IETF                                                         M. Huttunen
Internet-Draft                                                 J. Hakala
Obsoletes: 3187 (if approved)            The National Library of Finland
Updates: 2288 (if approved)                               A. Hoenes, Ed.
Intended status: Standards Track                                  TR-Sys
Expires: September 23, 2010                               March 22, 2010

  Using International Standard Book Numbers as Uniform Resource Names


   The International Standard Book Number, ISBN, is a widely used
   identifier for monographic publications.  Since 2001, there has been
   a URN (Uniform Resource Names) namespace for ISBNs.  The namespace
   registration was performed in RFC 3187 and applies to the ISBN as
   specified in the original ISO Standard 2108-1992.  To allow for
   further growth in use, the successor ISO Standard, ISO 2108-2005, has
   defined an expanded format for the ISBN, known as "ISBN-13".  This
   document replaces RFC 3187 and defines how both the old and new ISBN
   standard can be supported within the URN framework and the syntax for
   URNs defined in RFC 2141.  An updated namespace registration is
   included, which describes how both the old and the new ISBN format
   can share the same namespace.


   This draft version is the outcome of work started in 2008 and brought
   to the IETF as a contribution to a much larger effort to revise the
   basic URN RFCs, in order to bring them in alignment with the current
   URI Standard (STD 63, RFC 3986), ABNF, and IANA guidelines, and to
   establish a modern URN resolution system for bibliographic

   Until a more specific mailing list is established, comments are
   welcome on the mailing list (or sent to the

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   other groups may also distribute working documents as Internet-

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   it for publication as an RFC or to translate it into languages other
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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions used in this document  . . . . . . . . . . . . . .  5
   3.  Identification and Resolution  . . . . . . . . . . . . . . . .  5
   4.  International Standard Book Numbers  . . . . . . . . . . . . .  5
     4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  5
       4.1.1.  ISBN-10 Structure  . . . . . . . . . . . . . . . . . .  5
       4.1.2.  ISBN-13 Structure  . . . . . . . . . . . . . . . . . .  6
       4.1.3.  Relation between ISBN-10 and ISBN-13 . . . . . . . . .  6
     4.2.  Encoding Considerations  . . . . . . . . . . . . . . . . .  7
     4.3.  Resolution of ISBN-based URNs  . . . . . . . . . . . . . .  7
       4.3.1.  General  . . . . . . . . . . . . . . . . . . . . . . .  7
       4.3.2.  Practical Aspects  . . . . . . . . . . . . . . . . . .  8
     4.4.  Additional Considerations  . . . . . . . . . . . . . . . . 10
   5.  URN Namespace Registration and Use . . . . . . . . . . . . . . 11
     5.1.  URN Namespace ID Registration for the International
           Standard Book Number (ISBN)  . . . . . . . . . . . . . . . 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 15
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 16

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1.  Introduction

   One of the basic permanent URI schemes (cf. RFC 3986 [RFC3986],
   [IANA-URI]) is 'URN' (Uniform Resource Name) as defined in RFC 2141
   [RFC2141].  Any identifier, when used within the URN system, needs
   its own namespace.  As of this writing, there are 40 registered URN
   namespaces (see [IANA-URN]), one of which belongs to ISBN,
   International Standard Book Number, as specified 2001 in RFC 3187

   Since 2007, there have been two variants of ISBN in use; an outdated
   one based on ISO 2108-1992 [ISO1] and a new one defined in ISO 2108-
   2005 [ISO2].  These versions shall subsequently be called "ISBN-10"
   and "ISBN-13", respectively, in this document.  For the time being,
   both ISBNs may still be printed on a book, but the ISBN-13 is the
   actual identifier.  If what is said in this document applies to both
   ISBN versions, the term "ISBN" is used.

   As part of the validation process for the development of URNs, the
   IETF URN working group agreed that it is important to demonstrate
   that a 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
   [RFC2288] investigated the feasibility of using three identifiers
   (ISBN, ISSN and SICI) as URNs, with positive results, however it did
   not formally register corresponding URN namespaces.  This was in part
   due to the still evolving process to formalize criteria for namespace
   definition documents and registration, consolidated later in the IETF
   into RFC 3406 [RFC3406].

   URN Namespaces have subsequently been registered for both ISBN and
   ISSN in RFCs 3187 [RFC3187] and 3044 [RFC3044], but not for SICI, due
   to both the identifier's limited popularity and its complicated URN
   resolution process.

   Guidelines for using ISBN-10s (based on ISO 2108-1992) as URNs and
   the original namespace registration have been published in RFC 3187
   [RFC3187].  The RFC at hand replaces RFC 3187; sections related to
   ISBN-13 have been added, all ISBN-10 information has been updated and
   the namespace registration revised to make it compliant with both
   ISBN versions and stipulations of RFC 3406 [RFC3406], which has
   replaced RFC 2611 [RFC2611] applied in the initial registration.

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2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

   "ISBN-10" refers to the original, 10-digit ISBN scheme specified in
   ISO 2108-1992 [ISO1].

   "ISBN-13" refers to the current, 13-digit ISBN scheme specified in
   ISO 2108-2005 [ISO2].

3.  Identification and Resolution

   As a rule, 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.  In such
   a case, the URN:ISBN resolver should nevertheless be able to supply
   bibliographic data, possibly including information about where the
   physical resource is stored in the owning institution's holdings.
   There may be other resolution services supplying a wide variety of
   information resources or services related to the identified books.

   National libraries shall be among the organizations providing
   persistent URN resolution services for monographic publications,
   independent of their form.

4.  International Standard Book Numbers

4.1.  Overview

   An International Standard Book Number (ISBN) identifies a product
   form or edition of a monographic publication.

4.1.1.  ISBN-10 Structure

   The ISBN-10 is defined by the ISO Standard 2108-1992 [ISO1].  It is a
   ten-digit number (the last digit can be the letter "X" as well) which
   is divided into four variable length parts usually separated by
   hyphens when printed.  The parts are as follows (in this order):

   o  a group identifier which specifies a group of publishers, based on
      national, geographic, or some other criteria;

   o  the publisher identifier;

   o  the title identifier; and

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   o  a modulo 11 check digit, using X instead of 10; the details of the
      calculation are specified in [ISO1].

   ISBN-10 was in use from 1970s until ISBN-13 replaced it in January

4.1.2.  ISBN-13 Structure

   ISBN-13 is defined by the ISO Standard 2108-2005 [ISO2].  The ISBN-13
   is a thirteen-digit number which is divided into five parts usually
   separated by hyphens when printed.  The first and the last part have
   a fixed lenght, but the other parts have variable length.  These
   parts are as follows (in this order):

   o  a prefix element of ISBN-13 is a 3 digit prefix (at the time of
      this writing, legal values were 978 and 979; future versions of
      the standard may define additional values) specified by the
      International ISBN Agency;

   o  a registration group element that specifies the registration
      group; it identifies the national, geographic, language, or other
      such grouping within which one or more ISBN Agencies operate;

   o  the registrant element;

   o  the publication element; and

   o  a modulo 10 check digit; the details of the calculation are
      specified in [ISO2].

4.1.3.  Relation between ISBN-10 and ISBN-13

   The structural differences between the ISBN-10 and ISBN-13 are the
   prefix element (which did not exist in the old ISBN) and the check
   digit calculation algorithm, which was modulo 11 in ISBN-10 and is
   now modulo 10.

   Terminology in ISBN-10 differs substantially from the terminology
   applied in ISBN-13.  In this document, ISBN-13 terminology shall be
   used from now on; for a reader used to ISBN-10 terminology, the
   following mapping may be useful:

   o  the group identifier = the registration group element;

   o  the publisher identifier = the registrant element;

   o  the title identifier = the publication element.

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   Any ISBN-10 can be converted to ISBN-13 form, and retrospective
   conversion is indeed a recommended practice in ISO 2108-2005.  Any
   application processing ISBN-based URNs should however be prepared to
   deal with both ISBNs, since ISBN-10 numbers may not be converted to
   the new form.  ISBN-13s using prefix element 979 can not be converted
   back to ISBN-10, since in these ISBNs group identifiers will be re-
   assigned.  New books may still have ISBN-10 alongside ISBN-13 for
   practical reasons, but only as long as the prefix element in ISBN-13
   is 978.

4.2.  Encoding Considerations

   Embedding ISBNs within the URN framework does not present encoding
   problems, since all of the characters that can appear in an ISBN are
   valid in the namespace-specific string (NSS) part of the URN.
   %-encoding, as described in RFC 2141 [RFC2141], is never needed.

      Example 1: URN:ISBN:978-0-395-36341-6

      Example 2: URN:ISBN:951-0-18435-7

      Example 3: URN:ISBN:951-20-6541-X

4.3.  Resolution of ISBN-based URNs

4.3.1.  General

   For URN resolution purposes, all elements except the check digit (now
   0-9, previously 0-9 or X) must be taken into account.  The
   registration group and registrant element 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
   humans to recognize these elements without having to make reference
   to or have knowledge of the number assignments for registration group
   and registrant elements.  In ISBN-10, registration group element
   codes such as 91 for Sweden were unique.  In ISBN-13 only the
   combination of prefix and registration group elements is guaranteed
   to be unique. 978-951 and 978-952 both mean Finland, but 979-951 and
   979-952 almost certainly will not; registration group element(s) for
   Finland are not yet known for ISBNs starting with 979.

   The Finnish URN registry is maintained by the national library.  The
   service is capable of resolving ISBN-based URNs.  URNs starting with
   URN:ISBN:978-951 or URN:ISBN:978-952 are mapped into appropriate URL
   addresses in a table maintained within the registry.  Applications,
   such as the national bibliography or the open archive of a
   university, can use the URN as the address of the resource.  There is

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   just one place (the registry) where the location information must be
   kept up to date.

   ISBN-13 prefix / registration group element combinations (and the
   corresponding ISBN-10 registration group identifiers, if any) usually
   designate a country, but occasionally a single combination / ISBN-10
   group identifier is used to indicate a language area.  For instance,
   "978-3" (or "3" in ISBN-10) is utilised in Germany, Austria, and the
   German speaking parts of Switzerland.  As of this writing, there are
   two regional registration groups: "978-976" is used in the Caribbean
   community and "978-982" in the South Pacific (see [PREFIX]).

   Note that the prefix and registration group element combination
   "979-3" has not yet been assigned.  There is no intention to allocate
   the registration group elements in the same way as was done with

   The registrant element may or may not be used for resolution
   purposes, depending on whether individual publishers have set up
   their resolution services.

   The publication element shall enable targeting the individual

4.3.2.  Practical Aspects

   Due to the lack of URN support in, e.g., web browsers, the URNs are
   usually expressed as URLs when embedded in documents.  The Finnish
   URN registry is located at, and URNs are therefore
   expressed in the form<URN>.  For example, the URN identifies Sami Nurmi's
   doctoral dissertation "Aspects of Inflationary Models at Low Energy

   The Finnish URN registry can not resolve URN:ISBNs with non-Finnish
   registration group element values until other countries establish
   their registries, and all these services become aware of each other
   and their respective registration group responsibility domains and
   are able to communicate with each other.  Thus the Finnish registry
   can deal with URN:ISBN instances with registration group element
   value 91 (indicating Sweden) if and only if the Swedish registry
   exists, its address is known to the Finnish peer and the Swedish
   service is capable of receiving and processing requests from other

   If a registration group element does not identify a single country
   but a language area, there are at least two means for locating the
   correct national bibliography.  First, it is possible to define a

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   cascade of URN registries - for instance, German, Austrian and Swiss
   national registries, in this order - which should collectively be
   aware of resolution services such as national bibliographies for
   ISBN-13s starting with "978-3".  If the German registry is not able
   to find an authoritative resolution service, the request could be
   passed to the Austrian one, and if there are still no hits, finally
   to the Swiss service.

   Second, the registrant element ranges assigned to the publishers in
   Germany, Austria and Switzerland by the ISBN Agencies could be
   defined directly into the national registries.  This method would be
   more efficient than cascading, since the correct resolution service
   would be known immediately.  The choice between these two and
   possible other options should be made when the establishment of the
   European network of URN registries reaches this level of maturity.

   In some exceptional cases -- notably in the US and in the 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
   registration group element "3".  This is technically appropriate when
   the headquarters or one of the offices of the publisher is located in

   Information about such a book may not always be available in the
   German national bibliography, but via the Library of Congress
   systems.  Unfortunately, the German/Austrian/Swiss URN registries
   that should in this case be contacted may not be aware of the
   appropriate resolution service.

   However, the problem posed by the international publishers 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 registration group element "3" should be
   resolvable via 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.

   A large union catalogue, such as WorldCat maintained by OCLC
   [OCLC-WC] could be used to complement the resolution services
   provided in the national level, or as the default service, if no
   national services exist or are known to the registry from which the
   query originates.

   Due to the semantic structure of ISBN-13, even the registrant element

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   can be used as a "hint".  Technically, it is possible to establish a
   number of URN resolution services maintained by different kinds of
   organizations.  For instance, "978-951-0" is the unique ISBN
   registrant element of the largest publisher in Finland, Sanoma-WSOY.
   Resolution requests for ISBNs starting with "978-951-0" can be passed
   to and dealt with the publisher's server, if and when it is made URN-
   aware.  In such a case, resolving the same URN in multiple locations
   may provide different services; the national bibliography may be able
   to provide bibliographic information only, while the publisher can
   also provide the book itself, on its own terms.  Different resolution
   services may co-exist and complement one another.  Same ISBN may be
   resolved both as URN and as a Digital Object Identifier (DOI)
   [DOIHOME].  URN-based services hosted by, e.g., a national library,
   might provide only bibliographic data, whereas a service based on the
   DOI system provided by the publisher might deliver the book, parts of
   the book or various services related to the work.

   Persistence of resolution services is largely dependent on
   persistence of organizations providing them.  Thus some services,
   independent on base technology chosen, may disappear or their content
   may change much sooner than some peer solutions.

4.4.  Additional Considerations

   The basic guidelines for assigning ISBNs to electronic resources are
   the following:

   o  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.

   o  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 clear, their interpretation may vary.  As
   RFC 2288 [RFC2288] points out,

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      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 may resolve to many instances of the work (many

   These instances may be fully identical, or there may be some minor
   differences between them.  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 should only lead into
   the retrieval of two or more bibliographic records describing two
   different monographic publications.  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").  This should be taken into account
   in the URN resolution process.  Further details on the process of
   assigning ISBNs can be found in section 5 (Namespace registration)

5.  URN Namespace Registration and Use

   The formal URN Namespace Identifier Registration for the pre-2005
   version of the International Standard Book Number (ISBN) was done in
   RFC 3187 [RFC3187].

   The new ISBN standard does not require a new namespace, but the
   registration is renewed here, as the registrant organization has
   moved from Staatsbibliothek zu Berlin - Preussischer Kulturbesitz to
   The International ISBN Agency, London, U.K, and the syntax and
   resolution details are amended.

5.1.  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.

   [ RFC Editor: please replace "XXXX" in all instances of "RFC XXXX"
   below by the RFC number assigned to this document. ]

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   Namespace ID:  ISBN

      This Namespace ID has already been assigned to the International
      Standard Book Number in January 2001 when the namespace was
      registered for the first time.

   Registration Information:

      Version: 2
      Date: 2010-03-22

   Declared registrant of the namespace:

      Name: Mr. Brian Green
      Affiliation: Director, The International ISBN Agency
      Affiliation: EDItEUR, 39-41 North Road,London, N7 9DP, U.K.
      Web URL:

   Declaration of syntactic structure:

      The namspace-specific string of 'ISBN' URNs is either an ISBN-13
      (see Section 4.1.2 of RFC XXXX) or an ISBN-10 (see Section 4.1.1
      of RFC XXXX); the former is preferred.

      Example 1: URN:ISBN:978-0-395-36341-6
      Example 2: URN:ISBN:951-0-18435-7
      Example 3: URN:ISBN:951-20-6541-X

   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. 170 countries and territories are
      officially ISBN members, and more of them are joining the system.

      The administration of the ISBN system is carried out on three
         International agency,
         Group agencies,
         Publisher levels.

      The International ISBN agency is located in London.  The main
      functions of the Agency are:

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      *  To promote, co-ordinate and supervise the world-wide use of the
         ISBN system.

      *  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

      *  To advise group agencies on the allocation of international
         publisher identifiers.

      *  To publish the assigned group numbers and publisher prefixes in
         up-to-date form.

      Information about ISBN usage in general can be found from the ISBN
      FAQ, available at .

   Identifier uniqueness an persistence considerations:

      ISBN is a unique and persistent identifier.  An ISBN, once it has
      been assigned, must never be re-used for another book.  Moreover,
      a single manifestation of a book must never get a new ISBN.

      There may be multiple manifestations of a single literary work
      such as a novel.  In such case each manifestation shall receive a
      different ISBN.  ISO has developed a new standard, ISTC
      (International Standard Text Code, ISO 21047-2009) which enables
      identification of textual works.  See for more information.  In the
      standard itself, annex E describes the relations between ISBN and
      other publication identifiers and ISTC.

   Process of identifier assignment:

      Assignment of ISBNs is controlled.  There are three levels of
      control: the international agency, group agencies which typically
      operate in the national level and finally each publisher is
      responsible of using the ISBN system correctly.  Small publishers
      may demand ISBN numbers one at a time by contacting the ISBN group
      agency.  Large publishers receive ISBN blocks from which they
      allocate ISBNs to the books according to the ISBN assignment

   Process for identifier resolution:

      See Section 4.3 of RFC XXXX.

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   Rules for lexical equivalence:

      ISBN numbers are usually printed with the letters 'ISBN' and a
      single blank preceding them (for instance: ISBN 951-746-795-8).
      The data preceding the actual number must be removed before the
      ISBNs are analysed.  The ISBN serves directly as the namespace-
      specific string (NSS) of 'ISBN' URNs.

      Prior to comparing the NSS of two ISBN-based URNs for equivalence,
      all hyphens should be removed and letter 'X' capitalized.  Prior
      to comparing a URN based on ISBN-10 with a URN based on ISBN-13,
      the ISBN-10 must be converted to the ISBN-13 form.  This step is
      necessary since the ISBN-10s may or may not be already converted
      to the new form; as a rule, libraries shall keep the old ISBN
      since it is the one printed in books published prior to 2007,
      while publishers may convert the old identifiers originally
      assigned in ISBN-10 form and use the equivalent ISBN-13s in
      unchanged reprints of the books, which according to the ISBN
      assignment rules should not receive a new ISBN.

      The URNs are equivalent if the normalized forms obtained this way
      compare equal.

   Conformance with URN syntax:

      Legal ISBN characters are 0-9 and hyphen for ISBN-13 and 0-9 and X
      for ISBN-10.  No hex encoding is needed.

   Validation mechanism:

      The check digit helps to assure the correctness of an ISBN number
      assigned for a book when it has been entered or processed by a
      human.  Applications processing bibliographic data such as
      integrated library systems typically can check the correctness of
      both ISBN-10 and ISBN-13 (and make conversions between the two).
      If the number is wrong due to, e.g., a typing error made by a
      publisher, a correct ISBN is usually assigned afterwards.
      Although the book shall only contain the wrong number, national
      bibliography and system used by the book trade often to contain
      both the wrong and new, correct ISBN number.


      ISBN is a global identifier system used for identification of
      monographic publications.  It is very widely used and supported by
      the publishing industry.

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6.  Security Considerations

   This document proposes means of encoding ISBNs within the URN
   framework.  An ISBN-based URN resolution service is depicted here
   both for ISBN-10 and ISBN-13, but 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.

7.  IANA Considerations

   IANA is asked to update the existing registration of the Formal URN
   Namespace 'ISBN' using the template given above in Section 5.1.

8.  Acknowledgements

   This draft version is the outcome of work started in 2008 and brought
   to the IETF in 2010 to launch a much larger effort to revise the
   basic URN RFCs as a part of project PersID (
   PersID is developing tools for establishing an European network of
   URN resolvers concentrating on bibliographic identifiers.  The aim in
   the IETF is to bring these RFCs in alignment with the current URI
   Standard (STD 63, RFC 3986), ABNF, and IANA guidelines.  The
   discussion in PersID has contributed significantly to this work.

   Your name could go here ...

9.  References

9.1.  Normative References

   [ISO1]      ISO, "Information and documentation - The International
               Standard Book Number (ISBN)", ISO 2108-1992, 1992.

   [ISO2]      ISO, "Information and documentation - The International
               Standard Book Number (ISBN)", ISO 2108-2005, 2005.

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2141]   Moats, R., "URN Syntax", RFC 2141, May 1997.

   [RFC3406]   Daigle, L., van Gulik, D., Iannella, R., and P.
               Faltstrom, "Uniform Resource Names (URN) Namespace
               Definition Mechanisms", BCP 66, RFC 3406, October 2002.

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9.2.  Informative References

   [DOIHOME]   International DOI Foundation, "The Digital Object
               Identifier System", <>.

   [IANA-URI]  IANA, "URI Schemes Registry",

   [IANA-URN]  IANA, "URN Namespace Registry",

   [OCLC-WC]   OCLC WorldCat, " The World's Largest Library
               Catalog", <>.

   [PREFIX]    International ISBN Agency, "ISBN Prefix Ranges",

   [RFC2288]   Lynch, C., Preston, C., and R. Jr, "Using Existing
               Bibliographic Identifiers as Uniform Resource Names",
               RFC 2288, February 1998.

   [RFC2611]   Daigle, L., van Gulik, D., Iannella, R., and P.
               Faltstrom, "URN Namespace Definition Mechanisms", BCP 33,
               RFC 2611, June 1999.

   [RFC3044]   Rozenfeld, S., "Using The ISSN (International Serial
               Standard Number) as URN (Uniform Resource Names) within
               an ISSN-URN Namespace", RFC 3044, January 2001.

   [RFC3187]   Hakala, J. and H. Walravens, "Using International
               Standard Book Numbers as Uniform Resource Names",
               RFC 3187, October 2001.

   [RFC3986]   Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
               Resource Identifier (URI): Generic Syntax", STD 66,
               RFC 3986, January 2005.

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Authors' Addresses

   Maarit Huttunen
   The National Library of Finland
   P.O. Box 26
   Helsinki, Helsinki University  FIN-00014


   Juha Hakala
   The National Library of Finland
   P.O. Box 15
   Helsinki, Helsinki University  FIN-00014


   Alfred Hoenes (editor)
   Gerlinger Str. 12
   Ditzingen  D-71254


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