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Network Working Group                                          J. HakalaRequest for Comments: 3187                   Helsinki University LibraryCategory: Informational                                     H. Walravens                                           The International ISBN Agency                                                            October 2001Using International Standard Book 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 International Standard Book Numbers   (ISBN) can be supported within the URN (Uniform Resource Names)   framework and the syntax for URNs defined inRFC 2141.  Much of the   discussion below is based on the ideas expressed inRFC 2288.1. Introduction   As part of the validation process for the development of URNs, the   IETF URN 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, et al.] investigated the feasibility of   using three identifiers (ISBN, ISSN and SICI) as URNs.  This document   will analyse the usage of ISBNs as URNs in more detail thanRFC 2288.   A registration request for acquiring Namespace Identifier (NID)   "ISBN" for ISBNs is included in chapter 5.Hakala & Walravens           Informational                      [Page 1]

RFC 3187                  Using ISBNs as URNs               October 2001   The document at hand is part of a global joint venture of the   national libraries to foster identification of electronic documents   in general and utilisation of URNs in particular.  The document was   written as a co-operative project between the Helsinki University   Library and The International ISBN Agency.   We have used the URN Namespace Identifier "ISBN" for ISBNs in   examples below.2. Identification vs. Resolution   As a rule the ISBNs identify finite, manageably-sized objects, but   these objects may still be large enough that resolution into a   hierarchical system is appropriate.   The materials identified by an ISBN 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 the national library's holdings.3. International Standard Book Numbers3.1 OverviewRFC 2288 [Lynch] describes the ISBN system in the following way:      An International Standard Book Number (ISBN) identifies an edition      of a monographic work.  The ISBN is defined by the standard      NISO/ANSI/ISO 2108:1992 [ISO1]      Basically, an ISBN is a ten-digit number (actually, the last digit      can be the letter "X" as well, as described below) which is      divided into four variable length parts usually separated by      hyphens when printed.  The parts are as follows (in this order):      *  a group identifier which specifies a group of publishers, based         on national, geographic or some other criteria,      *  the publisher identifier,      *  the title identifier,      *  and a modulus 11 check digit, using X instead of 10.Hakala & Walravens           Informational                      [Page 2]

RFC 3187                  Using ISBNs as URNs               October 2001      The group and publisher number assignments are managed in such a      way that the hyphens are not needed to parse the ISBN      unambiguously into its constituent parts.  However, the ISBN is      normally transmitted and displayed with hyphens to make it easy      for human beings to recognize these parts without having to make      reference to or have knowledge of the number assignments for group      and publisher identifiers.   Groups usually cover only one country, but occasionally a single   group is used in several countries.  For instance, group "3" is   utilised in Germany, Austria and German-speaking parts of   Switzerland.  "976" is used in Caribbean community (Antigua, Bahamas,   Barbados, Belize, Cayman Islands, Dominica, Grenada, Guyana, Jamaica,   Montserrat, St. Kitts-Nevis, St. Lucia, St. Vincent and the   Grenadines, Trinidad and Tobago, Virgin Islands (Br))and "982" in   South Pacific (Cook Islands, Fiji, Kiribati, Marshall Islands, Nauru,   Niue, Solomon Islands, Tokelau, Tonga, Tuvalu; Vanuatu, Western   Samoa).  For each international group, the International ISBN Agency   has assigned ranges of publisher identifiers to individual countries.   These ranges are listed on the ISBN web site (http://www.isbn.spk-berlin.de/html/prefix.htm).  The group identifiers are listed athttp://www.isbn.spk-berlin.de/html/prefix/allpref.htm.   There are plans to extend the ISBN into 13 digits in order to make   the system more suitable for identification of electronic monographs.   So called Bookland ISBN will consist of a traditional ISBN preceded   by the 978 or 979 EAN flag.3.2 Encoding Considerations and Lexical EquivalenceRFC 2288 [Lynch] says that:      Embedding ISBNs within the URN framework presents no particular      encoding problems, since all of the characters that can appear in      an ISBN are valid in the identifier segment of the URN.  %-      encoding, as described in [MOATS] is never needed.      Example: URN:ISBN:0-395-36341-1      For the ISBN namespace, some additional equivalence rules are      appropriate.  Prior to comparing two ISBN URNs for equivalence, it      is appropriate to remove all hyphens, and to convert any      occurrences of the letter X to upper case.Hakala & Walravens           Informational                      [Page 3]

RFC 3187                  Using ISBNs as URNs               October 20013.3 Resolution of ISBN-based URNs   The existing ISBN structure is suitable for URN resolution purposes.   The group identifier can assist in the resolver discovery process.   For instance, the group identifier "951" means Finland.  In this   case, the Finnish national bibliographic database will be able to   resolve the URN either into bibliographic data or - if the resource   is available in the Internet - to the document itself.   If a group identifier does not identify a single country but a   language area, there are two means for locating the correct national   bibliography.  First, it is possible to define a cascade of URN   resolution services - for instance, German national bibliography,   Austrian national bibliography and Swiss national bibliography, in   this order - into the DNS records describing the resolution service   for ISBNs starting with "3".  Second, the publisher identifier ranges   assigned by the International ISBN Agency could be defined into the   DNS records.  This method is better than cascading, since the correct   resolution service can be found immediately.   In some exceptional cases - notably in the US and in UK, where   international companies do a significant portion of publishing - the   information provided by the group identifier may not always be fully   reliable.  For instance, some monographs published in New York by   international publishing companies may get an ISBN with the group   identifier "3".  This is technically appropriate when the   headquarters or one of the offices of the publisher is located in   Germany.   Information about such a book will not be available in the German   national bibliography, but via the Library of Congress systems.   Unfortunately, the appropriate national bibliography cannot be known   to the resolver discovery service.   As a fall back mechanism a large union catalogue, such as WorldCat   maintained by OCLC (http://www.oclc.org ) could be used to complement   the default services provided by national bibliographies.   The problem described above may well be less severe than it looks.   Some international publishers (Springer, for example) give the whole   production to the national library of their home country as legal   deposit, no matter which country the book was published.  Thus   everything published by Springer in New York with group identifier   "3" will be found from the German national bibliography.  On the   other hand, when these companies give their home base also as a place   of publication, the "home" national library requires the legal   deposit.Hakala & Walravens           Informational                      [Page 4]

RFC 3187                  Using ISBNs as URNs               October 2001   Due to the intelligent structure of ISBN, group identifier or even   the publisher identifier can be used as a "hint".  Technically, it is   possible to incorporate into the common structure also URN resolution   services maintained by publishers.  For instance, "951-0" is the   unique ISBN publisher identifier of the largest publisher in Finland,   Sanoma-WSOY.  If they launch their own URN resolution services,   resolution requests for ISBNs starting with "951-0" will be directed   to the publisher's server, and all other requests to the national   bibliography.3.4 Additional considerations   The basic guidelines for assigning ISBNs to electronic resources are   the following:   *  Format/means of delivery is irrelevant to the decision whether a      product needs an ISBN or not.  If the content meets the      requirement, it gets an ISBN, no matter what the format of the      delivery system.   *  Each format of a digital publication should have a separate ISBN.   The definition of a new edition is normally based on one of the two   criteria:   *  A change in the kind of packaging involved: the hard cover      edition, the paperback edition and the library-binding edition      would each get a separate ISBN.  The same applies to different      formats of digital files.   *  A change in the text, excluding packaging or minor changes such as      correcting a spelling error.  Again, this criterion applies      regardless of whether the publication is in printed or in digital      form.   Although these rules seem very clear, their interpretation may vary.   As [Lynch] points out,      The choice of whether to assign a new ISBN or to reuse an existing      one when publishing a revised printing of an existing edition of a      work or even a revised edition of a work is somewhat subjective.      Practice varies from publisher to publisher (indeed, the      distinction between a revised printing and a new edition is itself      somewhat subjective).  The use of ISBNs within the URN framework      simply reflects these existing practices.  Note that it is likely      that an ISBN URN will often resolve to many instances of the work      (many URLs).Hakala & Walravens           Informational                      [Page 5]

RFC 3187                  Using ISBNs as URNs               October 2001   Publishers have also in some occasions re-used the same ISBN for   another book.  This reasonably rare kind of human error does not   threaten or undermine the value of the ISBN system as a whole.   Neither do they pose a serious threat to the URN resolution service   based on ISBNs.  An error will only lead into the retrieval of two or   more bibliographic records from a national bibliographic database.   Based on the information in the records, a user can choose the   correct record from the result set.   Most national bibliographies and especially the Books in Print   correct ISBN mistakes.  The systems then provide cross references   ("incorrect ISBN -> correct ISBN").   Further details on the process of assigning ISBNs can be found insection 5  (Namespace registration) below.4. Security Considerations   This document proposes means of encoding ISBNs within the URN   framework. ISBN-based URN resolution service is depicted here only in   a fairly generic level; thus questions of secure or authenticated   resolution mechanisms are excluded.  It does not deal with means of   validating the integrity or authenticating the source or provenance   of URNs that contain ISBNs.  Issues regarding intellectual property   rights associated with objects identified by the ISBNs 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 International Standard Book   Number (ISBN)   This registration describes how International Standard Book Numbers   (ISBN) can be supported within the URN framework.   Namespace ID:   ISBN   This Namespace ID is the same as the internationally known acronym   for the International Standard Book Number.  Giving NID "ISBN" to any   other identifier system would cause a lot of confusion.   Registration Information:   Version: 1   Date: 2001-01-25Hakala & Walravens           Informational                      [Page 6]

RFC 3187                  Using ISBNs as URNs               October 2001   Declared registrant of the namespace:   Name: Hartmut Walravens   E-mail: hartmut.walravens@sbb.spk-berlin.de   Affiliation: Director, The International ISBN Agency   Address: Staatsbibliothek zu Berlin - Preussischer Kulturbesitz -   D-10772 Berlin, Germany   Declaration of syntactic structure:   An ISBN is a ten-digit number (actually, the last digit can be the   letter "X" as well, as described below) which is divided into four   variable length parts usually separated by hyphens when printed.  The   parts are as follows (in this order):   *  a group identifier which specifies a group of publishers, based on      national, geographic or some other criteria,   *  the publisher identifier,   *  the title identifier,   *  and a modulus 11 check digit, using X instead of 10.   Example:   URN:ISBN:0-395-36341-1   Relevant ancillary documentation:   The ISBN (International Standard Book Number) is a unique machine-   readable identification number, which marks any edition of a book   unambiguously.  This number is defined in ISO Standard 2108.  The   number has been in use now for 30 years and has revolutionised the   international book-trade.  154 countries are officially ISBN members,   and more countries are joining the system.   The administration of the ISBN system is carried out on three levels:      International agency      Group agencies      Publisher levels   The International ISBN agency is located within the State Library   Berlin.  The main functions of the International ISBN Agency are:   *  To promote, co-ordinate and supervise the world-wide use of the      ISBN system.Hakala & Walravens           Informational                      [Page 7]

RFC 3187                  Using ISBNs as URNs               October 2001   *  To approve the definition and structure of group agencies.   *  To allocate group identifiers to group agencies.   *  To advise on the establishment and functioning of group agencies.   *  To advise group agencies on the allocation of international      publisher identifiers.   *  To publish the assigned group numbers and publishers prefixes in      up-to-date form.   More information about ISBN usage can be found from the ISBN Users'   Manual.  4th edition of this document is available athttp://www.isbn.spk-berlin.de/html/userman.htm.   Identifier uniqueness considerations:   ISBN that has been assigned once should never be re-used.   Nevertheless, publishers do occasionally re-use the same number.   From the point of the URN resolution system proposed here, this will   typically cause retrieval of two bibliographic records.  A user can   choose the correct publication using the data in the record, such as   the author or title.   Incorrect ISBNs are routinely corrected in national bibliographies   and Books in Print catalogue.   Identifier persistence considerations:   The ISBN accompanies a publication from its production onwards.  It   is persistent; ISBN once given - if correct - will never leave the   publication.   Identifier assignment process:   Assignment of ISBNs is always controlled by ISBN group agencies,   which are often national and quite frequently located in the national   libraries.  Publishers are usually given blocks of ISBNs, from which   they pick identifiers for their newly published items.   As pointed out earlier, in spite of the common rules of how to use   ISBNs, there is some variation between different publishers in ISBN   assignment.  In practice these differences are so small that they do   not pose a threat to the usability of the ISBN system.Hakala & Walravens           Informational                      [Page 8]

RFC 3187                  Using ISBNs as URNs               October 2001   Identifier resolution process:   URNs based on ISBNs will be primarily resolved via the national   bibliography databases.  Since ISBN group agencies are as a rule   located in national libraries, the national bibliography databases   cover almost every publication which does have an ISBN.   If group identifier does not define a country but a language area   there may be many countries using the same group identifier.  In such   cases, the International ISBN Agency has divided publisher   identifiers into ranges assigned to each country within the group.   The appropriate resolution service can be found by using the group   identifier and publisher identifier information.  Alternatively a   cascade of national bibliographies can be defined.   Resolution carried out in national bibliography databases may be   complemented by so called union catalogues, which contain huge amount   of bibliographic data (up to 42 million records).  This complementary   service is only needed if the ISBN group identifier information is   misleading.  This is not common.   The International ISBN Agency maintains a list of publishers who have   been assigned a publisher identifier within the ISBN system.  The   publisher identifier may be used to allow participation of resolution   services maintained by publishers into the URN resolution system for   ISBN.   Rules for Lexical Equivalence:   For the ISBN namespace, some additional equivalence rules are   appropriate.  Prior to comparing two ISBN URNs for equivalence, it is   appropriate to remove all hyphens, and to convert any occurrences of   the letter X to upper case.   Conformance with URN Syntax:   Embedding ISBNs within the URN framework presents no particular   encoding problems, since all of the characters that can appear in an   ISBN are valid in the identifier segment of the URN %-encoding, as   described in [MOATS] is never needed.      Example: URN:ISBN:0-395-36341-1   Validation mechanism:   Validity of an ISBN string can be checked by modulus 11 check digit,   included in the ISBN.  X is used instead of 10.Hakala & Walravens           Informational                      [Page 9]

RFC 3187                  Using ISBNs as URNs               October 2001   Validity of ISBN assignments can be checked from the group agencies   or directly from the publisher.   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 1997.7. Authors' Addresses   Juha Hakala   Helsinki University Library - The National Library of Finland   P.O. Box 26   FIN-00014 Helsinki University   FINLAND   EMail: juha.hakala@helsinki.fi   Hartmut Walravens   The International ISBN agency   Staatsbibliothek zu Berlin - Preussischer Kulturbesitz -   D-10772 Berlin   GERMANY   EMail: hartmut.walravens@sbb.spk-berlin.deHakala & Walravens           Informational                     [Page 10]

RFC 3187                  Using ISBNs 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 & Walravens           Informational                     [Page 11]

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