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: August 19, 2012                               February 16, 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 European national libraries
   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.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   This Internet-Draft will expire on August 19, 2012.

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Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions used in this document  . . . . . . . . . . . . . .  4
   3.  Fundamental Namespace and Community Considerations for NBN . .  5
     3.1.  The URN:NBN Namespace  . . . . . . . . . . . . . . . . . .  5
     3.2.  Community Considerations for NBNs  . . . . . . . . . . . .  5
   4.  National Bibliography Numbers (NBNs) . . . . . . . . . . . . .  7
     4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.2.  Encoding Considerations and Lexical Equivalence  . . . . .  7
     4.3.  Resolution and Persistence of NBN-based URNs . . . . . . .  9
     4.4.  Additional Considerations  . . . . . . . . . . . . . . . . 10
   5.  URN Namespace ID Registration for the National
       Bibliography Number (NBN)  . . . . . . . . . . . . . . . . . . 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 15
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 16
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 16
   Appendix A.  Significant Changes from RFC 3188 . . . . . . . . . . 17
   Appendix B.  Draft Change Log  . . . . . . . . . . . . . . . . . . 18
     B.1.  draft-hakala-rfc3188bis-nbn-urn-00 to
           draft-ietf-urnbis-*-00 . . . . . . . . . . . . . . . . . . 18
     B.2.  draft-ietf-urnbis-rfc3188bis-nbn-urn-00 to -01 . . . . . . 18
     B.3.  draft-ietf-urnbis-rfc3188bis-nbn-urn-01 to -02 . . . . . . 18
     B.4.  draft-ietf-urnbis-rfc3188bis-nbn-urn-02 to -03 . . . . . . 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 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 February 2012, 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; 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

   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].  Since the current
   ISSN registration does not cover ISSN-L, defined in the new version
   of the ISSN standard, update of the existing namespace registration,
   RFC 3044 [RFC3044] is included in the charter of URNbis.  SICI-based
   URNs have not been specified to date, mainly due to the lack of use
   of SICI.

   The term "National Bibliography Number" encompasses persistent local
   identifier systems that the national libraries and their partner

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   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.

   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.

   As a result of the implementation experiences, the scope of the NBN
   has been expanded further.  They can 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.

   In this memo, "URN:NBN" is used as a shorthand for "NBN-based URN".

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3.  Fundamental Namespace and Community Considerations for NBN

3.1.  The URN:NBN Namespace

   NBNs are widely used to identify both hand-held and digital resources
   covered by legal requirements on national libraries and similar
   institutions to preserve the cultural heritage of their constituents.
   All resources in deposit collections will be preserved for long term.
   While the methods for digital preservation may vary, the favourite
   one is currently migration.  The old versions of a resource 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 with
   NBN-based URIs included in the descriptive metadata.

   NBNs SHOULD only be used for objects when the standard identifiers
   such as ISBN are not applicable.  However, NBNs MAY be used for
   component parts (fragments) even when the identified resources as a
   whole qualify for standard identifiers.  For instance, 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.  NBNs can also be applied to works (which are
   manifested as resources) and, e.g., metadata elements plus terms and
   concepts in ontologies and thesauri.

   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 resources 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 can also provide URN resolution services
   and other technical services to other NBN users.  These other
   organizations MUST either establish their own URN 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 resolve 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.  The
   application 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 Generic Syntax (RFC 3986
   [RFC3986]), the URN 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 are not always available in the
   Internet.  In that case, a surrogate such as a metadata record
   describing the resource can be supplied.  The record can contain
   information about the physical location(s) of the item(s), and links
   to metadata records describing other (possibly digital)
   manifestations of the resource.

   If an NBN identifies a work, descriptive metadata about the work
   SHOULD be supplied.  The metadata record can contain URI-based links
   to Internet-accessible digital manifestations of the work.  Metadata
   records describing these manifestations can be interlinked and they
   may also contain a URI linking them to the work level metadata

   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 URN:NBNs at the global scale [Iso3166MA].

   A national library using URN:NBNs SHOULD specify an assignment
   policy; such policy can limit the URN:NBN usage for instance to the
   resources stored permanently in the national library's digital
   deposit collection.  The resources identified by URN:NBNs SHOULD be
   persistent; NBNs assigned to a short-lived resources SHOULD NOT be
   made URN:NBNs.

   URN:NBN assignment policy SHOULD also clarify the local policy
   concerning fragment identification and outline the local fragment
   syntax in order to enable parsing of the NSS.  The policy MAY clarify
   if works or data elements are within the scope.

   URN:NBN assignment may be automated.  Some national libraries (e.g.,
   Finland, Norway, Sweden) have established Web-based URN generators
   that 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 resources.

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].

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

   o  a prefix, structured as a primary prefix, which is a two-letter
      ISO 3166-1 country code, and zero or more secondary prefixes, each
      indicated by a delimiting colon character (:) and a sub-namespace

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

   o  the NBN string.

   The prefix is case-insensitive.  An NBN string can be either case-
   sensitive or case-insensitive, depending on the NBN syntax applied.
   Future implementers of NBNs MAY make their NBN strings case-

   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).

   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

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   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, URNs might be resolved with the help of a resolver
   discovery service (RDS).  Since no such system has been installed yet
   in the Internet, URN:NBNs 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.  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.

   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.

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   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 a
   resource may have different look and feel, and even different
   intellectual content.  Because of this, each manifestation MUST be
   preserved, and they MUST also have different identifiers.  Any
   intellectual work will eventually be represented by a set of
   manifestations in which the look and feel of each successive version
   is likely to become more and more distant from the original object.

   It is not possible to know in advance which manifestation of a work
   will fit the needs of a particular user best.  A user who requires
   authenticity can prefer the oldest version, whereas a user to whom
   easy access is a priority prefers the latest manifestation.  In order
   to enable the users to switch from one manifestation to the next, it
   is necessary to interlink URN:NBNs belonging to the different
   manifestations of a resource (possibly via a work level metadata
   record) so as to make the users aware of all the existing
   manifestations of the resource and to enable them to retrieve the one
   that matches their interests best.

   Thus, even if manifestations of digital resources are not and will
   not be persistent per se, persistent identifiers such as URN:NBNs may
   support construction of an information architecture that enables
   persistent access to intellectual content, although the look and feel
   of the manifestations of the works will inevitably change over time.

   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 long-lived.

4.4.  Additional Considerations

   URN:NBNs SHOULD NOT be assigned to resources that are known to not be
   presistent.  If there are multiple copies of a resource in the
   Internet, the resolution process MAY be extended to cover them all.
   It the identified manifestation has disappeared, the resolution
   process MAY supply a surrogate, such as a more modern digital version
   of the resource, or the original (printed) version of it.

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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: 2012-02-16

   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:

      The prefix, consisting of an ISO 3166-1 country code and its
      (optional) sub-divisions, is case-insensitive.  The NBN string may
      be case-sensitive or case-insensitive, depending on the rules
      chosen by the NBN authority designated by the prefix; therefore,
      general-purpose resolver clients without sub-namespace specific
      knowledge) MUST treat NBN strings as case-sensitive.  Syntax
      requirements expressed in RFC 2141bis
      [I-D.ietf-urnbis-rfc2141bis-urn] MUST be taken into account.

      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;

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      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:

      It is possible that two national libraries assign the same NBN to
      different documents.  In such case, the prefix guarantees the
      uniqueness of the URN:NBNs.  URN:NBNs, once given to the resource,
      MUST be persistent.

      A URN:NBN, once it has been generated from a NBN, MUST NOT be re-
      used for another resource.

      Users of the URN:NBN namespace MUST ensure that they do not assign
      the same URN:NBN twice.  Different policies can be applied to
      guarantee this.  For instance, NBNs and corresponding URN:NBNs MAY
      be assigned sequentially by programs 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.  National guidelines
      MAY differ, but the common denominator, however, is that the
      identified resources themselves SHOULD be persistent.

      Different URN:NBN assignment policies have resulted in varying
      levels of control of the assignment process.  Manual URN
      assignment by the library personnel provides the tightest control,
      especially if the URN:NBNs cover only resources catalogued into
      the national bibliography.  In most libraries, the scope of URN:
      NBN is much broader than this.  Usage rules MAY vary within one
      country, from one URN:NBN sub-namespace to the next.  As of yet,
      there are no international guidelines for URN:NBN use beyond what
      has been expressed in this document.

   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

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      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.


      NBNs 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
      individual data elements present in the resource metadata.

6.  Security Considerations

   This document proposes means of encoding NBNs as URNs.  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 URN:NBNs.  Issues
   regarding intellectual property rights associated with objects
   identified by the URN: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.

   Beyond the generic security considerations laid out in the underlying
   documents listed in the Normative References (Section 9.1), no
   specific security threats have been identified for NBN-based URNs.

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 and review comments.

   Tommi Jauhiainen has provided feedback on an early version of this
   draft.  The authors wish to thank Tommi Jauhiainen, Bengt Neiss and
   Lars Svensson for the comments they have provided to various versions
   of this draft.

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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.

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

   [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-02 (work in
              progress), February 2012.

              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.

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   [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
              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.

   [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 3188.

   Non-ISO 3166 (country code) based NBNs have been removed due to lack
   of usage.

   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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B.4.  draft-ietf-urnbis-rfc3188bis-nbn-urn-02 to -03

   - improved text related to "prefix" in NSS;
   - addressed issues with text related to case-sensitivity of NSS
   - addressed comments and open details on requirements language;
   - switched language to talk about "resource" instead of "object";
   - several more 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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