sep-0012.txt

SEP: 12
Title: Sample reStructuredText SEP Template
Version: $Revision$
Last-Modified: $Date$
Author: Michael Carroll
Status: Draft
Type: Process
Content-Type: text/x-rst
Created: 05-Aug-2002
Post-History: 30-Aug-2002


Abstract
========

This SEP provides a boilerplate or sample template for creating your
own reStructuredText SEPs.  In conjunction with the content guidelines
in SEP 1 [1]_, this should make it easy for you to conform your own
SEPs to the format outlined below.

Note: if you are reading this SEP via the web, you should first grab
the text (reStructuredText) source of this SEP in order to complete
the steps below.  **DO NOT USE THE HTML FILE AS YOUR TEMPLATE!**

To get the source this (or any) SEP, look at the top of the HTML page
and click on the date & time on the "Last-Modified" line.  It is a
link to the source text in the ROS repository.

This template is entirely based on the PEP 9 template by David Goodger
and Barry Warsaw.  The Author field of this document has been changed
in order to reflect reponsibility for maintenance.

Rationale
=========

SEP submissions come in a wide variety of forms, not all adhering
to the format guidelines set forth below.  Use this template, in
conjunction with the format guidelines below, to ensure that your
SEP submission won't get automatically rejected because of form.

ReStructuredText is offered as an alternative to plaintext SEPs, to
allow SEP authors more functionality and expressivity, while
maintaining easy readability in the source text.  The processed HTML
form makes the functionality accessible to readers: live hyperlinks,
styled text, tables, images, and automatic tables of contents, among
other advantages.


How to Use This Template
========================

To use this template you must first decide whether your SEP is going
to be an Informational, Process, or Rules SEP.  Most SEPs are
Process because they propose a new process for the SPaRC team.
When in doubt, read SEP 1 for details.

Once you've decided which type of SEP yours is going to be, follow the
directions below.

- Make a copy of this file (``.txt`` file, **not** HTML!) and perform
  the following edits.

- Replace the "SEP: 9" header with "SEP: XXX" since you don't yet have
  a SEP number assignment.

- Change the Title header to the title of your SEP.

- Leave the Version and Last-Modified headers alone; we'll take care
  of those when we check your SEP into Github repository.
  These headers consist of keywords ("Revision" and "Date" enclosed in
  "$"-signs) which are automatically expanded by the repository.
  Please do not edit the expanded date or revision text.

- Change the Author header to include your name, and optionally your
  email address.  Be sure to follow the format carefully: your name
  must appear first, and it must not be contained in parentheses.
  Your email address may appear second (or it can be omitted) and if
  it appears, it must appear in angle brackets.  It is okay to
  obfuscate your email address.

- If there is a mailing list for discussion of your new feature, add a
  Discussions-To header right after the Author header.

- Change the Status header to "Draft".

- For Rule SEPs, change the Type header to "Rules".

- For Informational SEPs, change the Type header to "Informational".

- Change the Created header to today's date.  Be sure to follow the
  format carefully: it must be in ``dd-mmm-yyyy`` format, where the
  ``mmm`` is the 3 English letter month abbreviation, i.e. one of Jan,
  Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec.

- Leave Post-History alone for now; you'll add dates to this header
  each time you post your SEP.  If you posted your SEP to the lists on
  August 14, 2001 and September 3, 2001, the Post-History header would
  look like::

      Post-History: 14-Aug-2001, 03-Sept-2001

  You must manually add new dates and check them in.  If you don't
  have check-in privileges, send your changes to the SEP editors.

- Add a Replaces header if your SEP obsoletes an earlier SEP.  The
  value of this header is the number of the SEP that your new SEP is
  replacing.  Only add this header if the older SEP is in "final"
  form, i.e. is either Accepted, Final, or Rejected.  You aren't
  replacing an older open SEP if you're submitting a competing idea.

- Now write your Abstract, Rationale, and other content for your SEP,
  replacing all this gobbledygook with your own text. Be sure to
  adhere to the format guidelines below, specifically on the
  prohibition of tab characters and the indentation requirements.

- Update your References and Copyright section.  Usually you'll place
  your SEP into the public domain, in which case just leave the
  Copyright section alone.  Alternatively, you can use the `Open
  Publication License`__, but public domain is still strongly
  preferred.

  __ http://www.opencontent.org/openpub/

- Leave the Emacs stanza at the end of this file alone, including the
  formfeed character ("^L", or ``\f``).

- Send your SEP submission to the ROS developers at ros-developers@code.ros.org.


ReStructuredText SEP Formatting Requirements
============================================

The following is a SEP-specific summary of reStructuredText syntax.
For the sake of simplicity and brevity, much detail is omitted.  For
more detail, see `Resources`_ below.  `Literal blocks`_ (in which no
markup processing is done) are used for examples throughout, to
illustrate the plaintext markup.


General
-------

You must adhere to the Emacs convention of adding two spaces at the
end of every sentence.  You should fill your paragraphs to column 70,
but under no circumstances should your lines extend past column 79.
If your code samples spill over column 79, you should rewrite them.

Tab characters must never appear in the document at all.  A SEP should
include the standard Emacs stanza included by example at the bottom of
this SEP.


Section Headings
----------------

SEP headings must begin in column zero and the initial letter of each
word must be capitalized as in book titles.  Acronyms should be in all
capitals.  Section titles must be adorned with an underline, a single
repeated punctuation character, which begins in column zero and must
extend at least as far as the right edge of the title text (4
characters minimum).  First-level section titles are underlined with
"=" (equals signs), second-level section titles with "-" (hyphens),
and third-level section titles with "'" (single quotes or
apostrophes).  For example::

    First-Level Title
    =================

    Second-Level Title
    ------------------

    Third-Level Title
    '''''''''''''''''

If there are more than three levels of sections in your SEP, you may
insert overline/underline-adorned titles for the first and second
levels as follows::

    ============================
    First-Level Title (optional)
    ============================

    -----------------------------
    Second-Level Title (optional)
    -----------------------------

    Third-Level Title
    =================

    Fourth-Level Title
    ------------------

    Fifth-Level Title
    '''''''''''''''''

You shouldn't have more than five levels of sections in your SEP.  If
you do, you should consider rewriting it.

You must use two blank lines between the last line of a section's body
and the next section heading.  If a subsection heading immediately
follows a section heading, a single blank line in-between is
sufficient.

The body of each section is not normally indented, although some
constructs do use indentation, as described below.  Blank lines are
used to separate constructs.


Paragraphs
----------

Paragraphs are left-aligned text blocks separated by blank lines.
Paragraphs are not indented unless they are part of an indented
construct (such as a block quote or a list item).


Inline Markup
-------------

Portions of text within paragraphs and other text blocks may be
styled.  For example::

    Text may be marked as *emphasized* (single asterisk markup,
    typically shown in italics) or **strongly emphasized** (double
    asterisks, typically boldface).  ``Inline literals`` (using double
    backquotes) are typically rendered in a monospaced typeface.  No
    further markup recognition is done within the double backquotes,
    so they're safe for any kind of code snippets.


Block Quotes
------------

Block quotes consist of indented body elements.  For example::

    This is a paragraph.

        This is a block quote.

        A block quote may contain many paragraphs.

Block quotes are used to quote extended passages from other sources.
Block quotes may be nested inside other body elements.  Use 4 spaces
per indent level.


Literal Blocks
--------------

..
    In the text below, double backquotes are used to denote inline
    literals.  "``::``" is written so that the colons will appear in a
    monospaced font; the backquotes (``) are markup, not part of the
    text.  See "Inline Markup" above.

    By the way, this is a comment, described in "Comments" below.

Literal blocks are used for code samples or preformatted ASCII art. To
indicate a literal block, preface the indented text block with
"``::``" (two colons).  The literal block continues until the end of
the indentation.  Indent the text block by 4 spaces.  For example::

    This is a typical paragraph.  A literal block follows.

    ::

        for a in [5,4,3,2,1]:   # this is program code, shown as-is
            print a
        print "it's..."
        # a literal block continues until the indentation ends

The paragraph containing only "``::``" will be completely removed from
the output; no empty paragraph will remain.  "``::``" is also
recognized at the end of any paragraph.  If immediately preceded by
whitespace, both colons will be removed from the output.  When text
immediately precedes the "``::``", *one* colon will be removed from
the output, leaving only one colon visible (i.e., "``::``" will be
replaced by "``:``").  For example, one colon will remain visible
here::

    Paragraph::

        Literal block


Lists
-----

Bullet list items begin with one of "-", "*", or "+" (hyphen,
asterisk, or plus sign), followed by whitespace and the list item
body.  List item bodies must be left-aligned and indented relative to
the bullet; the text immediately after the bullet determines the
indentation.  For example::

    This paragraph is followed by a list.

    * This is the first bullet list item.  The blank line above the
      first list item is required; blank lines between list items
      (such as below this paragraph) are optional.

    * This is the first paragraph in the second item in the list.

      This is the second paragraph in the second item in the list.
      The blank line above this paragraph is required.  The left edge
      of this paragraph lines up with the paragraph above, both
      indented relative to the bullet.

      - This is a sublist.  The bullet lines up with the left edge of
        the text blocks above.  A sublist is a new list so requires a
        blank line above and below.

    * This is the third item of the main list.

    This paragraph is not part of the list.

Enumerated (numbered) list items are similar, but use an enumerator
instead of a bullet.  Enumerators are numbers (1, 2, 3, ...), letters
(A, B, C, ...; uppercase or lowercase), or Roman numerals (i, ii, iii,
iv, ...; uppercase or lowercase), formatted with a period suffix
("1.", "2."), parentheses ("(1)", "(2)"), or a right-parenthesis
suffix ("1)", "2)").  For example::

    1. As with bullet list items, the left edge of paragraphs must
       align.

    2. Each list item may contain multiple paragraphs, sublists, etc.

       This is the second paragraph of the second list item.

       a) Enumerated lists may be nested.
       b) Blank lines may be omitted between list items.

Definition lists are written like this::

    what
        Definition lists associate a term with a definition.

    how
        The term is a one-line phrase, and the definition is one
        or more paragraphs or body elements, indented relative to
        the term.


Tables
------

Simple tables are easy and compact::

    =====  =====  =======
      A      B    A and B
    =====  =====  =======
    False  False  False
    True   False  False
    False  True   False
    True   True   True
    =====  =====  =======

There must be at least two columns in a table (to differentiate from
section titles).  Column spans use underlines of hyphens ("Inputs"
spans the first two columns)::

    =====  =====  ======
       Inputs     Output
    ------------  ------
      A      B    A or B
    =====  =====  ======
    False  False  False
    True   False  True
    False  True   True
    True   True   True
    =====  =====  ======

Text in a first-column cell starts a new row.  No text in the first
column indicates a continuation line; the rest of the cells may
consist of multiple lines.  For example::

    =====  =========================
    col 1  col 2
    =====  =========================
    1      Second column of row 1.
    2      Second column of row 2.
           Second line of paragraph.
    3      - Second column of row 3.

           - Second item in bullet
             list (row 3, column 2).
    =====  =========================


Hyperlinks
----------

When referencing an external web page in the body of a SEP, you should
include the title of the page in the text, with either an inline
hyperlink reference to the URL or a footnote reference (see
`Footnotes`_ below).  Do not include the URL in the body text of the
SEP.

Hyperlink references use backquotes and a trailing underscore to mark
up the reference text; backquotes are optional if the reference text
is a single word.  For example::

    In this paragraph, we refer to the `ROS web site`_.

An explicit target provides the URL.  Put targets in a References
section at the end of the SEP, or immediately after the reference.
Hyperlink targets begin with two periods and a space (the "explicit
markup start"), followed by a leading underscore, the reference text,
a colon, and the URL (absolute or relative)::

    .. _ROS web site: http://ros.org/

The reference text and the target text must match (although the match
is case-insensitive and ignores differences in whitespace).  Note that
the underscore trails the reference text but precedes the target text.
If you think of the underscore as a right-pointing arrow, it points
*away* from the reference and *toward* the target.

The same mechanism can be used for internal references.  Every unique
section title implicitly defines an internal hyperlink target.  We can
make a link to the Abstract section like this::

    Here is a hyperlink reference to the `Abstract`_ section.  The
    backquotes are optional since the reference text is a single word;
    we can also just write: Abstract_.

Footnotes containing the URLs from external targets will be generated
automatically at the end of the References section of the SEP, along
with footnote references linking the reference text to the footnotes.

Text of the form "SEP x" or "RFC x" (where "x" is a number) will be
linked automatically to the appropriate URLs.


Footnotes
---------

Footnote references consist of a left square bracket, a number, a
right square bracket, and a trailing underscore::

    This sentence ends with a footnote reference [1]_.

Whitespace must precede the footnote reference.  Leave a space between
the footnote reference and the preceding word.

When referring to another SEP, include the SEP number in the body
text, such as "SEP 1".  The title may optionally appear.  Add a
footnote reference following the title.  For example::

    Refer to SEP 1 [2]_ for more information.

Add a footnote that includes the SEP's title and author.  It may
optionally include the explicit URL on a separate line, but only in
the References section.  Footnotes begin with ".. " (the explicit
markup start), followed by the footnote marker (no underscores),
followed by the footnote body.  For example::

    References
    ==========

    .. [2] SEP 1, "SEP Purpose and Guidelines", Carroll
       (http://AuburnSPaRC.github.com/SEP/sep-0001.html)

If you decide to provide an explicit URL for a SEP, please use this as
the URL template::

   http://AuburnSPaRC.github.com/SEP/sep-xxxx.html

SEP numbers in URLs must be padded with zeros from the left, so as to
be exactly 4 characters wide, however SEP numbers in the text are
never padded.

During the course of developing your SEP, you may have to add, remove,
and rearrange footnote references, possibly resulting in mismatched
references, obsolete footnotes, and confusion.  Auto-numbered
footnotes allow more freedom.  Instead of a number, use a label of the
form "#word", where "word" is a mnemonic consisting of alphanumerics
plus internal hyphens, underscores, and periods (no whitespace or
other characters are allowed).  For example::

    Refer to SEP 1 [#SEP-1]_ for more information.

    References
    ==========

    .. [#SEP-1] SEP 1, "SEP Purpose and Guidelines", Warsaw, Hylton

       http://AuburnSPaRC.github.com/SEP/sep-0001.html

Footnotes and footnote references will be numbered automatically, and
the numbers will always match.  Once a SEP is finalized, auto-numbered
labels should be replaced by numbers for simplicity.


Images
------

If your SEP contains a diagram, you may include it in the processed
output using the "image" directive::

    .. image:: diagram.png

Any browser-friendly graphics format is possible: .png, .jpeg, .gif,
.tiff, etc.

Since this image will not be visible to readers of the SEP in source
text form, you should consider including a description or ASCII art
alternative, using a comment (below).


Comments
--------

A comment block is an indented block of arbitrary text immediately
following an explicit markup start: two periods and whitespace.  Leave
the ".." on a line by itself to ensure that the comment is not
misinterpreted as another explicit markup construct.  Comments are not
visible in the processed document.  For the benefit of those reading
your SEP in source form, please consider including a descriptions of
or ASCII art alternatives to any images you include.  For example::

     .. image:: dataflow.png

     ..
        Data flows from the input module, through the "black box"
        module, and finally into (and through) the output module.

The Emacs stanza at the bottom of this document is inside a comment.


Escaping Mechanism
------------------

reStructuredText uses backslashes ("``\``") to override the special
meaning given to markup characters and get the literal characters
themselves.  To get a literal backslash, use an escaped backslash
("``\\``").  There are two contexts in which backslashes have no
special meaning: `literal blocks`_ and inline literals (see `Inline
Markup`_ above).  In these contexts, no markup recognition is done,
and a single backslash represents a literal backslash, without having
to double up.

If you find that you need to use a backslash in your text, consider
using inline literals or a literal block instead.


Habits to Avoid
===============

Many programmers who are familiar with TeX often write quotation marks
like this::

    `single-quoted' or ``double-quoted''

Backquotes are significant in reStructuredText, so this practice
should be avoided.  For ordinary text, use ordinary 'single-quotes' or
"double-quotes".  For inline literal text (see `Inline Markup`_
above), use double-backquotes::

    ``literal text: in here, anything goes!``


Resources
=========

Many other constructs and variations are possible.  For more details
about the reStructuredText markup, in increasing order of
thoroughness, please see:

* `A ReStructuredText Primer`__, a gentle introduction.

  __ http://docutils.sourceforge.net/docs/rst/quickstart.html

* `Quick reStructuredText`__, a users' quick reference.

  __ http://docutils.sourceforge.net/docs/rst/quickref.html

* `reStructuredText Markup Specification`__, the final authority.

  __ http://docutils.sourceforge.net/spec/rst/reStructuredText.html

The processing of reStructuredText SEPs is done using Docutils_.  If
you have a question or require assistance with reStructuredText or
Docutils, please `post a message`_ to the `Docutils-users mailing
list`_.  The `Docutils project web site`_ has more information.

.. _Docutils:
.. _Docutils project web site: http://docutils.sourceforge.net/
.. _post a message:
   mailto:docutils-users@lists.sourceforge.net?subject=SEPs
.. _Docutils-users mailing list:
   http://docutils.sf.net/docs/user/mailing-lists.html#docutils-users


References
==========

.. [1] SEP 1, SEP Purpose and Guidelines
   (http://AuburnSPaRC.github.com/SEP/sep-0001.html)


Copyright
=========

This document has been placed in the public domain.



..
   Local Variables:
   mode: indented-text
   indent-tabs-mode: nil
   sentence-end-double-space: t
   fill-column: 70
   coding: utf-8
   End: