idnits 2.17.00 (12 Aug 2021) /tmp/idnits40626/draft-ietf-appsawg-media-type-regs-07.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == There are 1 instance of lines with non-RFC2606-compliant FQDNs in the document. -- The draft header indicates that this document obsoletes RFC4288, but the abstract doesn't seem to mention this, which it should. 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'I-D.appsawg-media-type-suffix-regs' == Outdated reference: draft-ietf-appsawg-mime-default-charset has been published as RFC 6657 ** Obsolete normative reference: RFC 3023 (Obsoleted by RFC 7303) ** Obsolete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reference: RFC 3979 (Obsoleted by RFC 8179) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) == Outdated reference: draft-ietf-appsawg-xdash has been published as RFC 6648 -- Obsolete informational reference (is this intentional?): RFC 2048 (Obsoleted by RFC 4288,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 (==), 7 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 5, 2012 T. Hansen 7 AT&T Laboratories 8 May 4, 2012 10 Media Type Specifications and Registration Procedures 11 draft-ietf-appsawg-media-type-regs-07 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 5, 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 . . . . . . . . . . . . 4 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 . . . . . . . . . . . . . . . . . . . 7 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 . . . . . . . . . 16 80 4.8. Encoding Requirements . . . . . . . . . . . . . . . . . . 16 81 4.9. Usage and Implementation Non-requirements . . . . . . . . 17 82 4.10. Publication Requirements . . . . . . . . . . . . . . . . . 18 83 4.11. Fragment Identifier Requirements . . . . . . . . . . . . . 18 84 4.12. Additional Information . . . . . . . . . . . . . . . . . . 19 85 5. Media Type Registration Procedures . . . . . . . . . . . . . . 19 86 5.1. Preliminary Community Review . . . . . . . . . . . . . . . 19 87 5.2. Submit request to IANA . . . . . . . . . . . . . . . . . . 20 88 5.2.1. Provisional Registrations . . . . . . . . . . . . . . 20 89 5.3. Review and Approval . . . . . . . . . . . . . . . . . . . 20 90 5.4. Comments on Media Type Registrations . . . . . . . . . . . 21 91 5.5. Location of Registered Media Type List . . . . . . . . . . 21 92 5.6. Change Procedures . . . . . . . . . . . . . . . . . . . . 21 93 5.7. Registration Template . . . . . . . . . . . . . . . . . . 23 94 6. Structured Syntax Suffix Registration Procedures . . . . . . . 24 95 6.1. Change Procedures . . . . . . . . . . . . . . . . . . . . 25 96 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. A mechanism is needed 113 to label such content and a registration process is needed for these 114 labels, so that that the set of such values are defined in a 115 reasonably orderly, well-specified, and public manner. 117 This document defines media type specification and registration 118 procedures that use the Internet Assigned Numbers Authority (IANA) as 119 a central registry. 121 1.1. Historical Note 123 The media type registration process was initially defined for 124 registering media types for use in the context of the asynchronous 125 Internet mail environment. In this mail environment there is a need 126 to limit the number of possible media types, to increase the 127 likelihood of interoperability when the capabilities of the remote 128 mail system are not known. As media types are used in new 129 environments in which the proliferation of media types is not a 130 hindrance to interoperability, the original procedure proved 131 excessively restrictive and had to be generalized. This was 132 initially done in [RFC2048], but the procedure defined there was 133 still part of the MIME document set. The media type specification 134 and registration procedure has now been moved to this separate 135 document, to make it clear that it is independent of MIME. 137 It may be desirable to restrict the use of media types to specific 138 environments or to prohibit their use in other environments. This 139 revision incorporates such restrictions into media type registrations 140 in a systematic way. See Section 4.9 for additional discussion. 142 1.2. Conventions Used in This Document 144 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 145 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 146 document are to be interpreted as described in [RFC2119]. 148 This specification makes use of the Augmented Backus-Naur Form (ABNF) 149 [RFC5234] notation, including the core rules defined in Appendix A of 150 that document. 152 2. Media Type Registration Preliminaries 154 Registration of a new media type or types starts with the 155 construction of a registration proposal. Registration may occur 156 within several different registration trees that have different 157 requirements, as discussed below. In general, a new registration 158 proposal is circulated and reviewed in a fashion appropriate to the 159 tree involved. The media type is then registered if the proposal is 160 acceptable. The following sections describe the requirements and 161 procedures used for each of the different registration trees. 163 3. Registration Trees and Subtype Names 165 In order to increase the efficiency and flexibility of the 166 registration process, different structures of subtype names may be 167 registered to accommodate the different natural requirements for, 168 e.g., a subtype that will be recommended for wide support and 169 implementation by the Internet community, or a subtype that is used 170 to move files associated with proprietary software. The following 171 subsections define registration "trees" that are distinguished by the 172 use of faceted names, e.g., names of the form 173 "tree.subtree...subtype". Note that some media types defined prior 174 to this document do not conform to the naming conventions described 175 below. See Appendix A for a discussion of them. 177 3.1. Standards Tree 179 The standards tree is intended for types of general interest to the 180 Internet community. Registrations in the standards tree MUST be 181 either: 183 1. in the case of registrations in IETF specifications, approved 184 directly by the IESG, or 186 2. registered by a recognized standards body using the 187 "Specification Required" IANA registration policy [RFC5226] 188 (which implies Expert Review). 190 The first procedure is used for registering registrations from IETF 191 Consensus documents, or in rare cases when registering a 192 grandfathered (see Appendix A) and/or otherwise incomplete 193 registration is in the interest of the Internet community. 195 In the second case the IESG makes a one time decision on whether the 196 registration submitter represents a recognized standards body; after 197 that, a Media Types Reviewer (Designated Expert or a group of 198 Designated Experts) performs the Expert Review as specified in this 199 document. Subsequent submissions from the same source do not involve 200 the IESG. 202 In the case of registration for the IETF itself, the registration 203 proposal MUST be published as an RFC. When the RFC is in the IETF 204 stream it is an IETF Consensus RFC, which can be on the Standards 205 Track, a BCP, Informational, or Experimental. Registrations 206 published in non-IETF RFC streams are also allowed, and require IESG 207 approval. 209 In the case of registrations for other recognized standards bodies, 210 the format MUST be described by a formal standards specification 211 produced by that body. 213 A standards-tree registration can be either in a standalone 214 "registration only" RFC or incorporated into a more general 215 specification of some sort. 217 Media types in the standards tree are normally denoted by names that 218 are not explicitly faceted, i.e., do not contain period (".", full 219 stop) characters. 221 The "owner" of a media type registration in the standards tree is 222 assumed to be the standards body itself. Modification or alteration 223 of the specification uses the same level of processing (e.g., a 224 registration submitted on Standards Track can be revised in another 225 Standards Track RFC, but cannot be revised in an Informational RFC) 226 required for the initial registration. 228 Standards-tree registrations from recognized standards bodies may be 229 submitted directly to the IANA, where they will undergo Expert Review 230 [RFC5226] prior to approval. In this case, the Expert Reviewer(s) 231 will, among other things, ensure that the required specification 232 provides adequate documentation. 234 3.2. Vendor Tree 236 The vendor tree is used for media types associated with publicly 237 available products. "Vendor" and "producer" are construed very 238 broadly in this context and are considered equivalent. Note that 239 industry consortia as well as non-commercial entities that do not 240 qualify as recognized standards bodies can quite appropriately 241 register media types in the vendor tree. 243 A registration may be placed in the vendor tree by anyone who needs 244 to interchange files associated with some product or set of products. 245 However, the registration properly belongs to the vendor or 246 organization producing the software that employs the type being 247 registered, and that vendor or organization can at any time elect to 248 assert ownership of a registration done by a third party in order to 249 correct or update it. See Section 5.6 for additional information. 251 When a third party registers a type on behalf of someone else both 252 entities SHOULD be noted in the Change Controller field in the 253 registration. One possible format for this would be "Foo, on behalf 254 of Bar". 256 Registrations in the vendor tree will be distinguished by the leading 257 facet "vnd.". That may be followed, at the discretion of the 258 registrant, by either a media subtype name from a well-known producer 259 (e.g., "vnd.mudpie") or by an IANA-approved designation of the 260 producer's name that is followed by a media type or product 261 designation (e.g., vnd.bigcompany.funnypictures). 263 While public exposure and review of media types to be registered in 264 the vendor tree is not required, using the media-types@iana.org 265 mailing list for review is encouraged to improve the quality of those 266 specifications. Registrations in the vendor tree may be submitted 267 directly to the IANA, where they will undergo Expert Review [RFC5226] 268 prior to approval. 270 3.3. Personal or Vanity Tree 272 Registrations for media types created experimentally or as part of 273 products that are not distributed commercially may be registered in 274 the personal or vanity tree. The registrations are distinguished by 275 the leading facet "prs.". 277 The owner of "personal" registrations and associated specifications 278 is the person or entity making the registration, or one to whom 279 responsibility has been transferred as described below. 281 While public exposure and review of media types to be registered in 282 the personal tree is not required, using the media-types@iana.org 283 mailing list (see Section 5.1) for review is encouraged to improve 284 the quality of those specifications. Registrations in the personal 285 tree may be submitted directly to the IANA, where they will undergo 286 Expert Review [RFC5226] prior to approval. 288 3.4. Unregistered x. Tree 290 Subtype names with "x." as the first facet may be used for types 291 intended exclusively for use in private, local environments. Types 292 in this tree cannot be registered and are intended for use only with 293 the active agreement of the parties exchanging them. 295 However, with the simplified registration procedures described above 296 for vendor and personal trees, it should rarely, if ever, be 297 necessary to use unregistered types. Therefore, use of types in the 298 "x." tree is strongly discouraged. 300 Note that types with names beginning with "x-" are no longer 301 considered to members of this tree (see [I-D.ietf-appsawg-xdash]). 302 Also note that if a generally useful and widely deployed type 303 incorrectly ends up with an "x-" name prefix, it MAY be registered 304 using its current name in an alternate tree by following the 305 procedure defined in Appendix A. 307 3.5. Additional Registration Trees 309 From time to time and as required by the community, new top-level 310 registration trees may be created by IETF Standards Action. It is 311 explicitly assumed that these trees may be created for external 312 registration and management by well-known permanent bodies; for 313 example, scientific societies may register media types specific to 314 the sciences they cover. In general, the quality of review of 315 specifications for one of these additional registration trees is 316 expected to be equivalent to registrations in the standards tree by a 317 recognized Standards Development Organization. When the IETF 318 performs such review, it needs to consider the greater expertise of 319 the requesting body with respect to the subject media type. 321 4. Registration Requirements 323 Media type registrations are all expected to conform to various 324 requirements laid out in the following sections. Note that 325 requirement specifics sometimes vary depending on the registration 326 tree, again as detailed in the following sections. 328 4.1. Functionality Requirement 330 Media types MUST function as actual media formats. Registration of 331 things that are better thought of as a transfer encoding, as a 332 charset, or as a collection of separate entities of another type, is 333 not allowed. For example, although applications exist to decode the 334 base64 transfer encoding [RFC2045], base64 cannot be registered as a 335 media type. 337 This requirement applies regardless of the registration tree 338 involved. 340 4.2. Naming Requirements 342 All registered media types MUST be assigned type and subtype names. 343 The combination of these names serves to uniquely identify the media 344 type, and the format of the subtype name identifies the registration 345 tree. Both type and subtype names are case-insensitive. 347 Type and subtype names MUST conform to the following ABNF: 349 type-name = restricted-name 350 subtype-name = restricted-name 352 restricted-name = restricted-name-first *126restricted-name-chars 353 restricted-name-first = ALPHA / DIGIT 354 restricted-name-chars = ALPHA / DIGIT / "!" / "#" / 355 "$" / "&" / "-" / "^" / "_" 356 restricted-name-chars =/ "." ; Characters before first dot always 357 ; specify a facet name 358 restricted-name-chars =/ "+" ; Characters after last plus always 359 ; specify a structured syntax suffix 361 Note that this syntax is somewhat more restrictive than what is 362 allowed by the ABNF in section 5.1 of [RFC2045] or section 4.2 of 363 [RFC4288]. Also note that while this syntax allows names of up to 364 127 characters, implementation limits may make such long names 365 problematic. For this reason the components of names SHOULD be 366 limited to 64 characters. 368 Although the name syntax treats "." as equivalent to any other 369 character, characters before any initial "." always specify the 370 registration facet. Note that this means that facet-less standards 371 tree registrations cannot use periods in the subtype name. 373 Similarly, "+" is used in media type names to introduce a structured 374 syntax specifier suffix. Structured syntax suffix requirements are 375 specified in Section 4.2.8. 377 While it is possible for a given media type to be assigned additional 378 names, the use of different names to identify the same media type is 379 discouraged. 381 These requirements apply regardless of the registration tree 382 involved. 384 The choice of top-level type name MUST take into account the nature 385 of media type involved. New subtypes of top-level types MUST conform 386 to the restrictions of the top-level type, if any. The following 387 sections describe each of the initial set of top-level types and 388 their associated restrictions. Additionally, various protocols, 389 including but not limited to HTTP and MIME, MAY impose additional 390 restrictions on the media types they can transport. (See [RFC2046] 391 for additional information on the restrictions MIME imposes.) 393 4.2.1. Text Media Types 395 The "text" media type is intended for sending material that is 396 principally textual in form. 398 Many subtypes of text, notably including the subtype "text/plain", 399 which is a generic subtype for plain text defined in [RFC2046], 400 define a "charset" parameter. If a "charset" parameter is defined 401 for a particular subtype of text, it MUST be used to specify a 402 charset name defined in accordance to the procedures laid out in 403 [RFC2978]. 405 As specified in [I-D.ietf-appsawg-mime-default-charset], a "charset" 406 parameter SHOULD NOT be specified when charset information is 407 transported inside the payload (e.g., as in "text/xml"). 409 If a "charset" parameter is specified, it SHOULD be a required 410 parameter, eliminating the options of specifying a default value. If 411 there is a strong reason for the parameter to be optional despite 412 this advice, each subtype MAY specify its own default value, or 413 alternately, it MAY specify that there is no default value. Finally, 414 the "UTF-8" charset [RFC3629] SHOULD be selected as the default. See 415 [I-D.ietf-appsawg-mime-default-charset] for additional information on 416 the use of "charset" parameters in conjunction with subtypes of text. 418 Plain text does not provide for or allow formatting commands, font 419 attribute specifications, processing instructions, interpretation 420 directives, or content markup. Plain text is seen simply as a linear 421 sequence of characters, possibly interrupted by line breaks or page 422 breaks. Plain text MAY allow the stacking of several characters in 423 the same position in the text. Plain text in scripts like Arabic and 424 Hebrew may also include facilities that allow the arbitrary mixing of 425 text segments with different writing directions. 427 Beyond plain text, there are many formats for representing what might 428 be known as "rich text". An interesting characteristic of many such 429 representations is that they are to some extent readable even without 430 the software that interprets them. It is useful to distinguish them, 431 at the highest level, from such unreadable data as images, audio, or 432 text represented in an unreadable form. In the absence of 433 appropriate interpretation software, it is reasonable to present 434 subtypes of "text" to the user, while it is not reasonable to do so 435 with most non-textual data. Such formatted textual data should be 436 represented using subtypes of "text". 438 4.2.2. Image Media Types 440 A media type of "image" indicates that the content specifies one or 441 more individual images. The subtype names the specific image format. 443 4.2.3. Audio Media Types 445 A media type of "audio" indicates that the content contains audio 446 data. 448 4.2.4. Video Media Types 450 A media type of "video" indicates that the content specifies a time- 451 varying-picture image, possibly with color and coordinated sound. 452 The term 'video' is used in its most generic sense, rather than with 453 reference to any particular technology or format, and is not meant to 454 preclude subtypes such as animated drawings encoded compactly. 456 Note that although in general this document strongly discourages the 457 mixing of multiple media in a single body, it is recognized that many 458 so-called video formats include a representation for synchronized 459 audio and/or text, and this is explicitly permitted for subtypes of 460 "video". 462 4.2.5. Application Media Types 464 The "application" media type is to be used for discrete data that do 465 not fit in any of the media types, and particularly for data to be 466 processed by some type of application program. This is information 467 that must be processed by an application before it is viewable or 468 usable by a user. Expected uses for the "application" media type 469 include but are not limited to file transfer, spreadsheets, 470 presentations, scheduling data, and languages for "active" 471 (computational) material. (The last, in particular, can pose 472 security problems that must be understood by implementors, and that 473 are considered in detail in the discussion of the "application/ 474 postscript" media type in [RFC2046].) 476 For example, a meeting scheduler might define a standard 477 representation for information about proposed meeting dates. An 478 intelligent user agent would use this information to conduct a dialog 479 with the user, and might then send additional material based on that 480 dialog. More generally, there have been several "active" languages 481 developed in which programs in a suitably specialized language are 482 transported to a remote location and automatically run in the 483 recipient's environment. Such applications may be defined as 484 subtypes of the "application" media type. 486 The subtype of "application" will often either be the name or include 487 part of the name of the application for which the data are intended. 488 This does not mean, however, that any application program name may 489 simply be used freely as a subtype of "application"; the subtype 490 needs to be registered. 492 4.2.6. Multipart and Message Media Types 494 Multipart and message are composite types, that is, they provide a 495 means of encapsulating zero or more objects, each labeled with its 496 own media type. 498 All subtypes of multipart and message MUST conform to the syntax 499 rules and other requirements specified in [RFC2046] and amended by 500 Section 3.5 of [RFC6532]. 502 4.2.7. Additional Top-level Types 504 In some cases a new media type may not "fit" under any currently 505 defined top-level content type. Such cases are expected to be quite 506 rare. However, if such a case does arise a new top-level type can be 507 defined to accommodate it. Such a definition MUST be done via 508 standards-track RFC; no other mechanism can be used to define 509 additional top-level content types. 511 4.2.8. Structured Syntax Name Suffixes 513 [RFC3023] defined the first such augmentation to the media type 514 definition to additionally specify the underlying structure of that 515 media type. To quote: 517 This document also standardizes a convention (using the suffix 518 '+xml') for naming media types ... when those media types 519 represent XML MIME (Multipurpose Internet Mail Extensions) 520 entities. 522 That is, it specified a suffix (in that case, "+xml") to be appended 523 to the base media type name. 525 Since this was published, the de facto practice has arisen for using 526 this suffix convention for other well-known structuring syntaxes. In 527 particular, media types have been registered with suffixes such as 528 "+der", "+fastinfoset" and "+json". This specification formalizes 529 this practice and sets up a registry for structured type name 530 suffixes. 532 The primary guideline for whether a structured type name suffix 533 should be registrable is that it be described by a readily-available 534 description, preferably within a document published by an established 535 standards organization, and for which there's a reference that can be 536 used in a Normative References section of an RFC. 538 Media types that make use of a named structured syntax SHOULD use the 539 appropriate registered "+suffix" for that structured syntax when they 540 are registered. By the same token, media types MUST NOT be given 541 names incorporating suffixes for structured syntaxes they do not 542 actually employ. "+suffix" constructs for as-yet unregistered 543 structured syntaxes should be used with care, given the possibility 544 of conflicts with future suffix definitions. 546 4.2.9. Deprecated Aliases 548 In some cases a single media type may have been widely deployed prior 549 to registration under multiple names. In such cases a preferred name 550 MUST be chosen for the media type and applications MUST use this to 551 be compliant with the type's registration. However, a list of 552 deprecated aliases the type is known by MAY be supplied as additional 553 information in order to assist applications in processing the media 554 type properly. 556 4.3. Parameter Requirements 558 Media types MAY elect to use one or more media type parameters, or 559 some parameters may be automatically made available to the media type 560 by virtue of being a subtype of a content type that defines a set of 561 parameters applicable to any of its subtypes. In either case, the 562 names, values, and meanings of any parameters MUST be fully specified 563 when a media type is registered in the standards tree, and SHOULD be 564 specified as completely as possible when media types are registered 565 in the vendor or personal trees. 567 Parameter names have the syntax as media type names and values: 569 parameter-name = restricted-name 571 Note that this syntax is somewhat more restrictive than what is 572 allowed by the ABNF in [RFC2045] and amended by [RFC2231]. 574 Parameter names are case-insensitive and no meaning is attached to 575 the order in which they appear. It is an error for a specific 576 parameter to be specified more than once. 578 There is no defined syntax for parameter values. Therefore 579 registrations MUST specify parameter value syntax. Additionally, 580 some transports impose restrictions on parameter value syntax, so 581 care should be taken to limit the use of potentially problematic 582 syntaxes; e.g., pure binary valued parameters, while permitted in 583 some protocols, probably should be avoided. 585 New parameters SHOULD NOT be defined as a way to introduce new 586 functionality in types registered in the standards tree, although new 587 parameters MAY be added to convey additional information that does 588 not otherwise change existing functionality. An example of this 589 would be a "revision" parameter to indicate a revision level of an 590 external specification such as JPEG. Similar behavior is encouraged 591 for media types registered in the vendor or personal trees, but is 592 not required. 594 4.4. Canonicalization and Format Requirements 596 All registered media types MUST employ a single, canonical data 597 format, regardless of registration tree. 599 A permanent and readily available public specification of the format 600 for the media type MUST exist for all types registered in the 601 standards tree, and this specification MUST provide sufficient detail 602 so that interoperability between independent implementations using 603 the media type is possible. This specification MUST at a minimum be 604 referenced by, if it is not actually included in, the media type 605 registration proposal itself. 607 The specifications of format and processing particulars may or may 608 not be publicly available for media types registered in the vendor 609 and personal trees, and such registrations are explicitly permitted 610 to limit the information in the registration to which software and 611 version produce or process such media types. As such, references to 612 or inclusion of format specifications in registrations is encouraged 613 but not required. Note, however, that the public availability of a 614 meaningful specification will often make the difference between 615 simply having a name reserved so that there are no conflicts with 616 other uses and having the potential for other implementations of the 617 media type and useful interoperation with them. 619 Some media types involve the use of patented technology. The 620 registration of media types involving patented technology is 621 specifically permitted. However, the restrictions set forth in BCP 622 79 [RFC3979] and BCP 78 [RFC5378] on the use of patented technology 623 in IETF standards-track protocols must be respected when the 624 specification of a media type is part of a standards-track protocol. 625 In addition, other standards bodies making use of the standards tree 626 may have their own rules regarding intellectual property that must be 627 observed in their registrations. 629 IPR disclosures for registrations in the vendor and personal tree are 630 encouraged but not required. 632 4.5. Interchange Recommendations 634 Media types SHOULD interoperate across as many systems and 635 applications as possible. However, some media types will inevitably 636 have problems interoperating across different platforms. Problems 637 with different versions, byte ordering, and specifics of gateway 638 handling can and will arise. 640 Universal interoperability of media types is not required, but known 641 interoperability issues SHOULD be identified whenever possible. 642 Publication of a media type does not require an exhaustive review of 643 interoperability, and the interoperability considerations section is 644 subject to continuing evaluation. 646 These recommendations in this subsection apply regardless of the 647 registration tree involved. 649 4.6. Security Requirements 651 An analysis of security issues MUST be done for all types registered 652 in the standards tree. A similar analysis for media types registered 653 in the vendor or personal trees is encouraged but not required. 654 However, regardless of what security analysis has or has not been 655 done, all descriptions of security issues MUST be as accurate as 656 possible regardless of registration tree. In particular, a statement 657 that there are "no security issues associated with this type" MUST 658 NOT be confused with "the security issues associates with this type 659 have not been assessed". 661 There is absolutely no requirement that media types registered in any 662 tree be secure or completely free from risks. Nevertheless, all 663 known security risks MUST be identified in the registration of a 664 media type, again regardless of registration tree. 666 The security considerations section of all registrations is subject 667 to continuing evaluation and modification, and in particular MAY be 668 extended by use of the "comments on media types" mechanism described 669 in Section 5.4 below. 671 Some of the issues that should be examined and described in a 672 security analysis of a media type are: 674 o Complex media types may include provisions for directives that 675 institute actions on a recipient's files or other resources. In 676 many cases provision is made for originators to specify arbitrary 677 actions in an unrestricted fashion that may then have devastating 678 effects. See the registration of the application/postscript media 679 type in [RFC2046] for an example of such directives and how they 680 should be described in a media type registration. 682 o All registrations MUST state whether or not they employ such 683 "active content", and if they do, they MUST state what steps have 684 been taken to protect users of the media type from harm. 686 o Complex media types may include provisions for directives that 687 institute actions that, while not directly harmful to the 688 recipient, may result in disclosure of information that either 689 facilitates a subsequent attack or else violates a recipient's 690 privacy in some way. Again, the registration of the application/ 691 postscript media type illustrates how such directives can be 692 handled. 694 o A media type that employs compression may provide an opportunity 695 for sending a small amount of data that, when received and 696 evaluated, expands enormously to consume all of the recipient's 697 resources. All media types SHOULD state whether or not they 698 employ compression, and if they do they should discuss what steps 699 need to be taken to avoid such attacks. 701 o A media type might be targeted for applications that require some 702 sort of security assurance but not provide the necessary security 703 mechanisms themselves. For example, a media type could be defined 704 for storage of sensitive medical information that in turn requires 705 external confidentiality and integrity protection services, or 706 which is designed for use only within a secure environment. Types 707 not requiring such services SHOULD document this in their security 708 considerations. 710 4.7. Requirements specific to XML media types 712 There are a number of additional requirements specific to the 713 registration of XML media types. These requirements are specified in 714 [RFC3023]. 716 4.8. Encoding Requirements 718 Some transports impose restrictions on the type of data they can 719 carry. For example, Internet mail traditionally was limited to 7bit 720 US-ASCII text. Encoding schemes are often used to work around such 721 transport limitations. 723 It is therefore useful to note what sort of data a media type can 724 consist of as part of its registration. An "encoding considerations" 725 field is provided for this purpose. Possible values of this field 726 are: 728 7bit: The content of the media type consists solely of CRLF- 729 delimited 7bit US-ASCII text. 731 8bit: The content of the media type consists solely of CRLF- 732 delimited 8bit text. 734 binary: The content consists of an unrestricted sequence of octets. 736 framed: The content consists of a series of frames or packets 737 without internal framing or alignment indicators. Additional out- 738 of-band information is needed to interpret the data properly, 739 including but not necessarily limited to, knowledge of the 740 boundaries between successive frames and knowledge of the 741 transport mechanism. Note that media types of this sort cannot 742 simply be stored in a file or transported as a simple stream of 743 octets; therefore, such media types are unsuitable for use in many 744 traditional protocols. A commonly used transport with framed 745 encoding is the Real-time Transport Protocol, RTP. Additional 746 rules for framed encodings defined for transport using RTP are 747 given in [RFC4855]. 749 Additional restrictions on 7bit and 8bit text are given in Section 750 4.1.1 of [RFC2046]. 752 4.9. Usage and Implementation Non-requirements 754 In the asynchronous mail environment, where information on the 755 capabilities of the remote mail agent is frequently not available to 756 the sender, maximum interoperability is attained by restricting the 757 media types used to those "common" formats expected to be widely 758 implemented. This was asserted in the past as a reason to limit the 759 number of possible media types, and resulted in a registration 760 process with a significant hurdle and delay for those registering 761 media types. 763 However, the need for "common" media types does not require limiting 764 the registration of new media types. If a limited set of media types 765 is recommended for a particular application, that should be asserted 766 by a separate applicability statement specific for the application 767 and/or environment. 769 Therefore, universal support and implementation of a media type is 770 NOT a requirement for registration. However, if a media type is 771 explicitly intended for limited use, this MUST be noted in its 772 registration. The "Restrictions on Usage" field is provided for this 773 purpose. 775 4.10. Publication Requirements 777 Media types registered in the standards tree by the IETF itself MUST 778 be published as RFCs. RFC publication of vendor and personal media 779 type registrations is allowed but not required. In all cases the 780 IANA will retain copies of all media type registrations and "publish" 781 them as part of the media types registration tree itself. 783 As stated previously, standards tree registrations for media types 784 defined in documents produced by other standards bodies MUST be 785 described by a formal standards specification produced by that body. 786 Additionally, any copyright on the registration template MUST allow 787 the IANA to copy it into the IANA registry. 789 Other than IETF registrations in the standards tree, the registration 790 of a media type does not imply endorsement, approval, or 791 recommendation by the IANA or the IETF or even certification that the 792 specification is adequate. To become an Internet Standard, a 793 protocol or data object must go through the IETF standards process. 794 While it provides additional assurances when it is appropriate, this 795 is too difficult and too lengthy a process for the convenient 796 registration of media types. 798 The standards tree exists for media types that do require a 799 substantive review and approval process in a recognized standards 800 body. The vendor and personal trees exist for those media types that 801 do not require such a process. It is expected that applicability 802 statements for particular applications will be published from time to 803 time in the IETF, recommending implementation of, and support for, 804 media types that have proven particularly useful in those contexts. 806 As discussed above, registration of a top-level type requires 807 Standards Action in the IETF and, hence, the publication of a RFC on 808 the Standards Track. 810 4.11. Fragment Identifier Requirements 812 Media type registrations can specify how applications should 813 interpret fragment identifiers [RFC3986] associated with the media 814 type. 816 Media types are encouraged to adopt fragment identifier schemes that 817 are used with semantically similar media types. In particular, media 818 types that use a named structured syntax with a registered "+suffix" 819 MUST follow whatever fragment identifier rules are given in the 820 structured syntax suffix registration. 822 4.12. Additional Information 824 Various sorts of optional information SHOULD be included in the 825 specification of a media type if it is available: 827 o Magic number(s) (length, octet values). Magic numbers are byte 828 sequences that are always present at a given place in the file and 829 thus can be used to identify entities as being of a given media 830 type. 832 o File name extension(s) commonly used on one or more platforms to 833 indicate that some file contains a given media type. 835 o Mac OS File Type code(s) (4 octets) used to label files containing 836 a given media type. Some discussion of Macintosh file type codes 837 and their purpose can be found in [MacOSFileTypes]. 839 In the case of a registration in the standards tree, this additional 840 information MAY be provided in the formal specification of the media 841 type. It is suggested that this be done by incorporating the IANA 842 media type registration form into the specification itself. 844 5. Media Type Registration Procedures 846 The media type registration procedure is not a formal standards 847 process, but rather an administrative procedure intended to allow 848 community comment and sanity checking without excessive time delay. 850 The normal IETF processes should be followed for all IETF 851 registrations in the standards tree. The posting of an Internet 852 Draft is a necessary first step, followed by posting to the 853 media-types@iana.org list as discussed below. 855 5.1. Preliminary Community Review 857 Notice of a potential media type registration in the standards tree 858 SHOULD be sent to the media-types@iana.org mailing list for review. 859 This mailing list has been established for the purpose of reviewing 860 proposed media and access types. Registrations in other trees MAY be 861 sent to the list for review as well; doing so is entirely OPTIONAL, 862 but is strongly encouraged. 864 The intent of the public posting to this list is to solicit comments 865 and feedback on the choice of type/subtype name, the unambiguity of 866 the references with respect to versions and external profiling 867 information, and a review of any interoperability or security 868 considerations. The submitter may submit a revised registration 869 proposal or abandon the registration completely and at any time. 871 5.2. Submit request to IANA 873 Media types registered in the standards tree by the IETF itself MUST 874 be reviewed and approved by the IESG as part of the normal standards 875 process. Standards tree registrations by recognized standards bodies 876 as well as registrations in the vendor and personal tree should be 877 submitted directly to the IANA, unless other arrangements were made 878 as part of a liaison agreement. In either case posting the 879 registration to the media-types@iana.org list for review prior to 880 submission is strongly encouraged. 882 Registration requests can be sent to iana@iana.org. A web form for 883 registration requests is also available: 885 http://www.iana.org/cgi-bin/mediatypes.pl 887 5.2.1. Provisional Registrations 889 Standardization processes often take considerable time to complete. 890 In order to facilitate prototyping and testing it is often helpful to 891 assign identifiers, including but not limited to media types, early 892 in the process. This way identifiers used during standards 893 development can remain unchanged once the process is complete and 894 implementations and documentation do not have to be updated. 896 Accordingly, a provisional registration process is provided to 897 support early assignment of media type names. A provisional 898 registration MAY be submitted to IANA for standards tree types. The 899 only required fields in such registrations are the media type name 900 and contact information (including the standards body name). 902 Upon receipt of a provisional registration, IANA will check the name 903 and contact information, then publish the registration in a separate 904 provisional registration list. 906 Provisional registrations MAY be updated or abandoned at any time. 908 5.3. Review and Approval 910 With the exception of provisional standards tree registrations, 911 registrations submitted to the IANA will be passed on to the media 912 types reviewer. The media types reviewer, who is appointed by the 913 IETF Applications Area Director(s), will review the registration to 914 make sure it meets the requirements set forth in this document. 915 Registrations that do not meet these requirements will be returned to 916 the submitter for revision. 918 Decisions made by the media types reviewer may be appealed to the 919 IESG using the procedure specified in section 6.5.4 of [RFC2026]. 921 Once a media type registration has passed review, the IANA will 922 register the media type and make the media type registration 923 available to the community. 925 In the case of standards tree registrations from other standards 926 bodies IANA will also check that the submitter is in fact a 927 recognized standards body. If the submitter is not currently 928 recognized as such the IESG will be asked to confirm their status. 929 Recognition from the IESG MUST be obtained before a standards tree 930 registration can proceed. 932 5.4. Comments on Media Type Registrations 934 Comments on registered media types may be submitted by members of the 935 community to the IANA at iana@iana.org. These comments will be 936 reviewed by the media types reviewer and then passed on to the 937 "owner" of the media type if possible. Submitters of comments may 938 request that their comment be attached to the media type registration 939 itself, and if the IANA approves of this, the comment will be made 940 accessible in conjunction with the type registration. 942 5.5. Location of Registered Media Type List 944 Media type registrations are listed by the IANA at: 946 http://www.iana.org/assignments/media-types/ 948 5.6. Change Procedures 950 Once a media type has been published by the IANA, the owner may 951 request a change to its definition. The descriptions of the 952 different registration trees above designate the "owners" of each 953 type of registration. The same procedure that would be appropriate 954 for the original registration request is used to process a change 955 request. 957 Significant changes to a media type's definition should be requested 958 only when there are serious omissions or errors in the published 959 specification. When review is required, a change request may be 960 denied if it renders entities that were valid under the previous 961 definition invalid under the new definition. 963 The owner of a media type may pass responsibility to another person 964 or agency by informing the IANA; this can be done without discussion 965 or review. 967 The IESG may reassign responsibility for a media type. The most 968 common case of this will be to enable changes to be made to types 969 where the author of the registration has died, moved out of contact 970 or is otherwise unable to make changes that are important to the 971 community. 973 Media type registrations may not be deleted; media types that are no 974 longer believed appropriate for use can be declared OBSOLETE by a 975 change to their "intended use" field; such media types will be 976 clearly marked in the lists published by the IANA. 978 5.7. Registration Template 980 Type name: 982 Subtype name: 984 Required parameters: 986 Optional parameters: 988 Encoding considerations: 990 Security considerations: 992 Interoperability considerations: 994 Published specification: 996 Applications that use this media type: 998 Fragment identifier considerations: 1000 Additional information: 1002 Deprecated alias names for this type: 1003 Magic number(s): 1004 File extension(s): 1005 Macintosh file type code(s): 1007 Person & email address to contact for further information: 1009 Intended usage: 1011 (One of COMMON, LIMITED USE or OBSOLETE.) 1013 Restrictions on usage: 1015 (Any restrictions on where the media type can be used go here.) 1017 Author: 1019 Change controller: 1021 Provisional registration? (standards tree only): 1023 (Any other information that the author deems interesting may be 1024 added below this line.) 1025 "N/A", written exactly that way, can be used in any field if desired 1026 to emphasize the fact that it does not apply or that the question was 1027 not omitted by accident. Do not use 'none' or other words that could 1028 be mistaken for a response. 1030 Limited use media types should also note in the applications list 1031 whether or not that list is exhaustive. 1033 6. Structured Syntax Suffix Registration Procedures 1035 Someone wishing to define a "+suffix" name for a structured syntax 1036 for use with a new media type registration SHOULD: 1038 1. Check IANA's registry of media type name suffixes to see whether 1039 or not there is already an entry for that well-defined structured 1040 syntax. 1042 2. If there is no entry for their suffix scheme, fill out the 1043 template (specified in Section 6.2) and include that with the 1044 media type registration. The template may be contained in an 1045 Internet Draft, alone or as part of some other protocol 1046 specification. The template may also be submitted in some other 1047 form (as part of another document or as a stand-alone document), 1048 but the contents will be treated as an "IETF Contribution" under 1049 the guidelines of BCP 78 [RFC5378]. 1051 3. Send a copy of the template or a pointer to the containing 1052 document (with specific reference to the section with the 1053 template) to the mailing list media-types@iana.org, requesting 1054 review. This may be combined with a request to review the media 1055 type registration. Allow a reasonable time for discussion and 1056 comments. 1058 4. Respond to review comments and make revisions to the proposed 1059 registration as needed to bring it into line with the guidelines 1060 given in this document. 1062 5. Submit the (possibly updated) registration template (or pointer 1063 to the document containing it) to IANA at iana@iana.org. 1065 Upon receipt of a structured syntax suffix registration request, 1067 1. IANA checks the submission for completeness; if sections are 1068 missing or citations are not correct, IANA rejects the 1069 registration request. 1071 2. IANA checks the current registry for an entry with the same name; 1072 if such a registry exists, IANA rejects the registration request. 1074 3. IANA requests Expert Review of the registration request against 1075 the corresponding guidelines. 1077 4. The Designated Expert may request additional review or 1078 discussion, as necessary. 1080 5. If Expert Review recommends registration, IANA adds the 1081 registration to the appropriate registry. 1083 6.1. Change Procedures 1085 Registrations may be updated in each registry by the same mechanism 1086 as required for an initial registration. In cases where the original 1087 definition of the scheme is contained in an IESG-approved document, 1088 update of the specification also requires IESG approval. 1090 6.2. Structured Syntax Suffix Registration Template 1092 This template describes the fields that must be supplied in a 1093 structured syntax suffix registration request: 1095 Name 1096 Full name of the well-defined structured syntax. 1098 +suffix 1099 Suffix used to indicate conformance to the syntax. 1101 References 1102 Include full citations for all specifications necessary to 1103 understand the structured syntax. 1105 Encoding considerations 1106 General guidance regarding encoding considerations for any type 1107 employing this syntax should be given here. The same requirements 1108 for media type encoding considerations given in Section 4.8 apply 1109 here. 1111 Interoperability considerations 1112 Any issues regarding the interoperable use of types employing this 1113 structured syntax should be given here. Examples would include 1114 the existence of incompatible versions of the syntax, issues 1115 combining certain charsets with the syntax, or incompatibilities 1116 with other types or protocols. 1118 Fragment identifier considerations 1119 Generic processing of fragment identifiers for any type employing 1120 this syntax should be described here. 1122 Security considerations 1123 Security considerations shared by media types employing this 1124 structured syntax must be specified here. The same requirements 1125 for media type security considerations given in Section 4.6 apply 1126 here, with the exception that option of not assessing the security 1127 considerations is not available for suffix registrations. 1129 Contact 1130 Person (including contact information) to contact for further 1131 information. 1133 Author/Change controller. 1134 Person (including contact information) authorized to change this 1135 suffix registration. 1137 7. Security Considerations 1139 Security requirements for media type registrations are discussed in 1140 Section 4.6. 1142 8. IANA Considerations 1144 The purpose of this document is to define IANA registries for media 1145 types and structured syntax suffixes as well as the procedures for 1146 managing these registries. Additionally, this document requires IANA 1147 to maintain a list of IESG-recognized standards bodies who are 1148 allowed to register types in the standards tree. 1150 This document also creates a new registry for structured syntax 1151 names: 1153 o The name is the "Structured Syntax Suffix" registry. 1155 o The registration process is specified in Section 6. 1157 o The information required for a registry entry as well as the entry 1158 format are specified in Section 6.2. 1160 o The initial content of the registry is specified in 1161 [I-D.appsawg-media-type-suffix-regs]. 1163 Finally, this document calls for the creation of a new email address, 1164 media-types@iana.org, for the media type review list, which replaces 1165 the ietf-types@iana.org address specified in RFC 4288. 1166 ietf-types@iana.org should be retained as an alias. 1168 9. Acknowledgements 1170 The current authors would like to acknowledge their debt to the late 1171 Dr. Jon Postel, whose general model of IANA registration procedures 1172 and specific contributions shaped the predecessors of this document 1173 [RFC2048] [RFC4288]. We hope that the current version is one with 1174 which he would have agreed but, as it is impossible to verify that 1175 agreement, we have regretfully removed his name as a co-author. 1177 Bjoern Hoehrmann, Barry Leiba, Murray Kucherawy, Alexey Melnikov, S. 1178 Moonesamy, Peter Saint-Andre, and Jeni Tennison provided many helpful 1179 review comments and suggestions. 1181 10. References 1183 10.1. Normative References 1185 [I-D.appsawg-media-type-suffix-regs] 1186 Hansen, T., "Additional Media Type Structured Syntax 1187 Suffixes", draft-appsawg-media-type-suffix-regs-00 (work 1188 in progress), April 2012. 1190 [I-D.ietf-appsawg-mime-default-charset] 1191 Melnikov, A. and J. Reschke, "Update to MIME regarding 1192 Charset Parameter Handling in Textual Media Types", 1193 draft-ietf-appsawg-mime-default-charset-01 (work in 1194 progress), March 2012. 1196 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1197 Extensions (MIME) Part One: Format of Internet Message 1198 Bodies", RFC 2045, November 1996. 1200 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1201 Extensions (MIME) Part Two: Media Types", RFC 2046, 1202 November 1996. 1204 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1205 Requirement Levels", BCP 14, RFC 2119, March 1997. 1207 [RFC2978] Freed, N. and J. Postel, "IANA Charset Registration 1208 Procedures", BCP 19, RFC 2978, October 2000. 1210 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 1211 Types", RFC 3023, January 2001. 1213 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 1214 10646", STD 63, RFC 3629, November 2003. 1216 [RFC3979] Bradner, S., "Intellectual Property Rights in IETF 1217 Technology", BCP 79, RFC 3979, March 2005. 1219 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1220 Resource Identifier (URI): Generic Syntax", STD 66, 1221 RFC 3986, January 2005. 1223 [RFC4855] Casner, S., "Media Type Registration of RTP Payload 1224 Formats", RFC 4855, February 2007. 1226 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1227 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1228 May 2008. 1230 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 1231 Specifications: ABNF", STD 68, RFC 5234, January 2008. 1233 [RFC5378] Bradner, S. and J. Contreras, "Rights Contributors Provide 1234 to the IETF Trust", BCP 78, RFC 5378, November 2008. 1236 [RFC6532] Yang, A., Steel, S., and N. Freed, "Internationalized 1237 Email Headers", RFC 6532, January 2012. 1239 10.2. Informative References 1241 [I-D.ietf-appsawg-xdash] 1242 Saint-Andre, P. and D. Crocker, "Deprecating the X- Prefix 1243 and Similar Constructs in Application Protocols", 1244 draft-ietf-appsawg-xdash-05 (work in progress), 1245 April 2012. 1247 [MacOSFileTypes] 1248 Apple Computer, Inc., "Mac OS: File Type and Creator 1249 Codes, and File Formats", Apple Knowledge Base Article 1250 55381, June 1993, 1251 . 1253 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 1254 3", BCP 9, RFC 2026, October 1996. 1256 [RFC2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose 1257 Internet Mail Extensions (MIME) Part Four: Registration 1258 Procedures", BCP 13, RFC 2048, November 1996. 1260 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 1261 Word Extensions: 1262 Character Sets, Languages, and Continuations", RFC 2231, 1263 November 1997. 1265 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 1266 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 1267 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 1269 [RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and 1270 Registration Procedures", BCP 13, RFC 4288, December 2005. 1272 Appendix A. Grandfathered Media Types 1274 A number of media types with unfaceted names, registered prior to 1275 1996, would, if registered under the guidelines in this document, be 1276 given a faceted name and placed into either the vendor or personal 1277 trees. Reregistration of those types to reflect the appropriate 1278 trees is encouraged but not required. Ownership and change control 1279 principles outlined in this document apply to those types as if they 1280 had been registered in the trees described above. 1282 From time to time there may also be cases where a media type with an 1283 unfaceted name has been widely deployed without being registered. 1284 (Note that this includes types with names beginning with the "x-" 1285 prefix.) If possible such types SHOULD be reregistered with a proper 1286 faceted name. However, if this is not possible the type can, subject 1287 to approval by both the media types reviewer and the IESG, be 1288 registered in the proper tree with its unfaceted name. 1290 Appendix B. Changes Since RFC 4288 1292 o Suffixes to indicate the use of a particular structured syntax are 1293 now fully specified and a suffix registration process has been 1294 defined. 1296 o Registration of widely deployed unregistered unfaceted type names 1297 in the vendor or personal trees is now allowed, subject to 1298 approval by the media types reviewer and the IESG. 1300 o The standards tree registration process has been revised to 1301 include Expert Review and generalized to address cases like media 1302 types in non-IETF stream documents. 1304 o A field for fragment identifiers has been added to the 1305 registration template and brief directions for specifying fragment 1306 identifiers have been added. 1308 o The specification requirements for personal tree registrations 1309 have been changed to be the same as those for the vendor tree. 1310 The text has been changed to encourage (but not require) 1311 specification availability. 1313 o The definition of additional trees has been clarified to state 1314 that an IETF Standards Action is required. 1316 o Widely deployed types with "x-" names can now be registered as an 1317 exception in the vendor tree. 1319 o The requirements on changes to registrations have been loosened so 1320 minor changes are easier to make. 1322 o The registration process has been completely restructured so that 1323 with the exception of IETF-generated types in the standards tree, 1324 all requests are processed by IANA and not the IESG. 1326 o A provisional registration process has been added for early 1327 assignment of types in the standards tree. 1329 o Many editorial changes have been made throughout the document to 1330 make the requirements and processes it describes clearer and 1331 easier to follow. 1333 o The ability to specify a list of deprecated aliases for a media 1334 type has been added. 1336 o Types with names beginning with "x-" are no longer considered to 1337 be members of the unregistered "x." tree. As with any unfaceted 1338 type, special procedures have been added to allow registration of 1339 such types in an appropriate tree. 1341 o Changes to a type registered by a third party may now be made by 1342 the designated change controller even if that isn't the vendor or 1343 organization that created the type. However, the vendor or 1344 organization may elect to assert ownership and change controller 1345 over the type at any time. 1347 o Limited use media types are now asked to note whether or not the 1348 supplied list of applications employing the media type is 1349 exhaustive. 1351 o The ABNF for media type names has been further restricted to 1352 require that names begin with an alphanumeric character. 1354 o Mailing list review is no longer required prior to registration of 1355 media types. Additionally, the address associated with the media 1356 type review mailing list has been changed to media-types@iana.org. 1358 Authors' Addresses 1360 Ned Freed 1361 Oracle 1362 800 Royal Oaks 1363 Monrovia, CA 91016-6347 1364 USA 1366 Email: ned+ietf@mrochek.com 1368 John C. Klensin 1369 1770 Massachusetts Ave, #322 1370 Cambridge, MA 02140 1371 USA 1373 Email: john+ietf@jck.com 1375 Tony Hansen 1376 AT&T Laboratories 1377 200 Laurel Ave. 1378 Middletown, NJ 07748 1379 USA 1381 Email: tony+mtsuffix@maillennium.att.com