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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Applications Area Working Group S. Leonard 3 Internet-Draft Penango, Inc. 4 Intended Status: Informational February 21, 2015 5 Expires: August 25, 2015 7 text/markdown Use Cases 8 draft-ietf-appsawg-text-markdown-use-cases-00 10 Abstract 12 This document elaborates upon the text/markdown media type for use 13 with Markdown, a family of plain text formatting syntaxes that 14 optionally can be converted to formal markup languages such as HTML. 15 Background information, local storage strategies, and additional 16 syntax registrations are supplied. 18 Status of this Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 Copyright Notice 35 Copyright (c) 2015 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Dive Into Markdown . . . . . . . . . . . . . . . . . . . . . . 2 51 1.1. On Formats . . . . . . . . . . . . . . . . . . . . . . . . 3 52 1.2. Markdown Design Philosophy . . . . . . . . . . . . . . . . 4 53 1.3. Uses of Markdown . . . . . . . . . . . . . . . . . . . . . 5 54 1.4. Uses of Labeling Markdown Content as text/markdown . . . . 5 55 2. Strategies for Preserving Media Type and Parameters . . . . . 6 56 2.1. Map to Filename and Attributes . . . . . . . . . . . . . . 7 57 2.2. Store Headers in Adjacent File . . . . . . . . . . . . . . 8 58 2.3. "Arm" Content with MIME Headers . . . . . . . . . . . . . . 8 59 2.4. Create a Local Batch Script . . . . . . . . . . . . . . . . 8 60 2.5. Process the Markdown . . . . . . . . . . . . . . . . . . . 8 61 2.6. Rely on Context . . . . . . . . . . . . . . . . . . . . . . 8 62 2.7. Specific Strategies . . . . . . . . . . . . . . . . . . . . 9 63 2.7.1. Subversion . . . . . . . . . . . . . . . . . . . . . . 9 64 2.7.2. Git . . . . . . . . . . . . . . . . . . . . . . . . . . 9 65 3. Registration Templates for Common Markdown Syntaxes . . . . . 10 66 3.1. MultiMarkdown . . . . . . . . . . . . . . . . . . . . . . . 10 67 3.2. GitHub Flavored Markdown . . . . . . . . . . . . . . . . . 11 68 3.3. Pandoc . . . . . . . . . . . . . . . . . . . . . . . . . . 11 69 3.4. Fountain (Fountain.io) . . . . . . . . . . . . . . . . . . 13 70 3.5. CommonMark . . . . . . . . . . . . . . . . . . . . . . . . 14 71 3.6. kramdown-rfc2629 (Markdown for RFCs) . . . . . . . . . . . 15 72 3.7. rfc7328 (Pandoc2rfc) . . . . . . . . . . . . . . . . . . . 15 73 3.8. PHP Markdown Extra . . . . . . . . . . . . . . . . . . . . 15 74 4. Examples for Common Markdown Syntaxes . . . . . . . . . . . . 16 75 4.1. MultiMarkdown . . . . . . . . . . . . . . . . . . . . . . . 16 76 4.2. GitHub Flavored Markdown . . . . . . . . . . . . . . . . . 16 77 4.3. Pandoc . . . . . . . . . . . . . . . . . . . . . . . . . . 16 78 4.4. Fountain (Fountain.io) . . . . . . . . . . . . . . . . . . 16 79 4.5. CommonMark . . . . . . . . . . . . . . . . . . . . . . . . 16 80 4.6. kramdown-rfc2629 (Markdown for RFCs) . . . . . . . . . . . 16 81 4.7. rfc7328 (Pandoc2rfc) . . . . . . . . . . . . . . . . . . . 16 82 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 83 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 16 84 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 85 7.1. Normative References . . . . . . . . . . . . . . . . . . . 16 86 7.2. Informative References . . . . . . . . . . . . . . . . . . 17 87 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18 89 1. Dive Into Markdown 91 This document serves as an informational companion to [MDMTREG], the 92 text/markdown media type registration. It should be considered 93 jointly with [MDMTREG]. 95 "Sometimes the truth of a thing is not so much in the 96 think of it, but in the feel of it." --Stanley Kubrick 98 1.1. On Formats 100 In computer systems, textual data is stored and processed using a 101 continuum of techniques. On the one end is plain text: a linear 102 sequence of characters in some character set (code), possibly 103 interrupted by line breaks, page breaks, or other control characters. 104 Plain text provides /some/ fixed facilities for formatting 105 instructions, namely codes in the character set that have meanings 106 other than "represent this character on the output medium"; however, 107 these facilities are not particularly extensible. Compare with 108 [RFC6838] Section 4.2.1. Applications may neuter the effects of these 109 special characters by prohibiting them or by ignoring their dictated 110 meanings, as is the case with how modern applications treat most 111 control characters in US-ASCII. On this end, any text reader or 112 editor that interprets the character set can be used to see or 113 manipulate the text. If some characters are corrupted, the corruption 114 is unlikely to affect the ability of a computer system to process the 115 text (even if the human meaning is changed). 117 On the other end is binary format: a sequence of instructions 118 intended for some computer application to interpret and act upon. 119 Binary formats are flexible in that they can store non-textual data 120 efficiently (perhaps storing no text at all, or only storing certain 121 kinds of text for very specialized purposes). Binary formats require 122 an application to be coded specifically to handle the format; no 123 partial interoperability is possible. Furthermore, if even one byte 124 or bit are corrupted in a binary format, it may prevent an 125 application from processing any of the data correctly. 127 Between these two extremes lies formatted text, i.e., text that 128 includes non-textual information coded in a particular way, that 129 affects the interpretation of the text by computer programs. 130 Formatted text is distinct from plain text and binary format in that 131 the non-textual information is encoded into textual characters, which 132 are assigned specialized meanings /not/ defined by the character set. 133 With a regular text editor and a standard keyboard (or other standard 134 input mechanism), a user can enter these textual characters to 135 express the non-textual meanings. For example, a character like "<" 136 no longer means "LESS-THAN SIGN"; it means the start of a tag or 137 element that affects the document in some way. 139 On the formal end of the spectrum is markup, a family of languages 140 for annotating a document in such a way that the annotations are 141 syntactically distinguishable from the text. Markup languages are 142 (reasonably) well-specified and tend to follow (mostly) standardized 143 syntax rules. Examples of markup languages include SGML, HTML, XML, 144 and LaTeX. Standardized rules lead to interoperability between markup 145 processors, but a skill requirement for new (human) users of the 146 language that they learn these rules in order to do useful work. This 147 imposition makes markup less accessible for non-technical users 148 (i.e., users who are unwilling or unable to invest in the requisite 149 skill development). 151 informal /---------formatted text----------\ formal 152 <------v-------------v-------------v-----------------------v----> 153 plain text informal markup formal markup binary format 154 (Markdown) (HTML, XML, etc.) 156 Figure 1: Degrees of Formality in Data Storage Formats for Text 158 On the informal end of the spectrum are lightweight markup languages. 159 In comparison with formal markup like XML, lightweight markup uses 160 simple syntax, and is designed to be easy for humans to enter with 161 basic text editors. Markdown, the subject of this document, is an 162 /informal/ plain text formatting syntax that is intentionally 163 targeted at non-technical users (i.e., users upon whom little to no 164 skill development is imposed) using unspecialized tools (i.e., text 165 boxes). Jeff Atwood once described these informal markup languages as 166 "humane" [HUMANE]. 168 1.2. Markdown Design Philosophy 170 Markdown specifically is a family of syntaxes that are based on the 171 original work of John Gruber with substantial contributions from 172 Aaron Swartz, released in 2004 [MARKDOWN]. Since its release a number 173 of web or web-facing applications have incorporated Markdown into 174 their text entry systems, frequently with custom extensions. Fed up 175 with the complexity and security pitfalls of formal markup languages 176 (e.g., HTML5) and proprietary binary formats (e.g., commercial word 177 processing software), yet unwilling to be confined to the 178 restrictions of plain text, many users have turned to Markdown for 179 document processing. Whole toolchains now exist to support Markdown 180 for online and offline projects. 182 Informality is a bedrock premise of Gruber's design. Gruber created 183 Markdown after disastrous experiences with strict XML and XHTML 184 processing of syndicated feeds. In Mark Pilgrim's "thought 185 experiment", several websites went down because one site included 186 invalid XHTML in a blog post, which was automatically copied via 187 trackbacks across other sites [DIN2MD]. These scenarios led Gruber to 188 believe that clients (e.g., web browsers) SHOULD try to make sense of 189 data that they receive, rather than rejecting data simply because it 190 fails to adhere to strict, unforgiving standards. (In [DIN2MD], 191 Gruber compared Postel's Law [RFC0793] with the XML standard, which 192 says: "Once a fatal error is detected [...] the processor MUST NOT 193 continue normal processing" [XML1.0-5].) As a result, there is no 194 such thing as "invalid" Markdown; there is no standard demanding 195 adherence to the Markdown syntax; there is no governing body that 196 guides or impedes its development. If the Markdown syntax does not 197 result in the "right" output (defined as output that the author 198 wants, not output that adheres to some dictated system of rules), 199 Gruber's view is that the author either should keep on experimenting, 200 or should change the processor to address the author's particular 201 needs (see [MARKDOWN] Readme and [MD102b8] perldoc; see also 202 [CATPICS]). 204 1.3. Uses of Markdown 206 Since its introduction in 2004, Markdown has enjoyed remarkable 207 success. Markdown works for users for three key reasons. First, the 208 markup instructions (in text) look similar to the markup that they 209 represent; therefore the cognitive burden to learn the syntax is low. 210 Second, the primary arbiter of the syntax's success is *running 211 code*. The tool that converts the Markdown to a presentable format, 212 and not a series of formal pronouncements by a standards body, is the 213 basis for whether syntactic elements matter. Third, Markdown has 214 become something of an Internet meme [INETMEME], in that Markdown 215 gets received, reinterpreted, and reworked as additional communities 216 encounter it. There are communities that are using Markdown for 217 scholarly writing [CITE], for screenplays [FOUNTAIN], for 218 mathematical formulae [CITE], and even for music annotation [CITE]. 219 Clearly, a screenwriter has no use for specialized Markdown syntax 220 for mathematicians; likewise, mathematicians do not need to identify 221 characters or props in common ways. The overall gist is that all of 222 these communities can take the common elements of Markdown (which are 223 rooted in the common elements of HTML circa 2004) and build on them 224 in ways that best fit their needs. 226 1.4. Uses of Labeling Markdown Content as text/markdown 228 The primary purpose of an Internet media type is to label "content" 229 on the Internet, as distinct from "files". Content is any computer- 230 readable format that can be represented as a primary sequence of 231 octets, along with type-specific metadata (parameters) and type- 232 agnostic metadata (protocol dependent). From this description, it is 233 apparent that appending ".markdown" to the end of a filename is not a 234 sufficient means to identify Markdown. Filenames are properties of 235 files in file systems, but Markdown frequently exists in databases or 236 content management systems (CMSes) where the file metaphor does not 237 apply. One CMS [RAILFROG] uses media types to select appropriate 238 processing, so a media type is necessary for the safe and 239 interoperable use of Markdown. 241 Unlike complete HTML documents, [MDSYNTAX] provides no means to 242 include metadata into the content stream. Several derivative flavors 243 have invented metadata incorporation schemes (e.g., [MULTIMD]), but 244 these schemes only address specific use cases. In general, the 245 metadata must be supplied via supplementary means in an encapsulating 246 protocol, format, or convention. The relationship between the content 247 and the metadata is not directly addressed here or in [MDMTREG]; 248 however, by identifying Markdown with a media type, Markdown content 249 can participate as a first-class citizen with a wide spectrum of 250 metadata schemes. 252 Finally, registering a media type through the IETF process is not 253 trivial. Markdown can no longer be considered a "vendor"-specific 254 innovation, but the registration requirements even in the vendor tree 255 have proven to be overly burdensome for most Markdown implementers. 256 Moreover, registering hundreds of Markdown variants with distinct 257 media types would impede interoperability: virtually all Markdown 258 content can be processed by virtually any Markdown processor, with 259 varying degrees of success. The goal of [MDMTREG] is to reduce all of 260 these burdens by having one media type that accommodates diversity 261 and eases registration. 263 2. Strategies for Preserving Media Type and Parameters 265 The purpose of this document and [MDMTREG] is to promote 266 interoperability between different Markdown-related systems, 267 preserving the author's intent. While [MARKDOWN] was designed by 268 Gruber in 2004 as a simple way to write blog posts and comments, as 269 of 2014 Markdown and its derivatives are rapidly becoming the formats 270 of record for many communities and use cases. While an individual 271 member of (or software tool for) a community can probably look at 272 some "Markdown" and declare its meaning intuitively obvious, software 273 systems in different communities (or different times) need help. 274 [MDSYNTAX] does not have a signaling mechanism like , so 275 tagging Markdown internally is simply out of the question. Once tags 276 or metadata are introduced, the content is no longer "just" Markdown. 278 Some commentators have suggested that an in-band signaling mechanism, 279 such as in Markdown link definitions at the top of the content, could 280 be used to signal the variant. Unfortunately this signaling mechanism 281 is incompatible with other Markdown variants (e.g., [PANDOC]) that 282 expect their own kinds of metadata at the top of the file. Markdown 283 content is just a stream of text; the semantics of that text can only 284 be furnished by context. 286 The media type and variant parameter in [MDMTREG] furnish this 287 missing context, while allowing for additional extensibility. This 288 section covers strategies for how an application might preserve 289 metadata when it leaves the domain of IETF protocols. 291 [MDMTREG] (draft-05) only defines two parameters: the charset 292 parameter (required for all text/* media types) and the variant 293 parameter. Character set interoperability is well-studied territory 294 [NB: CITE?] and so is not further covered here. The variant parameter 295 provides a simple identifier--nothing less or more. Variants are 296 allowed to define additional parameters when sent with the 297 text/markdown media type; the variant can also introduce control 298 information into the textual content stream (such as via a metadata 299 block). Neither [MDMTREG] nor this specification recommend any 300 particular approach. However, the philosophy behind [MDMTREG] is to 301 preserve formats rather than create new ones, since supporting 302 existing toolchains is more realistic than creating novel ones that 303 lack traction in the Markdown community. 305 2.1. Map to Filename and Attributes 307 This strategy is to map the media type, variant, and parameters to 308 "attributes" or "forks" in the local convention. Firstly, Markdown 309 content saved to a file should have an appropriate file extension 310 ending in .md or .markdown, which serves to disambiguate it from 311 other kinds of files. The character repertoire of variant identifiers 312 in [MDMTREG] is designed to be compatible with most filename 313 conventions. Therefore, a recommended strategy is to record the 314 variant identifier as the prefix to the file extension. For example, 315 for [PANDOC] content, a file could be named 316 "example.pandoc.markdown". 318 Many filesystems are case-sensitive or case-preserving; however, file 319 extensions tend to be all-lowercase. This document takes no position 320 on whether variant identifiers should be case-preserved or all- 321 lowercase when Markdown content is written to a file. However, when 322 the variant identifier is read to influence operational behavior, it 323 needs to be compared case-insensitively. 325 Many modern filesystems support "extended attributes", "alternate 326 data streams", or "resource forks". Some version control systems 327 support named properties. If the variant defines additional 328 parameters, these parameters should be stored in these resources, 329 where the parameter name includes the name of the resource, and the 330 parameter value is the value of the resource (data in the resource), 331 preferably UTF-8 encoded (unless the parameter definition explicitly 332 defines a different encoding or repertoire). The variant identifier 333 itself should be stored in a resource with a name including the term 334 "variant". 336 2.2. Store Headers in Adjacent File 338 This strategy is to save the Markdown content in a first file, and to 339 save the metadata (specifically the Content-Type: header) in a second 340 file with a filename that is rationally related to the first 341 filename. For example, if the first file is named "readme.markdown", 342 the second file could be named "readme.markdown.headers". (If stored 343 in a database, the analogy would be to store the metadata in a second 344 table with a field that is a key to the first table.) This header 345 file has the media type "message/global-headers" [RFC6533] (".u8hdr" 346 suggestion notwithstanding). 348 2.3. "Arm" Content with MIME Headers 350 This strategy is to save the Markdown content along with its headers 351 in a file, "arming" the content by prepending the MIME headers 352 (specifically the Content-Type: header). It should be appreciated 353 that the file is no longer a "Markdown file"; rather, it is an 354 Internet Message Format file (e.g., [RFC5322]) with a Markdown 355 content part. Therefore, the file should have an Internet message 356 extension (e.g., ".eml", ".msg", or ".u8msg"), not a Markdown 357 extension (e.g., ".md" or ".markdown"). 359 2.4. Create a Local Batch Script 361 This strategy is to translate the processing instructions inferred 362 from the Content-Type and other parameters (e.g., Content- 363 Disposition) into a sequence of commands in the local convention, 364 storing those commands in a batch script. For example, when a MIME- 365 aware client stores some Markdown to disk, the client can save a 366 Makefile in the same directory with commands that are appropriate 367 (and safe) for the local system. 369 2.5. Process the Markdown 371 This strategy is to process the Markdown into the formal markup, 372 which eliminates ambiguities. Once the Markdown is processed into 373 (for example) valid XHTML, an application can save a file as 374 "doc.xhtml" with no further loss of metadata. While unambiguous, this 375 process may not be reversible. 377 2.6. Rely on Context 379 This last strategy is to use or create context to determine how to 380 interpret the Markdown. For example, Markdown content that is of the 381 Fountain.io type [FOUNTAIN] could be saved with the filename 382 "script.fountain" instead of "script.markdown". Alternatively, 383 scripts could be stored in a "/screenplays" directory while other 384 kinds of Markdown could be stored elsewhere. For reasons that should 385 be intuitively obvious, this method is the most error-prone. 386 "Context" can be easily lost over time, and the trend of passing 387 Markdown between systems--taking them *out* of context--is 388 increasing. 390 2.7. Specific Strategies 392 2.7.1. Subversion 394 This subsection covers a preservation strategy in Subversion [SVN], a 395 common client-server version control system. 397 Subversion supports named properties. The "svn:mime-type" property 398 duplicates the entire Content-Type header, so parameters SHOULD be 399 stored there. The filename SHOULD be consistent with this Content- 400 Type header, i.e., the extension SHOULD be the variant identifier 401 plus ".markdown". 403 [[TODO: Versions of Subversion after [[1.x]] treat svn:mime-type as 404 UTF-8 encoded, rather than US-ASCII. (See [RFC6532].) Therefore, the 405 encoding of [RFC2231] will not be necessary in the vast majority of 406 cases in newer versions. However, both for backwards compatibility 407 and for support for non-Unicode character sets, [RFC2231] still needs 408 to be supported.]] 410 [[TODO: Where to store Content-Disposition?]] 412 2.7.2. Git 414 This subsection covers a preservation strategy in Git [GIT], a common 415 distributed version control system. 417 Versions of Git as of the time of this writing do not support 418 arbitrary metadata storage; however, third-party projects add this 419 support. 421 If Git is used without a metadata storage service, then a reasonable 422 strategy is to include the variant identifier in the filename. The 423 encoding of the file should be transcoded to UTF-8. For other 424 properties, a header file should be recorded alongside the Markdown 425 file in accordance with Section 2.2. The contents of the header file 426 should be consistent with the rest of this paragraph, i.e., the 427 charset parameter should be "UTF-8" and the variant parameter should 428 match the identifier in the filename. 430 If a metadata storage service is used with Git, then use a convention 431 that is most analogous to the service. For example, the "metastore" 432 project emulates extended attributes (xattrs) of a POSIX-like system, 433 so whatever "xattr" methodology is developed would be usable with 434 metastore and Git. 436 3. Registration Templates for Common Markdown Syntaxes 438 The purpose of this section is to register certain syntaxes in the 439 Markdown Syntaxes Registry [MDMTREG] because they illustrate 440 particularly interesting use cases or are broadly applicable to the 441 Internet community; thus, these syntaxes would benefit from the level 442 of review associated with publication as IETF documents. 444 3.1. MultiMarkdown 446 Identifier: MultiMarkdown 448 Name: MultiMarkdown 450 Description: 451 MultiMarkdown (MMD) is a superset of "Original". It adds multiple 452 syntax features (tables, footnotes, and citations, to name a few), 453 and is intended to output to various formats. Additionally, it builds 454 in "smart" typography for various languages (proper left- and right- 455 sided quotes, for example). 457 Additional Parameters: 458 options: String with zero or more of the following WSP-delimited 459 tokens: 461 "memoir" / "beamer" 462 "full" / "snippet" 463 "process-html" 464 "random-footnote-identifiers" 465 "accept" 466 "reject" 467 "nosmart" 468 "nonotes" 469 "nolabels" 470 "nomask" 472 The meanings of these tokens are defined in the 473 MultiMarkdown documentation. 475 References: 476 478 Contact Information: 479 (individual) Fletcher T. Penney 480 482 3.2. GitHub Flavored Markdown 484 Identifier: GFM 486 Name: GitHub Flavored Markdown 488 Description: 489 "Original" with the following differences: 490 1. Multiple underscores in words 491 2. URL (URI) autolinking 492 3. Strikethrough 493 4. Fenced code blocks 494 5. Syntax highlighting 495 6. Tables (- for rows; | for columns; : for alignment) 496 7. Only some HTML allowed; sanitization is integral 497 to the format 499 References: 500 501 503 Contact Information: 504 (corporate) GitHub, Inc. 505 [[Vicent Marti ??]] 507 3.3. Pandoc 509 Identifier: pandoc 511 Name: Pandoc 513 Description: 514 Markdown is designed to be easy to write and to read: the content 515 should be publishable as-is, as plain text, without looking like it 516 has been marked up with tags or formatting instructions. Yet whereas 517 "Original" has HTML generation in mind, pandoc is designed for 518 multiple output formats. Thus, while pandoc allows the embedding of 519 raw HTML, it discourages it, and provides other, non-HTMLish ways of 520 representing important document elements like definition lists, 521 tables, mathematics, and footnotes. 523 Additional Parameters: 524 extensions: String with an optional starting syntax token, followed 525 by a "+" and "-" delimited list of extension tokens. "+" 526 preceding an extension token turns the extension on; "-" 527 turns the extension off. The starting syntax tokens are 528 "markdown", "markdown_strict", "markdown_phpextra", and 529 "markdown_github". If no starting syntax token is given, 530 "markdown" is assumed. The extension tokens include: 532 [[Stuff to turn off:]] 534 escaped_line_breaks 535 blank_before_header 536 header_attributes 537 auto_identifiers 538 implicit_header_references 539 blank_before_blockquote 540 fenced_code_blocks 541 fenced_code_attributes 542 line_blocks 543 fancy_lists 544 startnum 545 definition_lists 546 example_lists 547 table_captions 548 simple_tables 549 multiline_tables 550 grid_tables 551 pipe_tables 552 pandoc_title_block 553 yaml_metadata_block 554 all_symbols_escapable 555 intraword_underscores 556 strikeout 557 superscript 558 subscript 559 inline_code_attributes 560 tex_math_dollars 561 raw_html 562 markdown_in_html_blocks 563 native_divs 564 native_spans 565 raw_tex 566 latex_macros 567 implicit_figures 568 footnotes 569 inline_notes 570 citations 572 [[New stuff:]] 574 lists_without_preceding_blankline 575 hard_line_breaks 576 ignore_line_breaks 577 tex_math_single_backslash 578 tex_match_double_backslash 579 markdown_attribute 580 mmd_title_block 581 abbreviations 582 autolink_bare_uris 583 ascii_identifiers 584 link_attributes 585 mmd_header_identifiers 586 compact_definition_lists 588 Fragment Identifiers: 589 Pandoc defines fragment identifiers using the in the 590 {# .class ...} production (PHP Markdown Extra attribute block). 591 This syntax works for Header Identifiers and Code Block Identifiers. 593 References: 594 596 Contact Information: 597 (individual) Prof. John MacFarlane 598 600 3.4. Fountain (Fountain.io) 602 Identifier: Fountain 604 Name: Fountain 606 Description: 607 Fountain is a simple markup syntax for writing, editing and sharing 608 screenplays in plain, human-readable text. Fountain allows you to 609 work on your screenplay anywhere, on any computer or tablet, using 610 any software that edits text files. 612 Fragment Identifiers: 613 See and 614 . In the following 615 fragment identifiers, the and productions MUST have "/" 616 characters percent-encoded. 618 #/ Title Page (acts as metadata). 619 #/ Title Page; is the key string. 620 # *("/" ) 621 Section or subsection. The .. 622 productions are the text of the Section line, 623 with whitespace trimmed from both ends. 625 Sub-sections (sections with multiple # at 626 at the beginning of the line in the source) 627 are addressed hierarchically by preceding 628 the sub-section with higher-order 629 sections. If the section hierarchy "skips", 630 e.g., # to ###, use a blank section name, 631 e.g., #Section/ACT%20I//PATIO%20SCENE. 633 References: 634 636 Contact Information: 637 (individual) Stu Maschwitz 638 (individual) John August 640 3.5. CommonMark 642 Identifier: CommonMark 644 Name: CommonMark 646 Description: 647 CommonMark is a standard, unambiguous syntax specification for 648 Markdown, along with a suite of comprehensive tests to validate 649 Markdown implementations against this specification. The maintainers 650 believe that CommonMark is necessary, even essential, for the future 651 of Markdown. 653 Compared to "Original", CommonMark is much longer and in a few 654 instances contradicts "Original" based on seasoned experience. 655 Although CommonMark specifically does not mandate any particular 656 encoding for the input content, CommonMark draws in more of Unicode, 657 UTF-8, and HTML (including HTML5) than "Original". 659 This registration always refers to the latest version or an 660 unspecified version (receiver's choice). Version 0.13 of the 661 CommonMark specification was released 2014-12-10. 663 References: 664 666 Contact Information: 667 (individual) John MacFarlane 668 (individual) David Greenspan 669 (individual) Vicent Marti 670 (individual) Neil Williams 671 (individual) Benjamin Dumke-von der Ehe 672 (individual) Jeff Atwood 674 3.6. kramdown-rfc2629 (Markdown for RFCs) 676 Identifier: kramdown-rfc2629 678 Name: Markdown for RFCs 680 Description: 681 kramdown is a markdown parser by Thomas Leitner, which has a number 682 of backends for generating HTML, Latex, and Markdown again. kramdown- 683 rfc2629 is an additional backend to that: It allows the generation of 684 XML2RFC XML markup (also known as RFC 2629 compliant markup). 686 References: 687 689 Contact Information: 690 (individual) Carsten Bormann 692 3.7. rfc7328 (Pandoc2rfc) 694 Identifier: rfc7328 696 Name: Pandoc2rfc 698 Description: 699 Pandoc2rfc allows authors to write in "pandoc" that is then 700 transformed to XML and given to xml2rfc. The conversions are, in a 701 way, amusing, as we start off with (almost) plain text, use elaborate 702 XML, and end up with plain text again. 704 References: 705 RFC 7328 706 708 Contact Information: 709 (individual) R. (Miek) Gieben 711 3.8. PHP Markdown Extra 713 Identifier: Extra 715 Name: Markdown Extra 717 Description: 718 Markdown Extra is an extension to PHP Markdown implementing some 719 features currently not available with the plain Markdown syntax. 720 Markdown Extra is available as a separate parser class in PHP 721 Markdown Lib. Other implementations include Maruku (Ruby) and Python 722 Markdown. Markdown Extra is supported in several content management 723 systems, including Drupal, TYPO3, and MediaWiki. 725 Fragment Identifiers: 726 Markdown Extra defines fragment identifiers using the in the 727 {# .class ...} production (attribute block). This syntax works 728 for headers, fenced code blocks, links, and images. 730 References: 731 733 Contact Information: 734 (individual) Michel Fortin 736 4. Examples for Common Markdown Syntaxes 738 This section provides examples of the variants registered in Appendix 739 C. 741 4.1. MultiMarkdown 743 4.2. GitHub Flavored Markdown 745 4.3. Pandoc 747 4.4. Fountain (Fountain.io) 749 4.5. CommonMark 751 4.6. kramdown-rfc2629 (Markdown for RFCs) 753 4.7. rfc7328 (Pandoc2rfc) 755 [[TODO: complete.]] 757 5. IANA Considerations 759 IANA is asked to register the syntaxes specified in Section 3 in the 760 Markdown Variants Registry. 762 6. Security Considerations 764 See the respective syntax descriptions and output media type 765 registrations for their respective security considerations. 767 7. References 769 7.1. Normative References 771 [MARKDOWN] Gruber, J., "Daring Fireball: Markdown", December 2004, 772 . 774 [MDSYNTAX] Gruber, J., "Daring Fireball: Markdown Syntax 775 Documentation", December 2004, 776 . 778 [MDMTREG] Leonard, S., "The text/markdown Media Type", draft-ietf- 779 appsawg-text-markdown-05 (work in progress), December 780 2014. 782 [RFC5147] Wilde, E. and M. Duerst, "URI Fragment Identifiers for the 783 text/plain Media Type", RFC 5147, April 2008. 785 [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, 786 October 2008. 788 7.2. Informative References 790 [HUMANE] Atwood, J., "Is HTML a Humane Markup Language?", May 2008, 791 . 794 [DIN2MD] Gruber, J., "Dive Into Markdown", March 2004, 795 . 797 [MD102b8] Gruber, J., "[ANN] Markdown.pl 1.0.2b8", May 2007, 798 , . 802 [CATPICS] Gruber, J. and M. Arment, "The Talk Show: Ep. 88: 'Cat 803 Pictures' (Side 1)", July 2014, 804 . 806 [INETMEME] Solon, O., "Richard Dawkins on the internet's hijacking of 807 the word 'meme'", June 2013, 808 , . 811 [MULTIMD] Penney, F., "MultiMarkdown", April 2014, 812 . 814 [PANDOC] MacFarlane, J., "Pandoc", 2014, 815 . 817 [RAILFROG] Railfrog Team, "Railfrog", April 2009, 818 . 820 [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 821 793, September 1981. 823 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 824 Word Extensions: Character Sets, Languages, and 825 Continuations", RFC 2231, November 1997. 827 [RFC4263] Lilly, B., "Media Subtype Registration for Media Type 828 text/troff", RFC 4263, January 2006. 830 [RFC6533] Hansen, T., Ed., Newman, C. and A. Melnikov, 831 "Internationalized Delivery Status and Disposition 832 Notifications", RFC 6533, February 2012. 834 [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type 835 Specifications and Registration Procedures", BCP 13, RFC 836 6838, January 2013. 838 [XML1.0-5] Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and 839 F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth 840 Edition)", World Wide Web Consortium Recommendation REC- 841 xml-20081126, November 2008, 842 . 844 [FOUNTAIN] Maschwitz, S. and J. August, "Fountain | A markup language 845 for screenwriting.", 2014, . 847 [FTSYNTAX] Maschwitz, S. and J. August, "Syntax - Fountain | A markup 848 language for screenwriting.", 1.1, March 2014, 849 . 851 [SVN] Apache Subversion, December 2014, 852 . 854 [GIT] Git, December 2014, . 856 Author's Address 858 Sean Leonard 859 Penango, Inc. 860 5900 Wilshire Boulevard 861 21st Floor 862 Los Angeles, CA 90036 863 USA 865 EMail: dev+ietf@seantek.com 866 URI: http://www.penango.com/