RFC Beautification Working Group R. Gieben
Internet-Draft Google
Intended status: Informational July 05, 2013
Expires: January 06, 2014

Writing I-Ds and RFCs using Pandoc and a bit of XML


This document presents a technique for using a Markdown syntax variant, called Pandoc, and a (bit) of XML [RFC2629] as a source format for documents in the Internet-Drafts (I-Ds) and Request for Comments (RFC) series.

The goal of this technique is to let an author of an I-D focus on the main body of text without being distracted too much by XML tags, it does however not alleviate the need to typeset some files in XML.

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This Internet-Draft will expire on January 06, 2014.

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Table of Contents

1. Introduction

This document presents a technique for using a Markdown [Markdown] syntax variant, called Pandoci [Pandoc], and a bit of XML [RFC2629] as a source format for documents in the Internet-Drafts (I-Ds) and Request for Comments (RFC) series.

The goal of this technique is to let an author of an I-D focus on the main body of text without being distracted too much by XML tags, it does however not alleviate the need to typeset some files in XML.

Pandoc is an almost plain text format and therefor particularly well suited for editing RFC-like documents. The syntax itself is a super set of the syntax championed by Markdown.

2. Pandoc to RFC

Pandoc's syntax is easy to learn and write and it can be translated to numerous output formats, including, but not limited to: HTML, EPUB, (plain) Markdown and DocBook XML.

Pandoc2rfc allows authors to write in Pandoc syntax which is then transformed to XML and given to xml2rfc. The conversions are, in a way amusing, as we start off with (almost) plain text, use elaborate XML and end up with plain text again.

+-------------------+   pandoc   +---------+
| ALMOST PLAIN TEXT |   ------>  | DOCBOOK |
+-------------------+     1      +---------+
              |                       |
non-existent  |                     2 | xsltproc
  faster way  |                       |
              v                       v
      +------------+    xml2rfc  +---------+
      | PLAIN TEXT |  <--------  |   XML   |
      +------------+      3      +---------+

Figure 1: Attempt to justify Pandoc2rfc.

The output of step 2 in Figure 1 is XML which is suitable for inclusion in either the middle or back section of an RFC.

Even though Pandoc2rfc abstracts away a lot of XML details, there are still places left where XML files needs to be edited. Most notably in the front section of an RFC.

The simplest way to start using Pandoc2rfc is to create a template XML file and include the appropriate XML for the front, middle and back section:

<?xml version='1.0' ?>
<!DOCTYPE rfc SYSTEM 'rfc2629.dtd' [
<!ENTITY pandocAbstract PUBLIC '' 'abstract.xml'>
<!ENTITY pandocMiddle   PUBLIC '' 'middle.xml'>
<!ENTITY pandocBack     PUBLIC '' 'back.xml'>
<!ENTITY rfc.2629       PUBLIC '' 'reference.RFC.2629.xml'>

<rfc ipr='trust200902' docName='draft-gieben-pandoc2rfc-01'>
    <title>Writing I-Ds and RFCs using Pandoc</title>
    <references title="Normative References">

Figure 2: A minimal template.xml.

In this case you will need to edit four documents:

  1. abstract.mkd - contains the abstract;
  2. middle.mkd - contains the main body of text;
  3. back.mkd - holds the appendices (if any);
  4. And this template.xml - probably a fairly static file, among other things, it holds the author(s) and the references.

Up to date source code for Pandoc2rfc can be found at [Pandoc2rfc], this includes the style sheet transform.xsl which used for the XML transformation (also see Section 3).

2.1. Dependencies

Pandoc2rfc needs xsltproc [XSLT] and pandoc [Pandoc] to be installed. The conversion to xml2rfc XML is done with a style sheet based on XSLT version 1.0 [W3C.REC-xslt-19991116].

When using the template from Figure 2 xml2rfc version 2 (or higher) must be used.

3. Building an Internet-Draft

Assuming the setup from Section 2, we can build an I-D as follows (in a Unix-like environment):

for i in abstract middle back; do
pandoc -st docbook $i.mkd | xsltproc --nonet transform.xsl - > $i.xml

xml2rfc template.xml -f draft.txt --text  # create text output
xml2rfc template.xml -f draft.html --html # or create HTML output
xml2rfc template.xml -f draft.xml --exp   # or create XML output

Figure 3: Building an I-D.

Note that the output file names (abstract.xml, middle.xml and back.xml) must match the names used as the XML entities in template.xml (See the !ENTITY lines in Figure 2). The Pandoc2rfc source repository includes a shell script that incorporates the above transformations. Creating a draft.txt or a draft.xml can be done with pandoc2rfc *.mkd and pandoc2rfc -X *.mkd respectively.

4. Supported Features

The full description of Pandoc's syntax can be found in [PandocGuide]. The following features of xml2rfc are supported by Pandoc2rfc (also see Table 1 in Appendix B for a "cheat sheet"):

Term 1

:   Definition 1

Figure 4: Pandoc syntax used for a hanging paragraph.

  • Sections with an anchor and title attributes;
  • Several lists styles:
    • style="symbols", use "* " for each item;
    • style="numbers", use digits: "1. " for each item;
    • style="empty", use "#. " for each item;
    • style="format %i", use roman lowercase numerals: "ii. ";
    • style="format (%d)", use roman uppercase numerals "II. ";
    • style="letters", use lower- or uppercase letters: "a.  " and "A.  " (note: two spaces as mandated by Pandoc);
    • style="hanging", use the Pandoc definition list syntax:

  • Spanx style="verb", style="emph" and style="strong", respectively use: `text`, _text_ or **text**;
  • Block quote is converted to <list style="empty"> paragraph;
  • Figures with an anchor and title (Section 6.1);
  • Tables with an anchor and title (Section 6.2);
  • References (Section 6.3)
    • external (<eref>);
    • internal (<xref>), to:
      • sections (handled by Pandoc);
      • figures (handled by XSLT);
      • tables (handled by XSLT).

  • Citations, by using internal references;
  • Processing Instructions (PIs: <?rfc?>), may be used after a section header, they are carried over to the generated XML;
  • The <vspace>-tag is supported and carried over to the generated XML.

5. Unsupported Features and Limitations

With Pandoc2rfc an author of an I-D can get a long way without needing to input XML, but it is not a 100% solution. The initial setup and the reference library still forces the author to edit XML files. The meta data feature (Pandoc's "Title Block" extension) is not used in Pandoc2rfc. This information (authors, date, keyword and URLs) should be put in the template.xml.

Some other quirks:

  • An index is not supported;
  • Comments are supported via HTML comments in the Pandoc source files;
  • Authors still need to know how to deal with possible errors from xml2rfc.

6. Pandoc Style

The following sections detail how to use the Pandoc syntax for figures, tables and references to get the desired output.

6.1. Figures

Indent the paragraph with 4 spaces as mandated by Pandoc. If you add an inline footnote directly after the figure, the artwork gets a title attribute with the text of that footnote (and a possible anchor).

6.2. Tables

A table can be entered by using Pandoc's table syntax. You can choose multiple styles as input, but they all are converted to the same style (plain <texttable>) table in xml2rfc. If you add an inline footnote directly after the table, it will get a title attribute with the text of that footnote (and a possible anchor). The built in syntax of Pandoc to create a caption with Table: should not be used.

6.3. References

Pandoc provides a syntax that can be used for references. Its syntax is repeated in this paragraph. Any reference like: [Click here](URI), is an external reference. An internal (i.e. see Section X) reference is typeset with: [](#localid).

For referencing RFCs (and other citations), you will need add the reference source in the template, as an external XML entity, Figure 2 provides an example. After that you can use an internal reference: [](#RFC2629) to reference RFC 2629.

There is no direct support for referencing tables, figures and artworks, but pandoc2rfc employs the following "hack". If an inline footnote is added after the figure or table, the text of the footnote is used as the title. The first word up until a double colon :: will be used as the anchor. If a figure has an anchor it will be centered on the page.

Figure 2 for instance, is followed by this inline footnote:

^[fig:minimal::A minimal template.xml.]

7. Acknowledgements

The following people have helped shape Pandoc2rfc: Benno Overeinder, Erlend Hamnaberg, Matthijs Mekking and Trygve Laugstøl.

8. Security Considerations

This document raises no security issues.

9. IANA Considerations

This document has no actions for IANA.

10. Normative References

[Markdown] Gruber, J., "Markdown", 2004.
[XSLT] Veillard, D., "The XSLT C library for GNOME", 2006.
[Pandoc] MacFarlane, J., "Pandoc, a universal document converter", 2006.
[PandocGuide] MacFarlane, J., "Pandoc User's Guide", 2006.
[Pandoc2rfc] Gieben, R., "Pandoc2rfc git repository", October 2012.
[RFC2629] Rose, M.T., "Writing I-Ds and RFCs using XML", RFC 2629, June 1999.
[W3C.REC-xslt-19991116] Clark, J., "XSL Transformations (XSLT) Version 1.0", World Wide Web Consortium Recommendation REC-xslt-19991116, November 1999.

Appendix A. Changelog

[This section should be removed by the RFC editor before publishing]

A.1. -00

  1. Initial document.

A.2. -01

  1. Lots of updates;
  2. Added the style sheet use in an appendix.

A.3. -02

  1. Make template.xml actually valid XML;
  2. Removed the style sheet from the appendix;
  3. Make more explicit that typesetting some XML files is still needed;
  4. Fix blockquote text and conversion;
  5. Overhauled the way references to figures and tables work;
  6. Cleaned up and removed duplicate text.

Appendix B. Cheat Sheet

The most important textual constructs that can be used in Pandoc2rfc. The bottom three create output to voluminous to show in this table.
Textual construct Pandoc syntax Text output
Section Header # Section 1. Section
Unordered List * item o  item
Unordered List #. item item
Ordered List 1. item 1.  item
Ordered List a. item a.  item
Ordered List ii. item i.  item
Ordered List II. item (1)  item
Ordered List A. item A.  item
Emphasis _text_ text
Strong Emphasis **text** text
Verbatim `text` "text"
Block Quote > quote quote
External Reference [Click](URI) Click [1]
Internal Reference [](#id) Section 1
Figure Anchor ^[fid::text] N/A
Figure Reference [](#fid) Figure 1
Table Anchor ^[tid::text] N/A
Table Reference [](#tid) Table 1
Citations [](#RFC2119) [RFC2199]
Table Tables
Figures Code Blocks
Definition List Definition

Author's Address

R. (Miek) Gieben Google EMail: miek@google.com