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: July 22, 2012                                  January 19, 2012

     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.  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 in RFC 3188.  Since then, several national libraries in several
   European countries have implemented URN:NBN-based systems.

   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.

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   This Internet-Draft will expire on July 22, 2012.

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Copyright Notice

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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   publication of this document.  Please review these documents
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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   Without obtaining an adequate license from the person(s) controlling
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   not be created outside the IETF Standards Process, except to format
   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.  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 . . . . . . . 10
     4.4.  Additional Considerations  . . . . . . . . . . . . . . . . 11
   5.  URN Namespace ID Registration for the National
       Bibliography Number (NBN)  . . . . . . . . . . . . . . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 17
   Appendix A.  Significant Changes from RFC 3188 . . . . . . . . . . 18
   Appendix B.  Draft Change Log  . . . . . . . . . . . . . . . . . . 19
     B.1.  draft-hakala-rfc3188bis-nbn-urn-00 to
           draft-ietf-urnbis-*-00 . . . . . . . . . . . . . . . . . . 19
     B.2.  draft-ietf-urnbis-rfc3188bis-nbn-urn-00 to -01 . . . . . . 19
     B.3.  draft-ietf-urnbis-rfc3188bis-nbn-urn-01 to -02 . . . . . . 19

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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 traditional identifier, when
   used within the URN system, needs to have a namespace of its own.  As
   of December 2011, IANA had registered 45 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.  They
   can be used by the national libraries and organizations co-operating
   with them.

   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.

   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
   of the ISSN standard; there also is work in progress in the URNbis WG
   to update the existing namespace registration, RFC 3044 [RFC3044].
   SICI-based URNs have not been specified to date, mainly due to the
   identifier system's limited popularity.

   The term "National Bibliography Number" encompasses persistent local

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   identifier systems that the national libraries and their partner
   organizations use in addition to the more formally (and
   internationally) established identifiers.  In practice, NBN differs
   from the standard identifier systems listed above because it is not a
   single identifier system with standard-specified scope and syntax.
   Each NBN implementer is obliged to keep track of how NBNs are being
   used, but within the generic framework set in this document, local
   NBN assignment policies may vary a lot.

   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 is catalogued in the national
   bibliographies or other bibliographic databases.  Web contents
   harvested into Web archives are an example of resources that will not
   be catalogued but may nevertheless receive an NBN.

   The NBN scope may be expanded further if necessary.  For instance,
   NBNs may be used to identify (immaterial) works or data elements, in
   order to facilitate linked data.  If the identified resource itself
   cannot be retrieved via resolution, URN resolution should supply a
   surrogate, such as descriptive metadata of the work itself, or
   description of the metadata element.

   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, unused features have been
   eliminated, 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",
   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.

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3.  Fundamental Namespace and Community Considerations for NBN

3.1.  The URN:NBN Namespace

   NBNs are widely used to identify hand-held or digital resources
   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.  The old versions will not be removed, in order to
   alleviate the effects of failed migrations.  Eventually there will be
   multiple manifestations of most digital resources.  Each
   manifestation SHOULD have its own NBN.  All manifestations of a
   resource SHOULD be interlinked, for example via providing persistent
   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, an image within the book MAY receive an NBN if
   the image is available separately.

   The scope of standard identifier systems such as ISBN and ISSN is
   limited; they are applicable only to certain kinds of resources.  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
   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.

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   NBNs may be used to identify fragments, but the NBN namespace does
   not specify a generic, intrinsic syntax for fragment identification.
   Any character that could be used to indicate a fragment such as colon
   or full stop may already be reserved.  However, 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 fragment
   identifiers 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.

   Resources identified by NBNs do not need to be available in the
   Internet.  When the resource itself is not accessible, the URN:NBN
   resolver SHOULD supply 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 object.

   If an NBN identifies an immaterial object such as work, descriptive
   metadata SHOULD be supplied.  These work level metadata records MAY
   include links to the physical manifestations of the work.  Metadata
   records describing these manifestations should include links to each
   other and to the work level metadata record.  If an NBN identifies a
   data element, description of the element SHOULD be supplied.

   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.

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4.  National Bibliography Numbers (NBNs)

4.1.  Overview

   National Bibliography Number (NBN) is a generic term 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, which is the particular nation's ISO 3166-1
   alpha-2 two-letter country code.  These prefixes guarantee uniqueness
   of the NBN-based URNs at the global scale [Iso3166MA].

   In principle, NBNs enable identification of any kind of resource and
   its component parts, such as a periodical and articles published in
   it.  A national library using URN;NBNs should specify a national
   assignment policy; such policy may limit the NBN usage to resources
   stored permanently in the national library's legal deposit
   collection.  But the scope of the NBN assignment can be significantly
   broader; for instance, NBNs are already used to identify research
   datasets (which are not part of legal deposit in any country yet).

   URN:NBN assignment may be automated.  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 generate NBNs automatically for the processed

   Each national library administering a URN:NBN sub-namespace SHOULD
   specify a local NBN assignment policy.  Such document SHOULD clarify
   e.g. the local policy concerning fragment identification and the
   local fragment syntax used (if any).  The policy MAY also clarify if
   works or data elements are included.  The policy MAY also specify the
   maximum length of the NSS and other relevant syntactical features in
   order to simplify NSS parsing.

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4.2.  Encoding Considerations and Lexical Equivalence

   Expressing NBNs as URNs 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].

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

   o  a primary prefix, which is a two-letter ISO 3166-1 country code,

   o  zero or more secondary prefixes, each indicated by a delimiting
      colon character (:) and a sub-namespace identifier,

   o  a hyphen (-) as a delimiting character, and

   o  the NBN string.

   The prefix 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 well.

   Different delimiting characters are not semantically equivalent.

   Use of colon as the delimiting character is allowed if and only if
   the country code-based NBN namespace (identified by the respective
   ISO 3166-1 country code used as the primary part of the prefix) is
   split further into smaller sub-namespaces, in which case the colon
   separates the ISO 3166-1 country code from the sub-namespace
   identifier.  These sub-divisions (including the colon separator) form
   an optional part of the prefix.  A colon MUST NOT be used for any
   other purpose in the prefix.

   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.

   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).

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   Being part of the prefix, sub-namespace identifier strings are case-
   insensitive.  They MUST NOT contain any hyphens.

   The sub-namespace identifiers used 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.

   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>

   Examples (using actually assigned NBNs):





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.  For instance, in Finland, the address of the
   national URN 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.

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   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
   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

   URN:NBNs should not be assigned to resources that will not be
   preserved for long term.  If there are multiple copies of the
   resource in the Internet, the resolutuion process SHOULD include all
   of them.  If this is not possible, a URN:NBN should resolve to the
   copy that is deemed to be the most persistent one.

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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 had started in
      demo systems already in 1998.  Since 2001, 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

   Registration Information:

      Version: 4
      Date: 2012-01-19

   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
      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:

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         a prefix, consisting of an ISO 3166-1 alpha-2 country code and
         optional sub-namespace code(s) separated by colon(s),

         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      = iso_cc *( ":" subspc )
                     ; the entire prefix is case-insensitive

       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

       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.

      Whereas the prefix is 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.

      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).

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

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      See Section 4.2 of RFC XXXX 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 resources (and their component parts) that lack a
      'canonical' identifier.  NBN can also be used to identify, e.g.,
      intellectual works and data elements.  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.

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

      The NSS syntax specified in this registration is in full
      conformance with RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn] and
      its predecessor.

   Rules for lexical equivalence of NSS part:

      Prefix, consisting of either ISO 3166-1 country code and its
      (optional) sub-divisions, 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
      3. normalize the case of any percent-encoding;

      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.

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   Identifier uniqueness and persistence considerations:

      It is possible that two national libraries assign the same NBN to
      different documents.  In such case, the prefix guarantees the
      uniqueness of the NBN-based URNs.  URN: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 MUST make sure that they do not assign
      the same NBN twice.  They can utilise different policies for this.
      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 policies 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

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   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
      to identify, e.g., works that these resources manifest, and the
      data elements present in the resource metadata.

6.  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.

7.  IANA Considerations

   IANA is asked to update the existing registration of the Formal URN
   Namespace 'NBN' using the template given above in Section 5.

8.  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

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9.  References

9.1.  Normative References

              Hoenes, A., "Uniform Resource Name (URN) Syntax",
              draft-ietf-urnbis-rfc2141bis-urn-01 (work in progress),
              October 2011.

              Hoenes, A., "Uniform Resource Name (URN) Namespace
              Definition Mechanisms",
              draft-ietf-urnbis-rfc3406bis-urn-ns-reg-01 (work in
              progress), October 2011.

   [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.

9.2.  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.

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   [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
              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.  Significant Changes from RFC 3188

   Numerous clarifications based on a decade of experience with RFC

   Non-ISO 3166 country code based NBNs have been removed due to lack of

   In accordance with established practice, the whole NBN prefix is now
   declared case-insensitive.

   Updated URN:NBN Namespace Registration template for IANA; whole
   document adapted to new URN Syntax document, RFC 2141bis, and new URN
   Namespace Registration document, RFC 3406bis.

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Appendix B.  Draft Change Log

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

B.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.

B.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;
   - 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.

B.3.  draft-ietf-urnbis-rfc3188bis-nbn-urn-01 to -02

   - Removed the possibility of using prefixes not based on country
   - replaced all instances of the word object with resources;
   - removed some redundant/irrelevant paragraphs/subsections;
   - allowed the possibility for identifying data elements with NBNs;
   - a few editorial fixes and enhancements.

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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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