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'I-D.ah-rfc2141bis-urn' ** Obsolete normative reference: RFC 3406 (Obsoleted by RFC 8141) -- Obsolete informational reference (is this intentional?): RFC 2141 (Obsoleted by RFC 8141) -- Obsolete informational reference (is this intentional?): RFC 2611 (Obsoleted by RFC 3406) -- Obsolete informational reference (is this intentional?): RFC 3044 (Obsoleted by RFC 8254) -- Obsolete informational reference (is this intentional?): RFC 3187 (Obsoleted by RFC 8254) -- Obsolete informational reference (is this intentional?): RFC 3188 (Obsoleted by RFC 8458) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 9 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IETF J. Hakala 3 Internet-Draft The National Library of Finland 4 Obsoletes: 3188 (if approved) A. Hoenes, Ed. 5 Updates: 2288 (if approved) TR-Sys 6 Intended status: Standards Track May 19, 2010 7 Expires: November 20, 2010 9 Using National Bibliography Numbers as Uniform Resource Names 10 draft-hakala-rfc3188bis-nbn-urn-00 12 Abstract 14 National Bibliography Numbers, NBNs, are widely used by the national 15 libraries and other organizations in order to identify various 16 resources such as monographs pre-dating the emergence of the ISBN 17 system or still images. As a rule, NBNs are applied to all kinds of 18 resources that do not have an established identifier system of their 19 own. 21 Since 2001, there has been a URN (Uniform Resource Names) namespace 22 for NBNs, and during 2001-2009 millions of URN-based unique and 23 persistent NBNs have been assigned. The namespace registration was 24 performed in RFC 3188 and applied to the NBNs known at that point. 25 No URN:NBN resolution services existed at the time when the RFC was 26 written. Since then several countries have started using URN:NBNs to 27 identify electronic resources and to provide persistent links to 28 them. To this end, many countries have established URN:NBN 29 resolution services that supply URN - URL linking. 31 This document replaces RFC 3188 and defines how NBNs can be supported 32 within the URN framework. An updated namespace registration (version 33 4) is included. 35 Discussion 37 This document is an outcome of work performed in 2009-2010 as a part 38 of the project PersID (http://www.persid.org) revising the basic URN 39 RFCs, in order to bring them in alignment with the current URI 40 Standard (STD 63, RFC 3986), ABNF, and IANA guidelines, and to 41 establish a modern URN resolution system for bibliographic 42 identifiers. This work is being brought to the IETF, and the intent 43 is to establish a "URNbis" (or similar) working group in the 44 Applications Area as soon as possible, which will then target this 45 and related work. 47 Comments are welcome on the urn@ietf.org or the urn-nid@ietf.org 48 mailing list (or sent to the authors). Interested parties are also 49 invited to contribute to the WG formation process being discussed on 50 the former list. 52 Status of This Memo 54 This Internet-Draft is submitted in full conformance with the 55 provisions of BCP 78 and BCP 79. 57 Internet-Drafts are working documents of the Internet Engineering 58 Task Force (IETF). Note that other groups may also distribute 59 working documents as Internet-Drafts. The list of current Internet- 60 Drafts is at http://datatracker.ietf.org/drafts/current/. 62 Internet-Drafts are draft documents valid for a maximum of six months 63 and may be updated, replaced, or obsoleted by other documents at any 64 time. It is inappropriate to use Internet-Drafts as reference 65 material or to cite them other than as "work in progress." 67 This Internet-Draft will expire on November 20, 2010. 69 Copyright Notice 71 Copyright (c) 2010 IETF Trust and the persons identified as the 72 document authors. All rights reserved. 74 This document is subject to BCP 78 and the IETF Trust's Legal 75 Provisions Relating to IETF Documents 76 (http://trustee.ietf.org/license-info) in effect on the date of 77 publication of this document. Please review these documents 78 carefully, as they describe your rights and restrictions with respect 79 to this document. Code Components extracted from this document must 80 include Simplified BSD License text as described in Section 4.e of 81 the Trust Legal Provisions and are provided without warranty as 82 described in the Simplified BSD License. 84 This document may contain material from IETF Documents or IETF 85 Contributions published or made publicly available before November 86 10, 2008. The person(s) controlling the copyright in some of this 87 material may not have granted the IETF Trust the right to allow 88 modifications of such material outside the IETF Standards Process. 89 Without obtaining an adequate license from the person(s) controlling 90 the copyright in such materials, this document may not be modified 91 outside the IETF Standards Process, and derivative works of it may 92 not be created outside the IETF Standards Process, except to format 93 it for publication as an RFC or to translate it into languages other 94 than English. 96 Table of Contents 98 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 99 2. Conventions used in this document . . . . . . . . . . . . . . 5 100 3. Identification and Resolution . . . . . . . . . . . . . . . . 5 101 4. Namespace considerations: National Bibliography Numbers 102 (NBNs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 103 4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 6 104 4.2. Encoding Considerations and Lexical Equivalence . . . . . 7 105 4.3. Resolution of NBN-based URNs . . . . . . . . . . . . . . . 9 106 4.4. Additional Considerations . . . . . . . . . . . . . . . . 10 107 4.5. Security Considerations . . . . . . . . . . . . . . . . . 11 108 4.6. URN Namespace ID Registration for the National 109 Bibliography Number (NBN) . . . . . . . . . . . . . . . . 11 110 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 111 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 112 7. Community Considerations . . . . . . . . . . . . . . . . . . . 17 113 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 114 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 115 9.1. Normative References . . . . . . . . . . . . . . . . . . . 17 116 9.2. Informative References . . . . . . . . . . . . . . . . . . 18 118 1. Introduction 120 One of the basic permanent URI schemes (cf. RFC 3986 [RFC3986], 121 [IANA-URI]) is 'URN' (Uniform Resource Name) as defined in RFC 2141 122 [RFC2141]. Currently, there is work in progress to revise that 123 document [I-D.ah-rfc2141bis-urn]. Any identifier, when used within 124 the URN system, needs its own namespace. As of this writing, there 125 are 40 registered URN namespaces (see [IANA-URN]), one of which 126 belongs to NBN, National Bibliography Number, as specified 2001 in 127 RFC 3188 [RFC3188]. 129 Currently URN:NBNs are in production use in several European 130 countries including Finland, Germany, Italy, the Netherlands, Norway, 131 and Sweden. Several other countries in Europe and elsewhere are 132 considering usage of them. URN:NBNs have been applied in, e.g., Web 133 archives, large collections of digitized materials, and collections 134 of scientific articles. 136 As part of the validation process for the development of URNs back in 137 late 90s, the IETF URN working group agreed that it was important to 138 demonstrate that a URN syntax proposal can accommodate existing 139 identifiers from well-established namespaces. 141 One such infrastructure for assigning and managing names comes from 142 the bibliographic community. Bibliographic identifiers function as 143 names for objects that exist both in print and, increasingly, in 144 electronic formats. RFC 2288 [RFC2288] investigated the feasibility 145 of using three identifiers (ISBN, ISSN and SICI) as URNs, with 146 positive results, however it did not formally register corresponding 147 URN namespaces. This was in part due to the still evolving process 148 to formalize criteria for namespace definition documents and 149 registration, consolidated later in the IETF into RFC 3406 [RFC3406]. 151 URN Namespaces have subsequently been registered for NBN, ISBN and 152 ISSN in RFCs 3188 [RFC3188], 3187 [RFC3187], and 3044 [RFC3044]. The 153 ISBN namespace registration is being revised so that it covers both 154 ISBN-10 and ISBN-13; [I-D.hakala-rfc3187bis-isbn-urn]. the current 155 ISSN registration still does not cover ISSN-L, defined in the new 156 version of ISSN. However, there is no registered namespace for SICI, 157 and no plans to make such registration, due to the low popularity of 158 the standard. 160 Please note that NBN differs from the other identifiers listed here 161 because there is no standard describing NBNs. The term "National 162 Bibliography Number" encompasses all identifier systems the national 163 libraries use in addition to the more formally established 164 identifiers. Historically, they were only applied in the national 165 bibliography to identify the resources catalogued into it. During 166 the last 10 years NBN scope has been extended to a wide variety of 167 digital resources available via the Internet. Only a minority of 168 these resources are catalogued in the national bibliography. Some 169 national libraries have also allowed other organizations to apply 170 NBNs to their publications and other materials. 172 Guidelines for using NBNs as URNs and the original namespace 173 registration have been published in RFC 3188 [RFC3188]. The RFC at 174 hand replaces RFC 3188 [RFC3188]; sections discussing the methods in 175 which URN:NBNs can be resolved have been updated and the text is also 176 compliant with the stipulations of RFC 3406 [RFC3406], which has 177 replaced RFC 2611 [RFC2611] that was applied in the initial 178 registration. 180 2. Conventions used in this document 182 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 183 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 184 document are to be interpreted as described in RFC 2119 [RFC2119]. 186 NBN refers to any National Bibliography Number identifier system used 187 by the national libraries and other institutions using the system 188 with the national library's permission. 190 3. Identification and Resolution 192 As a rule, NBNs identify finite, manageably-sized objects, but these 193 objects may still be large enough that resolution into a hierarchical 194 system is appropriate. The materials identified by an NBN will often 195 be digital, but they may also exist only in printed or other physical 196 form. In such a case, the URN:NBN resolver should nevertheless be 197 able to supply e.g. bibliographic data about the resource, possibly 198 including the address where the resource is available. 200 National libraries are the key organizations providing persistent URN 201 resolution services for resources identified with NBNs, independent 202 of their form. National libraries may however allow other 203 organizations such as university libraries or governmental 204 organizations to assign NBNs to their resources. In such case the 205 national library will co-ordinate the use of NBNs and support the NBN 206 users in guaranteeing the persistence of these resources and 207 resolution. These other organizations may establish their own 208 resolution services or they may use the infrastructure provided by 209 the national library. 211 4. Namespace considerations: National Bibliography Numbers (NBNs) 213 4.1. Overview 215 National Bibliography Number (NBN) is a generic name referring to a 216 group of identifier systems utilised by the national libraries and 217 institutions authorized by them, such as universities. The common 218 denominator is that all these organizations are committed to preserve 219 their collections for a long time; at least decades and possibly 220 centuries. 222 Each national library uses its own NBNs independently of other 223 national libraries; there is no global authority that controls NBN 224 usage. For this reason, NBNs as such are unique only on a national 225 level. When used as URNs, NBN strings must be augmented with a 226 controlled prefix such as the ISO 3166 country code. These prefixes 227 guarantee uniqueness of the NBN-based URNs on the global scale. 229 NBNs have traditionally been given to documents that do not have a 230 formal (standard) identifier, but are catalogued to the national 231 bibliography. Examples of this include books that predate the 232 introduction of the ISBN in the 1970s, or modern books that for some 233 reason have not received an ISBN. NBNs can be seen as a fall-back 234 mechanism: if no other, standards-based identifier such as an ISBN 235 can be given, an NBN is assigned. 237 URNs may also be used in universities' open repositories when a 238 resource already has another identifier -- often a DOI (Digital 239 Object Identifier) -- that can only be resolved in a publisher's (or 240 third party's) resolution service, which cannot be used to provide 241 linking to the open repository. URN:NBN-based resolution can deliver 242 that, and may also be extended to include access to other 243 repositories holding the same resource. 245 In principle, NBNs enable identification of any kind of resource, 246 such as still images published in periodical articles, or short 247 stories and poems published in book form or in the Web. Local 248 policies may limit the NBN usage to for instance documents stored 249 permanently in the national library's collections. Following the 250 initial registration of a URN namespace for NBN, several countries 251 broadened the scope of NBN assignment significantly to cover broader 252 scope of their digital materials. 254 Some national libraries (e.g., Finland, Norway, Sweden) have 255 established Web-based URN generators, which enable authors and 256 publishers to fetch NBN-based URNs for their network resources. 257 There are also applications, used for instance in digitization 258 processes, that assign NBNs automatically to resources or even their 259 component parts such as still images published in monographs or 260 serials. 262 Within the limitations set by RFC 2141, this document, and other 263 relevant RFCs, both syntax and scope of local NBNs can be decided by 264 each national library independently. Historically, NBNs have 265 consisted of one or more letters and/or digits. For instance, 266 (Finnish) NBN for the Romanian translation of the Finnish classic 267 "Seven Brothers" published in 1957 is f568471. URN strings can 268 contain encoded UNICODE characters, as specified in the declaration 269 of syntactic structure, and there are no length limitations. 270 Therefore, literally billions of NBNs can be allocated, which makes 271 them suitable for, e.g., naming of Web documents. 273 In Italy a novel hierarchical distributed architecture for NBN 274 assignment has been designed, in order to eliminate the single-point- 275 of-error risks of a centralised system and to reduce the costs of 276 managing a resolution service based on persistent identifiers. 278 The Central National Library in Florence manages the national domain 279 NBN:IT and the national URN resolution service that contains every 280 URN:NBN assigned in Italy. The library has supplied URN:NBN:IT sub- 281 domains to trusted institutions and bodies such as universities that 282 are responsible for digital collections and routinely manage digital 283 resources, for instance via creating and updating metadata on these 284 resources, including location (URL) information. All these 285 institutions have their own resolution services, but the URN - URL 286 mappings in them are periodically harvested to the national 287 resolution service using the Open Archives Initiative Protocol for 288 Metadata Harvesting (OAI-PMH; see 289 (). 291 Harvesting the data to the central node enables distributed service. 292 The central node can serve the users when the local node is not 293 functional. This architecture increases the robustness of the 294 network via duplication of resolution services and enables peer-to- 295 peer resolution between the second-level institutions. Moreover, it 296 is possible to add yet another layer to the network by creating an 297 international node, which shall contain all the data from the 298 national nodes. Such international service may also be created by 299 building a virtual union resolver that uses all the national nodes. 300 The PersID project is investigating the feasibility of these 301 technical solutions at the European level. 303 4.2. Encoding Considerations and Lexical Equivalence 305 Embedding NBNs within the URN framework initially did not present any 306 particular encoding problems, since the ASCII characters utilized in 307 traditional NBN systems belonged to the URN character set. Machine 308 generated NBNs may be more demanding; if necessary, NBNs must be 309 translated into canonical form as specified in 310 [I-D.ah-rfc2141bis-urn]. 312 When an NBN is used as a URN, the namespace specific string must 313 consist of three parts: 315 o a prefix, consisting of either a two-letter ISO 3166 country code 316 or other registered string, 318 o a delimiting character that is either hyphen (-) or colon (:), and 320 o the NBN string. 322 Delimiting characters are not lexically equivalent. 324 A Hyphen MUST be used for separating the prefix and the NBN string. 326 A Colon MAY be used as the delimiting character if and only if a 327 country code-based NBN namespace is split further in smaller sub- 328 namespaces. If there are several national libraries in one country, 329 these libraries can divide the national namespace between themselves 330 using this method. 332 A national library may also assign to trusted organisation(s) such as 333 a university or a government institution its own NBN sub-namespace. 334 For instance, the national library of Finland has given Statistics 335 Finland () a sub-namespace "st" 336 (i.e., urn:nbn:fi:st). These trusted organisations must follow the 337 general rules of the NBN usage provided by the national library, and 338 take care of the long-term preservation of the identified resources 339 in order to guarantee persistence. 341 Non-ISO 3166 prefixes, if used, MUST be registered on the global 342 level. The U.S. Library of Congress SHALL maintain the central 343 register of reserved codes. 345 Sub-namespace codes beneath a country-code-based namespace MUST be 346 registered on the national level by the national library that 347 assigned the code. The national register SHOULD be made available on 348 the Web. 350 Two-letter codes MUST NOT be used as non-ISO prefixes, since all such 351 codes are reserved for existing and possible future ISO country 352 codes. If there are several national libraries in one country that 353 use the same prefix - for instance, a country code -, they need to 354 agree on how to divide the namespace. They may either share one 355 namespace but agree on how to avoid assigning duplicate identifiers, 356 or they may split the namespace into two sub-namespaces. 358 Models: 360 URN:NBN:- 362 URN:NBN::- 365 URN:NBN:- 367 Examples: 369 URN:NBN:fi-fe201003181510 370 (NBN assigned to Tero Frestadius's Master's Thesis "In and Out": 371 Segmentary Gang Politics in Los Angeles). 373 urn:nbn:ch:bel-9039 375 urn:nbn:se:uu:diva-3475 377 urn:nbn:hu-3006 379 From the libraries' point of view, one of the key benefits of using 380 URNs and other persistent identifiers is that there is only one 381 location - the resolution service - where the linking infomation has 382 to be maintained. If bibliographic records in library on-line public 383 access catalogues (OPACs) contain URLs, then each record must be 384 modified whenever the URL changes. With URNs, it is only necessary 385 to maintain the URN - URL linking in the mapping table of the 386 resolution service. 388 4.3. Resolution of NBN-based URNs 390 URNs can be used to provide various services. RFC 2483 [RFC2483] 391 gives a few examples, such as retrieving a single URL or all URLs 392 applying to the resource. Services available may vary, depending on 393 the technical implementation of the URN resolver and the target 394 system contacted. Please note that services must not be hard coded 395 into the URN itself. 397 Eventually, URNs will be resolved with the help of a resolver 398 discovery service (RDS). However, no such system is widely available 399 yet. Therefore, URNs are usually embedded in HTTP URIs in order to 400 make them actionable in the present Internet. In these HTTP URIs, 401 the authority part must point to the appropriate URN resolution 402 service. In Finland, the address of the national URN resolver is 403 . Thus the HTTP URI for the URN in the example is 404 . This in turn resolves to 405 the actual address of the thesis, which as of this writing 406 (2010-03-27) was . 409 The country code-based prefix part of the URN namespace specific 410 string will provide a guide to finding the correct national 411 resolution service for URN:NBNs from the resolver discovery service 412 when it is established. If there are multiple URN:NBN resolvers in 413 the country, there are two possible approaches for making sure that 414 RDS will work. All URN:NBNs mappings can be harvested to the 415 national node (the Italian approach). The other approach is to make 416 the RDS aware of all the URN:NBN resolution services, and specify 417 which parts of the national URN:NBN namespace they are capable of 418 serving. 420 URN:NBN - URL mappings maintained nationally can be harvested using 421 e.g. OAI-PMH from abroad to other national and international URN 422 resolvers. This makes it possible to improve the reliability of the 423 system; if the Finnish national resolver node does not respond, its 424 URN - URL mappings may be available at other resolvers. 426 Persistence of any resolution service is not only a technical issue, 427 but also an organisational and legal one. National libraries are in 428 ideal position to provide persistent resolution services, since most 429 of them maintain (legal) deposit collections, in which domestic 430 publications shall be preserved for future generations. Increasingly 431 these collection contain also digital resources. 433 4.4. Additional Considerations 435 Guidelines adopted and promoted by each national library define when 436 different manifestations of a work should be assigned the same or 437 differing NBNs. These rules apply only if identifier assignment is 438 done manually. If identifiers are allocated programmatically, each 439 manifestation of a resource will get a new NBN. For instance, over 440 time the national library may digitize the same photograph many times 441 from different sources, but each copy will get its own NBN. However, 442 if a checksum such as MD5 (see RFC 1321 [RFC1321]) is used as NBN, 443 the resources that are identical at bit level will receive the same 444 NBN. Dissimilar resources may get the same checksum; with a reliable 445 message digest algorithm such probability is however very small. 447 The rules governing the usage of NBNs are local and usually less 448 strict than those specifying the usage of ISBNs and other standard 449 identifiers. As long as the NBNs were assigned only in the national 450 libraries, the identifier use was however well co-ordinated in 451 practice. Now, following significant broadening in the scope of the 452 NBN to cover Web resources, NBN assignment is less tightly controlled 453 even within one national library. One resource -- for instance, a 454 photo that has been published in many newspapers -- is likely to 455 receive multiple NBNs. If two national libraries are digitizing the 456 same resources and use NBNs for identification of these resources, 457 the result will be duplicate NBN assignment since NBNs as a rule have 458 national scope. If the metadata describing the resource is harvested 459 into a common service, and the bibliographic records are similar 460 enough to be merged, the user may see two NBNs and HTTP URIs pointing 461 to two different resolution services and physical copies of the same 462 resource. If the two copies had the same identifier such as an ISBN, 463 there would still be two HTTP URIs providing access to different 464 physical copies of the resource. 466 If the same resource -- for instance, a master's thesis published by 467 two universities -- is held in two repositories located in different 468 NBN-sub-namespaces within one national namespace, these copies may 469 also receive different NBNs especially if there is no easy way of 470 checking if the resource has already been identified somewhere. In 471 this case, duplication may be revealed in the national level when the 472 metadata records of the two copies are compared. In such case, like 473 in the previous example, both URN:NBNs are equally valid. 475 4.5. Security Considerations 477 This document proposes means of encoding national bibliography 478 numbers (NBNs) within the URN framework. It discusses resolution 479 only at a very generic level; thus, questions of secure or 480 authenticated resolution services and authentication of users of such 481 services are out of scope. This document does not address means of 482 validating the integrity or authenticating the source or provenance 483 of URNs that contain NBNs. Issues regarding intellectual property 484 rights associated with objects identified by national bibliography 485 numbers are also beyond the scope of this document, as are questions 486 about rights to the bibliographic databases that may be used to 487 construct resolution services. 489 4.6. URN Namespace ID Registration for the National Bibliography Number 490 (NBN) 492 This registration describes how National Bibliography Numbers (NBNs) 493 can be supported within the URN framework. 495 [ RFC Editor: please replace "XXXX" in all instances of "RFC XXXX" 496 below by the RFC number assigned to this document. ] 497 Namespace ID: NBN 499 This Namespace ID was formally assigned to the National 500 Bibliography Number in October 2001 when the namespace was 501 registered officially. Utilization of URN:NBNs started in 502 demonstrator systems in 1998; production use has been going on for 503 several years, and millions of URN:NBNs have been assigned. 505 Registration Information: 507 Version: 4 508 Date: 2010-05-18 510 Declared registrant of the namespace: 512 Name: Mr. Juha Hakala 513 Affiliation: Senior Adviser, The National Library of Finland 514 Email: juha.hakala@helsinki.fi 515 Postal: P.O.Box 15, 00014 Helsinki University, Finland 516 Web URL: http://www.nationallibrary.fi/ 518 The National Library of Finland registered the namespace on behalf 519 of the Conference of the European National Librarians (CENL) and 520 Conference of Directors of National Libraries (CDNL), which have 521 both made a commitment in 1998 to foster the use of URNs. The NBN 522 namespace will be available for free for all national libraries in 523 the world. 525 Declaration of syntactic structure: 527 The namespace specific string (NSS) will consist of three parts: 529 a prefix, consisting of either a two-letter ISO 3166 country 530 code or other registered string and sub-namespace codes, 532 delimiting characters (colon (:) and hyphen (-)), and 534 an NBN string assigned by the national library or sub-delegated 535 authority. 537 Formal declaration of the NSS, using ABNF [RFC5234]. 539 nbn_nss = prefix "-" nbn_string 541 prefix = cc_prefix / reg_prefix 543 cc_prefix = iso_cc *( ":" subspc ) 545 iso_cc = 2ALPHA 546 ; country code as assigned by ISO 3166, part 1 -- 547 ; identifies the national library 548 ; to which the branch is delegated 550 subspc = 1*ALPHANUM 551 ; as assigned by the respective national library 553 reg_prefix = 3*ALPHANUM 554 ; as assigned by the Library of Congress -- 555 ; identifies a trusted third party 556 ; to which the bracnh is delegated 558 nbn_string = 559 ; must follow RFC 3986 syntax 561 Colon may be used as a delimiting character only within the 562 prefix, between ISO 3166 country code and sub-namespace code, 563 which splits the national namespace into smaller parts. 565 Dividing non-ISO 3166-based namespaces further with sub-namespace 566 codes MUST NOT be done. 568 Hyphen MUST be used as the delimiting character between the prefix 569 and the NBN string. Within the NBN string, hyphen MAY be used for 570 separating different sections of the code from one another. 572 Non-ISO prefixes used instead of the ISO country code must be 573 registered. A global registry, maintained by the Library of 574 Congress, shall be created and made available via the Web. Contact 575 information: nbn.register@loc.gov.us. 577 All two-letter codes are reserved for existing and possible future 578 ISO country codes and MUST NOT be used as non-ISO prefixes. 580 Sub-namespace codes MUST be registered on the national level by 581 the national library which assigned the code. The list of such 582 codes SHOULD be available via the Web. 584 Models: 586 URN:NBN:- 588 URN:NBN:- 591 URN:NBN:- 593 Example: 595 urn:nbn:de:gbv:089-3321752945 597 Relevant ancillary documentation: 599 National Bibliography Number (NBN) is a generic name referring to 600 a group of identifier systems used by the national libraries and 601 other organizations for identification of deposited publications 602 and other resources that lack a 'canonical' identifier, or to 603 descriptive metadata (cataloguing) that describes the resources. 604 Each national library uses its own NBN system independently of 605 other national libraries; there is neither a general standard 606 defining NBN syntax nor a global authority to control the use of 607 these identifier systems. 609 Each national library decides locally which resources shall 610 receive NBNs. These identifiers have traditionally been assigned 611 to documents that do not have a publisher-assigned identifier, but 612 are nevertheless catalogued to the national bibliography. 613 Typically identification of grey publications have largely been 614 dependent on NBNs. With the introduction of the Internet and URN: 615 NBN namespace in 1998, the scope of NBN assignment has been 616 extended to a broad spectrum of Internet resources including, 617 e.g., harvested Web pages. 619 Some national libraries (Finland, Norway, Sweden) have established 620 Web-based URN generators that enable authors and publishers to 621 fetch NBN-based URNs for the resources they publish in the Web. 622 The most significant group of publications to which NBNs have been 623 applied are doctoral theses. 625 The syntax of NBNs is decided by each national library 626 independently. Historically, NBNs used in national bibliographies 627 contained only characters that belong to the URN character set. 628 Following the expansion of NBN scope and semi- and fully automated 629 NBN assignment processes, some NBNs may contain characters that 630 must be translated into canonical form according to the 631 specifications in [I-D.ah-rfc2141bis-urn]. 633 Identifier uniqueness and persistence considerations: 635 NBN strings assigned by two national libraries may be identical. 636 In order to guarantee global uniqueness of NBN-based URNs, 637 therefore a controlled prefix is present in the namespace specific 638 string. These NBNs, once given to the resource, will be 639 persistent. Persistence of the resources themselves will be 640 guaranteed by the national libraries as a part of their legal 641 deposit activities. This applies to publications and Web 642 resources only; long-term preservation of other resources such as 643 governmental documents will be dependent on other actors like 644 national archives. 646 An NBN, once it has been assigned, must never be re-used for 647 another resource. 649 At the national level, libraries may utilise different policies 650 for guaranteeing uniqueness of NBNs. They may be assigned 651 sequentially by programs (URN generators) in order to avoid human 652 mistakes. It is also possible to use checksums such as SHA-1 or 653 MD5 as NBN. 655 Process of identifier assignment: 657 Assignment of NBN-based URNs MUST be controlled on national level 658 by the national library / national libraries. Although the basic 659 principles are the same, there are differences in scope; for 660 instance in the Netherlands URN:NBNs are used -- among other 661 things -- to identify scientific articles stored in the national 662 library's long term preservation system, whereas most other URN 663 users are not applying them on scientific articles. Finland, on 664 the other hand, is using URNs extensively to identify and provide 665 access to the digitized content. 667 National libraries may choose different strategies in assigning 668 NBN-based URNs, and different approaches have varying levels of 669 control. Manual URN assignment by the library personnel only 670 provides the best possible control, especially if this is done 671 traditionally, that is, only when the document is catalogued into 672 the national bibliography. Usually the scope of URN:NBN is much 673 broader than this; NBNs may for instance be automatically 674 generated for each archived resource by a long term preservation 675 system. From control point of view, the most liberal approach is 676 a URN generator which builds URNs for everyone, with no guarantee 677 that the resource identified will be preserved or accessible. 678 Every national library must decide the degree of freedom it allows 679 to the URN:NBN users. Usage rules may of course vary from one 680 sub-namespace to the next. As of yet there are no international 681 guidelines for NBN use, but they may be developed in the future. 683 Process for identifier resolution: 685 See Section 4.3 of RFC XXXX. 687 Rules for lexical equivalence: 689 None in the global level, beyond those expressed in 690 [I-D.ah-rfc2141bis-urn]. 692 National libraries may develop their own rules for the NBNs they 693 use. 695 Conformance with URN syntax: 697 Traditional NBNs (those applied in the national bibliographies) 698 consisted of ASCII 7-bit letters and digits (a-z and 0-9). For 699 instance, the NBN of the first Hungarian translation of the 700 Finnish national epos Kalevala is f20043425. The book was 701 published in 1853 and therefore does not have an ISBN. Machine- 702 generated NBNs must follow the stipulations of 703 [I-D.ah-rfc2141bis-urn]. 705 Validation mechanism: 707 None specified on the global level (beyond a routine check of 708 those characters that require special encoding when expressed as 709 URIs). A national library may use NBNs, which contain a checksum 710 and can therefore be validated, but as of this writing there are 711 no NBNs which incorporate a checksum. 713 Scope: 715 NBN is a global identifier system used for identification of 716 diverse publications and other resources. It is widely used and 717 supported by the national libraries. 719 5. Security Considerations 721 This document proposes means of encoding NBNs within the URN 722 framework. An NBN-based URN resolution service is depicted, but only 723 in a fairly generic level; thus questions of secure or authenticated 724 resolution mechanisms are excluded. It does not deal with means of 725 validating the integrity or authenticating the source or provenance 726 of URNs that contain NBNs. Issues regarding intellectual property 727 rights associated with objects identified by the NBNs are also beyond 728 the scope of this document, as are questions about rights to the 729 databases that might be used to construct resolvers. 731 6. IANA Considerations 733 IANA is asked to update the existing registration of the Formal URN 734 Namespace 'NBN' using the template given above in Section 4.6. 736 7. Community Considerations 738 National bibliography numbers enable the national libraries and 739 organisations which liaise with them to uniquely identify resources 740 and provide persistent links to the resource accessible in the 741 Internet. Since most digital documents held in national libraries' 742 digital collections are not eligible for other, more formal 743 identifiers such as ISBN, NBNs are a valuable asset for the 744 community. A proof of this are the millions of URN:NBNs that have 745 been allocated since the NBN namespace was reserved, and the 746 operational services that have been built, using these identifiers 747 and resolver applications. 749 For library users, URN-based identification and resolution services 750 mean more efficient and reliable access to resources in general. No 751 special tools are needed for this; Web browsers are sufficient. The 752 users may also be able to acquire URN:NBNs to their own key resources 753 such as university thesis. 755 8. Acknowledgements 757 The author wishes to thank his colleagues in the PersID project for 758 their support. 760 9. References 762 9.1. Normative References 764 [I-D.ah-rfc2141bis-urn] 765 Hoenes, A., "Uniform Resource Name (URN) Syntax", 766 draft-ah-rfc2141bis-urn-00 (work in progress), March 2010. 768 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 769 Requirement Levels", BCP 14, RFC 2119, March 1997. 771 [RFC3406] Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom, 772 "Uniform Resource Names (URN) Namespace Definition 773 Mechanisms", BCP 66, RFC 3406, October 2002. 775 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 776 Specifications: ABNF", STD 68, RFC 5234, January 2008. 778 9.2. Informative References 780 [I-D.hakala-rfc3187bis-isbn-urn] 781 Huttunen, M., Hakala, J., and A. Hoenes, "Using 782 International Standard Book Numbers as Uniform Resource 783 Names", draft-hakala-rfc3187bis-isbn-urn-00 (work in 784 progress), March 2010. 786 [IANA-URI] 787 IANA, "URI Schemes Registry", 788 . 790 [IANA-URN] 791 IANA, "URN Namespace Registry", 792 . 794 [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, 795 April 1992. 797 [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997. 799 [RFC2288] Lynch, C., Preston, C., and R. Jr, "Using Existing 800 Bibliographic Identifiers as Uniform Resource Names", 801 RFC 2288, February 1998. 803 [RFC2483] Mealling, M. and R. Daniel, "URI Resolution Services 804 Necessary for URN Resolution", RFC 2483, January 1999. 806 [RFC2611] Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom, 807 "URN Namespace Definition Mechanisms", BCP 33, RFC 2611, 808 June 1999. 810 [RFC3044] Rozenfeld, S., "Using The ISSN (International Serial 811 Standard Number) as URN (Uniform Resource Names) within an 812 ISSN-URN Namespace", RFC 3044, January 2001. 814 [RFC3187] Hakala, J. and H. Walravens, "Using International Standard 815 Book Numbers as Uniform Resource Names", RFC 3187, 816 October 2001. 818 [RFC3188] Hakala, J., "Using National Bibliography Numbers as 819 Uniform Resource Names", RFC 3188, October 2001. 821 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 822 Resource Identifier (URI): Generic Syntax", STD 66, 823 RFC 3986, January 2005. 825 Authors' Addresses 827 Juha Hakala 828 The National Library of Finland 829 P.O. Box 15 830 Helsinki, Helsinki University FIN-00014 831 Finland 833 Email: juha.hakala@helsinki.fi 835 Alfred Hoenes (editor) 836 TR-Sys 837 Gerlinger Str. 12 838 Ditzingen D-71254 839 Germany 841 Email: ah@TR-Sys.de