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rfc:rfc3187

Network Working Group J. Hakala Request for Comments: 3187 Helsinki University Library Category: Informational H. Walravens

                                         The International ISBN Agency
                                                          October 2001
            Using International Standard Book Numbers as
                       Uniform Resource Names

Status 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 in RFC 2141.  Much of the
 discussion below is based on the ideas expressed in RFC 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 than RFC 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 Numbers

3.1 Overview

 RFC 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 at
 http://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 Equivalence

 RFC 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.

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3.3 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.

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 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).

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 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 in
 section 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: 2001-01-25

Hakala & 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 at
 http://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.

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 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", RFC
          2288, 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.de

Hakala & Walravens Informational [Page 10] RFC 3187 Using ISBNs as URNs October 2001

8. 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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