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Versions: (draft-hakala-rfc3188bis-nbn-urn) 00 01 02 03 04

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 25, 2013                                 October 22, 2012


     Using National Bibliography Numbers as Uniform Resource Names
                draft-ietf-urnbis-rfc3188bis-nbn-urn-04

Abstract

   National Bibliography Numbers, NBNs, are used by the national
   libraries and other organizations in order to identify various
   resources such as digitized monographs.  Generally, NBNs are applied
   to 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) compliant to the RFC 3406bis draft is included.

Discussion

   Comments are welcome and should be directed to the urn@ietf.org
   mailing list or the authors.
   [[ RFC-Editor: this clause to be deleted before RFC publication ]]

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   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 25, 2013.



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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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   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  . . . . .  8
     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  . . . . . . . . . . . . . . . . . . . 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
     B.4.  draft-ietf-urnbis-rfc3188bis-nbn-urn-02 to -03 . . . . . . 20
     B.5.  draft-ietf-urnbis-rfc3188bis-nbn-urn-03 to -04 . . . . . . 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 traditional identifier, when
   used within the URN system, needs to have a namespace of its own.  At
   the time of this writing, there were 46 registered 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 collectively 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 formally register
   corresponding URN namespaces.  This was in part due to the still
   evolving process to formalize criteria for namespace definition
   documents and registration, consolidated later in the IETF, first
   into RFC 2611 [RFC2611], then into RFC 3406 [RFC3406], and now given
   by RFC 3406bis [I-D.ietf-urnbis-rfc3406bis-urn-ns-reg].

   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 has now been revised so that it covers 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, an update of the existing namespace
   registration is also pursued currently RFC 3044 [RFC3044],

   The term "National Bibliography Number" encompasses persistent local
   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



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   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.
   As of this writing, NBNs are given to, e.g., new books that do not
   have an ISBN.

   During the last 10 years, the NBN scope has been extended to cover a
   vast range of digitized and born digital resources available in 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
   are usually not catalogued but can nevertheless receive an NBN.

   It is possible and even likely that the scope of the NBN will be
   expanded even further.  For instance, NBNs can be used to identify
   metadata elements in order to facilitate creation of linked data.
   NBNs can also be used for identification of (immaterial) works when
   there is no standard identifier that could be used for the type of
   work in question.  Still images are an example of this.

   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 the
   revised URN specification and URN Namespace definition documents (RFC
   2141bis [I-D.ietf-urnbis-rfc2141bis-urn], RFC 3406bis
   [I-D.ietf-urnbis-rfc3406bis-urn-ns-reg]).

2.  Conventions used in this document

   When spelled in all-capitals as in this paragraph, the key words
   "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
   "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document
   are to be interpreted as described in BCP 14 [RFC2119].

   "NBN" refers to any National Bibliography Number identifier system
   used by the national libraries and other institutions using these
   identifiers with the national library's support and 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
   in the deposit collections of national libraries and similar
   institutions that are responsible for preserving the cultural
   heritage of their constituents.  All resources in these collections
   will be preserved for long term.  While the preferred methods for
   digital preservation may vary over time and depending on the content,
   the favourite one is currently migration.  Whenever necessary, a
   document in outdated file format is migrated into a more modern file
   format.  The old versions of a resource are kept, in order to
   alleviate the negative effects of failed migrations and gradual loss
   of original look and feel that often accompany even successful
   migrations.  When there are multiple manifestations of a digital
   object, each one SHOULD have its own NBN.

   NBNs SHOULD only be used for objects when standard identifiers such
   as ISBN are not applicable.  However, NBNs MAY be used for component
   resources even when the resource as a whole qualifies for a standard
   identifier.  For instance, if a digitized book has an ISBN, a JPEG
   file containing a single page of the book can get an NBN.  Then the
   URN:NBN can be used as a persistent link to the page.

   The scope of standard identifier systems such as ISBN and ISSN is
   limited; they are applicable only to certain kinds of resources.
   Generally speaking, 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 immaterial works (which can have 0-n physical
   manifestations, and each manifestation 0-n items) 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.  National libraries can also provide URN resolution services



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   and technical services to other NBN users.  These organizations MUST
   either establish their own URN resolution services or use the
   technical infrastructure provided by the national library.  In the
   URN:NBN namespace, each persistent identifier should be resolvable
   and provide one or more resolution services.

   NBNs MAY be used to identify component resources, but the NBN
   Namespace does not specify a generic, intrinsic syntax for doing
   that.  However, there are at least three different ways in which
   component resources can be identified and used within the NBN
   namespace.

   The simplest approach is to assign a separate NBN for each component
   resource such as a file containing a digitized page of a book, and
   make no provisions to make such NBNs discernible in a systematical
   way from others.  The URN:NBN assigned to the component resource
   enables direct and persistent access to the page, which might
   otherwise be available only via browsing the book from the title page
   to the page wanted.

   Second, a local "fragment" syntax MAY be used to identify component
   resources in a structured manner within the NSS, independently of the
   requirements of RFC 3986.  Such private fragment identifiers SHOULD
   be recognized as such by the appropriate URN resolver application.
   The resolver SHOULD be able to process the fragment part in the URN:
   NBN correctly; if so, the result is the identified component part of
   the resource.  For instance, if the resource is a database table, the
   identified component could be a single data element stored in the
   table.

   Finally, if the stipulations of the URI Generic Syntax (RFC 3986
   [RFC3986]) and the Internet media type specification RFC 2046
   [RFC2046] are met, in accordance with the provisions in RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn], URI fragment identifiers MAY be
   attached to URI references to URN:NBNs in order to designate a
   fragment of the media supplied by URN resolution.

   Note that this implies that the fragment identifier is not a part of
   the NSS, that the resolution process SHALL retrieve the entire
   document, and that the fragment selection is applied by the
   resolution client (e.g., browser) to the media returned by the
   resolution service.  In other words, in this latter case the
   fragments are logical and physical components of the resource whereas
   in the former cases these "fragments" are actually complete,
   independently named entities.

   Resources identified by NBNs are not always available in the
   Internet.  In that case, a surrogate such as a metadata record



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   describing the resource SHOULD be supplied.  These records often
   contain information about the physical location(s) of the item(s), or
   links to related metadata records describing other (possibly digital)
   manifestations of the work in question.

   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
   can also contain a URI linking them 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 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.  National
   libraries are committed to preserving their deposit collections for a
   long time -- at least decades, but the aim is to provide access to
   digital resources for centuries.

   Each national library uses NBNs independently of other national
   libraries; apart from this document, 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, base 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 a local assignment
   policy; such policy SHOULD limit the URN:NBN usage to the digital
   resources stored permanently in the national library's deposit
   collection.  A more liberal URN:NBN assignment policy MAY be applied,
   but NBNs assigned to a short-lived resources SHOULD NOT be made URN:
   NBNs.

   URN:NBN assignment policy SHOULD also clarify the local policy
   concerning component resource identifier assignment and specify with
   sufficient detail the syntax of local component identifiers (if such
   exist as a discernible part of the NBNs).  This syntax will only be



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   understood by the appropriate URN resolvers (that is, the resolvers
   that deal with the namespace in question).  The policy SHOULD also
   cover any employed extensions to the default NBN scope (e.g., to
   cover works or data elements).

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 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
      identifier,

   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-
   insensitive.

   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.



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   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
   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):

      URN:NBN:fi-fe201003181510

      urn:nbn:ch:bel-9039

      urn:nbn:se:uu:diva-3475

      urn:nbn:hu-3006

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 <http://urn.fi>.  Thus the HTTP URI for the Finnish URN
   in the example above is <http://urn.fi/URN:NBN:fi-fe201003181510>.
   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
   https://helda.helsinki.fi/handle/10138/18199).  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.




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   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.  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, digital repositories usually
   preserve each manifestation.  In the URN:NBN namespace, each
   manifestation SHOULD have a different identifier.

   Different users will prefer different manifestations.  A user who
   requires authenticity probably wants the oldest version of the
   resource, whereas a user to whom easy access is a priority is likely
   to be satisfied with the latest manifestation.  In order to enable
   the users to find the best match, it is necessary to interlink URN:
   NBNs belonging to the different manifestations of a resource to each
   other (possibly via a work level metadata record) so as to make the
   users aware of all the existing manifestations of the resource.

   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 which enables
   persistent access to the requested intellectual content.

   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 are likely to be long-lived.

4.4.  Additional Considerations

   URN:NBNs SHOULD NOT be assigned to resources that are known to not be
   persistent (that is, resources that will simply disappear).  URN:NBNs
   MAY be applied to resources which have a low-level preservation
   priority, including resources which are not migrated but only



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   preserved as bits.  URN:NBN or other persistent identifier should be
   applied to the documents which proioritized in the organisation's
   preservation plan.  It the identified manifestation has disappeared,
   the resolution process SHOULD supply an alternative if one exists,
   such as the original printed version which can be used when a
   digitized surrogate has been lost or rendered unreadable.

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

   This URN Namespace registration describes how National Bibliography
   Numbers (NBNs) can be supported within the URN framework; it uses the
   template from RFC 3406bis [I-D.ietf-urnbis-rfc3406bis-urn-ns-reg].

   [[ 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
      liaisons.

   Kind of named resources:

      Preserved publications at the work, manifestation, or data element
      level -- or their metadata.

   Registration Information:

      Version: 4
      Date: 2012-10-22

   Declared registrant of the namespace:

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

      The National Library of Finland registered the namespace on behalf
      of the Conference of the European National Librarians (CENL) and



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      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.  They
      MAY allow other organizations to assign URN:NBNs and use the
      resolution services established by the library for free or for a
      fee.  The fees, if collected, SHOULD 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 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
         authority.

      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.



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      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.

      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
      their partner organizations for identification of deposited
      publications and other resources (and their component parts) that
      lack a 'canonical' identifier.  In the future, the scope of NBN
      can be extended to include, e.g., intellectual works and metadata
      elements.  Each national library uses NBNs 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 locally.  NBNs used in
      national bibliographies contain only characters that belong to the
      US-ASCII character set.  Following the expansion of the NBN scope
      and semi- and fully automated NBN assignment processes, some
      future NBNs MAY contain characters that MUST be translated into
      canonical form according to the specifications in RFC 2141bis
      [I-D.ietf-urnbis-rfc2141bis-urn].

   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



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      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
      sub-divisions);
      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.

   Usage of query instructions:

      URN:NBN resolvers MAY support several global services.  Some of
      them have been specified in RFC 2483; some remain unspecified.
      Examples of existing relevant services are URI to URL or URLs, URI
      to URN or URNs, URI to resource or resources, and URI to URC or
      URCs.  The component directive is relevant especially to the URI
      to URC service, where it can be used to, e.g., indicate the
      preferred metadata format or the completeness of the metadata
      record or the metadata content requested such as table of
      contents.  A URN resolver maintained by a national library can
      consult for instance the national bibliography, digital asset
      management systems and digital preservation systems to supply
      these services.

      Examples of services that can be specified and implemented in the
      future: request the oldest and most original manifestation of the
      resource; request the latest version of the resource, and request
      metadata related to the work.

   Usage of fragment part:

      If URI-to-resource service is used and the media type supports the
      use of URI fragment parts, the users can utilize that to indicate
      locations within the identified resources since NBNs should be
      assigned to one and only one manifestation of a resource.

      The URN:NBN Namespace does not impose any restrictions of its own
      on the fragment identifiers allowed, beyond what the respective
      media type admits.

      It is also possible to specify a local fragment syntax.  By
      default, such syntax will be understood only by the URN resolvers



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      dedicated to the relevant URN:NBN sub-namespace.  This syntax can
      be utilized when it is impractical to assign URN:NBNs to all
      component resources; for instance, a linguistic database can get a
      single URN:NBN, and each concept in the database can be identified
      with a fragment.

   Identifier uniqueness and persistence considerations:

      NBNs as such are not unique; different national libraries can
      assign the same NBN to different documents.  Therefore, something
      must be done to guarantee the uniqueness of the URN:NBNs.  The
      prefix, based on the ISO country code, serves this purpose.  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.





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   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.

   Scope:

      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.

   [[ Editorial Note: this section to be amended by text on URN Query
   Parameter registries, once discussion on versions -03 of rfc2141bis
   and rfc3406bis drafts has settled. ]]

8.  Acknowledgements

   Revision of RFC 3188 started during the project PersID
   (<http://www.persid.org>).  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.



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   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.

9.  References

9.1.  Normative References

   [I-D.ietf-urnbis-rfc2141bis-urn]
              Hoenes, A., "Uniform Resource Name (URN) Syntax",
              draft-ietf-urnbis-rfc2141bis-urn-03 (work in progress),
              October 2012.

   [I-D.ietf-urnbis-rfc3406bis-urn-ns-reg]
              Hoenes, A., "Defining Uniform Resource Name (URN)
              Namespaces", draft-ietf-urnbis-rfc3406bis-urn-ns-reg-03
              (work in progress), October 2012.

   [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

   [I-D.ietf-urnbis-rfc3187bis-isbn-urn]
              Huttunen, M., Hakala, J., and A. Hoenes, "Using
              International Standard Book Numbers as Uniform Resource
              Names", draft-ietf-urnbis-rfc3187bis-isbn-urn-03 (work in
              progress), October 2012.

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

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

   [Iso3166MA]
              ISO, "ISO Maintenance agency for ISO 3166 country codes",
              <http://www.iso.org/iso/country_codes.htm>.



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   [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
              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.





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   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.

   Use of query directives and fragment parts with this Namespace is now
   specified, in accordance with the aforementioned RFCs.


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-
      insensitive;
   -  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
      codes;
   -  replaced all instances of the word object with resources;



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   -  removed some redundant/irrelevant paragraphs/subsections;
   -  allowed the possibility for identifying data elements with NBNs;
   -  a few editorial fixes and enhancements.

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
      strings;
   -  addressed comments and open details on requirements language;
   -  switched language to talk about "resource" instead of "object";
   -  several more editorial fixes and enhancements.

B.5.  draft-ietf-urnbis-rfc3188bis-nbn-urn-03 to -04

   -  specification of how to use URN query and fragment part based on
      the revised versions of rfc2141bis and rfc3406bis;
   -  various textual improvements and clarifications, including:
   -  textual alignments with rfc3187bis draft vers. -03;
   -  multiple editorial fixes and improvements.


Authors' Addresses

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

   Email: juha.hakala@helsinki.fi


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

   Email: ah@TR-Sys.de











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