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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 URNBIS P. Saint-Andre 3 Internet-Draft Filament 4 Obsoletes: 2141, 3406 (if approved) J. Klensin 5 Intended status: Standards Track June 27, 2016 6 Expires: December 29, 2016 8 Uniform Resource Names (URNs) 9 draft-ietf-urnbis-rfc2141bis-urn-17 11 Abstract 13 A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI) 14 that is assigned under the "urn" scheme and a particular URN 15 namespace, with the intent that the URN will be either a persistent, 16 location-independent resource identifier or in some cases an abstract 17 designator that is persistent but that does not identify a resource. 18 With regard to URN syntax, this document defines the canonical syntax 19 for URNs (in a way that is consistent with URI syntax), specifies 20 methods for determining URN equivalence, and discusses URI 21 conformance. With regard to URN namespaces, this document specifies 22 a method for defining a URN namespace and associating it with a 23 namespace identifier, and describes procedures for registering 24 namespace identifiers with the Internet Assigned Numbers Authority 25 (IANA). This document obsoletes both RFC 2141 and RFC 3406. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on December 29, 2016. 44 Copyright Notice 46 Copyright (c) 2016 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 This document may contain material from IETF Documents or IETF 60 Contributions published or made publicly available before November 61 10, 2008. The person(s) controlling the copyright in some of this 62 material may not have granted the IETF Trust the right to allow 63 modifications of such material outside the IETF Standards Process. 64 Without obtaining an adequate license from the person(s) controlling 65 the copyright in such materials, this document may not be modified 66 outside the IETF Standards Process, and derivative works of it may 67 not be created outside the IETF Standards Process, except to format 68 it for publication as an RFC or to translate it into languages other 69 than English. 71 Table of Contents 73 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 74 1.1. Specificity and this Standard . . . . . . . . . . . . . . 5 75 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 76 2. URN Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 6 77 2.1. Namespace Identifier (NID) . . . . . . . . . . . . . . . 7 78 2.2. Namespace Specific String (NSS) . . . . . . . . . . . . . 8 79 2.3. Optional Components . . . . . . . . . . . . . . . . . . . 9 80 2.3.1. q-component . . . . . . . . . . . . . . . . . . . . . 9 81 2.3.2. r-component . . . . . . . . . . . . . . . . . . . . . 11 82 2.3.3. f-component . . . . . . . . . . . . . . . . . . . . . 12 83 3. URN Equivalence . . . . . . . . . . . . . . . . . . . . . . . 13 84 3.1. Procedure . . . . . . . . . . . . . . . . . . . . . . . . 13 85 3.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 14 86 4. URI Conformance . . . . . . . . . . . . . . . . . . . . . . . 15 87 4.1. Use in URI Protocol Slots . . . . . . . . . . . . . . . . 15 88 4.2. Parsing . . . . . . . . . . . . . . . . . . . . . . . . . 16 89 4.3. URNs and Relative References . . . . . . . . . . . . . . 16 90 4.4. Transport and Display . . . . . . . . . . . . . . . . . . 17 91 4.5. URI Design and Ownership . . . . . . . . . . . . . . . . 17 92 5. URN Namespaces . . . . . . . . . . . . . . . . . . . . . . . 18 93 5.1. Formal Namespaces . . . . . . . . . . . . . . . . . . . . 19 94 5.2. Informal Namespaces . . . . . . . . . . . . . . . . . . . 21 95 6. Defining and Registering a URN Namespace . . . . . . . . . . 21 96 6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 21 97 6.2. Registration Policy and Process: Community Registrations 22 98 6.3. Registration Policy and Process: Fast Track for Standards 99 Development Organizations, Scientific Societies, and 100 Similar Bodies . . . . . . . . . . . . . . . . . . . . . 23 101 6.4. Completing the Template . . . . . . . . . . . . . . . . . 24 102 6.4.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . 24 103 6.4.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . 25 104 6.4.3. Assignment . . . . . . . . . . . . . . . . . . . . . 26 105 6.4.4. Security and Privacy . . . . . . . . . . . . . . . . 26 106 6.4.5. Interoperability . . . . . . . . . . . . . . . . . . 27 107 6.4.6. Resolution . . . . . . . . . . . . . . . . . . . . . 27 108 6.4.7. Additional Information . . . . . . . . . . . . . . . 27 109 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 110 7.1. URI Scheme . . . . . . . . . . . . . . . . . . . . . . . 27 111 7.2. Registration of URN Namespaces . . . . . . . . . . . . . 28 112 8. Security and Privacy Considerations . . . . . . . . . . . . . 28 113 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 29 114 9.1. Normative References . . . . . . . . . . . . . . . . . . 29 115 9.2. Informative References . . . . . . . . . . . . . . . . . 29 116 Appendix A. Registration Template . . . . . . . . . . . . . . . 31 117 Appendix B. Changes from RFC 2141 . . . . . . . . . . . . . . . 33 118 B.1. Syntax changes from RFC 2141 . . . . . . . . . . . . . . 33 119 B.2. Other changes from RFC 2141 . . . . . . . . . . . . . . . 33 120 Appendix C. Changes from RFC 3406 . . . . . . . . . . . . . . . 34 121 Appendix D. Contributors . . . . . . . . . . . . . . . . . . . . 34 122 Appendix E. Acknowledgements . . . . . . . . . . . . . . . . . . 34 123 Appendix F. Change log for versions of draft-ietf-urnbis- 124 rfc2141bis-urn . . . . . . . . . . . . . . . . . . . 35 125 F.1. Changes from -08 to -09 . . . . . . . . . . . . . . . . . 35 126 F.2. Changes from -09 to -10 . . . . . . . . . . . . . . . . . 35 127 F.3. Changes from -10 to -11 . . . . . . . . . . . . . . . . . 36 128 F.4. Changes from -11 to -12 . . . . . . . . . . . . . . . . . 36 129 F.5. Changes from -12 to -13 . . . . . . . . . . . . . . . . . 36 130 F.6. Changes from -13 to -14 . . . . . . . . . . . . . . . . . 37 131 F.7. Changes from -14 to -15 . . . . . . . . . . . . . . . . . 37 132 F.8. Changes from -15 (2016-02-04) to -16 . . . . . . . . . . 37 133 F.9. Changes from -16 (2016-04-16) to -17 . . . . . . . . . . 38 134 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39 136 1. Introduction 138 A Uniform Resource Name (URN) is a Uniform Resource Identifier (URI) 139 [RFC3986] that is assigned under the "urn" scheme and a particular 140 namespace, with the intent that the URN will be either a persistent, 141 location-independent resource identifier or in some cases an abstract 142 designator that is persistent but that does not identify a resource. 143 A URN namespace is a collection of such identifiers, each of which is 144 (1) unique, (2) assigned in a consistent and managed way, and (3) 145 assigned according to a common definition. (Some URN namespaces 146 create names that exist only as URNs, whereas others create URNs out 147 of names that already exist in other identifier systems, such as 148 ISBNs [RFC3187] and ISSNs [RFC3044].) 150 The assignment of URNs is done by an organization (or, in some cases, 151 according to an algorithm or other automated process) that has been 152 formally delegated a namespace within the "urn" scheme (e.g., a URN 153 in the 'example' namespace [RFC6963] might be of the form 154 "urn:example:foo"). 156 This document rests on two key assumptions: 158 1. Assignment of a URN is a managed process. 160 2. The space of URN namespaces is itself managed. 162 While other URI schemes may allow identifiers to be freely chosen and 163 assigned, such is not the case for URNs. The syntactical correctness 164 of a string starting with "urn:" is not sufficient to make it a URN. 165 In order for the string to be a valid URN, the namespace identifier 166 needs to be registered in accordance with the rules defined here and 167 the remaining parts of the assigned-name portion of the URN needs to 168 be generated in accordance with the rules for the registered 169 namespace. 171 So that information about both URN syntax and URN namespaces is 172 available in one place, this document does the following: 174 1. Defines the canonical syntax for URNs in general (in a way that 175 is consistent with URI syntax), specifies methods for determining 176 URN equivalence, and discusses URI conformance. 178 2. Specifies a method for defining a URN namespace and associating 179 it with a namespace identifier, and describes procedures for 180 registering namespace identifiers with the Internet Assigned 181 Numbers Authority (IANA). 183 For URN syntax and URN namespaces, this document modernizes and 184 replaces the definitions from the original URN syntax [RFC2141] and 185 namespace definition and registration [RFC3406] specifications. 186 These modifications build on the key requirements provided in the 187 original functional description for URN [RFC1737] and many years of 188 experience. In both those original documents and the present one, 189 the intent is to define URNs in a consistent manner so that, wherever 190 practical, the parsing, handling, and resolution of URNs can be 191 independent of the namespace within which a given URN is assigned. 193 Together with input from several key user communities, the history 194 and experiences dictated expansion of the URN definition to support 195 new functionality, including the use of syntax explicitly reserved 196 for future standardization in RFC 2141. All namespaces and URNs that 197 were valid under the earlier specifications remain valid even though 198 it may be useful to update some of them to take advantage of new 199 features. 201 Summaries of changes from RFC 2141 and RFC 3406 appear in Appendix B 202 and Appendix C respectively. This document obsoletes both [RFC2141] 203 and [RFC3406]. While it does not explicitly update or replace 204 [RFC1737] or [RFC2276] the reader who references those documents 205 should be aware that the conceptual model of URNs in this document is 206 slightly different from those older specifications. 208 1.1. Specificity and this Standard 210 To a degree much greater than when URNs were first considered and 211 their uses outlined (Cf. [RFC1737]) issues of persistent identifiers 212 on the Internet involve fundamental design tradeoffs and research 213 questions that are much broader that URNs or the URN approach. Ideal 214 and comprehensive specifications about what should be done or 215 required across the entire range of URNs would require general 216 agreement about those issues and their resolution. While some of 217 them were introduced by the Internet or computer-age approaches to 218 character encodings and data abstraction, others predate the Internet 219 and computer systems by centuries; there is unlikely to be agreement 220 about comprehensive solutions in the near future. 222 Among these general issues, one that is specific to URNs is the 223 fairly abstract topic of "resolution", discussed in Section 1.2, 224 Section 2.3.2, and elsewhere below. While it is possible to define 225 the relationships quite precisely for a URN that resolves to a URL 226 that, in turn, resolves (or locates) to a single target document or 227 similar resource, that is only one special case albeit an important 228 one. URNs (either individually or entire namespaces as defined 229 below) that do not resolve to URLs at all or that resolve to metadata 230 or non-Internet objects are among URN use cases explicitly permitted 231 by this specification; each leaves the concept of "resolution" 232 somewhat more abstract and difficult than the simple case of 233 resolution to a URL. 235 A similar set of issues arises for character sets and encodings. 236 URNs, especially URNs that will be used as user-facing identifiers, 237 should be convenient to use in local languages and writing systems, 238 easily specified with a wide range of keyboards and local 239 conventions, and unambiguous. There are tradeoffs among those goals 240 and it is impossible at present to see how a simple and readily- 241 understandable set of rules could be developed that would be optimal, 242 or even reasonable, for all URNs. The discussion in Section 2.2 243 defines an overall framework that should make generalized parsing and 244 processing possible, but also makes recommendations about rules for 245 individual namespaces. 247 This specification consequently contains some requirements and 248 flexibility that would not be present in a more perfect world but 249 that are necessary in order to allow producing any consensus 250 specification at all rather than just giving up on URNs going 251 forward. 253 1.2. Terminology 255 This document uses the terms "resolution" and "resolver" in roughly 256 the sense in which they were used in the original discussion of 257 architectural principles for URNs [RFC2276], i.e., "resolution" is 258 the act of supplying services related to the identified resource, 259 such as translating the persistent name into one or more current 260 locators for the resource, delivering metadata about the resource in 261 an appropriate format, or even delivering a document object from a 262 convenient source without requiring further intermediaries. At the 263 time of this writing, resolution services are described in [RFC2483]. 264 In order to underline the difference between the names and locators, 265 this document uses the term Uniform Resource Locator (URL), rather 266 than the generic term Uniform Resource Identifier (URI), to refer to 267 locators; see also Section 1.1.3 of [RFC3986]. 269 If there are or will be resolution services available for a URN, this 270 document calls the URN a "resource identifier" in roughly the sense 271 that term is used in [RFC3986]. If there is no intention to provide 272 any resolution services, and the distinction is important, this 273 document calls the URN an "abstract designator". 275 Several other important terms used in this document, including some 276 "normalization" operations that are not part of the Unicode Standard 277 [UNICODE], are defined in the URI specification [RFC3986]. 279 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 280 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 281 "OPTIONAL" in this document are to be interpreted as described in 282 [RFC2119]. 284 2. URN Syntax 286 As discussed above, the syntax for URNs in this specification allows 287 significantly more functionality than was the case in the earlier 288 specifications. It is also harmonized with the general URI syntax 290 [RFC3986]. That syntax definition was completed after the earlier 291 URN specifications. 293 However, this specification does not extend the URN syntax to allow 294 direct use of characters outside the ASCII range [RFC20]. That 295 prohibition implies that any such characters need to be percent- 296 encoded as described in Section 2.1 of the URI specification 297 [RFC3986]. 299 The basic syntax for a URN is defined using the Augmented Backus-Naur 300 Form (ABNF) as specified in [RFC5234]. Rules not defined here 301 (specifically: alphanum, fragment, and pchar) are defined as part of 302 the URI syntax [RFC3986] and used here to point out the syntactic 303 relationship with the terms used there. The definitions of some of 304 the terms used below are not complete; additional restrictions are 305 imposed sections of the document that are specific to those terms. 307 namestring = assigned-name 308 [ rq-components ] 309 [ "#" f-component ] 310 assigned-name = "urn" ":" NID ":" NSS 311 NID = (alphanum) 0*30(ldh) (alphanum) 312 ldh = alphanum / "-" 313 NSS = pchar *(pchar / "/") 314 rq-components = ( "?=" q-component 315 [ "?+" r-component ] ) / 316 ( "?+" r-component 317 [ "?=" q-component ] ) 318 q-component = pchar *( pchar / "/" / "?" ) 319 r-component = pchar *( pchar / "/" / "?" ) 320 f-component = fragment 322 The question mark character "?" can be used without percent-encoding 323 inside q-components, r-components, and f-components. Other than 324 inside those components a "?" that is not immediately followed by "=" 325 or "+" is not defined for URNs and SHOULD be treated as a syntax 326 error by URN-specific parsers and other processors. 328 The following sections provide additional information about the 329 syntactic elements of URNs. 331 2.1. Namespace Identifier (NID) 333 Namespace Identifiers (NIDs) are case insensitive (e.g., "ISBN" and 334 "isbn" are equivalent). 336 Characters outside the ASCII range [RFC20] are not permitted in NIDs, 337 and no encoding mechanism for such characters is supported. 339 Section 5.1 and Section 5.2 impose additional constraints on the 340 strings that can be used as NIDs, i.e., the syntax shown above is not 341 comprehensive. 343 2.2. Namespace Specific String (NSS) 345 The namespace specific string (NSS) is a unique identifier within a 346 namespace that is assigned and managed in a consistent way and that 347 conforms to the definition of the relevant namespace. The 348 combination of the NID (unique across the entire "urn" scheme) and 349 the NSS (unique within the namespace) ensures that the resulting URN 350 is a globally unique URI. 352 The NSS specified in this document allows characters not permitted by 353 earlier specifications (see Appendix B. In particular, the "/" 354 character, which is now allowed, effectively makes it possible to 355 encapsulate hierarchical identifiers from other naming systems. For 356 instance, consider the hypothetical example of a hierarchical naming 357 system in which the identifiers take the form of a sequence of 358 numbers separated by the "/" character, such as "1/406/47452/2". If 359 the naming authority for such identifiers were to use URNs, it would 360 be natural to place the existing identifiers in the NSS, resulting in 361 URNs such as "urn:example:1/406/47452/2". 363 The changes to the syntax for the NSS do not modify the encoding 364 rules for URN namespaces that were defined in accordance with 365 [RFC2141]. If any such URN namespace that is used outside of the URN 366 context (i.e., as a standalone, non-embedded, identifier space) also 367 allows the use of "/", "~", or "&" in the native form within that 368 identifier space, then the encoding rules for that namespace are not 369 changed by this specification. 371 [[CREF1: Placeholder for call: In his 2016-05-05 12:48 +0000 note, 372 Henry expressed the concern that "name" and "namespace" were not used 373 consistently and/or adequately defined, singling out the following 374 paragraph as an example. Applying his suggested fix will take some 375 thought and no one has followed the comment up on the list, so the 376 text is unchanged so far.]] 378 Depending on the rules governing a namespace, strings that are valid 379 in an NSS associated with that namespace might contain characters 380 that are not allowed by the "pchar" production referenced above 381 (e.g., characters outside the ASCII range or, consistent with the 382 restrictions in RFC 3986, the characters "/", "?", "#", "[", and 383 "]"). While such a string might be a valid name, it is not a valid 384 URN until it has been translated into a conformant NSS. In the case 385 of URNs that are formed from names that exist separately in a 386 standalone identifier space, translation of an identifier from its 387 "native" format to URN format is accomplished by using the 388 canonicalization and encoding methods defined for that URN namespace. 389 Software that is not aware of those namespace-specific 390 canonicalization and encoding rules MUST NOT construct URNs from the 391 names in the standalone identifier space. 393 In particular, with regard to characters outside the ASCII range, 394 URNs that appear in protocols or that are passed between systems MUST 395 use only Unicode characters encoded in UTF-8 and further encoded as 396 required by RFC 3986. To the extent feasible consistent with the 397 requirements of identifiers defined and standardized elsewhere and 398 the principles discussed in Section 1.1, strings SHOULD be restricted 399 to either ASCII letters and digits or to the characters and syntax of 400 some widely-used identifier model such as those of IDNA [RFC5890], 401 PRECIS [RFC7613], or the Unicode Identifier and Pattern Syntax spec 402 [UAX31]. 404 In order to make URNs as stable and persistent as possible when 405 protocols evolve and the environment around them changes, namespaces 406 SHOULD NOT allow characters outside the basic Latin repertoire 407 [RFC20] unless the nature of the particular namespace makes such 408 characters necessary. 410 2.3. Optional Components 412 This specification includes three optional components in the URN 413 syntax. They are known as q-component, r-component, and f-component 414 and are described in more detail below. Because this specification 415 focuses almost exclusively on URN syntax, it does not define detailed 416 semantics of these components for URNs in general. However, each of 417 these components has a distinct role that is independent of the URN 418 and its namespace. It is intended that clients will be able to 419 handle these components uniformly for all URNs. These components MAY 420 be used with URNs from existing namespaces, whether or not a 421 namespace explicitly supports them. However, consistent with the 422 approach taken in RFC 3986, the behavior of a URN that contains 423 components that are undefined or meaningless for a particular 424 namespace or resource is not defined. The following sections 425 describe these optional components and their interpretation in 426 greater detail. 428 2.3.1. q-component 430 The q-component is intended for passing parameters to either the 431 named resource or a system that can supply the requested service, for 432 interpretation by that resource or system. (By contrast, passing 433 parameters to URN resolution services is handled by r-components as 434 described in the next section.) 435 The URN q-component has the same syntax as the URI query component, 436 but is introduced by "?=", not the "?" alone. For URNs which may be 437 resolved to a URL, the semantics of the q-component are identical to 438 those for the query component of that URL. So URN resolvers 439 returning a URL for a URN with a q-component do this by copying the 440 q-component from the URN to the query component of the URL. If the 441 URN does not resolve to a URL the interpretation of the q-component 442 is undefined by this specification. An example of the copying 443 operation appears below. 445 [[CREF2: Placeholder for call: Sean (note dated 2016-06-03 12:31 446 -0700): "I still disagree strongly with the syntax of that paragraph, 447 namely, using "?=" as an introducer anywhere in the q-component.]] 449 If the URN does not resolve to a URL (i.e., is an abstract designator 450 or resolves directly to an object or a non-URL resource designator), 451 the interpretation of the q-component is undefined by this 452 specification. Thus, for URNs which may be resolved to a URL, the 453 semantics of q-component are identical to those for queries to the 454 resource located via that URL. 456 For the sake of consistency with RFC 3986, neither the general syntax 457 nor the semantics of q-components are defined by, or dependent on, 458 the namespace of the URN. In parallel with RFC 3896, specifics of 459 syntax and semantics, e.g., which keywords or terms are meaningful, 460 of course may depend on a particular namespace or even a particular 461 resource. 463 The sequence "?=" introduces the q-component. The q-component 464 terminates when a "?+" sequence (which begins an r-component) or a 465 "#" character (number sign, which begins an f-component) appears. If 466 neither of those appear, the q-component continues to the end of the 467 URN. Note the the q-component itself does not include the "?=" 468 delimier or any terminating delimiter. The characters slash ("/") 469 and question mark ("?") may represent data within the q-component. 470 Note that characters outside the ASCII range [RFC20] MUST be percent- 471 encoded using the method defined in Section 2.1 of the generic URI 472 specification [RFC3986]. 474 As described in Section 3, the q-component SHALL NOT be taken into 475 account when determining URN equivalence. 477 Namespaces and associated information placement in syntax SHOULD be 478 designed to avoid any need for a resolution service to consider the 479 q-component. Namespace-specific and more generic resolution systems 480 MUST NOT require that q-component information be passed to them for 481 processing. 483 Consider the hypothetical example of passing parameters to an 484 application that returns weather reports from different regions or 485 for different time periods. This could perhaps be accomplished by 486 specifying latitude and longitude coordinates and datetimes in the 487 URN's q-component, resulting in URNs such as the following. 489 urn:example:weather?=op=map&lat=39.56 490 &lon=-104.85&datetime=1969-07-21T02:56:15Z 492 If this example resolved to an HTTP URL, the result might look like: 494 https://weatherapp.example?op=map&lat=39.56 495 &lon=-104.85&datetime=1969-07-21T02:56:15Z 497 2.3.2. r-component 499 The r-component is intended for passing parameters to URN resolution 500 services (taken broadly, see Section 1.1) and interpreted by those 501 services. (By contrast, passing parameters to the resources 502 identified by a URN, or to applications that manage such resources, 503 is handled by q-components as described in the previous section.) 505 The URN r-component has no syntactic equivalent in URLs. 507 The sequence "?+" introduces the r-component just as "?=" introduces 508 the q-component as discussed above. The r-component ends with a "?=" 509 sequence (which begins a q-component) or a "#" character (number 510 sign, which begins an f-component). If neither of those appear, the 511 r-component continues to the end of the URN. Note that characters 512 outside the ASCII range [RFC20] MUST be percent-encoded using the 513 method defined in Section 2.1 of the generic URI specification 514 [RFC3986]. 516 As described under Section 3, the r-component SHALL NOT be taken into 517 account when determining URN equivalence. However, the r-component 518 SHALL be supplied along with the URN when presenting a request to a 519 URN resolution service. 521 This document defines only the syntax of the r-component and reserves 522 it for future use. The exact semantics of the r-component and its 523 use in URN resolution protocols are a matter for potential 524 standardization in separate specifications, presumably including 525 specifications that define conventions and a registry for resolution 526 service identifiers. 528 Consider the hypothetical example of passing parameters to a 529 resolution service (say, an ISO alpha-2 country code [ISO3166-1] in 530 order to select the preferred country in which to search for a 531 physical copy of a book). This could perhaps be accomplished by 532 specifying the country code in the r-component, resulting in URNs 533 such as: 535 urn:example:foo-bar-baz-qux?+CCResolve: cc=uk 537 While the above should serve as a general explanation and 538 illustration of the intent for r-components, there are many 539 unresolved issues with them, including their relationship to 540 resolution mechanisms associated with the particular NID and 541 namespace at registration time. Thus r-components SHOULD NOT be used 542 for actual URNs until additional development and standardization work 543 is complete, including specification of any necessary registration 544 mechanisms. 546 2.3.3. f-component 548 [[CREF3: Placeholder for call: AFAICT, we still have people arguing 549 for saying less about f-components while others insisted earlier on 550 saying more after a round of trying to say less. Up to the call, the 551 WG Chairs, and whatever consensus calls might be made, but the 552 current editor's default is that the balance is about as close as we 553 are going to get it.]] 555 The f-component is intended to be interpreted by the client as a 556 specification for a location within, or region of, the named 557 resource. 559 The URN f-component has the same syntax as the URI fragment 560 component. If a URN containing an f-component resolves to a single 561 URL associated with the named resource, the f-component from the URN 562 can be applied (usually by the client) verbatim as the fragment of 563 that URL. If the URN does not resolve to a URL (e.g., is an abstract 564 designator), the interpretation of the f-component is undefined by 565 this specification. Thus, for URNs which may be resolved to a URL, 566 the semantics of f-components are identical to those of fragments for 567 that resource. 569 For the sake of consistency with RFC 3986, neither the general syntax 570 nor the semantics of f-components are defined by, or dependent on, 571 the namespace of the URN. In parallel with RFC 3896, specifics of 572 syntax and semantics, e.g., which keywords or terms are meaningful, 573 of course may depend on a particular namespace or even a particular 574 resource. 576 The f-component is indicated by the presence of a number sign ("#") 577 character and terminated by the end of the URI. Any characters 578 outside the ASCII range [RFC20] that appear in the f-component MUST 579 be percent-encoded using the method defined in Section 2.1 of the 580 generic URI specification [RFC3986]. 582 As described under Section 3, the f-component SHALL NOT be taken into 583 account when determining URN equivalence. 585 Clients SHOULD NOT pass f-components to resolution services unless 586 those services also perform object retrieval and interpretation 587 functions. 589 The f-component is primarily intended to distinguish the constituent 590 parts of resources named by URNs. Thus, for URNs that resolve to 591 URLs of the named resources, the semantics of an f-component are 592 defined by the media type of those resources, not by the namespace. 594 Consider the hypothetical example of obtaining resources that are 595 part of a larger entity (say, the chapters of a book). Each part 596 could be specified in the f-component, resulting in URNs such as: 598 urn:example:foo-bar-baz-qux#somepart 600 3. URN Equivalence 602 3.1. Procedure 604 For various purposes such as caching, it is often desirable to 605 determine if two URNs are "the same". This is done most generally 606 (i.e., independent of the scheme) by testing for equivalence (see 607 Section 6.1 of [RFC3986]). 609 The generic URI specification [RFC3986] is very flexible about 610 equality comparisons, putting the focus on allowing false negatives 611 and avoiding false positives. If comparisons are made in a scheme- 612 independent way, i.e., as URI comparisons only, URNs that this 613 specification considers equal would be rejected. The discussion 614 below applies when the URIs involved are known to be URNs. 616 Two URNs are equivalent (as URNs) if their portions 617 are octet-by-octet equal after applying case normalization (as 618 specified in Section 6.2.2.1 of [RFC3986]) to the following 619 constructs: 621 1. the URI scheme "urn", by conversion to lower case 623 2. the NID, by conversion to lower case 624 3. any percent-encoded characters in the NSS (that is, all character 625 triplets that match the production found in 626 Section 2.1 of the base URI specification [RFC3986]), by 627 conversion to upper case for the digits A-F. 629 Percent-encoded characters MUST NOT be decoded, i.e., percent- 630 encoding normalization (as specified in Section 6.2.2.2 of [RFC3986]) 631 MUST NOT be applied as part of the comparison process. 633 If a q-component, r-component, or f-component (or any combination 634 thereof) are included in a URN, they MUST be ignored for purposes of 635 determining URN equivalence. 637 URN namespace definitions MAY include additional rules for URN 638 equivalence, such as case-insensitivity of the NSS (or parts 639 thereof). Such rules MUST always have the effect of eliminating some 640 of the false negatives obtained by the procedure above and MUST NOT 641 result in treating two URNs as not equivalent if the procedure here 642 says they are equivalent. For related considerations with regard to 643 NID registration, see below. 645 3.2. Examples 647 This section shows a variety of URNs (using the "example" NID defined 648 in [RFC6963]) that highlight the URN equivalence rules. 650 First, because the scheme and NID are case-insensitive, the following 651 URNs are equivalent to each other: 653 o urn:example:a123,z456 655 o URN:example:a123,z456 657 o urn:EXAMPLE:a123,z456 659 Second, because the q-component and f-component are not taken into 660 account for purposes of testing URN equivalence, the following URNs 661 are equivalent to the first three examples above: 663 o urn:example:a123,z456?=abc 665 o urn:example:a123,z456#789 667 o urn:example:a123,z456#abc 669 Third, because the "/" character (and anything that follows it) in 670 the NSS is taken into account for purposes of URN equivalence, the 671 following URNs are not equivalent to each other or to the preceding 672 URNs: 674 o urn:example:a123,z456/foo 676 o urn:example:a123,z456/bar 678 o urn:example:a123,z456/baz 680 Fourth, because of percent-encoding, the following URNs are 681 equivalent only to each other (although %2C is the percent-encoded 682 transformation of "," from the previous examples, such sequences are 683 not decoded for purposes of testing URN equivalence): 685 o urn:example:a123%2Cz456 687 o URN:EXAMPLE:a123%2cz456 689 Fifth, because characters other than percent-encoded sequences in the 690 NSS are treated in a case-sensitive manner (unless otherwise 691 specified for the namespace in question), the following URNs are not 692 equivalent to the first three URNs: 694 o urn:example:A123,z456 696 o urn:example:a123,Z456 698 Sixth, on casual visual inspection of a URN presented in a human- 699 oriented interface the following URN might appear the same as the 700 first three URNs (because U+0430 CYRILLIC SMALL LETTER A can be 701 confused with U+0061 LATIN SMALL LETTER A), but it is not equivalent: 703 o urn:example:%D0%B0123,z456 705 4. URI Conformance 707 4.1. Use in URI Protocol Slots 709 Because a URN is, syntactically, a URI under the "urn" scheme, in 710 theory a URN can be placed in any protocol slot that allows for a URI 711 (e.g., the 'href' and 'src' attributes in HTML, the element 712 in HTML, the 'xml:base' attribute in XML [XML-BASE], and the 'xmlns' 713 attribute in XML for XML namespace names [XML-NAMES]). 715 However, this does not imply that, semantically, it always makes 716 sense in practice to place a URN in a given URI protocol slot; in 717 particular, because a URN might not specify the location of a 718 resource or even point indirectly to one, it might not be appropriate 719 to place a URN in a URI protocol slot that points to a resource 720 (e.g., the aforementioned 'href' and 'src' attributes). 722 Ultimately, guidelines regarding when it is appropriate to use URIs 723 under the "urn" scheme (or any other scheme) are the responsibility 724 of specifications for individual URI protocol slots (e.g., the 725 specification for the 'xml:base' attribute in XML might recommend 726 that it is inappropriate to use URNs in that protocol slot). This 727 specification cannot possibly anticipate all of the relevant cases, 728 and it is not the place of this specification to require or restrict 729 usage for individual protocol slots. 731 4.2. Parsing 733 In part because of the separation of URN semantics from more general 734 URI syntax [I-D.ietf-urnbis-semantics-clarif], generic URI processors 735 need to pay special attention to the parsing and analysis rules of 736 RFC 3986 and, in particular, must treat the URI as opaque unless the 737 scheme and its requirements are recognized. In the latter case, such 738 processors may be in a position to invoke scheme-appropriate 739 processing such as by a URN resolver. The URN resolver can either be 740 an external resolver that the URI resolver knows of, or it can be 741 functionality built into the URI resolver. Note that this 742 requirement might impose constraints on the contexts in which URNs 743 are appropriately used; see Section 4.1. 745 4.3. URNs and Relative References 747 Section 5.2 of [RFC3986] describes an algorithm for converting a URI 748 reference that might be relative to a given base URI into "parsed 749 components" of the target of that reference, which can then be 750 recomposed per RFC 3986 Section 5.3 into a target URI. This 751 algorithm cannot be applied directly to URNs because their syntax 752 does not support the necessary path components. Whenever a URN 753 resolves to a URL which may be used to access the resource, there is 754 a more specific interpretation of q-component and f-component: the 755 q-component is copied verbatim to the query portion of the URL (if 756 that URL scheme supports query), and the f-component is copied 757 verbatim to the fragment portion of the URL. Even though the notion 758 of a URN as a "persistent", "permanent" identifier does not reconcile 759 easily with relative referencing, resources named with URNs may 760 contain relative references that do not apply to the URN itself. 762 Given the foregoing, a relative reference SHOULD NOT be evaluated 763 directly with respect to a URN. Instead, a relative reference SHOULD 764 be evaluated indirectly with respect to one of the following: 766 1. a base URI (other than a URN) declared by the resource itself; or 767 2. a base URI (other than a URN) obtained through the URN resolution 768 process; or 770 3. the URL of the resource as obtained through the URN resolution 771 process 773 (Case 2 permits the resolution process to explicitly supply a base 774 URI if the resource content is supplied directly by the resolution 775 service rather than via an intermediate "location" URI.) 777 If no such base URI exists, use of a relative reference with respect 778 to a URN is an error. Client behavior in this case is undefined. 780 Resolution services SHOULD ensure that a base URI is supplied any 781 time they provide resource content directly to a client. 783 4.4. Transport and Display 785 When URNs are transported and exchanged, they MUST be represented in 786 the format defined herein. Further, all URN-aware applications MUST 787 offer the option of displaying URNs in this canonical form to allow 788 for direct transcription (for example by cut-and-paste techniques). 789 Such applications might support display of URNs in a more human- 790 friendly form and might use a character set that includes characters 791 that are not permitted in URN syntax as defined in this specification 792 (e.g., when displaying URNs to humans, such applications might 793 replace percent-encoded strings with characters from an extended 794 character repertoire such as Unicode [UNICODE]). 796 To minimize user confusion, a URI browser SHOULD display the complete 797 URN (including the "urn" scheme and any components) to ensure that 798 there is no confusion between URN namespace identifiers and URI 799 scheme identifiers. For example, a URI beginning with "urn:xmpp:" 800 [RFC4854] is very different from a URI beginning with "xmpp:" 801 [RFC5122]. Similarly, a potential DOI URI scheme [DOI-URI] is 802 different from, and possibly completely unrelated to, a possible DOI 803 URN namespace. 805 4.5. URI Design and Ownership 807 As mentioned, the assignment of URNs is a managed process, as is the 808 assignment of namespaces themselves. Although design of the URNs to 809 be assigned within a given namespace is ceded by this specification 810 to the namespace owner, doing so in a managed way avoids the problems 811 inherent in unmanaged generation of URIs as described in the 812 recommendations regarding URI design and ownership [RFC7320]. 814 5. URN Namespaces 816 A URN namespace is a collection of identifiers that obey three 817 constraints: each identifier is (1) unique, (2) assigned in a 818 consistent way, and (3) assigned according to a common definition. 820 1. The "uniqueness" constraint means that an identifier within the 821 namespace is never assigned to more than one resource and never 822 reassigned to a different resource (for the kind of "resource" 823 identified by URNs assigned within the namespace). This holds 824 true even if the identifier itself is deprecated or becomes 825 obsolete. 827 2. The "consistent assignment" constraint means that an identifier 828 within the namespace is assigned by an organization or created in 829 accordance with a process or algorithm that is always followed. 831 3. The "common definition" constraint means that there are clear 832 definitions for the syntax of identifiers within the namespace 833 and for the process of assigning or creating them. 835 A URN namespace is identified by a particular NID in order to ensure 836 the global uniqueness of URNs and, optionally, to provide a cue 837 regarding the structure of URNs assigned within a namespace. 839 With regard to global uniqueness, using different NIDs for different 840 collections of identifiers ensures that no two URNs will be the same 841 for different resources, since each collection is required to 842 uniquely assign each identifier. However, a single resource MAY have 843 more than one URN assigned to it, either in the same namespace (if 844 the namespace permits it) or in different namespaces, and either for 845 similar purposes or different purposes. (For example, if a publisher 846 assigns an ISBN to an electronic publication and that publication is 847 later incorporated into a digital long term archive operated by a 848 national library, the library might assign the publication a NBN, 849 resulting in two URNs referring to the same book.) Subject to other 850 constraints, such as those imposed by the URI syntax [RFC3986], the 851 rules of the URN scheme are intended to allow preserving the normal 852 and natural form of identifiers specified elsewhere when they are 853 treated as URN namespaces. 855 With regard to the structure of URNs assigned within a namespace, the 856 development of an identifier structure (and thereby a collection of 857 identifiers) depends on the requirements of the community defining 858 the identifiers, how the identifiers will be assigned and used, etc. 859 These issues are beyond the scope of URN syntax and the general rules 860 for URN namespaces, because they are specific to the community 861 defining a namespace (e.g., the bibliographic and publishing 862 communities in the case of the 'ISBN' and 'ISSN' namespaces, or the 863 developers of extensions to the Extensible Messaging and Presence 864 Protocol in the case of the 'XMPP' namespace). 866 URN namespaces inherit certain rights and responsibilities by the 867 nature of URNs, e.g.: 869 1. They uphold the general principles of a well-managed URN 870 namespace by providing persistent identification of resources and 871 unique assignment of identifier strings in accordance with a 872 common definition. 874 2. Optionally, they can be registered in global registration 875 services such as those described in [RFC2483]. 877 There are two types of URN namespace: formal and informal. These are 878 distinguished by the expected level of service, the information 879 needed to define the namespace, and the procedures for registration. 880 Because the majority of the namespaces registered so far have been 881 formal, this document concentrates on formal namespaces. 883 5.1. Formal Namespaces 885 A formal namespace provides benefit to some subset of users on the 886 Internet. In particular, it would not make sense for a formal 887 namespace to be used only by a community or network that is not 888 connected to the Internet. For example, it would be inappropriate 889 for a NID to effectively force someone to use a proprietary network 890 or service not open to the general Internet user. The intent is 891 that, while the community of those who might actively use the names 892 assigned within that NID might be small, the potential use of 893 identifiers within that NID is open to any user on the Internet. 894 Formal NIDs might be appropriate even when some aspects are not fully 895 open. For example, a namespace might make use of a fee-based, 896 privately managed, or proprietary registry for assignment of URNs in 897 the namespace. However, it might still benefit some Internet users 898 if the associated services have openly-published identifiers. 900 An organization that will assign URNs within a formal namespace 901 SHOULD meet the following criteria: 903 1. Organizational stability and the ability to maintain the URN 904 namespace for a long time; absent such evidence, it ought to be 905 clear how the namespace can remain viable if the organization can 906 no longer maintain the namespace. 908 2. Competency in name assignment. This will improve the likelihood 909 of persistence (e.g. to minimize the likelihood of conflicts). 911 3. Commitment to not reassigning existing names and to allowing old 912 names to continue to be valid (e.g., if the assignee of a name is 913 no longer a member or customer of the assigning organization, if 914 various information about the assignee or named entity happens to 915 change, or even if the assignee or the named entity itself is no 916 longer in existence; in all these cases, the name is still 917 valid). 919 A formal namespace establishes a particular NID, subject to the 920 following constraints (above and beyond the syntax rules already 921 specified): 923 1. It MUST NOT be an already-registered NID. 925 2. It MUST NOT start with "urn-" (which is reserved for informal 926 namespaces). 928 3. It MUST be more than two characters long. 930 4. It MUST NOT start with ALPHA ALPHA "-", i.e., any string 931 consisting of two letters followed by one hyphen. 933 5. It MUST NOT start with the string "xn--" or any other string 934 consisting of two letters followed by two hyphens. Such strings 935 are reserved for potential representation of DNS A-labels and 936 similar strings in the future [RFC5890]. 938 6. It MUST NOT start with the string "X-" so that it will not be 939 confused with or conflict any experimental namespace previously 940 permitted by [RFC3406]. 942 All two-letter strings, and all two-letter strings followed by "-" 943 and any sequence of valid NID characters, are reserved for potential 944 use as NIDs based on ISO alpha-2 country codes [ISO3166-1] for 945 eventual national registrations of URN namespaces. The definition 946 and scoping of rules for allocation of responsibility for such 947 country-code-based namespaces is beyond the scope of this document. 949 Applicants and reviewers considering new NIDs should also be aware 950 that they may be considered as names with semantic implications and 951 hence a source of conflict. Particular attention should be paid to 952 strings that might be construed as names of, or registered under the 953 authority of, countries (including ISO 3166-1 alpha-3 codes) and to 954 strings that might imply association with existing URI schemes, 955 identifier systems, or trademarks. However, in line with traditional 956 policies, disputes about "ownership" of particular strings are 957 disagreements among the parties involved; neither IANA nor the IETF 958 will become involved in such disputes except in response to orders 959 from a court of competent jurisdiction. 961 5.2. Informal Namespaces 963 Informal namespaces are full-fledged URN namespaces, with all the 964 associated rights and responsibilities. Informal namespaces differ 965 from formal namespaces in the process for assigning a NID: for an 966 informal namespace, the registrant does not designate the NID; 967 instead, IANA assigns a NID consisting of the string 'urn-' followed 968 by one or more digits (e.g., "urn-7") where the digits consist of the 969 next available number in the sequence of positive integers assigned 970 to informal namespaces. Thus the syntax of an informal namespace is: 972 InformalNamespaceName = "urn-" Number 973 Number = DigitNonZero 0*Digit 974 DigitNonZero = "1"/ "2" / "3" / "4"/ "5" 975 / "6" / "7" / "8" / "9" 976 Digit = "0" / DigitNonZero 978 The only restrictions on are that it (1) consist strictly of 979 ASCII digits, that it (2) not have leading zeros, and that it (3) not 980 cause the NID to exceed the length limitations defined for the URN 981 syntax. 983 6. Defining and Registering a URN Namespace 985 6.1. Overview 987 Because the space of URN namespaces is itself managed, the definition 988 of a namespace SHOULD pay particular attention to: 990 1. The purpose of the namespace. 992 2. The syntax of URNs assigned within the namespace, including the 993 internal syntax and anticipated effects of q-components or 994 r-components. (The syntax and interpretation of f-components are 995 defined in RFC 3986.) 997 3. The process for assigning URNs within the namespace. 999 4. The security implications of assigning URNs within the namespace 1000 and using the assigned URNs. 1002 5. Any potential interoperability issues with URNs assigned within 1003 the namespace. 1005 6. Optionally, the process for resolving URNs issued within the 1006 namespace. 1008 The section on completing the template (Section 6.4) explains these 1009 matters in greater detail. Although the registration templates are 1010 the same in all cases, slightly different procedures are used 1011 depending on the source of the registration. 1013 6.2. Registration Policy and Process: Community Registrations 1015 The basic registration policy for URN namespaces is Expert Review as 1016 defined in the "IANA Considerations" document [RFC5226]. For 1017 namespaces or their definitions that are intended to become standards 1018 or normative components of standards, the output of the Expert Review 1019 process is intended to be a report, rather than instructions to IANA 1020 to take action (see below). The key steps are: 1022 1. Fill out the namespace registration template (see Section 6.4 and 1023 Appendix A). This can be done as part of an Internet-Draft or a 1024 specification in another series, although that is not necessary. 1026 2. Send the completed template to the urn@ietf.org discussion list 1027 for review. 1029 3. If necessary to address comments received, repeat steps 1 and 2. 1031 4. If the designated experts approve the request and no 1032 standardization action is involved, the IANA will register the 1033 requested NID. If standardization is anticipated, the designated 1034 experts will prepare a report and forward it to the appropriate 1035 standards approval body (the IESG in the case of the IETF); IANA 1036 will register the requested NID only after receiving directions 1037 from that body and a copy of the expert review report. 1039 A namespace registration can be revised by updating the registration 1040 template, following the same steps outlined above for new 1041 registrations. A revised registration MUST describe differences from 1042 prior versions and SHOULD make special note of any relevant changes 1043 in the underlying technologies or namespace management processes. 1045 Experience to date with namespace registration requests has shown 1046 that registrants sometimes do not initially understand some of the 1047 subtleties of URN namespaces, and that defining the namespace in the 1048 form of a specification enables the registrants to clearly formulate 1049 their "contract" with the intended user community. Therefore, 1050 although the registration policy for formal namespaces is Expert 1051 Review and a specification is not strictly required, registrants 1052 SHOULD provide a stable specification documenting the namespace 1053 definition and expanding upon the issues described herein. 1055 Because naming can be difficult and contentious, namespace 1056 registrants and the designated experts are strongly encouraged to 1057 work together in a spirit of good faith and mutual understanding to 1058 achieve rough consensus (see [RFC7282]) on handling registration 1059 requests. They are also encouraged to bring additional expertise 1060 into the discussion if that would be helpful in providing perspective 1061 or otherwise resolving issues. 1063 Especially when iterations in the registration process are prolonged, 1064 designated experts are expected to take reasonable precautions to 1065 avoid "race conditions" on proposed NID names and, if such situations 1066 arise, to encourage applicants to work out any conflicts among 1067 themselves. 1069 6.3. Registration Policy and Process: Fast Track for Standards 1070 Development Organizations, Scientific Societies, and Similar 1071 Bodies 1073 The IETF recognizes that situations will arise in which URN 1074 namespaces will be created to either embed existing and established 1075 standards, particularly identifier standards, or to reflect 1076 knowledge, terminology, or methods of organizing information that lie 1077 well outside the IETF's scope or the likely subject matter knowledge 1078 of its Designated Experts. In situations in which the registration 1079 request originates from, or is authorized by, a recognized standards- 1080 related organization, scientific society, or similar body, a somewhat 1081 different procedure is available at the option of that body: 1083 1. The namespace registration template is filled out and submitted 1084 as in steps 1 and 2 above. 1086 2. A specification is required that reflects or points to the needed 1087 external standards or specifications. Publication in the RFC 1088 Series or through an IETF process (e.g., posting as an Internet 1089 Draft) is not expected and would be appropriate only under very 1090 unusual circumstances. 1092 3. The reviews on the discussion list and by the designated experts 1093 are strictly advisory, with the decisions about what advice to 1094 accept and the length of time to allocate to the process strictly 1095 under the control of the external body. 1097 4. When that body concludes that the application is sufficiently 1098 mature, its representative(s) will request that IANA complete the 1099 registration for the NID, and IANA will do so. 1101 Decisions about whether to recognize the requesting entity as a 1102 standards-related organization, scientific society, or similar body 1103 are the responsibility of the IESG. 1105 A model similar to this has already been defined for recognized 1106 standards-related organizations that wish to register Media Types. 1107 The document describing that mechanism [RFC6838] provides somewhat 1108 more information about the general approach. 1110 6.4. Completing the Template 1112 A template for defining and registering a URN namespace is provided 1113 in Appendix A. This section describes considerations for completing 1114 the template. 1116 6.4.1. Purpose 1118 The "Purpose" section of the template describes matters such as: 1120 1. The kinds of resources identified by URNs assigned within the 1121 namespace. 1123 2. The scope and applicability of the URNs assigned within the 1124 namespace; this might include information about the community of 1125 use (e.g., a particular nation, industry, technology, or 1126 organization), whether the assigned URNs will be used on public 1127 networks or private networks, etc. 1129 3. How the intended community (and the Internet community at large) 1130 will benefit from using or resolving the assigned URNs. 1132 4. How the namespace relates to and complements existing URN 1133 namespaces, URI schemes, and identifier systems. 1135 5. The kinds of software applications that can use or resolve the 1136 assigned URNs (e.g., by differentiating among disparate 1137 namespaces, identifying resources in a persistent fashion, or 1138 meaningfully resolving and accessing services associated with the 1139 namespace). 1141 6. Whether resolution services are available or will be available 1142 (and, if so, the nature or identity of the services). Examples 1143 of q-component and, when they are standardized, r-component, 1144 semantics and syntax are helpful here, even if detailed 1145 definitions are provided elsewhere later. 1147 7. Whether the namespace or its definition is expected to become an 1148 integral or normative element of a standard being developed in 1149 the IETF or some other recognized standards body. 1151 6.4.2. Syntax 1153 The "Syntax" section of the template contains: 1155 1. A description of the structure of URNs within the namespace, in 1156 conformance with the fundamental URN syntax. The structure might 1157 be described in terms of a formal definition (e.g., using 1158 Augmented BNF for Syntax Specifications (ABNF) as specified in 1159 [RFC5234]), an algorithm for generating conformant URNs, or a 1160 regular expression for parsing the identifier into components; 1161 alternatively, the structure might be opaque. 1163 2. Any special character encoding rules for assigned URNs (e.g., 1164 which character ought to always be used for quotes). 1166 3. Rules for determining URN equivalence between two identifiers in 1167 the namespace. Such rules ought to always have the effect of 1168 eliminating false negatives that might otherwise result from 1169 comparison. If it is appropriate and helpful, reference can be 1170 made to specific equivalence rules defined in the URI 1171 specification [RFC3986]. Examples of URN equivalence rules 1172 include equivalence between uppercase and lowercase characters in 1173 the Namespace Specific String, between hyphenated and non- 1174 hyphenated groupings in the identifier string, or between single- 1175 quotes and double-quotes. There may also be namespace-specific 1176 special encoding considerations, especially for URNs that contain 1177 embedded forms of other types of identifiers. (Note that these 1178 are not normative statements for any kind of best practice 1179 related to handling of relationships between characters in 1180 general; such statements are limited to one particular namespace 1181 only.) 1183 4. Any special considerations necessary for conforming with the URN 1184 syntax. This is particularly applicable in the case of existing 1185 naming systems that are used in the context of URNs. For 1186 example, if a namespace is used in contexts other than URNs, it 1187 might make use of characters that are reserved in the URN syntax. 1188 This section ought to note any such characters, and outline 1189 necessary mappings to conform to URN syntax. Normally, this will 1190 be handled by percent-encoding the character as specified in 1191 Section 2.1 of the URI specification [RFC3986]. 1193 5. Any special considerations for the meaning of q-components (e.g., 1194 keywords) or f-components (e.g., predefined terms) in the context 1195 of this namespace. 1197 6.4.3. Assignment 1199 The "Assignment" section of the template describes matters such as: 1201 1. Mechanisms or authorities for assigning URNs to resources. It 1202 ought to make clear whether assignment is completely open (e.g., 1203 following a particular procedure such as first-come, first-served 1204 (FCFS)), completely closed (e.g., for a private organization), or 1205 limited in various ways (e.g., delegated to authorities 1206 recognized by a particular organization); if limited, it ought to 1207 explain how to become an assigner of identifiers or how to 1208 request assignment of identifiers from existing assignment 1209 authorities. 1211 2. Methods for ensuring that URNs within the namespace are unique. 1212 For example, identifiers might be assigned sequentially or in 1213 accordance with some well-defined process by a single authority, 1214 assignment might be partitioned among delegated authorities that 1215 are individually responsible for respecting uniqueness rules, or 1216 URNs might be created independently following an algorithm that 1217 itself guarantees uniqueness. 1219 6.4.4. Security and Privacy 1221 The "Security and Privacy" section of the template describes any 1222 potential issues related to security and privacy with regard to 1223 assignment, use, and resolution of identifiers within the namespace. 1224 Examples of such issues include: 1226 o The consequences of producing false negatives and false positives 1227 during comparison for URN equivalence (see "Issues in Identifier 1228 Comparison for Security Purposes" [RFC6943]) 1230 o Leakage of private information when identifiers are communicated 1231 on the public Internet 1233 o The potential for directory harvesting 1235 o Various issues discussed in the guidelines for security 1236 considerations in RFCs [RFC3552] and the privacy considerations 1237 for Internet protocols [RFC6973]. 1239 6.4.5. Interoperability 1241 The "Interoperability" section MUST specify any known potential 1242 issues related to interoperability. Examples include possible 1243 confusion with other URN namespaces or naming systems because of 1244 syntax (e.g., percent-encoding of certain characters) or scope (e.g., 1245 overlapping areas of interest). If at all possible, concerns that 1246 arise during the registration of a URN namespace (e.g., due to the 1247 syntax or scope of an identifier system) should be resolved as part 1248 of or in parallel to the registration process. 1250 6.4.6. Resolution 1252 The "Resolution" section MUST specify whether resolution mechanisms 1253 are intended or anticipated for URNs assigned within the namespace 1254 (e.g., URNs within some namespaces are intended to act as abstract 1255 designators and thus are not intended to be resolved). 1257 If resolution is intended, then this section SHOULD specify whether 1258 the organization that assigns URNs within the namespace intends to 1259 operate or recommend any resolution services for URNs within that 1260 namespace. In addition, if the assigning organization intends to 1261 implement registration for publicly advertised resolution services 1262 (for example using a system based on principles similar to those 1263 described in [RFC2276] and [RFC2483]), then this section SHOULD list 1264 or reference the requirements for being publicly advertised by the 1265 assigning organization. In addition, this section SHOULD describe 1266 any special considerations for the handling of r-components in the 1267 context of this namespace. 1269 6.4.7. Additional Information 1271 Please include any additional information that would be useful to 1272 those trying to understand this registration or its relationship to 1273 others, such as comparisons to existing namespaces that might seem to 1274 overlap. 1276 This section of the template is optional. 1278 7. IANA Considerations 1280 7.1. URI Scheme 1282 This section updates the registration of the 'urn' URI scheme in the 1283 Permanent URI Registry [URI-Registry] . 1285 [Note to RFC Editor: please replace "[ this document ]" with "RFC" 1286 and the number assigned to this document upon publication.] 1287 URI Scheme Name: urn 1289 Status: permanent 1291 URI Scheme Syntax: See Section 2 of [ this document ]. 1293 URI Scheme Semantics: The 'urn' scheme identifies Uniform Resource 1294 Names, which are persistent, location-independent resource 1295 identifiers. 1297 Encoding Considerations: See Section 2 of [ this document ]. 1299 Applications/Protocols That Use This URI Scheme Name: Uniform 1300 Resource Names are used in a wide variety of applications, 1301 including bibliographic reference systems and as names for 1302 Extensible Markup Language (XML) namespaces. 1304 Interoperability Considerations: See Section 4 of [ this document ]. 1306 Security Considerations: See Section 6.4.4 and Section 8 of [ this 1307 document ]. 1309 Contact: URNBIS WG [mailto:urn@ietf.org] 1311 Author/Change Controller: This scheme is registered under the IETF 1312 tree. As such, the IETF maintains change control. 1314 References None. 1316 7.2. Registration of URN Namespaces 1318 This document outlines the processes for registering URN namespaces, 1319 and has implications for the IANA in terms of registries to be 1320 maintained (see especially Section 6). In all cases, the IANA ought 1321 to assign the appropriate NID (formal or informal) once the 1322 procedures outlined in this document have been completed. 1324 8. Security and Privacy Considerations 1326 The definition of a URN namespace needs to account for potential 1327 security and privacy issues related to assignment, use, and 1328 resolution of identifiers within the namespace (e.g., some namespace 1329 resolvers might assign special meaning to certain characters in the 1330 Namespace Specific String); see Section 6.4.4 for further discussion. 1332 In most cases, URN namespaces provide a way to declare public 1333 information. Normally, these declarations will have a relatively low 1334 security profile, however there is always the danger of "spoofing" 1335 and providing misinformation. Information in these declarations 1336 ought to be taken as advisory. 1338 9. References 1340 9.1. Normative References 1342 [RFC20] Cerf, V., "ASCII format for network interchange", RFC 20, 1343 October 1969. 1345 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1346 Requirement Levels", BCP 14, RFC 2119, March 1997. 1348 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1349 Resource Identifier (URI): Generic Syntax", STD 66, 1350 RFC 3986, January 2005. 1352 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1353 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1354 May 2008. 1356 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 1357 Specifications: ABNF", STD 68, RFC 5234, January 2008. 1359 9.2. Informative References 1361 [DOI-URI] Paskin, N., Neylon, E., Hammond, T., and S. Sun, "The 1362 "doi" URI Scheme for the Digital Object Identifier (DOI)", 1363 June 2003, 1364 . 1366 [I-D.ietf-urnbis-semantics-clarif] 1367 Klensin, J., "URN Semantics Clarification", draft-ietf- 1368 urnbis-semantics-clarif-03 (work in progress), February 1369 2016. 1371 [ISO3166-1] 1372 ISO, "Codes for the representation of names of countries 1373 and their subdivisions -- Part 1: Country codes", 1374 ISO 3166-1:2013, 2013. 1376 [RFC1737] Sollins, K. and L. Masinter, "Functional Requirements for 1377 Uniform Resource Names", RFC 1737, December 1994. 1379 [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997. 1381 [RFC2276] Sollins, K., "Architectural Principles of Uniform Resource 1382 Name Resolution", RFC 2276, January 1998. 1384 [RFC2483] Mealling, M. and R. Daniel, "URI Resolution Services 1385 Necessary for URN Resolution", RFC 2483, January 1999. 1387 [RFC3044] Rozenfeld, S., "Using The ISSN (International Serial 1388 Standard Number) as URN (Uniform Resource Names) within an 1389 ISSN-URN Namespace", RFC 3044, January 2001. 1391 [RFC3187] Hakala, J. and H. Walravens, "Using International Standard 1392 Book Numbers as Uniform Resource Names", RFC 3187, October 1393 2001. 1395 [RFC3406] Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom, 1396 "Uniform Resource Names (URN) Namespace Definition 1397 Mechanisms", BCP 66, RFC 3406, October 2002. 1399 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 1400 Text on Security Considerations", BCP 72, RFC 3552, July 1401 2003. 1403 [RFC4854] Saint-Andre, P., "A Uniform Resource Name (URN) Namespace 1404 for Extensions to the Extensible Messaging and Presence 1405 Protocol (XMPP)", RFC 4854, April 2007. 1407 [RFC5122] Saint-Andre, P., "Internationalized Resource Identifiers 1408 (IRIs) and Uniform Resource Identifiers (URIs) for the 1409 Extensible Messaging and Presence Protocol (XMPP)", 1410 RFC 5122, February 2008. 1412 [RFC5890] Klensin, J., "Internationalized Domain Names for 1413 Applications (IDNA): Definitions and Document Framework", 1414 RFC 5890, August 2010. 1416 [RFC6648] Saint-Andre, P., Crocker, D., and M. Nottingham, 1417 "Deprecating the "X-" Prefix and Similar Constructs in 1418 Application Protocols", BCP 178, RFC 6648, June 2012. 1420 [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type 1421 Specifications and Registration Procedures", BCP 13, 1422 RFC 6838, January 2013. 1424 [RFC6943] Thaler, D., "Issues in Identifier Comparison for Security 1425 Purposes", RFC 6943, May 2013. 1427 [RFC6963] Saint-Andre, P., "A Uniform Resource Name (URN) Namespace 1428 for Examples", BCP 183, RFC 6963, May 2013. 1430 [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., 1431 Morris, J., Hansen, M., and R. Smith, "Privacy 1432 Considerations for Internet Protocols", RFC 6973, July 1433 2013. 1435 [RFC7282] Resnick, P., "On Consensus and Humming in the IETF", 1436 RFC 7282, June 2014. 1438 [RFC7320] Nottingham, M., "URI Design and Ownership", BCP 190, 1439 RFC 7320, July 2014. 1441 [RFC7613] Saint-Andre, P. and A. Melnikov, "Preparation, 1442 Enforcement, and Comparison of Internationalized Strings 1443 Representing Usernames and Passwords", RFC 7613, 1444 DOI 10.17487/RFC7613, August 2015, 1445 . 1447 [UAX31] The Unicode Consortium, "Unicode Standard Annex #31: 1448 Unicode Identifier and Pattern Syntax", June 2015, 1449 . 1451 [UNICODE] The Unicode Consortium, "The Unicode Standard", 2015, 1452 . 1454 [URI-Registry] 1455 IANA, "Permanent URI Schemes", 1456 . 1459 [XML-BASE] 1460 Marsh, J. and R. Tobin, "XML Base (Second Edition)", World 1461 Wide Web Consortium Recommendation REC-xmlbase-20090128, 1462 January 2009, 1463 . 1465 [XML-NAMES] 1466 Thompson, H., Hollander, D., Layman, A., Bray, T., and R. 1467 Tobin, "Namespaces in XML 1.0 (Third Edition)", World Wide 1468 Web Consortium Recommendation REC-xml-names-20091208, 1469 December 2009, 1470 . 1472 Appendix A. Registration Template 1474 Namespace ID: Requested of IANA (formal) or assigned by IANA 1475 (informal). 1477 Version: The version of the registration, starting with 1 and 1478 incrementing by 1 with each new version. 1480 Date: The date when the registration is requested of IANA, using the 1481 format YYYY-MM-DD. 1483 Registrant: The person or organization that has registered the NID, 1484 including the name and address of the registering organization, as 1485 well as the name and contact information (email, phone number, or 1486 postal address) of the designated contact person. If the 1487 registrant is a recognized standards development organization or 1488 scientific society requesting the fact track registration 1489 procedure (see Section 6.3), that information should be clearly 1490 indicated in this section of the template. 1492 Purpose: Described under Section 6.4.1 of this document. 1494 Syntax: Described under Section 6.4.2 of this document. Unless the 1495 registration explicitly says otherwise, use of q-components and 1496 f-components is not allowed for this namespace. 1498 Assignment: Described under Section 6.4.3 of this document. 1500 Security and Privacy: Described under Section 6.4.4 of this 1501 document. 1503 Interoperability: Described under Section 6.4.5 of this document. 1505 Resolution: Described under Section 6.4.6 of this document. 1507 Documentation: A pointer to an RFC, a specification published by 1508 another standards development organization, or another stable 1509 document that provides further information about the namespace. 1511 Additional Information Described under Section 6.4.7 of this 1512 document. 1514 Revision Information: Description of changes from prior version(s). 1515 (Applicable only when earlier registrations have been revised.) 1517 Additional Information: Any additional information that would be 1518 useful to the reader or those trying to understand the 1519 registration, perhaps in context with other work. May be a 1520 reference to another document or omitted if not needed. 1522 Appendix B. Changes from RFC 2141 1524 This document makes substantive changes from the syntax and semantics 1525 of [RFC2141]: 1527 B.1. Syntax changes from RFC 2141 1529 The syntax of URNs as provided in [RFC2141] was defined before the 1530 updated specification of URIs in [RFC3986]. The definition of URN 1531 syntax is updated in this document to do the following: 1533 o Ensure consistency with the URI syntax. 1535 o Facilitate the use of URNs with parameters similar to URI queries 1536 and fragments. 1538 o Permit parameters influencing URN resolution. 1540 o Ease the use of URNs with naming systems that include the '/' 1541 character. 1543 In particular, this specification does the following: 1545 o Extends URN syntax to explicitly allow the characters '/', "?", 1546 and "#", which were reserved for future use by RFC 2141. As 1547 described below, this change effectively also allows several 1548 components of the URI syntax although without necessarily tying 1549 those components to URI semantics. 1551 o Defines general syntax for an additional component that can be 1552 used in interactions with a URN resolution service. 1554 o Disallows "-" at the end of a NID. 1556 o Allows the "/", "~", and "&" characters in the namespace-specific 1557 string (NSS). 1559 o Makes several smaller syntax adjustments. 1561 B.2. Other changes from RFC 2141 1563 o Formally registers 'urn' as a URI scheme. 1565 o Allows what are now called q-components, r-components, and 1566 f-components. 1568 In addition, some of the text has been updated to be consistent with 1569 the definition of Uniform Resource Identifiers (URIs) [RFC3986] and 1570 the processes for registering information with the IANA [RFC5226], as 1571 well as more modern guidance with regard to security [RFC3552] and 1572 privacy [RFC6973] issues and identifier comparison [RFC6943]. 1574 Appendix C. Changes from RFC 3406 1576 This document makes the following substantive changes from [RFC3406]: 1578 1. Relaxes the registration policy for formal namespaces from "IETF 1579 Review" to "Expert Review" as discussed in Section 6.2. 1581 2. Removes the category of experimental namespaces, consistent with 1582 [RFC6648]. Experimental namespaces were denoted by prefixing the 1583 namespace identifier with the string "X-". Because experimental 1584 namespaces were never registered, removing the experimental 1585 category has no impact on the existing registries. Because they 1586 are not registered, strings that refer to experimental namespaces 1587 are not valid URNs. Truly experimental usages MAY, of course, 1588 employ the 'example' namespace [RFC6963]. 1590 3. Adds some information too, but generally simplifies, the 1591 registration template. 1593 Appendix D. Contributors 1595 RFC 2141, which provided the basis for the syntax portion of this 1596 document, was authored by Ryan Moats. 1598 RFC 3406, which provided the basis for the namespace portion of this 1599 document, was authored by Leslie Daigle, Dirk-Willem van Gulik, 1600 Renato Iannella, and Patrik Faltstrom. 1602 Their work is gratefully acknowledged. 1604 Appendix E. Acknowledgements 1606 Many thanks to Marc Blanchet, Leslie Daigle, Martin Duerst, Juha 1607 Hakala, Ted Hardie, Alfred Hoenes, Paul Jones, Barry Leiba, Sean 1608 Leonard, Larry Masinter, Keith Moore, Mark Nottingham, Julian 1609 Reschke, Lars Svensson, Henry S. Thompson, Dale Worley, and other 1610 participants in the URNBIS WG for their input. Alfred Hoenes in 1611 particular edited an earlier version of this document and served as 1612 co-chair of the URNBIS WG. 1614 Juha Hakala deserves special recognition for his dedication to 1615 successfully completing this work, as do Andrew Newton and Melinda 1616 Shore in their roles as working group co-chairs and Barry Leiba in 1617 his role as area director and then as co-chair. 1619 Appendix F. Change log for versions of draft-ietf-urnbis-rfc2141bis-urn 1621 [[RFC Editor: please remove this appendix before publication.]] 1623 F.1. Changes from -08 to -09 1625 o Altered the text in Section 4 to reflect list discussions about 1626 the earlier phrasing. Also added DOI example and citation to that 1627 section. 1629 o Clarified the naming rules for formal namespaces and their 1630 relationship to ISO 3166, IDNA, etc., reserved strings. 1632 o Added an explicit statement about use of URNs in various protocols 1633 and contexts to Section 4. 1635 o Clarified that experimental namespace NIDs, which were explicitly 1636 not registered, are not valid URNs (in Section 5. 1638 o Transformed the partial production in Section 5.2 into valid ABNF. 1640 o Added more text about p-/q-/f-components and recommendations about 1641 use. 1643 o Added clarifying note about "?" within q-components and 1644 f-components. 1646 o Added explicit requirement that revisions of existing 1647 registrations document the changes and added a slot for that 1648 description to the template. 1650 o Many small editorial changes and adjustments including adding 1651 additional references and cross-references for clarification. 1653 o Inserted a placeholder for additional examples. 1655 F.2. Changes from -09 to -10 1657 o Several clarifying editorial changes, most suggested by Ted Hardie 1658 and Henry S. Thompson (some of them off-list). 1660 o Added a large number of placeholders that identify issues that 1661 require WG consideration and resolution (or WG delegation to the 1662 editors). 1664 F.3. Changes from -10 to -11 1666 o Removed most of the placeholders added in -10. Supplied new text 1667 as required or suggested by on-list discussion of those issues. 1669 o Replaced the conformance examples Section 3.2 with a more complete 1670 collection and discussion. 1672 o Revised and consolidated the registration procedure, and added 1673 provisions for NIDs that are the subject of standards and for 1674 avoiding race conditions about NID strings. 1676 o In response to independent comments from Ted Hardie and Henry S. 1677 Thompson, called attention to the possibility of conflicts between 1678 NID strings and various claims of national, corporate, and other 1679 perogatives. 1681 o Changed the production for assigned-name as suggested by Lars 1682 Svensson. 1684 o Several clarifying editorial changes including correcting a glitch 1685 in instructions to the RFC Editor. 1687 F.4. Changes from -11 to -12 1689 o Removed p-components as a standalone construct, and instead folded 1690 them into the NSS. 1692 o Defined syntax for r-components as a way to pass information to 1693 resolvers, but left the semantics for future standardization 1694 efforts. 1696 o Further tuned the discussion of interoperability and related 1697 registration issues. 1699 o Made a number of editorial corrections and reorganized the syntax 1700 material in Section 2 somewhat to make it internally consistent 1701 and keep the relationship to RFC 3986 clear. 1703 F.5. Changes from -12 to -13 1705 o More precisely defined the semantics of the optional components. 1707 o Defined the term "resolution" and clarified several related 1708 matters throughout the text. 1710 o Clarified terminological relationship to RFC 3986. 1712 o Further cleansed the document of p-components. 1714 o Corrected several examples to avoid confusion with existing 1715 identifier systems. 1717 o Improved text regarding the purpose of namespaces being 1718 registered. 1720 F.6. Changes from -13 to -14 1722 o Reverted the ABNF to what had been defined in version -12. 1724 o Added fast-track approval process for standards-related 1725 organizations, scientific societies, and similar bodies (similar 1726 to RFC 6838 for Media Types). 1728 F.7. Changes from -14 to -15 1730 o Reorganized the Introduction slightly, adding new subsection 1.1 1731 and making Terminology (the former Section 2) Section 1.2. 1733 o Tightened the discussion of "resolution" somewhat to try to 1734 mitigate some on-list confusion. 1736 o Added some text about character set choices and repertoires 1737 (consistent with the Section 1.1 explanation). 1739 o Moved away from "?" and "??" for q-component and r-component 1740 delimiters and went to two-character sequences for each. This 1741 includes several changes to the text to remove or modify 1742 discussions of string termination and the role of a question mark 1743 not followed by one of the new delimiters. 1745 o Redefined r-component to be an ASCII resolver ID and a string. 1746 Neither is further defined in this specification and text has been 1747 added to say that. 1749 o Several editorial changes to improve clarity, most following up on 1750 comments made on the list. These included modifying the table of 1751 contents so that the subsections on optional components now appear 1752 there. 1754 F.8. Changes from -15 (2016-02-04) to -16 1756 o Rewrote the introductory material to make the relationship to 1757 other specifications more clear and allow removing or altering 1758 text that was stated in terms of changes from 2141. The 1759 specification is now self-contained with regard to the earlier 1760 definitions and descriptions of URNs. 1762 o Removed the parts of Section 2 that were really a description of 1763 changes from RFC 2141 to Appendix B, where such changes are 1764 enumerated. Similarly, removed most material describing changes 1765 from RFC 3406 to Appendix C. 1767 o Replaced one example. 1769 o Rearranged and rewrote text to improve clarity and relationships 1770 to other documents and to reduce redundant material. 1772 o Made it more clear that r-components, despite the partial syntax 1773 specification, are reserved for future standardization. 1775 o Clarified that there can be URNs that neither resolve to URLs nor 1776 are abstract designators. 1778 o Added pointers to make it clear that the Syntax material in 1779 Section 2 is not self-contained, e.g., that its subsections and 1780 other sections further restrict strings that can be used for NIDs 1781 and so on. 1783 o Added an "Additional Information" section to the registration 1784 template. See list discussion on and about 2016-03-18. 1786 o Minor editorial/ typographic fixes (per comment from Lars). 1788 F.9. Changes from -16 (2016-04-16) to -17 1790 o Clarified material about copying q-components, including adding an 1791 example. 1793 o Modified the document in several places to try to respond to 1794 concerns about the unqualified use of the term "equivalence". The 1795 term has been eliminated in one or two places and changed to "URN 1796 equivalence" in situations in which the scheme is known and URN- 1797 specific rules are being applied. 1799 o Editorial and typographic fixes. 1801 o Temporarily (this version only) added [[CREF...]] placeholders to 1802 identify outstanding issues that might usefully be discussed 1803 during the 2016-06-29 virtual meeting but that must be resolved in 1804 some way for the document to move forward. 1806 Authors' Addresses 1808 Peter Saint-Andre 1809 Filament 1811 Email: peter@filament.com 1812 URI: https://filament.com/ 1814 John C Klensin 1815 1770 Massachusetts Ave, Ste 322 1816 Cambridge, MA 02140 1817 USA 1819 Phone: +1 617 245 1457 1820 Email: john-ietf@jck.com