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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-03) exists of draft-gellens-slim-negotiating-human-language-02 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). 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: January 9, 2017 July 8, 2016 7 Multiple Language Content Type 8 draft-ietf-slim-multilangcontent-01 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 January 9, 2017. 35 Copyright Notice 37 Copyright (c) 2016 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 exponentially. 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.gellens-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 parameter of the Content-Language field instead of 99 the ordering of the parts and the 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 encoding is used for this message part. 139 Whilst this section of the message is useful for backward 140 compatibility, it will normally only be shown when rendered by a non- 141 conforming email client, because conforming email clients SHOULD only 142 show the single language message part identified by the user's 143 preferred language and the language message part's Content-Language. 145 For the correct display of the multilingual preface in a non- 146 conforming email client, the sender MAY use the Content-Disposition 147 field with a value of 'inline' in conformance with RFC 2183 [RFC2183] 148 (which defines the Content-Disposition field). If provided, this 149 SHOULD be placed at the multipart/multilingual level and in the 150 multilingual preface. This makes it clear to a non-conforming email 151 client that the multilingual preface should be displayed immediately 152 to the recipient, followed by any subsequent parts marked as 153 'inline'. 155 For an example of a multilingual preface, see the examples in 156 Section 8. 158 3.2. The Language Message Parts 160 The language message parts are typically translations of the same 161 message content. These message parts SHOULD be ordered so that the 162 first part after the multilingual preface is in the language believed 163 to be the most likely to be recognised by the recipient as this will 164 constitute the default part when language negotiation fails and there 165 is no Language Independent part. All of the language message parts 166 MUST have a Content-Language field and a Content-Type field and MAY 167 have a Translation-Type parameter applied to the Content-Language 168 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 when 173 support for message/global becomes more commonplace. Each language 174 message part SHOULD have a Subject field in the appropriate language 175 for that language part. 177 3.3. The Language Independent Message Part 179 If there is language independent content intended for the recipient 180 to see if they have a preferred language other than one of those 181 specified in the language message parts and the default language 182 message part is unlikely to be understood, another part MAY be 183 provided. This could typically be a language independent graphic. 184 When this part is present, it MUST be the last part, MUST have a 185 Content-Language field with a value of "zxx" (as described in BCP 47/ 186 RFC 5646 [RFC5646]) and SHOULD NOT have a Subject field. The part 187 SHOULD have a Content-Type of message/rfc822 or message/global (to 188 match the language message parts). 190 4. Message Part Selection 192 The logic for selecting the message part to render and present to the 193 recipient is summarised in the next few paragraphs. 195 Firstly, if the email client does not understand multipart/ 196 multilingual then it SHOULD treat the message as if it was multipart/ 197 mixed and render message parts accordingly. 199 If the email client does understand multipart/multilingual then it 200 SHOULD ignore the multilingual preface and select the best match for 201 the user's preferred language from the language message parts 202 available. Also, the user may prefer to see the original message 203 content in their second language over a machine translation in their 204 first language. The Translation-Type parameter of the Content- 205 Language field value can be used for further selection based on this 206 preference. The selection of language part may be implemented in a 207 variety of ways, although the matching schemes detailed in RFC 4647 208 [RFC4647] are RECOMMENDED as a starting point for an implementation. 209 The goal is to render the most appropriate translation for the user. 211 If there is no match for the user's preferred language (or there is 212 no preferred language information available) the email client SHOULD 213 select the language independent part (if one exists) or the first 214 language part (directly after the multilingual preface) if a language 215 independent part does not exist. 217 If there is no translation type preference information available, the 218 values of the Translation-Type parameter may be ignored. 220 Additionally, interactive implementations MAY offer the user a choice 221 from among the available languages. 223 5. The Content-Language Field 225 The Content-Language field in the individual language message parts 226 is used to identify the language in which the message part is 227 written. Based on the value of this field, a conforming email client 228 can determine which message part to display (given the user's 229 language settings). 231 The Content-Language MUST comply with RFC 3282 [RFC3282] (which 232 defines the Content-Language field) and BCP 47/RFC 5646 [RFC5646] 233 (which defines the structure and semantics for the language code 234 values). While RFC 5646 provides a mechanism accommodating 235 increasingly fine-grained distinctions, in the interest of maximum 236 interoperability, each Content-Language value SHOULD be restricted to 237 the largest granularity of language tags; in other words, it is 238 RECOMMENDED to specify only a Primary-subtag and NOT to include 239 subtags (e.g., for region or dialect) unless the languages might be 240 mutually incomprehensible without them. Examples of this field for 241 English, German and an instruction manual in Spanish and French, 242 could look like the following: 244 Content-Language: en 246 Content-Language: de 248 Content-Language: es, fr 250 6. The Translation-Type Parameter 252 The Translation-Type parameter can be applied to the Content-Language 253 field in the individual language message parts and is used to 254 identify the type of translation. Based on the value of this 255 parameter and the user's preferences, a conforming email client can 256 determine which message part to display. 258 This parameter can have one of three possible values: 'original', 259 'human' or 'automated' although other values may be added in the 260 future. A value of 'original' is given in the language message part 261 that is in the original language. A value of 'human' is used when a 262 language message part is translated by a human translator or a human 263 has checked and corrected an automated translation. A value of 264 'automated' is used when a language message part has been translated 265 by an electronic agent without proofreading or subsequent correction. 267 Examples of this parameter include: 269 Content-Language: en; translation-type=original 271 Content-Language: fr; translation-type=human 273 7. The Subject Field in the Language Message parts 275 On receipt of the message, conforming email clients will need to 276 render the subject in the correct language for the recipient. To 277 enable this the Subject field SHOULD be provided in each language 278 message part. The value for this field should be a translation of 279 the email subject. 281 US-ASCII and 'encoded-word' examples of this field include: 283 Subject: A really simple email subject 284 Subject: =?UTF-8?Q?Un_asunto_de_correo_electr=C3=b3nico_ 285 realmente_sencillo?= 287 See RFC 2047 [RFC2047] for the specification of 'encoded-word'. 289 The subject to be presented to the recipient should be selected from 290 the message part identified during the message part selection stage. 291 If no Subject field is found (for example if the language independent 292 part is selected) the top-level Subject header field value should be 293 used. 295 8. Examples 297 8.1. An Example of a Simple Multiple language email message 299 Below is a minimal example of a multiple language email message. It 300 has the multilingual preface and two language message parts. 302 From: Nik 303 To: Nathaniel 304 Subject: Example of a message in Spanish and English 305 Date: Thu, 7 Jul 2016 21:28:00 +0100 306 MIME-Version: 1.0 307 Content-type: multipart/multilingual; 308 boundary="01189998819991197253" 310 --01189998819991197253 311 Content-type: text/plain; charset="UTF-8" 312 Content-Disposition: inline 313 Content-transfer-encoding: quoted-printable 315 This is a message in multiple languages. It says the 316 same thing in each language. If you can read it in one language, 317 you can ignore the other translations. The other translations may be 318 presented as attachments or grouped together. 320 Este es un mensaje en varios idiomas. Dice lo mismo en 321 cada idioma. Si puede leerlo en un idioma, puede ignorar las otras 322 traducciones. Las otras traducciones pueden presentarse como archivos 323 adjuntos o agrupados. 325 --01189998819991197253 326 Content-type: message/rfc822 327 Content-Language: en; translation-type=original 328 Content-disposition: inline 330 Subject: Example of a message in Spanish and English 331 Content-Type: text/plain; charset="US-ASCII" 332 Content-Transfer-Encoding: 7bit 333 MIME-Version: 1.0 335 Hello, this message content is provided in your language. 337 --01189998819991197253 338 Content-type: message/rfc822 339 Content-Language: es; translation-type=human 340 Content-disposition: inline 342 Subject: =?UTF-8?Q?Ejemplo_pr=C3=A1ctico_de_mensaje_?= 343 =?UTF-8?Q?en_espa=C3=B1ol_e_ingl=C3=A9s?= 344 Content-Type: text/plain; charset="US-ASCII" 345 Content-Transfer-Encoding: 7bit 346 MIME-Version: 1.0 348 Hola, el contenido de este mensaje esta disponible en su idioma. 350 --01189998819991197253-- 352 8.2. An Example of a Multiple language email message with language 353 independent part 355 Below is an example of a multiple language email message that has the 356 multilingual preface followed by two language message parts and then 357 a language independent png image. 359 From: Nik 360 To: Nathaniel 361 Subject: Example of a message in Spanish and English 362 Date: Thu, 7 Jul 2016 21:08:00 +0100 363 MIME-Version: 1.0 364 Content-type: multipart/multilingual; 365 boundary="01189998819991197253" 367 --01189998819991197253 368 Content-type: text/plain; charset="UTF-8" 369 Content-Disposition: inline 370 Content-transfer-encoding: quoted-printable 372 This is a message in multiple languages. It says the 373 same thing in each language. If you can read it in one language, 374 you can ignore the other translations. The other translations may be 375 presented as attachments or grouped together. 377 Este es un mensaje en varios idiomas. Dice lo mismo en 378 cada idioma. Si puede leerlo en un idioma, puede ignorar las otras 379 traducciones. Las otras traducciones pueden presentarse como archivos 380 adjuntos o agrupados. 382 --01189998819991197253 383 Content-type: message/rfc822 384 Content-Language: en; translation-type=original 385 Content-disposition: inline 387 Subject: Example of a message in Spanish and English 388 Content-Type: text/plain; charset="US-ASCII" 389 Content-Transfer-Encoding: 7bit 390 MIME-Version: 1.0 392 Hello, this message content is provided in your language. 394 --01189998819991197253 395 Content-type: message/rfc822 396 Content-Language: es; translation-type=human 397 Content-disposition: inline 399 Subject: =?UTF-8?Q?Ejemplo_pr=C3=A1ctico_de_mensaje_?= 400 =?UTF-8?Q?en_espa=C3=B1ol_e_ingl=C3=A9s?= 401 Content-Type: text/plain; charset="US-ASCII" 402 Content-Transfer-Encoding: 7bit 403 MIME-Version: 1.0 405 Hola, el contenido de este mensaje esta disponible en su idioma. 407 --01189998819991197253 408 Content-type: message/rfc822; name="Icon" 409 Content-Language: zxx 410 Content-disposition: inline 412 Content-Type: multipart/mixed; 413 boundary="99911972530118999881"; charset="US-ASCII" 414 Content-Transfer-Encoding: 7bit 415 MIME-Version: 1.0 417 --99911972530118999881 418 Content-Type: image/png; name="icon.png" 419 Content-Disposition: inline 420 Content-transfer-encoding: base64 422 iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAKQ2lDQ1BJQ0MgUHJvZmlsZQAA 423 SA2dlndUU1... shortened for brevity ...7yxfd1SNsEy+OXr76qr 424 997zF2hvZYeDEP5ftGV6Xzx2o9MAAAAASUVORK5CYII= 426 --99911972530118999881-- 427 --01189998819991197253-- 428 8.3. An Example of a complex Multiple language email message with 429 language independent part 431 Below is an example of a more complex multiple language email 432 message. It has the multilingual preface and two language message 433 parts and then a language independent png image. The language 434 message parts have multipart/alternative contents and would therefore 435 require further processing to determine the content to display. 437 From: Nik 438 To: Nathaniel 439 Subject: Example of a message in Spanish and English 440 Date: Thu, 7 Jul 2016 20:55:00 +0100 441 MIME-Version: 1.0 442 Content-type: multipart/multilingual; 443 boundary="01189998819991197253" 445 --01189998819991197253 446 Content-type: text/plain; charset="UTF-8" 447 Content-Disposition: inline 448 Content-transfer-encoding: quoted-printable 450 This is a message in multiple languages. It says the 451 same thing in each language. If you can read it in one language, 452 you can ignore the other translations. The other translations may be 453 presented as attachments or grouped together. 455 Este es un mensaje en varios idiomas. Dice lo mismo en 456 cada idioma. Si puede leerlo en un idioma, puede ignorar las otras 457 traducciones. Las otras traducciones pueden presentarse como archivos 458 adjuntos o agrupados. 460 --01189998819991197253 461 Content-type: message/rfc822 462 Content-Language: en; translation-type=original 463 Content-disposition: inline 465 Subject: Example of a message in Spanish and English 466 Content-Type: multipart/alternative; 467 boundary="72530118999911999881"; charset="US-ASCII" 468 Content-Transfer-Encoding: 7bit 469 MIME-Version: 1.0 471 --72530118999911999881 472 Content-Type: text/plain; charset="US-ASCII" 473 Content-Transfer-Encoding: 7bit 475 Hello, this message content is provided in your language. 477 --72530118999911999881 478 Content-Type: text/html; charset="US-ASCII" 479 Content-Transfer-Encoding: 7bit 481 Hello, this message content is provided in your language. 483 --72530118999911999881-- 484 --01189998819991197253 485 Content-type: message/rfc822 486 Content-Language: es; translation-type=human 487 Content-disposition: inline 489 Subject: =?UTF-8?Q?Ejemplo_pr=C3=A1ctico_de_mensaje_?= 490 =?UTF-8?Q?en_espa=C3=B1ol_e_ingl=C3=A9s?= 491 Content-Type: multipart/alternative; 492 boundary="53011899989991197281"; charset="US-ASCII" 493 Content-Transfer-Encoding: 7bit 494 MIME-Version: 1.0 496 --53011899989991197281 497 Content-Type: text/plain; charset="US-ASCII" 498 Content-Transfer-Encoding: 7bit 500 Hola, el contenido de este mensaje esta disponible en su idioma. 502 --53011899989991197281 503 Content-Type: text/html; charset="US-ASCII" 504 Content-Transfer-Encoding: 7bit 506 Hola, el contenido de este mensaje esta 507 disponible en su idioma. 509 --53011899989991197281-- 510 --01189998819991197253 511 Content-type: message/rfc822; name="Icon" 512 Content-Language: zxx 513 Content-disposition: inline 515 Content-Type: multipart/mixed; 516 boundary="99911972530118999881"; charset="US-ASCII" 517 Content-Transfer-Encoding: 7bit 518 MIME-Version: 1.0 520 --99911972530118999881 521 Content-Type: image/png; name="icon.png" 522 Content-Disposition: inline 523 Content-transfer-encoding: base64 524 iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAKQ2lDQ1BJQ0MgUHJvZmlsZQAA 525 SA2dlndUU1... shortened for brevity ...7yxfd1SNsEy+OXr76qr 526 997zF2hvZYeDEP5ftGV6Xzx2o9MAAAAASUVORK5CYII= 528 --99911972530118999881-- 529 --01189998819991197253-- 531 9. Changes from Previous Versions 533 9.1. Changes from draft-tomkinson-multilangcontent-01 to draft- 534 tomkinson-slim-multilangcontent-00 536 o File name and version number changed to reflect the proposed WG 537 name SLIM (Selection of Language for Internet Media). 539 o Replaced the Subject-Translation field in the language message 540 parts with Subject and provided US-ASCII and non-US-ASCII 541 examples. 543 o Introduced the language-independent message part. 545 o Many wording improvements and clarifications throughout the 546 document. 548 9.2. Changes from draft-tomkinson-slim-multilangcontent-00 to draft- 549 tomkinson-slim-multilangcontent-01 551 o Added Translation-Type in each language message part to identify 552 the source of the translation (original/human/automated). 554 9.3. Changes from draft-tomkinson-slim-multilangcontent-01 to draft- 555 tomkinson-slim-multilangcontent-02 557 o Changed Translation-Type to be a parameter for the Content- 558 Language field rather than a new separate field. 560 o Added a paragraph about using Content-Disposition field to help 561 non-conforming mail clients correctly render the multilingual 562 preface. 564 o Recommended using a Name parameter on the language part Content- 565 Type to help the recipient identify the translations in non- 566 conforming mail clients. 568 o Many wording improvements and clarifications throughout the 569 document. 571 9.4. Changes from draft-tomkinson-slim-multilangcontent-02 to draft- 572 ietf-slim-multilangcontent-00 574 o Name change to reflect the draft being accepted into SLIM as a 575 working group document. 577 o Updated examples to use UTF-8 encoding where required. 579 o Removed references to 'locale' for identifying language 580 preference. 582 o Recommended language matching schemes from RFC 4647 [RFC4647]. 584 o Renamed the unmatched part to language independent part to 585 reinforce its intended purpose. 587 o Added requirement for using Content-Language: zxx in the language 588 independent part. 590 o Many wording improvements and clarifications throughout the 591 document. 593 9.5. Changes from draft-ietf-slim-multilangcontent-00 to draft-ietf- 594 slim-multilangcontent-01 596 o Changed the inner content type to require message/rfc822 or 597 message/global. 599 o Updated the examples to reflect the new inner content types. 601 o Added to the security considerations to highlight the risk from 602 insufficient spam filters. 604 10. Acknowledgements 606 The authors are grateful for the helpful input received from many 607 people but would especially like to acknowledge the help of Harald 608 Alvestrand, Stephane Bortzmeyer, Eric Burger, Mark Davis, Doug Ewell, 609 Randall Gellens, Gunnar Hellstrom, Sean Leonard, John Levine, Alexey 610 Melnikov, Addison Phillips, Pete Resnick, Fiona Tomkinson, Simon 611 Tyler and Daniel Vargha. 613 The authors would also like to thank Fernando Alvaro and Luis de 614 Pablo for their work on the Spanish translations. 616 11. IANA Considerations 618 The multipart/multilingual MIME type will be registered with IANA. 620 12. Security Considerations 622 Whilst it is intended that each language message part is a direct 623 translation of the original message, this may not always be the case 624 and these parts could contain undesirable content. Therefore there 625 is a possible risk that undesirable text or images could be shown to 626 the recipient if the message is passed through a spam filter that 627 does not check all of the message parts. The risk should be minimal 628 due to the fact that an unknown multipart subtype should be treated 629 as multipart/mixed and so each message part should be subsequently 630 scanned. 632 13. References 634 13.1. Normative References 636 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail 637 Extensions (MIME) Part Two: Media Types", RFC 2046, 638 DOI 10.17487/RFC2046, November 1996, 639 . 641 [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) 642 Part Three: Message Header Extensions for Non-ASCII Text", 643 RFC 2047, DOI 10.17487/RFC2047, November 1996, 644 . 646 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 647 Requirement Levels", BCP 14, RFC 2119, 648 DOI 10.17487/RFC2119, March 1997, 649 . 651 [RFC2183] Troost, R., Dorner, S., and K. Moore, Ed., "Communicating 652 Presentation Information in Internet Messages: The 653 Content-Disposition Header Field", RFC 2183, 654 DOI 10.17487/RFC2183, August 1997, 655 . 657 [RFC3282] Alvestrand, H., "Content Language Headers", RFC 3282, 658 DOI 10.17487/RFC3282, May 2002, 659 . 661 [RFC4647] Phillips, A. and M. Davis, "Matching of Language Tags", 662 BCP 47, RFC 4647, DOI 10.17487/RFC4647, September 2006, 663 . 665 [RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying 666 Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646, 667 September 2009, . 669 13.2. Informational References 671 [I-D.gellens-slim-negotiating-human-language] 672 Gellens, R., "Negotiating Human Language in Real-Time 673 Communications", draft-gellens-slim-negotiating-human- 674 language-02 (work in progress), July 2015. 676 Authors' Addresses 678 Nik Tomkinson 679 Mimecast Ltd 680 CityPoint, One Ropemaker Street 681 London EC2Y 9AW 682 United Kingdom 684 Email: rfc.nik.tomkinson@gmail.com 686 Nathaniel Borenstein 687 Mimecast Ltd 688 480 Pleasant Street 689 Watertown MA 02472 690 North America 692 Email: nsb@mimecast.com