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'I-D.appsawg-media-type-suffix-regs' == Outdated reference: draft-ietf-appsawg-mime-default-charset has been published as RFC 6657 ** Obsolete normative reference: RFC 3023 (Obsoleted by RFC 7303) ** Obsolete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reference: RFC 3979 (Obsoleted by RFC 8179) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) == Outdated reference: draft-ietf-appsawg-xdash has been published as RFC 6648 -- Obsolete informational reference (is this intentional?): RFC 2048 (Obsoleted by RFC 4288,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) Summary: 3 errors (**), 0 flaws (~~), 4 warnings (==), 8 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: November 19, 2012 T. Hansen 7 AT&T Laboratories 8 May 18, 2012 10 Media Type Specifications and Registration Procedures 11 draft-ietf-appsawg-media-type-regs-09 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 November 19, 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 . . . . . . . . . . . . . . . . . . 15 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 . . . . . . . . . . . . . . 20 89 5.3. Review and Approval . . . . . . . . . . . . . . . . . . . 21 90 5.4. Comments on Media Type Registrations . . . . . . . . . . . 21 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. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27 100 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27 101 10.1. Normative References . . . . . . . . . . . . . . . . . . . 27 102 10.2. Informative References . . . . . . . . . . . . . . . . . . 28 103 Appendix A. Grandfathered Media Types . . . . . . . . . . . . . . 29 104 Appendix B. Changes Since RFC 4288 . . . . . . . . . . . . . . . 29 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 107 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 has now been moved to this separate 147 document, to make it 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 revision incorporates such restrictions into media type registrations 152 in a systematic way. See Section 4.9 for additional discussion. 154 1.2. Conventions Used in This Document 156 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 157 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 158 document are to be interpreted as described in [RFC2119] when they 159 appear in ALL CAPS. They may also appear in lower or mixed case as 160 plain English words, without any normative meaning. 162 This specification makes use of the Augmented Backus-Naur Form (ABNF) 163 [RFC5234] notation, including the core rules defined in Appendix A of 164 that document. 166 2. Media Type Registration Preliminaries 168 Registration of a new media type or types starts with the 169 construction of a registration proposal. Registration may occur 170 within several different registration trees that have different 171 requirements, as discussed below. In general, a new registration 172 proposal is circulated and reviewed in a fashion appropriate to the 173 tree involved. The media type is then registered if the proposal is 174 acceptable. The following sections describe the requirements and 175 procedures used for each of the different registration trees. 177 3. Registration Trees and Subtype Names 179 In order to increase the efficiency and flexibility of the 180 registration process, different structures of subtype names can be 181 registered to accommodate the different natural requirements for, 182 e.g., a subtype that will be recommended for wide support and 183 implementation by the Internet community, or a subtype that is used 184 to move files associated with proprietary software. The following 185 subsections define registration "trees" that are distinguished by the 186 use of faceted names, e.g., names of the form 187 "tree.subtree...subtype". Note that some media types defined prior 188 to this document do not conform to the naming conventions described 189 below. See Appendix A for a discussion of them. 191 3.1. Standards Tree 193 The standards tree is intended for types of general interest to the 194 Internet community. Registrations in the standards tree MUST be 195 either: 197 1. in the case of registrations in IETF specifications, approved 198 directly by the IESG, or 200 2. registered by a recognized standards body using the 201 "Specification Required" IANA registration policy [RFC5226] 202 (which implies Expert Review). 204 The first procedure is used for registering registrations from IETF 205 Consensus documents, or in rare cases when registering a 206 grandfathered (see Appendix A) and/or otherwise incomplete 207 registration is in the interest of the Internet community. The 208 registration proposal MUST be published as an RFC. When the RFC is 209 in the IETF stream it is an IETF Consensus RFC, which can be on the 210 Standards Track, a BCP, Informational, or Experimental. 211 Registrations published in non-IETF RFC streams are also allowed, and 212 require IESG approval. A registration can be either in a standalone 213 "registration only" RFC or incorporated into a more general 214 specification of some sort. 216 In the second case the IESG makes a one time decision on whether the 217 registration submitter represents a recognized standards body; after 218 that, a Media Types Reviewer (Designated Expert or a group of 219 Designated Experts) performs the Expert Review as specified in this 220 document. Subsequent submissions from the same source do not involve 221 the IESG. The format MUST be described by a formal standards 222 specification produced by the submitting standards body. 224 Media types in the standards tree MUST NOT have faceted names, unless 225 they are grandfathered in using the process described in Appendix A. 227 The "owner" of a media type registered in the standards tree is 228 assumed to be the standards body itself. Modification or alteration 229 of the specification uses the same level of processing (e.g., a 230 registration submitted on Standards Track can be revised in another 231 Standards Track RFC, but cannot be revised in an Informational RFC) 232 required for the initial registration. 234 Standards-tree registrations from recognized standards bodies may be 235 submitted directly to the IANA, where they will undergo Expert Review 236 [RFC5226] prior to approval. In this case, the Expert Reviewer(s) 237 will, among other things, ensure that the required specification 238 provides adequate documentation. 240 3.2. Vendor Tree 242 The vendor tree is used for media types associated with publicly 243 available products. "Vendor" and "producer" are construed very 244 broadly in this context and are considered equivalent. Note that 245 industry consortia as well as non-commercial entities that do not 246 qualify as recognized standards bodies can quite appropriately 247 register media types in the vendor tree. 249 A registration may be placed in the vendor tree by anyone who needs 250 to interchange files associated with some product or set of products. 251 However, the registration properly belongs to the vendor or 252 organization producing the software that employs the type being 253 registered, and that vendor or organization can at any time elect to 254 assert ownership of a registration done by a third party in order to 255 correct or update it. See Section 5.5 for additional information. 257 When a third party registers a type on behalf of someone else both 258 entities SHOULD be noted in the Change Controller field in the 259 registration. One possible format for this would be "Foo, on behalf 260 of Bar". 262 Registrations in the vendor tree will be distinguished by the leading 263 facet "vnd.". That may be followed, at the discretion of the 264 registrant, by either a media subtype name from a well-known producer 265 (e.g., "vnd.mudpie") or by an IANA-approved designation of the 266 producer's name that is followed by a media type or product 267 designation (e.g., vnd.bigcompany.funnypictures). 269 While public exposure and review of media types to be registered in 270 the vendor tree is not required, using the media-types@iana.org 271 mailing list for review is encouraged to improve the quality of those 272 specifications. Registrations in the vendor tree may be submitted 273 directly to the IANA, where they will undergo Expert Review [RFC5226] 274 prior to approval. 276 3.3. Personal or Vanity Tree 278 Registrations for media types created experimentally or as part of 279 products that are not distributed commercially may be registered in 280 the personal or vanity tree. The registrations are distinguished by 281 the leading facet "prs.". 283 The owner of "personal" registrations and associated specifications 284 is the person or entity making the registration, or one to whom 285 responsibility has been transferred as described below. 287 While public exposure and review of media types to be registered in 288 the personal tree is not required, using the media-types@iana.org 289 mailing list (see Section 5.1) for review is encouraged to improve 290 the quality of those specifications. Registrations in the personal 291 tree may be submitted directly to the IANA, where they will undergo 292 Expert Review [RFC5226] prior to approval. 294 3.4. Unregistered x. Tree 296 Subtype names with "x." as the first facet may be used for types 297 intended exclusively for use in private, local environments. Types 298 in this tree cannot be registered and are intended for use only with 299 the active agreement of the parties exchanging them. 301 However, with the simplified registration procedures described above 302 for vendor and personal trees, it should rarely, if ever, be 303 necessary to use unregistered types. Therefore, use of types in the 304 "x." tree is strongly discouraged. 306 Note that types with names beginning with "x-" are no longer 307 considered to members of this tree (see [I-D.ietf-appsawg-xdash]). 308 Also note that if a generally useful and widely deployed type 309 incorrectly ends up with an "x-" name prefix, it MAY be registered 310 using its current name in an alternate tree by following the 311 procedure defined in Appendix A. 313 3.5. Additional Registration Trees 315 From time to time and as required by the community, new top-level 316 registration trees may be created by IETF Standards Action. It is 317 explicitly assumed that these trees may be created for external 318 registration and management by well-known permanent bodies; for 319 example, scientific societies may register media types specific to 320 the sciences they cover. In general, the quality of review of 321 specifications for one of these additional registration trees is 322 expected to be equivalent to registrations in the standards tree by a 323 recognized Standards Development Organization. When the IETF 324 performs such review, it needs to consider the greater expertise of 325 the requesting body with respect to the subject media type. 327 4. Registration Requirements 329 Media type registrations are all expected to conform to various 330 requirements laid out in the following sections. Note that 331 requirement specifics sometimes vary depending on the registration 332 tree, again as detailed in the following sections. 334 4.1. Functionality Requirement 336 Media types MUST function as actual media formats. Registration of 337 things that are better thought of as a transfer encoding, as a 338 charset, or as a collection of separate entities of another type, is 339 not allowed. For example, although applications exist to decode the 340 base64 transfer encoding [RFC2045], base64 cannot be registered as a 341 media type. 343 This requirement applies regardless of the registration tree 344 involved. 346 4.2. Naming Requirements 348 All registered media types MUST be assigned top-level type and 349 subtype names. The combination of these names serves to uniquely 350 identify the media type, and the subtype name facet (or the absence 351 of one) identifies the registration tree. Both top-level type and 352 subtype names are case-insensitive. 354 Type and subtype names MUST conform to the following ABNF: 356 type-name = restricted-name 357 subtype-name = restricted-name 359 restricted-name = restricted-name-first *126restricted-name-chars 360 restricted-name-first = ALPHA / DIGIT 361 restricted-name-chars = ALPHA / DIGIT / "!" / "#" / 362 "$" / "&" / "-" / "^" / "_" 363 restricted-name-chars =/ "." ; Characters before first dot always 364 ; specify a facet name 365 restricted-name-chars =/ "+" ; Characters after last plus always 366 ; specify a structured syntax suffix 368 Note that this syntax is somewhat more restrictive than what is 369 allowed by the ABNF in section 5.1 of [RFC2045] or section 4.2 of 370 [RFC4288]. Also note that while this syntax allows names of up to 371 127 characters, implementation limits may make such long names 372 problematic. For this reason the components of names SHOULD be 373 limited to 64 characters. 375 Although the name syntax treats "." as equivalent to any other 376 character, characters before any initial "." always specify the 377 registration facet. Note that this means that facet-less standards 378 tree registrations cannot use periods in the subtype name. 380 Similarly, "+" is used in subtype names to introduce a structured 381 syntax specifier suffix. Structured syntax suffix requirements are 382 specified in Section 4.2.8. 384 While it is possible for a given media type to be assigned additional 385 names, the use of different names to identify the same media type is 386 discouraged. 388 These requirements apply regardless of the registration tree 389 involved. 391 The choice of top-level type MUST take into account the nature of 392 media type involved. New subtypes of top-level types MUST conform to 393 the restrictions of the top-level type, if any. The following 394 sections describe each of the initial set of top-level types and 395 their associated restrictions. Additionally, various protocols, 396 including but not limited to HTTP and MIME, MAY impose additional 397 restrictions on the media types they can transport. (See [RFC2046] 398 for additional information on the restrictions MIME imposes.) 400 4.2.1. Text Media Types 402 The "text" top-level type is intended for sending material that is 403 principally textual in form. 405 Many subtypes of text, notably including the subtype "text/plain", 406 which is a generic subtype for plain text defined in [RFC2046], 407 define a "charset" parameter. If a "charset" parameter is defined 408 for a particular subtype of text, it MUST be used to specify a 409 charset name defined in accordance to the procedures laid out in 410 [RFC2978]. 412 As specified in [I-D.ietf-appsawg-mime-default-charset], a "charset" 413 parameter SHOULD NOT be specified when charset information is 414 transported inside the payload (e.g., as in "text/xml"). 416 If a "charset" parameter is specified, it SHOULD be a required 417 parameter, eliminating the options of specifying a default value. If 418 there is a strong reason for the parameter to be optional despite 419 this advice, each subtype MAY specify its own default value, or 420 alternately, it MAY specify that there is no default value. Finally, 421 the "UTF-8" charset [RFC3629] SHOULD be selected as the default. See 422 [I-D.ietf-appsawg-mime-default-charset] for additional information on 423 the use of "charset" parameters in conjunction with subtypes of text. 425 Regardless of what approach is chosen, all text/* registrations MUST 426 clearly specify how the charset is determined; relying on the US- 427 ASCII default defined in Section 4.1.2 of [RFC2046] is no longer 428 permitted. If explanatory text is needed this SHOULD be placed in 429 the additional information section of the registration. 431 Plain text does not provide for or allow formatting commands, font 432 attribute specifications, processing instructions, interpretation 433 directives, or content markup. Plain text is seen simply as a linear 434 sequence of characters, possibly interrupted by line breaks or page 435 breaks. Plain text MAY allow the stacking of several characters in 436 the same position in the text. Plain text in scripts like Arabic and 437 Hebrew may also include facilities that allow the arbitrary mixing of 438 text segments with different writing directions. 440 Beyond plain text, there are many formats for representing what might 441 be known as "rich text". An interesting characteristic of many such 442 representations is that they are to some extent readable even without 443 the software that interprets them. It is useful to distinguish them, 444 at the highest level, from such unreadable data as images, audio, or 445 text represented in an unreadable form. In the absence of 446 appropriate interpretation software, it is reasonable to present 447 subtypes of "text" to the user, while it is not reasonable to do so 448 with most non-textual data. Such formatted textual data can be 449 represented using subtypes of "text". 451 4.2.2. Image Media Types 453 A top-level type of "image" indicates that the content specifies one 454 or more individual images. The subtype names the specific image 455 format. 457 4.2.3. Audio Media Types 459 A top-level type of "audio" indicates that the content contains audio 460 data. The subtype names the specific audio format. 462 4.2.4. Video Media Types 464 A top-level type of "video" indicates that the content specifies a 465 time-varying-picture image, possibly with color and coordinated 466 sound. The term 'video' is used in its most generic sense, rather 467 than with reference to any particular technology or format, and is 468 not meant to preclude subtypes such as animated drawings encoded 469 compactly. 471 Note that although in general the mixing of multiple kinds media in a 472 single body is discouraged [RFC2046], it is recognized that many 473 video formats include a representation for synchronized audio and/or 474 text, and this is explicitly permitted for subtypes of "video". 476 4.2.5. Application Media Types 478 The "application" top-level type is to be used for discrete data that 479 do not fit under any of the other type names, and particularly for 480 data to be processed by some type of application program. This is 481 information that must be processed by an application before it is 482 viewable or usable by a user. Expected uses for the "application" 483 type name include but are not limited to file transfer, spreadsheets, 484 presentations, scheduling data, and languages for "active" 485 (computational) material. (The last, in particular, can pose 486 security problems that must be understood by implementors The 487 "application/postscript" media type registration in [RFC2046] 488 provides a good example of how to handle these issues.) 490 For example, a meeting scheduler might define a standard 491 representation for information about proposed meeting dates. An 492 intelligent user agent would use this information to conduct a dialog 493 with the user, and might then send additional material based on that 494 dialog. More generally, there have been several "active" languages 495 developed in which programs in a suitably specialized language are 496 transported to a remote location and automatically run in the 497 recipient's environment. Such applications may be defined as 498 subtypes of the "application" top-level type. 500 The subtype of "application" will often either be the name or include 501 part of the name of the application for which the data are intended. 502 This does not mean, however, that any application program name may 503 simply be used freely as a subtype of "application"; the subtype 504 needs to be registered. 506 4.2.6. Multipart and Message Media Types 508 Multipart and message are composite types, that is, they provide a 509 means of encapsulating zero or more objects, each one a separate 510 media type. 512 All subtypes of multipart and message MUST conform to the syntax 513 rules and other requirements specified in [RFC2046] and amended by 514 Section 3.5 of [RFC6532]. 516 4.2.7. Additional Top-level Types 518 In some cases a new media type may not "fit" under any currently 519 defined top-level type names. Such cases are expected to be quite 520 rare. However, if such a case does arise a new type name can be 521 defined to accommodate it. Such a definition MUST be done via 522 standards-track RFC; no other mechanism can be used to define 523 additional type name. 525 4.2.8. Structured Syntax Name Suffixes 527 XML in MIME [RFC3023] defined the first such augmentation to the 528 media type definition to additionally specify the underlying 529 structure of that media type. To quote: 531 This document also standardizes a convention (using the suffix 532 '+xml') for naming media types ... when those media types 533 represent XML MIME (Multipurpose Internet Mail Extensions) 534 entities. 536 That is, it specified a suffix (in that case, "+xml") to be appended 537 to the base subtype name. 539 Since this was published, the de facto practice has arisen for using 540 this suffix convention for other well-known structuring syntaxes. In 541 particular, media types have been registered with suffixes such as 542 "+der", "+fastinfoset" and "+json". This specification formalizes 543 this practice and sets up a registry for structured type name 544 suffixes. 546 The primary guideline for whether a structured type name suffix is 547 registrable is that it be described by a readily-available 548 description, preferably within a document published by an established 549 standards organization, and for which there's a reference that can be 550 used in a Normative References section of an RFC. 552 Media types that make use of a named structured syntax SHOULD use the 553 appropriate registered "+suffix" for that structured syntax when they 554 are registered. By the same token, media types MUST NOT be given 555 names incorporating suffixes for structured syntaxes they do not 556 actually employ. "+suffix" constructs for as-yet unregistered 557 structured syntaxes SHOULD NOT be used, given the possibility of 558 conflicts with future suffix definitions. 560 4.2.9. Deprecated Aliases 562 In some cases a single media type may have been widely deployed prior 563 to registration under multiple names. In such cases a preferred name 564 MUST be chosen for the media type and applications MUST use this to 565 be compliant with the type's registration. However, a list of 566 deprecated aliases the type is known by MAY be supplied as additional 567 information in order to assist applications in processing the media 568 type properly. 570 4.3. Parameter Requirements 572 Media types MAY elect to use one or more media type parameters, or 573 some parameters may be automatically made available to the media type 574 by virtue of being a subtype of a content type that defines a set of 575 parameters applicable to any of its subtypes. In either case, the 576 names, values, and meanings of any parameters MUST be fully specified 577 when a media type is registered in the standards tree, and SHOULD be 578 specified as completely as possible when media types are registered 579 in the vendor or personal trees. 581 Parameter names have the syntax as media type names and values: 583 parameter-name = restricted-name 585 Note that this syntax is somewhat more restrictive than what is 586 allowed by the ABNF in [RFC2045] and amended by [RFC2231]. 588 Parameter names are case-insensitive and no meaning is attached to 589 the order in which they appear. It is an error for a specific 590 parameter to be specified more than once. 592 There is no defined syntax for parameter values. Therefore 593 registrations MUST specify parameter value syntax. Additionally, 594 some transports impose restrictions on parameter value syntax, so 595 care needs be taken to limit the use of potentially problematic 596 syntaxes; e.g., pure binary valued parameters, while permitted in 597 some protocols, are best avoided. 599 New parameters SHOULD NOT be defined as a way to introduce new 600 functionality in types registered in the standards tree, although new 601 parameters MAY be added to convey additional information that does 602 not otherwise change existing functionality. An example of this 603 would be a "revision" parameter to indicate a revision level of an 604 external specification such as JPEG. Similar behavior is encouraged 605 for media types registered in the vendor or personal trees, but is 606 not required. 608 Changes to parameters (including the introduction of new ones) is 609 managed in the same manner as other changes to the media type; see 610 Section 5.5. 612 4.4. Canonicalization and Format Requirements 614 All registered media types MUST employ a single, canonical data 615 format, regardless of registration tree. 617 A permanent and readily available public specification of the format 618 for the media type MUST exist for all types registered in the 619 standards tree, and this specification MUST provide sufficient detail 620 so that interoperability between independent implementations using 621 the media type is possible. This specification MUST at a minimum be 622 referenced by, if it is not actually included in, the media type 623 registration proposal itself. 625 The specifications of format and processing particulars may or may 626 not be publicly available for media types registered in the vendor 627 and personal trees, and such registrations are explicitly permitted 628 to limit the information in the registration to which software and 629 version produce or process such media types. As such, references to 630 or inclusion of format specifications in registrations is encouraged 631 but not required. Note, however, that the public availability of a 632 meaningful specification will often make the difference between 633 simply having a name reserved so that there are no conflicts with 634 other uses and having the potential for other implementations of the 635 media type and useful interoperation with them. 637 Some media types involve the use of patented technology. The 638 registration of media types involving patented technology is 639 specifically permitted. However, the restrictions set forth in BCP 640 79 [RFC3979] and BCP 78 [RFC5378] on the use of patented technology 641 in IETF standards-track protocols must be respected when the 642 specification of a media type is part of a standards-track protocol. 643 In addition, other standards bodies making use of the standards tree 644 may have their own rules regarding intellectual property that must be 645 observed in their registrations. 647 IPR disclosures for registrations in the vendor and personal tree are 648 encouraged but not required. 650 4.5. Interchange Recommendations 652 Media types SHOULD interoperate across as many systems and 653 applications as possible. However, some media types will inevitably 654 have problems interoperating across different platforms. Problems 655 with different versions, byte ordering, and specifics of gateway 656 handling can and will arise. 658 Universal interoperability of media types is not required, but known 659 interoperability issues SHOULD be identified whenever possible. 660 Publication of a media type does not require an exhaustive review of 661 interoperability, and the interoperability considerations section is 662 subject to continuing evaluation. 664 These recommendations in this subsection apply regardless of the 665 registration tree involved. 667 4.6. Security Requirements 669 An analysis of security issues MUST be done for all types registered 670 in the standards tree. A similar analysis for media types registered 671 in the vendor or personal trees is encouraged but not required. 672 However, regardless of what security analysis has or has not been 673 done, all descriptions of security issues MUST be as accurate as 674 possible regardless of registration tree. In particular, a statement 675 that there are "no security issues associated with this type" MUST 676 NOT be confused with "the security issues associates with this type 677 have not been assessed". 679 There is absolutely no requirement that media types registered in any 680 tree be secure or completely free from risks. Nevertheless, all 681 known security risks MUST be identified in the registration of a 682 media type, again regardless of registration tree. 684 The security considerations section of all registrations is subject 685 to continuing evaluation and modification, and in particular MAY be 686 extended by use of the "comments on media types" mechanism described 687 in Section 5.4 below. 689 Some of the issues that need to be examined and described in a 690 security analysis of a media type are: 692 o Complex media types may include provisions for directives that 693 institute actions on a recipient's files or other resources. In 694 many cases provision is made for originators to specify arbitrary 695 actions in an unrestricted fashion that may then have devastating 696 effects. See the registration of the application/postscript media 697 type in [RFC2046] for an example of such directives and how they 698 can be described in a media type registration. 700 o Any security analysis MUST state whether or not they employ such 701 "active content", and if they do, they MUST state what steps have 702 been taken to protect users of the media type from harm. 704 o Complex media types may include provisions for directives that 705 institute actions that, while not directly harmful to the 706 recipient, may result in disclosure of information that either 707 facilitates a subsequent attack or else violates a recipient's 708 privacy in some way. Again, the registration of the application/ 709 postscript media type illustrates how such directives can be 710 handled. 712 o A media type that employs compression may provide an opportunity 713 for sending a small amount of data that, when received and 714 evaluated, expands enormously to consume all of the recipient's 715 resources. All media types SHOULD state whether or not they 716 employ compression, and if they do they SHOULD discuss what steps 717 need to be taken to avoid such attacks. 719 o A media type might be targeted for applications that require some 720 sort of security assurance but not provide the necessary security 721 mechanisms themselves. For example, a media type could be defined 722 for storage of sensitive medical information that in turn requires 723 external confidentiality and integrity protection services, or 724 which is designed for use only within a secure environment. Types 725 SHOULD always document whether or not they need such servies in 726 their security considerations. 728 4.7. Requirements specific to XML media types 730 There are a number of additional requirements specific to the 731 registration of XML media types. These requirements are specified in 732 [RFC3023]. 734 4.8. Encoding Requirements 736 Some transports impose restrictions on the type of data they can 737 carry. For example, Internet mail traditionally was limited to 7bit 738 US-ASCII text. Encoding schemes are often used to work around such 739 transport limitations. 741 It is therefore useful to note what sort of data a media type can 742 consist of as part of its registration. An "encoding considerations" 743 field is provided for this purpose. Possible values of this field 744 are: 746 7bit: The content of the media type consists solely of CRLF- 747 delimited 7bit US-ASCII text. 749 8bit: The content of the media type consists solely of CRLF- 750 delimited 8bit text. 752 binary: The content consists of an unrestricted sequence of octets. 754 framed: The content consists of a series of frames or packets 755 without internal framing or alignment indicators. Additional out- 756 of-band information is needed to interpret the data properly, 757 including but not necessarily limited to, knowledge of the 758 boundaries between successive frames and knowledge of the 759 transport mechanism. Note that media types of this sort cannot 760 simply be stored in a file or transported as a simple stream of 761 octets; therefore, such media types are unsuitable for use in many 762 traditional protocols. A commonly used transport with framed 763 encoding is the Real-time Transport Protocol, RTP. Additional 764 rules for framed encodings defined for transport using RTP are 765 given in [RFC4855]. 767 Additional restrictions on 7bit and 8bit text are given in Section 768 4.1.1 of [RFC2046]. 770 4.9. Usage and Implementation Non-requirements 772 In the asynchronous mail environment, where information on the 773 capabilities of the remote mail agent is frequently not available to 774 the sender, maximum interoperability is attained by restricting the 775 media types used to those "common" formats expected to be widely 776 implemented. This was asserted in the past as a reason to limit the 777 number of possible media types, and resulted in a registration 778 process with a significant hurdle and delay for those registering 779 media types. 781 However, the need for "common" media types does not require limiting 782 the registration of new media types. If a limited set of media types 783 is recommended for a particular application, that should be asserted 784 by a separate applicability statement specific for the application 785 and/or environment. 787 Therefore, universal support and implementation of a media type is 788 NOT a requirement for registration. However, if a media type is 789 explicitly intended for limited use, this MUST be noted in its 790 registration. The "Restrictions on Usage" field is provided for this 791 purpose. 793 4.10. Publication Requirements 795 Media types registered in the standards tree by the IETF itself MUST 796 be published as RFCs. RFC publication of vendor and personal media 797 type registrations is allowed but not required. In all cases the 798 IANA will retain copies of all media type registrations and "publish" 799 them as part of the media types registration tree itself. 801 As stated previously, standards tree registrations for media types 802 defined in documents produced by other standards bodies MUST be 803 described by a formal standards specification produced by that body. 804 Additionally, any copyright on the registration template MUST allow 805 the IANA to copy it into the IANA registry. 807 Other than IETF registrations in the standards tree, the registration 808 of a media type does not imply endorsement, approval, or 809 recommendation by the IANA or the IETF or even certification that the 810 specification is adequate. To become an Internet Standard, a 811 protocol or data object must go through the IETF standards process. 812 While it provides additional assurances when it is appropriate, this 813 is too difficult and too lengthy a process for the convenient 814 registration of media types. 816 The standards tree exists for media types that do require a 817 substantive review and approval process in a recognized standards 818 body. The vendor and personal trees exist for those media types that 819 do not require such a process. It is expected that applicability 820 statements for particular applications will be published from time to 821 time in the IETF, recommending implementation of, and support for, 822 media types that have proven particularly useful in those contexts. 824 As discussed above, registration of a top-level type requires 825 Standards Action in the IETF and, hence, the publication of a RFC on 826 the Standards Track. 828 4.11. Fragment Identifier Requirements 830 Media type registrations can specify how applications should 831 interpret fragment identifiers (specified in section 3.5 of 832 [RFC3986]) associated with the media type. 834 Media types are encouraged to adopt fragment identifier schemes that 835 are used with semantically similar media types. In particular, media 836 types that use a named structured syntax with a registered "+suffix" 837 MUST follow whatever fragment identifier rules are given in the 838 structured syntax suffix registration. 840 4.12. Additional Information 842 Various sorts of optional information SHOULD be included in the 843 specification of a media type if it is available: 845 o Magic number(s) (length, octet values). Magic numbers are byte 846 sequences that are always present at a given place in the file and 847 thus can be used to identify entities as being of a given media 848 type. 850 o File name extension(s) commonly used on one or more platforms to 851 indicate that some file contains a given media type. 853 o Mac OS File Type code(s) (4 octets) used to label files containing 854 a given media type. Some discussion of Macintosh file type codes 855 and their purpose can be found in [MacOSFileTypes]. 857 In the case of a registration in the standards tree, this additional 858 information MAY be provided in the formal specification of the media 859 type format. It is suggested that this be done by incorporating the 860 IANA media type registration form into the format specification 861 itself. 863 5. Media Type Registration Procedures 865 The media type registration procedure is not a formal standards 866 process, but rather an administrative procedure intended to allow 867 community comment and sanity checking without excessive time delay. 869 Normal IETF processes need to be followed for all IETF registrations 870 in the standards tree. The posting of an Internet Draft is a 871 necessary first step, followed by posting to the media-types@iana.org 872 list as discussed below. 874 5.1. Preliminary Community Review 876 Notice of a potential media type registration in the standards tree 877 SHOULD be sent to the media-types@iana.org mailing list for review. 878 This mailing list has been established for the purpose of reviewing 879 proposed media and access types. Registrations in other trees MAY be 880 sent to the list for review as well; doing so is entirely OPTIONAL, 881 but is strongly encouraged. 883 The intent of the public posting to this list is to solicit comments 884 and feedback on the choice of type/subtype name, the unambiguity of 885 the references with respect to versions and external profiling 886 information, and a review of any interoperability or security 887 considerations. The submitter may submit a revised registration 888 proposal or abandon the registration completely and at any time. 890 5.2. Submit request to IANA 892 Media types registered in the standards tree by the IETF itself MUST 893 be reviewed and approved by the IESG as part of the normal standards 894 process. Standards tree registrations by recognized standards bodies 895 as well as registrations in the vendor and personal tree are 896 submitted directly to the IANA, unless other arrangements were made 897 as part of a liaison agreement. In either case posting the 898 registration to the media-types@iana.org list for review prior to 899 submission is strongly encouraged. 901 Registration requests can be sent to iana@iana.org. A web form for 902 registration requests is also available: 904 http://www.iana.org/cgi-bin/mediatypes.pl 906 5.2.1. Provisional Registrations 908 Standardization processes often take considerable time to complete. 909 In order to facilitate prototyping and testing it is often helpful to 910 assign identifiers, including but not limited to media types, early 911 in the process. This way identifiers used during standards 912 development can remain unchanged once the process is complete and 913 implementations and documentation do not have to be updated. 915 Accordingly, a provisional registration process is provided to 916 support early assignment of media type names. A provisional 917 registration MAY be submitted to IANA for standards tree types. The 918 only required fields in such registrations are the media type name 919 and contact information (including the standards body name). 921 Upon receipt of a provisional registration, IANA will check the name 922 and contact information, then publish the registration in a separate 923 provisional registration list. 925 Provisional registrations MAY be updated or abandoned at any time. 927 5.3. Review and Approval 929 With the exception of provisional standards tree registrations, 930 registrations submitted to the IANA will be passed on to the media 931 types reviewer. The media types reviewer, who is appointed by the 932 IETF Applications Area Director(s), will review the registration to 933 make sure it meets the requirements set forth in this document. 934 Registrations that do not meet these requirements will be returned to 935 the submitter for revision. 937 Decisions made by the media types reviewer may be appealed to the 938 IESG using the procedure specified in section 6.5.4 of [RFC2026]. 940 Once a media type registration has passed review, the IANA will 941 register the media type and make the media type registration 942 available to the community. 944 In the case of standards tree registrations from other standards 945 bodies IANA will also check that the submitter is in fact a 946 recognized standards body. If the submitter is not currently 947 recognized as such the IESG will be asked to confirm their status. 948 Recognition from the IESG MUST be obtained before a standards tree 949 registration can proceed. 951 5.4. Comments on Media Type Registrations 953 Comments on registered media types may be submitted by members of the 954 community to the IANA at iana@iana.org. These comments will be 955 reviewed by the media types reviewer and then passed on to the 956 "owner" of the media type if possible. Submitters of comments may 957 request that their comment be attached to the media type registration 958 itself, and if the IANA, in consultation with the media types 959 reviewer, approves, the comment will be made accessible in 960 conjunction with the type registration. 962 5.5. Change Procedures 964 Once a media type has been published by the IANA, the owner may 965 request a change to its definition. The descriptions of the 966 different registration trees above designate the "owners" of each 967 type of registration. The same procedure that would be appropriate 968 for the original registration request is used to process a change 969 request. 971 Media type registrations may not be deleted; media types that are no 972 longer believed appropriate for use can be declared OBSOLETE by a 973 change to their "intended use" field; such media types will be 974 clearly marked in the lists published by the IANA. 976 Significant changes to a media type's definition should be requested 977 only when there are serious omissions or errors in the published 978 specification. When review is required, a change request may be 979 denied if it renders entities that were valid under the previous 980 definition invalid under the new definition. 982 The owner of a media type may pass responsibility to another person 983 or agency by informing the IANA; this can be done without discussion 984 or review. 986 The IESG may reassign responsibility for a media type. The most 987 common case of this will be to enable changes to be made to types 988 where the author of the registration has died, moved out of contact 989 or is otherwise unable to make changes that are important to the 990 community. 992 5.6. Registration Template 994 Type name: 996 Subtype name: 998 Required parameters: 1000 Optional parameters: 1002 Encoding considerations: 1004 Security considerations: 1006 Interoperability considerations: 1008 Published specification: 1010 Applications that use this media type: 1012 Fragment identifier considerations: 1014 Additional information: 1016 Deprecated alias names for this type: 1017 Magic number(s): 1018 File extension(s): 1019 Macintosh file type code(s): 1021 Person & email address to contact for further information: 1023 Intended usage: 1025 (One of COMMON, LIMITED USE or OBSOLETE.) 1027 Restrictions on usage: 1029 (Any restrictions on where the media type can be used go here.) 1031 Author: 1033 Change controller: 1035 Provisional registration? (standards tree only): 1037 (Any other information that the author deems interesting may be 1038 added below this line.) 1039 "N/A", written exactly that way, can be used in any field if desired 1040 to emphasize the fact that it does not apply or that the question was 1041 not omitted by accident. Do not use 'none' or other words that could 1042 be mistaken for a response. 1044 Limited use media types should also note in the applications list 1045 whether or not that list is exhaustive. 1047 6. Structured Syntax Suffix Registration Procedures 1049 Someone wishing to define a "+suffix" name for a structured syntax 1050 for use with a new media type registration SHOULD: 1052 1. Check IANA's registry of media type name suffixes to see whether 1053 or not there is already an entry for that well-defined structured 1054 syntax. 1056 2. If there is no entry for their suffix scheme, fill out the 1057 template (specified in Section 6.2) and include that with the 1058 media type registration. The template may be contained in an 1059 Internet Draft, alone or as part of some other protocol 1060 specification. The template may also be submitted in some other 1061 form (as part of another document or as a stand-alone document), 1062 but the contents will be treated as an "IETF Contribution" under 1063 the guidelines of BCP 78 [RFC5378]. 1065 3. Send a copy of the template or a pointer to the containing 1066 document (with specific reference to the section with the 1067 template) to the mailing list media-types@iana.org, requesting 1068 review. This may be combined with a request to review the media 1069 type registration. Allow a reasonable time for discussion and 1070 comments. 1072 4. Respond to review comments and make revisions to the proposed 1073 registration as needed to bring it into line with the guidelines 1074 given in this document. 1076 5. Submit the (possibly updated) registration template (or pointer 1077 to the document containing it) to IANA at iana@iana.org. 1079 Upon receipt of a structured syntax suffix registration request, 1081 1. IANA checks the submission for completeness; if sections are 1082 missing or citations are not correct, IANA rejects the 1083 registration request. 1085 2. IANA checks the current registry for an entry with the same name; 1086 if such a registry exists, IANA rejects the registration request. 1088 3. IANA requests Expert Review of the registration request against 1089 the corresponding guidelines. 1091 4. The Designated Expert may request additional review or 1092 discussion, as necessary. 1094 5. If Expert Review recommends registration, IANA adds the 1095 registration to the appropriate registry. 1097 6.1. Change Procedures 1099 Registrations may be updated in each registry by the same mechanism 1100 as required for an initial registration. In cases where the original 1101 definition of the scheme is contained in an IESG-approved document, 1102 update of the specification also requires IESG approval. 1104 6.2. Structured Syntax Suffix Registration Template 1106 This template describes the fields that must be supplied in a 1107 structured syntax suffix registration request: 1109 Name 1110 Full name of the well-defined structured syntax. 1112 +suffix 1113 Suffix used to indicate conformance to the syntax. 1115 References 1116 Include full citations for all specifications necessary to 1117 understand the structured syntax. 1119 Encoding considerations 1120 General guidance regarding encoding considerations for any type 1121 employing this syntax should be given here. The same requirements 1122 for media type encoding considerations given in Section 4.8 apply 1123 here. 1125 Interoperability considerations 1126 Any issues regarding the interoperable use of types employing this 1127 structured syntax should be given here. Examples would include 1128 the existence of incompatible versions of the syntax, issues 1129 combining certain charsets with the syntax, or incompatibilities 1130 with other types or protocols. 1132 Fragment identifier considerations 1133 Generic processing of fragment identifiers for any type employing 1134 this syntax should be described here. 1136 Security considerations 1137 Security considerations shared by media types employing this 1138 structured syntax must be specified here. The same requirements 1139 for media type security considerations given in Section 4.6 apply 1140 here, with the exception that option of not assessing the security 1141 considerations is not available for suffix registrations. 1143 Contact 1144 Person (including contact information) to contact for further 1145 information. 1147 Author/Change controller. 1148 Person (including contact information) authorized to change this 1149 suffix registration. 1151 7. Security Considerations 1153 Security requirements for media type registrations are discussed in 1154 Section 4.6. 1156 8. IANA Considerations 1158 The purpose of this document is to define IANA registries for media 1159 types and structured syntax suffixes as well as the procedures for 1160 managing these registries. Additionally, this document requires IANA 1161 to maintain a list of IESG-recognized standards bodies who are 1162 allowed to register types in the standards tree. 1164 This document also creates a new registry for structured syntax 1165 names: 1167 o The name is the "Structured Syntax Suffix" registry. 1169 o The registration process is specified in Section 6. 1171 o The information required for a registry entry as well as the entry 1172 format are specified in Section 6.2. 1174 o The initial content of the registry is specified in 1175 [I-D.appsawg-media-type-suffix-regs]. 1177 Finally, this document calls for the creation of a new email address, 1178 media-types@iana.org, for the media type review list, which replaces 1179 the ietf-types@iana.org address specified in RFC 4288. 1180 ietf-types@iana.org should be retained as an alias. 1182 9. Acknowledgements 1184 The current authors would like to acknowledge their debt to the late 1185 Dr. Jon Postel, whose general model of IANA registration procedures 1186 and specific contributions shaped the predecessors of this document 1187 [RFC2048] [RFC4288]. We hope that the current version is one with 1188 which he would have agreed but, as it is impossible to verify that 1189 agreement, we have regretfully removed his name as a co-author. 1191 Randy Bush, Bjoern Hoehrmann, Barry Leiba, Murray Kucherawy, Alexey 1192 Melnikov, S. Moonesamy, Mark Nottingham, Tom Petch, Peter Saint- 1193 Andre, and Jeni Tennison provided many helpful review comments and 1194 suggestions. 1196 10. References 1198 10.1. Normative References 1200 [I-D.appsawg-media-type-suffix-regs] 1201 Hansen, T., "Additional Media Type Structured Syntax 1202 Suffixes", draft-appsawg-media-type-suffix-regs-00 (work 1203 in progress), April 2012. 1205 [I-D.ietf-appsawg-mime-default-charset] 1206 Melnikov, A. and J. Reschke, "Update to MIME regarding 1207 Charset Parameter Handling in Textual Media Types", 1208 draft-ietf-appsawg-mime-default-charset-01 (work in 1209 progress), March 2012. 1211 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1212 Extensions (MIME) Part One: Format of Internet Message 1213 Bodies", RFC 2045, November 1996. 1215 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1216 Extensions (MIME) Part Two: Media Types", RFC 2046, 1217 November 1996. 1219 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1220 Requirement Levels", BCP 14, RFC 2119, March 1997. 1222 [RFC2978] Freed, N. and J. Postel, "IANA Charset Registration 1223 Procedures", BCP 19, RFC 2978, October 2000. 1225 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 1226 Types", RFC 3023, January 2001. 1228 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 1229 10646", STD 63, RFC 3629, November 2003. 1231 [RFC3979] Bradner, S., "Intellectual Property Rights in IETF 1232 Technology", BCP 79, RFC 3979, March 2005. 1234 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1235 Resource Identifier (URI): Generic Syntax", STD 66, 1236 RFC 3986, January 2005. 1238 [RFC4855] Casner, S., "Media Type Registration of RTP Payload 1239 Formats", RFC 4855, February 2007. 1241 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1242 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1243 May 2008. 1245 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 1246 Specifications: ABNF", STD 68, RFC 5234, January 2008. 1248 [RFC5378] Bradner, S. and J. Contreras, "Rights Contributors Provide 1249 to the IETF Trust", BCP 78, RFC 5378, November 2008. 1251 [RFC6532] Yang, A., Steel, S., and N. Freed, "Internationalized 1252 Email Headers", RFC 6532, January 2012. 1254 10.2. Informative References 1256 [I-D.ietf-appsawg-xdash] 1257 Saint-Andre, P. and D. Crocker, "Deprecating the X- Prefix 1258 and Similar Constructs in Application Protocols", 1259 draft-ietf-appsawg-xdash-05 (work in progress), 1260 April 2012. 1262 [MacOSFileTypes] 1263 Apple Computer, Inc., "Mac OS: File Type and Creator 1264 Codes, and File Formats", Apple Knowledge Base Article 1265 55381, June 1993, 1266 . 1268 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 1269 3", BCP 9, RFC 2026, October 1996. 1271 [RFC2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose 1272 Internet Mail Extensions (MIME) Part Four: Registration 1273 Procedures", BCP 13, RFC 2048, November 1996. 1275 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 1276 Word Extensions: 1277 Character Sets, Languages, and Continuations", RFC 2231, 1278 November 1997. 1280 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 1281 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 1282 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 1284 [RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and 1285 Registration Procedures", BCP 13, RFC 4288, December 2005. 1287 Appendix A. Grandfathered Media Types 1289 A number of media types with unfaceted subtype names, registered 1290 prior to 1996, would, if registered under the guidelines in this 1291 document, be given a faceted name and placed into either the vendor 1292 or personal trees. Reregistration of those types to reflect the 1293 appropriate trees is encouraged but not required. Ownership and 1294 change control principles outlined in this document apply to those 1295 types as if they had been registered in the trees described above. 1297 From time to time there may also be cases where a media type with an 1298 unfaceted subtype name has been widely deployed without being 1299 registered. (Note that this includes subtype names beginning with 1300 the "x-" prefix.) If possible such media type SHOULD be reregistered 1301 with a proper faceted subtype name. However, if this is not possible 1302 the type can, subject to approval by both the media types reviewer 1303 and the IESG, be registered in the proper tree with its unfaceted 1304 name. 1306 Appendix B. Changes Since RFC 4288 1308 o Suffixes to indicate the use of a particular structured syntax are 1309 now fully specified and a suffix registration process has been 1310 defined. 1312 o Registration of widely deployed unregistered unfaceted type names 1313 in the vendor or personal trees is now allowed, subject to 1314 approval by the media types reviewer and the IESG. 1316 o The standards tree registration process has been revised to 1317 include Expert Review and generalized to address cases like media 1318 types in non-IETF stream documents. 1320 o A field for fragment identifiers has been added to the 1321 registration template and brief directions for specifying fragment 1322 identifiers have been added. 1324 o The specification requirements for personal tree registrations 1325 have been changed to be the same as those for the vendor tree. 1326 The text has been changed to encourage (but not require) 1327 specification availability. 1329 o The definition of additional trees has been clarified to state 1330 that an IETF Standards Action is required. 1332 o Widely deployed types with "x-" names can now be registered as an 1333 exception in the vendor tree. 1335 o The requirements on changes to registrations have been loosened so 1336 minor changes are easier to make. 1338 o The registration process has been completely restructured so that 1339 with the exception of IETF-generated types in the standards tree, 1340 all requests are processed by IANA and not the IESG. 1342 o A provisional registration process has been added for early 1343 assignment of types in the standards tree. 1345 o Many editorial changes have been made throughout the document to 1346 make the requirements and processes it describes clearer and 1347 easier to follow. 1349 o The ability to specify a list of deprecated aliases for a media 1350 type has been added. 1352 o Types with names beginning with "x-" are no longer considered to 1353 be members of the unregistered "x." tree. As with any unfaceted 1354 type, special procedures have been added to allow registration of 1355 such types in an appropriate tree. 1357 o Changes to a type registered by a third party may now be made by 1358 the designated change controller even if that isn't the vendor or 1359 organization that created the type. However, the vendor or 1360 organization may elect to assert ownership and change controller 1361 over the type at any time. 1363 o Limited use media types are now asked to note whether or not the 1364 supplied list of applications employing the media type is 1365 exhaustive. 1367 o The ABNF for media type names has been further restricted to 1368 require that names begin with an alphanumeric character. 1370 o Mailing list review is no longer required prior to registration of 1371 media types. Additionally, the address associated with the media 1372 type review mailing list has been changed to media-types@iana.org. 1374 Authors' Addresses 1376 Ned Freed 1377 Oracle 1378 800 Royal Oaks 1379 Monrovia, CA 91016-6347 1380 USA 1382 Email: ned+ietf@mrochek.com 1384 John C. Klensin 1385 1770 Massachusetts Ave, #322 1386 Cambridge, MA 02140 1387 USA 1389 Email: john+ietf@jck.com 1391 Tony Hansen 1392 AT&T Laboratories 1393 200 Laurel Ave. 1394 Middletown, NJ 07748 1395 USA 1397 Email: tony+mtsuffix@maillennium.att.com