Network Working Group                                          J. Hakala
Internet-Draft                           The National Library of Finland
Obsoletes: 3188 (if approved)                             April 16, 2018
Intended status: Informational
Expires: October 18, 2018

     Using National Bibliography Numbers as Uniform Resource Names


   National Bibliography Numbers, NBNs, are used by the national
   libraries and other organizations in order to identify resources in
   their collections.  Generally, NBNs are applied to resources that are
   not catered for by established (standard) identifier systems such as

   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 RFC 8141 is included.

Relationship to earlier documents

   This draft replaces draft-ietf-urnbis-rfc3188bis-nbn-urn-04, posted

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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   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 18, 2018.

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Copyright Notice

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   document authors.  All rights reserved.

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   Provisions Relating to IETF Documents
   ( in effect on the date of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Discussion list . . . . . . . . . . . . . . . . . . . . .   4
   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 (NID) Registration for the National
       Bibliography Number (NBN) . . . . . . . . . . . . . . . . . .  10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  16
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     10.2.  Informative References . . . . . . . . . . . . . . . . .  17
   Appendix A.  Significant Changes from RFC 3188  . . . . . . . . .  18
   Appendix B.  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  . . . . .  20
     B.3.  draft-ietf-urnbis-rfc3188bis-nbn-urn-01 to -02  . . . . .  20
     B.4.  draft-ietf-urnbis-rfc3188bis-nbn-urn-02 to -03  . . . . .  20
     B.5.  draft-ietf-urnbis-rfc3188bis-nbn-urn-03 to -04  . . . . .  21
     B.6.  draft-ietf-urnbis-rfc3188bis-nbn-urn-04 (2012-10-22) to
           draft-hakala-urn-nbn-rfc3188bis-00  . . . . . . . . . . .  21
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  21

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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] with new definitions and registration procedure in
   2017 [RFC8141].  Any traditional identifier, when used within the URN
   system, must to have a namespace of its own, registered with IANA
   [IANA-URN].  National Bibliography Number (NBN) is one such
   namespace, specified in 2001 in RFC 3188 [RFC3188].

   URN:NBNs are in production use in several European countries
   including (in alphabetical order) Austria, Finland, Germany, Italy,
   Hungary, the Netherlands, Norway, Sweden, and Switzerland.  The
   URN:NBN namespace is collectively managed by these 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 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
   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 8141 [RFC8141].

   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 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.  These partner
   organizations include university libraries, universities and other
   research organizations and governmental organizations.  Some national
   libraries have a lot of these liaisons; for instance, the German
   National Library had almost 400 by early 2018 [NBN-Resolving].

   In practice, NBN differs from standard identifier systems such as
   ISBN and ISSN because it is not a single identifier system with
   standard-specified scope and syntax.  Each NBN implementer creates
   its own system with its own syntax and assignment rules.  Each user

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   organization is also 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 considerably.

   Historically, NBNs were only applied in the national bibliographies
   to identify the resources catalogued into it.  Prior to the emergence
   of bibliographic standard identifiers identifiers in the early 1970s,
   every publication got an NBN.

   Since the late 1990s, the NBN scope has been extended to cover a vast
   range of digitized and born digital resources.  Only a small subset
   of these resources is cataloged in the national bibliographies or
   other bibliographic databases.  Digitized resources and their
   component parts (such as still images in books, or journal articles)
   are examples of resources that may get NBNs.

   It is possible to extend the scope of the NBN much further.  The
   National Library of Finland is using them in the Finnish National
   Ontology Service Finto to identify corporate names (see  NBNs to identify metadata elements provides
   a stable basis for creation of linked data.

   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 [RFC8141].

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

1.1.  Discussion list

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

   [[CREF1: RFC-Editor: this subsection to be deleted before RFC

2.  Conventions used in this document

   "NBN" refers to any National Bibliography Number identifier system
   used by the national libraries and other institutions, which use
   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 collections of national libraries and other institutions that
   are responsible for preserving the cultural heritage of their
   constituents.  Resources in these collections are usually preserved
   for a long time (i.e., for centuries).  While the preferred methods
   for digital preservation may vary over time and depending on the
   content, the favorite one is currently migration.  Whenever
   necessary, a resource in outdated file format is migrated into a more
   modern file format.  All old versions of the resource are also kept,
   in order to alleviate the negative effects of partially successful
   migrations and gradual loss of original look and feel that may
   accompany even fully 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, even if a digitized book has an ISBN, JPEG
   image files of its pages get NBNs.  These URN:NBNs can be used as
   persistent links to the pages.

   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 identifiers and NBNs cover all resources
   the national libraries and their partners need to preserve for the
   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 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
   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

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   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

   The simplest and probably the most common 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.  These 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

   Finally, if the stipulations of the URI Generic Syntax [RFC3986] and
   the Internet media type specification [RFC2046] are met, in
   accordance with the provisions in RFC 8141, the URN f-component MAY
   be attached to URN:NBNs in order to indicate the desired location
   within the resource supplied by URN resolution.

   Note that the f-component is not a part of the NSS and therefore the
   component part is not identified.  Moreover, the resolution process
   SHALL retrieve the entire resource.  The fragment selection is
   applied by the resolution client (e.g., browser) to the media
   returned by the resolution process.  In other words, in this latter
   case the fragments are logical and physical components of the
   identified 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 of the
   identified resource can be supplied.

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   If an NBN identifies an immaterial work, descriptive metadata about
   the work SHOULD be supplied.  The metadata record MAY contain links
   to Internet-accessible digital manifestations of the work.

   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 permanent preservation of their deposit

   Each national library uses NBNs independently of other national
   libraries; apart from this document, there is no global authority
   that specifies or controls NBN usage.  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 information
   resources stored permanently in the national library's digital
   collections or databases.  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 identifier assignment to component parts of resources, and
   specify with sufficient detail the syntax of local component
   identifiers (if there is one as a discernible part of the NBNs).  The
   policy SHOULD also cover any employed extensions to the default NBN
   scope (e.g., to cover identification of metadata 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 8141.

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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 SHOULD 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 subdivisions (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 (the national library MUST be informed about these sub-

   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>






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 <>.

   The country code-based prefix part of the URN:NBN namespace-specific
   string will provide a hint needed to find the correct resolution
   service for URN:NBNs from the global 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 a life time exceeding
   10-20 years can be considered as long.

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   However, it is a common practice to keep also the original and
   previously migrated versions of resources.  Therefore even outdated
   versions of resources can be available, no matter how old or
   difficult to use they have become.

   If all versions of a resource are kept, a user who requires
   authenticity may retrieve the original version of the resource,
   whereas a user to whom the ease of use is a priority is likely to be
   satisfied with the latest version.  In order to enable the users to
   find the best match, an archive can link all manifestations of a
   resource to each other (possibly via a work level metadata record) so
   as to make the users aware of them.

   Thus, even if specific versions of digital resources are not normally
   persistent, persistent identifiers such as URN:NBNs support
   information architectures that enable persistent access to any
   version of the resource, including ones which can only be utilized by
   using digital archeology tools such as custom made applications to
   render the resource.

   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, these services are likely to be long-lived.

4.4.  Additional considerations

   URN:NBNs (or other persistent identifiers) SHOULD be applied to all
   resources which have been prioritized in the organization's digital
   preservation plan.

   URN:NBNs SHOULD NOT be assigned to resources that are known to not be
   persistent.  URN:NBNs MAY however be applied to resources that have a
   low-level preservation priority and will not be migrated to more
   modern file formats.

   If the identified version of a resource has disappeared, the
   resolution process SHOULD supply a surrogate if one exists, such as
   the original printed version of a resource, or a more modern digital
   version of that resource.

5.  URN Namespace ID (NID) 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
   updated IANA template specified in RFC 8141.

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   Namespace ID:  NBN
      This Namespace ID was formally assigned to the National
      Bibliography Number in October 2001 when the namespace was
      registered officially [RFC3188].  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 many national libraries using the system
      have formed new liaisons.

   Kind of named resources:
      Resources (digital or otherwise) in the collections of national
      libraries and their partner organizations.
      Component parts of identified resources.
      Metadata records describing the identified resources.
      Individual data elements in identified metadata records.

   Registration Information:
      Version: 4
      Date: 2018-04-09

   Declared registrant of the namespace:
      Name: 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).  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

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   Formal declaration of the NSS:
      This definition uses 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  = &lt;specific per prefix&gt;
                                         ; MUST adhere to RFC 3986 &lt;path-rootless&gt; 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.

      See Section 4.2 of RFC XXXX for examples.

   Relevant ancillary documentation:

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      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 resources (and
      their component parts) that lack a 'canonical' identifier.  The
      scope of NBN has been extended to also include, e.g., metadata
      records and their 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 8141.

   Conformance with URN syntax:
      The NSS syntax specified in this registration is in full
      conformance with RFC 8141 and its predecessors.

   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 8141 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 r-component and q-component:
      URN:NBN resolvers MAY support several services.  Some of them have
      been formally specified in RFC 2483; some remain unspecified.

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      Examples of existing relevant services are URI to URL or URLs, URI
      to URN or URNs, URI to resource or resources, and URI to resource
      metadata.  In the latter case it is important to be able to
      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
      utilize 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 version of the
      resource; request the latest version of the resource, and request
      rights metadata related to the resource.

      Depending on the technical infrastructure within which digital
      resources are preserved and made available, any service can be
      provided either via q-component, r-component or both.

   Usage of f-component:
      If URI-to-resource service is used and the media type of a
      resource supports the use of an f-component, it can be used to
      indicate a location within the identified resource because NBNs
      SHOULD be assigned to one and only one version of a resource, such
      as a PDF version of an article.

      The URN:NBN Namespace does not impose any restrictions of its own
      on f-component usage.

   Identifier uniqueness and persistence considerations:
      NBNs as such are not unique; different national libraries can
      assign the same NBN to different resources.  Therefore, to
      guarantee the uniqueness of URN:NBNs, a prefix, based on the ISO
      country code, is added to the resource.  An NBN, once it has been
      assigned to a resource, MUST be persistent, and therefore URN:NBNs
      are persistent as well.

      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 NBNs.

   Process of identifier assignment:

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      Assignment of NBN-based URNs MUST be controlled on national level
      by the national library (or national libraries, if there is more
      than one).  National guidelines MAY differ, but 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 national libraries, the scope
      of URN:NBN is already 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 those 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
      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 NBNs 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., component parts of these resources or metadata
      records describing resources or their component parts.

6.  IANA Considerations

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

7.  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

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   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.

8.  Acknowledgements

   Revision of RFC 3188 started during the project PersID [PERSID] Later
   the revision was included in the charter of the URNbis working group
   and worked on in that group in parallel with what became RFC 8141 and
   RFC 8254.  The author wishes to thank his colleagues in the PersID
   project and the URNbis participants for their support and review

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

   John Klensin provided significant editorial and advisory support for
   late versions of the draft.

9.  Contributors

   Alfred Hoenes was the editor and co-author of two of the documents
   from which this one is, in part, derived.  This document would not
   have been possible without his contributions.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,

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   [RFC8141]  Saint-Andre, P. and J. Klensin, "Uniform Resource Names
              (URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,

10.2.  Informative References

              Huttunen, M., Hakala, J., and A. Hoenes, "Using
              International Standard Book Numbers as Uniform Resource
              Names", October 2006.

              draft-ietf-urnbis-rfc3187bis-isbn-urn-03 (Expired draft).

              IANA, "URI Schemes Registry",

              IANA, "URN Namespace Registry",

              ISO, "ISO Maintenance agency for ISO 3166 country codes",
              2006, <>.

              Deutsche Nationalbibliothek, "URN:NBN Resolver fuer
              Deutschland und Schweiz: Information ueber Partner
              Institutionen", Captured 2018-04-09,

   [PERSID]   PersID initiative, 2009-2011, "persid: Building a
              persistent identifier infrastructure",
              Captured 2018-04-09, <>.

   [RFC1321]  Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
              DOI 10.17487/RFC1321, April 1992,

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              DOI 10.17487/RFC2046, November 1996,

   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, DOI 10.17487/RFC2141,
              May 1997, <>.

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   [RFC2288]  Lynch, C., Preston, C., and R. Daniel, "Using Existing
              Bibliographic Identifiers as Uniform Resource Names",
              RFC 2288, DOI 10.17487/RFC2288, February 1998,

   [RFC2611]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "URN Namespace Definition Mechanisms", BCP 33, RFC 2611,
              DOI 10.17487/RFC2611, June 1999,

   [RFC3044]  Rozenfeld, S., "Using The ISSN (International Serial
              Standard Number) as URN (Uniform Resource Names) within an
              ISSN-URN Namespace", RFC 3044, DOI 10.17487/RFC3044,
              January 2001, <>.

   [RFC3187]  Hakala, J. and H. Walravens, "Using International Standard
              Book Numbers as Uniform Resource Names", RFC 3187,
              DOI 10.17487/RFC3187, October 2001,

   [RFC3188]  Hakala, J., "Using National Bibliography Numbers as
              Uniform Resource Names", RFC 3188, DOI 10.17487/RFC3188,
              October 2001, <>.

   [RFC3406]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "Uniform Resource Names (URN) Namespace Definition
              Mechanisms", RFC 3406, DOI 10.17487/RFC3406, October 2002,

   [RFC6234]  Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234,
              DOI 10.17487/RFC6234, May 2011,

   [RFC8254]  Klensin, J. and J. Hakala, "Uniform Resource Name (URN)
              Namespace Registration Transition", RFC 8254,
              DOI 10.17487/RFC8254, October 2017,

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 usage.

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   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 (now retired and merged
   into 2141bis.

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

Appendix B.  Change Log

   [[CREF2: RFC-Editor: Please delete this whole section before RFC

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

   o  formal updates for a WG draft; no more "Updates: 2288";

   o  introduced references to other URNbis WG documents;

   o  changes based on review by Tommi Jauhiainen;

   o  Sect. 3 restructured into namespace and community considerations;

   o  old Sect. 7 incorporated in new Sect. 3.1;

   o  Security Considerations: old Section 4.5 merged into Section 5;

   o  added guidelines for when two manifestations of the same work
      should get different URN:NBNs;

   o  clarified role of ISO 3166/MA for ISO 3166-1 country codes;

   o  clarified role of non-ISO prefix registry maintaind by the LoC;

   o  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-

   o  registration template adapted to rfc3406bis[-00];

   o  numerous editorial fixes and enhancements.

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

   o  Numerous changes to accommodate the outcome of the discussions on
      the urn list;

   o  three different ways of identifying fragments specified;

   o  removed some redundant/irrelevant paragraphs/subsections;

   o  the "one manifestation, one URN" principle strenghtened;

   o  introduced the idea of interlinking manifestations;

   o  extended the scope of the NBN explicitly to works;

   o  added reference to S4.2 in namespace registration;

   o  numerous editorial fixes and enhancements.

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

   o  Removed the possibility of using prefixes not based on country

   o  replaced all instances of the word object with resources;

   o  removed some redundant/irrelevant paragraphs/subsections;

   o  allowed the possibility for identifying data elements with NBNs;

   o  a few editorial fixes and enhancements.

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

   o  improved text related to "prefix" in NSS;

   o  addressed issues with text related to case-sensitivity of NSS

   o  addressed comments and open details on requirements language;

   o  switched language to talk about "resource" instead of "object";

   o  several more editorial fixes and enhancements.

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

   o  specification of how to use URN query and fragment part based on
      the revised versions of rfc2141bis and rfc3406bis;

   o  various textual improvements and clarifications, including:

   o  textual alignments with rfc3187bis draft vers. -03;

   o  multiple editorial fixes and improvements.

B.6.  draft-ietf-urnbis-rfc3188bis-nbn-urn-04 (2012-10-22) to draft-

   o  Conversion of document to XML2RFC format, change of name (not a WG

   o  Adjusted for changes to 2141bis, consolidation of RFC 3406bis,
      creation of transition document.

   o  Made a number of changes to reflect publication of RFC 8141
      (previously 2141bis and 3406bis) and update terminology,
      references, and current status to early 2018.

Author's Address

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


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