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Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-24) exists of draft-ietf-slim-negotiating-human-language-13 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IETF N. Tomkinson 3 Internet-Draft N. Borenstein 4 Intended status: Standards Track Mimecast Ltd 5 Expires: February 2, 2018 August 1, 2017 7 Multiple Language Content Type 8 draft-ietf-slim-multilangcontent-10 10 Abstract 12 This document defines an addition to the Multipurpose Internet Mail 13 Extensions (MIME) standard to make it possible to send one message 14 that contains multiple language versions of the same information. 15 The translations would be identified by a language tag and selected 16 by the email client based on a user's language settings. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on February 2, 2018. 35 Copyright Notice 37 Copyright (c) 2017 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 1. Introduction 52 Since the invention of email and the rapid spread of the Internet, 53 more and more people have been able to communicate in more and more 54 countries and in more and more languages. But during this time of 55 technological evolution, email has remained a single-language 56 communication tool, whether it is English to English, Spanish to 57 Spanish or Japanese to Japanese. 59 Also during this time, many corporations have established their 60 offices in multi-cultural cities and formed departments and teams 61 that span continents, cultures and languages, so the need to 62 communicate efficiently with little margin for miscommunication has 63 grown significantly. 65 The objective of this document is to define an addition to the 66 Multipurpose Internet Mail Extensions (MIME) standard, to make it 67 possible to send a single message to a group of people in such a way 68 that all of the recipients can read the email in their preferred 69 language. The methods of translation of the message content are 70 beyond the scope of this document, but the structure of the email 71 itself is defined herein. 73 Whilst this document depends on identification of language in message 74 parts for non-real-time communication, there is a companion document 75 that is concerned with a similar problem for real-time communication: 76 [I-D.ietf-slim-negotiating-human-language] 78 1.1. Requirements Language 80 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 81 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 82 document are to be interpreted as described in RFC 2119 [RFC2119]. 84 2. The Content-Type Header Field 86 The "multipart/multilingual" MIME subtype allows the sending of a 87 message in a number of different languages with the translations 88 embedded in the same message. This MIME subtype helps the receiving 89 email client make sense of the message structure. 91 The multipart subtype "multipart/multilingual" has similar semantics 92 to "multipart/alternative" (as discussed in RFC 2046 [RFC2046]) in 93 that each of the message parts is an alternative version of the same 94 information. The primary difference between "multipart/multilingual" 95 and "multipart/alternative" is that when using "multipart/ 96 multilingual", the message part to select for rendering is chosen 97 based on the values of the Content-Language field and optionally the 98 Translation-Type field instead of the ordering of the parts and the 99 Content-Types. 101 The syntax for this multipart subtype conforms to the common syntax 102 for subtypes of multipart given in section 5.1.1. of RFC 2046 103 [RFC2046]. An example "multipart/multilingual" Content-Type header 104 field would look like this: 106 Content-Type: multipart/multilingual; boundary=01189998819991197253 108 3. The Message Parts 110 A multipart/multilingual message will have a number of message parts: 111 exactly one multilingual preface, one or more language message parts 112 and zero or one language independent message part. The details of 113 these are described below. 115 3.1. The Multilingual Preface 117 In order for the message to be received and displayed in non- 118 conforming email clients, the message SHOULD contain an explanatory 119 message part which MUST NOT be marked with a Content-Language field 120 and MUST be the first of the message parts. For maximum support in 121 the most basic of non-conforming email clients, it SHOULD have a 122 Content-Type of text/plain. Because non-conforming email clients are 123 expected to treat a message with an unknown multipart type as 124 multipart/mixed (in accordance with sections 5.1.3 and 5.1.7 of RFC 125 2046 [RFC2046]) they may show all of the message parts sequentially 126 or as attachments. Including and showing this explanatory part will 127 help the message recipient understand the message structure. 129 This initial message part SHOULD explain briefly to the recipient 130 that the message contains multiple languages and the parts may be 131 rendered sequentially or as attachments. This SHOULD be presented in 132 the same languages that are provided in the subsequent language 133 message parts. 135 As this explanatory section is likely to contain languages using 136 scripts that require non-US-ASCII characters, it is RECOMMENDED that 137 UTF-8 charset is used for this message part. See RFC 3629 [RFC3629] 138 for details of UTF-8. 140 Whilst this section of the message is useful for backward 141 compatibility, it will normally only be shown when rendered by a non- 142 conforming email client, because conforming email clients SHOULD only 143 show the single language message part identified by the user's 144 preferred language and the language message part's Content-Language. 146 For the correct display of the multilingual preface in a non- 147 conforming email client, the sender MAY use the Content-Disposition 148 field with a value of 'inline' in conformance with RFC 2183 [RFC2183] 149 (which defines the Content-Disposition field). If provided, this 150 SHOULD be placed at the multipart/multilingual level and in the 151 multilingual preface. This makes it clear to a non-conforming email 152 client that the multilingual preface should be displayed immediately 153 to the recipient, followed by any subsequent parts marked as 154 'inline'. 156 For an example of a multilingual preface, see the examples in 157 Section 8. 159 3.2. The Language Message Parts 161 The language message parts are typically translations of the same 162 message content. These message parts SHOULD be ordered so that the 163 first part after the multilingual preface is in the language believed 164 to be the most likely to be recognised by the recipient as this will 165 constitute the default part when language negotiation fails and there 166 is no Language Independent part. All of the language message parts 167 MUST have a Content-Language field and a Content-Type field and MAY 168 have a Translation-Type field. 170 The Content-Type for each individual language message part SHOULD be 171 message/rfc822 to provide good support with non-conforming email 172 clients. However, an implementation MAY use message/global as 173 support for message/global becomes more commonplace. See RFC 6532 174 [RFC6532] for details of message/global. Each language message part 175 SHOULD have a Subject field in the appropriate language for that 176 language part. If there is a From field present, its value MUST 177 include the same email address as the top-level From header although 178 the display name MAY be a localised version. 180 3.3. The Language Independent Message Part 182 If there is language independent content intended for the recipient 183 to see if they have a preferred language other than one of those 184 specified in the language message parts and the default language 185 message part is unlikely to be understood, another part MAY be 186 provided. This could typically include a language independent 187 graphic. When this part is present, it MUST be the last part and 188 MUST have a Content-Language field with a value of "zxx" (as 189 described in BCP 47/RFC 5646 [RFC5646]). The part SHOULD have a 190 Content-Type of message/rfc822 or message/global (to match the 191 language message parts). 193 4. Message Part Selection 195 The logic for selecting the message part to render and present to the 196 recipient is summarised in the next few paragraphs. 198 Firstly, if the email client does not understand multipart/ 199 multilingual then it will treat the message as if it was multipart/ 200 mixed and render message parts accordingly (in accordance with 201 sections 5.1.3 and 5.1.7 of RFC 2046 [RFC2046]). 203 If the email client does understand multipart/multilingual then it 204 SHOULD ignore the multilingual preface and select the best match for 205 the user's preferred language from the language message parts 206 available. Also, the user may prefer to see the original message 207 content in their second language over a machine translation in their 208 first language. The Translation-Type field value can be used for 209 further selection based on this preference. The selection of 210 language part may be implemented in a variety of ways, although the 211 matching schemes detailed in RFC 4647 [RFC4647] are RECOMMENDED as a 212 starting point for an implementation. The goal is to render the most 213 appropriate translation for the user. 215 If there is no match for the user's preferred language (or there is 216 no preferred language information available) the email client SHOULD 217 select the language independent part (if one exists) or the first 218 language part (directly after the multilingual preface) if a language 219 independent part does not exist. 221 If there is no translation type preference information available, the 222 values of the Translation-Type field may be ignored. 224 Additionally, interactive implementations MAY offer the user a choice 225 from among the available languages. 227 5. The Content-Language Field 229 The Content-Language field in the individual language message parts 230 is used to identify the language in which the message part is 231 written. Based on the value of this field, a conforming email client 232 can determine which message part to display (given the user's 233 language settings). 235 The Content-Language MUST comply with RFC 3282 [RFC3282] (which 236 defines the Content-Language field) and BCP 47/RFC 5646 [RFC5646] 237 (which defines the structure and semantics for the language code 238 values). 240 Examples of this field for English, German and an instruction manual 241 in Spanish and French, could look like the following: 243 Content-Language: en 245 Content-Language: de 247 Content-Language: es, fr 249 6. The Translation-Type Field 251 The Translation-Type field can be used in the individual language 252 message parts to identify the type of translation. Based on the 253 value of this parameter and the user's preferences, a conforming 254 email client can determine which message part to display. 256 This field can have one of three possible values: 'original', 'human' 257 or 'automated' although other values may be added in the future. A 258 value of 'original' is given in the language message part that is in 259 the original language. A value of 'human' is used when a language 260 message part is translated by a human translator or a human has 261 checked and corrected an automated translation. A value of 262 'automated' is used when a language message part has been translated 263 by an electronic agent without proofreading or subsequent correction. 265 Examples of this field include: 267 Translation-Type: original 269 Translation-Type: human 271 The syntax of the Translation-Type field in ABNF RFC 5234 [RFC5234] 272 is: 274 Translation-Type = [FWS] translationtype 276 FWS = 277 translationtype = "original" / "human" / "automated" 279 This references RFC 5322 [RFC5322] for a pre-defined rule FWS. 281 7. The Subject Field in the Language Message parts 283 On receipt of the message, conforming email clients will need to 284 render the subject in the correct language for the recipient. To 285 enable this the Subject field SHOULD be provided in each language 286 message part. The value for this field should be a translation of 287 the email subject. 289 US-ASCII and 'encoded-word' examples of this field include: 291 Subject: A really simple email subject 293 Subject: =?UTF-8?Q?Un_asunto_de_correo_electr=C3=b3nico_ 294 realmente_sencillo?= 296 See RFC 2047 [RFC2047] for the specification of 'encoded-word'. 298 The subject to be presented to the recipient should be selected from 299 the message part identified during the message part selection stage. 300 If no Subject field is found the top-level Subject header field value 301 should be used. 303 8. Examples 305 8.1. An Example of a Simple Multiple language email message 307 Below is a minimal example of a multiple language email message. It 308 has the multilingual preface and two language message parts. 310 From: Nik@example.com 311 To: Nathaniel@example.com 312 Subject: Example of a message in Spanish and English 313 Date: Thu, 7 Apr 2017 21:28:00 +0100 314 MIME-Version: 1.0 315 Content-Type: multipart/multilingual; 316 boundary="01189998819991197253" 318 --01189998819991197253 319 Content-Type: text/plain; charset="UTF-8" 320 Content-Disposition: inline 321 Content-Transfer-Encoding: quoted-printable 323 This is a message in multiple languages. It says the 324 same thing in each language. If you can read it in one language, 325 you can ignore the other translations. The other translations may be 326 presented as attachments or grouped together. 328 Este es un mensaje en varios idiomas. Dice lo mismo en 329 cada idioma. Si puede leerlo en un idioma, puede ignorar las otras 330 traducciones. Las otras traducciones pueden presentarse como archivos 331 adjuntos o agrupados. 333 --01189998819991197253 334 Content-Type: message/rfc822 335 Content-Language: en 336 Translation-Type: original 337 Content-Disposition: inline 339 Subject: Example of a message in Spanish and English 340 Content-Type: text/plain; charset="US-ASCII" 341 Content-Transfer-Encoding: 7bit 342 MIME-Version: 1.0 344 Hello, this message content is provided in your language. 346 --01189998819991197253 347 Content-Type: message/rfc822 348 Content-Language: es 349 Translation-Type: human 350 Content-Disposition: inline 352 Subject: =?UTF-8?Q?Ejemplo_pr=C3=A1ctico_de_mensaje_?= 353 =?UTF-8?Q?en_espa=C3=B1ol_e_ingl=C3=A9s?= 354 Content-Type: text/plain; charset="US-ASCII" 355 Content-Transfer-Encoding: 7bit 356 MIME-Version: 1.0 358 Hola, el contenido de este mensaje esta disponible en su idioma. 360 --01189998819991197253-- 362 8.2. An Example of a Multiple language email message with language 363 independent part 365 Below is an example of a multiple language email message that has the 366 multilingual preface followed by two language message parts and then 367 a language independent png image. 369 From: Nik@example.com 370 To: Nathaniel@example.com 371 Subject: Example of a message in Spanish and English 372 Date: Thu, 7 Apr 2017 21:08:00 +0100 373 MIME-Version: 1.0 374 Content-Type: multipart/multilingual; 375 boundary="01189998819991197253" 377 --01189998819991197253 378 Content-Type: text/plain; charset="UTF-8" 379 Content-Disposition: inline 380 Content-Transfer-Encoding: quoted-printable 382 This is a message in multiple languages. It says the 383 same thing in each language. If you can read it in one language, 384 you can ignore the other translations. The other translations may be 385 presented as attachments or grouped together. 387 Este es un mensaje en varios idiomas. Dice lo mismo en 388 cada idioma. Si puede leerlo en un idioma, puede ignorar las otras 389 traducciones. Las otras traducciones pueden presentarse como archivos 390 adjuntos o agrupados. 392 --01189998819991197253 393 Content-Type: message/rfc822 394 Content-Language: en 395 Translation-Type: original 396 Content-Disposition: inline 398 Subject: Example of a message in Spanish and English 399 Content-Type: text/plain; charset="US-ASCII" 400 Content-Transfer-Encoding: 7bit 401 MIME-Version: 1.0 403 Hello, this message content is provided in your language. 405 --01189998819991197253 406 Content-Type: message/rfc822 407 Content-Language: es 408 Translation-Type: human 409 Content-Disposition: inline 411 Subject: =?UTF-8?Q?Ejemplo_pr=C3=A1ctico_de_mensaje_?= 412 =?UTF-8?Q?en_espa=C3=B1ol_e_ingl=C3=A9s?= 413 Content-Type: text/plain; charset="US-ASCII" 414 Content-Transfer-Encoding: 7bit 415 MIME-Version: 1.0 417 Hola, el contenido de este mensaje esta disponible en su idioma. 419 --01189998819991197253 420 Content-Type: message/rfc822; name="Icon" 421 Content-Language: zxx 422 Content-Disposition: inline 424 Content-Type: image/png; name="icon.png" 425 Content-Transfer-Encoding: base64 427 iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAKQ2lDQ1BJQ0MgUHJvZmlsZQAA 428 SA2dlndUU1... shortened for brevity ...7yxfd1SNsEy+OXr76qr 429 997zF2hvZYeDEP5ftGV6Xzx2o9MAAAAASUVORK5CYII= 431 --01189998819991197253-- 432 8.3. An Example of a complex Multiple language email message with 433 language independent part 435 Below is an example of a more complex multiple language email 436 message. It has the multilingual preface and two language message 437 parts and then a language independent png image. The language 438 message parts have multipart/alternative contents and would therefore 439 require further processing to determine the content to display. 441 From: Nik@example.com 442 To: Nathaniel@example.com 443 Subject: Example of a message in Spanish and English 444 Date: Thu, 7 Apr 2017 20:55:00 +0100 445 MIME-Version: 1.0 446 Content-Type: multipart/multilingual; 447 boundary="01189998819991197253" 449 --01189998819991197253 450 Content-Type: text/plain; charset="UTF-8" 451 Content-Disposition: inline 452 Content-Transfer-Encoding: quoted-printable 454 This is a message in multiple languages. It says the 455 same thing in each language. If you can read it in one language, 456 you can ignore the other translations. The other translations may be 457 presented as attachments or grouped together. 459 Este es un mensaje en varios idiomas. Dice lo mismo en 460 cada idioma. Si puede leerlo en un idioma, puede ignorar las otras 461 traducciones. Las otras traducciones pueden presentarse como archivos 462 adjuntos o agrupados. 464 --01189998819991197253 465 Content-Type: message/rfc822 466 Content-Language: en 467 Translation-Type: original 468 Content-Disposition: inline 470 Subject: Example of a message in Spanish and English 471 Content-Type: multipart/alternative; 472 boundary="72530118999911999881"; charset="US-ASCII" 473 Content-Transfer-Encoding: 7bit 474 MIME-Version: 1.0 476 --72530118999911999881 477 Content-Type: text/plain; charset="US-ASCII" 478 Content-Transfer-Encoding: 7bit 479 Hello, this message content is provided in your language. 481 --72530118999911999881 482 Content-Type: text/html; charset="US-ASCII" 483 Content-Transfer-Encoding: 7bit 485 Hello, this message content is provided in 486 your language. 488 --72530118999911999881-- 489 --01189998819991197253 490 Content-Type: message/rfc822 491 Content-Language: es 492 Translation-Type: human 493 Content-Disposition: inline 495 Subject: =?UTF-8?Q?Ejemplo_pr=C3=A1ctico_de_mensaje_?= 496 =?UTF-8?Q?en_espa=C3=B1ol_e_ingl=C3=A9s?= 497 Content-Type: multipart/alternative; 498 boundary="53011899989991197281"; charset="US-ASCII" 499 Content-Transfer-Encoding: 7bit 500 MIME-Version: 1.0 502 --53011899989991197281 503 Content-Type: text/plain; charset="US-ASCII" 504 Content-Transfer-Encoding: 7bit 506 Hola, el contenido de este mensaje esta disponible en su idioma. 508 --53011899989991197281 509 Content-Type: text/html; charset="US-ASCII" 510 Content-Transfer-Encoding: 7bit 512 Hola, el contenido de este mensaje esta 513 disponible en su idioma. 515 --53011899989991197281-- 516 --01189998819991197253 517 Content-Type: message/rfc822; name="Icon" 518 Content-Language: zxx 519 Content-Disposition: inline 521 Content-Type: multipart/mixed; 522 boundary="99911972530118999881"; charset="US-ASCII" 523 Content-Transfer-Encoding: 7bit 524 MIME-Version: 1.0 526 --99911972530118999881 527 Content-Type: image/png; name="icon.png" 528 Content-Disposition: inline 529 Content-Transfer-Encoding: base64 531 iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAKQ2lDQ1BJQ0MgUHJvZmlsZQAA 532 SA2dlndUU1... shortened for brevity ...7yxfd1SNsEy+OXr76qr 533 997zF2hvZYeDEP5ftGV6Xzx2o9MAAAAASUVORK5CYII= 535 --99911972530118999881-- 536 --01189998819991197253-- 538 9. Acknowledgements 540 The authors are grateful for the helpful input received from many 541 people but would especially like to acknowledge the help of Harald 542 Alvestrand, Stephane Bortzmeyer, Eric Burger, Mark Davis, Doug Ewell, 543 Randall Gellens, Gunnar Hellstrom, Barry Leiba, Sean Leonard, John 544 Levine, Alexey Melnikov, Addison Phillips, Julian Reschke, Pete 545 Resnick, Brian Rosen, Fiona Tomkinson, Simon Tyler and Daniel Vargha. 547 The authors would also like to thank Fernando Alvaro and Luis de 548 Pablo for their work on the Spanish translations. 550 10. IANA Considerations 552 10.1. The multipart/multilingual MIME type 554 The multipart/multilingual MIME type will be registered with IANA 555 including a reference to this document. This is the registration 556 template: 558 Media Type name: multipart 560 Media subtype name: multilingual 562 Required parameters: boundary (defined in RFC2046) 564 Optional parameters: N/A 566 Encoding considerations: There are no encoding considerations for 567 this multipart other than that of the embedded body parts. 568 The embedded body parts (typically one text/plain plus one or 569 more message/*) may contain 7-bit, 8-bit or binary encodings. 571 Security considerations: See the Security Considerations section 572 in RFC XXXX 574 Interoperability considerations: 575 Existing systems that do not treat unknown multipart subtypes 576 as multipart/mixed may not correctly render a 577 multipart/multilingual type. These systems would also be non- 578 compliant with MIME. 580 Author/Change controller: IETF 582 Published specification: RFC XXXX 584 Applications that use this media type: 585 Mail Transfer Agents, Mail User Agents, spam detection, 586 virus detection modules and message authentication modules. 588 Additional information: 589 Deprecated alias names for this type: N/A 590 Magic number(s): N/A 591 File extension(s): N/A 592 Macintosh file type code(s): N/A 594 Person & email address to contact for further information: 595 Nik Tomkinson 596 rfc.nik.tomkinson@gmail.com 598 Nathaniel Borenstein 599 nsb@mimecast.com 601 Intended usage: Common 603 10.2. The Translation-Type field 605 The Translation-Type field will be added to the IANA "Permanent 606 Message Header Field Names" registry. That entry will reference this 607 document. This is the registration template: 609 Header field name: Translation-Type 611 Applicable protocol: mail 613 Status: Standard 615 Author/Change controller: IETF 617 Specification document(s): RFC XXXX 619 Related information: none 621 11. Security Considerations 623 Whilst it is intended that each language message part is a direct 624 translation of the original message, this may not always be the case 625 and these parts could contain undesirable content. Therefore there 626 is a possible risk that undesirable text or images could be shown to 627 the recipient if the message is passed through a spam filter that 628 does not check all of the message parts. The risk should be minimal 629 due to the fact that an unknown multipart subtype should be treated 630 as multipart/mixed and so each message part should be subsequently 631 scanned. 633 Because the language message parts have a Content-Type of message/ 634 rfc822 or message/global, they might contain From fields which could 635 have different values to that of the top-level From field and may not 636 reflect the actual sender. The inconsistent From field values might 637 get shown to the recipient in a non-conforming email client and may 638 mislead the recipient into thinking that the email came from someone 639 other than the real sender. 641 12. Changes from Previous Versions 643 12.1. Changes from draft-tomkinson-multilangcontent-01 to draft- 644 tomkinson-slim-multilangcontent-00 646 o File name and version number changed to reflect the proposed WG 647 name SLIM (Selection of Language for Internet Media). 649 o Replaced the Subject-Translation field in the language message 650 parts with Subject and provided US-ASCII and non-US-ASCII 651 examples. 653 o Introduced the language-independent message part. 655 o Many wording improvements and clarifications throughout the 656 document. 658 12.2. Changes from draft-tomkinson-slim-multilangcontent-00 to draft- 659 tomkinson-slim-multilangcontent-01 661 o Added Translation-Type in each language message part to identify 662 the source of the translation (original/human/automated). 664 12.3. Changes from draft-tomkinson-slim-multilangcontent-01 to draft- 665 tomkinson-slim-multilangcontent-02 667 o Changed Translation-Type to be a parameter for the Content- 668 Language field rather than a new separate field. 670 o Added a paragraph about using Content-Disposition field to help 671 non-conforming mail clients correctly render the multilingual 672 preface. 674 o Recommended using a Name parameter on the language part Content- 675 Type to help the recipient identify the translations in non- 676 conforming mail clients. 678 o Many wording improvements and clarifications throughout the 679 document. 681 12.4. Changes from draft-tomkinson-slim-multilangcontent-02 to draft- 682 ietf-slim-multilangcontent-00 684 o Name change to reflect the draft being accepted into SLIM as a 685 working group document. 687 o Updated examples to use UTF-8 encoding where required. 689 o Removed references to 'locale' for identifying language 690 preference. 692 o Recommended language matching schemes from RFC 4647 [RFC4647]. 694 o Renamed the unmatched part to language independent part to 695 reinforce its intended purpose. 697 o Added requirement for using Content-Language: zxx in the language 698 independent part. 700 o Many wording improvements and clarifications throughout the 701 document. 703 12.5. Changes from draft-ietf-slim-multilangcontent-00 to draft-ietf- 704 slim-multilangcontent-01 706 o Changed the inner content type to require message/rfc822 or 707 message/global. 709 o Updated the examples to reflect the new inner content types. 711 o Added to the security considerations to highlight the risk from 712 insufficient spam filters. 714 12.6. Changes from draft-ietf-slim-multilangcontent-01 to draft-ietf- 715 slim-multilangcontent-02 717 o Restricted the use of a From field in the language message parts 718 and the language independent part. 720 o Updated the security considerations to highlight the risk of an 721 unmatched sender addresses that could be set in the language 722 message parts. 724 12.7. Changes from draft-ietf-slim-multilangcontent-02 to draft-ietf- 725 slim-multilangcontent-03 727 o Relaxed the restriction on the use of the From field in the 728 language message parts to allow a localised version of the 729 sender's display name. 731 12.8. Changes from draft-ietf-slim-multilangcontent-03 to draft-ietf- 732 slim-multilangcontent-04 734 o Updated the wording of the security considerations section to 735 reflect the relaxation of the use of the From field in the 736 language message parts. 738 12.9. Changes from draft-ietf-slim-multilangcontent-04 to draft-ietf- 739 slim-multilangcontent-05 741 o Referenced the RFC for message/global in Language Message Parts 742 section. 744 o Removed RFC 2119 keyword in the Message Part Selection section. 746 o Included full email addresses in all examples. 748 o Updated reference name of real-time companion document in the 749 Introduction. 751 o Removed paragraph warning of over use of language sub-tags. 753 o Changed 'exponential' to 'significantly' in Introduction. 755 12.10. Changes from draft-ietf-slim-multilangcontent-05 to draft-ietf- 756 slim-multilangcontent-06 758 o Changed parameter Translation-Type back to a new field to reduce 759 the risk of breaking existing implementations that don't expect 760 any parameters on Content-Language. 762 o Improved the IANA Considerations section to include the full 763 registration template for the multipart/multilingual type and the 764 new Translation-Type field. 766 12.11. Changes from draft-ietf-slim-multilangcontent-06 to draft-ietf- 767 slim-multilangcontent-07 769 o Updated the Encoding Considerations in the IANA Registration 770 Template. 772 12.12. Changes from draft-ietf-slim-multilangcontent-07 to draft-ietf- 773 slim-multilangcontent-08 775 o Reordered the sections to make the Security Considerations easier 776 to find. 778 o Shortened a line in one of the examples that was longer than 72 779 characters. 781 o Updated the link to the real-time companion document to the latest 782 version. 784 12.13. Changes from draft-ietf-slim-multilangcontent-08 to draft-ietf- 785 slim-multilangcontent-09 787 o Removed the phrase "and SHOULD NOT have a Subject field and SHOULD 788 NOT have a From field" in section 3.3 because the language 789 independent part would be message/rfc822 or message/global so it 790 is likely to have From and Subject fields. 792 o For the same reason as above, the phrase "(for example if the 793 language independent part is selected)" was removed from section 794 7. 796 o Phrase in part 3.3 was reworded from "This could typically be a 797 language independent graphic" to "This could typically include a 798 language independent graphic". 800 12.14. Changes from draft-ietf-slim-multilangcontent-09 to draft-ietf- 801 slim-multilangcontent-10 803 o Added Normative Reference to RFC 3629 for details of UTF-8 in the 804 Multilingual Preface section. 806 o Added ABNF for Translation-Type field. 808 o Updated example 2 to contain a image/png language independent 809 image directly rather than it being nested inside multipart/mixed 810 content. 812 o Inserted Change Controller into IANA template for multipart/ 813 multilingual. 815 o Replaced references to "This document" with RFC XXXX in the IANA 816 considerations. 818 13. References 820 13.1. Normative References 822 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 823 Extensions (MIME) Part Two: Media Types", RFC 2046, 824 DOI 10.17487/RFC2046, November 1996, 825 . 827 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 828 Part Three: Message Header Extensions for Non-ASCII Text", 829 RFC 2047, DOI 10.17487/RFC2047, November 1996, 830 . 832 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 833 Requirement Levels", BCP 14, RFC 2119, 834 DOI 10.17487/RFC2119, March 1997, 835 . 837 [RFC2183] Troost, R., Dorner, S., and K. Moore, Ed., "Communicating 838 Presentation Information in Internet Messages: The 839 Content-Disposition Header Field", RFC 2183, 840 DOI 10.17487/RFC2183, August 1997, 841 . 843 [RFC3282] Alvestrand, H., "Content Language Headers", RFC 3282, 844 DOI 10.17487/RFC3282, May 2002, 845 . 847 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 848 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 849 2003, . 851 [RFC4647] Phillips, A. and M. Davis, "Matching of Language Tags", 852 BCP 47, RFC 4647, DOI 10.17487/RFC4647, September 2006, 853 . 855 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 856 Specifications: ABNF", STD 68, RFC 5234, 857 DOI 10.17487/RFC5234, January 2008, 858 . 860 [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, 861 DOI 10.17487/RFC5322, October 2008, 862 . 864 [RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying 865 Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646, 866 September 2009, . 868 [RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized 869 Email Headers", RFC 6532, DOI 10.17487/RFC6532, February 870 2012, . 872 13.2. Informational References 874 [I-D.ietf-slim-negotiating-human-language] 875 Gellens, R., "Negotiating Human Language in Real-Time 876 Communications", draft-ietf-slim-negotiating-human- 877 language-13 (work in progress), July 2017. 879 Authors' Addresses 880 Nik Tomkinson 881 Mimecast Ltd 882 CityPoint, One Ropemaker Street 883 London EC2Y 9AW 884 United Kingdom 886 Email: rfc.nik.tomkinson@gmail.com 888 Nathaniel Borenstein 889 Mimecast Ltd 890 480 Pleasant Street 891 Watertown MA 02472 892 North America 894 Email: nsb@mimecast.com