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Versions: 00 draft-ietf-appsawg-text-markdown

Network Working Group                                         S. Leonard
Internet-Draft                                             Penango, Inc.
Intended Status: Informational                              July 4, 2014
Expires: January 5, 2015

                      The text/markdown Media Type


   This document registers the text/markdown media type for use with
   Markdown, a family of plain text formatting syntaxes that optionally
   can be converted to formal markup languages such as HTML.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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Copyright Notice

   Copyright (c) 2014 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
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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1. Introduction

   In computer systems, textual data is stored and processed using a
   continuum of techniques. On the one end is plain text: a linear
   sequence of characters in some character set (code), possibly
   interrupted by line breaks, page breaks, or other control characters.
   Plain text provides /some/ fixed facilities for formatting
   instructions, namely codes in the character set that have meanings
   other than "represent this character on the output medium"; however,
   these facilities are not particularly extensible. Compare with
   [RFC6838] Section 4.2.1. (Applications may neuter the effects of
   these special characters by prohibiting them or by ignoring their
   dictated meanings, as is the case with how modern applications treat
   most control characters in US-ASCII.) On this end, any text reader or
   editor that interprets the character set can be used to see or
   manipulate the text. If some characters are corrupted, the corruption
   is unlikely to affect the ability of a computer system to process the
   text (even if the human meaning is changed).

   On the other end is binary format: a sequence of instructions
   intended for some computer application to interpret and act upon.
   Binary formats are flexible in that they can store non-textual data
   efficiently (perhaps storing no text at all, or only storing certain
   kinds of text for very specialized purposes). Binary formats require
   an application to be coded specifically to handle the format; no
   partial interoperability is possible. Furthermore, if even one byte
   or bit are corrupted in a binary format, it may prevent an
   application from processing any of the data correctly.

   Between these two extremes lies formatted text, i.e., text that
   includes non-textual information coded in a particular way, that
   affects the interpretation of the text by computer programs.
   Formatted text is distinct from plain text and binary format in that
   the non-textual information is encoded into textual characters, which
   are assigned specialized meanings /not/ defined by the character set.
   With a regular text editor and a standard keyboard (or other standard
   input mechanism), a user can enter these textual characters to
   express the non-textual meanings. For example, a character like "<"
   no longer means "LESS-THAN SIGN"; it means the start of a tag or
   element that affects the document in some way.

   On the formal end of the spectrum is markup, a family of languages
   for annotating a document in such a way that the annotations are
   syntactically distinguishable from the text. Markup languages are
   (reasonably) well-specified and tend to follow (mostly) standardized
   syntax rules. Examples of markup languages include SGML, HTML, XML,
   and LaTeX. Standardized rules lead to interoperability between markup
   processors, but a skill requirement for new (human) users of the

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   language that they learn these rules in order to do useful work. This
   imposition makes markup less accessible for non-technical users
   (i.e., users who are unwilling or unable to invest in the requisite
   skill development).

     informal        /---------formatted text----------\        formal
      plain text     informal markup   formal markup    binary format
                     (Markdown)        (HTML, XML, etc.)

    Figure 1: Degrees of Formality in Data Storage Formats for Text

   On the informal end of the spectrum are lightweight markup languages.
   In comparison with formal markup like XML, lightweight markup uses
   simple syntax, and is designed to be easy for humans to enter with
   basic text editors. Markdown, the subject of this document, is an
   /informal/ plain text formatting syntax that is intentionally
   targeted at non-technical users (i.e., users upon whom little to no
   skill development is imposed) using unspecialized tools (i.e., text
   boxes). Jeff Atwood once described these informal markup languages as

   Markdown specifically is a family of syntaxes that are based on the
   original work of John Gruber with substantial contributions from
   Aaron Swartz, released in 2004.[MARKDOWN] Since its release a number
   of web or web-facing applications have incorporated Markdown into
   their text entry systems, frequently with proprietary extensions. Fed
   up with the complexity and security pitfalls of formal markup
   languages (e.g., HTML5) and proprietary binary formats (e.g.,
   commercial word processing software), yet unwilling to be confined to
   the restrictions of plain text, many users have turned to Markdown
   for document processing. Whole toolchains now exist to support
   Markdown for online and offline projects.

   Due to Markdown's intentional informality, there is no standard
   specifying the Markdown syntax, and no governing body that guides or
   impedes its development. Markdown works for users for two key
   reasons. First, the markup instructions (in text) look similar to the
   markup that they represent; therefore the cognitive burden to learn
   the syntax is very low. Second, the primary arbiter of the syntax's
   success is *running code*. The tool that converts the Markdown to a
   presentable format, and not a series of formal pronouncements by a
   standards body, is the basis for whether syntactic elements matter.

   To support identifying and conveying Markdown (as distinguished from
   plain text), this document defines a media type and a "flavor"
   parameter that indicates, in broad strokes, the author's intent on
   how to interpret the Markdown.

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1.1. Requirements Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

2. Markdown Media Type Registration Applications

   This section provides the media type registration application for the
   text/markdown media type (see [RFC6838], Section 5.6).

   Type name: text

   Subtype name: markdown

   Required parameters: charset. Per Section 4.2.1 of [RFC6838], charset
   is REQUIRED. The default value is UTF-8. If omitted, parsers MAY
   reject the input; if parsers accept the input, they MUST interpret
   the content as UTF-8.

   Optional parameters:

     flavor=f; where f is an identifier that specifies the "flavor", or
     variation, of the Markdown syntax. The parameter represents the
     intent of the author, namely, that the Markdown will be interpreted
     "best" (i.e., as the author intended) when processed with tools
     associated with the identified flavor.

     The flavor parameter is opaque and case-sensitive. Valid flavor
     values can be any sequence of characters or bytes; in practice,
     however, virtually all will be alphanumeric (US-ASCII) and
     registered in the IANA Markdown Flavors Registry, discussed in
     Section 4. Implementations checking flavor parameters MUST only
     compare them for exact equality.

   Encoding considerations: Text.

   Security considerations:

     Markdown interpreted as plain text is relatively harmless. A text
     editor need only display the text. The editor SHOULD take care to
     handle control characters appropriately, and to limit the effect of
     the Markdown to the text editing area itself; malicious Unicode-
     based Markdown could, for example, surreptitiously change the
     directionality of the text. An editor for normal text would already
     take these control characters into consideration, however.

     Markdown interpreted as a precursor to other formats, such as HTML,

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     carry all of the security considerations as the target formats. For
     example, HTML can contain instructions to execute scripts, redirect
     the user to other webpages, download remote content, and upload
     personally identifiable information. Markdown also can contain
     islands of formal markup, such as HTML. These islands of formal
     markup may be passed as-is, transformed, or ignored (perhaps
     because the islands are conditional or incompatible) when the
     Markdown is interpreted into the target format. Since Markdown may
     have different interpretations depending on the tool and the
     environment, a better approach is to analyze (and sanitize or
     block) the output markup, rather than attempting to analyze the

   Interoperability considerations:

     Markdown flavors are designed to be broadly compatible with humans
     ("humane"), but not necessarily with each other. Therefore, syntax
     in one Markdown flavor may be ignored or treated differently in
     another flavor. The overall effect is a general degradation of the
     output, proportional to the quantity of flavor-specific Markdown
     used in the text. When it is desirable to reflect the author's
     intent in the output, stick with the flavor identified in the
     flavor parameter.

   Published specification: This specification.

   Applications that use this media type:

     Markdown conversion tools, Markdown WYSIWYG editors, and plain text
     editors and viewers; target markup processors indirectly use
     Markdown (e.g., web browsers for Markdown converted to HTML).

   Additional information:

     Magic number(s): None
     File extension(s): .md, .markdown
     Macintosh File Type Code(s): TEXT

   Person & email address to contact for further information:

     Sean Leonard <dev+ietf@seantek.com>

   Restrictions on usage: None.

   Author: Sean Leonard <dev+ietf@seantek.com>

   Intended usage: COMMON

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   Change controller: The IESG <iesg@ietf.org>

3.  Example

   The following is an example of Markdown as an e-mail attachment:

      MIME-Version: 1.0
      Content-Type: text/markdown; charset=UTF-8; flavor=GitHub
      Content-Disposition: attachment; filename=readme.md

      Sample GitHub Markdown

      This is some sample GitHub Flavored Markdown (*GFM*).
      The generated HTML is then run through filters in the
      to perform things like [sanitization](#html-sanitization) and
      [syntax highlighting](#syntax-highlighting).

      Bulleted Lists

      Here are some bulleted lists...

      * One Potato
      * Two Potato
      * Three Potato

      - One Tomato
      - Two Tomato
      - Three Tomato

      More Information

      [.markdown, .md](http://daringfireball.net/projects/markdown/)
      has more information.

4.  IANA Considerations

   IANA is asked to register the media type text/markdown in the
   Standards tree using the application provided in Section 2 of this

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   IANA is also asked to establish a subtype registry called "Markdown
   Flavors". Entries in these registries is by Expert Review [RFC5226].
   The Expert will determine whether the registration represents a bona-
   fide variation of the Markdown syntax (i.e., neither a duplicate of
   an existing registration nor a syntax that is something other than
   Markdown; [MARKDOWN] SHALL be treated as a normative basis), a brief
   description, one or more responsible parties, whether the flavor is
   being maintained at the time of registration, and the existence of at
   least one complete tool (with or without documentation) that
   processes the Markdown syntax into a formal document language.

   A responsible party can be an individual author or maintainer, a
   corporate author or maintainer (plus an individual contact), or a
   representative of a community of interest dedicated to the Markdown

   The registry shall have one initial value, "Standard", with the
   following data:

    The Markdown syntax as it exists in the Markdown 1.0.1 Perl script
    at <http://daringfireball.net/projects/markdown/>, with accompanying
    documentation at

   Responsible Parties:
    John Gruber <http://daringfireball.net/>

   Currently Maintained? No

    Name: Markdown 1.0.1
    Reference: <http://daringfireball.net/projects/markdown/>
    Purpose: Converts to HTML or XHTML circa 2004.

5. Security Considerations

   See the answer to the Security Considerations template questions in
   Section 2.

6. References

6.1. Normative References

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

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   [RFC5226]  Narten, T., and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226, May 2008.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13, RFC
              6838, January 2013.

6.2. Informative References

   [HUMANE]   Atwood, J., "Is HTML a Humane Markup Language?", WWW
              language/, May 2008.

   [MARKDOWN] Gruber, J., "Daring Fireball: Markdown", WWW
              http://daringfireball.net/projects/markdown/, December

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Author's Address

   Sean Leonard
   Penango, Inc.
   5900 Wilshire Boulevard
   21st Floor
   Los Angeles, CA  90036

   EMail: dev+ietf@seantek.com
   URI:   http://www.penango.com/

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Html markup produced by rfcmarkup 1.129b, available from https://tools.ietf.org/tools/rfcmarkup/