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Network Working Group                                          J. HakalaRequest for Comments: 3188                   Helsinki University LibraryCategory: Informational                                     October 2001Using National Bibliography Numbers asUniform Resource NamesStatus of this Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2001).  All Rights Reserved.Abstract   This document discusses how national bibliography numbers (persistent   and unique identifiers assigned by the national libraries) can be   supported within the URN (Uniform Resource Names) framework and the   syntax for URNs defined inRFC 2141.  Much of the discussion is based   on the ideas expressed inRFC 2288.1. Introduction   As part of the validation process for the development of URNs the   IETF working group agreed that it is important to demonstrate that   the current URN syntax proposal can accommodate existing identifiers   from well established namespaces.  One such infrastructure for   assigning and managing names comes from the bibliographic community.   Bibliographic identifiers function as names for objects that exist   both in print and, increasingly, in electronic formats.RFC 2288   [Lynch] investigated the feasibility of using three identifiers   (ISBN, ISSN and SICI) as URNs.   This document will analyse the usage of national bibliography numbers   (NBNs) as URNs.  The need to extend analysis to new identifier   systems was briefly discussed inRFC 2288 as well, with the following   summary: "The issues involved in supporting those additional   identifiers are anticipated to be broadly similar to those involved   in supporting ISBNs, ISSNs, and SICIs".Hakala                       Informational                      [Page 1]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   A registration request for acquiring a Namespace Identifier (NID)   "NBN" for national bibliography numbers has been written by the   National Library of Finland on the request of the Conference of   Directors of National Libraries (CDNL) and the Conference of the   European National Librarians (CENL).  Chapter 5 contains a URN   namespace registration request modeled according to the template inRFC 2611.   The document at hand is part of a global co-operation of the national   libraries to foster identification of electronic documents in general   and utilisation of URNs in particular.  Some national libraries,   including the national libraries of Finland, Norway and Sweden, are   already assigning NBN-based URNs for electronic resources.   We have used the URN Namespace Identifier "NBN" for the national   bibliographic numbers in examples below.2. Identification vs. Resolution   As a rule the national bibliography numbers identify finite,   manageably-sized objects, but these objects may still be large enough   that resolution to a hierarchical system is appropriate.   The materials identified by a national bibliography number may exist   only in printed or other physical form, not electronically.  The best   that a resolver will be able to offer in this case is bibliographic   data from a national bibliography database, including information   about where the physical resource is stored in a national library's   holdings.   The URN Framework provides resolution services that may be used to   describe any differences between the resource identified by a URN and   the resource that would be returned as a result of resolving that   URN.  However, NBNs will be used for instance to identify resources   in digital Web archives created by harvester robot applications.  In   this case, NBN will identify exactly the resource the user expects to   see.3. National bibliography numbers3.1 Overview   National Bibliography Number (NBN) is a generic name referring to a   group of identifier systems utilised by the national libraries and   only by them for identification of deposited publications which lack   an identifier, or to descriptive metadata (cataloging) that describes   the resources.  In many countries legal (or voluntary) deposit is   being extended to electronic publications.Hakala                       Informational                      [Page 2]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   Each national library uses its own NBN strings independently of other   national libraries; there is no global authority which controls them.   For this reason NBNs are unique only on national level.  When used as   URNs, NBN strings must be augmented with a controlled prefix such as   country code.  These prefixes guarantee uniqueness of the NBN-based   URNs on the global scale.   NBNs have traditionally been given to documents that do not have a   publisher-assigned identifier, but are cataloged to the national   bibliography.  NBNs can be seen as a fall-back mechanism: if no   other, better established identifier such as ISBN can be given, an   NBN is assigned.  In principle, NBN usage enables identification of   any Internet document.  Local policies may limit the NBN usage to a   much smaller subset of documents.   Some national libraries (e.g., Finland, Norway, Sweden) have   established Web-based URN generators, which enable authors and   publishers to fetch NBN-based URNs for their network documents.  At   least national libraries of Sweden and Finland are harvesting and   archiving domestic Web documents (and a number of other libraries   plan to start this activity), and long-time preservation of these   materials requires persistent and unique identification.  NBNs can be   and are in fact already used as internal identifiers in these Web   archives.   Both syntax and scope of NBNs can be decided by each national library   independently.  Typically, an NBN consist of one or more letters   and/or digits.  This simple syntax makes NBNs infinitely extensible   and very suitable for e.g., naming of the Web documents.  For   instance the application used by the national library of Finland for   Web harvesting creates NBNs which are based on the MD5 checksum of   the archived resource.3.2 F-code   F-code is the NBN used by the National Library of Finland.   F-codes have been used since early 20th century to identify catalogue   cards and later MARC records in the national bibliography.  In 1998   the national library decided to enable the Finnish authors and   publishers to assign F-codes to their Internet documents, if these   documents do not qualify for other identifiers such as ISBN.  F-   codes, embedded into URNs, can be fetched from the URN generator   (http://www.lib.helsinki.fi/cgi-bin/urn.pl) developed in co-operation   between the national library of Finland and the Lund University   library, NETLAB unit.  Attached to the generator there is a user   guide (http://www.lib.helsinki.fi/meta/URN-opas.html; only in   Finnish), which tells the users how to use URNs.Hakala                       Informational                      [Page 3]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   F-codes are also used within the Web harvesting and archiving   software (http://www.csc.fi/sovellus/nedlib/), which has been built   for the Networked European Deposit Library (NEDLIB) project (seehttp://www.kb.nl/nedlib).  NEDLIB harvester calculates MD5 checksum   for each archived resource, and then builds an NBN-based URN from the   checksum.  The URN serves then as a unique identifier to the archived   resource.  Traditional identifiers can not be used for this purpose,   since there may for instance be several variants of a book which   (quite rightly so) all have the same ISBN.  Moreover, identifiers   embedded into a document do not necessarily belong to the document   itself; thus the Web archiving application can not trust the   identifiers embedded into the body of the document.   The F-code built by the URN generator consist of:   Prefix (for example fe)   Year (YYYY; for example 1999)   Number (for example 1055)   The generator also adds namespace identifier "NBN" and ISO 3166   country code.  Thus a URN based on F-code would in this case be for   instance urn:nbn:fi-fe19991055.   URNs created by the Web archiving application have similar overall   structure, except that prefix (which may be defined by the operator)   is fea and year is not used.  An example:  urn:nbn:fi-fea-   5c5875e6e49ae649cad63e5ee4f6c346.   F-codes never need any special encoding when used as URNs, since they   consist of alphanumeric codes only (0-9, a-z).  This is often the   case for other national libraries' NBN systems as well.3.3 Encoding Considerations and Lexical Equivalence   Embedding NBNs within the URN framework usually presents no   particular encoding problems, since all of the characters that can   appear in commonly used NBN systems can be expressed in special   encoding, as described inRFC 2141 [MOATS].   When an NBN is used as a URN, the namespace specific string will   consist of three parts: prefix, consisting of either a two-letter ISO   3166 country code or other registered string, delimiting character   which is either hyphen (-) or colon (:), and NBN string assigned by   the national library.  Delimiting characters are not lexically   equivalent.   Hyphen is always used for separating the prefix and the NBN string.Hakala                       Informational                      [Page 4]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   Colon is used as the delimiting character if and only if a country   code-based NBN namespace is split further in smaller sub-namespaces.   If there are several national libraries in one country, these   libraries can split their national namespace into smaller parts using   this method.   A national library may also assign a trusted organisation(s) its own   sub-namespace.  For instance, the national library of Finland has   given Statistics Finland (http://www.stat.fi/index_en.html) a sub-   namespace "st" (e.g., urn:nbn:fi:st:).  The Finnish Council of State   (http://www.vn.fi/vn/english/index.htm) will use sub-namespace "vn"   (e.g., urn:nbn:fi:vn).   Non-ISO 3166-prefixes, if used, must be registered on the global   level. The Library of Congress will maintain the central register of   reserved codes.  This register will be available to the national   libraries and other users in the Web.   Sub-namespace codes beneath a country-code-based namespace need to be   registered on the national level by the national library which   assigned the code.  The national register must be available in the   Web and should also be linked to the global register maintained by   the Library of Congress.   Two-letter codes may not be used as non-ISO prefixes, since all such   codes are reserved for existing and possible future ISO country   codes. If there are several national libraries in one country who use   the same prefix - for instance, a country code -, they need to agree   on how to split the namespace between them.   Models:   URN:NBN:<ISO 3166 country code>-<assigned NBN string>   URN:NBN:<ISO 3166 country code>:<sub-namespace code>-<assigned NBN   string>   URN:NBN:<non-ISO 3166 prefix>-<assigned NBN string>   Examples:   URN:NBN:fi-fe19981001 (A "real" URN assigned by the National Library   of Finland).3.4 Resolution of NBN-based URNs   The (usually) country code-based prefix part of the URN namespace   specific string will provide a guide to where to find a resolution   service, and the NBN register will identify the assigning agency.   Once the NBN-based URN resolution is in global usage, the number of   prefixes will slowly approach and may eventually exceed the number of   national libraries.Hakala                       Informational                      [Page 5]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   If NBN assignment for a given country is limited to the national   bibliography database, then all NBN-based URNs for that country will   be resolved there.  In one model these databases contain detailed   resource descriptions including URLs, which will point both to the   copy of the document in the Internet and to the copy in the national   library's (legal) deposit collection.  Due to the limitations in the   usage of legal deposit documents it is possible that the deposited   electronic materials can not be delivered in electronic form outside   the premises of the national library.   If it is possible for the authors and publishers to retrieve NBNs to   Web documents and there is no obligation to deposit thus identified   documents to the national library, URN resolution service is not   possible without a national Web index and archive, maintained by the   national library or other organisation(s).  A Web index/archive will   also resolve machine-generated URNs to the archived Web documents.3.5 Additional considerations   Guidelines adopted by each national library define when different   versions of a work should be assigned the same or differing NBNs.   These rules apply only if identifier assignment is done manually.  If   identifiers are allocated programmatically, the only criteria that   can be used is that two documents which are identical on the bit   level (have the same MD5 checksum) are deemed identical and should   receive the same NBN.  The likelihood of this happening to dissimilar   documents is about 2^64, according to theRFC 1321.   The rules governing the usage of NBNs are less strict than those   specifying the usage of ISBN or other, better established   identifiers. Since the NBNs have up to now been given only by the   personnel (cataloguers) working in the national libraries, the   identifier assignment has in practice been well co-ordinated.   A NBN-based URN will resolve to single instance of the work if   identifier assignment has been automatic.  Given the nature of NBNs   it is also likely that different versions of the same work will   receive different NBNs even if the identifier is given manually.4. Security Considerations   This document proposes means of encoding several existing   bibliographic identifiers within the URN framework.  This document   does not discuss resolution except at a very generic level; thus   questions of secure or authenticated resolution mechanisms are out of   scope.  It does not address means of validating the integrity or   authenticating the source or provenance of URNs that contain   bibliographic identifiers.  Issues regarding intellectual propertyHakala                       Informational                      [Page 6]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   rights associated with objects identified by the various   bibliographic identifiers are also beyond the scope of this document,   as are questions about rights to the databases that might be used to   construct resolvers.5. Namespace registration   URN Namespace ID Registration for the National Bibliography Number   (NBN)   Namespace ID:   NBN   This Namespace ID has been in production use in demonstrator systems   since summer 1998; thousands of URNs from this namespace have already   been delivered in Finland, Sweden and Norway.   Registration Information:   Version: 3   Date: 2001-01-30   The first registration of the NID "NBN" was done via the URN WG in   1998. The second, slightly edited registration request was done in   1999.   Declared registrant of the namespace:   Name: Juha Hakala   E-mail: juha.hakala@helsinki.fi   Affiliation: Helsinki University Library - The National Library of   Finland, Conference of European National Librarians (CENL) and   Conference of Directors of National Libraries (CDNL)   Address: P.O.Box 26, 00014 Helsinki University, Finland   Both CENL and CDNL made decisions to foster the usage of URNs during   1998.  The latter organisation has set up a working group for this   purpose.  One item in the common work plan is utilisation of national   bibliography numbers as URNs for identification of grey literature   published in the Internet.  The NBN namespace will be available for   free for all national libraries in the world.   Declaration of syntactic structure:Hakala                       Informational                      [Page 7]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   The namespace specific string will consist of three parts:   prefix, consisting of either a two-letter ISO 3166 country code or   other registered string and sub-namespace codes,   delimiting characters (colon (:), or hyphen (-), and   NBN string assigned by the national library.   Colon is used as a delimiting character only within the prefix,   between ISO 3166 country code and sub-namespace code, which splits   the national namespace into smaller parts.  This technique can be   used when there are several national libraries, which all need their   own namespaces, or when the national library allows trusted partners   to set up their own sub-namespaces within the national NBN namespace.   Dividing non-ISO 3166-based namespaces further with sub-namespace   codes is not allowed.   Hyphen is used as a delimiting character between the prefix and the   NBN string.  Within the NBN string, hyphen can be used for separating   different sections of the code from one another.   Non-ISO prefixes used instead of the ISO country code must be   registered.  A global registry, maintained by the Library of   Congress, will be created and made available via the Web.  Contact   information: nbn.register@loc.gov.us.   All two-letter codes are reserved for existing and possible future   ISO country codes and may not be used as non-ISO prefixes.   Sub-namespace codes must be registered on the national level by the   national library which assigned the code.  The register must be   available via the Web, and it should be accessible via the global   registry set up by the Library of Congress.   Models:   URN:NBN:<ISO 3166 country code>-<assigned NBN string>   URN:NBN:<ISO 3166 country code:sub-namespace code>-<assigned NBN   string>   URN:NBN:<non-ISO 3166 prefix>-<assigned NBN string>   Example:   A country code-based URN: URN:NBN:fi-fe19981001 (A URN assigned by   the National Library of Finland).Hakala                       Informational                      [Page 8]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   Relevant ancillary documentation:   National Bibliography Number (NBN) is a generic name referring to a   group of identifier systems used by the national libraries for   identification of deposited publications which lack an identifier, or   to descriptive metadata (cataloguing) that describes the resources.   Each national library uses its own NBN system independently of other   national libraries; there is no global authority which controls   syntax of these identifier systems.   Each national library can decide freely which resources will receive   NBNs.  These identifiers have traditionally been assigned to   documents that do not have a publisher-assigned identifier, but are   nevertheless catalogued to the national bibliography.  Typically   identification of grey publications have largely been dependent on   NBNs.   Some national libraries (Finland, Norway, Sweden) have established   Web-based URN generators, which enable authors and publishers to   fetch NBN-based URNs for their network documents.   Both syntax and scope of NBNs is decided by each national library   independently.  Typically, a NBN consist of one or more letters and a   number.   Identifier uniqueness considerations:   NBN strings assigned by two national libraries may be identical.  For   this reason usage of a controlled prefix in the namespace specific   string is obligatory in order to guarantee global uniqueness of NBN-   based URNs.   In the national level, libraries utilise different policies for   guaranteeing uniqueness.  A national library may automate the   delivery of NBN-based URNs.  In this case, the NBNs are assigned   sequentially by a program (URN generator).   Identifier persistence considerations:   Persistence of the NBNs as identifiers is guaranteed by the   persistence of national libraries and information systems, such as   national bibliographies, maintained by them.  NBNs have been used for   several centuries for printed materials.  NBN-based identification of   electronic documents is a recent practice, but it is likely to   continue for a very long time.Hakala                       Informational                      [Page 9]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   Process of identifier assignment:   Assignment of NBN-based URNs is always controlled on national level   by the national library / national libraries.  The Conference of   Directors of National Librarians (CDNL) has established in 1999 a   task force, which will co-ordinate the URN usage in all national   libraries.   National libraries may choose different strategies in assigning NBN-   based URNs.  One option is assignment by the library personnel only.   This is done when the document is catalogued into the national   bibliography.  Thus in this case the national bibliography database   will serve as the URN resolution service.   A national library may also set up a URN generator (generators), and   allow publishers and authors to retrieve NBN-based URNs from there.   In this case there is no guarantee that the identified resource will   ever be catalogued into the national bibliography, and URN resolution   is dependent on Web index/archive.   Process for identifier resolution:   URNs based on NBNs will be primarily resolved via the national   bibliography databases.  In one model these databases contain   detailed resource descriptions including URLs, which will point both   to the copy of the document in the Internet and to the copy in the   national library's (legal) deposit collection.  Due to the   limitations in the usage of legal deposit documents it is possible   that the deposited materials can not be delivered outside the   premises of the national library.   For those documents not catalogued into the national bibliography   database URN resolution may take place via national or international   Web indexes and/or archives.  Nordic national libraries have   established in autumn 2000 a joint initiative called Nordic Web   Archive (NWA), which aims at creating a national Web archive into all   Nordic countries. Indexes to these archive systems will be able to   act as URN resolution services of any document which a) is or has   been available via the Web, and b) had an URN embedded into it.   Country code and additional sub-namespace information will provide a   guide to where to find appropriate resolution services.  For   instance, if the country code is "fi", the primary resolution service   is the national bibliography database.  Secondary resolution service   is the Web archive.Hakala                       Informational                     [Page 10]

RFC 3188      Using National Bibliography Numbers as URNs   October 2001   Generally, there will be one or more resolution services specified   for each country, depending on the assignment policy and services of   the national library.  If NBN assignment is limited to the national   bibliography database, then all NBN-based URNs for that country will   be resolved there.  If the authors and publishers have been allowed   to retrieve NBNs to their Web resources, URN resolution services   require a national Web archive.  If other organisations have been   allowed to assign NBNs, they may also set up their own URN resolution   services.   Rules for Lexical Equivalence:   None in the global level.  Any national library may provide its own   rules, on the basis of its NBN syntax.   Conformance with URN Syntax:   All NBNs we know of are ASCII strings consisting of letters (a-z) and   numbers (0-9).  If NBN contains characters that are reserved in the   URN syntax, this data must be presented in hex encoded form as   defined inRFC 2141.  A national library may limit the full scope of   its NBN strings in URN usage in such a way that there are no reserved   characters in the URN namespace specific strings.   Validation mechanism:   None specified on the global level.  A national library may use NBNs,   which contain a checksum and can therefore be validated, but this is   for the time being not a common practice.   Scope:   Global.6. References   [Daigle] Daigle, L., van Gulik, D., Iannella, R. and P. Faltstrom,            "URN Namespace Definition Mechanisms",RFC 2611, June 1999.   [Lynch]  Lynch, C., Preston, C. and R. Daniel, "Using Existing            Bibliographic Identifiers as Uniform Resource Names",RFC2288, February 1998.   [Moats]  Moats, R., "URN Syntax",RFC 2141, May 1997.Hakala                       Informational                     [Page 11]

RFC 3188      Using National Bibliography Numbers as URNs   October 20017. Author's Address   Juha Hakala   Helsinki University Library - The National Library of Finland   P.O. Box 26   FIN-00014 Helsinki University   FINLAND   EMail: juha.hakala@helsinki.fiHakala                       Informational                     [Page 12]

RFC 3188      Using National Bibliography Numbers as URNs   October 20018. Full Copyright Statement   Copyright (C) The Internet Society (2001).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Hakala                       Informational                     [Page 13]