draft-ietf-netmod-artwork-folding-00.txt   draft-ietf-netmod-artwork-folding-01.txt 
NETMOD Working Group K. Watsen NETMOD Working Group K. Watsen
Internet-Draft Juniper Networks Internet-Draft Watsen Networks
Intended status: Best Current Practice Q. Wu Intended status: Best Current Practice Q. Wu
Expires: May 9, 2019 Huawei Technologies Expires: September 11, 2019 Huawei Technologies
A. Farrel A. Farrel
Old Dog Consulting Old Dog Consulting
B. Claise B. Claise
Cisco Systems, Inc. Cisco Systems, Inc.
November 5, 2018 March 10, 2019
Handling Long Lines in Artwork in Internet-Drafts and RFCs Handling Long Lines in Inclusions in Internet-Drafts and RFCs
draft-ietf-netmod-artwork-folding-00 draft-ietf-netmod-artwork-folding-01
Abstract Abstract
This document introduces a simple and yet time-proven strategy for This document introduces a simple and yet time-proven strategy for
handling long lines in artwork in drafts using a backslash ('\') handling long lines in inclusions in drafts using a backslash ('\')
character where line-folding has occurred. The strategy works on any character where line-folding has occurred. The strategy works on any
text based artwork, but is primarily intended for sample text and text-based content, but is primarily intended for a structured
formatted examples and code, rather than for graphical artwork. The sequence of lines, such as would be referenced by the <sourcecode>
approach produces consistent results regardless of the content and element defined in Section 2.48 of RFC 7991, rather than for two-
uses a per-artwork header. The strategy is both self-documenting and dimensional imagery, such as would be referenced by the <artwork>
enables automated reconstitution of the original artwork. element defined in Section 2.5 of RFC 7991. The approach produces
consistent results, regardless of the content, that is both self-
documenting and enables automated reconstitution of the original
content.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 9, 2019. This Internet-Draft will expire on September 11, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Applicability Statement . . . . . . . . . . . . . . . . . . . 3
3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
3.1. Automated Folding of Long Lines in Artwork . . . . . . . 3 4. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Automated Reconstitution of Original Artwork . . . . . . 4 4.1. Automated Folding of Long Lines in Text Content . . . . . 4
4. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. Automated Reconstitution of the Original Text Content . . 4
4.1. Not Recommended for Graphical Artwork . . . . . . . . . . 4 5. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Doesn't Work as Well as Format-Specific Options . . . . . 4 5.1. Not Recommended for Graphical Artwork . . . . . . . . . . 5
5. Folded Structure . . . . . . . . . . . . . . . . . . . . . . 5 5.2. Doesn't Work as Well as Format-Specific Options . . . . . 5
5.1. Header . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Folded Structure . . . . . . . . . . . . . . . . . . . . . . 5
5.2. Body . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6.1. Header . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.2. Body . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Automated Folding . . . . . . . . . . . . . . . . . . . . 6 7. Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1.1. Manual Folding . . . . . . . . . . . . . . . . . . . 7 7.1. Automated Folding . . . . . . . . . . . . . . . . . . . . 6
6.2. Automated Unfolding . . . . . . . . . . . . . . . . . . . 7 7.1.1. Manual Folding . . . . . . . . . . . . . . . . . . . 7
7. Considerations for xml2rfc v3 . . . . . . . . . . . . . . . . 8 7.2. Automated Unfolding . . . . . . . . . . . . . . . . . . . 8
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Simple Example Showing Boundary Conditions . . . . . . . 8 8.1. Simple Example Showing Boundary Conditions . . . . . . . 9
8.2. Example Showing Multiple Wraps of a Single Line . . . . . 9 8.2. Example Showing Multiple Wraps of a Single Line . . . . . 9
8.3. Example With Native Backslash . . . . . . . . . . . . . . 9 8.3. Example With Native Backslash . . . . . . . . . . . . . . 10
8.4. Example With Native Whitespace . . . . . . . . . . . . . 9 8.4. Example With Native Whitespace . . . . . . . . . . . . . 10
8.5. Example of Manual Wrapping . . . . . . . . . . . . . . . 9 8.5. Example of Manual Wrapping . . . . . . . . . . . . . . . 10
9. Security Considerations . . . . . . . . . . . . . . . . . . . 10 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
11.1. Normative References . . . . . . . . . . . . . . . . . . 10 11.1. Normative References . . . . . . . . . . . . . . . . . . 13
11.2. Informative References . . . . . . . . . . . . . . . . . 10 11.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. POSIX Shell Script . . . . . . . . . . . . . . . . . 12 Appendix A. POSIX Shell Script . . . . . . . . . . . . . . . . . 15
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 16 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
[RFC7994]sets out the requirements for plain-text RFCs and states [RFC7994] sets out the requirements for plain-text RFCs and states
that each line of an RFC (and hence of an Internet-Draft) must be that each line of an RFC (and hence of an Internet-Draft) must be
limited to 72 characters followed by the character sequence that limited to 72 characters followed by the character sequence that
denotes an end-of-line (EOL). denotes an end-of-line (EOL).
Internet-Drafts and RFCs often include example text or code Internet-Drafts and RFCs often include example text or code
fragments. In order to render the formatting of such text it is fragments. In order to render the formatting of such text it is
usually presented as a figure using the "<artwork>" element in the usually presented as a figure using the "<sourcecode>" element in the
source XML. Many times the example text or code exceeds the 72 source XML. Many times the example text or code exceeds the 72
character line-length limit and the "xml2rfc" utility does not character line-length limit and the `xml2rfc` utility does not
attempt to wrap the content of artwork, simply issuing a warning attempt to wrap the content of such inclusions, simply issuing a
whenever artwork lines exceed 69 characters. According to the RFC warning whenever lines exceed 69 characters. According to the RFC
Editor, there is currently no convention in place for how to handle Editor, there is currently no convention in place for how to handle
long lines, other than advising authors to clearly indicate what long lines, other than advising authors to clearly indicate what
manipulation has occurred. manipulation has occurred.
This document introduces a simple and yet time-proven strategy for This document introduces a simple and yet time-proven strategy for
handling long lines using a backslash ('\') character where line- handling long lines in inclusions in drafts using a backslash ('\')
folding has occurred. The strategy works on any text based artwork, character where line-folding has occurred. The strategy works on any
but is primarily intended for sample text and formatted examples and text based inclusion, but is primarily intended for a structured
code, rather than for graphical artwork. The approach produces sequence of lines, such as would be referenced by the <sourcecode>
consistent results regardless of the content and uses a per-artwork element defined in Section 2.48 of [RFC7991], rather than for two-
header. The strategy is both self-documenting and enables automated dimensional imagery, such as would be referenced by the <artwork>
reconstitution of the original artwork. element defined in Section 2.5 of [RFC7991]. The approach produces
consistent results, regardless of the content, that is both self-
documenting and enables automated reconstitution of the original
content.
Note that text files are represent as lines having their first Note that text files are represent as lines having their first
character in column 1, and a line length of N where the last character in column 1, and a line length of N where the last
character is in the Nth column and is immediately followed by an end character is in the Nth column and is immediately followed by an end
of line character sequence. of line character sequence.
2. Requirements Language 2. Applicability Statement
The format and algorithm defined in this document may be used in any
context, whether for IETF documents or in other situations where
structured folding is desired.
Within the IETF, this work is primarily targeted to xml2rfc v3
<sourcecode> element (Section 2.48 of [RFC7991]) and xml2rfc v2
<artwork> element (Section 2.5 of [RFC7749]) that, for lack of a
better option, is currently used for both source code and artwork.
This work may be also be used for the xml2rfc v3 <artwork> element
(Section 2.5 of [RFC7991]) but, as described in Section 5.1, it is
generally not recommended.
3. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Goals 4. Goals
3.1. Automated Folding of Long Lines in Artwork 4.1. Automated Folding of Long Lines in Text Content
Automated folding of long lines is needed in order to support draft Automated folding of long lines is needed in order to support draft
compilations that entail a) validation of source input files (e.g., compilations that entail a) validation of source input files (e.g.,
XML, JSON, ABNF, ASN.1) and/or b) dynamic generation of output, using XML, JSON, ABNF, ASN.1) and/or b) dynamic generation of output, using
a tool that doesn't observe line lengths, that is stitched into the a tool that doesn't observe line lengths, that is stitched into the
final document to be submitted. final document to be submitted.
Generally, in order for tooling to be able to process input files, Generally, in order for tooling to be able to process input files,
the files must be in their original/natural state, which may include the files must be in their original/natural state, which may include
having some long lines. Thus, these source files need to be modified having some long lines. Thus, these source files need to be modified
before inclusion in the document in order to satisfy the line length before inclusion in the document in order to satisfy the line length
limits. This modification SHOULD be automated to reduce effort and limits. This modification SHOULD be automated to reduce effort and
errors resulting from manual effort. errors resulting from manual effort.
Similarly, dynamically generated output (e.g., tree diagrams) must Similarly, dynamically generated output (e.g., tree diagrams) must
also be modified, if necessary, in order for the resulting document also be modified, if necessary, in order for the resulting document
to satisfy the line length limits. When needed, this effort again to satisfy the line length limits. When needed, this effort again
SHOULD be automated to reduce effort and errors resulting from manual SHOULD be automated to reduce effort and errors resulting from manual
effort. effort.
3.2. Automated Reconstitution of Original Artwork 4.2. Automated Reconstitution of the Original Text Content
Automated reconstitution of the original artwork is needed to support Automated reconstitution of the original content is needed to support
validation of artwork extracted from documents. YANG [RFC7950] validation of artwork extracted from documents. YANG [RFC7950]
modules are already extracted from Internet-Drafts and validated as modules are already extracted from Internet-Drafts and validated as
part of the draft-submission process. Additionally, there has been part of the draft-submission process. Additionally, there has been
some discussion regarding needing to do the same for example YANG some discussion regarding needing to do the same for instance
fragments contained within Internet-Drafts ([yang-doctors-thread]). examples (i.e., XML/JSON documents) contained within Internet-Drafts
Thus, it SHOULD be possible to mechanically reconstitute artwork in ([yang-doctors-thread]). Thus, it SHOULD be possible to mechanically
order to satisfy the tooling input parsers. reconstitute the original text content in order to satisfy tooling
input parsers.
4. Limitations
4.1. Not Recommended for Graphical Artwork 5. Limitations
5.1. Not Recommended for Graphical Artwork
While the solution presented in this document will work on any kind While the solution presented in this document will work on any kind
of text-based artwork, it is most useful on artwork that represents of text-based content, it is most useful on content that represents
sourcecode (XML, JSON, etc.) or, more generally, on artwork that has source code (XML, JSON, etc.) or, more generally, on content that has
not been laid out in two dimensions (e.g., diagrams). not been laid out in two dimensions (e.g., diagrams).
Fundamentally, the issue is whether the artwork remains readable once Fundamentally, the issue is whether the text content remains readable
folded. Artwork that is unpredictable is especially susceptible to once folded. Text content that is unpredictable is especially
looking bad when folded; falling into this category are most UML susceptible to looking bad when folded; falling into this category
diagrams. are most UML diagrams, YANG tree diagrams, and ASCII art in general.
It is NOT RECOMMENDED to use the solution presented in this document It is NOT RECOMMENDED to use the solution presented in this document
on graphical artwork. on graphical artwork.
4.2. Doesn't Work as Well as Format-Specific Options 5.2. Doesn't Work as Well as Format-Specific Options
The solution presented in this document works generically for all The solution presented in this document works generically for all
artwork, as it only views artwork as plain text. However, various text-based content, as it only views content as plain text. However,
formats sometimes have built-in mechanisms that can be used to various formats sometimes have built-in mechanisms that are better
prevent long lines. suited to prevent long lines.
For instance, both the `pyang` and `yanglint` utilities have the For instance, both the `pyang` and `yanglint` utilities have the
command line option "--tree-line-length" that can be used to indicate command line option "--tree-line-length" that can be used to indicate
a desired maximum line length for when generating tree diagrams a desired maximum line length for when generating tree diagrams
[RFC8340]. [RFC8340].
In another example, some source formats (e.g., YANG [RFC7950]) allow In another example, some source formats (e.g., YANG [RFC7950]) allow
any quoted string to be broken up into substrings separated by a any quoted string to be broken up into substrings separated by a
concatenation character (e.g., '+'), any of which can be on a concatenation character (e.g., '+'), any of which can be on a
different line. different line.
In yet another example, some languages allow factoring chunks of code In yet another example, some languages allow factoring blocks of code
into call outs, such as functions. Using such call outs is into call outs, such as functions. Using such call outs is
especially helpful when in some deeply-nested code, as they typically especially helpful when in some deeply-nested code, as they typically
reset the indentation back to the first column. reset the indentation back to the first column.
As such, it is RECOMMENDED that authors do as much as possible within It is RECOMMENDED that authors do as much as possible within the
the selected format to avoid long lines. selected format to avoid long lines.
5. Folded Structure 6. Folded Structure
Artwork that has been folded as specified by this document MUST Text content that has been folded as specified by this document MUST
contain the following structure. contain the following structure.
5.1. Header 6.1. Header
The header is two lines long. The header is two lines long.
The first line is the following 46-character string that MAY be The first line is the following 46-character string that MAY be
surrounded by any number of printable characters. This first line surrounded by any number of printable characters. This first line
cannot itself be folded. cannot itself be folded.
NOTE: '\\' line wrapping per BCP XX (RFC XXXX) NOTE: '\\' line wrapping per BCP XX (RFC XXXX)
[Note to RFC Editor: Please replace XX and XXXX with the numbers [Note to RFC Editor: Please replace XX and XXXX with the numbers
assigned to this document and delete this note. Please make this assigned to this document and delete this note. Please make this
change in multiple places in this document.] change in multiple places in this document.]
The second line is a blank line. This line provides visual The second line is a blank line. This line provides visual
separation for readability. separation for readability.
5.2. Body 6.2. Body
The character encoding is the same as described in Section 2 of The character encoding is the same as described in Section 2 of
[RFC7994], except that, per [RFC7991], tab characters are prohibited. [RFC7994], except that, per [RFC7991], tab characters are prohibited.
Lines that have a backslash ('\') occurring as the last character in Lines that have a backslash ('\') occurring as the last character in
a line immediately followed by the end of line character sequence, a line immediately followed by the end of line character sequence,
when the subsequent line starts with a backslash ('\') as the first when the subsequent line starts with a backslash ('\') as the first
non-space (' ') character, are considered "folded". non-space (' ') character, are considered "folded".
Really long lines may be folded multiple times. Really long lines may be folded multiple times.
6. Algorithm 7. Algorithm
6.1. Automated Folding This section describes the processes for folding and unfolding long
lines when they are encountered in a single instance of text content.
It is assumed that another process inserts/extracts the individual
text content instances to/from an Internet-Draft or RFC. For
example, the `xiax` utility [xiax] does just this.
Determine the desired maximum line length from input. If no value is 7.1. Automated Folding
explicitly specified, the value "69" SHOULD be used.
Determine the desired maximum line length from input to the automated
line-wrapping process, such as from a command line parameter. If no
value is explicitly specified, the value "69" SHOULD be used.
Ensure that the desired maximum line length is not less than the Ensure that the desired maximum line length is not less than the
minimum header, which is 46 characters. If the desired maximum line minimum header, which is 46 characters. If the desired maximum line
length is less than this minimum, exit (this artwork can not be length is less than this minimum, exit (this text-based content
folded). cannot be folded).
Scan the artwork to see if any line exceeds the desired maximum. If Scan the text content for horizontal tab characters. If any
no line exceeds the desired maximum, exit (this artwork does not need horizontal tab characters appear, either resolve them to space
to be folded). characters or exit, forcing the input provider to convert them to
space characters themselves first.
Scan the artwork for horizontal tab characters. If any horizontal Scan the text content to see if any line exceeds the desired maximum.
tab characters appear, either resolve them to space characters or If no line exceeds the desired maximum, exit (this text content does
exit, forcing the input provider to convert them to space characters not need to be folded).
themselves first.
Scan the artwork to ensure no existing lines already end with a Scan the text content to ensure no existing lines already end with a
backslash ('\') character when the subsequent line starts with a backslash ('\') character when the subsequent line starts with a
backslash ('\') character as the first non-space (' ') character, as backslash ('\') character as the first non-space (' ') character, as
this would lead to an ambiguous result. If such a line is found, this would lead to an ambiguous result. If such a line is found,
exit (this artwork cannot be folded). exit (this text content cannot be folded).
For each line in the artwork, from top-to-bottom, if the line exceeds If this text content needs to and can be folded, insert the header as
the desired maximum, then fold the line at the desired maximum column described in Section 6.1.
by 1) inserting the character backslash ('\') character at the
maximum column, 2) inserting the end of line character sequence, For each line in the text content, from top-to-bottom, if the line
inserting any number of space (' ') characters, and 4) inserting a exceeds the desired maximum, then fold the line at the desired
further backslash ('\') character. maximum column by 1) inserting the character backslash ('\')
character at the maximum column, 2) inserting the end of line
character sequence, inserting any number of space (' ') characters,
and 4) inserting a further backslash ('\') character.
The result of this previous operation is that the next line starts The result of this previous operation is that the next line starts
with an arbitrary number of space (' ') characters, followed by a with an arbitrary number of space (' ') characters, followed by a
backslash ('\') character, immediately followed by the character that backslash ('\') character, immediately followed by the character that
was previously in the maximum column. was previously in the maximum column.
Continue in this manner until reaching the end of the artwork. Note Continue in this manner until reaching the end of the text content.
that this algorithm naturally addresses the case where the remainder Note that this algorithm naturally addresses the case where the
of a folded line is still longer than the desired maximum, and hence remainder of a folded line is still longer than the desired maximum,
needs to be folded again, ad infinitum. and hence needs to be folded again, ad infinitum.
6.1.1. Manual Folding The process described in this section is illustrated by the
"fold_it()" function in Appendix A.
7.1.1. Manual Folding
Authors may choose to fold text examples and source code by hand to Authors may choose to fold text examples and source code by hand to
produce a document that is more pleasant for a human reader but which produce a text content that is more pleasant for a human reader but
can still be automatically unfolded (as described in Section 6.2) to which can still be automatically unfolded (as described in
produce single lines that are longer than the maximum document line Section 7.2) to produce single lines that are longer than the maximum
length. document line length.
For example, an author may choose to make the fold at convenient gaps For example, an author may choose to make the fold at convenient gaps
between words such that the backslash is placed in a lower column between words such that the backslash is placed in a lower column
number than the artwork's maximum column value. number than the text content's maximum column value.
Additionally, an author may choose to indent the start of a Additionally, an author may choose to indent the start of a
continuation line by inserting space characters before the line continuation line by inserting space characters before the line
continuation marker backslash character. continuation marker backslash character.
Manual folding may also help handle the cases that cannot be Manual folding may also help handle the cases that cannot be
automatically folded as described in Section 6. automatically folded as described in Section 7.
6.2. Automated Unfolding Authors MUST produce a result that adheres to the structure described
in Section 6.
7.2. Automated Unfolding
All unfolding is assumed to be automated although a reader will All unfolding is assumed to be automated although a reader will
mentally perform the act of unfolding the text to understand the true mentally perform the act of unfolding the text to understand the true
nature of the artwork or source code. nature of the original text content.
Scan the beginning of the artwork for the header described in Scan the beginning of the text content for the header described in
Section 5.1. If the header is not present, starting on the first Section 6.1. If the header is not present, starting on the first
line of the artwork, exit (this artwork does not need to be line of the text content, exit (this artwork does not need to be
unfolded). unfolded).
Remove the 2-line header from the artwork. Remove the 2-line header from the text content.
For each line in the artwork, from top-to-bottom, if the line has a For each line in the text content, from top-to-bottom, if the line
backslash ('\') character immediately followed by the end of line has a backslash ('\') character immediately followed by the end of
character sequence, and if the next line has a backslash ('\') line character sequence, and if the next line has a backslash ('\')
character as the first non-space (' ') character, then the lines can character as the first non-space (' ') character, then the lines can
be unfolded. Remove the first backslash ('\') character, the end of be unfolded. Remove the first backslash ('\') character, the end of
line character sequence, any leading space (' ') characters, and the line character sequence, any leading space (' ') characters, and the
second backslash ('\') character, which will bring up the next line. second backslash ('\') character, which will bring up the next line.
Then continue to scan each line in the artwork starting with the Then continue to scan each line in the text content starting with the
current line (in case it was multiply folded). current line (in case it was multiply folded).
Continue in this manner until reaching the end of the artwork. Continue in this manner until reaching the end of the text content.
7. Considerations for xml2rfc v3
[RFC7991] introduces the vocabulary for version 3 of the xml2rfc
tool. This includes a new element, "<sourcecode>" used to present
sourcecode examples and fragments and to distinguish them from
general artwork and in particular figures and graphics.
The folding and unfolding described in this document is applicable to The process described in this section is illustrated by the
the "<artwork>" element in both v2 and v3 of xml2rfc, and is equally "unfold_it()" function in Appendix A.
applicable to the "<sourcecode>" element in xml2rfc v3.
8. Examples 8. Examples
The following self-documenting examples illustrate a folded document. The following self-documenting examples illustrate folded text-based
content.
The source artwork cannot be presented here, as it would again need The source text content cannot be presented here, as it would again
to be folded. Alas, only the result can be provided. need to be folded. Alas, only the result can be provided.
The examples in Sections 8.1 through 8.4 were automatically folded on The examples in Sections 8.1 through 8.4 were automatically folded on
column 69, the default value. Section 8.5 shows an example of manual column 69, the default value. Section 8.5 shows an example of manual
folding. folding.
8.1. Simple Example Showing Boundary Conditions 8.1. Simple Example Showing Boundary Conditions
This example illustrates a boundary condition test using numbers for This example illustrates a boundary condition test using numbers for
counting purposes. The input contains 5 lines, each line one counting purposes. The input contains 5 lines, each line one
character longer than the previous. character longer than the previous.
skipping to change at page 10, line 5 skipping to change at page 10, line 32
\ white space." \ white space."
8.5. Example of Manual Wrapping 8.5. Example of Manual Wrapping
This example was manually wrapped to cause the folding to occur after This example was manually wrapped to cause the folding to occur after
each term, putting each term on its own line. Indentation is used to each term, putting each term on its own line. Indentation is used to
additionally improve readability. Also note that the mandatory additionally improve readability. Also note that the mandatory
header is surrounded by different printable characters than shown in header is surrounded by different printable characters than shown in
the other examples. the other examples.
[NOTE: '\\' line wrapping per BCP XX (RFC XXXX)] ===== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) =====
<request>::= <RP> \ <yang-library
\<END-POINTS> \ xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"
\[<LSPA>] \ xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
\[<BANDWIDTH>] \
\[<metric-list>] \ <module-set>
\[<RRO>[<BANDWIDTH>]] \ <name>config-modules</name>
\[<IRO>] \ <module>
\[<LOAD-BALANCING>] <name>ietf-interfaces</name>
<revision>2018-02-20</revision>
<namespace>\
\urn:ietf:params:xml:ns:yang:ietf-interfaces\
\</namespace>
</module>
<module>
<name>ietf-ip</name>
<revision>2018-02-22</revision>
<namespace>\
\urn:ietf:params:xml:ns:yang:ietf-ip\
\</namespace>
</module>
<import-only-module>
<name>ietf-yang-types</name>
<revision>2013-07-15</revision>
<namespace>\
\urn:ietf:params:xml:ns:yang:ietf-yang-types\
\</namespace>
</import-only-module>
<import-only-module>
<name>ietf-inet-types</name>
<revision>2013-07-15</revision>
<namespace>\
\urn:ietf:params:xml:ns:yang:ietf-inet-types\
\</namespace>
</import-only-module>
</module-set>
<schema>
<name>config-schema</name>
<module-set>config-modules</module-set>
</schema>
<schema>
<name>state-schema</name>
<module-set>config-modules</module-set>
<module-set>state-modules</module-set>
</schema>
<datastore>
<name>ds:startup</name>
<schema>config-schema</schema>
</datastore>
<datastore>
<name>ds:running</name>
<schema>config-schema</schema>
</datastore>
<datastore>
<name>ds:operational</name>
<schema>state-schema</schema>
</datastore>
<content-id>75a43df9bd56b92aacc156a2958fbe12312fb285</content-id>
</yang-library>
The manual folding produces a more readable result than the following The manual folding produces a more readable result than the following
equivalent folding that contains no indentation. equivalent folding that contains no indentation.
========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) =========== ========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) ===========
<yang-library
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
<request>::= <RP> <END-POINTS> [<LSPA>] [<BANDWIDTH>] [<metric-list>\ <module-set>
\] [<RRO>[<BANDWIDTH>]] [<IRO>] [<LOAD-BALANCING>] <name>config-modules</name>
<module>
<name>ietf-interfaces</name>
<revision>2018-02-20</revision>
<namespace>urn:ietf:params:xml:ns:yang:ietf-interfaces</namesp\
\ace>
</module>
<module>
<name>ietf-ip</name>
<revision>2018-02-22</revision>
<namespace>urn:ietf:params:xml:ns:yang:ietf-ip</namespace>
</module>
<import-only-module>
<name>ietf-yang-types</name>
<revision>2013-07-15</revision>
<namespace>urn:ietf:params:xml:ns:yang:ietf-yang-types</namesp\
\ace>
</import-only-module>
<import-only-module>
<name>ietf-inet-types</name>
<revision>2013-07-15</revision>
<namespace>urn:ietf:params:xml:ns:yang:ietf-inet-types</namesp\
\ace>
</import-only-module>
</module-set>
<schema>
<name>config-schema</name>
<module-set>config-modules</module-set>
</schema>
<schema>
<name>state-schema</name>
<module-set>config-modules</module-set>
<module-set>state-modules</module-set>
</schema>
<datastore>
<name>ds:startup</name>
<schema>config-schema</schema>
</datastore>
<datastore>
<name>ds:running</name>
<schema>config-schema</schema>
</datastore>
<datastore>
<name>ds:operational</name>
<schema>state-schema</schema>
</datastore>
<content-id>75a43df9bd56b92aacc156a2958fbe12312fb285</content-id>
</yang-library>
9. Security Considerations 9. Security Considerations
This BCP has no Security Considerations. This BCP has no Security Considerations.
10. IANA Considerations 10. IANA Considerations
This BCP has no IANA Considerations. This BCP has no IANA Considerations.
11. References 11. References
skipping to change at page 10, line 47 skipping to change at page 13, line 37
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References 11.2. Informative References
[RFC7749] Reschke, J., "The "xml2rfc" Version 2 Vocabulary",
RFC 7749, DOI 10.17487/RFC7749, February 2016,
<https://www.rfc-editor.org/info/rfc7749>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016, RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>. <https://www.rfc-editor.org/info/rfc7950>.
[RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary", [RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary",
RFC 7991, DOI 10.17487/RFC7991, December 2016, RFC 7991, DOI 10.17487/RFC7991, December 2016,
<https://www.rfc-editor.org/info/rfc7991>. <https://www.rfc-editor.org/info/rfc7991>.
[RFC7994] Flanagan, H., "Requirements for Plain-Text RFCs", [RFC7994] Flanagan, H., "Requirements for Plain-Text RFCs",
RFC 7994, DOI 10.17487/RFC7994, December 2016, RFC 7994, DOI 10.17487/RFC7994, December 2016,
<https://www.rfc-editor.org/info/rfc7994>. <https://www.rfc-editor.org/info/rfc7994>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>. <https://www.rfc-editor.org/info/rfc8340>.
[xiax] "The `xiax` Python Package",
<https://pypi.org/project/xiax/>.
[yang-doctors-thread] [yang-doctors-thread]
"[yang-doctors] automating yang doctor reviews", "[yang-doctors] automating yang doctor reviews",
<https://mailarchive.ietf.org/arch/msg/yang-doctors/ <https://mailarchive.ietf.org/arch/msg/yang-doctors/
DCfBqgfZPAD7afzeDFlQ1Xm2X3g>. DCfBqgfZPAD7afzeDFlQ1Xm2X3g>.
Appendix A. POSIX Shell Script Appendix A. POSIX Shell Script
This non-normative appendix section includes a shell script that can This non-normative appendix section includes a shell script that can
both fold and unfold artwork. both fold and unfold text content. Note that this script is applied
only to single text content instances.
========== NOTE: '\\' line wrapping per BCP XX (RFC XXXX) ===========
#!/bin/bash #!/bin/bash
print_usage() { print_usage() {
echo echo
echo "Folds the text file, only if needed, at the specified" echo "Folds the text file, only if needed, at the specified"
echo "column, according to BCP XX." echo "column, according to BCP XX."
echo echo
echo "Usage: $0 [-c <col>] [-r] -i <infile> -o <outfile>" echo "Usage: $0 [-c <col>] [-r] -i <infile> -o <outfile>"
echo echo
skipping to change at page 13, line 14 skipping to change at page 16, line 13
cp $infile $outfile cp $infile $outfile
return -1 return -1
fi fi
foldcol=`expr "$maxcol" - 1` # for the inserted '\' char foldcol=`expr "$maxcol" - 1` # for the inserted '\' char
# ensure input file doesn't contain a TAB # ensure input file doesn't contain a TAB
grep $'\t' $infile >> /dev/null 2>&1 grep $'\t' $infile >> /dev/null 2>&1
if [ $? -eq 0 ]; then if [ $? -eq 0 ]; then
echo echo
echo "Error: infile contains a TAB character, which is not allow\ echo "Error: infile contains a TAB character, which is not"
\ed." echo "allowed."
echo echo
return 1 return 1
fi fi
# ensure input file doesn't contain the fold-sequence already # ensure input file doesn't contain the fold-sequence already
pcregrep -M "\\\\\n[\ ]*\\\\" $infile >> /dev/null 2>&1 pcregrep -M "\\\\\n[\ ]*\\\\" $infile >> /dev/null 2>&1
if [ $? -eq 0 ]; then if [ $? -eq 0 ]; then
echo echo
echo "Error: infile has a line ending with a '\' character follo\ echo "Error: infile has a line ending with a '\' character"
\wed" echo " followed by a '\' character as the first non-space"
echo " by '\' as the first non-space character on the next\ echo " character on the next line. This file cannot be"
\ line." echo " folded."
echo " This file cannot be folded."
echo echo
return 1 return 1
fi fi
# center header text # center header text
length=`expr ${#hdr_txt} + 2` length=`expr ${#hdr_txt} + 2`
left_sp=`expr \( "$maxcol" - "$length" \) / 2` left_sp=`expr \( "$maxcol" - "$length" \) / 2`
right_sp=`expr "$maxcol" - "$length" - "$left_sp"` right_sp=`expr "$maxcol" - "$length" - "$left_sp"`
header=`printf "%.*s %s %.*s" "$left_sp" "$equal_chars" "$hdr_txt"\ header=`printf "%.*s %s %.*s" "$left_sp" "$equal_chars"\
\ "$right_sp" "$equal_chars"` "$hdr_txt" "$right_sp" "$equal_chars"`
# fold using recursive passes ('g' didn't work) # fold using recursive passes ('g' didn't work)
if [ -z "$1" ]; then if [ -z "$1" ]; then
# init recursive env # init recursive env
cp $infile /tmp/wip cp $infile /tmp/wip
fi fi
gsed "/.\{$testcol\}/s/\(.\{$foldcol\}\)/\1\\\\\n\\\\/" < /tmp/wip\ gsed "/.\{$testcol\}/s/\(.\{$foldcol\}\)/\1\\\\\n\\\\/" < /tmp/wip\
\ >> /tmp/wip2 >> /tmp/wip2
diff /tmp/wip /tmp/wip2 > /dev/null 2>&1 diff /tmp/wip /tmp/wip2 > /dev/null 2>&1
if [ $? -eq 1 ]; then if [ $? -eq 1 ]; then
mv /tmp/wip2 /tmp/wip mv /tmp/wip2 /tmp/wip
fold_it "recursing" fold_it "recursing"
else else
echo "$header" > $outfile echo "$header" > $outfile
echo "" >> $outfile echo "" >> $outfile
cat /tmp/wip2 >> $outfile cat /tmp/wip2 >> $outfile
rm /tmp/wip* rm /tmp/wip*
fi fi
## following two lines represent a non-functional variant to the r\ ## following two lines represent a non-functional variant to the
\ecursive ## recursive logic presented in the block above. It used to work
## logic presented in the block above. It used to work before the\ ## before the '\' on the next line was added to the format (i.e.,
\ '\' ## the trailing '\\\\' in the substitution below), but now there
## on the next line was added to the format (i.e., the trailing '\\ ## is an off-by-one error. Leaving here in case anyone can fix it.
\\\\'
## in the substitution below), but now there is an off-by-one erro\
\r.
## Leaving here in case anyone can fix it.
#echo "$header" > $outfile #echo "$header" > $outfile
#echo "" >> $outfile #echo "" >> $outfile
#gsed "/.\{$testcol\}/s/\(.\{$foldcol\}\)/\1\\\\\n\\\\/g" < $infil\ #gsed "/.\{$testcol\}/s/\(.\{$foldcol\}\)/\1\\\\\n\\\\/g"\
\e >> $outfile < $infile >> $outfile
return 0 return 0
} }
unfold_it() { unfold_it() {
# check if file needs unfolding # check if file needs unfolding
line=`head -n 1 $infile | fgrep "$hdr_txt"` line=`head -n 1 $infile | fgrep "$hdr_txt"`
if [ $? -ne 0 ]; then if [ $? -ne 0 ]; then
if [[ $debug -eq 1 ]]; then if [[ $debug -eq 1 ]]; then
echo "nothing to do" echo "nothing to do"
fi fi
cp $infile $outfile cp $infile $outfile
return -1 return -1
fi fi
# output all but the first two lines (the header) to wip (work in \ # output all but the first two lines (the header) to wip (work
\progress) file # in progress) file
awk "NR>2" $infile > /tmp/wip awk "NR>2" $infile > /tmp/wip
# unfold wip file # unfold wip file
gsed ":x; /.*\\\\\$/N; s/\\\\\n[ ]*\\\\//; tx; s/\t//g" /tmp/wip >\ gsed ":x; /.*\\\\\$/N; s/\\\\\n[ ]*\\\\//; tx; s/\t//g" /tmp/wip\
\ $outfile > $outfile
# clean up and return # clean up and return
rm /tmp/wip rm /tmp/wip
return 0 return 0
} }
process_input() { process_input() {
while [ "$1" != "" ]; do while [ "$1" != "" ]; do
if [ "$1" == "-h" -o "$1" == "--help" ]; then if [ "$1" == "-h" -o "$1" == "--help" ]; then
print_usage print_usage
exit 1 exit 1
fi fi
if [ "$1" == "-d" ]; then if [ "$1" == "-d" ]; then
debug=1 debug=1
fi fi
if [ "$1" == "-c" ]; then if [ "$1" == "-c" ]; then
maxcol="$2" maxcol="$2"
shift shift
fi fi
if [ "$1" == "-r" ]; then if [ "$1" == "-r" ]; then
reversed=1 reversed=1
skipping to change at page 16, line 4 skipping to change at page 18, line 47
echo echo
exit 1 exit 1
fi fi
if [ ! -f "$infile" ]; then if [ ! -f "$infile" ]; then
echo echo
echo "Error: specified file \"$infile\" is does not exist." echo "Error: specified file \"$infile\" is does not exist."
echo echo
exit 1 exit 1
fi fi
min_supported=`expr ${#hdr_txt} + 8` min_supported=`expr ${#hdr_txt} + 8`
if [ $maxcol -lt $min_supported ]; then if [ $maxcol -lt $min_supported ]; then
echo echo
echo "Error: the folding column cannot be less than $min_support\ echo "Error: the folding column cannot be less than"
\ed" echo "$min_supported"
echo echo
exit 1 exit 1
fi fi
max_supported=`expr ${#equal_chars} + 1 + ${#hdr_txt} + 1 + ${#equ\ max_supported=`expr ${#equal_chars} + 1 + ${#hdr_txt} + 1\
\al_chars}` + ${#equal_chars}`
if [ $maxcol -gt $max_supported ]; then if [ $maxcol -gt $max_supported ]; then
echo echo
echo "Error: the folding column cannot be more than $max_support\ echo "Error: the folding column cannot be more than"
\ed" echo "$max_supported"
echo echo
exit 1 exit 1
fi fi
} }
main() { main() {
if [ "$#" == "0" ]; then if [ "$#" == "0" ]; then
print_usage print_usage
exit 1 exit 1
skipping to change at page 17, line 6 skipping to change at page 19, line 48
main "$@" main "$@"
Acknowledgements Acknowledgements
The authors thank the following folks for their various contributions The authors thank the following folks for their various contributions
(sorted by first name): Gianmarco Bruno, Italo Busi, Jonathan (sorted by first name): Gianmarco Bruno, Italo Busi, Jonathan
Hansford, Joel Jaeggli, Lou Berger, Martin Bjorklund, Italo Busi, and Hansford, Joel Jaeggli, Lou Berger, Martin Bjorklund, Italo Busi, and
Rob Wilton. Rob Wilton.
The authors additionally thank the RFC Editor for confirming that The authors additionally thank the RFC Editor for confirming that
there is no set convention today for handling long lines in artwork. there is no set convention today for handling long lines in artwork/
sourcecode inclusions.
Authors' Addresses Authors' Addresses
Kent Watsen Kent Watsen
Juniper Networks Watsen Networks
EMail: kwatsen@juniper.net EMail: kent+ietf@watsen.net
Qin Wu Qin Wu
Huawei Technologies Huawei Technologies
EMail: bill.wu@huawei.com EMail: bill.wu@huawei.com
Adrian Farrel Adrian Farrel
Old Dog Consulting Old Dog Consulting
EMail: adrian@olddog.co.uk EMail: adrian@olddog.co.uk
 End of changes. 80 change blocks. 
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