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Versions: (RFC 3188) 00 draft-ietf-urnbis-rfc3188bis-nbn-urn

IETF                                                           J. Hakala
Internet-Draft                           The National Library of Finland
Obsoletes: 3188 (if approved)                             A. Hoenes, Ed.
Updates: 2288 (if approved)                                       TR-Sys
Intended status: Standards Track                            May 19, 2010
Expires: November 20, 2010


     Using National Bibliography Numbers as Uniform Resource Names
                  draft-hakala-rfc3188bis-nbn-urn-00

Abstract

   National Bibliography Numbers, NBNs, are widely used by the national
   libraries and other organizations in order to identify various
   resources such as monographs pre-dating the emergence of the ISBN
   system or still images.  As a rule, NBNs are applied to all kinds of
   resources that do not have an established identifier system of their
   own.

   Since 2001, there has been a URN (Uniform Resource Names) namespace
   for NBNs, and during 2001-2009 millions of URN-based unique and
   persistent NBNs have been assigned.  The namespace registration was
   performed in RFC 3188 and applied to the NBNs known at that point.
   No URN:NBN resolution services existed at the time when the RFC was
   written.  Since then several countries have started using URN:NBNs to
   identify electronic resources and to provide persistent links to
   them.  To this end, many countries have established URN:NBN
   resolution services that supply URN - URL linking.

   This document replaces RFC 3188 and defines how NBNs can be supported
   within the URN framework.  An updated namespace registration (version
   4) is included.

Discussion

   This document is an outcome of work performed in 2009-2010 as a part
   of the project PersID (http://www.persid.org) revising 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
   identifiers.  This work is being brought to the IETF, and the intent
   is to establish a "URNbis" (or similar) working group in the
   Applications Area as soon as possible, which will then target this
   and related work.

   Comments are welcome on the urn@ietf.org or the urn-nid@ietf.org
   mailing list (or sent to the authors).  Interested parties are also
   invited to contribute to the WG formation process being discussed on
   the former list.


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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   it for publication as an RFC or to translate it into languages other
   than English.








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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions used in this document  . . . . . . . . . . . . . .  5
   3.  Identification and Resolution  . . . . . . . . . . . . . . . .  5
   4.  Namespace considerations: National Bibliography Numbers
       (NBNs) . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.2.  Encoding Considerations and Lexical Equivalence  . . . . .  7
     4.3.  Resolution of NBN-based URNs . . . . . . . . . . . . . . .  9
     4.4.  Additional Considerations  . . . . . . . . . . . . . . . . 10
     4.5.  Security Considerations  . . . . . . . . . . . . . . . . . 11
     4.6.  URN Namespace ID Registration for the National
           Bibliography Number (NBN)  . . . . . . . . . . . . . . . . 11
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   7.  Community Considerations . . . . . . . . . . . . . . . . . . . 17
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 18






























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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].  Currently, there is work in progress to revise that
   document [I-D.ah-rfc2141bis-urn].  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 NBN, National Bibliography Number, as specified 2001 in
   RFC 3188 [RFC3188].

   Currently URN:NBNs are in production use in several European
   countries including Finland, Germany, Italy, the Netherlands, Norway,
   and Sweden.  Several other countries in Europe and elsewhere are
   considering usage of them.  URN:NBNs have been applied in, e.g., Web
   archives, large collections of digitized materials, and collections
   of scientific articles.

   As part of the validation process for the development of URNs back in
   late 90s, the IETF URN working group agreed that it was 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 NBN, ISBN and
   ISSN in RFCs 3188 [RFC3188], 3187 [RFC3187], and 3044 [RFC3044].  The
   ISBN namespace registration is being revised so that it covers both
   ISBN-10 and ISBN-13; [I-D.hakala-rfc3187bis-isbn-urn]. the current
   ISSN registration still does not cover ISSN-L, defined in the new
   version of ISSN.  However, there is no registered namespace for SICI,
   and no plans to make such registration, due to the low popularity of
   the standard.

   Please note that NBN differs from the other identifiers listed here
   because there is no standard describing NBNs.  The term "National
   Bibliography Number" encompasses all identifier systems the national
   libraries use in addition to the more formally established
   identifiers.  Historically, they were only applied in the national
   bibliography to identify the resources catalogued into it.  During



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   the last 10 years NBN scope has been extended to a wide variety of
   digital resources available via the Internet.  Only a minority of
   these resources are catalogued in the national bibliography.  Some
   national libraries have also allowed other organizations to apply
   NBNs to their publications and other materials.

   Guidelines for using NBNs as URNs and the original namespace
   registration have been published in RFC 3188 [RFC3188].  The RFC at
   hand replaces RFC 3188 [RFC3188]; sections discussing the methods in
   which URN:NBNs can be resolved have been updated and the text is also
   compliant with the stipulations of RFC 3406 [RFC3406], which has
   replaced RFC 2611 [RFC2611] that was applied in the initial
   registration.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   NBN refers to any National Bibliography Number identifier system used
   by the national libraries and other institutions using the system
   with the national library's permission.

3.  Identification and Resolution

   As a rule, NBNs 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 NBN will often
   be digital, but they may also exist only in printed or other physical
   form.  In such a case, the URN:NBN resolver should nevertheless be
   able to supply e.g. bibliographic data about the resource, possibly
   including the address where the resource is available.

   National libraries are the key organizations providing persistent URN
   resolution services for resources identified with NBNs, independent
   of their form.  National libraries may however allow other
   organizations such as university libraries or governmental
   organizations to assign NBNs to their resources.  In such case the
   national library will co-ordinate the use of NBNs and support the NBN
   users in guaranteeing the persistence of these resources and
   resolution.  These other organizations may establish their own
   resolution services or they may use the infrastructure provided by
   the national library.







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4.  Namespace considerations: National Bibliography Numbers (NBNs)

4.1.  Overview

   National Bibliography Number (NBN) is a generic name referring to a
   group of identifier systems utilised by the national libraries and
   institutions authorized by them, such as universities.  The common
   denominator is that all these organizations are committed to preserve
   their collections for a long time; at least decades and possibly
   centuries.

   Each national library uses its own NBNs independently of other
   national libraries; there is no global authority that controls NBN
   usage.  For this reason, NBNs as such are unique only on a national
   level.  When used as URNs, NBN strings must be augmented with a
   controlled prefix such as the ISO 3166 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
   formal (standard) identifier, but are catalogued to the national
   bibliography.  Examples of this include books that predate the
   introduction of the ISBN in the 1970s, or modern books that for some
   reason have not received an ISBN.  NBNs can be seen as a fall-back
   mechanism: if no other, standards-based identifier such as an ISBN
   can be given, an NBN is assigned.

   URNs may also be used in universities' open repositories when a
   resource already has another identifier -- often a DOI (Digital
   Object Identifier) -- that can only be resolved in a publisher's (or
   third party's) resolution service, which cannot be used to provide
   linking to the open repository.  URN:NBN-based resolution can deliver
   that, and may also be extended to include access to other
   repositories holding the same resource.

   In principle, NBNs enable identification of any kind of resource,
   such as still images published in periodical articles, or short
   stories and poems published in book form or in the Web. Local
   policies may limit the NBN usage to for instance documents stored
   permanently in the national library's collections.  Following the
   initial registration of a URN namespace for NBN, several countries
   broadened the scope of NBN assignment significantly to cover broader
   scope of their digital materials.

   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 resources.
   There are also applications, used for instance in digitization
   processes, that assign NBNs automatically to resources or even their



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   component parts such as still images published in monographs or
   serials.

   Within the limitations set by RFC 2141, this document, and other
   relevant RFCs, both syntax and scope of local NBNs can be decided by
   each national library independently.  Historically, NBNs have
   consisted of one or more letters and/or digits.  For instance,
   (Finnish) NBN for the Romanian translation of the Finnish classic
   "Seven Brothers" published in 1957 is f568471.  URN strings can
   contain encoded UNICODE characters, as specified in the declaration
   of syntactic structure, and there are no length limitations.
   Therefore, literally billions of NBNs can be allocated, which makes
   them suitable for, e.g., naming of Web documents.

   In Italy a novel hierarchical distributed architecture for NBN
   assignment has been designed, in order to eliminate the single-point-
   of-error risks of a centralised system and to reduce the costs of
   managing a resolution service based on persistent identifiers.

   The Central National Library in Florence manages the national domain
   NBN:IT and the national URN resolution service that contains every
   URN:NBN assigned in Italy.  The library has supplied URN:NBN:IT sub-
   domains to trusted institutions and bodies such as universities that
   are responsible for digital collections and routinely manage digital
   resources, for instance via creating and updating metadata on these
   resources, including location (URL) information.  All these
   institutions have their own resolution services, but the URN - URL
   mappings in them are periodically harvested to the national
   resolution service using the Open Archives Initiative Protocol for
   Metadata Harvesting (OAI-PMH; see
   (<http://www.openarchives.org/OAI/openarchivesprotocol.html>).

   Harvesting the data to the central node enables distributed service.
   The central node can serve the users when the local node is not
   functional.  This architecture increases the robustness of the
   network via duplication of resolution services and enables peer-to-
   peer resolution between the second-level institutions.  Moreover, it
   is possible to add yet another layer to the network by creating an
   international node, which shall contain all the data from the
   national nodes.  Such international service may also be created by
   building a virtual union resolver that uses all the national nodes.
   The PersID project is investigating the feasibility of these
   technical solutions at the European level.

4.2.  Encoding Considerations and Lexical Equivalence

   Embedding NBNs within the URN framework initially did not present any
   particular encoding problems, since the ASCII characters utilized in



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   traditional NBN systems belonged to the URN character set.  Machine
   generated NBNs may be more demanding; if necessary, NBNs must be
   translated into canonical form as specified in
   [I-D.ah-rfc2141bis-urn].

   When an NBN is used as a URN, the namespace specific string must
   consist of three parts:

   o  a prefix, consisting of either a two-letter ISO 3166 country code
      or other registered string,

   o  a delimiting character that is either hyphen (-) or colon (:), and

   o  the NBN string.

   Delimiting characters are not lexically equivalent.

   A Hyphen MUST be used for separating the prefix and the NBN string.

   A Colon MAY be 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 divide the national namespace between themselves
   using this method.

   A national library may also assign to trusted organisation(s) such as
   a university or a government institution its own NBN sub-namespace.
   For instance, the national library of Finland has given Statistics
   Finland (<http://www.stat.fi/index_en.html>) a sub-namespace "st"
   (i.e., urn:nbn:fi:st).  These trusted organisations must follow the
   general rules of the NBN usage provided by the national library, and
   take care of the long-term preservation of the identified resources
   in order to guarantee persistence.

   Non-ISO 3166 prefixes, if used, MUST be registered on the global
   level.  The U.S. Library of Congress SHALL maintain the central
   register of reserved codes.

   Sub-namespace codes beneath a country-code-based namespace MUST be
   registered on the national level by the national library that
   assigned the code.  The national register SHOULD be made available on
   the Web.

   Two-letter codes MUST 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 that
   use the same prefix - for instance, a country code -, they need to
   agree on how to divide the namespace.  They may either share one



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   namespace but agree on how to avoid assigning duplicate identifiers,
   or they may split the namespace into two sub-namespaces.

   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-fe201003181510
      (NBN assigned to Tero Frestadius's Master's Thesis "In and Out":
      Segmentary Gang Politics in Los Angeles).

      urn:nbn:ch:bel-9039

      urn:nbn:se:uu:diva-3475

      urn:nbn:hu-3006

   From the libraries' point of view, one of the key benefits of using
   URNs and other persistent identifiers is that there is only one
   location - the resolution service - where the linking infomation has
   to be maintained.  If bibliographic records in library on-line public
   access catalogues (OPACs) contain URLs, then each record must be
   modified whenever the URL changes.  With URNs, it is only necessary
   to maintain the URN - URL linking in the mapping table of the
   resolution service.

4.3.  Resolution of NBN-based URNs

   URNs can be used to provide various services.  RFC 2483 [RFC2483]
   gives a few examples, such as retrieving a single URL or all URLs
   applying to the resource.  Services available may vary, depending on
   the technical implementation of the URN resolver and the target
   system contacted.  Please note that services must not be hard coded
   into the URN itself.

   Eventually, URNs will be resolved with the help of a resolver
   discovery service (RDS).  However, no such system is widely available
   yet.  Therefore, URNs are usually embedded in HTTP URIs in order to
   make them actionable in the present Internet.  In these HTTP URIs,
   the authority part must point to the appropriate URN resolution
   service.  In Finland, the address of the national URN resolver is



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   <http://urn.fi>.  Thus the HTTP URI for the URN in the example is
   <http://urn.fi/URN:NBN:fi-fe201003181510>.  This in turn resolves to
   the actual address of the thesis, which as of this writing
   (2010-03-27) was <https://oa.doria.fi/bitstream/handle/10024/59475/
   inandout.pdf?sequence=1>.

   The country code-based prefix part of the URN namespace specific
   string will provide a guide to finding the correct national
   resolution service for URN:NBNs from the resolver discovery service
   when it is established.  If there are multiple URN:NBN resolvers in
   the country, there are two possible approaches for making sure that
   RDS will work.  All URN:NBNs mappings can be harvested to the
   national node (the Italian approach).  The other approach is to make
   the RDS aware of all the URN:NBN resolution services, and specify
   which parts of the national URN:NBN namespace they are capable of
   serving.

   URN:NBN - URL mappings maintained nationally can be harvested using
   e.g.  OAI-PMH from abroad to other national and international URN
   resolvers.  This makes it possible to improve the reliability of the
   system; if the Finnish national resolver node does not respond, its
   URN - URL mappings may be available at other resolvers.

   Persistence of any resolution service is not only a technical issue,
   but also an organisational and legal one.  National libraries are in
   ideal position to provide persistent resolution services, since most
   of them maintain (legal) deposit collections, in which domestic
   publications shall be preserved for future generations.  Increasingly
   these collection contain also digital resources.

4.4.  Additional Considerations

   Guidelines adopted and promoted by each national library define when
   different manifestations 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, each
   manifestation of a resource will get a new NBN.  For instance, over
   time the national library may digitize the same photograph many times
   from different sources, but each copy will get its own NBN.  However,
   if a checksum such as MD5 (see RFC 1321 [RFC1321]) is used as NBN,
   the resources that are identical at bit level will receive the same
   NBN.  Dissimilar resources may get the same checksum; with a reliable
   message digest algorithm such probability is however very small.

   The rules governing the usage of NBNs are local and usually less
   strict than those specifying the usage of ISBNs and other standard
   identifiers.  As long as the NBNs were assigned only in the national
   libraries, the identifier use was however well co-ordinated in



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   practice.  Now, following significant broadening in the scope of the
   NBN to cover Web resources, NBN assignment is less tightly controlled
   even within one national library.  One resource -- for instance, a
   photo that has been published in many newspapers -- is likely to
   receive multiple NBNs.  If two national libraries are digitizing the
   same resources and use NBNs for identification of these resources,
   the result will be duplicate NBN assignment since NBNs as a rule have
   national scope.  If the metadata describing the resource is harvested
   into a common service, and the bibliographic records are similar
   enough to be merged, the user may see two NBNs and HTTP URIs pointing
   to two different resolution services and physical copies of the same
   resource.  If the two copies had the same identifier such as an ISBN,
   there would still be two HTTP URIs providing access to different
   physical copies of the resource.

   If the same resource -- for instance, a master's thesis published by
   two universities -- is held in two repositories located in different
   NBN-sub-namespaces within one national namespace, these copies may
   also receive different NBNs especially if there is no easy way of
   checking if the resource has already been identified somewhere.  In
   this case, duplication may be revealed in the national level when the
   metadata records of the two copies are compared.  In such case, like
   in the previous example, both URN:NBNs are equally valid.

4.5.  Security Considerations

   This document proposes means of encoding national bibliography
   numbers (NBNs) within the URN framework.  It discusses resolution
   only at a very generic level; thus, questions of secure or
   authenticated resolution services and authentication of users of such
   services are out of scope.  This document does not address means of
   validating the integrity or authenticating the source or provenance
   of URNs that contain NBNs.  Issues regarding intellectual property
   rights associated with objects identified by national bibliography
   numbers are also beyond the scope of this document, as are questions
   about rights to the bibliographic databases that may be used to
   construct resolution services.

4.6.  URN Namespace ID Registration for the National Bibliography Number
      (NBN)

   This registration describes how National Bibliography Numbers (NBNs)
   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:  NBN

      This Namespace ID was formally assigned to the National
      Bibliography Number in October 2001 when the namespace was
      registered officially.  Utilization of URN:NBNs started in
      demonstrator systems in 1998; production use has been going on for
      several years, and millions of URN:NBNs have been assigned.

   Registration Information:

      Version: 4
      Date: 2010-05-18

   Declared registrant of the namespace:

      Name: Mr. Juha Hakala
      Affiliation: Senior Adviser, The National Library of Finland
      Email: juha.hakala@helsinki.fi
      Postal: P.O.Box 15, 00014 Helsinki University, Finland
      Web URL: http://www.nationallibrary.fi/

      The National Library of Finland registered the namespace on behalf
      of the Conference of the European National Librarians (CENL) and
      Conference of Directors of National Libraries (CDNL), which have
      both made a commitment in 1998 to foster the use of URNs.  The NBN
      namespace will be available for free for all national libraries in
      the world.

   Declaration of syntactic structure:

      The namespace specific string (NSS) will consist of three parts:

         a prefix, consisting of either a two-letter ISO 3166 country
         code or other registered string and sub-namespace codes,

         delimiting characters (colon (:) and hyphen (-)), and

         an NBN string assigned by the national library or sub-delegated
         authority.

      Formal declaration of the NSS, using ABNF [RFC5234].










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         nbn_nss     = prefix "-" nbn_string

         prefix      = cc_prefix / reg_prefix

         cc_prefix   = iso_cc *( ":" subspc )

         iso_cc      = 2ALPHA
                       ; country code as assigned by ISO 3166, part 1 --
                       ; identifies the national library
                       ; to which the branch is delegated

         subspc      = 1*ALPHANUM
                       ; as assigned by the respective national library

         reg_prefix  = 3*ALPHANUM
                       ; as assigned by the Library of Congress --
                       ; identifies a trusted third party
                       ; to which the bracnh is delegated

         nbn_string  = <specific per prefix>
                       ;  must follow RFC 3986 <path-rootless> syntax

      Colon may be 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.

      Dividing non-ISO 3166-based namespaces further with sub-namespace
      codes MUST NOT be done.

      Hyphen MUST be used as the delimiting character between the prefix
      and the NBN string.  Within the NBN string, hyphen MAY 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, shall 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 MUST 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 list of such
      codes SHOULD be available via the Web.







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      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:

         urn:nbn:de:gbv:089-3321752945

   Relevant ancillary documentation:

      National Bibliography Number (NBN) is a generic name referring to
      a group of identifier systems used by the national libraries and
      other organizations for identification of deposited publications
      and other resources that lack a 'canonical' 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 neither a general standard
      defining NBN syntax nor a global authority to control the use of
      these identifier systems.

      Each national library decides locally which resources shall
      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.  With the introduction of the Internet and URN:
      NBN namespace in 1998, the scope of NBN assignment has been
      extended to a broad spectrum of Internet resources including,
      e.g., harvested Web pages.

      Some national libraries (Finland, Norway, Sweden) have established
      Web-based URN generators that enable authors and publishers to
      fetch NBN-based URNs for the resources they publish in the Web.
      The most significant group of publications to which NBNs have been
      applied are doctoral theses.

      The syntax of NBNs is decided by each national library
      independently.  Historically, NBNs used in national bibliographies
      contained only characters that belong to the URN character set.
      Following the expansion of NBN scope and semi- and fully automated
      NBN assignment processes, some NBNs may contain characters that
      must be translated into canonical form according to the
      specifications in [I-D.ah-rfc2141bis-urn].



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   Identifier uniqueness and persistence considerations:

      NBN strings assigned by two national libraries may be identical.
      In order to guarantee global uniqueness of NBN-based URNs,
      therefore a controlled prefix is present in the namespace specific
      string.  These NBNs, once given to the resource, will be
      persistent.  Persistence of the resources themselves will be
      guaranteed by the national libraries as a part of their legal
      deposit activities.  This applies to publications and Web
      resources only; long-term preservation of other resources such as
      governmental documents will be dependent on other actors like
      national archives.

      An NBN, once it has been assigned, must never be re-used for
      another resource.

      At the national level, libraries may utilise different policies
      for guaranteeing uniqueness of NBNs.  They may be assigned
      sequentially by programs (URN generators) in order to avoid human
      mistakes.  It is also possible to use checksums such as SHA-1 or
      MD5 as NBN.

   Process of identifier assignment:

      Assignment of NBN-based URNs MUST be controlled on national level
      by the national library / national libraries.  Although the basic
      principles are the same, there are differences in scope; for
      instance in the Netherlands URN:NBNs are used -- among other
      things -- to identify scientific articles stored in the national
      library's long term preservation system, whereas most other URN
      users are not applying them on scientific articles.  Finland, on
      the other hand, is using URNs extensively to identify and provide
      access to the digitized content.

      National libraries may choose different strategies in assigning
      NBN-based URNs, and different approaches have varying levels of
      control.  Manual URN assignment by the library personnel only
      provides the best possible control, especially if this is done
      traditionally, that is, only when the document is catalogued into
      the national bibliography.  Usually the scope of URN:NBN is much
      broader than this; NBNs may for instance be automatically
      generated for each archived resource by a long term preservation
      system.  From control point of view, the most liberal approach is
      a URN generator which builds URNs for everyone, with no guarantee
      that the resource identified will be preserved or accessible.
      Every national library must decide the degree of freedom it allows
      to the URN:NBN users.  Usage rules may of course vary from one
      sub-namespace to the next.  As of yet there are no international
      guidelines for NBN use, but they may be developed in the future.


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   Process for identifier resolution:

      See Section 4.3 of RFC XXXX.

   Rules for lexical equivalence:

      None in the global level, beyond those expressed in
      [I-D.ah-rfc2141bis-urn].

      National libraries may develop their own rules for the NBNs they
      use.

   Conformance with URN syntax:

      Traditional NBNs (those applied in the national bibliographies)
      consisted of ASCII 7-bit letters and digits (a-z and 0-9).  For
      instance, the NBN of the first Hungarian translation of the
      Finnish national epos Kalevala is f20043425.  The book was
      published in 1853 and therefore does not have an ISBN.  Machine-
      generated NBNs must follow the stipulations of
      [I-D.ah-rfc2141bis-urn].

   Validation mechanism:

      None specified on the global level (beyond a routine check of
      those characters that require special encoding when expressed as
      URIs).  A national library may use NBNs, which contain a checksum
      and can therefore be validated, but as of this writing there are
      no NBNs which incorporate a checksum.

   Scope:

      NBN is a global identifier system used for identification of
      diverse publications and other resources.  It is widely used and
      supported by the national libraries.

5.  Security Considerations

   This document proposes means of encoding NBNs within the URN
   framework.  An NBN-based URN resolution service is depicted, 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 NBNs.  Issues regarding intellectual property
   rights associated with objects identified by the NBNs are also beyond
   the scope of this document, as are questions about rights to the
   databases that might be used to construct resolvers.




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6.  IANA Considerations

   IANA is asked to update the existing registration of the Formal URN
   Namespace 'NBN' using the template given above in Section 4.6.

7.  Community Considerations

   National bibliography numbers enable the national libraries and
   organisations which liaise with them to uniquely identify resources
   and provide persistent links to the resource accessible in the
   Internet.  Since most digital documents held in national libraries'
   digital collections are not eligible for other, more formal
   identifiers such as ISBN, NBNs are a valuable asset for the
   community.  A proof of this are the millions of URN:NBNs that have
   been allocated since the NBN namespace was reserved, and the
   operational services that have been built, using these identifiers
   and resolver applications.

   For library users, URN-based identification and resolution services
   mean more efficient and reliable access to resources in general.  No
   special tools are needed for this; Web browsers are sufficient.  The
   users may also be able to acquire URN:NBNs to their own key resources
   such as university thesis.

8.  Acknowledgements

   The author wishes to thank his colleagues in the PersID project for
   their support.


9.  References

9.1.  Normative References

   [I-D.ah-rfc2141bis-urn]
              Hoenes, A., "Uniform Resource Name (URN) Syntax",
              draft-ah-rfc2141bis-urn-00 (work in progress), March 2010.

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

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.




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9.2.  Informative References

   [I-D.hakala-rfc3187bis-isbn-urn]
              Huttunen, M., Hakala, J., and A. Hoenes, "Using
              International Standard Book Numbers as Uniform Resource
              Names", draft-hakala-rfc3187bis-isbn-urn-00 (work in
              progress), March 2010.

   [IANA-URI]
              IANA, "URI Schemes Registry",
              <http://www.iana.org/assignments/uri-schemes/>.

   [IANA-URN]
              IANA, "URN Namespace Registry",
              <http://www.iana.org/assignments/urn-namespaces/>.

   [RFC1321]  Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
              April 1992.

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

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

   [RFC2483]  Mealling, M. and R. Daniel, "URI Resolution Services
              Necessary for URN Resolution", RFC 2483, January 1999.

   [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.

   [RFC3188]  Hakala, J., "Using National Bibliography Numbers as
              Uniform Resource Names", RFC 3188, 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

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

   Email: juha.hakala@helsinki.fi


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

   Email: ah@TR-Sys.de

































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