., "RELAX NG Compact Syntax", The Organization
            for the Advancement of Structured Information
            Standards (OASIS), November 2002,
            <https://www.oasis-open.org/committees/
            relax-ng/compact-20021121.html>.
 [RNG]      ISO/IEC, "Information Technology - Document Schema
            Definition Languages (DSDL) - Part 2: Regular-Grammar-
            Based Validation - RELAX NG (Second Edition)",
            ISO/IEC 19757-2:2008(E), December 2008.
            A useful source of RNG-related information is
            <http://relaxng.org/>.
 [TLP1.0]   IETF Trust, "Legal Provisions Relating to IETF Documents",
            November 2008,
            <http://trustee.ietf.org/license-info/IETF-TLP-1.htm>.
 [TLP2.0]   IETF Trust, "Legal Provisions Relating to IETF Documents",
            February 2009,
            <http://trustee.ietf.org/license-info/IETF-TLP-2.htm>.
 [TLP3.0]   IETF Trust, "Legal Provisions Relating to IETF Documents",
            September 2009,
            <http://trustee.ietf.org/license-info/IETF-TLP-3.htm>.
 [TLP4.0]   IETF Trust, "Legal Provisions Relating to IETF Documents",
            December 2009,
            <http://trustee.ietf.org/license-info/IETF-TLP-4.htm>.
 [TLP5.0]   IETF Trust, "Legal Provisions Relating to IETF Documents",
            March 2015,
            <http://trustee.ietf.org/license-info/IETF-TLP-5.htm>.
 [UAX24]    The Unicode Consortium, "UAX #24: Unicode Script
            Property", <http://www.unicode.org/reports/tr24/>.
 [UNICODE]  The Unicode Consortium, "The Unicode Standard",
            <http://www.unicode.org/versions/latest/>.
 [USASCII]  American National Standards Institute, "Coded Character
            Set -- 7-bit American Standard Code for Information
            Interchange", ANSI X3.4, 1986.

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 [XInclude] Marsh, J., Orchard, D., and D. Veillard, "XML Inclusions
            (XInclude) Version 1.0 (Second Edition)", W3C
            Recommendation REC-xinclude-20061115, November 2006,
            <https://www.w3.org/TR/2006/REC-xinclude-20061115/>.
            Latest version available at
            <http://www.w3.org/TR/xinclude/>.
 [XPOINTER] Grosso, P., Maler, E., Marsh, J., and N. Walsh,
            "XPointer Framework", W3C Recommendation
            REC-xptr-framework-20030325, March 2003,
            <http://www.w3.org/TR/2003/REC-xptr-framework-20030325/>.
            Latest version available at
            <http://www.w3.org/TR/xptr-framework/>.

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Appendix A. Front-Page ("Boilerplate") Generation

 The values listed here will be defined by the RFC Series Editor.
 Those listed here are believed to be the current values in use.

A.1. The "ipr" Attribute

 This attribute value can take a long list of values, each of which
 describes an IPR policy for the document (Section 2.45.5).  The
 values are not the result of a grand design, but they remain simply
 for historic reasons.  Of these values, only a few are currently in
 use; all others are supported by various tools for backwards
 compatibility with old source files.
    Note: Some variations of the boilerplate are selected based on the
    document's date; therefore, it is important to specify the "year",
    "month", and "day" attributes of the <date> element when archiving
    the XML source of an Internet-Draft on the day of submission.
 _Disclaimer: THIS ONLY PROVIDES IMPLEMENTATION INFORMATION.  IF YOU
 NEED LEGAL ADVICE, PLEASE CONTACT A LAWYER._  For further
 information, refer to <http://trustee.ietf.org/docs/
 IETF-Copyright-FAQ.pdf>.
 For the current "Copyright Notice" text, the submissionType attribute
 of the <rfc> element (Section 2.45.12) determines whether a statement
 about "Code Components" is inserted (which is the case for the value
 "IETF", which is the default).  Other values, such as "independent",
 suppress this part of the text.

A.1.1. Current Values: "*trust200902"

 The name for these values refers to version 2.0 of the IETF Trust's
 "Legal Provisions Relating to IETF Documents", sometimes simply
 called the "TLP", which went into effect on February 15, 2009
 [TLP2.0].  Updates to the document were published on September 12,
 2009 [TLP3.0] and on December 28, 2009 [TLP4.0], modifying the
 license for code components (see <http://trustee.ietf.org/
 license-info/> for further information).  The actual text is located
 in Section 6 ("Text to Be Included in IETF Documents") of these
 documents.

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 The prep tool automatically produces the "correct" text, depending on
 the document's date information (see above):
    +----------+--------------------------------+
    | TLP      | starting with publication date |
    +----------+--------------------------------+
    | [TLP3.0] | 2009-11-01                     |
    | [TLP4.0] | 2010-04-01                     |
    +----------+--------------------------------+
    The TLP was again updated in March 2015 [TLP5.0], but the changes
    made in that version do not affect the boilerplate text.

A.1.1.1. trust200902

 This value should be used unless one of the more specific
 "*trust200902" values is a better fit.  It produces the text in
 Sections 6.a and 6.b of the TLP.

A.1.1.2. noModificationTrust200902

 This produces the additional text from Section 6.c.i of the TLP:
    This document may not be modified, and derivative works of it may
    not be created, except to format it for publication as an RFC or
    to translate it into languages other than English.
    Note: this clause is incompatible with RFCs that are published on
    the Standards Track.

A.1.1.3. noDerivativesTrust200902

 This produces the additional text from Section 6.c.ii of the TLP:
    This document may not be modified, and derivative works of it may
    not be created, and it may not be published except as an
    Internet-Draft.
    Note: this clause is incompatible with RFCs.

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A.1.1.4. pre5378Trust200902

 This produces the additional text from Section 6.c.iii of the TLP,
 frequently called the "pre-5378 escape clause" referring to changes
 introduced in [RFC5378]:
    This document may contain material from IETF Documents or IETF
    Contributions published or made publicly available before November
    10, 2008.  The person(s) controlling the copyright in some of this
    material may not have granted the IETF Trust the right to allow
    modifications of such material outside the IETF Standards Process.
    Without obtaining an adequate license from the person(s)
    controlling the copyright in such materials, this document may not
    be modified outside the IETF Standards Process, and derivative
    works of it may not be created outside the IETF Standards Process,
    except to format it for publication as an RFC or to translate it
    into languages other than English.
 See Section 4 of <http://trustee.ietf.org/docs/
 IETF-Copyright-FAQ.pdf> for further information about when to use
 this value.
    Note: this text appears under "Copyright Notice", unless the
    document was published before November 2009, in which case it
    appears under "Status of This Memo".

A.1.2. Historic Values

A.1.2.1. Historic Values: "*trust200811"

 The attribute values "trust200811", "noModificationTrust200811", and
 "noDerivativesTrust200811" are similar to their "trust200902"
 counterparts, except that they use text specified in [TLP1.0].

A.1.2.2. Historic Values: "*3978"

 The attribute values "full3978", "noModification3978", and
 "noDerivatives3978" are similar to their counterparts above, except
 that they use text specified in [RFC3978].

A.1.2.3. Historic Values: "*3667"

 The attribute values "full3667", "noModification3667", and
 "noDerivatives3667" are similar to their counterparts above, except
 that they use text specified in [RFC3667].

Hoffman Informational [Page 95] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

A.1.2.4. Historic Values: "*2026"

 The attribute values "full2026" and "noDerivativeWorks2026" are
 similar to their counterparts above, except that they use text
 specified in Section 10 of [RFC2026].
 The special value "none" was also used back then; it denied the IETF
 any rights beyond publication as an Internet-Draft.

A.2. The "submissionType" Attribute

 The RFC Editor publishes documents from different "document streams",
 of which the "IETF stream" is the most prominent.  Other streams are
 the "Independent Submissions stream" (used for things such as
 discussion of Internet-related technologies that are not part of the
 IETF agenda), the "IAB stream" (Internet Architecture Board), and the
 "IRTF stream" (Internet Research Task Force).
 The values for the attribute are "IETF" (the default value),
 "independent", "IAB", and "IRTF".
 Historically, this attribute did not affect the final appearance of
 RFCs, except for subtle differences in copyright notices.  Nowadays
 (as of [RFC7841]), the stream name appears in the first line of the
 front page, and it also affects the text in the "Status of This Memo"
 section.
 For current documents, setting the "submissionType" attribute will
 have the following effect:
 o  For RFCs, the stream name appears in the upper left corner of the
    first page (in Internet-Drafts, this is either "Network Working
    Group" or the value of the <workgroup> element).
 o  For RFCs, it affects the whole "Status of This Memo" section (see
    Section 3.2 of [RFC7841]).
 o  For all RFCs and Internet-Drafts, it determines whether the
    "Copyright Notice" section mentions the Copyright on Code
    Components (see Section 6 of the TLP ("Text to Be Included in IETF
    Documents")).

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A.3. The "consensus" Attribute

 For some of the publication streams (see Appendix A.2), the "Status
 of This Memo" section depends on whether there was a consensus to
 publish (again, see Section 3.4 of [RFC7841]).
 The consensus attribute can be used to supply this information.  The
 acceptable values are "true" (the default) and "false"; "yes" and
 "no" from v2 are deprecated.
 The effect of this value for the various streams is:
 o  "independent": none.
 o  "IAB": mention that there was an IAB consensus.
 o  "IETF": mention that there was an IETF consensus.
 o  "IRTF": mention that there was a research group consensus (where
    the name of the research group is extracted from the <workgroup>
    element).

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Appendix B. The v3 Format and Processing Tools

 This section describes topics that are specific to v3 processing
 tools.  Note that there is some discussion of tools in the main body
 of the document as well.  For example, some elements have
 descriptions of how a processing tool might create output from the
 element.
 The expected design of the tools that will be used with v3 documents
 includes:
 o  A "prep tool" that takes a v3 document, makes many checks, adds
    and changes many attribute values, and creates a file that is a
    "prepared document".  The prepared document is a valid v3
    document.  The prep tool is described in [RFC7998].
    The prep tool is expected to have many modes:
  • RFC mode – The mode used by the RFC Editor to process the

input from one of the RFC streams and to process XML produced

       during the RFC editing process.  The restrictions on the
       canonical XML for RFCs, as well as how the non-canonical
       formats will look, are described at
       <https://www.rfc-editor.org/rse/wiki/
       doku.php?id=design:format-and-content-rfcs>.
  • Draft mode – The mode used by the Internet-Draft submission

tool. The restrictions for the XML from this mode will be

       described later.
  • Diagnostic mode – A mode that can be used by document authors

to look for errors or warnings before they submit their

       documents for publication.
  • Consolidation mode – Produces output where no external

resources are required to render the file output. This

       includes expanding the XInclude entities and DTD entities in
       place, and changing all elements that have "src" attributes
       with external links into either "data:" URI or content for the
       element, as specified in [RFC7998].
 o  Formatting tools that will create HTML, PDF, plain text, and
    possibly other output formats.  These formatters will be created
    by the IETF, but others can create such tools as well.  The IETF
    tools are expected to take prepared documents as input.

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 There may also be processing tools that are meant to run on the
 computers of authors.  These tools may be used to produce interim
 versions of the non-canonical representations so that authors can see
 how their XML might later be rendered, to create documents in
 representations different than those supported by the RFC Editor, to
 possibly create documents that are not meant to be Internet-Drafts or
 RFCs, and to convert XML that has external information into XML that
 has that external information included.
 The prep tool is expected to have clear error reporting, giving more
 context than just a line number.  For example, the error messages
 should differentiate between errors in XML and those from the v3
 format.
 In v2, the grammar was specified as a DTD.  In v3, the grammar is
 specified only as RELAX Next Generation (RNG).  This means that tools
 need to work from the RNG, not from a DTD.  Some of the features of
 the v3 grammar cannot be specified as a DTD.

B.1. Including External Text with XInclude

 All tools for the v3 format are expected to support XInclude
 [XInclude].  XInclude specifies a processing model and syntax for
 general-purpose inclusion of information that is either on the
 Internet or local to the user's computer.
 In the v3 syntax, XInclude is expressed as the <xi:include> element.
 To use this element, you need to include the "xi" namespace in the
 <rfc> element; that is, you need to specify
 xmlns:xi="http://www.w3.org/2001/XInclude"
 as one of the attributes in the <rfc> element.
 The most common way to use <xi:include> is to pull in references that
 are already formed as XML.  Currently, this can be done from
 xml2rfc.tools.ietf.org, but later this is expected to be from the RFC
 Editor.  For example, if a document has three normative references,
 all RFCs, the document might contain:
 <references>
     <xi:include href="http://xml2rfc.tools.ietf.org/public/rfc/
        bibxml/reference.RFC.2119.xml"/>
     <xi:include href="http://xml2rfc.tools.ietf.org/public/rfc/
        bibxml/reference.RFC.4869.xml"/>
     <xi:include href="http://xml2rfc.tools.ietf.org/public/rfc/
        bibxml/reference.RFC.7169.xml"/>
 </references>

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 <xi:include> can be used anywhere an XML element could be used (but
 not where free text is used).  For example, if three Internet-Drafts
 are all including a particular paragraph or section verbatim, that
 text can be kept either in a file or somewhere on the web and can be
 included with <xi:include>.  An example of pulling something from the
 local disk would be:
 <x:include href="file://home/chris/ietf/drafts/commontext.xml"/>
 In general, XInclude should be used instead of ENTITY references and
 XML Processing Instructions (PIs) that allow external inclusions.

B.2. Anchors and IDs

 People writing and reading Internet-Drafts and RFCs often want to
 make reference to specific locations in those documents.  In the case
 of RFC authors, it is common to want to reference another part of
 their document, such as "see Section 3.2 of this document."  Readers,
 on the other hand, want to reference parts of documents that they
 didn't write, such as "see Section 3.2 of RFC 6949."  The XML
 vocabulary in this document attempts to support both sets of people.
 Authors can leave anchors in a document that can later be used for
 references with the "anchor" attribute.  Anchors can be included in
 the numerous elements.  The author can then refer to that anchor in
 the "target" attribute of the <xref> element.
 Readers can refer to any element that has an "anchor" attribute by
 that attribute.  Note, however, that most of the time, elements won't
 have anchors.  In the common case, the reader wants to refer to an
 element that does not have an "anchor" attribute, but that element
 has a "pn" attribute.
 Processing tools add the "pn" attribute to many elements during
 processing.  This attribute and its value are automatically generated
 by the tool if the attribute is not there; if the attribute is
 already there, the tool may replace the value.

B.2.1. Overlapping Values

 In the HTML representation of this XML vocabulary, both anchors and
 "pn" attributes will be used in the "id" attributes of elements.
 Thus, there can be no overlap between the names entered in "anchor"
 attributes, in "slugifiedName" attributes, and those that are
 generated for the "pn" attributes.  Also, there are some values for
 the "anchor" values that are reserved for sections, and those
 sections can only have those anchor values.

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 The following rules prevent this overlap:
 o  "pn" for regular sections always has the format "s-nnn", where
    "nnn" is the section number, or the appendix identifier (which
    starts with a letter).  For example, this would be "s-2.1.3" for
    Section 2.1.3 and "s-a" for Appendix A.  For the <abstract>
    element, it is always "s-abstract".  For the <note> element, it is
    always "s-note-nnn", where "nnn" is a sequential value.  For
    sections in the <boilerplate> element, it is always
    "s-boilerplate-nnn", where "nnn" is a sequential value.
 o  "pn" for <references> elements has the format "s-nnn".  It is
    important to note that "nnn" is a number, not letters, even though
    the <references> appear in the back.  It is the number that is one
    higher than the highest top-level section number in <middle>.  If
    there are two or more <references>, "nnn" will include a dot as if
    the <references> are a subsection of a section that is numbered
    one higher than the highest top-level section number in <middle>.
 o  "pn" for <figure> elements always has the format "f-nnn", where
    "nnn" is the figure number.  For example, this would be "f-5" for
    Figure 5.
 o  "pn" for <iref> elements always has the format "i-ttt-nnn", where
    "ttt" is the slugified item (plus a hyphen and the slugified
    subitem if there is a subitem), and "nnn" is the instance of that
    item/subitem pair.  For example, this would be "i-foo-1" for
    "<iref item='foo'>" and "i-foo-bar-1" for "<iref item='foo'
    subitem='bar'>".
 o  "pn" for <table> elements always has the format "t-nnn", where
    "nnn" is the table number.  For example, this would be "t-5" for
    Table 5.
 o  "pn" for all elements not listed above always has the format
    "p-nnn-mmm", where "nnn" is the section number and "mmm" is the
    relative position in the section.  For example, this would be
    "p-2.1.3-7" for the seventh part number in Section 2.1.3.

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 o  "slugifiedName" always has the format "n-ttt", where "ttt" is the
    text of the name after slugification.  For example, this would be
    "n-protocol-overview" for the name "Protocol Overview".  The
    actual conversions done in slugification will be specified at a
    later time.
 o  Anchors must never overlap with any of the above.  The easiest way
    to assure that is to not pick an anchor name that starts with a
    single letter followed by a hyphen.  If an anchor does overlap
    with one of the types of names above, the processing tool will
    reject the document.

B.3. Attributes Controlled by the Prep Tool

 Many elements in the v3 vocabulary have new attributes whose role is
 to hold values generated by the prep tool.  These attributes can
 exist in documents that are input to the prep tool; however, any of
 these attributes might be added, removed, or changed by the prep
 tool.  Thus, it is explicitly unsafe for a document author to include
 these attributes and expect that their values will survive processing
 by the prep tool.
 The attributes that are controlled by the prep tool are:
 o  The "pn" attribute in any element -- The number for this item
    within the section.  The numbering is shared with other elements
    of a section.  The "pn" attribute is added to many block-level
    elements inside sections.
 o  <artwork> originalSrc -- This attribute is filled with the
    original value of the "src" attribute if that attribute is removed
    by the prep tool.
 o  <figure> originalSrc -- This attribute is filled with the original
    value of the "src" attribute if that attribute is removed by the
    prep tool.
 o  <name> "slugifiedName" attribute -- This attribute is filled with
    a "slugified" version of the text in the element.  This attribute
    can be used in the output formats for elements that have both
    names and numbers.
 o  <relref> "derivedLink" attribute -- This attribute is filled with
    the link that is derived from combining the URI from the reference
    and the relative part that is either a copy of the "relative"
    attribute or a section number derived from the "section"
    attribute.

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 o  <rfc> "expiresDate" attribute -- This attribute is filled with the
    date that an Internet-Draft expires.  The date is in the format
    yyyy-mm-dd.
 o  <rfc> "mode" attribute -- This attribute is filled with a string
    that indicates what mode the prep tool was in when it processed
    the XML, such as whether it was processing a file to become an
    Internet-Draft or an RFC.
 o  <rfc> "scripts" attribute -- This attribute is filled with a list
    of scripts needed to render this document.  The list is comma-
    separated, with no spaces allowed.  The order is unimportant.  The
    names come from [UAX24].  For example, if the document has Chinese
    characters in it, the value might be "Common,Latin,Han".
 o  <sourcecode> "originalSrc" attribute -- This attribute is filled
    with the original value of the "src" attribute if that attribute
    is removed by the prep tool.
 o  <xref> "derivedContent" attribute -- This attribute is filled in
    if there is no content in the <xref> element.  The value for this
    attribute is based on the value in the "displayFormat" attribute.
    Examples of how this value is filled can be found in
    Section 2.66.1.
 In addition, note that the contents of the <boilerplate> element are
 controlled by the prep tool.

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Appendix C. RELAX NG Schema

 The following is the RELAX NG schema for the v3 format.
 namespace a = "http://relaxng.org/ns/compatibility/annotations/1.0"
 # xml2rfc Version 3 grammar
 rfc =
   element rfc {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute number { text }?,
     [ a:defaultValue = "" ] attribute obsoletes { text }?,
     [ a:defaultValue = "" ] attribute updates { text }?,
     attribute category { text }?,
     attribute mode { text }?,
     [ a:defaultValue = "false" ]
     attribute consensus { "no" | "yes" | "false" | "true" }?,
     attribute seriesNo { text }?,
     attribute ipr { text }?,
     attribute iprExtract { xsd:IDREF }?,
     [ a:defaultValue = "IETF" ]
     attribute submissionType {
       "IETF" | "IAB" | "IRTF" | "independent"
     }?,
     attribute docName { text }?,
     [ a:defaultValue = "false" ]
     attribute sortRefs { "true" | "false" }?,
     [ a:defaultValue = "true" ]
     attribute symRefs { "true" | "false" }?,
     [ a:defaultValue = "true" ]
     attribute tocInclude { "true" | "false" }?,
     [ a:defaultValue = "3" ] attribute tocDepth { text }?,
     attribute prepTime { text }?,
     [ a:defaultValue = "true" ]
     attribute indexInclude { "true" | "false" }?,
     attribute version { text }?,
     [ a:defaultValue = "Common,Latin" ] attribute scripts { text }?,
     attribute expiresDate { text }?,
     link*,
     front,
     middle,
     back?
   }

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 link =
   element link {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute href { text },
     attribute rel { text }?
   }
 front =
   element front {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     title,
     seriesInfo*,
     author+,
     date?,
     area*,
     workgroup*,
     keyword*,
     abstract?,
     note*,
     boilerplate?
   }
 title =
   element title {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute abbrev { text }?,
     attribute ascii { text }?,
     text
   }
 author =
   element author {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute initials { text }?,
     attribute asciiInitials { text }?,
     attribute surname { text }?,
     attribute asciiSurname { text }?,
     attribute fullname { text }?,
     attribute role { "editor" }?,
     attribute asciiFullname { text }?,
     organization?,
     address?
   }

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 organization =
   element organization {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute abbrev { text }?,
     attribute ascii { text }?,
     text
   }
 address =
   element address {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     postal?,
     phone?,
     facsimile?,
     email?,
     uri?
   }
 postal =
   element postal {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     ((city | code | country | region | street)* | postalLine+)
   }
 street =
   element street {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute ascii { text }?,
     text
   }
 city =
   element city {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute ascii { text }?,
     text
   }

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 region =
   element region {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute ascii { text }?,
     text
   }
 code =
   element code {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute ascii { text }?,
     text
   }
 country =
   element country {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute ascii { text }?,
     text
   }
 postalLine =
   element postalLine {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute ascii { text }?,
     text
   }
 phone =
   element phone {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     text
   }
 facsimile =
   element facsimile {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     text
   }

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 email =
   element email {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute ascii { text }?,
     text
   }
 uri =
   element uri {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     text
   }
 date =
   element date {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute day { text }?,
     attribute month { text }?,
     attribute year { text }?,
     empty
   }
 area =
   element area {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     text
   }
 workgroup =
   element workgroup {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     text
   }
 keyword =
   element keyword {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     text
   }

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 abstract =
   element abstract {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     (dl | ol | t | ul)+
   }
 note =
   element note {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute title { text }?,
     attribute pn { text }?,
     [ a:defaultValue = "false" ]
     attribute removeInRFC { "true" | "false" }?,
     name?,
     (dl | ol | t | ul)+
   }
 boilerplate =
   element boilerplate {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     section+
   }
 middle =
   element middle {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     section+
   }

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 section =
   element section {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     attribute title { text }?,
     [ a:defaultValue = "true" ]
     attribute numbered { "true" | "false" }?,
     [ a:defaultValue = "default" ]
     attribute toc { "include" | "exclude" | "default" }?,
     [ a:defaultValue = "false" ]
     attribute removeInRFC { "true" | "false" }?,
     name?,
     (artwork
      | aside
      | blockquote
      | dl
      | figure
      | iref
      | ol
      | sourcecode
      | t
      | table
      | texttable
      | ul)*,
     section*
   }
 name =
   element name {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute slugifiedName { text }?,
     (text | cref | eref | relref | tt | xref)*
   }

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 t =
   element t {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     attribute hangText { text }?,
     [ a:defaultValue = "false" ]
     attribute keepWithNext { "false" | "true" }?,
     [ a:defaultValue = "false" ]
     attribute keepWithPrevious { "false" | "true" }?,
     (text
      | bcp14
      | cref
      | em
      | eref
      | iref
      | \list
      | relref
      | spanx
      | strong
      | sub
      | sup
      | tt
      | vspace
      | xref)*
   }
 aside =
   element aside {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     (artwork | dl | figure | iref | \list | ol | t | table | ul)*
   }

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 blockquote =
   element blockquote {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     attribute cite { text }?,
     attribute quotedFrom { text }?,
     ((artwork | dl | figure | ol | sourcecode | t | ul)+
      | (text
         | bcp14
         | cref
         | em
         | eref
         | iref
         | relref
         | strong
         | sub
         | sup
         | tt
         | xref)+)
   }
 \list =
   element list {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     [ a:defaultValue = "empty" ] attribute style { text }?,
     attribute hangIndent { text }?,
     attribute counter { text }?,
     attribute pn { text }?,
     t+
   }
 ol =
   element ol {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     [ a:defaultValue = "1" ] attribute type { text }?,
     [ a:defaultValue = "1" ] attribute start { text }?,
     attribute group { text }?,
     [ a:defaultValue = "normal" ]
     attribute spacing { "normal" | "compact" }?,
     attribute pn { text }?,
     li+
   }

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 ul =
   element ul {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     [ a:defaultValue = "normal" ]
     attribute spacing { "normal" | "compact" }?,
     ([ a:defaultValue = "false" ]
      attribute empty { "false" | "true" },
      attribute pn { text }?)?,
     li+
   }
 li =
   element li {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     ((artwork | dl | figure | ol | sourcecode | t | ul)+
      | (text
         | bcp14
         | cref
         | em
         | eref
         | iref
         | relref
         | strong
         | sub
         | sup
         | tt
         | xref)+)
   }
 dl =
   element dl {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     [ a:defaultValue = "normal" ]
     attribute spacing { "normal" | "compact" }?,
     [ a:defaultValue = "true" ]
     attribute hanging { "false" | "true" }?,
     attribute pn { text }?,
     (dt, dd)+
   }

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 dt =
   element dt {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     (text
      | bcp14
      | cref
      | em
      | eref
      | iref
      | relref
      | strong
      | sub
      | sup
      | tt
      | xref)*
   }
 dd =
   element dd {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     ((artwork | dl | figure | ol | sourcecode | t | ul)+
      | (text
         | bcp14
         | cref
         | em
         | eref
         | iref
         | relref
         | strong
         | sub
         | sup
         | tt
         | xref)+)
   }

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 xref =
   element xref {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute target { xsd:IDREF },
     [ a:defaultValue = "false" ]
     attribute pageno { "true" | "false" }?,
     [ a:defaultValue = "default" ]
     attribute format { "default" | "title" | "counter" | "none" }?,
     attribute derivedContent { text }?,
     text
   }
 relref =
   element relref {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute target { xsd:IDREF },
     [ a:defaultValue = "of" ]
     attribute displayFormat { "of" | "comma" | "parens" | "bare" }?,
     attribute section { text },
     attribute relative { text }?,
     attribute derivedLink { text }?,
     text
   }
 eref =
   element eref {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute target { text },
     text
   }
 iref =
   element iref {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute item { text },
     [ a:defaultValue = "" ] attribute subitem { text }?,
     [ a:defaultValue = "false" ]
     attribute primary { "true" | "false" }?,
     attribute pn { text }?,
     empty
   }

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 cref =
   element cref {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute source { text }?,
     [ a:defaultValue = "true" ]
     attribute display { "true" | "false" }?,
     (text | em | eref | relref | strong | sub | sup | tt | xref)*
   }
 tt =
   element tt {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text
      | bcp14
      | cref
      | em
      | eref
      | iref
      | relref
      | strong
      | sub
      | sup
      | xref)*
   }
 strong =
   element strong {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text
      | bcp14
      | cref
      | em
      | eref
      | iref
      | relref
      | sub
      | sup
      | tt
      | xref)*
   }

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 em =
   element em {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text
      | bcp14
      | cref
      | eref
      | iref
      | relref
      | strong
      | sub
      | sup
      | tt
      | xref)*
   }
 sub =
   element sub {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text
      | bcp14
      | cref
      | em
      | eref
      | iref
      | relref
      | strong
      | tt
      | xref)*
   }
 sup =
   element sup {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text
      | bcp14
      | cref
      | em
      | eref
      | iref
      | relref
      | strong
      | tt
      | xref)*
   }

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 spanx =
   element spanx {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     [ a:defaultValue = "preserve" ]
     attribute xml:space { "default" | "preserve" }?,
     [ a:defaultValue = "emph" ] attribute style { text }?,
     text
   }
 vspace =
   element vspace {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     [ a:defaultValue = "0" ] attribute blankLines { text }?,
     empty
   }
 figure =
   element figure {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     [ a:defaultValue = "" ] attribute title { text }?,
     [ a:defaultValue = "false" ]
     attribute suppress-title { "true" | "false" }?,
     attribute src { text }?,
     attribute originalSrc { text }?,
     [ a:defaultValue = "left" ]
     attribute align { "left" | "center" | "right" }?,
     [ a:defaultValue = "" ] attribute alt { text }?,
     [ a:defaultValue = "" ] attribute width { text }?,
     [ a:defaultValue = "" ] attribute height { text }?,
     name?,
     iref*,
     preamble?,
     (artwork | sourcecode)+,
     postamble?
   }

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 table =
   element table {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     name?,
     iref*,
     thead?,
     tbody+,
     tfoot?
   }
 preamble =
   element preamble {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text
      | bcp14
      | cref
      | em
      | eref
      | iref
      | relref
      | spanx
      | strong
      | sub
      | sup
      | tt
      | xref)*
   }

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 artwork =
   element artwork {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     attribute xml:space { text }?,
     [ a:defaultValue = "" ] attribute name { text }?,
     [ a:defaultValue = "" ] attribute type { text }?,
     attribute src { text }?,
     [ a:defaultValue = "left" ]
     attribute align { "left" | "center" | "right" }?,
     [ a:defaultValue = "" ] attribute alt { text }?,
     [ a:defaultValue = "" ] attribute width { text }?,
     [ a:defaultValue = "" ] attribute height { text }?,
     attribute originalSrc { text }?,
     (text* | svg)
   }
 # https://www.rfc-editor.org/materials/format/SVG-1.2-RFC.rnc
 sourcecode =
   element sourcecode {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     attribute pn { text }?,
     [ a:defaultValue = "" ] attribute name { text }?,
     [ a:defaultValue = "" ] attribute type { text }?,
     attribute src { text }?,
     attribute originalSrc { text }?,
     text
   }
 thead =
   element thead {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     tr+
   }
 tbody =
   element tbody {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     tr+
   }

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 tfoot =
   element tfoot {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     tr+
   }
 tr =
   element tr {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     (td | th)+
   }
 td =
   element td {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     [ a:defaultValue = "0" ] attribute colspan { text }?,
     [ a:defaultValue = "0" ] attribute rowspan { text }?,
     [ a:defaultValue = "left" ]
     attribute align { "left" | "center" | "right" }?,
     ((artwork | dl | figure | ol | sourcecode | t | ul)+
      | (text
         | bcp14
         | br
         | cref
         | em
         | eref
         | iref
         | relref
         | strong
         | sub
         | sup
         | tt
         | xref)*)
   }

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 th =
   element th {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     [ a:defaultValue = "0" ] attribute colspan { text }?,
     [ a:defaultValue = "0" ] attribute rowspan { text }?,
     [ a:defaultValue = "left" ]
     attribute align { "left" | "center" | "right" }?,
     ((artwork | dl | figure | ol | sourcecode | t | ul)+
      | (text
         | bcp14
         | br
         | cref
         | em
         | eref
         | iref
         | relref
         | strong
         | sub
         | sup
         | tt
         | xref)*)
   }
 postamble =
   element postamble {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text | cref | eref | iref | spanx | xref)*
   }

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 texttable =
   element texttable {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID }?,
     [ a:defaultValue = "" ] attribute title { text }?,
     [ a:defaultValue = "false" ]
     attribute suppress-title { "true" | "false" }?,
     [ a:defaultValue = "center" ]
     attribute align { "left" | "center" | "right" }?,
     [ a:defaultValue = "full" ]
     attribute style { "all" | "none" | "headers" | "full" }?,
     name?,
     preamble?,
     ttcol+,
     c*,
     postamble?
   }
 ttcol =
   element ttcol {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute width { text }?,
     [ a:defaultValue = "left" ]
     attribute align { "left" | "center" | "right" }?,
     (cref | eref | iref | xref | text)*
   }
 c =
   element c {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text | cref | eref | iref | spanx | xref)*
   }
 bcp14 =
   element bcp14 {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     text
   }

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 br =
   element br {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     empty
   }
 back =
   element back {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     displayreference*,
     references*,
     section*
   }
 displayreference =
   element displayreference {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute target { xsd:IDREF },
     attribute to { text }
   }
 references =
   element references {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute pn { text }?,
     attribute anchor { xsd:ID }?,
     attribute title { text }?,
     name?,
     (reference | referencegroup)*
   }
 reference =
   element reference {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID },
     attribute target { text }?,
     [ a:defaultValue = "true" ]
     attribute quoteTitle { "true" | "false" }?,
     front,
     (annotation | format | refcontent | seriesInfo)*
   }

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 referencegroup =
   element referencegroup {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute anchor { xsd:ID },
     reference+
   }
 seriesInfo =
   element seriesInfo {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute name { text },
     attribute value { text },
     attribute asciiName { text }?,
     attribute asciiValue { text }?,
     attribute status { text }?,
     [ a:defaultValue = "IETF" ]
     attribute stream { "IETF" | "IAB" | "IRTF" | "independent" }?,
     empty
   }
 format =
   element format {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     attribute target { text }?,
     attribute type { text },
     attribute octets { text }?,
     empty
   }

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 annotation =
   element annotation {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text
      | bcp14
      | cref
      | em
      | eref
      | iref
      | relref
      | spanx
      | strong
      | sub
      | sup
      | tt
      | xref)*
   }
 refcontent =
   element refcontent {
     attribute xml:base { text }?,
     attribute xml:lang { text }?,
     (text | bcp14 | em | strong | sub | sup | tt)*
   }
 start |= rfc

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Appendix D. Schema Differences from v2

 The following is a non-normative comparison of the v3 format to the
 v2 format.  A "-" indicates lines removed from the v2 schema, and a
 "+" indicates lines added to the v3 schema.
   namespace a =
   "http://relaxng.org/ns/compatibility/annotations/1.0"
 + # xml2rfc Version 3 grammar
   rfc =
     element rfc {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute number { text }?,
       [ a:defaultValue = "" ] attribute obsoletes { text }?,
       [ a:defaultValue = "" ] attribute updates { text }?,
 -     attribute category { "std" | "bcp" | "info" | "exp" |
 - "historic" }?,
 -     attribute consensus { "no" | "yes" }?,
 +     attribute category { text }?,
 +     attribute mode { text }?,
 +     [ a:defaultValue = "false" ]
 +     attribute consensus { "no" | "yes" | "false" | "true" }?,
       attribute seriesNo { text }?,
 -     attribute ipr {
 -       "full2026"
 -       | "noDerivativeWorks2026"
 -       | "none"
 -       | "full3667"
 -       | "noModification3667"
 -       | "noDerivatives3667"
 -       | "full3978"
 -       | "noModification3978"
 -       | "noDerivatives3978"
 -       | "trust200811"
 -       | "noModificationTrust200811"
 -       | "noDerivativesTrust200811"
 -       | "trust200902"
 -       | "noModificationTrust200902"
 -       | "noDerivativesTrust200902"
 -       | "pre5378Trust200902"
 -     }?,

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 +     attribute ipr { text }?,
       attribute iprExtract { xsd:IDREF }?,
       [ a:defaultValue = "IETF" ]
       attribute submissionType {
         "IETF" | "IAB" | "IRTF" | "independent"
       }?,
       attribute docName { text }?,
 -     [ a:defaultValue = "en" ] attribute xml:lang { text }?,
 +     [ a:defaultValue = "false" ]
 +     attribute sortRefs { "true" | "false" }?,
 +     [ a:defaultValue = "true" ]
 +     attribute symRefs { "true" | "false" }?,
 +     [ a:defaultValue = "true" ]
 +     attribute tocInclude { "true" | "false" }?,
 +     [ a:defaultValue = "3" ] attribute tocDepth { text }?,
 +     attribute prepTime { text }?,
 +     [ a:defaultValue = "true" ]
 +     attribute indexInclude { "true" | "false" }?,
 +     attribute version { text }?,
 +     [ a:defaultValue = "Common,Latin" ] attribute scripts { text
 + }?,
 +     attribute expiresDate { text }?,
 +     link*,
       front,
       middle,
       back?
     }

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 + link =
 +   element link {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute href { text },
 +     attribute rel { text }?
 +   }
   front =
     element front {
 -     title, author+, date, area*, workgroup*, keyword*, abstract?,
 - note*
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     title,
 +     seriesInfo*,
 +     author+,
 +     date?,
 +     area*,
 +     workgroup*,
 +     keyword*,
 +     abstract?,
 +     note*,
 +     boilerplate?
     }
   title =
     element title {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute abbrev { text }?,
 +     attribute ascii { text }?,
       text
     }
   author =
     element author {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute initials { text }?,
 +     attribute asciiInitials { text }?,
       attribute surname { text }?,
 +     attribute asciiSurname { text }?,
       attribute fullname { text }?,
       attribute role { "editor" }?,
 +     attribute asciiFullname { text }?,
       organization?,
       address?
     }

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   organization =
     element organization {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute abbrev { text }?,
 +     attribute ascii { text }?,
 +     text
 +   }
 + address =
 +   element address {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     postal?,
 +     phone?,
 +     facsimile?,
 +     email?,
 +     uri?
 +   }
 + postal =
 +   element postal {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     ((city | code | country | region | street)* | postalLine+)
 +   }
 + street =
 +   element street {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute ascii { text }?,
 +     text
 +   }
 + city =
 +   element city {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute ascii { text }?,
 +     text
 +   }
 + region =
 +   element region {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute ascii { text }?,
 +     text
 +   }

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 + code =
 +   element code {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute ascii { text }?,
 +     text
 +   }
 + country =
 +   element country {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute ascii { text }?,
 +     text
 +   }
 + postalLine =
 +   element postalLine {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute ascii { text }?,
 +     text
 +   }
 + phone =
 +   element phone {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     text
 +   }
 + facsimile =
 +   element facsimile {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     text
 +   }
 + email =
 +   element email {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute ascii { text }?,
 +     text
 +   }

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 + uri =
 +   element uri {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       text
     }
 - address = element address { postal?, phone?, facsimile?, email?,
 - uri? }
 - postal = element postal { street+, (city | region | code |
 - country)* }
 - street = element street { text }
 - city = element city { text }
 - region = element region { text }
 - code = element code { text }
 - country = element country { text }
 - phone = element phone { text }
 - facsimile = element facsimile { text }
 - email = element email { text }
 - uri = element uri { text }
   date =
     element date {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute day { text }?,
       attribute month { text }?,
       attribute year { text }?,
       empty
     }
 - area = element area { text }
 - workgroup = element workgroup { text }
 - keyword = element keyword { text }
 - abstract = element abstract { t+ }
 + area =
 +   element area {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     text
 +   }
 + workgroup =
 +   element workgroup {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     text
 +   }

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 + keyword =
 +   element keyword {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     text
 +   }
 + abstract =
 +   element abstract {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
 +     (dl | ol | t | ul)+
 +   }
   note =
     element note {
 -     attribute title { text },
 -     t+
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute title { text }?,
 +     attribute pn { text }?,
 +     [ a:defaultValue = "false" ]
 +     attribute removeInRFC { "true" | "false" }?,
 +     name?,
 +     (dl | ol | t | ul)+
 +   }
 + boilerplate =
 +   element boilerplate {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     section+
 +   }
 + middle =
 +   element middle {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     section+
     }

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  1. middle = element middle { section+ }

section =

     element section {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute anchor { xsd:ID }?,
 -     attribute title { text },
 +     attribute pn { text }?,
 +     attribute title { text }?,
 +     [ a:defaultValue = "true" ]
 +     attribute numbered { "true" | "false" }?,
       [ a:defaultValue = "default" ]
       attribute toc { "include" | "exclude" | "default" }?,
 -     (t | figure | texttable | iref)*,
 +     [ a:defaultValue = "false" ]
 +     attribute removeInRFC { "true" | "false" }?,
 +     name?,
 +     (artwork
 +      | aside
 +      | blockquote
 +      | dl
 +      | figure
 +      | iref
 +      | ol
 +      | sourcecode
 +      | t
 +      | table
 +      | texttable
 +      | ul)*,
       section*
     }

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 + name =
 +   element name {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute slugifiedName { text }?,
 +     (text | cref | eref | relref | tt | xref)*
 +   }
   t =
     element t {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
       attribute hangText { text }?,
 +     [ a:defaultValue = "false" ]
 +     attribute keepWithNext { "false" | "true" }?,
 +     [ a:defaultValue = "false" ]
 +     attribute keepWithPrevious { "false" | "true" }?,
       (text
 -      | \list
 -      | figure
 -      | xref
 +      | bcp14
 +      | cref
 +      | em
        | eref
        | iref
 -      | cref
 +      | \list
 +      | relref
        | spanx
 -      | vspace)*
 +      | strong
 +      | sub
 +      | sup
 +      | tt
 +      | vspace
 +      | xref)*
 +   }
 + aside =
 +   element aside {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
 +     (artwork | dl | figure | iref | \list | ol | t | table | ul)*
 +   }

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 + blockquote =
 +   element blockquote {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
 +     attribute cite { text }?,
 +     attribute quotedFrom { text }?,
 +     ((artwork | dl | figure | ol | sourcecode | t | ul)+
 +      | (text
 +         | bcp14
 +         | cref
 +         | em
 +         | eref
 +         | iref
 +         | relref
 +         | strong
 +         | sub
 +         | sup
 +         | tt
 +         | xref)+)
     }
   \list =
     element list {
 -     attribute style { text }?,
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     [ a:defaultValue = "empty" ] attribute style { text }?,
       attribute hangIndent { text }?,
       attribute counter { text }?,
 +     attribute pn { text }?,
       t+
     }
 + ol =
 +   element ol {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     [ a:defaultValue = "1" ] attribute type { text }?,
 +     [ a:defaultValue = "1" ] attribute start { text }?,
 +     attribute group { text }?,
 +     [ a:defaultValue = "normal" ]
 +     attribute spacing { "normal" | "compact" }?,
 +     attribute pn { text }?,
 +     li+
 +   }

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 + ul =
 +   element ul {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     [ a:defaultValue = "normal" ]
 +     attribute spacing { "normal" | "compact" }?,
 +     ([ a:defaultValue = "false" ]
 +      attribute empty { "false" | "true" },
 +      attribute pn { text }?)?,
 +     li+
 +   }
 + li =
 +   element li {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
 +     ((artwork | dl | figure | ol | sourcecode | t | ul)+
 +      | (text
 +         | bcp14
 +         | cref
 +         | em
 +         | eref
 +         | iref
 +         | relref
 +         | strong
 +         | sub
 +         | sup
 +         | tt
 +         | xref)+)
 +   }
 + dl =
 +   element dl {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     [ a:defaultValue = "normal" ]
 +     attribute spacing { "normal" | "compact" }?,
 +     [ a:defaultValue = "true" ]
 +     attribute hanging { "false" | "true" }?,
 +     attribute pn { text }?,
 +     (dt, dd)+
 +   }

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 + dt =
 +   element dt {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
 +     (text
 +      | bcp14
 +      | cref
 +      | em
 +      | eref
 +      | iref
 +      | relref
 +      | strong
 +      | sub
 +      | sup
 +      | tt
 +      | xref)*
 +   }
 + dd =
 +   element dd {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
 +     ((artwork | dl | figure | ol | sourcecode | t | ul)+
 +      | (text
 +         | bcp14
 +         | cref
 +         | em
 +         | eref
 +         | iref
 +         | relref
 +         | strong
 +         | sub
 +         | sup
 +         | tt
 +         | xref)+)
 +   }

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   xref =
     element xref {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute target { xsd:IDREF },
 -     [ a:defaultValue = "false" ] attribute pageno { "true" |
 - "false" }?,
 +     [ a:defaultValue = "false" ]
 +     attribute pageno { "true" | "false" }?,
       [ a:defaultValue = "default" ]
 -     attribute format { "counter" | "title" | "none" | "default"
 +     attribute format { "default" | "title" | "counter" | "none"
 + }?,
 +     attribute derivedContent { text }?,
 +     text
 +   }
 + relref =
 +   element relref {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute target { xsd:IDREF },
 +     [ a:defaultValue = "of" ]
 +     attribute displayFormat { "of" | "comma" | "parens" | "bare"
   }?,
 +     attribute section { text },
 +     attribute relative { text }?,
 +     attribute derivedLink { text }?,
       text
     }
   eref =
     element eref {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute target { text },
       text
     }
   iref =
     element iref {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute item { text },
       [ a:defaultValue = "" ] attribute subitem { text }?,
       [ a:defaultValue = "false" ]
       attribute primary { "true" | "false" }?,
 +     attribute pn { text }?,
       empty
     }

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   cref =
     element cref {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute anchor { xsd:ID }?,
       attribute source { text }?,
 -     text
 +     [ a:defaultValue = "true" ]
 +     attribute display { "true" | "false" }?,
 +     (text | em | eref | relref | strong | sub | sup | tt | xref)*
 +   }
 + tt =
 +   element tt {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text
 +      | bcp14
 +      | cref
 +      | em
 +      | eref
 +      | iref
 +      | relref
 +      | strong
 +      | sub
 +      | sup
 +      | xref)*
 +   }
 + strong =
 +   element strong {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text
 +      | bcp14
 +      | cref
 +      | em
 +      | eref
 +      | iref
 +      | relref
 +      | sub
 +      | sup
 +      | tt
 +      | xref)*
 +   }

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 + em =
 +   element em {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text
 +      | bcp14
 +      | cref
 +      | eref
 +      | iref
 +      | relref
 +      | strong
 +      | sub
 +      | sup
 +      | tt
 +      | xref)*
 +   }
 + sub =
 +   element sub {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text
 +      | bcp14
 +      | cref
 +      | em
 +      | eref
 +      | iref
 +      | relref
 +      | strong
 +      | tt
 +      | xref)*
 +   }
 + sup =
 +   element sup {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text
 +      | bcp14
 +      | cref
 +      | em
 +      | eref
 +      | iref
 +      | relref
 +      | strong
 +      | tt
 +      | xref)*
     }

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   spanx =
     element spanx {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       [ a:defaultValue = "preserve" ]
       attribute xml:space { "default" | "preserve" }?,
       [ a:defaultValue = "emph" ] attribute style { text }?,
       text
     }
   vspace =
     element vspace {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       [ a:defaultValue = "0" ] attribute blankLines { text }?,
       empty
     }
   figure =
     element figure {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
       [ a:defaultValue = "" ] attribute title { text }?,
       [ a:defaultValue = "false" ]
       attribute suppress-title { "true" | "false" }?,
       attribute src { text }?,
 +     attribute originalSrc { text }?,
       [ a:defaultValue = "left" ]
       attribute align { "left" | "center" | "right" }?,
       [ a:defaultValue = "" ] attribute alt { text }?,
       [ a:defaultValue = "" ] attribute width { text }?,
       [ a:defaultValue = "" ] attribute height { text }?,
 +     name?,
       iref*,
       preamble?,
 -     artwork,
 +     (artwork | sourcecode)+,
       postamble?
     }

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 + table =
 +   element table {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
 +     name?,
 +     iref*,
 +     thead?,
 +     tbody+,
 +     tfoot?
 +   }
   preamble =
 -   element preamble { (text | xref | eref | iref | cref | spanx)* }
 +   element preamble {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text
 +      | bcp14
 +      | cref
 +      | em
 +      | eref
 +      | iref
 +      | relref
 +      | spanx
 +      | strong
 +      | sub
 +      | sup
 +      | tt
 +      | xref)*
 +   }

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   artwork =
     element artwork {
 -     [ a:defaultValue = "preserve" ]
 -     attribute xml:space { "default" | "preserve" }?,
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
 +     attribute xml:space { text }?,
       [ a:defaultValue = "" ] attribute name { text }?,
       [ a:defaultValue = "" ] attribute type { text }?,
       attribute src { text }?,
       [ a:defaultValue = "left" ]
       attribute align { "left" | "center" | "right" }?,
       [ a:defaultValue = "" ] attribute alt { text }?,
       [ a:defaultValue = "" ] attribute width { text }?,
       [ a:defaultValue = "" ] attribute height { text }?,
 -     text*
 +     attribute originalSrc { text }?,
 +     (text* | svg)
 +   }
 + # https://www.rfc-editor.org/materials/format/SVG-1.2-RFC.rnc
 + sourcecode =
 +   element sourcecode {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute pn { text }?,
 +     [ a:defaultValue = "" ] attribute name { text }?,
 +     [ a:defaultValue = "" ] attribute type { text }?,
 +     attribute src { text }?,
 +     attribute originalSrc { text }?,
 +     text
 +   }
 + thead =
 +   element thead {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     tr+
 +   }
 + tbody =
 +   element tbody {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     tr+
 +   }

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 + tfoot =
 +   element tfoot {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     tr+
 +   }
 + tr =
 +   element tr {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     (td | th)+
 +   }
 + td =
 +   element td {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     [ a:defaultValue = "0" ] attribute colspan { text }?,
 +     [ a:defaultValue = "0" ] attribute rowspan { text }?,
 +     [ a:defaultValue = "left" ]
 +     attribute align { "left" | "center" | "right" }?,
 +     ((artwork | dl | figure | ol | sourcecode | t | ul)+
 +      | (text
 +         | bcp14
 +         | br
 +         | cref
 +         | em
 +         | eref
 +         | iref
 +         | relref
 +         | strong
 +         | sub
 +         | sup
 +         | tt
 +         | xref)*)
 +   }

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 + th =
 +   element th {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID }?,
 +     [ a:defaultValue = "0" ] attribute colspan { text }?,
 +     [ a:defaultValue = "0" ] attribute rowspan { text }?,
 +     [ a:defaultValue = "left" ]
 +     attribute align { "left" | "center" | "right" }?,
 +     ((artwork | dl | figure | ol | sourcecode | t | ul)+
 +      | (text
 +         | bcp14
 +         | br
 +         | cref
 +         | em
 +         | eref
 +         | iref
 +         | relref
 +         | strong
 +         | sub
 +         | sup
 +         | tt
 +         | xref)*)
     }
   postamble =
 -   element postamble { (text | xref | eref | iref | cref | spanx)*
 +   element postamble {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text | cref | eref | iref | spanx | xref)*
   }

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   texttable =
     element texttable {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute anchor { xsd:ID }?,
       [ a:defaultValue = "" ] attribute title { text }?,
       [ a:defaultValue = "false" ]
       attribute suppress-title { "true" | "false" }?,
       [ a:defaultValue = "center" ]
       attribute align { "left" | "center" | "right" }?,
       [ a:defaultValue = "full" ]
       attribute style { "all" | "none" | "headers" | "full" }?,
 +     name?,
       preamble?,
       ttcol+,
       c*,
       postamble?
     }
   ttcol =
     element ttcol {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute width { text }?,
       [ a:defaultValue = "left" ]
       attribute align { "left" | "center" | "right" }?,
 +     (cref | eref | iref | xref | text)*
 +   }
 + c =
 +   element c {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text | cref | eref | iref | spanx | xref)*
 +   }
 + bcp14 =
 +   element bcp14 {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       text
     }
 - c = element c { (text | xref | eref | iref | cref | spanx)* }
 - back = element back { references*, section* }
 + br =
 +   element br {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     empty
 +   }

Hoffman Informational [Page 147] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

 + back =
 +   element back {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     displayreference*,
 +     references*,
 +     section*
 +   }
 + displayreference =
 +   element displayreference {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute target { xsd:IDREF },
 +     attribute to { text }
 +   }
   references =
     element references {
 -     [ a:defaultValue = "References" ] attribute title { text }?,
 -     reference+
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute pn { text }?,
 +     attribute anchor { xsd:ID }?,
 +     attribute title { text }?,
 +     name?,
 +     (reference | referencegroup)*
     }
   reference =
     element reference {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute anchor { xsd:ID },
       attribute target { text }?,
 +     [ a:defaultValue = "true" ]
 +     attribute quoteTitle { "true" | "false" }?,
       front,
 -     seriesInfo*,
 -     format*,
 -     annotation*
 +     (annotation | format | refcontent | seriesInfo)*
 +   }

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 + referencegroup =
 +   element referencegroup {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     attribute anchor { xsd:ID },
 +     reference+
     }
   seriesInfo =
     element seriesInfo {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute name { text },
       attribute value { text },
 +     attribute asciiName { text }?,
 +     attribute asciiValue { text }?,
 +     attribute status { text }?,
 +     [ a:defaultValue = "IETF" ]
 +     attribute stream { "IETF" | "IAB" | "IRTF" | "independent" }?,
       empty
     }
   format =
     element format {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
       attribute target { text }?,
       attribute type { text },
       attribute octets { text }?,
       empty
     }

Hoffman Informational [Page 149] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

   annotation =
 -   element annotation { (text | xref | eref | iref | cref |
 - spanx)* }
 - start = rfc
 +   element annotation {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text
 +      | bcp14
 +      | cref
 +      | em
 +      | eref
 +      | iref
 +      | relref
 +      | spanx
 +      | strong
 +      | sub
 +      | sup
 +      | tt
 +      | xref)*
 +   }
 + refcontent =
 +   element refcontent {
 +     attribute xml:base { text }?,
 +     attribute xml:lang { text }?,
 +     (text | bcp14 | em | strong | sub | sup | tt)*
 +   }
 + start |= rfc

Hoffman Informational [Page 150] RFC 7991 The "xml2rfc" Version 3 Vocabulary December 2016

IAB Members at the Time of Approval

 The IAB members at the time this memo was approved were
 (in alphabetical order):
    Jari Arkko
    Ralph Droms
    Ted Hardie
    Joe Hildebrand
    Russ Housley
    Lee Howard
    Erik Nordmark
    Robert Sparks
    Andrew Sullivan
    Dave Thaler
    Martin Thomson
    Brian Trammell
    Suzanne Woolf

Acknowledgements

 Thanks to everybody who reviewed this document and provided feedback
 and/or specification text.  Thanks especially go to Julian Reschke
 for editing [RFC7749] and those who provided feedback on that
 document.
 We also thank Marshall T. Rose for both the original design and the
 reference implementation of the "xml2rfc" processor.

Author's Address

 Paul Hoffman
 ICANN
 Email: paul.hoffman@icann.org

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/data/webs/external/dokuwiki/data/pages/rfc/rfc7991.txt · Last modified: 2016/12/16 15:29 (external edit)