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'I-D.appsawg-media-type-suffix-regs' == Outdated reference: A later version (-04) exists of draft-ietf-appsawg-mime-default-charset-01 ** Obsolete normative reference: RFC 3023 (Obsoleted by RFC 7303) ** Obsolete normative reference: RFC 3979 (Obsoleted by RFC 8179) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) -- Obsolete informational reference (is this intentional?): RFC 2048 (Obsoleted by RFC 4288, RFC 4289) -- Obsolete informational reference (is this intentional?): RFC 2616 (Obsoleted by RFC 7230, RFC 7231, RFC 7232, RFC 7233, RFC 7234, RFC 7235) -- Obsolete informational reference (is this intentional?): RFC 4288 (Obsoleted by RFC 6838) -- Obsolete informational reference (is this intentional?): RFC 5987 (Obsoleted by RFC 8187) Summary: 3 errors (**), 0 flaws (~~), 3 warnings (==), 9 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group N. Freed 3 Internet-Draft Oracle 4 Obsoletes: 4288 (if approved) J. Klensin 5 Intended status: BCP 6 Expires: December 22, 2012 T. Hansen 7 AT&T Laboratories 8 June 20, 2012 10 Media Type Specifications and Registration Procedures 11 draft-ietf-appsawg-media-type-regs-14 13 Abstract 15 This document defines procedures for the specification and 16 registration of media types for use in HTTP, MIME and other Internet 17 protocols. 19 Status of this Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on December 22, 2012. 36 Copyright Notice 38 Copyright (c) 2012 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 54 1.1. Historical Note . . . . . . . . . . . . . . . . . . . . . 4 55 1.2. Conventions Used in This Document . . . . . . . . . . . . 5 56 2. Media Type Registration Preliminaries . . . . . . . . . . . . 5 57 3. Registration Trees and Subtype Names . . . . . . . . . . . . . 5 58 3.1. Standards Tree . . . . . . . . . . . . . . . . . . . . . . 5 59 3.2. Vendor Tree . . . . . . . . . . . . . . . . . . . . . . . 6 60 3.3. Personal or Vanity Tree . . . . . . . . . . . . . . . . . 7 61 3.4. Unregistered x. Tree . . . . . . . . . . . . . . . . . . . 8 62 3.5. Additional Registration Trees . . . . . . . . . . . . . . 8 63 4. Registration Requirements . . . . . . . . . . . . . . . . . . 8 64 4.1. Functionality Requirement . . . . . . . . . . . . . . . . 8 65 4.2. Naming Requirements . . . . . . . . . . . . . . . . . . . 9 66 4.2.1. Text Media Types . . . . . . . . . . . . . . . . . . . 10 67 4.2.2. Image Media Types . . . . . . . . . . . . . . . . . . 11 68 4.2.3. Audio Media Types . . . . . . . . . . . . . . . . . . 11 69 4.2.4. Video Media Types . . . . . . . . . . . . . . . . . . 11 70 4.2.5. Application Media Types . . . . . . . . . . . . . . . 11 71 4.2.6. Multipart and Message Media Types . . . . . . . . . . 12 72 4.2.7. Additional Top-level Types . . . . . . . . . . . . . . 12 73 4.2.8. Structured Syntax Name Suffixes . . . . . . . . . . . 12 74 4.2.9. Deprecated Aliases . . . . . . . . . . . . . . . . . . 13 75 4.3. Parameter Requirements . . . . . . . . . . . . . . . . . . 13 76 4.4. Canonicalization and Format Requirements . . . . . . . . . 14 77 4.5. Interchange Recommendations . . . . . . . . . . . . . . . 15 78 4.6. Security Requirements . . . . . . . . . . . . . . . . . . 16 79 4.7. Requirements specific to XML media types . . . . . . . . . 17 80 4.8. Encoding Requirements . . . . . . . . . . . . . . . . . . 17 81 4.9. Usage and Implementation Non-requirements . . . . . . . . 18 82 4.10. Publication Requirements . . . . . . . . . . . . . . . . . 18 83 4.11. Fragment Identifier Requirements . . . . . . . . . . . . . 19 84 4.12. Additional Information . . . . . . . . . . . . . . . . . . 19 85 5. Media Type Registration Procedures . . . . . . . . . . . . . . 20 86 5.1. Preliminary Community Review . . . . . . . . . . . . . . . 20 87 5.2. Submit request to IANA . . . . . . . . . . . . . . . . . . 20 88 5.2.1. Provisional Registrations . . . . . . . . . . . . . . 21 89 5.3. Review and Approval . . . . . . . . . . . . . . . . . . . 21 90 5.4. Comments on Media Type Registrations . . . . . . . . . . . 22 91 5.5. Change Procedures . . . . . . . . . . . . . . . . . . . . 22 92 5.6. Registration Template . . . . . . . . . . . . . . . . . . 23 93 6. Structured Syntax Suffix Registration Procedures . . . . . . . 24 94 6.1. Change Procedures . . . . . . . . . . . . . . . . . . . . 25 95 6.2. Structured Syntax Suffix Registration Template . . . . . . 25 97 7. Security Considerations . . . . . . . . . . . . . . . . . . . 26 98 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 99 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27 100 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28 101 10.1. Normative References . . . . . . . . . . . . . . . . . . . 28 102 10.2. Informative References . . . . . . . . . . . . . . . . . . 29 103 Appendix A. Grandfathered Media Types . . . . . . . . . . . . . . 30 104 Appendix B. Changes Since RFC 4288 . . . . . . . . . . . . . . . 30 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32 107 1. Introduction 109 Recent Internet protocols have been carefully designed to be easily 110 extensible in certain areas. In particular, many protocols, 111 including but not limited to HTTP [RFC2616] and MIME [RFC2045], are 112 capable of carrying arbitrary labeled content. 114 The mechanism used to label such content is a media type, consisting 115 of a top-level type and a subtype, which is further structured into 116 trees. Optionally, media types can define companion data, known as 117 parameters. 119 A registration process is needed for these labels, so that that the 120 set of such values are defined in a reasonably orderly, well- 121 specified, and public manner. 123 This document specifies the criteria for media type registrations and 124 defines the procedures to be used to register media types (Section 5) 125 as well as media type structured suffixes (Section 6) in the Internet 126 Assigned Numbers Authority (IANA) central registry. 128 The location of the media type registry managed by these procedures 129 is: 131 http://www.iana.org/assignments/media-types/ 133 1.1. Historical Note 135 The media type registration process was initially defined for 136 registering media types for use in the context of the asynchronous 137 Internet mail environment. In this mail environment there is a need 138 to limit the number of possible media types, to increase the 139 likelihood of interoperability when the capabilities of the remote 140 mail system are not known. As media types are used in new 141 environments in which the proliferation of media types is not a 142 hindrance to interoperability, the original procedure proved 143 excessively restrictive and had to be generalized. This was 144 initially done in [RFC2048], but the procedure defined there was 145 still part of the MIME document set. The media type specification 146 and registration procedure is now a separate document, to make it 147 clear that it is independent of MIME. 149 It may be desirable to restrict the use of media types to specific 150 environments or to prohibit their use in other environments. This 151 specification incorporates such restrictions into media type 152 registrations in a systematic way. See Section 4.9 for additional 153 discussion. 155 1.2. Conventions Used in This Document 157 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 158 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 159 document are to be interpreted as described in [RFC2119] when they 160 appear in ALL CAPS. They may also appear in lower or mixed case as 161 plain English words, without any normative meaning. 163 This specification makes use of the Augmented Backus-Naur Form (ABNF) 164 [RFC5234] notation, including the core rules defined in Appendix A of 165 that document. 167 2. Media Type Registration Preliminaries 169 Registration of a new media type or types starts with the 170 construction of a registration proposal. Registration may occur 171 within several different registration trees that have different 172 requirements, as discussed below. In general, a new registration 173 proposal is circulated and reviewed in a fashion appropriate to the 174 tree involved. The media type is then registered if the proposal is 175 acceptable. The following sections describe the requirements and 176 procedures used for each of the different registration trees. 178 3. Registration Trees and Subtype Names 180 In order to increase the efficiency and flexibility of the 181 registration process, different structures of subtype names can be 182 registered to accommodate the different natural requirements for, 183 e.g., a subtype that will be recommended for wide support and 184 implementation by the Internet community, or a subtype that is used 185 to move files associated with proprietary software. The following 186 subsections define registration "trees" that are distinguished by the 187 use of faceted names, e.g., subtype names that begin with a a "tree." 188 prefix. Note that some media types defined prior to this document do 189 not conform to the naming conventions described below. See Appendix 190 A for a discussion of them. 192 3.1. Standards Tree 194 The standards tree is intended for types of general interest to the 195 Internet community. Registrations in the standards tree MUST be 196 either: 198 1. in the case of registrations in IETF specifications, approved 199 directly by the IESG, or 201 2. registered by a recognized standards body using the 202 "Specification Required" IANA registration policy [RFC5226] 203 (which implies Expert Review). 205 The first procedure is used for registering registrations from IETF 206 Consensus documents, or in rare cases when registering a 207 grandfathered (see Appendix A) and/or otherwise incomplete 208 registration is in the interest of the Internet community. The 209 registration proposal MUST be published as an RFC. When the RFC is 210 in the IETF stream it is an IETF Consensus RFC, which can be on the 211 Standards Track, a BCP, Informational, or Experimental. 212 Registrations published in non-IETF RFC streams are also allowed, and 213 require IESG approval. A registration can be either in a standalone 214 "registration only" RFC or incorporated into a more general 215 specification of some sort. 217 In the second case the IESG makes a one time decision on whether the 218 registration submitter represents a recognized standards body; after 219 that, a Media Types Reviewer (Designated Expert or a group of 220 Designated Experts) performs the Expert Review as specified in this 221 document. Subsequent submissions from the same source do not involve 222 the IESG. The format MUST be described by a formal standards 223 specification produced by the submitting standards body. 225 Media types in the standards tree MUST NOT have faceted names, unless 226 they are grandfathered in using the process described in Appendix A. 228 The "owner" of a media type registered in the standards tree is 229 assumed to be the standards body itself. Modification or alteration 230 of the specification uses the same level of processing (e.g., a 231 registration submitted on Standards Track can be revised in another 232 Standards Track RFC, but cannot be revised in an Informational RFC) 233 required for the initial registration. 235 Standards-tree registrations from recognized standards bodies are 236 submitted directly to the IANA, where they will undergo Expert Review 237 [RFC5226] prior to approval. In this case, the Expert Reviewer(s) 238 will, among other things, ensure that the required specification 239 provides adequate documentation. 241 3.2. Vendor Tree 243 The vendor tree is used for media types associated with publicly 244 available products. "Vendor" and "producer" are construed very 245 broadly in this context and are considered equivalent. Note that 246 industry consortia as well as non-commercial entities that do not 247 qualify as recognized standards bodies can quite appropriately 248 register media types in the vendor tree. 250 A registration may be placed in the vendor tree by anyone who needs 251 to interchange files associated with some product or set of products. 252 However, the registration properly belongs to the vendor or 253 organization producing the software that employs the type being 254 registered, and that vendor or organization can at any time elect to 255 assert ownership of a registration done by a third party in order to 256 correct or update it. See Section 5.5 for additional information. 258 When a third party registers a type on behalf of someone else both 259 entities SHOULD be noted in the Change Controller field in the 260 registration. One possible format for this would be "Foo, on behalf 261 of Bar". 263 Registrations in the vendor tree will be distinguished by the leading 264 facet "vnd.". That may be followed, at the discretion of the 265 registrant, by either a media subtype name from a well-known producer 266 (e.g., "vnd.mudpie") or by an IANA-approved designation of the 267 producer's name that is followed by a media type or product 268 designation (e.g., vnd.bigcompany.funnypictures). 270 While public exposure and review of media types to be registered in 271 the vendor tree is not required, using the media-types@iana.org 272 mailing list for review is encouraged to improve the quality of those 273 specifications. Registrations in the vendor tree may be submitted 274 directly to the IANA, where they will undergo Expert Review [RFC5226] 275 prior to approval. 277 3.3. Personal or Vanity Tree 279 Registrations for media types created experimentally or as part of 280 products that are not distributed commercially may be registered in 281 the personal or vanity tree. The registrations are distinguished by 282 the leading facet "prs.". 284 The owner of "personal" registrations and associated specifications 285 is the person or entity making the registration, or one to whom 286 responsibility has been transferred as described below. 288 While public exposure and review of media types to be registered in 289 the personal tree is not required, using the media-types@iana.org 290 mailing list (see Section 5.1) for review is encouraged to improve 291 the quality of those specifications. Registrations in the personal 292 tree may be submitted directly to the IANA, where they will undergo 293 Expert Review [RFC5226] prior to approval. 295 3.4. Unregistered x. Tree 297 Subtype names with "x." as the first facet may be used for types 298 intended exclusively for use in private, local environments. Types 299 in this tree cannot be registered and are intended for use only with 300 the active agreement of the parties exchanging them. 302 However, with the simplified registration procedures described above 303 for vendor and personal trees, it should rarely, if ever, be 304 necessary to use unregistered types. Therefore, use of types in the 305 "x." tree is strongly discouraged. 307 Note that types with names beginning with "x-" are no longer 308 considered to be members of this tree (see [I-D.ietf-appsawg-xdash]). 309 Also note that if a generally useful and widely deployed type 310 incorrectly ends up with an "x-" name prefix, it MAY be registered 311 using its current name in an alternate tree by following the 312 procedure defined in Appendix A. 314 3.5. Additional Registration Trees 316 From time to time and as required by the community, new top-level 317 registration trees may be created by IETF Standards Action. It is 318 explicitly assumed that these trees may be created for external 319 registration and management by well-known permanent bodies; for 320 example, scientific societies may register media types specific to 321 the sciences they cover. In general, the quality of review of 322 specifications for one of these additional registration trees is 323 expected to be equivalent to registrations in the standards tree by a 324 recognized Standards Development Organization. When the IETF 325 performs such review, it needs to consider the greater expertise of 326 the requesting body with respect to the subject media type. 328 4. Registration Requirements 330 Media type registrations are all expected to conform to various 331 requirements laid out in the following sections. Note that 332 requirement specifics sometimes vary depending on the registration 333 tree, again as detailed in the following sections. 335 4.1. Functionality Requirement 337 Media types MUST function as actual media formats. Registration of 338 things that are better thought of as a transfer encoding, as a 339 charset, or as a collection of separate entities of another type, is 340 not allowed. For example, although applications exist to decode the 341 base64 transfer encoding [RFC2045], base64 cannot be registered as a 342 media type. 344 This requirement applies regardless of the registration tree 345 involved. 347 4.2. Naming Requirements 349 All registered media types MUST be assigned top-level type and 350 subtype names. The combination of these names serves to uniquely 351 identify the media type, and the subtype name facet (or the absence 352 of one) identifies the registration tree. Both top-level type and 353 subtype names are case-insensitive. 355 Type and subtype names MUST conform to the following ABNF: 357 type-name = restricted-name 358 subtype-name = restricted-name 360 restricted-name = restricted-name-first *126restricted-name-chars 361 restricted-name-first = ALPHA / DIGIT 362 restricted-name-chars = ALPHA / DIGIT / "!" / "#" / 363 "$" / "&" / "-" / "^" / "_" 364 restricted-name-chars =/ "." ; Characters before first dot always 365 ; specify a facet name 366 restricted-name-chars =/ "+" ; Characters after last plus always 367 ; specify a structured syntax suffix 369 Note that this syntax is somewhat more restrictive than what is 370 allowed by the ABNF in section 5.1 of [RFC2045] or section 4.2 of 371 [RFC4288]. Also note that while this syntax allows names of up to 372 127 characters, implementation limits may make such long names 373 problematic. For this reason the components of names SHOULD be 374 limited to 64 characters. 376 Although the name syntax treats "." as equivalent to any other 377 character, characters before any initial "." always specify the 378 registration facet. Note that this means that facet-less standards 379 tree registrations cannot use periods in the subtype name. 381 Similarly, "+" is used in subtype names to introduce a structured 382 syntax specifier suffix. Structured syntax suffix requirements are 383 specified in Section 4.2.8. 385 While it is possible for a given media type to be assigned additional 386 names, the use of different names to identify the same media type is 387 discouraged. 389 These requirements apply regardless of the registration tree 390 involved. 392 The choice of top-level type MUST take into account the nature of 393 media type involved. New subtypes of top-level types MUST conform to 394 the restrictions of the top-level type, if any. The following 395 sections describe each of the initial set of top-level types and 396 their associated restrictions. Additionally, various protocols, 397 including but not limited to HTTP and MIME, MAY impose additional 398 restrictions on the media types they can transport. (See [RFC2046] 399 for additional information on the restrictions MIME imposes.) 401 4.2.1. Text Media Types 403 The "text" top-level type is intended for sending material that is 404 principally textual in form. 406 Many subtypes of text, notably including the subtype "text/plain", 407 which is a generic subtype for plain text defined in [RFC2046], 408 define a "charset" parameter. If a "charset" parameter is defined 409 for a particular subtype of text, it MUST be used to specify a 410 charset name defined in accordance to the procedures laid out in 411 [RFC2978]. 413 As specified in [I-D.ietf-appsawg-mime-default-charset], a "charset" 414 parameter SHOULD NOT be specified when charset information is 415 transported inside the payload (e.g., as in "text/xml"). 417 If a "charset" parameter is specified, it SHOULD be a required 418 parameter, eliminating the options of specifying a default value. If 419 there is a strong reason for the parameter to be optional despite 420 this advice, each subtype MAY specify its own default value, or 421 alternately, it MAY specify that there is no default value. Finally, 422 the "UTF-8" charset [RFC3629] SHOULD be selected as the default. See 423 [I-D.ietf-appsawg-mime-default-charset] for additional information on 424 the use of "charset" parameters in conjunction with subtypes of text. 426 Regardless of what approach is chosen, all new text/* registrations 427 MUST clearly specify how the charset is determined; relying on the 428 US-ASCII default defined in Section 4.1.2 of [RFC2046] is no longer 429 permitted. If explanatory text is needed this SHOULD be placed in 430 the additional information section of the registration. 432 Plain text does not provide for or allow formatting commands, font 433 attribute specifications, processing instructions, interpretation 434 directives, or content markup. Plain text is seen simply as a linear 435 sequence of characters, possibly interrupted by line breaks or page 436 breaks. Plain text MAY allow the stacking of several characters in 437 the same position in the text. Plain text in scripts like Arabic and 438 Hebrew may also include facilities that allow the arbitrary mixing of 439 text segments with different writing directions. 441 Beyond plain text, there are many formats for representing what might 442 be known as "rich text". An interesting characteristic of many such 443 representations is that they are to some extent readable even without 444 the software that interprets them. It is useful to distinguish them, 445 at the highest level, from such unreadable data as images, audio, or 446 text represented in an unreadable form. In the absence of 447 appropriate interpretation software, it is reasonable to present 448 subtypes of "text" to the user, while it is not reasonable to do so 449 with most non-textual data. Such formatted textual data can be 450 represented using subtypes of "text". 452 4.2.2. Image Media Types 454 A top-level type of "image" indicates that the content specifies one 455 or more individual images. The subtype names the specific image 456 format. 458 4.2.3. Audio Media Types 460 A top-level type of "audio" indicates that the content contains audio 461 data. The subtype names the specific audio format. 463 4.2.4. Video Media Types 465 A top-level type of "video" indicates that the content specifies a 466 time-varying-picture image, possibly with color and coordinated 467 sound. The term 'video' is used in its most generic sense, rather 468 than with reference to any particular technology or format, and is 469 not meant to preclude subtypes such as animated drawings encoded 470 compactly. 472 Note that although in general the mixing of multiple kinds media in a 473 single body is discouraged [RFC2046], it is recognized that many 474 video formats include a representation for synchronized audio and/or 475 text, and this is explicitly permitted for subtypes of "video". 477 4.2.5. Application Media Types 479 The "application" top-level type is to be used for discrete data that 480 do not fit under any of the other type names, and particularly for 481 data to be processed by some type of application program. This is 482 information that must be processed by an application before it is 483 viewable or usable by a user. Expected uses for the "application" 484 type name include but are not limited to file transfer, spreadsheets, 485 presentations, scheduling data, and languages for "active" 486 (computational) material. (The last, in particular, can pose 487 security problems that must be understood by implementors. The 488 "application/postscript" media type registration in [RFC2046] 489 provides a good example of how to handle these issues.) 491 For example, a meeting scheduler might define a standard 492 representation for information about proposed meeting dates. An 493 intelligent user agent would use this information to conduct a dialog 494 with the user, and might then send additional material based on that 495 dialog. More generally, there have been several "active" languages 496 developed in which programs in a suitably specialized language are 497 transported to a remote location and automatically run in the 498 recipient's environment. Such applications may be defined as 499 subtypes of the "application" top-level type. 501 The subtype of "application" will often either be the name or include 502 part of the name of the application for which the data are intended. 503 This does not mean, however, that any application program name may 504 simply be used freely as a subtype of "application"; the subtype 505 needs to be registered. 507 4.2.6. Multipart and Message Media Types 509 Multipart and message are composite types, that is, they provide a 510 means of encapsulating zero or more objects, each one a separate 511 media type. 513 All subtypes of multipart and message MUST conform to the syntax 514 rules and other requirements specified in [RFC2046] and amended by 515 Section 3.5 of [RFC6532]. 517 4.2.7. Additional Top-level Types 519 In some cases a new media type may not "fit" under any currently 520 defined top-level type names. Such cases are expected to be quite 521 rare. However, if such a case does arise a new type name can be 522 defined to accommodate it. Such a definition MUST be done via 523 standards-track RFC; no other mechanism can be used to define 524 additional type names. 526 4.2.8. Structured Syntax Name Suffixes 528 XML in MIME [RFC3023] defined the first such augmentation to the 529 media type definition to additionally specify the underlying 530 structure of that media type. To quote: 532 This document also standardizes a convention (using the suffix 533 '+xml') for naming media types ... when those media types 534 represent XML MIME (Multipurpose Internet Mail Extensions) 535 entities. 537 That is, it specified a suffix (in that case, "+xml") to be appended 538 to the base subtype name. 540 Since this was published, the de facto practice has arisen for using 541 this suffix convention for other well-known structuring syntaxes. In 542 particular, media types have been registered with suffixes such as 543 "+der", "+fastinfoset" and "+json". This specification formalizes 544 this practice and sets up a registry for structured type name 545 suffixes. 547 The primary guideline for whether a structured type name suffix is 548 registrable is that it be described by a readily-available 549 description, preferably within a document published by an established 550 standards organization, and for which there's a reference that can be 551 used in a Normative References section of an RFC. 553 Media types that make use of a named structured syntax SHOULD use the 554 appropriate registered "+suffix" for that structured syntax when they 555 are registered. By the same token, media types MUST NOT be given 556 names incorporating suffixes for structured syntaxes they do not 557 actually employ. "+suffix" constructs for as-yet unregistered 558 structured syntaxes SHOULD NOT be used, given the possibility of 559 conflicts with future suffix definitions. 561 4.2.9. Deprecated Aliases 563 In some cases a single media type may have been widely deployed prior 564 to registration under multiple names. In such cases a preferred name 565 MUST be chosen for the media type and applications MUST use this to 566 be compliant with the type's registration. However, a list of 567 deprecated aliases the type is known by MAY be supplied as additional 568 information in order to assist applications in processing the media 569 type properly. 571 4.3. Parameter Requirements 573 Media types MAY elect to use one or more media type parameters, or 574 some parameters may be automatically made available to the media type 575 by virtue of being a subtype of a content type that defines a set of 576 parameters applicable to any of its subtypes. In either case, the 577 names, values, and meanings of any parameters MUST be fully specified 578 when a media type is registered in the standards tree, and SHOULD be 579 specified as completely as possible when media types are registered 580 in the vendor or personal trees. 582 Parameter names have the syntax as media type names and values: 584 parameter-name = restricted-name 586 Note that this syntax is somewhat more restrictive than what is 587 allowed by the ABNF in [RFC2045] and amended by [RFC2231]. 589 Parameter names are case-insensitive and no meaning is attached to 590 the order in which they appear. It is an error for a specific 591 parameter to be specified more than once. 593 There is no defined syntax for parameter values. Therefore 594 registrations MUST specify parameter value syntax. Additionally, 595 some transports impose restrictions on parameter value syntax, so 596 care needs be taken to limit the use of potentially problematic 597 syntaxes; e.g., pure binary valued parameters, while permitted in 598 some protocols, are best avoided. 600 Note that a protocol can impose further restrictions on parameter 601 value syntax, depending on how it chooses to represent parameters. 602 Both MIME [RFC2045] [RFC2231] and HTTP [RFC2045] [RFC5987] allow 603 binary parameters as well as parameter values expressed in a specific 604 charset, but other protocols may be less flexible. 606 New parameters SHOULD NOT be defined as a way to introduce new 607 functionality in types registered in the standards tree, although new 608 parameters MAY be added to convey additional information that does 609 not otherwise change existing functionality. An example of this 610 would be a "revision" parameter to indicate a revision level of an 611 external specification such as JPEG. Similar behavior is encouraged 612 for media types registered in the vendor or personal trees, but is 613 not required. 615 Changes to parameters (including the introduction of new ones) is 616 managed in the same manner as other changes to the media type; see 617 Section 5.5. 619 4.4. Canonicalization and Format Requirements 621 All registered media types MUST employ a single, canonical data 622 format, regardless of registration tree. 624 A permanent and readily available public specification of the format 625 for the media type MUST exist for all types registered in the 626 standards tree, and this specification MUST provide sufficient detail 627 so that interoperability between independent implementations using 628 the media type is possible. This specification MUST at a minimum be 629 referenced by, if it is not actually included in, the media type 630 registration proposal itself. 632 The specifications of format and processing particulars may or may 633 not be publicly available for media types registered in the vendor 634 and personal trees, and such registrations are explicitly permitted 635 to limit the information in the registration to which software and 636 version produce or process such media types. As such, references to 637 or inclusion of format specifications in registrations is encouraged 638 but not required. Note, however, that the public availability of a 639 meaningful specification will often make the difference between 640 simply having a name reserved so that there are no conflicts with 641 other uses and having the potential for other implementations of the 642 media type and useful interoperation with them. 644 Some media types involve the use of patented technology. The 645 registration of media types involving patented technology is 646 specifically permitted. However, the restrictions set forth in BCP 647 79 [RFC3979] and BCP 78 [RFC5378] on the use of patented technology 648 in IETF standards-track protocols must be respected when the 649 specification of a media type is part of a standards-track protocol. 650 In addition, other standards bodies making use of the standards tree 651 may have their own rules regarding intellectual property that must be 652 observed in their registrations. 654 IPR disclosures for registrations in the vendor and personal tree are 655 encouraged but not required. 657 4.5. Interchange Recommendations 659 Ideally media types will be defined so they interoperate across as 660 many systems and applications as possible. However, some media types 661 will inevitably have problems interoperating across different 662 platforms. Problems with different versions, byte ordering, and 663 specifics of gateway handling can and will arise. 665 Universal interoperability of media types is not required, but known 666 interoperability issues SHOULD be identified whenever possible. 667 Publication of a media type does not require an exhaustive review of 668 interoperability, and the interoperability considerations section is 669 subject to continuing evaluation. 671 These recommendations in this subsection apply regardless of the 672 registration tree involved. 674 4.6. Security Requirements 676 An analysis of security issues MUST be done for all types registered 677 in the standards tree. A similar analysis for media types registered 678 in the vendor or personal trees is encouraged but not required. 679 However, regardless of what security analysis has or has not been 680 done, all descriptions of security issues MUST be as accurate as 681 possible regardless of registration tree. In particular, the 682 security considerations MUST NOT state that there are "no security 683 issues associated with this type". Security considerations for types 684 in the vendor or personal tree MAY say that "the security issues 685 associates with this type have not been assessed". 687 There is absolutely no requirement that media types registered in any 688 tree be secure or completely free from risks. Nevertheless, all 689 known security risks MUST be identified in the registration of a 690 media type, again regardless of registration tree. 692 The security considerations section of all registrations is subject 693 to continuing evaluation and modification, and in particular MAY be 694 extended by use of the "comments on media types" mechanism described 695 in Section 5.4 below. 697 Some of the issues that need to be examined and described in a 698 security analysis of a media type are: 700 o Complex media types may include provisions for directives that 701 institute actions on a recipient's files or other resources. In 702 many cases provision is made for originators to specify arbitrary 703 actions in an unrestricted fashion that may then have devastating 704 effects. See the registration of the application/postscript media 705 type in [RFC2046] for an example of such directives and how they 706 can be described in a media type registration. 708 o Any security analysis MUST state whether or not they employ such 709 "active content", and if they do, they MUST state what steps have 710 been taken, or MUST be taken by applications of the media type, to 711 protect users of the media type from harm. 713 o Complex media types may include provisions for directives that 714 institute actions that, while not directly harmful to the 715 recipient, may result in disclosure of information that either 716 facilitates a subsequent attack or else violates a recipient's 717 privacy in some way. Again, the registration of the application/ 718 postscript media type illustrates how such directives can be 719 handled. 721 o A media type that employs compression may provide an opportunity 722 for sending a small amount of data that, when received and 723 evaluated, expands enormously to consume all of the recipient's 724 resources. All media types SHOULD state whether or not they 725 employ compression, and if they do they SHOULD discuss what steps 726 need to be taken to avoid such attacks. 728 o A media type might be targeted for applications that require some 729 sort of security assurance but not provide the necessary security 730 mechanisms themselves. For example, a media type could be defined 731 for storage of sensitive medical information that in turn requires 732 external confidentiality and integrity protection services, or 733 which is designed for use only within a secure environment. Types 734 SHOULD always document whether or not they need such services in 735 their security considerations. 737 4.7. Requirements specific to XML media types 739 There are a number of additional requirements specific to the 740 registration of XML media types. These requirements are specified in 741 [RFC3023]. 743 4.8. Encoding Requirements 745 Some transports impose restrictions on the type of data they can 746 carry. For example, Internet mail traditionally was limited to 7bit 747 US-ASCII text. Encoding schemes are often used to work around such 748 transport limitations. 750 It is therefore useful to note what sort of data a media type can 751 consist of as part of its registration. An "encoding considerations" 752 field is provided for this purpose. Possible values of this field 753 are: 755 7bit: The content of the media type consists solely of CRLF- 756 delimited 7bit US-ASCII text. 758 8bit: The content of the media type consists solely of CRLF- 759 delimited 8bit text. 761 binary: The content consists of an unrestricted sequence of octets. 763 framed: The content consists of a series of frames or packets 764 without internal framing or alignment indicators. Additional out- 765 of-band information is needed to interpret the data properly, 766 including but not necessarily limited to, knowledge of the 767 boundaries between successive frames and knowledge of the 768 transport mechanism. Note that media types of this sort cannot 769 simply be stored in a file or transported as a simple stream of 770 octets; therefore, such media types are unsuitable for use in many 771 traditional protocols. A commonly used transport with framed 772 encoding is the Real-time Transport Protocol, RTP. Additional 773 rules for framed encodings defined for transport using RTP are 774 given in [RFC4855]. 776 Additional restrictions on 7bit and 8bit text are given in Section 777 4.1.1 of [RFC2046]. 779 4.9. Usage and Implementation Non-requirements 781 In the asynchronous mail environment, where information on the 782 capabilities of the remote mail agent is frequently not available to 783 the sender, maximum interoperability is attained by restricting the 784 media types used to those "common" formats expected to be widely 785 implemented. This was asserted in the past as a reason to limit the 786 number of possible media types, and resulted in a registration 787 process with a significant hurdle and delay for those registering 788 media types. 790 However, the need for "common" media types does not require limiting 791 the registration of new media types. If a limited set of media types 792 is recommended for a particular application, that should be asserted 793 by a separate applicability statement specific for the application 794 and/or environment. 796 Therefore, universal support and implementation of a media type is 797 NOT a requirement for registration. However, if a media type is 798 explicitly intended for limited use, this MUST be noted in its 799 registration. The "Restrictions on Usage" field is provided for this 800 purpose. 802 4.10. Publication Requirements 804 Media types registered in the standards tree by the IETF itself MUST 805 be published as RFCs. RFC publication of vendor and personal media 806 type registrations is allowed but not required. In all cases the 807 IANA will retain copies of all media type registrations and "publish" 808 them as part of the media types registration tree itself. 810 As stated previously, standards tree registrations for media types 811 defined in documents produced by other standards bodies MUST be 812 described by a formal standards specification produced by that body. 813 Additionally, any copyright on the registration template MUST allow 814 the IANA to copy it into the IANA registry. 816 Other than IETF registrations in the standards tree, the registration 817 of a media type does not imply endorsement, approval, or 818 recommendation by the IANA or the IETF or even certification that the 819 specification is adequate. To become an Internet Standard, a 820 protocol or data object must go through the IETF standards process. 821 While it provides additional assurances when it is appropriate, this 822 is too difficult and too lengthy a process for the convenient 823 registration of media types. 825 The standards tree exists for media types that do require a 826 substantive review and approval process in a recognized standards 827 body. The vendor and personal trees exist for those media types that 828 do not require such a process. It is expected that applicability 829 statements for particular applications will be published from time to 830 time in the IETF, recommending implementation of, and support for, 831 media types that have proven particularly useful in those contexts. 833 As discussed above, registration of a top-level type requires 834 Standards Action in the IETF and, hence, the publication of a RFC on 835 the Standards Track. 837 4.11. Fragment Identifier Requirements 839 Media type registrations can specify how applications should 840 interpret fragment identifiers (specified in section 3.5 of 841 [RFC3986]) associated with the media type. 843 Media types are encouraged to adopt fragment identifier schemes that 844 are used with semantically similar media types. In particular, media 845 types that use a named structured syntax with a registered "+suffix" 846 MUST follow whatever fragment identifier rules are given in the 847 structured syntax suffix registration. 849 4.12. Additional Information 851 Various sorts of optional information SHOULD be included in the 852 specification of a media type if it is available: 854 o Magic number(s) (length, octet values). Magic numbers are byte 855 sequences that are always present at a given place in the file and 856 thus can be used to identify entities as being of a given media 857 type. 859 o File name extension(s) commonly used on one or more platforms to 860 indicate that some file contains a given media type. 862 o Mac OS File Type code(s) (4 octets) used to label files containing 863 a given media type. Some discussion of Macintosh file type codes 864 and their purpose can be found in [MacOSFileTypes]. 866 In the case of a registration in the standards tree, this additional 867 information MAY be provided in the formal specification of the media 868 type format. It is suggested that this be done by incorporating the 869 IANA media type registration form into the format specification 870 itself. 872 5. Media Type Registration Procedures 874 The media type registration procedure is not a formal standards 875 process, but rather an administrative procedure intended to allow 876 community comment and sanity checking without excessive time delay. 878 Normal IETF processes need to be followed for all IETF registrations 879 in the standards tree. The posting of an Internet Draft is a 880 necessary first step, followed by posting to the media-types@iana.org 881 list as discussed below. 883 5.1. Preliminary Community Review 885 Notice of a potential media type registration in the standards tree 886 SHOULD be sent to the media-types@iana.org mailing list for review. 887 This mailing list has been established for the purpose of reviewing 888 proposed media and access types. Registrations in other trees MAY be 889 sent to the list for review as well; doing so is entirely OPTIONAL, 890 but is strongly encouraged. 892 The intent of the public posting to this list is to solicit comments 893 and feedback on the choice of type/subtype name, the unambiguity of 894 the references with respect to versions and external profiling 895 information, and a review of any interoperability or security 896 considerations. The submitter may submit a revised registration 897 proposal or abandon the registration completely and at any time. 899 5.2. Submit request to IANA 901 Media types registered in the standards tree by the IETF itself MUST 902 be reviewed and approved by the IESG as part of the normal standards 903 process. Standards tree registrations by recognized standards bodies 904 as well as registrations in the vendor and personal tree are 905 submitted directly to the IANA, unless other arrangements were made 906 as part of a liaison agreement. In either case posting the 907 registration to the media-types@iana.org list for review prior to 908 submission is strongly encouraged. 910 Registration requests can be sent to iana@iana.org. A web form for 911 registration requests is also available: 913 http://www.iana.org/cgi-bin/mediatypes.pl 915 5.2.1. Provisional Registrations 917 Standardization processes often take considerable time to complete. 918 In order to facilitate prototyping and testing it is often helpful to 919 assign identifiers, including but not limited to media types, early 920 in the process. This way identifiers used during standards 921 development can remain unchanged once the process is complete and 922 implementations and documentation do not have to be updated. 924 Accordingly, a provisional registration process is provided to 925 support early assignment of media type names in the standards tree. 926 A provisional registration MAY be submitted to IANA for standards 927 tree types. The only required fields in such registrations are the 928 media type name and contact information (including the standards body 929 name). 931 Upon receipt of a provisional registration, IANA will check the name 932 and contact information, then publish the registration in a separate 933 publicly visible provisional registration list. 935 Provisional registrations MAY be updated or abandoned at any time. 936 When the registration is abandoned the media type is no longer 937 registered in any sense; it can subsequently be registered just like 938 any other unassigned media type name. 940 5.3. Review and Approval 942 With the exception of provisional standards tree registrations, 943 registrations submitted to the IANA will be passed on to the media 944 types reviewer. The media types reviewer, who is appointed by the 945 IETF Applications Area Director(s), will review the registration to 946 make sure it meets the requirements set forth in this document. 947 Registrations that do not meet these requirements will be returned to 948 the submitter for revision. 950 Decisions made by the media types reviewer may be appealed to the 951 IESG using the procedure specified in section 6.5.4 of [RFC2026]. 953 Once a media type registration has passed review, the IANA will 954 register the media type and make the media type registration 955 available to the community. 957 In the case of standards tree registrations from other standards 958 bodies IANA will also check that the submitter is in fact a 959 recognized standards body. If the submitter is not currently 960 recognized as such the IESG will be asked to confirm their status. 962 Recognition from the IESG MUST be obtained before a standards tree 963 registration can proceed. 965 5.4. Comments on Media Type Registrations 967 Comments on registered media types may be submitted by members of the 968 community to the IANA at iana@iana.org. These comments will be 969 reviewed by the media types reviewer and then passed on to the 970 "owner" of the media type if possible. Submitters of comments may 971 request that their comment be attached to the media type registration 972 itself, and if the IANA, in consultation with the media types 973 reviewer, approves, the comment will be made accessible in 974 conjunction with the type registration. 976 5.5. Change Procedures 978 Once a media type has been published by the IANA, the owner may 979 request a change to its definition. The descriptions of the 980 different registration trees above designate the "owners" of each 981 type of registration. The same procedure that would be appropriate 982 for the original registration request is used to process a change 983 request. 985 Media type registrations may not be deleted; media types that are no 986 longer believed appropriate for use can be declared OBSOLETE by a 987 change to their "intended use" field; such media types will be 988 clearly marked in the lists published by the IANA. 990 Significant changes to a media type's definition should be requested 991 only when there are serious omissions or errors in the published 992 specification. When review is required, a change request may be 993 denied if it renders entities that were valid under the previous 994 definition invalid under the new definition. 996 The owner of a media type may pass responsibility to another person 997 or agency by informing the IANA; this can be done without discussion 998 or review. 1000 The IESG may reassign responsibility for a media type. The most 1001 common case of this will be to enable changes to be made to types 1002 where the author of the registration has died, moved out of contact 1003 or is otherwise unable to make changes that are important to the 1004 community. 1006 5.6. Registration Template 1008 Type name: 1010 Subtype name: 1012 Required parameters: 1014 Optional parameters: 1016 Encoding considerations: 1018 Security considerations: 1020 Interoperability considerations: 1022 Published specification: 1024 Applications that use this media type: 1026 Fragment identifier considerations: 1028 Additional information: 1030 Deprecated alias names for this type: 1031 Magic number(s): 1032 File extension(s): 1033 Macintosh file type code(s): 1035 Person & email address to contact for further information: 1037 Intended usage: 1039 (One of COMMON, LIMITED USE or OBSOLETE.) 1041 Restrictions on usage: 1043 (Any restrictions on where the media type can be used go here.) 1045 Author: 1047 Change controller: 1049 Provisional registration? (standards tree only): 1051 (Any other information that the author deems interesting may be 1052 added below this line.) 1053 "N/A", written exactly that way, can be used in any field if desired 1054 to emphasize the fact that it does not apply or that the question was 1055 not omitted by accident. Do not use 'none' or other words that could 1056 be mistaken for a response. 1058 Limited use media types should also note in the applications list 1059 whether or not that list is exhaustive. 1061 6. Structured Syntax Suffix Registration Procedures 1063 Someone wishing to define a "+suffix" name for a structured syntax 1064 for use with a new media type registration SHOULD: 1066 1. Check IANA's registry of media type name suffixes to see whether 1067 or not there is already an entry for that well-defined structured 1068 syntax. 1070 2. If there is no entry for their suffix scheme, fill out the 1071 template (specified in Section 6.2) and include that with the 1072 media type registration. The template may be contained in an 1073 Internet Draft, alone or as part of some other protocol 1074 specification. The template may also be submitted in some other 1075 form (as part of another document or as a stand-alone document), 1076 but the contents will be treated as an "IETF Contribution" under 1077 the guidelines of BCP 78 [RFC5378]. 1079 3. Send a copy of the template or a pointer to the containing 1080 document (with specific reference to the section with the 1081 template) to the mailing list media-types@iana.org, requesting 1082 review. This may be combined with a request to review the media 1083 type registration. Allow a reasonable time for discussion and 1084 comments. 1086 4. Respond to review comments and make revisions to the proposed 1087 registration as needed to bring it into line with the guidelines 1088 given in this document. 1090 5. Submit the (possibly updated) registration template (or pointer 1091 to the document containing it) to IANA at iana@iana.org. 1093 Upon receipt of a structured syntax suffix registration request, 1095 1. IANA checks the submission for completeness; if sections are 1096 missing or citations are not correct, IANA rejects the 1097 registration request. 1099 2. IANA checks the current registry for an entry with the same name; 1100 if such a registry exists, IANA rejects the registration request. 1102 3. IANA requests Expert Review of the registration request against 1103 the corresponding guidelines. 1105 4. The Designated Expert may request additional review or 1106 discussion, as necessary. 1108 5. If Expert Review recommends registration, IANA adds the 1109 registration to the appropriate registry. 1111 The initial registry content specification 1112 [I-D.appsawg-media-type-suffix-regs] provides examples of structured 1113 syntax suffix registrations. 1115 6.1. Change Procedures 1117 Registrations may be updated in each registry by the same mechanism 1118 as required for an initial registration. In cases where the original 1119 definition of the scheme is contained in an IESG-approved document, 1120 update of the specification also requires IESG approval. 1122 6.2. Structured Syntax Suffix Registration Template 1124 This template describes the fields that must be supplied in a 1125 structured syntax suffix registration request: 1127 Name 1128 Full name of the well-defined structured syntax. 1130 +suffix 1131 Suffix used to indicate conformance to the syntax. 1133 References 1134 Include full citations for all specifications necessary to 1135 understand the structured syntax. 1137 Encoding considerations 1138 General guidance regarding encoding considerations for any type 1139 employing this syntax should be given here. The same requirements 1140 for media type encoding considerations given in Section 4.8 apply 1141 here. 1143 Interoperability considerations 1144 Any issues regarding the interoperable use of types employing this 1145 structured syntax should be given here. Examples would include 1146 the existence of incompatible versions of the syntax, issues 1147 combining certain charsets with the syntax, or incompatibilities 1148 with other types or protocols. 1150 Fragment identifier considerations 1151 Generic processing of fragment identifiers for any type employing 1152 this syntax should be described here. 1154 Security considerations 1155 Security considerations shared by media types employing this 1156 structured syntax must be specified here. The same requirements 1157 for media type security considerations given in Section 4.6 apply 1158 here, with the exception that the option of not assessing the 1159 security considerations is not available for suffix registrations. 1161 Contact 1162 Person (including contact information) to contact for further 1163 information. 1165 Author/Change controller. 1166 Person (including contact information) authorized to change this 1167 suffix registration. 1169 7. Security Considerations 1171 Security requirements for both media type and media type suffix 1172 registrations are discussed in Section 4.6. 1174 8. IANA Considerations 1176 The purpose of this document is to define IANA registries for media 1177 types and structured syntax suffixes as well as the procedures for 1178 managing these registries. Additionally, this document requires IANA 1179 to maintain a list of IESG-recognized standards bodies who are 1180 allowed to register types in the standards tree. 1182 The existing media type registry has been extended to include a 1183 section for provisional registrations. Only standards tree 1184 registrations are allowed in the standards tree and only at the 1185 request of a standards body on the IESG-recognized standards body 1186 list. See Section 5.2.1 for additional information on provisional 1187 registrations. 1189 IANA is also requested to add the following note at the top of the 1190 provisional registry: 1192 This registry, unlike some other provisional IANA registries, is 1193 only for temporary use. Entries in this registry are either 1194 finalized and moved to the main media types registry, or are 1195 abandoned and deleted. Entries in this registry are suitable for 1196 use for use for development and test purposes only. 1198 The structured syntax name suffix registry is to be created as 1199 follows: 1201 o The name is the "Structured Syntax Suffix" registry. 1203 o The registration process is specified in Section 6. 1205 o The information required for a registry entry as well as the entry 1206 format are specified in Section 6.2. 1208 o The initial content of the registry is specified in 1209 [I-D.appsawg-media-type-suffix-regs]. 1211 Entries in both the media type and structured suffix registries will 1212 be annotated by IANA with both the original registration date as well 1213 as the date of the most recent update to the entry. Registrations 1214 made prior to the implementations of this specification can be marked 1215 as "registered under RFC 4288 or earlier". 1217 Since registration entries can be updated multiple times, IANA is 1218 also requested to maintain the history of changes to each 1219 registration in such a way that the state of the registration at any 1220 given time can be determined 1222 Finally, this document calls for the creation of a new email address, 1223 media-types@iana.org, for the media type review list, which replaces 1224 the ietf-types@iana.org address specified in RFC 4288. 1225 ietf-types@iana.org should be retained as an alias. 1227 9. Acknowledgments 1229 The current authors would like to acknowledge their debt to the late 1230 Dr. Jon Postel, whose general model of IANA registration procedures 1231 and specific contributions shaped the predecessors of this document 1232 [RFC2048] [RFC4288]. We hope that the current version is one with 1233 which he would have agreed but, as it is impossible to verify that 1234 agreement, we have regretfully removed his name as a co-author. 1236 Randy Bush, Francis Dupont, Bjoern Hoehrmann, Barry Leiba, Murray 1237 Kucherawy, Alexey Melnikov, S. Moonesamy, Mark Nottingham, Tom Petch, 1238 Peter Saint-Andre, and Jeni Tennison provided many helpful review 1239 comments and suggestions. 1241 10. References 1243 10.1. Normative References 1245 [I-D.appsawg-media-type-suffix-regs] 1246 Hansen, T., "Additional Media Type Structured Syntax 1247 Suffixes", draft-appsawg-media-type-suffix-regs-00 (work 1248 in progress), April 2012. 1250 [I-D.ietf-appsawg-mime-default-charset] 1251 Melnikov, A. and J. Reschke, "Update to MIME regarding 1252 Charset Parameter Handling in Textual Media Types", 1253 draft-ietf-appsawg-mime-default-charset-01 (work in 1254 progress), March 2012. 1256 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1257 Extensions (MIME) Part One: Format of Internet Message 1258 Bodies", RFC 2045, November 1996. 1260 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1261 Extensions (MIME) Part Two: Media Types", RFC 2046, 1262 November 1996. 1264 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1265 Requirement Levels", BCP 14, RFC 2119, March 1997. 1267 [RFC2978] Freed, N. and J. Postel, "IANA Charset Registration 1268 Procedures", BCP 19, RFC 2978, October 2000. 1270 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 1271 Types", RFC 3023, January 2001. 1273 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 1274 10646", STD 63, RFC 3629, November 2003. 1276 [RFC3979] Bradner, S., "Intellectual Property Rights in IETF 1277 Technology", BCP 79, RFC 3979, March 2005. 1279 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1280 Resource Identifier (URI): Generic Syntax", STD 66, 1281 RFC 3986, January 2005. 1283 [RFC4855] Casner, S., "Media Type Registration of RTP Payload 1284 Formats", RFC 4855, February 2007. 1286 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1287 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1288 May 2008. 1290 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 1291 Specifications: ABNF", STD 68, RFC 5234, January 2008. 1293 [RFC5378] Bradner, S. and J. Contreras, "Rights Contributors Provide 1294 to the IETF Trust", BCP 78, RFC 5378, November 2008. 1296 [RFC6532] Yang, A., Steel, S., and N. Freed, "Internationalized 1297 Email Headers", RFC 6532, January 2012. 1299 10.2. Informative References 1301 [I-D.ietf-appsawg-xdash] 1302 Saint-Andre, P. and D. Crocker, "Deprecating the X- Prefix 1303 and Similar Constructs in Application Protocols", 1304 draft-ietf-appsawg-xdash-05 (work in progress), 1305 April 2012. 1307 [MacOSFileTypes] 1308 Apple Computer, Inc., "Mac OS: File Type and Creator 1309 Codes, and File Formats", Apple Knowledge Base Article 1310 55381, June 1993, 1311 . 1313 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 1314 3", BCP 9, RFC 2026, October 1996. 1316 [RFC2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose 1317 Internet Mail Extensions (MIME) Part Four: Registration 1318 Procedures", BCP 13, RFC 2048, November 1996. 1320 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 1321 Word Extensions: 1322 Character Sets, Languages, and Continuations", RFC 2231, 1323 November 1997. 1325 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 1326 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 1327 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 1329 [RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and 1330 Registration Procedures", BCP 13, RFC 4288, December 2005. 1332 [RFC5987] Reschke, J., "Character Set and Language Encoding for 1333 Hypertext Transfer Protocol (HTTP) Header Field 1334 Parameters", RFC 5987, August 2010. 1336 Appendix A. Grandfathered Media Types 1338 A number of media types with unfaceted subtype names, registered 1339 prior to 1996, would, if registered under the guidelines in this 1340 document, be given a faceted name and placed into either the vendor 1341 or personal trees. Reregistration of those types to reflect the 1342 appropriate trees is encouraged but not required. Ownership and 1343 change control principles outlined in this document apply to those 1344 types as if they had been registered in the trees described above. 1346 From time to time there may also be cases where a media type with an 1347 unfaceted subtype name has been widely deployed without being 1348 registered. (Note that this includes subtype names beginning with 1349 the "x-" prefix.) If possible such media type SHOULD be reregistered 1350 with a proper faceted subtype name. However, if this is not possible 1351 the type can, subject to approval by both the media types reviewer 1352 and the IESG, be registered in the proper tree with its unfaceted 1353 name. 1355 Appendix B. Changes Since RFC 4288 1357 o Suffixes to indicate the use of a particular structured syntax are 1358 now fully specified and a suffix registration process has been 1359 defined. 1361 o Registration of widely deployed unregistered unfaceted type names 1362 in the vendor or personal trees is now allowed, subject to 1363 approval by the media types reviewer and the IESG. 1365 o The standards tree registration process has been revised to 1366 include Expert Review and generalized to address cases like media 1367 types in non-IETF stream documents. 1369 o A field for fragment identifiers has been added to the 1370 registration template and brief directions for specifying fragment 1371 identifiers have been added. 1373 o The specification requirements for personal tree registrations 1374 have been changed to be the same as those for the vendor tree. 1375 The text has been changed to encourage (but not require) 1376 specification availability. 1378 o The definition of additional trees has been clarified to state 1379 that an IETF Standards Action is required. 1381 o Widely deployed types with "x-" names can now be registered as an 1382 exception in the vendor tree. 1384 o The requirements on changes to registrations have been loosened so 1385 minor changes are easier to make. 1387 o The registration process has been completely restructured so that 1388 with the exception of IETF-generated types in the standards tree, 1389 all requests are processed by IANA and not the IESG. 1391 o A provisional registration process has been added for early 1392 assignment of types in the standards tree. 1394 o Many editorial changes have been made throughout the document to 1395 make the requirements and processes it describes clearer and 1396 easier to follow. 1398 o The ability to specify a list of deprecated aliases for a media 1399 type has been added. 1401 o Types with names beginning with "x-" are no longer considered to 1402 be members of the unregistered "x." tree. As with any unfaceted 1403 type, special procedures have been added to allow registration of 1404 such types in an appropriate tree. 1406 o Changes to a type registered by a third party may now be made by 1407 the designated change controller even if that isn't the vendor or 1408 organization that created the type. However, the vendor or 1409 organization may elect to assert ownership and change controller 1410 over the type at any time. 1412 o Limited use media types are now asked to note whether or not the 1413 supplied list of applications employing the media type is 1414 exhaustive. 1416 o The ABNF for media type names has been further restricted to 1417 require that names begin with an alphanumeric character. 1419 o Mailing list review is no longer required prior to registration of 1420 media types. Additionally, the address associated with the media 1421 type review mailing list has been changed to media-types@iana.org. 1423 o The rules for text/* media types have been updated to reflect the 1424 changes specified in [I-D.ietf-appsawg-mime-default-charset]. 1426 Authors' Addresses 1428 Ned Freed 1429 Oracle 1430 800 Royal Oaks 1431 Monrovia, CA 91016-6347 1432 USA 1434 Email: ned+ietf@mrochek.com 1436 John C. Klensin 1437 1770 Massachusetts Ave, #322 1438 Cambridge, MA 02140 1439 USA 1441 Email: john+ietf@jck.com 1443 Tony Hansen 1444 AT&T Laboratories 1445 200 Laurel Ave. 1446 Middletown, NJ 07748 1447 USA 1449 Email: tony+mtsuffix@maillennium.att.com