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Using National Bibliography Numbers as Uniform Resource Names
draft-hakala-urn-nbn-rfc3188bis-01

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 8458.
Author Juna Hakala
Last updated 2018-06-07 (Latest revision 2018-06-02)
Replaces draft-ietf-urnbis-rfc3188bis-nbn-urn
RFC stream Internet Engineering Task Force (IETF)
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Reviews
Stream WG state (None)
Document shepherd Peter Saint-Andre
Shepherd write-up Show Last changed 2018-06-03
IESG IESG state Became RFC 8458 (Informational)
Consensus boilerplate Yes
Telechat date (None)
Needs a YES.
Responsible AD Alexey Melnikov
Send notices to (None)
IANA IANA review state IANA OK - Actions Needed
draft-hakala-urn-nbn-rfc3188bis-01
Network Working Group                                          J. Hakala
Internet-Draft                           The National Library of Finland
Obsoletes: 3188 (if approved)                               June 2, 2018
Intended status: Informational
Expires: December 4, 2018

     Using National Bibliography Numbers as Uniform Resource Names
                   draft-hakala-urn-nbn-rfc3188bis-01

Abstract

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

   A URN (Uniform Resource Names) namespace for NBNs was established in
   2001 in RFC 3188.  Since then, a number of 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
   2012-10-22.

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 https://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 December 4, 2018.

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Copyright Notice

   Copyright (c) 2018 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
   (https://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
     1.1.  Discussion list . . . . . . . . . . . . . . . . . . . . .   5
   2.  Conventions used in this document . . . . . . . . . . . . . .   5
   3.  Fundamental Namespace and Community Considerations for NBN  .   5
     3.1.  The URN:NBN Namespace . . . . . . . . . . . . . . . . . .   5
     3.2.  Community Considerations for NBNs . . . . . . . . . . . .   6
   4.  National Bibliography Number URNs . . . . . . . . . . . . . .   7
     4.1.  Assignment  . . . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   8
       4.2.1.  Usage of r-component and q-component  . . . . . . . .  10
       4.2.2.  Usage of f-component  . . . . . . . . . . . . . . . .  10
     4.3.  Encoding Considerations and Lexical Equivalence . . . . .  10
     4.4.  Resolution and Persistence of NBN-based URNs  . . . . . .  12
     4.5.  Additional considerations . . . . . . . . . . . . . . . .  13
   5.  URN Namespace ID (NID) Registration for the National
       Bibliography Number (NBN) . . . . . . . . . . . . . . . . . .  13
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  16
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     10.2.  Informative References . . . . . . . . . . . . . . . . .  16
   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  . . . . .  19
     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  . . . . .  20

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     B.6.  draft-ietf-urnbis-rfc3188bis-nbn-urn-04 (2012-10-22) to
           draft-hakala-urn-nbn-rfc3188bis-00  . . . . . . . . . . .  21
     B.7.  draft-hakala-urn-nbn-rfc3188bis-00 (2018-04-15) to -01  .  21
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   One of the basic permanent URI schemes (cf.  RFC 3986 [RFC3986],
   [IANA-URI]) is 'URN' (Uniform Resource Name).  URNs were originally
   defined in RFC 2141 [RFC2141].  In 2017, a revision was adopted with
   new definitions and registration procedures [RFC8141].  Any
   traditional identifier, when used within the URN system, must 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, Hungary,
   Italy, 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 (for further discussion of how these systems
   have evolved as URNs, see the discussion in RFC 8254 [RFC8254]) 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 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.  ISBN and ISSN
   namespaces were made compliant with RFC 8141 [RFC8141] in 2017 by
   publishing revised ISSN [ISSN-namespace] and ISBN [ISBN-namespace]
   namespace registrations.

   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.  These partner
   organizations include universities and their libraries and other
   subsidiaries, other research institutions, plus governmental
   organizations and commercial companies such as publishers.  Some
   national libraries maintain a significant number of these liaison
   relationships; 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
   organization is also obliged to keep track of how NBNs are being
   used; however, within the generic framework set in this document,
   local NBN assignment policies may vary considerably.

   Historically, NBNs have been applied in the national bibliographies
   to identify the resources catalogued into them.  Prior to the
   emergence of bibliographic standard identifiers in the early 1970s,
   national libraries assigned NBNs to all catalogued publications.

   Since the late 1990s, the NBN scope has been extended to cover a vast
   range of resources, both originally digital and digitized.  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
   http://finto.fi/cn/en/).  Using 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 by 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",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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1.1.  Discussion list

   Comments are welcome and should be directed to the urn@ietf.org
   mailing list or to the author.

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

2.  Conventions used in this document

   "NBN" refers to any National Bibliography Number identifier system
   used by the national libraries (or equivalent organizations) and
   other institutions, which use these identifiers with national
   libraries' support and permission.

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

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 depend on the
   content, the most commonly used one is currently migration.  Whenever
   necessary, a resource in outdated file format is migrated into a more
   modern file format.  To the extent possible, 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 NBNs
   are used to identify manifestations and there are many of them for a
   single work, local policy MAY mandate that each manifestation ought
   to have its own NBN.  An NBN MAY also be used to identify works and
   expressions; in such a role it can interconnect the manifestations.

   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 might be assigned 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 give (national)

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   libraries an identifier system they can control and that can be used
   in addition or in parallel to other established systems.
   Collectively, the standard identifiers and NBNs cover all resources
   the national libraries and their partners need to preserve for the
   long term while recognising that there might be significant overlap
   between the systems.

   Section 4 below, and particularly Section 4.1, present 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 the 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 are
   expected to either establish their own URN resolution services or use
   the technical infrastructure provided by the national library.
   URN:NBNs are expected to be resolvable and support 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 two different ways in which
   component resources can be taken into account within the NBN
   namespace.

   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, 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.

   From the library community point of view it is important that the
   f-component is not a part of the NSS and therefore f-component

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   attachment does not mean that the relevant component part is
   identified.  Moreover, the resolution process still retrieves the
   entire resource even if there is an f-component.  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.  If one is not and there are no other resolution services
   available, the URN:NBN SHOULD resolve to a surrogate such as a
   metadata record describing the identified resource.

   If an NBN identifies a 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 particularly its Section 4.4, 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 Number URNs

4.1.  Assignment

   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
   collections.

   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 can differ, but the identified resources
   themselves SHOULD be persistent.

   Different national URN:NBN assignment policies have resulted in
   varying levels of control of the assignment process.  Manual URN:NBN
   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 can vary
   within one country, from one URN:NBN sub-namespace to the next.

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   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 (referred to as "ISO
   country code" below) [ISO3166-1].  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 for itself; such policy MAY limit the URN:NBN usage to the
   information resources stored in the national library's digital
   collections or databases.  A more liberal URN:NBN assignment policy
   MAY be applied, but NBNs assigned to 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).

   NBNs as such are not unique; different national libraries can assign
   the same NBN to different resources.  A prefix, based on the ISO
   country code as described above, guarantees the uniqueness of
   URN:NBNs across countries.  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] as NBNs.

4.2.  Syntax

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

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

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

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

   The following formal definition uses ABNF [RFC5234].

      nbn_nss     = prefix "-" nbn_string

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

      iso_cc      = 2ALPHA
                  ; alpha-2 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  = path-rootless
                  ; the "path-rootless" rule is defined in RFC 3986.
                  ; syntax requirements specified in RFC 8141 MUST be
                  ; taken into account.

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

   The structure (if any) of the nbn_string is determined by the
   authority for the prefix.  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 is
   the responsibility of the relevant 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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   Note: Because case mapping for ASCII letters is completely reversible
   and does not lose information, the case used in case-insensitive
   matching is a local matter; implementations can convert to lower or
   upper case as they see fit; they only need to do it consistently.

4.2.1.  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.
   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, the completeness of the metadata
   record, or the metadata content requested, e.g., a 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 include requests for the oldest and most original version of
   the resource, the latest version of the resource, and 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 via q-component, r-component or both, as long as the usage
   of these components is consistent with RFC 8141 or its successors.

4.2.2.  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.

4.3.  Encoding Considerations and Lexical Equivalence

   Expressing NBNs as URNs is usually straightforward, as only ASCII
   characters are allowed in NBN strings.  If necessary, NBNs MUST be
   translated into canonical form as specified in RFC 8141.

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

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   o  a prefix, structured as a primary prefix, which is a two-letter
      ISO 3166-1 country code of the library's country, 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.

   Different delimiting characters are not semantically equivalent.

   The syntax and roles of the three parts listed above are described in
   Section 4.2.

   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 its own NBN sub-namespace to
   trusted organization(s) such as a university or a government
   institution.  The sub-namespace MAY be further divided by the partner
   organization.  All 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.

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

   Formally, two URN:NBNs are lexically equivalent if they are octet-
   by-octet equal after the following (conceptional) preprocessing:

   1.  convert all characters in the leading "urn:nbn:" token to a
       single case;

   2.  convert all characters in the prefix (country code and its
       optional sub-divisions) to a single case;

   3.  convert all characters embedded in any percent-encodings to a
       single case;

   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>

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   Examples:

      URN:NBN:fi-fe201003181510

      urn:nbn:ch:bel-9039

      urn:nbn:se:uu:diva-3475

      urn:nbn:hu-3006

4.4.  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>.

   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.

   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 can 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

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   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.

4.5.  Additional considerations

   URN:NBNs (or other persistent identifiers) SHOULD be applied to all
   resources that 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.

   Namespace Indentifier:  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.

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   Version:  4

   Date:  2018-04-09

   Registrant:
      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
      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.

   Purpose:  See Section 3 of RFC XXXX

   Syntax:  See Section 4.2 of RFC XXXX

   Assignment:  See Section 4.1 of RFC XXXX

   Security and Privacy:  See Section 7 of RFC XXXX

   Interoperability:
      National libraries and their partners use URN:NBNs only if a
      standard identifier such as ISBN is not applicable for the
      resource to be identified.  Significant overlap with other URN
      namespaces is therefore unlikely.

      URN:NBNs may contain characters which must be percent-encoded, but
      usually they consist of printable ASCII characters representing
      themselves.

   Resolution:  See Section 4.4 of RFC XXXX

   Documentation:  RFC XXXX

   Revision Information:
      Version 4 of the URN:NBN namespace was updated to use the revised
      definition of URN syntax from RFC 8141.  In particular, use of
      query components and fragment components is now specified.  In
      addition, non-ISO 3166 (country code) based NBNs have been removed
      due to lack of deployment.  The entire NBN prefix is now specified

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      to be case-insensitive in accordance with established practice.
      This version also includes numerous clarifications based on a
      decade of experience with RFC 3188.

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 defines 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.

   Although no validation mechanisms are specified on the global level
   (beyond a routine check of those characters that require special
   encoding when employed in URIs), NBNs assigned by any given authority
   can have a well-specified and rich syntax (including, e.g., fixed
   length and checksum).  In such cases, it is possible to validate the
   correctness of NBNs programmatically.

   Issues regarding intellectual property rights associated with objects
   identified by the URN:NBNs are 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 10.1), 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 comments.

   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.

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

9.  Contributors

   This document would not have been possible without contributions by
   Alfred Hoenes.

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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC8141]  Saint-Andre, P. and J. Klensin, "Uniform Resource Names
              (URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,
              <https://www.rfc-editor.org/info/rfc8141>.

10.2.  Informative References

   [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>.

   [ISBN-namespace]
              Griffiths, S., "Namespace Registration for International
              Standard Book Number (ISBN) ISO 2108:2017",
              <https://www.iana.org/assignments/urn-formal/isbn>.

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   [ISO3166-1]
              ISO, "Codes for the representation of names of countries
              and their subdivisions -- Part 1: Country codes",
              ISO 3166-1:2013, 2013,
              <https://www.iso.org/standard/63545.html>.

   [Iso3166MA]
              ISO, "ISO Maintenance agency for ISO 3166 country codes",
              2006, <http://www.iso.org/iso/country_codes.htm>.

   [ISSN-namespace]
              Bequet, G., "Namespace Registration for International
              Standard Serial Number (ISSN) and Linking ISSN (ISSN-L)
              based on ISO 3297:2007",
              <https://www.iana.org/assignments/urn-formal/issn>.

   [NBN-Resolving]
              Deutsche Nationalbibliothek, "URN:NBN Resolver fuer
              Deutschland und Schweiz: Information ueber Partner
              Institutionen", Captured 2018-04-09,
              <https://nbn-resolving.org/institutions>.

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

   [RFC1321]  Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
              DOI 10.17487/RFC1321, April 1992,
              <https://www.rfc-editor.org/info/rfc1321>.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              DOI 10.17487/RFC2046, November 1996,
              <https://www.rfc-editor.org/info/rfc2046>.

   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, DOI 10.17487/RFC2141,
              May 1997, <https://www.rfc-editor.org/info/rfc2141>.

   [RFC2288]  Lynch, C., Preston, C., and R. Daniel, "Using Existing
              Bibliographic Identifiers as Uniform Resource Names",
              RFC 2288, DOI 10.17487/RFC2288, February 1998,
              <https://www.rfc-editor.org/info/rfc2288>.

   [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,
              <https://www.rfc-editor.org/info/rfc2611>.

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   [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, <https://www.rfc-editor.org/info/rfc3044>.

   [RFC3187]  Hakala, J. and H. Walravens, "Using International Standard
              Book Numbers as Uniform Resource Names", RFC 3187,
              DOI 10.17487/RFC3187, October 2001,
              <https://www.rfc-editor.org/info/rfc3187>.

   [RFC3188]  Hakala, J., "Using National Bibliography Numbers as
              Uniform Resource Names", RFC 3188, DOI 10.17487/RFC3188,
              October 2001, <https://www.rfc-editor.org/info/rfc3188>.

   [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,
              <https://www.rfc-editor.org/info/rfc3406>.

   [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,
              <https://www.rfc-editor.org/info/rfc6234>.

   [RFC8254]  Klensin, J. and J. Hakala, "Uniform Resource Name (URN)
              Namespace Registration Transition", RFC 8254,
              DOI 10.17487/RFC8254, October 2017,
              <https://www.rfc-editor.org/info/rfc8254>.

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.

   The document is based on the new URN Syntax specification, RFC 8141.

   Use of query components and fragment components with this Namespace
   is now specified, in accordance with RFC 8141.

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Appendix B.  Change Log

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

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-
      insensitive;

   o  registration template adapted to rfc3406bis[-00];

   o  numerous editorial fixes and enhancements.

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;

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   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
      codes;

   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
      strings;

   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.

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.

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B.6.  draft-ietf-urnbis-rfc3188bis-nbn-urn-04 (2012-10-22) to draft-
      hakala-urn-nbn-rfc3188bis-00

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

   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.

B.7.  draft-hakala-urn-nbn-rfc3188bis-00 (2018-04-15) to -01

   o  Extensive editorial corrections in response to issues identified
      during IETF Last Call

Author's Address

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

   Email: juha.hakala@helsinki.fi

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