IETF URNbis WG                                                 J. Hakala
Internet-Draft                           The National Library of Finland
Obsoletes: 3188 (if approved)                             A. Hoenes, Ed.
Intended status: Standards Track                                  TR-Sys
Expires: April 28, 2012                                 October 26, 2011

     Using National Bibliography Numbers as Uniform Resource Names


   National Bibliography Numbers, NBNs, are widely used by the national
   libraries and other organizations in order to identify various
   resources such as digitized monographs and monographs pre-dating the
   emergence of the ISBN system.  Generally, NBNs may be applied to all
   kinds of resources that do not have an established (standard)
   identifier system of their own.

   A URN (Uniform Resource Names) namespace for NBNs was established in
   2001, and since then, tens of millions of unique URN:NBNs have been
   assigned.  The namespace registration was performed in RFC 3188 and
   applied to the NBNs in use at that point.  No URN:NBN resolution
   services existed at the time when that RFC was written.  Since then,
   national libraries in several countries including Finland, Germany,
   Italy, and the Netherlands have established these services.

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


   Comments are welcome and should be directed to the
   mailing list or the authors.

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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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 28, 2012.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions used in this document  . . . . . . . . . . . . . .  5
   3.  Fundamental Namespace and Community Considerations for NBN . .  6
     3.1.  The URN:NBN Namespace  . . . . . . . . . . . . . . . . . .  6
     3.2.  Community Considerations for NBNs  . . . . . . . . . . . .  6
   4.  National Bibliography Numbers (NBNs) . . . . . . . . . . . . .  8
     4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.2.  Encoding Considerations and Lexical Equivalence  . . . . .  9
     4.3.  Resolution and Persistence of NBN-based URNs . . . . . . . 11
     4.4.  Additional Considerations  . . . . . . . . . . . . . . . . 13
     4.5.  URN Namespace ID Registration for the National
           Bibliography Number (NBN)  . . . . . . . . . . . . . . . . 13
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 18
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 19
   Appendix A.  Draft Change Log  . . . . . . . . . . . . . . . . . . 20
     A.1.  draft-hakala-rfc3188bis-nbn-urn-00 to
           draft-ietf-urnbis-*-00 . . . . . . . . . . . . . . . . . . 20
     A.2.  draft-ietf-urnbis-rfc3188bis-nbn-urn-00 to -01 . . . . . . 20

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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 originally defined in
   RFC 2141 [RFC2141] and now being formally specified in RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn].  Any identifier, when used within
   the URN system, needs to have a namespace of its own.  As of October
   2011, IANA had registered 44 formal URN namespaces (see [IANA-URN]),
   one of which belongs to NBN, National Bibliography Number, as
   specified 2001 in RFC 3188 [RFC3188].

   URN:NBNs are in production use in several European countries
   including (in alphabetical order) Austria, Finland, Germany, Italy,
   the Netherlands, Norway, Sweden, and Switzerland; several other
   countries in Europe and elsewhere are considering usage of them.  The
   URN:NBN namespace is managed by the national libraries.  URN:NBNs
   have been applied to diverse content including Web archives,
   digitized materials, research data, and doctoral dissertations.

   As a part of the initial development of the URN system back in the
   late 1990s, the IETF URN working group agreed that it was important
   to demonstrate that the URN syntax can accommodate existing
   identifier systems.

   The bibibliographic community (including, e.g., publishers and
   libraries) is dependent on the use of identifiers.  Bibliographic
   identifiers function as persistent names for books, serials, articles
   etc. that exist in print and, increasingly, in various electronic
   formats.  There are also standard identifiers for works -- immaterial
   entities which only become "real" via manifestations such as printed
   or electronic books.

   RFC 2288 [RFC2288] investigated the feasibility of using three
   identifiers (ISBN, ISSN and SICI, see below) as URNs, with positive
   results; however, it did not 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].  That RFC, in
   turn, is now being updated as well into RFC 3406bis

   URN Namespaces have subsequently been registered for NBN (National
   Bibliography Number), ISBN (International Standard Book Number), and
   ISSN (International Serial Standard Number) in RFCs 3188 [RFC3188],
   3187 [RFC3187], and 3044 [RFC3044], respectively.  The ISBN namespace
   registration is being revised so that it will cover both ISBN-10 and
   ISBN-13; [I-D.ietf-urnbis-rfc3187bis-isbn-urn].  The current ISSN
   registration still does not cover ISSN-L, defined in the new version

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   of ISSN; there is work in progress in the URNbis WG to update the
   existing namespace registration, RFC 3044 [RFC3044].

   NBN differs from the other bibliographic identifier systems listed
   above because it is not a single identifier system with standard-
   specified syntax.  There is not and there will never be a standard
   describing all the NBN systems in use, although each NBN implementer
   MUST keep track on how the identifier is used.  The term "National
   Bibliography Number" encompasses unique and persistent local
   identifier systems that the national libraries and their partner
   organizations use in addition to the more formally (and
   internationally) established identifiers.

   Historically, NBNs were only applied in the national bibliographies
   to identify the resources catalogued into it.  Prior to the emergence
   of bibliographic standard identifiers, every publication got an NBN;
   after, e.g., the ISBN system was established, NBNs were given only to
   those books that did not have an ISBN -- whether due to human error
   or because they did not qualify.

   During the last 10 years, the NBN scope has been extended to cover a
   vast range of digital resources available via the Internet.  Only a
   small subset of these resources are catalogued in the national
   bibliographies or other bibliographical databases.  Digitized books
   are an example of this group; the ISBN manual does not allow ISBN
   assigment to them, even if the original printed book had had an ISBN.
   Objects harvested into Web archives are an example of resources that
   will not be catalogued but which may nevertheless receive an NBN.

   For now, NBNs have been used to identify manifestations of resources.
   However, they may be used to identify (immaterial) works as well, if
   the local NBN assignment practices allow that.  In such a case, URN
   resolution SHOULD supply, for instance, descriptive metadata of the
   work itself, and/or links to the manifestations of the work.

   Simple guidelines for using NBNs as URNs and the original namespace
   registration were published in RFC 3188 [RFC3188].  The RFC at hand
   replaces RFC 3188; sections discussing the methods in which URN:NBNs
   should be resolved have been updated and the text is compliant with
   the stipulations of RFC 3406bis
   [I-D.ietf-urnbis-rfc3406bis-urn-ns-reg], the successor of RFC 3406
   [RFC3406], which previously had replaced RFC 2611 [RFC2611] (the
   latter was applied in the initial registration).

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",

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   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.  Fundamental Namespace and Community Considerations for NBN

3.1.  The URN:NBN Namespace

   NBNs are widely used to identify hand-held or digital objects covered
   by legal requirements on national libraries and similar institutions
   to preserve the cultural heritage of their constituents.  All objects
   in deposit collections will be preserved for long term.  While the
   methods for digital preservation may vary, the favourite one is
   migration.  As a rule, the old versions are not removed, in order to
   alleviate the effects of failed migrations.  This means that
   eventually there will be multiple manifestations of every digital
   object.  Each manifestation MUST have its own NBN.  All
   manifestations of an object SHOULD be interlinked, for example via
   providing links in the descriptive metadata.

   NBNs SHOULD only be used for objects when the standard identifiers
   such as ISBN are not applicable.  However, they MAY be used for
   component parts (fragments) even when the identified resources as a
   whole qualify for standard identifiers.  For instance, even if an
   e-book has an ISBN, a chapter or image within the book MAY receive an
   NBN if it is available separately.

   Standard identifier systems (such as ISBN and ISSN) have a limited
   scope; they are applicable only to certain kinds of objects.  The
   role of the NBN is to fill in the gaps; collectively, the standard
   bibliographic identifiers and NBNs cover -- at least in theory -- all
   resources the national libraries and their partners need to preserve
   for long term.

   Section 4 below, and there in particular Section 4.1, presents a more
   detailed overview of the structure of the NBN namespace, related
   institutions, and the identifier assignment principles used.

3.2.  Community Considerations for NBNs

   National libraries are the key organizations providing persistent URN
   resolution services for objects identified with NBNs, independent of
   their form.  National libraries MAY allow other organizations such as
   university libraries or governmental organizations to assign NBNs to
   the resources they preserve for long term.  In such case, the
   national library MUST co-ordinate the use of NBNs at the national

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   level.  The national library MAY also provide URN resolution services
   and other technical services to other NBN users.  These other
   organizations MUST either establish their own resolution services or
   use the technical infrastructure provided by the national library.

   Bibliographic objects often have a logical structure.  For instance,
   books can be divided into component parts such as articles, chapters,
   short stories / novellas, images, and so on.  Depending on, e.g., the
   technical infrastructure, it may be possible to access these
   component parts directly, necessitating identification.  NBNs MAY be
   assigned to these component parts, depending the local NBN assignment

   The NBN namespace does not specify a generic, intrinsic syntax for
   fragment identification, since all candidate characters such as colon
   or full stop MAY already be in other use.  In practice, there are at
   least three different ways in which component parts can be identified
   and used within the NBN namespace.

   The simplest approach is to assign a separate NBN for each component
   part.  In these cases, the resolution process SHOULD link the URN:NBN
   to a URI belonging to an object such as a text file containing a
   chapter of a book.

   Second, a local fragment syntax MAY be used, independently of the
   requirements of RFC 3986.  Fragment identifiers will only be
   recognized as such in the application responding to the request.  It
   MUST be able to process the URN:NBN correctly; the result MUST be the
   identified logical component of the entire resource, or a surrogate
   such as descriptive metadata about the component.

   Finally, if the stipulations of the URI standard (RFC 3986
   [RFC3986]), the URI Syntax (RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn]), and those of the Internet media
   type as specified in RFC 2046 [RFC2046] are met, URI fragments MAY be
   applied in the NBN string.  In such cases the resolution process
   SHALL retrieve the entire document, and the fragment selection is
   then applied to it.  This will take the user to, e.g., the beginning
   of a relevant journal article within an XML file containing the
   entire issue.

   The objects identified by NBNs do not need to be available in the
   Internet.  If so, the URN:NBN resolver SHOULD supply descriptive
   metadata about the resource, possibly including information about
   where its physical manifestations are stored in the owning
   institutions' holdings.  A resolver MAY also deliver a digital
   surrogate, if one exists, or information about other versions of the

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   If an NBN identifies a work, descriptive metadata SHOULD be supplied.
   These metadata records MAY include links to the physical
   manifestations of the work.  Metadata records describing these
   manifestations MAY include links to each other and to the work level
   metadata record.

   Section 4 below, and in particular Section 4.3 therein, presents a
   detailed overview of the application of the URN:NBN namespace as well
   as the principles of, and systems used for, the resolution of NBN-
   based URNs.

4.  National Bibliography Numbers (NBNs)

4.1.  Overview

   National Bibliography Number (NBN) is a generic name referring to a
   group of identifier systems administered by the national libraries
   and institutions authorized by them.  The NBN assignment is typically
   performed by the organization hosting the resource.  These
   organizations (national libraries and institutions in liaison with
   them) are usually committed to preserving their deposit collections
   for a long time -- at least decades, and possibly centuries.
   Resources belonging to these collections SHOULD receive NBNs only if
   no standard identifier is applicable.

   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 the national
   level.  When used as URNs, NBN strings MUST be augmented with a
   controlled prefix such as the ISO 3166-1 alpha-2 two-letter country
   code.  These prefixes guarantee uniqueness of the NBN-based URNs at
   the global scale [Iso3166MA].

   NBNs have traditionally been assigned to objects that do not have (or
   cannot have) a formal (standard) identifier, but are catalogued to
   the national bibliography.  Examples of this include books that
   predate the introduction of the ISBN standard in the 1970s, modern
   books that for some reason have not received an ISBN, and all
   digitized books.

   In principle, NBNs enable identification of any kind of resource and
   their component parts, such as periodical articles and still images
   within them, or short stories and poems published in book form or in
   the Web. The national libraries often specify national assignment
   policies; such policy may limit the NBN usage to resources stored
   permanently in the national library's legal deposit collection.
   However, the scope of the NBN assignment can be significantly
   broader; for instance, NBNs are already used to identify research

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   datasets (which are not part of legal deposit in any country yet).

   Some national libraries (e.g., Finland, Norway, Sweden) have
   established Web-based URN generators, which enable authors and
   publishers to retrieve NBN-based URNs.  There are also applications,
   used for instance in digitization processes, that assign NBNs
   automatically to resources or even their component parts such as
   still images published in monographs or serials.

   Within the limits set by the URI Generic Syntax (RFC 3986 [RFC3986])
   and the URN Syntax (RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn]),
   each national library using URN:NBNs SHOULD specify the scope of the
   system.  Such scope document SHOULD clarify the local policy
   concerning fragment identification and the local fragment syntax used
   (if any).  The policy MAY specify the maximum length of the NSS and
   other relevant syntactical features in order to simplify NSS parsing.

4.2.  Encoding Considerations and Lexical Equivalence

   Expressing NBNs as URIs is usually straightforward, as traditionally
   only ASCII characters have been used in NBN strings.  If necessary,
   NBNs must be translated into canonical form as specified in
   RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn].

      [[ Editorial Note: The text below is scheduled for revision in the
      next draft version in order to better align it with the ABNF in
      Section 4.5. ]]

   When an NBN is used as a URN, the namespace-specific string (NSS)
   MUST consist of three parts:

   o  a prefix, consisting of either a two-letter ISO 3166-1 country
      code or another registered string,

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

   o  the NBN string.

   The prefix, consisting of either the ISO 3166-1 country code or other
   registered prefix string, is case-insensitive.  The NBN string MAY be
   case sensitive, depending on the NBN syntax applied locally.  Future
   NBN implementations SHOULD make the NBN string case insensitive as

   Different delimiting characters are not semantically equivalent.

   Use of colon as the delimiting character is allowed if and only if a
   country code-based NBN namespace is split further into smaller sub-

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   namespaces.  These sub-divisions are part of the prefix.  A colon
   MUST NOT be used for any other purpose, or in the another registered

   A hyphen MUST be used for separating the prefix and the NBN string,
   or the part of the NBN string that is assigned to the identified
   object by a sub-division authority.  A registered prefix string MUST
   NOT contain any hyphens, since they would make parsing of URN:NBNs
   impossible.  The first hyphen SHALL indicate the end of the prefix.
   "indicates" ??  Since the NBN string itself can contain hyphens,
   parsing cannot be based on the last hyphen being the delimiting

   If there are several national libraries in one country, these
   libraries MUST agree on how to divide the national namespace between
   themselves using this method before the URN:NBN assignment begins in
   any of these libraries.

   A national library MAY also assign to trusted organization(s) such as
   a university or a government institution its own NBN sub-namespace.
   The sub-namespace MAY be further divided by the partner organization
   (or by the national library on request of the partner).

   Sub-namespace identifier strings are case-insensitive.  They MUST NOT
   contain any hyphens.

   Non-ISO 3166-1 alpha-2 prefixes, if used, MUST be registered on the
   global level.  The U.S. Library of Congress maintains the central
   register of assigned non-ISO 3166-1 prefix strings together with the
   name and contact information of the registrant.  Each prefix MUST
   have one and only one user organization, which is responsible for
   maintaining the delegated sub-namespace according to the general
   rules set out in this document.

      Since the setup of that registry, and up to the time of this
      writing, no such prefixes have been registered, and it is expected
      that demand will remain low.  Therefore, no more complicated rules
      (for instance for a hierarchical structure of such prefixes), are
      specified here.  For this unlikely case of unexpected future
      needs, a revision of this document would be needed to accommodate

      [[ Note: If the NBN community does not see a need to maintain this
      -- so far unused -- option for prefixes not based on ISO 3166-1,
      it could be dropped without breaking backwards compatibility.
      Another option to consider would be migrating the registry to IANA
      if that would be preferred by the Library of Congress. ]]

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   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 of these codes SHOULD be
   made available online.

   All two-letter prefixes are reserved for existing and possible future
   ISO country codes (or for private use) [Iso3166MA] and MUST NOT be
   used as non-ISO country-code prefixes.

   Models (indicated linebreak inserted for readability):

      URN:NBN:<ISO 3166 alpha-2 country code>-<assigned NBN string>

      URN:NBN:<ISO 3166 alpha-2 country code>:<sub-namespace code>-\
          <assigned NBN string>

      URN:NBN:<non-ISO 3166 prefix>-<assigned NBN string>

   Examples (using actually assigned NBNs):





   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
   (URL) has to be maintained.  If bibliographic records in libraries'
   on-line public access catalogues (OPACs) contain URLs, then each
   record must be modified whenever the URL changes.  This could mean
   hundreds of changes for a popular resource.  With URNs, only the URN
   - URL linking in the mapping table of the resolution servicem needs
   to be kept up-to-date.  All links in the bibliographic records point
   to the resolution service where the URN is translated to one or more
   valid URL(s).

4.3.  Resolution and Persistence of NBN-based URNs

   Eventually, URN:NBNs will be resolved with the help of a resolver
   discovery service (RDS).  No such system has been installed yet in
   the Internet infrastructure.  Therefore, URN:NBNs MAY be 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

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   resolver is <>.  Thus the HTTP URI for the Finnish URN
   in the example above is <>.
   This public persistent identifier will not change.  In contrast,
   since the resource has already moved once from one DSpace system to
   another, its DSpace-internal Handle has changed (to  Since Handles are in
   this case only internal identifiers, they do not need to persist, and
   users are asked to rely on the URN-based HTTP URI when they make
   persistent links to the document.

   The country code-based prefix part of the URN namespace-specific
   string will provide a hint needed to find the correct national
   resolution service for URN:NBNs from the resolver discovery service
   when it is established.

   There are three inter-related aspects of persistence that need to be
   discussed: persistence of the objects itself, persistence of the
   identifier and persistence of the URN resolvers.

   NBNs have traditionally been assigned to printed resources, which
   tend to be persistent.  Many books published in the 15th century are
   still perfectly readable.  In contrast, digital resources require
   frequent migrations to guarantee accessibility.  Although it is
   impossible to estimate how often migrations are needed, hardware and
   software upgrades take place frequently, and even a life time of
   10-20 years can be considered as long.

   Migration is often a lossy process, so different manifestations of an
   object may have different look and feel, and possibly even
   intellectual content.  Because of this, each manifestation must have
   a different identifier.  Any intellectual work will eventually be
   represented by a set of manifestations in which each successive
   version is likely to be more and more distant from the original
   object.  It is not possible to know which one of these versions will
   fit the needs of a user best; therefore it is necessary to interlink
   URNs belonging to the different manifestations of an object (possibly
   via a work level metadata record) so as to make the users aware of
   all the existing manifestations of the object and to enable them to
   retrieve the one that matches their interests best.

   Thus, even if manifestations of digital objects are not and will not
   be persistent per se, persistent identifiers such as URN:NBNs SHOULD
   support construction of an information architecture thath enables
   persistent access to the identified intellectual content, although
   the look and feel of their manifestations will inevitably change over

   Persistence of URN resolvers themselves is mainly an organizational

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   issue, related to the persistence of organizations maintaining them.
   As URN:NBN resolution services will be supplied (primarily) by the
   national libraries to enable access to their (legal) deposit
   collections, these services SHOULD be persistent.

4.4.  Additional Considerations


4.5.  URN Namespace ID Registration for the National Bibliography Number

   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. ]]

   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 demo
      systems in 1998; since then, tens of millions of URN:NBNs have
      been assigned.  The number of users of the namespace has grown in
      two ways: new national libraries have started using NBNs, and some
      national libraries using the system have formed new liaisons.

   Registration Information:

      Version: 4
      Date: 2011-10-25

   Declared registrant of the namespace:

      Name: Mr. Juha Hakala
      Affiliation: Senior Adviser, The National Library of Finland
      Postal: P.O.Box 15, 00014 Helsinki University, Finland
      Web URL:

      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 is available for free for the national libraries and the
      organizations co-operating with them.  The national libraries may
      allow these organizations to use the namespace for free or for a

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      fee; such fees, if collected, may be based on, e.g., the
      maintenance costs of the system.

   Declaration of syntactic structure of NSS part:

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

         a prefix, consisting of either an ISO 3166-1 alpha-2 country
         code and optional sub-namespace code(s) separated by colon(s)
         or other registered string (which must not contain the
         delimiting characters colon (:) and hyphen (-)),

         a hyphen (-) as the delimiting character, and

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

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

       nbn_nss     = prefix "-" nbn_string

       prefix      = cc_prefix / reg_prefix
                     ; these prefixes are case-insensitive

       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*(ALPHA / DIGIT)
                     ; as assigned by the respective national library

       reg_prefix  = 3*(ALPHA / DIGIT)
                     ; as assigned by the Library of Congress --
                     ; identifies a trusted third party
                     ; to which the branch is delegated

       nbn_string  = <specific per prefix>
                     ; MUST adhere to RFC 3986 <path-rootless> syntax;
                     ; parsers must regard nbn_strings as case-sensitive

      Colon MAY be used as a delimiting character only within the
      prefix, between ISO 3166-1 country code and sub-namespace code(s),
      which split the national namespace into smaller parts.

      Dividing non-ISO 3166-based namespaces further with sub-namespace

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      codes MUST NOT be done.

      Whereas all prefixes are regarded as case-insensitive, NBN-strings
      MAY be case-sensitive at the preference of the assigning
      authority; parsers therefore MUST treat these as case-sensitive;
      any case mapping needed to introduce case-insensitivity MUST be
      implemented in the responsible resolution system.

      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 identifier 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, has beeen created and made available via the Web.
      Contact information: <>.

      All two-letter codes are reserved by the ISO 3166 Maintenance
      Agency for either existing and possible future ISO country codes
      (or for private use) and MUST NOT be used as non-ISO prefixes.

      Sub-namespace codes MUST be registered on the national level by
      the national library that assigned the code.  The list of such
      codes SHOULD be available via the Web.

      See chapter 4.2 for examples.

   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 objects (and their component parts) that lack a
      'canonical' identifier.  NBN can also be used to identify works.
      Each national library uses its own NBN system independently of
      other national libraries; there is neither a general standard
      defining the NBN syntax nor a global authority to control the use
      of these identifier systems.

      Each national library decides locally its NBN assignment policy.
      These identifiers have traditionally been assigned to documents
      that cannot have a standard identifier, but are nevertheless
      catalogued to the national bibliography.  Due to the extension of
      the scope of the (legal) deposit actitivies to Internet resources,
      NBN assignment has been extended to, e.g., harvested Web pages.

      The syntax of NBNs is specified by each national library
      independently.  Historically, NBNs used in national bibliographies

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      contained only characters that belong to the US-ASCII 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 RFC 2141bis

   Conformance with URN syntax:

      [[ Editorial Note: Need to discuss new specification requirements
      from the RFC 2141bis draft! ]]

   Rules for lexical equivalence of NSS part:

      Prefix, consisting of either ISO 3166-1 country code and its
      (optional) sub-divisions, or other registered string, is case-
      insensitive.  NBN string MAY be case-sensitive; the recommendation
      is that new NBN implementations should be case-insensitive.
      Requirements expressed in RFC 2141bis
      [I-D.ietf-urnbis-rfc2141bis-urn] must be taken into account as

      Formally, two URN:NBNs are lexically equivalent if they are octet-
      by-octet equal after the following (conceptional) preprocessing:
      1. normalize the case of the leading "urn:" token;
      2. normalize the case of the prefix (country code and its optional
      sub-divisions or other registered string);
      3. normalize the case of any percent-encoding;
      4. ignore <query> parameters (if included).

      Note: The case used in the normalization steps is a local matter;
      implementations can normalize to lower or upper case as they see
      fit, they only need to do it consistently.

   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, MUST be
      persistent.  Persistence of the resources themselves will be
      guaranteed by the national libraries as a part of their legal
      deposit activities.

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

      Users of the NBN namespace MAY utilise different policies for

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      guaranteeing uniqueness of NBNs.  The identifiers can be assigned
      sequentially by programs (URN generators) in order to avoid human
      mistakes.  It is also possible to use printable representations of
      checksums such as SHA-1 [RFC6234] or MD5 [RFC1321] as NBN, as long
      as the registration process prevents collisions (irrespective of
      the minuscule probability for these to occur).

   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 MAY be differences in scope.  The
      common denominator, however, is that the identified resources
      themselves are persistent.

      National libraries have applied different strategies in assigning
      NBN-based URNs, and different approaches have varying levels of
      control with respect to the persistence of the documents.  Manual
      URN assignment by the library personnel provides the best possible
      control, especially if this is done only when the document is
      catalogued into the national bibliography.  In most libraries the
      scope of URN:NBN is much broader than this.  From a control point
      of view, the most liberal approach is a URN generator that builds
      URNs for anonymous users, 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
      assignment.  Usage rules may of course vary within one country,
      from one sub-namespace to the next.  As of yet there are no
      international guidelines for NBN use beyond what has been
      stipulated above, but more stringent rules may be developed in the

   Process for identifier resolution:

      See Section 4.3 of RFC XXXX.

   Validation mechanism:

      None specified on the global level (beyond a routine check of
      those characters that require special encoding when employed in
      URIs).  NBNs may have a well specified and rich syntax (including,
      e.g., fixed length and checksum).  In such case, it is possible to
      validate the correctness of the NBN programmatically.


      NBN are applied to resources held in the collections of national
      libraries and their partner organizations.  NBNs may also be used

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      to identify works that these resources manifest.

5.  Security Considerations

   This document proposes means of encoding NBNs within the URN
   framework.  A URN resolution service for NBN-based URNs is depicted,
   but only at a generic level; thus, questions of secure or
   authenticated resolution mechanisms and authentication of users are
   out of scope of this document.  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 resolution services.

6.  IANA Considerations

   IANA is asked to update the existing registration of the Formal URN
   Namespace 'NBN' using the template given above in Section 4.5.

7.  Acknowledgements

   Revision of RFC 3188 started during the project PersID
   (<>).  Later the revision was included in the
   charter of the URNbis working group in the Applications Area.  The
   author wishes to thank his colleagues in the PersID project and the
   URNbis participants for their support.

   Tommi Jauhiainen has provided feedback on an early version of this

   Your name could go here ...

8.  References

8.1.  Normative References

              Hoenes, A., "Uniform Resource Name (URN) Syntax",
              draft-ietf-urnbis-rfc2141bis-urn-00 (work in progress),
              November 2010.

              Hoenes, A., "Uniform Resource Name (URN) Namespace
              Definition Mechanisms",
              draft-ietf-urnbis-rfc3406bis-urn-ns-reg-00 (work in
              progress), December 2010.

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

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

8.2.  Informative References

              Huttunen, M., Hakala, J., and A. Hoenes, "Using
              International Standard Book Numbers as Uniform Resource
              Names", draft-ietf-urnbis-rfc3187bis-isbn-urn-01 (work in
              progress), October 2011.

              IANA, "URI Schemes Registry",

              IANA, "URN Namespace Registry",

              ISO, "ISO Maintenance agency for ISO 3166 country codes",

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

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              November 1996.

   [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.

   [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

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              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.

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

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

   [RFC6234]  Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011.

Appendix A.  Draft Change Log

   [[ RFC-Editor: Whole section to be deleted before RFC publication. ]]

A.1.  draft-hakala-rfc3188bis-nbn-urn-00 to draft-ietf-urnbis-*-00

   - formal updates for a WG draft; no more "Updates: 2288";
   - introduced references to other URNbis WG documents;
   - changes based on review by Tommi Jauhiainen;
   - Sect. 3 restructured into namespace and community considerations;
   - old Sect. 7 incorporated in new Sect. 3.1;
   - Security Considerations: old Section 4.5 merged into Section 5;
   - added guidelines for when two manifestations of the same work
   should get different URN:NBNs;
   - clarified role of ISO 3166/MA for ISO 3166-1 country codes;
   - clarified role of non-ISO prefix registry maintaind by the LoC;
   - resolved inconsistency in lexical equivalence rules: as already
   specified for ISO alpha-2 country-codes, and in accordance with
   established practice, the whole NBN prefix is now declared case-
   - registration template adapted to rfc3406bis [-00];
   - numerous editorial fixes and enhancements.

A.2.  draft-ietf-urnbis-rfc3188bis-nbn-urn-00 to -01

   - Numerous changes to accommodate the outcome of the discussions on
   the urn list;
   - three different ways of identifying fragments specified;
   - removed some redundant/irrelevant paragraphs/subsections;
   - the "one manifestation, one URN" principle strenghtened;

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   - introduced the idea of interlinking manifestations;
   - extended the scope of the NBN explicitly to works;
   - added reference to S4.2 in namespace registration;
   - numerous editorial fixes and enhancements.

Authors' Addresses

   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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