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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: October 17, 2012 T. Hansen 7 AT&T Laboratories 8 April 15, 2012 10 Media Type Specifications and Registration Procedures 11 draft-ietf-appsawg-media-type-regs-05 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 October 17, 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. Additional Information . . . . . . . . . . . . . . . . . . 18 84 5. Media Type Registration Procedures . . . . . . . . . . . . . . 19 85 5.1. Preliminary Community Review . . . . . . . . . . . . . . . 19 86 5.2. Submit request to IANA . . . . . . . . . . . . . . . . . . 19 87 5.2.1. Provisional Registrations . . . . . . . . . . . . . . 20 88 5.3. Review and Approval . . . . . . . . . . . . . . . . . . . 20 89 5.4. Comments on Media Type Registrations . . . . . . . . . . . 21 90 5.5. Location of Registered Media Type List . . . . . . . . . . 21 91 5.6. Change Procedures . . . . . . . . . . . . . . . . . . . . 21 92 5.7. 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. 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 IETF Consensus RFC, which can be on 204 the Standards Track, a BCP, Informational, or Experimental. In the 205 case of registrations for other recognized standards bodies, the 206 format MUST be described by a formal standards specification produced 207 by that body. 209 Registrations published in non-IETF RFC streams are allowed and 210 require IESG approval. 212 Standards-tree registration RFCs can either be standalone 213 "registration only" RFCs, or they can be incorporated into a more 214 general specification of some sort. 216 Media types in the standards tree are normally denoted by names that 217 are not explicitly faceted, i.e., do not contain period (".", full 218 stop) characters. 220 The "owner" of a media type registration in the standards tree is 221 assumed to be the standards body itself. Modification or alteration 222 of the specification uses the same level of processing (e.g., a 223 registration submitted on Standards Track can be revised in another 224 Standards Track RFC, but cannot be revised in an Informational RFC) 225 required for the initial registration. 227 Standards-tree registrations from recognized standards bodies may be 228 submitted directly to the IANA, where they will undergo Expert Review 229 [RFC5226] prior to approval. In this case, the Expert Reviewer(s) 230 will, among other things, ensure that the required specification 231 provides adequate documentation. 233 3.2. Vendor Tree 235 The vendor tree is used for media types associated with publicly 236 available products. "Vendor" and "producer" are construed very 237 broadly in this context and are considered equivalent. Note that 238 industry consortia as well as non-commercial entities that do not 239 qualify as recognized standards bodies can quite appropriately 240 register media types in the vendor tree. 242 A registration may be placed in the vendor tree by anyone who needs 243 to interchange files associated with some product or set of products. 244 However, the registration properly belongs to the vendor or 245 organization producing the software that employs the type being 246 registered, and that vendor or organization can at any time elect to 247 assert ownership of a registration done by a third party in order to 248 correct or update it. See Section 5.6 for additional information. 250 When a third party registers a type on behalf of someone else both 251 entities SHOULD be noted in the Change Controller field in the 252 registration. One possible format for this would be "Foo, on behalf 253 of Bar". 255 Registrations in the vendor tree will be distinguished by the leading 256 facet "vnd.". That may be followed, at the discretion of the 257 registrant, by either a media subtype name from a well-known producer 258 (e.g., "vnd.mudpie") or by an IANA-approved designation of the 259 producer's name that is followed by a media type or product 260 designation (e.g., vnd.bigcompany.funnypictures). 262 While public exposure and review of media types to be registered in 263 the vendor tree is not required, using the media-types@iana.org 264 mailing list for review is encouraged to improve the quality of those 265 specifications. Registrations in the vendor tree may be submitted 266 directly to the IANA, where they will undergo Expert Review [RFC5226] 267 prior to approval. 269 3.3. Personal or Vanity Tree 271 Registrations for media types created experimentally or as part of 272 products that are not distributed commercially may be registered in 273 the personal or vanity tree. The registrations are distinguished by 274 the leading facet "prs.". 276 The owner of "personal" registrations and associated specifications 277 is the person or entity making the registration, or one to whom 278 responsibility has been transferred as described below. 280 While public exposure and review of media types to be registered in 281 the personal tree is not required, using the media-types@iana.org 282 mailing list (see Section 5.1) for review is encouraged to improve 283 the quality of those specifications. Registrations in the personal 284 tree may be submitted directly to the IANA, where they will undergo 285 Expert Review [RFC5226] prior to approval. 287 3.4. Unregistered x. Tree 289 Subtype names with "x." as the first facet may be used for types 290 intended exclusively for use in private, local environments. Types 291 in this tree cannot be registered and are intended for use only with 292 the active agreement of the parties exchanging them. 294 However, with the simplified registration procedures described above 295 for vendor and personal trees, it should rarely, if ever, be 296 necessary to use unregistered types. Therefore, use of types in the 297 "x." tree is strongly discouraged. 299 Note that types with names beginning with "x-" are no longer 300 considered to members of this tree (see [I-D.ietf-appsawg-xdash]). 301 Also note that if a generally useful and widely deployed type 302 incorrectly ends up with an "x-" name prefix, it MAY be registered 303 using its current name in an alternate tree by following the 304 procedure defined in Appendix A. 306 3.5. Additional Registration Trees 308 From time to time and as required by the community, new top-level 309 registration trees may be created by IETF Standards Action. It is 310 explicitly assumed that these trees may be created for external 311 registration and management by well-known permanent bodies; for 312 example, scientific societies may register media types specific to 313 the sciences they cover. In general, the quality of review of 314 specifications for one of these additional registration trees is 315 expected to be equivalent to registrations in the standards tree by a 316 recognized Standards Development Organization. When the IETF 317 performs such review, it needs to consider the greater expertise of 318 the requesting body with respect to the subject media type. 320 4. Registration Requirements 322 Media type registrations are all expected to conform to various 323 requirements laid out in the following sections. Note that 324 requirement specifics sometimes vary depending on the registration 325 tree, again as detailed in the following sections. 327 4.1. Functionality Requirement 329 Media types MUST function as an actual media format. Registration of 330 things that are better thought of as a transfer encoding, as a 331 charset, or as a collection of separate entities of another type, is 332 not allowed. For example, although applications exist to decode the 333 base64 transfer encoding [RFC2045], base64 cannot be registered as a 334 media type. 336 This requirement applies regardless of the registration tree 337 involved. 339 4.2. Naming Requirements 341 All registered media types MUST be assigned type and subtype names. 342 The combination of these names serves to uniquely identify the media 343 type, and the format of the subtype name identifies the registration 344 tree. Both type and subtype names are case-insensitive. 346 Type and subtype names MUST conform to the following ABNF: 348 type-name = restricted-name 349 subtype-name = restricted-name 351 restricted-name = restricted name-first *126restricted-name-chars 352 restricted-name-first = ALPHA / DIGIT 353 restricted-name-chars = ALPHA / DIGIT / "!" / 354 "#" / "$" / "&" / "." / 355 "+" / "-" / "^" / "_" 357 Note that this syntax is somewhat more restrictive than what is 358 allowed by the ABNF in section 5.1 of [RFC2045] or section 4.2 of 359 [RFC4288]. Also note that while this syntax allows names of up to 360 127 characters, implementation limits may make such long names 361 problematic. For this reason the components of names SHOULD be 362 limited to 64 characters. 364 Although the name syntax treats "+" as equivalent to any other 365 character, it is used in media type names to introduce a structured 366 syntax specifier suffix. Structured syntax suffix requirements are 367 specified in Section 4.2.8. 369 While it is possible for a given media type to be assigned additional 370 names, the use of different names to identify the same media type is 371 discouraged. 373 These requirements apply regardless of the registration tree 374 involved. 376 The choice of top-level type name MUST take into account the nature 377 of media type involved. New subtypes of top-level types MUST conform 378 to the restrictions of the top-level type, if any. The following 379 sections describe each of the initial set of top-level types and 380 their associated restrictions. Additionally, various protocols, 381 including but not limited to HTTP and MIME, MAY impose additional 382 restrictions on the media types they can transport. (See [RFC2046] 383 for additional information on the restrictions MIME imposes.) 385 4.2.1. Text Media Types 387 The "text" media type is intended for sending material that is 388 principally textual in form. 390 Many subtypes of text, notably including the subtype "text/plain", 391 which is a generic subtype for plain text defined in [RFC2046], 392 define a "charset" parameter. If a "charset" parameter is defined 393 for a particular subtype of text, it MUST be used to specify a 394 charset name defined in accordance to the procedures laid out in 395 [RFC2978]. 397 As specified in [I-D.ietf-appsawg-mime-default-charset], a "charset" 398 parameter SHOULD NOT be specified when charset information is 399 transported inside the payload (e.g., as in "text/xml"). 401 If a "charset" parameter is specified, it SHOULD be a required 402 parameter, eliminating the options of specifying a default value. If 403 there is a strong reason for the parameter to be optional despite 404 this advice, each subtype MAY specify its own default value, or 405 alternately, it MAY specify that there is no default value. Finally, 406 the "UTF-8" charset [RFC3629] SHOULD be selected as the default. See 407 [I-D.ietf-appsawg-mime-default-charset] for additional information on 408 the use of "charset" parameters in conjunction with subtypes of text. 410 Plain text does not provide for or allow formatting commands, font 411 attribute specifications, processing instructions, interpretation 412 directives, or content markup. Plain text is seen simply as a linear 413 sequence of characters, possibly interrupted by line breaks or page 414 breaks. Plain text MAY allow the stacking of several characters in 415 the same position in the text. Plain text in scripts like Arabic and 416 Hebrew may also include facilities that allow the arbitrary mixing of 417 text segments with different writing directions. 419 Beyond plain text, there are many formats for representing what might 420 be known as "rich text". An interesting characteristic of many such 421 representations is that they are to some extent readable even without 422 the software that interprets them. It is useful to distinguish them, 423 at the highest level, from such unreadable data as images, audio, or 424 text represented in an unreadable form. In the absence of 425 appropriate interpretation software, it is reasonable to present 426 subtypes of "text" to the user, while it is not reasonable to do so 427 with most non-textual data. Such formatted textual data should be 428 represented using subtypes of "text". 430 4.2.2. Image Media Types 432 A media type of "image" indicates that the content specifies one or 433 more individual images. The subtype names the specific image format. 435 4.2.3. Audio Media Types 437 A media type of "audio" indicates that the content contains audio 438 data. 440 4.2.4. Video Media Types 442 A media type of "video" indicates that the content specifies a time- 443 varying-picture image, possibly with color and coordinated sound. 444 The term 'video' is used in its most generic sense, rather than with 445 reference to any particular technology or format, and is not meant to 446 preclude subtypes such as animated drawings encoded compactly. 448 Note that although in general this document strongly discourages the 449 mixing of multiple media in a single body, it is recognized that many 450 so-called video formats include a representation for synchronized 451 audio and/or text, and this is explicitly permitted for subtypes of 452 "video". 454 4.2.5. Application Media Types 456 The "application" media type is to be used for discrete data that do 457 not fit in any of the media types, and particularly for data to be 458 processed by some type of application program. This is information 459 that must be processed by an application before it is viewable or 460 usable by a user. Expected uses for the "application" media type 461 include but are not limited to file transfer, spreadsheets, 462 presentations, scheduling data, and languages for "active" 463 (computational) material. (The last, in particular, can pose 464 security problems that must be understood by implementors, and that 465 are considered in detail in the discussion of the "application/ 466 postscript" media type in [RFC2046].) 468 For example, a meeting scheduler might define a standard 469 representation for information about proposed meeting dates. An 470 intelligent user agent would use this information to conduct a dialog 471 with the user, and might then send additional material based on that 472 dialog. More generally, there have been several "active" languages 473 developed in which programs in a suitably specialized language are 474 transported to a remote location and automatically run in the 475 recipient's environment. Such applications may be defined as 476 subtypes of the "application" media type. 478 The subtype of "application" will often either be the name or include 479 part of the name of the application for which the data are intended. 480 This does not mean, however, that any application program name may 481 simply be used freely as a subtype of "application"; the subtype 482 needs to be registered. 484 4.2.6. Multipart and Message Media Types 486 Multipart and message are composite types, that is, they provide a 487 means of encapsulating zero or more objects, each labeled with its 488 own media type. 490 All subtypes of multipart and message MUST conform to the syntax 491 rules and other requirements specified in [RFC2046] and amended by 492 Section 3.5 of [RFC6532]. 494 4.2.7. Additional Top-level Types 496 In some cases a new media type may not "fit" under any currently 497 defined top-level content type. Such cases are expected to be quite 498 rare. However, if such a case does arise a new top-level type can be 499 defined to accommodate it. Such a definition MUST be done via 500 standards-track RFC; no other mechanism can be used to define 501 additional top-level content types. 503 4.2.8. Structured Syntax Name Suffixes 505 [RFC3023] defined the first such augmentation to the media type 506 definition to additionally specify the underlying structure of that 507 media type. To quote: 509 This document also standardizes a convention (using the suffix 510 '+xml') for naming media types ... when those media types 511 represent XML MIME (Multipurpose Internet Mail Extensions) 512 entities. 514 That is, it specified a suffix (in that case, "+xml") to be appended 515 to the base media type name. 517 Since this was published, the de facto practice has arisen for using 518 this suffix convention for other well-known structuring syntaxes. In 519 particular, media types have been registered with suffixes such as 520 "+der", "+fastinfoset" and "+json". This specification formalizes 521 this practice and sets up a registry for structured type name 522 suffixes. 524 The primary guideline for whether a structured type name suffix 525 should be registrable is that it be described by a readily-available 526 description, preferably within a document published by an established 527 standards organization, and for which there's a reference that can be 528 used in a References section of an RFC. 530 Media types that make use of a named structured syntax SHOULD use the 531 appropriate registered "+suffix" for that structured syntax when they 532 are registered. By the same token, media types MUST NOT be given 533 names incorporating suffixes for structured syntaxes they do not 534 actually employ. "+suffix" constructs for as-yet unregistered 535 structured syntaxes should be used with care, given the possibility 536 of conflicts with future suffix definitions. 538 4.2.9. Deprecated Aliases 540 In some cases a single media type may have been widely deployed prior 541 to registration under multiple names. In such cases a preferred name 542 MUST be chosen for the media type and applications MUST use this to 543 be compliant with the type's registration. However, a list of 544 deprecated aliases the type is known by MAY be supplied as additional 545 information in order to assist application in processing the media 546 type properly. 548 4.3. Parameter Requirements 550 Media types MAY elect to use one or more media type parameters, or 551 some parameters may be automatically made available to the media type 552 by virtue of being a subtype of a content type that defines a set of 553 parameters applicable to any of its subtypes. In either case, the 554 names, values, and meanings of any parameters MUST be fully specified 555 when a media type is registered in the standards tree, and SHOULD be 556 specified as completely as possible when media types are registered 557 in the vendor or personal trees. 559 Parameter names have the syntax as media type names and values: 561 parameter-name = restricted-name 563 Note that this syntax is somewhat more restrictive than what is 564 allowed by the ABNF in [RFC2045] and amended by [RFC2231]. 566 Parameter names are case-insensitive and no meaning is attached to 567 the order in which they appear. It is an error for a specific 568 parameter to be specified more than once. 570 There is no defined syntax for parameter values. Therefore 571 registrations MUST specify parameter value syntax. Additionally, 572 some transports impose restrictions on parameter value syntax, so 573 care should be taken to limit the use of potentially problematic 574 syntaxes; e.g., pure binary valued parameters, while permitted in 575 some protocols, probably should be avoided. 577 New parameters SHOULD NOT be defined as a way to introduce new 578 functionality in types registered in the standards tree, although new 579 parameters MAY be added to convey additional information that does 580 not otherwise change existing functionality. An example of this 581 would be a "revision" parameter to indicate a revision level of an 582 external specification such as JPEG. Similar behavior is encouraged 583 for media types registered in the vendor or personal trees, but is 584 not required. 586 4.4. Canonicalization and Format Requirements 588 All registered media types MUST employ a single, canonical data 589 format, regardless of registration tree. 591 A precise and openly available specification of the format of each 592 media type MUST exist for all types registered in the standards tree 593 and MUST at a minimum be referenced by, if it is not actually 594 included in, the media type registration proposal itself. 596 The specifications of format and processing particulars may or may 597 not be publicly available for media types registered in the vendor 598 and personal trees, and such registrations are explicitly permitted 599 to limit the information in the registration to which software and 600 version produce or process such media types. As such, references to 601 or inclusion of format specifications in registrations is encouraged 602 but not required. Note, however, that the public availability of a 603 meaningful specification will often make the difference between 604 simply having a name reserved so that there are no conflicts with 605 other uses and having the potential for other implementations of the 606 media type and useful interoperation with them. 608 Some media types involve the use of patented technology. The 609 registration of media types involving patented technology is 610 specifically permitted. However, the restrictions set forth in 611 [RFC3979] and [RFC5378] on the use of patented technology in IETF 612 standards-track protocols must be respected when the specification of 613 a media type is part of a standards-track protocol. In addition, 614 other standards bodies making use of the standards tree may have 615 their own rules regarding intellectual property that must be observed 616 in their registrations. 618 IPR disclosures for registrations in the vendor and personal tree are 619 encouraged but not required. 621 4.5. Interchange Recommendations 623 Media types SHOULD interoperate across as many systems and 624 applications as possible. However, some media types will inevitably 625 have problems interoperating across different platforms. Problems 626 with different versions, byte ordering, and specifics of gateway 627 handling can and will arise. 629 Universal interoperability of media types is not required, but known 630 interoperability issues SHOULD be identified whenever possible. 631 Publication of a media type does not require an exhaustive review of 632 interoperability, and the interoperability considerations section is 633 subject to continuing evaluation. 635 These recommendations in this subsection apply regardless of the 636 registration tree involved. 638 4.6. Security Requirements 640 An analysis of security issues MUST be done for all types registered 641 in the standards tree. A similar analysis for media types registered 642 in the vendor or personal trees is encouraged but not required. 643 However, regardless of what security analysis has or has not been 644 done, all descriptions of security issues MUST be as accurate as 645 possible regardless of registration tree. In particular, a statement 646 that there are "no security issues associated with this type" MUST 647 NOT be confused with "the security issues associates with this type 648 have not been assessed". 650 There is absolutely no requirement that media types registered in any 651 tree be secure or completely free from risks. Nevertheless, all 652 known security risks MUST be identified in the registration of a 653 media type, again regardless of registration tree. 655 The security considerations section of all registrations is subject 656 to continuing evaluation and modification, and in particular MAY be 657 extended by use of the "comments on media types" mechanism described 658 in Section 5.4 below. 660 Some of the issues that should be examined and described in a 661 security analysis of a media type are: 663 o Complex media types may include provisions for directives that 664 institute actions on a recipient's files or other resources. In 665 many cases provision is made for originators to specify arbitrary 666 actions in an unrestricted fashion that may then have devastating 667 effects. See the registration of the application/postscript media 668 type in [RFC2046] for an example of such directives and how they 669 should be described in a media type registration. 671 o All registrations MUST state whether or not they employ such 672 "active content", and if they do, they MUST state what steps have 673 been taken to protect users of the media type from harm. 675 o Complex media types may include provisions for directives that 676 institute actions that, while not directly harmful to the 677 recipient, may result in disclosure of information that either 678 facilitates a subsequent attack or else violates a recipient's 679 privacy in some way. Again, the registration of the application/ 680 postscript media type illustrates how such directives can be 681 handled. 683 o A media type that employs compression may provide an opportunity 684 for sending a small amount of data that, when received and 685 evaluated, expands enormously to consume all of the recipient's 686 resources. All media types SHOULD state whether or not they 687 employ compression, and if they do they should discuss what steps 688 need to be taken to avoid such attacks. 690 o A media type might be targeted for applications that require some 691 sort of security assurance but not provide the necessary security 692 mechanisms themselves. For example, a media type could be defined 693 for storage of sensitive medical information that in turn requires 694 an external confidentiality and integrity protection services, or 695 which is designed for use only within a secure environment. Types 696 not requiring such services SHOULD document this in their security 697 considerations. 699 4.7. Requirements specific to XML media types 701 There are a number of additional requirements specific to the 702 registration of XML media types. These requirements are specified in 703 [RFC3023]. 705 4.8. Encoding Requirements 707 Some transports impose restrictions on the type of data they can 708 carry. For example, Internet mail traditionally was limited to 7bit 709 US-ASCII text. Encoding schemes are often used to work around such 710 transport limitations. 712 It is therefore useful to note what sort of data a media type can 713 consist of as part of its registration. An "encoding considerations" 714 field is provided for this purpose. Possible values of this field 715 are: 717 7bit: The content of the media type consists solely of CRLF- 718 delimited 7bit US-ASCII text. 720 8bit: The content of the media type consists solely of CRLF- 721 delimited 8bit text. 723 binary: The content consists of an unrestricted sequence of octets. 725 framed: The content consists of a series of frames or packets 726 without internal framing or alignment indicators. Additional out- 727 of-band information is needed to interpret the data properly, 728 including but not necessarily limited to, knowledge of the 729 boundaries between successive frames and knowledge of the 730 transport mechanism. Note that media types of this sort cannot 731 simply be stored in a file or transported as a simple stream of 732 octets; therefore, such media types are unsuitable for use in many 733 traditional protocols. A commonly used transport with framed 734 encoding is the Real-time Transport Protocol, RTP. Additional 735 rules for framed encodings defined for transport using RTP are 736 given in [RFC4855]. 738 Additional restrictions on 7bit and 8bit text are given in Section 739 4.1.1 of [RFC2046]. 741 4.9. Usage and Implementation Non-requirements 743 In the asynchronous mail environment, where information on the 744 capabilities of the remote mail agent is frequently not available to 745 the sender, maximum interoperability is attained by restricting the 746 media types used to those "common" formats expected to be widely 747 implemented. This was asserted in the past as a reason to limit the 748 number of possible media types, and resulted in a registration 749 process with a significant hurdle and delay for those registering 750 media types. 752 However, the need for "common" media types does not require limiting 753 the registration of new media types. If a limited set of media types 754 is recommended for a particular application, that should be asserted 755 by a separate applicability statement specific for the application 756 and/or environment. 758 Therefore, universal support and implementation of a media type is 759 NOT a requirement for registration. However, if a media type is 760 explicitly intended for limited use, this MUST be noted in its 761 registration. The "Restrictions on Usage" field is provided for this 762 purpose. 764 4.10. Publication Requirements 766 Media types registered in the standards tree by the IETF itself MUST 767 be published as RFCs. RFC publication of vendor and personal media 768 type registrations is allowed but not required. In all cases the 769 IANA will retain copies of all media type registrations and "publish" 770 them as part of the media types registration tree itself. 772 As stated previously, standards tree registrations for media types 773 defined in documents produced by other standards bodies MUST be 774 described by a formal standards specification produced by that body. 775 Additionally, any copyright on the registration template MUST allow 776 the IANA to copy it into the IANA registry. 778 Other than IETF registrations in the standards tree, the registration 779 of a media type does not imply endorsement, approval, or 780 recommendation by the IANA or the IETF or even certification that the 781 specification is adequate. To become Internet Standards, a protocol 782 or data object must go through the IETF standards process. While it 783 provides additional assurances when it is appropriate, this is too 784 difficult and too lengthy a process for the convenient registration 785 of media types. 787 The standards tree exists for media types that do require a 788 substantive review and approval process in a recognized standards 789 body. The vendor and personal trees exist for those media types that 790 do not require such a process. It is expected that applicability 791 statements for particular applications will be published from time to 792 time in the IETF, recommending implementation of, and support for, 793 media types that have proven particularly useful in those contexts. 795 As discussed above, registration of a top-level type requires 796 standards-track processing in the IETF and, hence, RFC publication. 798 4.11. Additional Information 800 Various sorts of optional information SHOULD be included in the 801 specification of a media type if it is available: 803 o Magic number(s) (length, octet values). Magic numbers are byte 804 sequences that are always present at a given place in the file and 805 thus can be used to identify entities as being of a given media 806 type. 808 o File name extension(s) commonly used on one or more platforms to 809 indicate that some file contains a given media type. 811 o Mac OS File Type code(s) (4 octets) used to label files containing 812 a given media type. Some discussion of Macintosh file type codes 813 and their purpose can be found in [MacOSFileTypes]. 815 o Information about how fragment/anchor identifiers [RFC3986] are 816 constructed for use in conjunction with this media type. 818 In the case of a registration in the standards tree, this additional 819 information MAY be provided in the formal specification of the media 820 type. It is suggested that this be done by incorporating the IANA 821 media type registration form into the specification itself. 823 5. Media Type Registration Procedures 825 The media type registration procedure is not a formal standards 826 process, but rather an administrative procedure intended to allow 827 community comment and sanity checking without excessive time delay. 829 The normal IETF processes should be followed for all IETF 830 registrations in the standards tree. The posting of an Internet 831 Draft is a necessary first step, followed by posting to the 832 media-types@iana.org list as discussed below. 834 5.1. Preliminary Community Review 836 Notice of a potential media type registration in the standards tree 837 SHOULD be sent to the media-types@iana.org mailing list for review. 838 This mailing list has been established for the purpose of reviewing 839 proposed media and access types. Registrations in other trees MAY be 840 sent to the list for review as well; doing so is entirely OPTIONAL, 841 but is strongly encouraged. 843 The intent of the public posting to this list is to solicit comments 844 and feedback on the choice of type/subtype name, the unambiguity of 845 the references with respect to versions and external profiling 846 information, and a review of any interoperability or security 847 considerations. The submitter may submit a revised registration 848 proposal or abandon the registration completely and at any time. 850 5.2. Submit request to IANA 852 Media types registered in the standards tree by the IETF itself MUST 853 be reviewed and approved by the IESG as part of the normal standards 854 process. Standards tree registrations by recognized standards bodies 855 as well as registrations in the vendor and personal tree should be 856 submitted directly to the IANA, unless other arrangements were made 857 as part of a liaison agreement. In either case posting the 858 registration to the media-types@iana.org list for review prior to 859 submission is strongly encouraged. 861 Registration requests can be sent to iana@iana.org. A web form for 862 registration requests is also available: 864 http://www.iana.org/cgi-bin/mediatypes.pl 866 5.2.1. Provisional Registrations 868 Standardization processes often take considerable time to complete. 869 In order to facilitate prototyping and testing it is often helpful to 870 assign identifiers, including but not limited to media types, early 871 in the process. This way identifiers used during standards 872 development can remain unchanged once the process is complete and 873 implementations and documentation do not have to be updated. 875 Accordingly, a provisional registration process is provided to 876 support early assignment of media type names. A provisional 877 registration MAY be submitted to IANA for standards tree types. The 878 only required fields in such registrations are the media type name 879 and contact information (including the standards body name). 881 Upon receipt of a provisional registration, IANA will check the name 882 and contact information, then publish the registration in a separate 883 provisional registration list. 885 Provisional registrations MAY be updated or abandoned at any time. 887 5.3. Review and Approval 889 With the exception of provisional standards tree registrations, 890 registrations submitted to the IANA will be passed on to the media 891 types reviewer. The media types reviewer, who is appointed by the 892 IETF Applications Area Director(s), will review the registration to 893 make sure it meets the requirements set forth in this document. 894 Registrations that do not meet these requirements will be returned to 895 the submitter for revision. 897 Decisions made by the media types reviewer may be appealed to the 898 IESG using the procedure specified in section 6.5.4 of [RFC2026]. 900 Once a media type registration has passed review, the IANA will 901 register the media type and make the media type registration 902 available to the community. 904 In the case of standards tree registrations from other standards 905 bodies IANA will also check that the submitter is in fact a 906 recognized standards body. If the submitter is not currently 907 recognized as such the IESG will be asked to confirm their status. 908 Recognition from the IESG MUST be obtained before a standards tree 909 registration can proceed. 911 5.4. Comments on Media Type Registrations 913 Comments on registered media types may be submitted by members of the 914 community to the IANA at iana@iana.org. These comments will be 915 reviewed by the media types reviewer and then passed on to the 916 "owner" of the media type if possible. Submitters of comments may 917 request that their comment be attached to the media type registration 918 itself, and if the IANA approves of this, the comment will be made 919 accessible in conjunction with the type registration. 921 5.5. Location of Registered Media Type List 923 Media type registrations are listed by the IANA at: 925 http://www.iana.org/assignments/media-types/ 927 5.6. Change Procedures 929 Once a media type has been published by the IANA, the owner may 930 request a change to its definition. The descriptions of the 931 different registration trees above designate the "owners" of each 932 type of registration. The same procedure that would be appropriate 933 for the original registration request is used to process a change 934 request. 936 Significant changes to a media type's definition should be requested 937 only when there are serious omissions or errors in the published 938 specification. When review is required, a change request may be 939 denied if it renders entities that were valid under the previous 940 definition invalid under the new definition. 942 The owner of a media type may pass responsibility to another person 943 or agency by informing the IANA; this can be done without discussion 944 or review. 946 The IESG may reassign responsibility for a media type. The most 947 common case of this will be to enable changes to be made to types 948 where the author of the registration has died, moved out of contact 949 or is otherwise unable to make changes that are important to the 950 community. 952 Media type registrations may not be deleted; media types that are no 953 longer believed appropriate for use can be declared OBSOLETE by a 954 change to their "intended use" field; such media types will be 955 clearly marked in the lists published by the IANA. 957 5.7. Registration Template 959 Type name: 961 Subtype name: 963 Required parameters: 965 Optional parameters: 967 Encoding considerations: 969 Security considerations: 971 Interoperability considerations: 973 Published specification: 975 Applications that use this media type: 977 Additional information: 979 Deprecated alias names for this type: 980 Magic number(s): 981 File extension(s): 982 Macintosh file type code(s): 983 URI fragment/anchor identifier(s): 985 Person & email address to contact for further information: 987 Intended usage: 989 (One of COMMON, LIMITED USE or OBSOLETE.) 991 Restrictions on usage: 993 (Any restrictions on where the media type can be used go here.) 995 Author: 997 Change controller: 999 Provisional registration? (standards tree only): 1001 (Any other information that the author deems interesting may be 1002 added below this line.) 1003 "N/A", written exactly that way, can be used in any field if desired 1004 to emphasize the fact that it does not apply or that the question was 1005 not omitted by accident. Do not use 'none' or other words that could 1006 be mistaken for a response. 1008 Limited use media types should also note in the applications list 1009 whether or not that list is exhaustive. 1011 6. Structured Syntax Suffix Registration Procedures 1013 Someone wishing to define a "+suffix" name for a structured syntax 1014 for use with a new media type registration SHOULD: 1016 1. Check IANA's registry of media type name suffixes to see whether 1017 or not there is already an entry for that well-defined structured 1018 syntax. 1020 2. If there is no entry for their suffix scheme, fill out the 1021 template (specified in Section 6.2) and include that with the 1022 media type registration. The template may be contained in an 1023 Internet Draft, alone or as part of some other protocol 1024 specification. The template may also be submitted in some other 1025 form (as part of another document or as a stand-alone document), 1026 but the contents will be treated as an "IETF Contribution" under 1027 the guidelines of RFC 5378 [RFC5378]. 1029 3. Send a copy of the template or a pointer to the containing 1030 document (with specific reference to the section with the 1031 template) to the mailing list media-types@iana.org, requesting 1032 review. This may be combined with a request to review the media 1033 type registration. Allow a reasonable time for discussion and 1034 comments. 1036 4. Respond to review comments and make revisions to the proposed 1037 registration as needed to bring it into line with the guidelines 1038 given in this document. 1040 5. Submit the (possibly updated) registration template (or pointer 1041 to the document containing it) to IANA at iana@iana.org. 1043 Upon receipt of a structured syntax suffix registration request, 1045 1. IANA checks the submission for completeness; if sections are 1046 missing or citations are not correct, IANA rejects the 1047 registration request. 1049 2. IANA checks the current registry for an entry with the same name; 1050 if such a registry exists, IANA rejects the registration request. 1052 3. IANA requests Expert Review of the registration request against 1053 the corresponding guidelines. 1055 4. The Designated Expert may request additional review or 1056 discussion, as necessary. 1058 5. If Expert Review recommends registration, IANA adds the 1059 registration to the appropriate registry. 1061 6.1. Change Procedures 1063 Registrations may be updated in each registry by the same mechanism 1064 as required for an initial registration. In cases where the original 1065 definition of the scheme is contained in an IESG-approved document, 1066 update of the specification also requires IESG approval. 1068 6.2. Structured Syntax Suffix Registration Template 1070 This template describes the fields that must be supplied in a 1071 structured syntax suffix registration request: 1073 Name 1074 Full name of the well-defined structured syntax. 1076 +suffix 1077 Suffix used to indicate conformance to the syntax. 1079 References. 1080 Include full citations for all specifications necessary to 1081 understand the structured syntax. 1083 Encoding considerations 1084 General guidance regarding encoding considerations for any type 1085 employing this syntax should be given here. The same requirements 1086 for media type encoding considerations given in Section 4.8 apply 1087 here. 1089 Interoperability considerations 1090 Any issues regarding the interoperable use of types employing this 1091 structured syntax should be given here. Examples would include 1092 the existence of incompatible versions of the syntax, issues 1093 combining certain charsets with the syntax, or incompatibilities 1094 with other types or protocols. 1096 Security considerations 1097 Security considerations shared by media types employing this 1098 structured syntax must be specified here. The same requirements 1099 for media type security considerations given in Section 4.6 apply 1100 here, with the exception that option of not assessing the security 1101 considerations is not available for suffix registrations. 1103 Contact 1104 Person (including contact information) to contact for further 1105 information. 1107 Author/Change controller. 1108 Person (including contact information) authorized to change this 1109 suffix registration. 1111 7. Security Considerations 1113 Security requirements for media type registrations are discussed in 1114 Section 4.6. 1116 8. IANA Considerations 1118 The purpose of this document is to define IANA registries for media 1119 types and structured syntax suffixes as well as the procedures for 1120 managing these registries. Additionally, this document requires IANA 1121 to maintain a list of IESG-recognized standards bodies who are 1122 allowed to register types in the standards tree. 1124 This document also creates a new registry for structured syntax 1125 names: 1127 o The name is the "Structured Syntax Suffix" registry. 1129 o The registration process is specified in Section 6. 1131 o The information required for a registry entry as well as the entry 1132 format are specified in Section 6.2. 1134 o The initial content of the registry is specified in 1135 [I-D.hansen-media-type-suffix-regs]. 1137 Finally, this document calls for the creation of a new email address, 1138 media-types@iana.org, for the media type review list, which replaces 1139 the ietf-types@iana.org address specified in RFC 4288. 1140 ietf-types@iana.org should be retained as an alias. 1142 9. Acknowledgements 1144 The current authors would like to acknowledge their debt to the late 1145 Dr. Jon Postel, whose general model of IANA registration procedures 1146 and specific contributions shaped the predecessors of this document 1147 [RFC2048]. We hope that the current version is one with which he 1148 would have agreed but, as it is impossible to verify that agreement, 1149 we have regretfully removed his name as a co-author. 1151 Barry Leiba, Murray Kucherawy, Alexey Melnikov, and Peter Saint-Andre 1152 provided many helpful review comments and suggestions. 1154 10. References 1156 10.1. Normative References 1158 [I-D.hansen-media-type-suffix-regs] 1159 Hansen, T., "Additional Media Type Structured Syntax 1160 Suffixes", draft-hansen-media-type-suffix-regs-01 (work in 1161 progress), April 2012. 1163 [I-D.ietf-appsawg-mime-default-charset] 1164 Melnikov, A. and J. Reschke, "Update to MIME regarding 1165 Charset Parameter Handling in Textual Media Types", 1166 draft-ietf-appsawg-mime-default-charset-01 (work in 1167 progress), March 2012. 1169 [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1170 Extensions (MIME) Part One: Format of Internet Message 1171 Bodies", RFC 2045, November 1996. 1173 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 1174 Extensions (MIME) Part Two: Media Types", RFC 2046, 1175 November 1996. 1177 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1178 Requirement Levels", BCP 14, RFC 2119, March 1997. 1180 [RFC2978] Freed, N. and J. Postel, "IANA Charset Registration 1181 Procedures", BCP 19, RFC 2978, October 2000. 1183 [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media 1184 Types", RFC 3023, January 2001. 1186 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 1187 10646", STD 63, RFC 3629, November 2003. 1189 [RFC3979] Bradner, S., "Intellectual Property Rights in IETF 1190 Technology", BCP 79, RFC 3979, March 2005. 1192 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1193 Resource Identifier (URI): Generic Syntax", STD 66, 1194 RFC 3986, January 2005. 1196 [RFC4855] Casner, S., "Media Type Registration of RTP Payload 1197 Formats", RFC 4855, February 2007. 1199 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1200 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1201 May 2008. 1203 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 1204 Specifications: ABNF", STD 68, RFC 5234, January 2008. 1206 [RFC5378] Bradner, S. and J. Contreras, "Rights Contributors Provide 1207 to the IETF Trust", BCP 78, RFC 5378, November 2008. 1209 [RFC6532] Yang, A., Steel, S., and N. Freed, "Internationalized 1210 Email Headers", RFC 6532, January 2012. 1212 10.2. Informative References 1214 [I-D.ietf-appsawg-xdash] 1215 Saint-Andre, P. and D. Crocker, "Deprecating the X- Prefix 1216 and Similar Constructs in Application Protocols", 1217 draft-ietf-appsawg-xdash-05 (work in progress), 1218 April 2012. 1220 [MacOSFileTypes] 1221 Apple Computer, Inc., "Mac OS: File Type and Creator 1222 Codes, and File Formats", Apple Knowledge Base Article 1223 55381, June 1993, 1224 . 1226 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 1227 3", BCP 9, RFC 2026, October 1996. 1229 [RFC2048] Freed, N., Klensin, J., and J. Postel, "Multipurpose 1230 Internet Mail Extensions (MIME) Part Four: Registration 1231 Procedures", BCP 13, RFC 2048, November 1996. 1233 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 1234 Word Extensions: 1235 Character Sets, Languages, and Continuations", RFC 2231, 1236 November 1997. 1238 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 1239 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 1240 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 1242 [RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and 1243 Registration Procedures", BCP 13, RFC 4288, December 2005. 1245 Appendix A. Grandfathered Media Types 1247 A number of media types with unfaceted names, registered prior to 1248 1996, would, if registered under the guidelines in this document, be 1249 given a faceted name and placed into either the vendor or personal 1250 trees. Reregistration of those types to reflect the appropriate 1251 trees is encouraged but not required. Ownership and change control 1252 principles outlined in this document apply to those types as if they 1253 had been registered in the trees described above. 1255 From time to time there may also be cases where a media type with an 1256 unfaceted name has been widely deployed without being registered. 1257 (Note that this includes types with names beginning with the "x-" 1258 prefix.) If possible such types SHOULD be reregistered with a proper 1259 faceted name. However, if this is not possible the type can, subject 1260 to approval by both the media types reviewer and the IESG, be 1261 registered in the proper tree with its unfaceted name. 1263 Appendix B. Changes Since RFC 4288 1265 o Suffixes to indicate the use of a particular structured syntax are 1266 now fully specified and a suffix registration process has been 1267 defined. 1269 o Registration of widely deployed unregistered unfaceted type names 1270 in the vendor or personal trees is now allowed, subject to 1271 approval by the media types reviewer and the IESG. 1273 o The standards tree registration process has been revised to 1274 include Expert Review and generalized to address cases like media 1275 types in non-IETF stream documents. 1277 o A field for fragment/anchor identifiers has been added to the 1278 registration template. 1280 o The specification requirements for personal tree registrations 1281 have been changed to be the same as those for the vendor tree. 1282 The text has been changed to encourage (but not require) 1283 specification availability. 1285 o The definition of additional trees has been clarified to state 1286 that an IETF Standards Action is required. 1288 o Widely deployed types with "x-" names can now be registered as an 1289 exception in the vendor tree. 1291 o The requirements on changes to registrations have been loosened so 1292 minor changes are easier to make. 1294 o The registration process has been completely restructured so that 1295 with the exception of IETF-generated types in the standards tree, 1296 all requests are processed by IANA and not the IESG. 1298 o A provisional registration process has been added for early 1299 assignment of types in the standards tree. 1301 o Many editorial changes have been made throughout the document to 1302 make the requirements and processes it describes clearer and 1303 easier to follow. 1305 o The ability to specify a list of deprecated aliases for a media 1306 type has been added. 1308 o Types with names beginning with "x-" are no longer considered to 1309 be members of the unregistered "x." tree. As with any unfaceted 1310 type, special procedures have been added to allow registration of 1311 such types in an appropriate tree. 1313 o Changes to a type registered by a third party may now be made by 1314 the designated change controller even if that isn't the vendor or 1315 organization that created the type. However, the vendor or 1316 organization may elect to assert ownership and change controller 1317 over the type at any time. 1319 o Limited use media types are now asked to note whether or not the 1320 supplied list of applications employing the media type is 1321 exhaustive. 1323 o The ABNF for media type names has been further restricted to 1324 require that names begin with an alphanumeric character. 1326 o Mailing list review is no longer required prior to registration of 1327 media types. Additionally, the address associated with the media 1328 type review mailing list has been changed to media-types@iana.org. 1330 Authors' Addresses 1332 Ned Freed 1333 Oracle 1334 800 Royal Oaks 1335 Monrovia, CA 91016-6347 1336 USA 1338 Email: ned+ietf@mrochek.com 1340 John C. Klensin 1341 1770 Massachusetts Ave, #322 1342 Cambridge, MA 02140 1343 USA 1345 Email: john+ietf@jck.com 1347 Tony Hansen 1348 AT&T Laboratories 1349 200 Laurel Ave. 1350 Middletown, NJ 07748 1351 USA 1353 Email: tony+mtsuffix@maillennium.att.com