IETF URNbis WG                                            A. Hoenes, Ed.
Internet-Draft                                                    TR-Sys
Obsoletes: 3406 (if approved)                           October 19, 2012
Intended status: BCP
Expires: April 22, 2013

            Defining Uniform Resource Name (URN) Namespaces


   RFC 2141bis formalizes the concept of Uniform Resource Names (URNs)
   for persistent, location-independent, resource identifiers within the
   generic URI system specified in RFC 3986.  To structure and organize
   URN usage, RFC 2141bis specifies a hierarchy that divides the set of
   possible URNs into "URN Namespaces" that can be individually defined
   and managed.  URN Namespaces allow to map existing identifier systems
   into the URN scheme and thereby make available generic, network-based
   resolution services for the identified resources (documents,
   artifacts, and other objects) and metadata related to them.

   To this end, URN Namespaces need to be defined and specified in a
   comparable manner, and their Namespace Identifiers (NIDs) need to be
   registered with IANA, so that naming conflicts are avoided and
   implementers of services can follow a structured approach in support
   of various namespaces, guided by the registry to the related
   documents and the particularities of specific namespaces, as
   described in these Namespace registration documents.

   This RFC serves as a design guideline for stakeholders of URN
   Namespaces and authors of URN Namespace definition and registration
   documents.  It describes the process to be followed to register a URN
   Namespace with IANA and the essential content of such documents.

   This document supersedes and replaces RFC 3406.


   Discussion of this memo utilizes the mailing list.
   [[ RFC-Editor: this clause to be deleted before RFC publication ]]

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Requirement Language and Terminology . . . . . . . . . . .  5
   2.  What is a URN Namespace? . . . . . . . . . . . . . . . . . . .  6
   3.  URN Namespace (Registration) Types . . . . . . . . . . . . . .  8
     3.1.  Experimental Namespaces  . . . . . . . . . . . . . . . . .  8
     3.2.  Informal Namespaces  . . . . . . . . . . . . . . . . . . .  8
     3.3.  Formal Namespaces  . . . . . . . . . . . . . . . . . . . .  8
   4.  URN Namespace Registry: Processes for Registration and
       Update . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     4.1.  Experimental Namespaces: No Registration . . . . . . . . . 11
     4.2.  Informal Namespaces  . . . . . . . . . . . . . . . . . . . 12
     4.3.  Formal Namespaces  . . . . . . . . . . . . . . . . . . . . 13
     4.4.  Registration Documents . . . . . . . . . . . . . . . . . . 14
       4.4.1.  Namespace Considerations in Registration Documents . . 14
       4.4.2.  Community Considerations in Registration Documents . . 15
       4.4.3.  Security Considerations in Registration Documents  . . 16
       4.4.4.  IANA Considerations in Registration Documents  . . . . 16
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 19
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 20
   Appendix A.  URN Namespace Definition Template . . . . . . . . . . 21
     A.1.  Annotated URN Namespace Definition Template  . . . . . . . 21
     A.2.  Plain URN Namespace Definition Template (Informative)  . . 27
   Appendix B.  Summary of Registration Steps (Informative) . . . . . 28
   Appendix C.  Changes from RFC 3406 (Informative) . . . . . . . . . 29
     C.1.  Essential Changes since RFC 3406 . . . . . . . . . . . . . 29
     C.2.  Changes from RFC 3406 to URNbis WG Draft -00 . . . . . . . 29
     C.3.  Changes from URNbis WG I-D -00 to -01  . . . . . . . . . . 32
     C.4.  Changes from URNbis WG I-D -01 to -02  . . . . . . . . . . 32
     C.5.  Changes from URNbis WG I-D -02 to -03  . . . . . . . . . . 32

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1.  Introduction

   Uniform Resource Names (URNs) are identifiers bound to resources with
   the objective to provide location-independent identification of these
   resources as well as longevity of reference.  URNs are part of the
   larger Uniform Resource Identifier (URI) family (see the joint W3C/
   IETF memorandum, RFC 3305 [RFC3305], and the IETF STD 66, RFC 3986
   [RFC3986]), with the specific goal of persistent binding names to

   The URN scheme formalized in RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn] structures and organizes the
   entirety of URNs into a hierarchy that divides the set of possible
   URNs into "URN Namespaces" that can be individually defined, managed,
   and (optionally) further subdivided.  URN Namespaces in particular
   serve to map existing identifier systems into the URN system and
   thereby make available generic, network-based resolution services for
   the identified resources (documents, artifacts, abstract concepts,
   and other objects) and their metadata.

   There are two assumptions that are key to this document:

   Assumption #1:  Assignment of a URN is a managed process.

      I.e., not all strings that conform to URN syntax are necessarily
      valid URNs.  A URN is assigned according to the rules of a
      particular namespace (in terms of syntax, semantics, and process).

   Assumption #2:  The space of URN Namespaces is managed.

      I.e., not all syntactically correct URN Namespace identifiers (per
      the URN syntax definition) designate valid URN Namespaces.  A URN
      Namespace must have a well recognized definition in order to be

   To actually draw benefits from this unification (structured embedding
   of existing namespaces into the URN framework), URN Namespaces have
   common design considerations, they need to be specified in a
   comparable manner, and their Namespace Identifiers (NIDs) need to be
   centrally registered, so that naming conflicts are avoided and
   implementers of services can follow a structured approach in support
   of various namespaces, guided by the registry to the related
   documents and the particularities of specific namespaces, as
   described in these URN Namespace registration documents.

   The primary purpose of this document is to outline a mechanism for
   explicit URN Namespace definition, associating it with an identifier
   (called a "Namespace ID", or NID).  To this end, this RFC defines the

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   requirements for URN NID specification documents and provides a
   registration template, which is to be registered with the Internet
   Assigned Numbers Authority (IANA) [IANA] in the URN Namespaces
   registry maintained at [IANA-URN].  However, to give additional
   guidance to prospective stakeholders / designers of URN Namespaces in
   fulfiling the requirements for registration, this document also
   elaborates on generic considerations and design choices for the
   establishment of URN Namespaces.

   The URN Namespace definition and registration mechanisms originally
   have been specified in BCP 33, RFC 2611 [RFC2611], which has been
   obsoleted by BCP 66, RFC 3406 [RFC3406].  Guidelines for documents
   prescribing IANA procedures have been revised as well over the years,
   and at the time of this writing, BCP 26, RFC 5226 [RFC5226] is the
   normative document.  This document is a revision of RFC 3406 based on
   the revised specification of URNs in RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn] and RFC 5226.

   The reader is referred to Section 1.1 of RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn] for a more detailed synopsis of the
   history of documents fundamental for URNs.

   Note that this document restricts itself to the description of
   processes for the creation of URN Namespaces.  If generic
   "resolution" of any so-created URN identifiers is desired, a separate
   process of registration in a global NID directory, such as that
   proposed by the DDDS system [RFC3401], is necessary.  See [RFC3405]
   for information on obtaining registration in the DDDS global NID
   directory.  RFC 2141bis establishes an IANA registry for URN
   services, such that registration documents can unambiguously identify
   such services and discuss their applicability to the particular URN

1.1.  Requirement Language and Terminology

   When spelled in all-capitals as in this paragraph, the key words
   "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document
   are to be interpreted as described in BCP 14 [RFC2119].  In this
   document, these key words describe requirements for the process to be
   followed and the content to be provided in URN Namespace definition
   documents and registration templates.

   For the purpose of this document, its subject is spelled "URN
   Namespace" (in headline case), whereas in other context, "namespace"
   is spelled in lower case, e.g., to designate a (standard or non-
   standard) identifier system on which a URN Namespace is based.

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2.  What is a URN Namespace?

   For the purposes of URNs, a "namespace" is a collection of uniquely-
   assigned identifiers.  That is, the identifiers are not ever assigned
   to more than one resource.  These resources may be stable (e.g., a
   doctoral dissertation or an abstract concept of a protocol) or
   dynamic (e.g., a continuously evolving web site of a periodical or a
   specific protocol parameter registry subject to additions and
   maintenance).  If the identified resource is a metadata record, such
   record may describe several objects (such as two versions of a book)
   or a collection of objects (such as a periodical with, say, monthly
   issues); in this case, these subordinate objects are not the
   identified resources.  For each namespace, it must be clear what the
   identified resources are; if the namespace is heterogenous in this
   respect, the registration and resolution systems must unambiguously
   designate the kind of identified resource, for each identifier
   assigned in the namespace.  Once assigned, URNs are never re-assigned
   to a different resource.  A single resource, however, may have more
   than one URN assigned to it -- within a particular Namespace or among
   different Namespaces -- for different purposes, since the Namespaces
   are not mutually exclusive.

   Such abstract namespace might be defined by some pre-established
   (standard or non-standard) identifier system that can be made
   "network-actionable" by embedding it into the URN framework using a
   specific URN Namespace.  A URN Namespace itself has an identifier in
   order to:
   -  ensure global uniqueness of URNs,
   -  (where desired) provide a cue for the structure of the identifier.

   For example, many identifier systems use strings of numbers as
   identifiers (e.g., ISBN, ISSN, phone numbers).  It is conceivable
   that there might be some numbers that are valid identifiers in two
   different established identifier systems.  Using different
   designators for the two collections (and making these designators an
   intrinsic syntactic part of URNs) ensures that no two URNs will be
   the same for different resources (since each collection is required
   to uniquely assign each identifier).

   The development of an identifier structure, and thereby a collection
   of identifiers, is a process that is inherently dependent on the
   requirements of the community defining the identifier, how they will
   be assigned, and the uses to which they will be put.  All of these
   issues are specific to the individual community seeking to define a
   namespace (e.g., publishing community, association of booksellers,
   protocol developers, technology-specific vendor groups, etc.); they
   are beyond the scope of the IETF URN work.

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   If a namespace contains structured resources, per RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn] the designers of a related URN
   Namespace and the implementers of the related resolution systems have
   available three options for the Namespace to support identification
   and resolution of component resources:

   a.  A Namespace can choose to assign individual identifiers
       (Namespace Specific String, NSS) to some or all components of a
       structured resource that is also named by the identifier system.
       This method is independent of the Internet media types the
       resolution system(s) for the Namespace can provide.  This is the
       preferred method.  However, there may be rules for a pre-existing
       identifier system (that is going to be made accessible via URNs)
       and objectives for the NSS format desired that effectively
       prohibit such identifier assignments; in such cases, the
       Namespace designers cannot adopt this method.

   b.  A Namespace can choose to provide a resolution system that
       interprets the 'component' ("c=") directive that can be
       incorporated in the <query> part of URI references to URNs (see
       [I-D.ietf-urnbis-rfc2141bis-urn]).  This way, only the basic
       resources are assigned an NSS -- which will simplify the
       identifier assignment/registration processes/systems for the
       namespace, or even be dictated by existing processes/systems --
       and the URN resolvers for the Namespace can make use of
       additional information captured from the owners of the individual
       resources (in any way that is proper for the namespace).  This
       method is independent of the Internet media types that will be
       used to return the URN resolution results for such Namespace, and
       as such allows for stable assigned names yet a flexible, perhaps
       evolving choice of media types provided by the resolution

   c.  A Namespace that tightly controls the media types provided by
       particular resolution services might specify how resolution
       clients can make use of <fragment> identifiers contained in URI
       references to URNs of that Namespace (see
       [I-D.ietf-urnbis-rfc2141bis-urn]) to pick a component resource
       from the media returned by the URN service.  Since per STD 66
       [RFC3986] <fragment> identifiers of URIs are evaluated at the
       client side in a manner specific to each media type (if
       applicable at all), this method depends on the specific
       capabilities of the media types used.

   Namespaces specified prior to RFC 2141bis are constricted to method
   a.  Future Namespace definitions MUST document the methods applicable
   to it and available via its resolvers.

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   This document outlines the processes by which a collection of
   identifiers satisfying certain constraints (uniqueness of assignment,
   etc.) can become a bona fide URN Namespace by obtaining a NID.  In a
   nutshell, a template for the definition of the Namespace is completed
   for deposit with IANA, and a NID is assigned.  The details of the
   process and possibilities for NID strings are outlined below.

3.  URN Namespace (Registration) Types

   There are three categories (types) of URN Namespaces defined here,
   distinguished by expected level of service and required procedures
   for registration.  Registration processes for each of these Namespace
   types are given in Section 4.  In both this Section and Section 4
   these categories are ordered by increasing relevance/importance for
   the Internet and, accordingly, increasing strenght of requirements
   for the definition and registration processes.

3.1.  Experimental Namespaces

   These are not explicitly registered with IANA.

   No provision is made for avoiding collision of experimental NIDs;
   they are intended for use within internal or limited experimental
   contexts.  However, as described below in Section 4.1, these are
   designated by a specific form of the NID to allow differentiation
   (without preexisting knowledge of details) from the other URN
   Namespace types.

3.2.  Informal Namespaces

   These are fully fledged URN Namespaces, with all the rights and
   requirements associated thereto.  Informal Namespaces can be
   registered in global registration services.  They are required to
   uphold the general principles of a well-managed URN Namespace --
   providing persistent identification of resources and unique
   assignment of identifier strings.  Informal and Formal Namespaces
   (described below) differ in the NID assignment.  IANA will assign to
   registered Informal Namespaces a simply structured, alphanumeric,
   ordinal NID (following a pattern defined in Section 4.2 below), per
   the process outlined in Section 4.

3.3.  Formal Namespaces

   A Formal Namespace may be requested, and IETF review sought, in cases
   where the publication of the NID proposal and the underlying
   namespace will provide benefit to some subset of users on the
   Internet.  That is, a formal NID proposal, if accepted, must be
   functional on and with the global Internet, not limited to users in

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   communities or networks not connected to the Internet.  For example,
   assume a NID is requested that is meant for naming of physics
   research material.  If that NID request required that the user use a
   proprietary network or service that was not at all open to the
   general Internet user, then it would make a poor request for a formal
   NID.  The intent is that, while the community of those who may
   actively use the names assigned within that NID may be small (but no
   less important), the potential use of names within that NID is open
   to any user on the Internet.

   It is however expected that Formal NIDs may be applied to Namespaces
   where some aspects are not fully open.  For example, a Namespace may
   make use of a fee-based, privately managed, or proprietary registry
   for assignment of URNs in the Namespace, but it may still provide
   benefit to some Internet users if the services associated with it
   have openly published access protocols.

   In addition to the basic registration information defined in the
   registration template (in Appendix A), a Formal Namespace request
   must be accompanied by documented considerations of the need for a
   new Namespace and of the benefit for the Internet community from
   formally establishing the proposed URN Namespace -- see Sections
   4.4.1 and 4.4.2 below.

   Additionally, since the goal of URNs is to provide persistent
   identification, careful consideration must be given to the longevity
   and maintainability of the URN Namespace.  The collective experience
   of the IETF community contains a wealth of information on technical
   factors that will prevent longevity of identification.  Thus, the
   IESG may elect not to accept a proposed Namespace registration if the
   IETF community consensus is that the registration document contains
   technical flaws that will prevent (or seriously impair the
   possibility of) persistent identification, and that it therefore
   should not be published as an RFC.

   In addition to the technical aspects of the Namespace and its
   resolution, consideration should be given to the following
   organizatorial aspects:

   -  the organization maintaining the URN Namespace should credibly
      demonstrate stability and the ability to maintain the URN
      Namespace for a long time, and/or it should be clear how the
      Namespace can continue to be usable/useful if the organization
      ceases to be able to foster it;

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   -  the organization(s) assigning URNs within the URN Namespace should
      demonstrate ability and competency in name assignment; this should
      improve the likelihood of persistence (e.g., to minimize the
      likelihood of conflicts);

   -  the organization(s) assigning URNs within the URN Namespace need
      to be committed to honor the scope, rules, and regulations
      outlined in its registration document and the documents defining
      the underlying namespace and covering its identifier assignment
      and maintenance procedures (if any), and the organization
      maintaining the URN Namespace needs to have procedures in force
      that aim at ensuring this adherance at a very high confidence
      level; and

   -  the involved organization(s) need to commit to not re-assign
      existing names; old names MUST continue to be valid, even if the
      owners or assignees of those names are no longer members or
      customers of such organization; this does not mean that there
      needs to be resolution of such names, but that they must not
      resolve such names to false or stale information and that they
      must not be reassigned.

   If the underlying namespace is based on an established standard, the
   standards body or the organization(s) in charge with the maintenance
   of the namespace should be involved in the process, either by
   performing the registration on their own, or by supporting the action
   of the registrant and asserting support of the registration document.

   These aspects, though hard to quantify objectively, should be
   considered by organizations/people considering the development of a
   Formal URN Namespace, and they will be kept in mind when evaluating
   the technical merits of any proposed Formal URN Namespace.  The kind
   of mandate upon which the organization aims to undertake this
   activity might give a strong indication for this evaluation, because
   it likely mirrors the trust that other parties (for instance states,
   international treaty organizations, professionals' associations,
   etc.) put on the organization.

4.  URN Namespace Registry: Processes for Registration and Update

   Different levels of disclosure are expected/defined for Namespaces.
   According to the level of open-forum discussion surrounding the
   disclosure, a URN Namespace may be assigned an identifier by IANA or
   may request a particular identifier.

   The IANA Considerations Guidelines document (BCP 26 [RFC5226])
   suggests the need to specify update mechanisms for registrations --
   who is given the authority to do so, from time to time, and what are

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   the processes.  Since URNs are meant to be persistently useful, few
   (if any) changes should be made to the structural interpretation of
   URN strings (e.g., adding or removing rules for lexical equivalence
   that might affect the interpretation of URN IDs already assigned).
   However, it may be important to introduce clarifications, expand the
   list of authorized URN assigners, etc., over the natural course of a
   Namespace's lifetime.  Specific processes are outlined below.

   The official list of registered URN Namespaces is currently
   maintained at [IANA-URN].  The registry is subdivided into two sub-
   registries, one for "Formal URN Namespaces" and one for "Informal URN
   Namespaces", and each entry there links to a stable repository of the
   registration document or (an escrow copy of) the filled-out
   registration template.

   The registration and maintenance procedures vary between the
   Namespace types defined in Section 3.  The process generally makes
   use of the discussion list, where, under the
   auspices of the designated expert(s), volunteering experts and other
   interested parties review URN Namespace proposals.

   NOTE:  The nominal review period on that list (repeatedly quoted
      below) is specified in this document as four weeks.  This is an
      upper limit intended to grant the experts following the list
      sufficient headroom and flexibility.  The designated expert(s) may
      always come to a conclusion earlier, based on personal judgement,
      observation of feedback on the list, and the precedents of a

   Registrations may be revised by updating the Namespace definition
   document using the same process as used for initial registrations,
   including the circulation of the draft form of the revised Namespace
   definition document on the urn-nid discussion list.

4.1.  Experimental Namespaces: No Registration

   The NIDs of Experimental Namespaces (Section 3.1) are not explicitly
   registered with IANA.  They SHOULD take the form:


   where <nid> is a string of up to 30 characters, consisting solely of
   letters, decimal digits, and hyphen ("-") characters, as specified by
   the NID syntax specification in Section 2.1 of RFC 2141bis

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   No provision is made for avoiding collision of experimental NIDs;
   they are intended for use within internal or limited experimental
   contexts exclusively.

   NOTE:  The above form is no more considered MANDATORY, in order to
      accommodate experience and demonstrated evidence that, under
      specific circumstances, experimental prototype systems have to
      create and assign identifiers that the interested community
      perceives are infeasible to be changed once the Namespace gets
      formally registered.  However, it is still RECOMMENDED to prefix
      eventually targeted NIDs by "X-" during experiments and tests.

   As there is no registration, no registration/maintenance procedures
   are needed.

   Usage of Experimental URN Namespaces MUST be short-lived and whithin
   a private scope; it MUST NOT be disclosed to the Internet at large,
   e.g., by distribution of software versions that make use of such.

4.2.  Informal Namespaces

   The NIDs of Informal Namespaces are synthesized by the IANA using an
   assigned sequence number (ordinal) and registered in their own sub-
   registry, as indicated in Section 4; they take the format:


   where <number> is the decimal representation of a natural number,
   with no leading zeroes.  This sequence number is assigned by the IANA
   on a First-Come-First-Served [RFC5226] basis to registration requests
   for Informal Namespaces.

   Registrants should send a copy of the registration template (as shown
   in Appendix A), duly completed, to the mailing list
   for review and allow for a four-week discussion period for clarifying
   the expression of the registration information and suggestions for
   technical improvements to the Namespace proposal.

   After suggestions for clarification of the registration information
   have been incorporated, the template may be submitted for assignment
   of an Informal NID by email to .

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4.3.  Formal Namespaces

   Formal NIDs are assigned via IETF Review and Expert Review, as
   defined in BCP 26 [RFC5226].

   "IETF Review" means that the Formal NID application is made via
   submission to the IETF of an Internet-Draft that contains the
   Namespace definition and targets publication as an RFC of
   Informational or Standards-Track category, which needs to be approved
   by the IESG after performing an IETF Last Call on the document and
   evaluating review comments.  The applicant can be an individual or an
   IETF working group, in alignment with the designation of the
   Internet-Draft.  The actual choice should be properly considered by
   applicants, but it is RECOMMENDED that the registration documents for
   NIDs belonging to an established standard namespace aim at Standards-
   Track, whereas other applications aim at Informational RFC.

   Before publication can be requested, however, the draft Namespace
   specification document must undergo an "Expert Review" process
   [RFC5226] pursuant to the guidelines written here (as well as
   standard RFC publication guidelines).  The designated expert(s) for
   URN Namespace registrations are nominated by the IESG, and their role
   adheres to the guidelines in BCP 26, unless specified otherwise
   below.  The template defined in Appendix A SHOULD be included as part
   of an RFC-to-be defining some other aspect(s) of the Namespace, but
   it MAY be put forward as a Namespace definition document in its own
   right.  The proposed template (including a pointer to a readily
   available copy of the registration document) should be sent to the mailing list for review.  This list is monitored by
   the designated expert(s).  The applicant has to allow for a four-week
   discussion period for clarifying the expression of the registration
   information, and SHOULD improve the Namespace document and/or
   registration template based on the comments received, under the
   guidance of the designated expert(s).  Multiple iterations can be
   performed, before the proposal is accepted and the document can be
   forwarded to the IESG for review at large. the

   Working groups generally SHOULD seek early expert review for a
   Namespace definition document, and individual applicants are also
   advised to seek expert comments early enough.  The aforementioned
   list can be contacted for informal advice at any stage.  The document
   writeup needed for submitting a working group document to the IESG
   requires that all applicable Expert Review processes have been
   followed; this applies to the process described here.

   NIDs for Formal URN Namespaces MUST NOT have the forms indicated in
   the preceding two sections for the other two Namespace types.  The
   proposed NID string MUST conform with the <nid> syntax rule in

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   Section 2.1 of RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn] and it
   MUST adhere to the following additional constraints:

      -  not be an already-registered NID;

      -  not start with "X-" (see Section 4.1 above);

      -  not start with "urn-" (see Section 4.2 above);

      -  not start with "xy-", where xy is any combination of 2 ASCII
         letters (see NOTE below);

      -  not be equal to or start with "example" (see NOTE below);

      -  be more than 2 characters long.

   NOTE:  All two-letter combinations as well as two-letter combinations
      followed by "-" and any sequence of valid NID characters are
      reserved for potential future use as countrycode-based NIDs for
      eventual national registrations of URN Namespaces.  The definition
      and scoping of rules for allocation of responsibility for such
      Namespaces is beyond the scope of this document.
      Further, to avoid confusion, "urn" is not allowed as an NID
      string; To allow neutral example URNs in code and documentation,
      NID strings starting with "example" are set aside for use in
      documentation; IANA has permanently reserved these string to
      prohibit assignment.

   Applicants, in concert with the designated expert(s), should ensure
   that the sought NID strings are "proper" for the designated purpose,
   according to common sense (and applicable legal rules).

4.4.  Registration Documents

   The following subsections describe essential, MANDATORY parts of URN
   Namespace registration documents (beyond the registration template
   specified in Appendix A), which will be focal in the Expert Review
   process and IETF Review.

4.4.1.  Namespace Considerations in Registration Documents

   The Namespace definition document MUST include a section with
   "Namespace Considerations" that outlines the perceived need for a new
   namespace (i.e., where existing namespaces fall short of the
   proposer's requirements).  Part of the expected elaborations need to
   be the arguments why other identifier systems, in particular a
   specific/new URI Scheme would not be suitable for the intended

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   The basis for the expected reasoning can be laid by collecting and
   analyzing the requirements for the new namespace or, if an existing
   identifier system shall be incorporated into the URN system, from
   studying applicable stable (and preferably readily available)
   documents related to that identifier system that can be quoted.
   Particular insight to properly decide whether a new namespace is
   needed can be gained from preparing the explanations to be filled
   into clauses of the Registration template in Appendix A related to:

      -  kind of resources to be named;

      -  URN assignment procedures;

      -  URN resolution/delegation;

      -  type of services to be supported.

   NOTE: It is expected that more than one Namespace may serve the same
   "functional" purpose; the intent of the "Namespace Considerations"
   section is to provide a record of the proposer's "due diligence" in
   exploring existing possibilities, for the IESG's consideration.

   If the need for a new namespace can be demonstrated, it needs to be
   checked whether the requirements and properties of the desired
   identifer system is properly matched to the basic assumptions and
   requirements for URNs -- cf. the Introduction of RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn].  If that is not obvious, it needs
   to be explained in detail in the Namespace Considerations.

   See the trailing NOTE of the next Section for exceptional conditions
   that might allow to waive the need for presenting the above-described
   rationale in a standalone section of a particular Namespace
   definition document.

4.4.2.  Community Considerations in Registration Documents

   The Namespace definition document MUST also include a section with
   "Community Considerations" that indicates the dimensions upon which
   the proposer expects its community to be able to benefit by
   publication of this Namespace, as well as how a general Internet user
   will be able to use the space if they care to do so.

   Again, insight into arguments needed here might be possible to be
   gained by preparing the material to be filled into clauses of the
   Registration template in Appendix A related to:

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      -  (open) assignment and use of identifiers within the Namespace;

      -  open operation of resolution servers for the Namespace

      -  creation of software that can meaningfully resolve and access
         services for the Namespace (client).

   NOTE:  It is acknowledged that occasionally the Namespace
      Considerations and Community Considerations are closely
      intertwined; e.g., this has has been observed in the context of
      legacy identifier systems to be embedded into a URN Namespace.
      If such circumstances can be demonstrated, the Expert Review
      process can waive the requirement to present the two independent
      sections of a Namespace defintition document described in this and
      the preceding Section and concede to the applicant(s) to combine
      the content required for those two mandatory sections into a
      single "Namespace and Community Considerations" section.

4.4.3.  Security Considerations in Registration Documents

   According to the general procurements for RFCs, URN Namespace
   definition documents must include a "Security Considerations" section
   (cf. BCP 72 [RFC3552]).  That section has to identify the security
   considerations specific to the subject URN Namespace.  If the subject
   URN Namespace is based on an underlying namespace, the registration
   can include substantive security considerations described in
   specifications related to that particular namespace by reference to
   these documents.  For general security considerations regarding URN
   usage (and more generally, URI usage), for the sake of clarity and
   brevity, it should refer to the Security Considerations in STD 63
   [RFC3986] and in the URN Syntax document

4.4.4.  IANA Considerations in Registration Documents

   According to the general procurements for RFCs, URN Namespace
   definitions documents must include an "IANA Considerations" section
   (cf. BCP 26 [RFC5226]).  That section has to indicate that the
   document includes a URN Namespace registration template that is to be
   entered into the IANA registry of either Informal or Formal URN

   The completed Namespace registration template included in (or
   referred by) the IANA Considerations section in the published form of
   Registration documents will provide the particular, unique NID string
   that has been assigned, in case of formal Namespaces, by the
   Standards/Protocol Action of the IESG that approved the publication

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   of the registration document as an RFC, or, in case of informal
   Namespaces, by the IANA after successful Expert Review.  As specified
   above in Section 4.3, draft registration documents for formal
   Namespaces usually carry the NID suggested by the registrant (subject
   to the expert review process); otherwise the NID will be assigned by
   the IANA.  RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn] specifies
   that NID strings are ASCII strings that are interpreted in a case-
   insensitive manner, but the NID string SHALL be registered in the
   capitalization form preferred by the registrant.  Additional
   syntactical constraints for NIDs are specified (per Namespace type)
   in Sections 4.2 and 4.3 above.

   Applicants and the designated expert(s) have to ensure that the
   sought NID strings are suitable and proper for the designated purpose
   and not misleading, according to common sense and applicable legal
   rules.  The IETF Review process gives interested parties the
   opportunity to rise concerns if they want to challenge proposed
   strings; the final approval decision still remains with the IESG.

   To avoid clerical accidents, the IANA Considerations Section in
   Namespace registration documents should clearly spell out the
   implications of the registration on the URN Query Parameters
   registries defined in RFC 2141bis [I-D.ietf-urnbis-rfc2141bis-urn],
   if any.  Namespace registration documents have to specify the use or
   non-use of query instructions (by registered keyword) by the
   resolvers related to the respective namespace.  Additionally, they
   can optionally define new query keywords (of specific scope) for that
   Namespace or an entire group of Namespaces.

5.  Security Considerations

   This document largely focuses on providing mechanisms for the
   declaration of public information.  Nominally, these declarations
   should be of relatively low security profile; however, there is
   always the danger of "spoofing" and providing mis-information.
   Information in these declarations should be taken as advisory.

6.  IANA Considerations

   This document outlines the processes for registering URN Namespaces,
   and has implications for the IANA in terms of registries to be
   maintained, as previously defined in RFC 3406 [RFC3406].  This
   document replaces RFC 3406; it contains a revised description for the
   management of the "Uniform Resource Names (URN) Namespaces" IANA
   Registry that uses the policy designation terms from BCP 26, RFC 5226
   [RFC5226], but does not introduce significant changes to the
   applicable procedures described in Section 4 of this RFC.

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   IANA is asked to update the applicable policy for the registry of
   Formal URN Namespaces in the list of protocol parameter registries at, replacing "IETF Consensus Action" by
   "IETF Review after expert review on the urn-nid discussion list
   (designated expert: ...)".

   In both sub-registries of [IANA-URN] (for Formal and Informal
   Namespaces), the registry column headings "URN Namespaces" should be
   changed to "Namespace ID", and "Value" to "Ordinal"; preferably these
   columns should be swapped in both sub-registries.
   [[ DISCUSS: Do we actually need these numerical columns at all? ]]

   IANA is asked to add to both sub-registries of [IANA-URN] a new third
   column entitled "Kind of named resources"; entries into this column
   shall be captured from the respective clause of received registration
   templates conforming to Appendix A.  For legacy entries, the original
   registrants are encouraged to provide proper short descriptions to
   [[ DISCUSS: Shall *we* provide sensical values for legacy entries
   and/or actively poll the Namespace owners instead? ]]

   All references there to the predecessor, [RFC3406], should be
   replaced by references to this document.
   We would appreciate a reorganization of the Registry web page to make
   the registration templates for Informal URN Namespaces directly
   linked from the main page; this would make the page /assignments/
   urn-informal.htm page dispensable (for persistency's sake, the web
   server should redirect requests to the /assignments/urn-namespaces

   Section 4 of this document outlines the general procedures.  Sections
   4.2 and 4.3 above describe the syntax rules for NIDs to which the
   registry needs to obey.

   As pointed out in Section 4.3 above and in RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn], the string "urn" is permanently
   reserved and MUST NOT be assigned as an NID.  All strings starting
   with "example" are permanently reserved for use in code and
   documentation, and hence MUST NOT be assigned as an NID.

   In conformance with BCP 100 [RFC4020], in all cases of new Namespace
   registration proposals, the IANA should provisionally assign the
   appropriate NID (informal or formal), as described throughout the
   body of this memo, once an IESG-designated expert has confirmed that
   the requisite registration process steps have been completed.  These
   registrations become permanent and can be made publicly available
   once the registration document has been approved by the IESG for
   publications as a Standards-Track or Informational RFC.

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   Once a Namespace registration template has been accepted for IANA
   processing, the IANA is expected to also update the "Supported by"
   lists in the registry specified by Section 9.2.1 of RFC 2141bis
   [I-D.ietf-urnbis-rfc2141bis-urn], based on the information supplied
   in the "Usage of query instructions" clause of the registration

7.  Acknowledgements

   This document is heavily based on RFC 3406 (and thereby its
   predecessor, RFC 2611), authored by Leslie Daigle, Dirk-Willem van
   Gulik, Renato Ianella, and Patrik Faltstrom, whose work is cordially

   This document also been inspired by other recent documents that have
   updated important IANA registries, and the countless authors and
   contributors to these efforts are acknowledged anonymously.

   Several individuals in the URNbis working group have participated in
   the detailed discussion of this memo.  Particular thanks for detailed
   review comments and text suggestions go to (in alphabetical order)
   Leslie Daigle Juha Hakala, Subramanian Moonesamy.  Peter Saint-Andre,
   Lars Svensson, and Mykyta Yevstifeyev.

8.  References

8.1.  Normative References

              Hoenes, A., "Uniform Resource Name (URN) Syntax",
              draft-ietf-urnbis-rfc2141bis-urn-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.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

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8.2.  Informative References

   [IANA]     IANA, "The Internet Assigned Numbers Authority",

              IANA, "Uniform Resource Names (URN) Namespace Registry",

   [RFC2276]  Sollins, K., "Architectural Principles of Uniform Resource
              Name Resolution", RFC 2276, January 1998.

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

   [RFC3305]  Mealling, M. and R. Denenberg, "Report from the Joint W3C/
              IETF URI Planning Interest Group: Uniform Resource
              Identifiers (URIs), URLs, and Uniform Resource Names
              (URNs): Clarifications and Recommendations", RFC 3305,
              August 2002.

   [RFC3339]  Klyne, G., Ed. and C. Newman, "Date and Time on the
              Internet: Timestamps", RFC 3339, July 2002.

   [RFC3401]  Mealling, M., "Dynamic Delegation Discovery System (DDDS)
              Part One: The Comprehensive DDDS", RFC 3401, October 2002.

   [RFC3405]  Mealling, M., "Dynamic Delegation Discovery System (DDDS)
              Part Five: URI.ARPA Assignment Procedures", BCP 65,
              RFC 3405, October 2002.

   [RFC3406]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "Uniform Resource Names (URN) Namespace Definition
              Mechanisms", BCP 66, RFC 3406, October 2002.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              July 2003.

   [RFC4020]  Kompella, K. and A. Zinin, "Early IANA Allocation of
              Standards Track Code Points", BCP 100, RFC 4020,
              February 2005.

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

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Appendix A.  URN Namespace Definition Template

   Definition of a URN Namespace is accomplished by completing the
   following information template.  It is provided in two versions; the
   annotated template with comments explaining what should go into the
   filled-out template is shown in Appendix A.1 and the plain template
   that can be used as a starting point for filling in the required
   information via plaintext editing is shown in Appendix A.2.
   To further the application of the template, both forms will be made
   available in xml2rfc form on the IETF Tools and/or IANA web site [[
   to be decided ]].
   In case of (unintended) deviations, Appendix A.1 takes precedence
   over Appendix A.2.

   Apart from providing a mechanism for disclosing the structure of the
   URN Namespace, this information is designed to be useful for

   -  entities seeking to have a URN assigned in a Namespace (if
      applicable) and

   -  entities seeking to provide URN resolvers for a Namespace (if

   This is particularly important for communities evaluating the
   possibility of using a portion of an existing URN Namespace rather
   than creating their own.

   Applications for Formal URN Namespaces must also document "Namespace
   Considerations", "Community Considerations", "Security
   Considerations", and "IANA Considerations", as described in
   Section 4.4.

A.1.  Annotated URN Namespace Definition Template

   Information in the template is as follows (text in curly braces
   describes the expected content and should be removed from filled-in

   Namespace ID:

      { If request is for an Informal NID, indicate so; the number will
      be assigned by IANA.  In the case of a Formal NID registration,
      regularly a particular NID string will be requested. }

   Kind of named resources:

      { Short description of what resources are named under this NID. }

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   Registration Information:

      { This is information to identify the particular version of
      registration information: }
      -  version number:
         { starting with 1, incrementing by 1 with each new version }
      -  date:
         { date submitted to the IANA or date of approval of
         registration document, using the format outlined in "Date and
         Time on the Internet: Timestamps", [RFC3339]: YYYY-MM-DD }

   Declared registrant of the Namespace:

      -  Registering organization:
           Name: { ... }
           Address: { ... }
      -  Designated contact person:
           Name: { ... }
         { Address: ...
           (at least one of: Email, Phone, Postal address) }

   Declaration of syntactic structure of NSS part:

      This clause should outline any structural features of identifiers
      in this Namespace.  At the very least, this description may be
      used to introduce terminology used in other clauses.  This
      structure may also be used for determining realistic caching/
      shortcuts approaches; suitable caveats should be provided.  If
      there are any specific character encoding rules (e.g., which
      character should always be used for single-quotes), these should
      be listed here.

      Answers might include, but are not limited to:
      -  the structure is opaque (no exposition);
      -  a regular expression for parsing the identifier into
         components, including naming authorities;
      -  formal syntax of the NSS, preferably in ABNF (STD 68

   Relevant ancillary documentation:

      This clause should list any RFCs, standards, or other published
      documentation that defines or explains all or part of the
      namespace structure.

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      Answers might include, but are not limited to:
      -  RFCs that outline the syntax of the namespace;
      -  other documents of the defining community (e.g., ISO) that
         outline the syntax of the identifiers in the namespace;
      -  explanatory material that introduces the namespace.

   Conformance with URN Syntax:

      This clause should outline any special considerations required for
      conforming with the URN syntax.  This is particularly applicable
      in the case of legacy naming systems that are used in the context
      of URNs.

      For example, if a namespace is used in contexts other than URNs,
      it may make use of characters that are reserved in the URN syntax.

      This clause should flag any such characters, and outline necessary
      mappings to conform to URN syntax.  Normally, this will be handled
      by percent-encoding the symbol.

   Rules for Lexical Equivalence of NSS part:

      If there are particular algorithms for determining equivalence
      between two identifiers in the underlying namespace (and hence, in
      the URN string itself), rules can be provided here.

      Some examples include:
      -  equivalence between hyphenated and non-hyphenated groupings in
         the identifier string;
      -  equivalence between single-quotes and double-quotes;
      -  namespace-defined equivalences between specific characters,
         such as "character X with or without diacritic marks".

      Note that these are not normative statements for any kind of best
      practice for handling equivalences between characters; they are
      statements limited to reflecting the namespace's own rules.

      However, namespaces that seek to provide higher-level lexical
      equivalence rules should preferably make use of established and
      standardized normalization procedures (like the methods leading to
      the various Unicode Normalization Forms, which would have to be
      applied before UTF-8 encoding) and not invent their own "magic";
      in practice, the utility of such things is likely to be limited
      since test of lexical equivalence is a typical client-side pre-

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      screening operation performed by applications that try to remain
      as general as possible and typically will not have built-in, NID-
      specific knowledge -- ultimately, functional (or semantical)
      equivalence of URNs can only be decided in the NID-specific
      assignment/resolution systems, and their internal rules can be
      handled much more flexibly than more complicated, nailed-down
      lexical equivalence rules that are unlikely to be implemented at

   Usage of query instructions:

      Either say "not applicable" or describe the query instructions
      (keywords and associated values) supported by the resolvers for
      this Namespace (cf. Sections 2.5 and 9.2 of RFC 2141bis).
      Is the "s" keyword supported to select component resources?
      If yes: Which registered services can be selected with it?  What
      is the default/fallback service if "s=" is not given or if the
      value specified for it is unknown/unsupported?
      For which services is the "c" keyword supported (if any)?
      If affirmative, specify the values that can be used with it and
      the behavior if an unrecognized / inapplicable value is used.

   Usage of fragment part:

      Either say "not applicable" if <fragment> parts cannot sensically
      be used with URI references to URNs of this NID,
      or specify (by URN service supported) which media types that
      support fragment identifiers will be returned by the resolvers for
      this Namespace, and the <fragment> designators that will be
      applicable.  (Cf. Section 2.4 of RFC 2141bis.)

   Identifier uniqueness considerations:

      This clause should address the requirement that URN identifiers be
      assigned uniquely -- they are assigned to at most one resource,
      and are not reassigned.

      (Note that the definition of "resource" is fairly broad; for
      example, information on "Today's Weather" might be considered a
      single resource, although the content is dynamic.)

      Possible answers include, but are not limited to:

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      -  exposition of the structure of the identifiers, and
         partitioning of the space of identifiers amongst assignment
         authorities that are individually responsible for respecting
         uniqueness rules;
      -  identifiers are assigned sequentially;
      -  information is withheld; that is, the namespace is opaque.

   Identifier persistence considerations:

      Although non-reassignment of URN identifiers ensures that a URN
      will persist in identifying a particular resource even after the
      "lifetime of the resource", some consideration should be given to
      the persistence of the usability of the URN.  This is particularly
      important in the case of URN Namespaces providing global

      Possible answers include, but are not limited to:
      -  quality of service considerations.

   Process of identifier assignment:

      This clause should detail the mechanisms and/or authorities for
      assigning URNs to resources.  It should make clear whether
      assignment is completely open, or if limited, how to become an
      assigner of identifiers, and/or get one assigned by existing
      assignment authorities.

      Answers could include, but are not limited to:
      -  assignment is completely open, following a particular
      -  assignment is delegated to authorities recognized by a
         particular organization (e.g., the Digital Object Identifier
         Foundation controls the DOI assignment space and its
      -  assignment is completely closed (e.g., for a private

   Process for identifier resolution:

      Which URN resolution services will be supported?
      What is the default service provided by the resolvers for this

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      (The "Usage of query instructions:" clause above only reports
      which services can be selected by the "s" query instruction, if
      If a Namespace is intended to be accessible for global resolution,
      it must be registered in an RDS (Resolution Discovery System, see
      RFC 2276 [RFC2276]) such as the DDDS (see RFC 3401 [RFC3401]).
      Resolution then proceeds according to standard URI resolution
      processes, and the mechanisms of the RDS.  What this clause should
      outline is the requirements for becoming a recognized resolver of
      URNs in this Namespace (and being so listed in the RDS registry).

      Answers may include, but are not limited to:
      -  the Namespace is not listed with an RDS, this is not relevant;
      -  resolution mirroring is completely open, with a mechanism for
         updating an appropriate RDS;
      -  resolution is controlled by entities to which assignment has
         been delegated.

   Validation mechanism:

      Apart from attempting resolution of a URN, a URN Namespace may
      provide mechanisms for "validating" a URN -- i.e., determining
      whether a given string is currently a validly-assigned URN.  There
      are 2 issues here: 1) users should not "guess" URNs in a
      Namespace; 2) when the URN Namespace is based on an existing
      identifier system, it may not be the case that all the existing
      identifiers are assigned on Day 0.  The reasonable expectation is
      that the resource associated with each resulting URN is somehow
      related to the thing identified by the original identifier system,
      but those resources may not exist for each original identifier.
      For example, even if a telephone number-based URN Namespace was
      created, it is not clear that all telephone numbers would
      immediately become "valid" URNs, that could be resolved using
      whatever mechanisms are described as part of the Namespace

      Validation mechanisms might be:
      -  a syntax grammar;
      -  an on-line service;
      -  an off-line service.

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      This clause should outline the scope of the use of the identifiers
      in this namespace, i.e. the precise kind of resources to which the
      URNs are assigned.  Apart from considerations of private vs.
      public namespaces, this clause is critical in evaluating the
      applicability of a requested NID.  For example, a namespace
      claiming to deal with "social security numbers" should have a
      global scope and address all social security number structures
      (unlikely).  On the other hand, at a national level, it is
      reasonable to propose a URN Namespace for "this nation's social
      security numbers".

A.2.  Plain URN Namespace Definition Template (Informative)

   Namespace ID:  ...

   Kind of named resources:  ...

   Registration Information:

      -  version number:  _
      -  date:  yyyy-mm-dd

   Declared registrant of the Namespace:

      -  Registering organization:
           Name: ...
           Address: ...
      -  Designated contact person:
           Name: ...
         { Address: ... }

   Declaration of syntactic structure of NSS part:


   Relevant ancillary documentation:


   Conformance with URN Syntax:


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   Rules for Lexical Equivalence of NSS part:


   Identifier uniqueness considerations:


   .. [[ to be completed in next draft rev if this idea is accepted ]]


Appendix B.  Summary of Registration Steps (Informative)

   The key steps for registration of Informal or Formal Namespaces
   typically play out as follows:

   A) Informal NID:

      1.  Complete the registration template.  This may be done as part
          of an Internet-Draft.

      2.  Communicate the registration template to for
          technical review -- as an email with a pointer to the
          submitted I-D or inline text containing the template.

      3.  Update the registration template (and/or document) as
          necessary from comments, and repeat steps 2 and 3 as

      4.  Once comments have been addressed (and the review period has
          expired), send a request to IANA with the revised registration

   B) Formal NID:

      1.  Write an Internet-Draft describing the namespace and include
          the registration template, duly completed.  Be sure to include
          "Namespace Considerations" and "Community Considerations"
          sections (or a combined section for these), "Security
          Considerations" and "IANA Considerations" sections, as
          described in Section 4.4.

      2.  Submit the Internet-Draft, and send a pointer to the I-D
          (perhaps using a copy of the I-D announcement) to
 in order to solicit technical review.

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      3.  Update the Internet-Draft as necessary from comments, and
          repeat steps 2 and 3 as needed.

      4.  If the Internet-Draft is the product of a working group in the
          IETF, follow the usual WG process to forward the document to
          the IESG for publication as an RFC.  Otherwise, find a
          sponsoring Area Director willing to guide the draft through
          the IESG.  The IESG (or the IETF at large in case an IETF-wide
          last call is deemed necessary) may request further changes
          (submitted as I-D revisions) and/or direct discussion to
          designated working groups, area experts, etc.

      5.  The IESG evaluation process includes a review by IANA, and if
          the IESG approves the document for publication as an RFC, IANA
          processing of the document will follow the regular work-flow
          between the RFC Editor and IANA.  This way, the NID
          registration will be made public by IANA when the RFC is

Appendix C.  Changes from RFC 3406 (Informative)

C.1.  Essential Changes since RFC 3406

   [ RFC Editor: please remove the Appendix C.1 headline and all
   subsequent subsections of Appendix C starting with Appendix C.2. ]

   [[ T.B.D. in next iteration of this memo. ]]

C.2.  Changes from RFC 3406 to URNbis WG Draft -00

   o  Abstract: rewritten entirely;

   o  Section 1 (Introduction): added historical RFC information;

   o  Section 1.1 (Requirements Language): added;

   o  Section 3.1: added Note that challenges the utility of
      Experimental Namespaces and raises question of whether formal
      "provisional" registrations would be useful;

   o  Section 4: text expanded and updated; background material added;
      added Note to challenge IANA website practices;

   o  Section 4.2 ff: changed "home" of URN-NID registration discussion
      list (it already had been moved to the IETF Secretariat servers);

   o  Section 4.2: added Note to challenge the 2-week review period; in
      current practice, that is almost always exceeded, and some regard

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      it as too short;

   o  Section 4.3: largely clarified procedures as they happen in
      practice; adapted language for conformance with RFC 5226; use new
      home of URN-NID (as mentioned above); the registration template
      (Appendix A) now "SHOULD" be used;

   o  Section 4.3: split off new Section 4.4 on Registration Documents,
      because registrants essentially are encouraged to follow these
      guidelines for Informal Namespaces as well, as far as practical;
      replaced "RFC" by "Registration Document"; Section 4.4 is
      subdivided for all mandatory sections;

   o  Section 4.4.1: made requirements a "MUST";

   o  Sections 4.4.1 and 4.4.2: added common Note that challenges the
      need to split Namespace and Community Considerations, based on
      observed problems in practice to separate the topics, and pointing
      to overlap with clauses in the registration template due to
      bullets listed that are not so clearly related to the headlines
      under which they appear; suggestion is to avoid duplication, place
      factual stuff into the template and focus on rationale in these
      Considerations, perhaps in a common section;

   o  Section 4.4.3: added discussion of Security Considerations
      section; advice is to focus on namespace-specific considerations
      and refer to the SecCons in the "generic" RFCs for the general

   o  Section 4.4.4: amended discussion of IANA Considerations section;
      this tries to reflect standing practice and codifies that Formal
      NIDs are generally proposed by the registrant; added Note that
      "urn" is permanently reserved and MUST NOT be assigned as a NID,
      to avoid confusion (as also specified in RFC 2141bis draft); wrt
      registration maintenance: got rid of wrong reference in RFC 3406
      (to RFC 2606);

   o  Section 6 (IANA Considerations): updated and rephrased description
      of the role of this document, including a sketch of the history;
      added teat that tries to precisely describe what is expected from
      IANA on approval of this draft; added text on procedures and
      suggest a provisional assignment practice upon "thumbs-up" of the
      IANA Expert to protect prospective registrants from collateral
      damage on NID precedence in case the document suffers from delays
      unrelated to the registration template before it eventually gets

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   o  Section 7 (Acknowledgements): added;

   o  References: Updated and amended references; added pointers to
      chartered URNbis work items; removed entirely outdated example
      material related to legacy documents;

   o  Appendix A and B.1: added words on Security Considerations

   o  Appendix A (Registration Template): clarified role of text
      snippets in the Template: hint and commentary now all enclosed in
      curly braces, with not that these parts shall be removed when
      filling in the tempalte; indicate that Formal NIDs are normally
      proposed by registrant; changed date/time ref. from ISO 8601 to
      RFC 3339; use inherited term "percent-encoding";

   o  Appendix A -- structure: moved formal clauses on Conformance with
      URN Syntax and Rules for Lexical Equivalence to vicinity of
      namespace specific syntax clause, to which these are closely

   o  Appendix A -- changes of clauses: the Declaration of syntactic
      structure and Rules for Lexical Equivalence clauses now
      tentatively have been restricted to the NSS part only; this change
      is described in NOTEs and motivated by the observation of repeated
      confusion in past and present registration documents, which
      hopefully can be avoided (and the job of the Expert and reviewers
      made easier) by leaving discussion of the invariate parts that
      cannot be re-specified there at the single place where they belong
      to: the NID is fully specified in the initial clause, rules for
      the NID and the URI scheme name "urn" are inherited from RFC
      2141[bis] and RFC 3986, respectively, and hence the new clause
      descriptions avoid conflict by taking these components out of
      scope of these clauses;

   o  Appendix B.1 (Example Template): facelifted a bit; concerns with
      IESG policy on examples in RFCs raised in a NOTE;

   o  Appendix B.2 (Registration steps in practice): updated and
      clarified description of procedure, in alignment to current

   o  Appendix C: removed "Changes from RFC 2611"; added this change

   o  General: numerous editorial changes and enhancements, following
      contemporary RFC style.

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C.3.  Changes from URNbis WG I-D -00 to -01

   Usage of terminology strenghtened.

   Clarified role and usage of Experimental Namespaces.

   Clarified NID strings for Formal Namespaces.

   Added hint that recommends Std. Track RFCs for NID applications based
   on established standard namespaces, and Informational for others.

   Changed standard review period from 2 to 4 weeks (pending

   Resolved with IANA: simple, traditional and generic URL used by IANA
   for the URN Namespace registry.  (Needed to be re-opened in -02!)

   Numerous editorial enhancements and fixes.

C.4.  Changes from URNbis WG I-D -01 to -02

   General text edits based on evaluation of meeting and on-list

   Updated and tightened the organizatorial requirements for Formal
   Namespace requests.

   Restored additional IANA Considerations -- due to observed defects.

   Reserved NID strings "example.*" for documentation (as suggested by
   Larry Masinter, Peter Saint-Andre, and Julian Reschke).

   Added text on possible "higher level" methods to establish lexical
   equivalence of URNs, with the caveats that such things are rather
   unlikely to get traction in general-purpose client software.

   Removed historical Appendix B.1 (Example Template).

   Various editorial enhancements and fixes.

   Updated and expanded "Issues" Appendix (below) in preparation of
   usage of the IETF Issue Tracker.

C.5.  Changes from URNbis WG I-D -02 to -03

   Due to the scattered discussion of the previous draft version, the
   items below not only list effected changes but also give rationale
   for where suggested changes have not been applied.

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   Document title shortened to better reflect entire purpose of

   Abstract: revised and shortened (comments from SM).

   Rephrased 1st para to put emphasis on name binding property (derived
   from list discussion on related topic, Keith Moore et al.).
   Amended / modified text to better reflect the intended audience of
   the memo and its contents, and to accommodate the evolution of the
   rfc2141bis I-D.
   Wordsmithing Assumption: "_well_ recognized" (Lars Svensson).
   Contrary to a proposal (PSA), the draft text keeps the Assumptions
   separate from the consequences/conclusions drawn from these; the
   registration process is what is to be followed to maintain the
   assumption, not the 2nd assumption itself.
   Text reworked based on comments (SM, PSA, et al.).
   The single paragraph with a historical perspective on previous
   documents is deemed rather helpful for the intended audience (note
   the confusing artifact caused by RFC Editor mistake, giving the
   replacement of a BCP a different BCP number!), and it serves to
   capture important motivations for the document revision effort;
   therefore, it is kept in the draft.
   The pargraph describing the purpose of the document has been
   rephrased.  It isn't barely about an IANA procedure, it is also about
   what prospective registrants are well advised to consider before
   deciding on a new Namespace and the processes they have to implement,
   and finally capturing the results in a URN Namespace registration

   Section 2:
   Amended by text describing the 3 methods available to Namespace
   designers / stakeholdes to make component resources of structured
   resources identifiable/accessible.
   Some existing text reworded based on comments (SM et al.).
   It has been argued that text on URN Namespaces in s2 would better be
   placed into the rfc2141bis document, but on the other hand, it has
   been argued that text introducing and discussing Namespace properties
   from rfc2141bis should better be placed into this memo.  To keep both
   documents as much self-contained as practical, text on URN Namespaces
   of specific interest to prospective stakeholders of URN Namespaces
   and authors of registration documents has been kept in s2 of this
   draft, and new such material has been added there.  (The rfc2141bis
   draft now points to this.)

   s3.3: Reworded "benefit" clause to clarify distinction between the
   community interested in a new Namespace and the Internet community at
   large (corollary to comments on and revision of s4.4.2.).

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   s4: (dealing with comments from SM, PSA)
   The justification for the need to consider and specify registration
   maintenance procedures has been in RFC 3406; the text from there has
   been updated according to our chartered, to update for RFC 5226.
   This matter needs to be taken into account by prospective Namespace
   owners, and thus the text makes sense in this document.
   Reorganization of subsequent text made it logically necessary to
   include into this section a high level description of the list.  The nominal review period is left a four
   weeks in this draft revision, but a Note has been added to s4
   indicating that this is an upper limit to accommodate headroom,
   whereas the designated expert(s) may always come to a conclusion
   Repeated references to IANA have been consolidated.
   The common shorthand designation "IANA experts" for the designated
   expert(s) supporting IANA in the maintenance of the URN NID registry
   is now being avoided.

   s4.1: No technical changes.  The continued use of the "X-" prefix for
   Experimental Namespaces does not violate RFC 6648 because this is
   legacy practice, experimental NIDs are not being registered, and this
   memo again prohibits the use of Experimental Namespaces in the open

   Text reorganized, incorporating material from s4.4.4 (see below).
   The text on the (modified) "IETF Review" policy has been upgraded
   from RFC 3406 (and thereby effectively shortened).  It serves to give
   concise information to the expected primary audience of the document,
   applicants for Namespaces, which according to experience are rather
   unlikely inclined to read the full RFC 5226, but just need to know
   what is said in the single sentence in the draft.  Further, this
   sentence supplies the background information for the following
   sentences and thus improved the readability of the text.  Therefore,
   no substantive changes applied here.

   s4.4: text amended to avoid confusion about registration template.

   s4.4.1 and s4.4.2: Heavily reworked based on discussion (Leslie, PSA,
   Juha, et al.).  Bullet lists now point to clauses of the registration
   template where working on the text to be supplied there will likely
   give insights to answer the basic questions to be answered here.
   A NOTE now tentatively allows to include a combined Namespace and
   Community Considerations section into a Namespace registration
   document, if the expert review admits it.

   s4.4.3: The first sentence lays the foundation for the subsequent
   sentences and gives the appropriate reference (to BCP 72); hence it

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   is regarded as non-disposable -- no change.
   Repeated negative experience has motivated the addition of a hint
   that emphasizes that WG documents including URN Namespace definitions
   need to go through the urn-nid process before they can be forwarded
   to the IESG (document writeup requirement).

   s4, s4.4.4: Last paragraph ostensibly belonging to s4.4.4 moved to
   end of s4, then adjusted to context.  (The RFC format doesn't allow
   to recognize the continuation of a higher-level section after the
   inclusion of sub-sections.)

   s4.3, s4.4.4: The checklist of syntactical constraints for NIDs of
   formal namespaces was intended as a checklist for IANA; following
   comments from Lars Svensson, it has been moved from s4.4.4 to s4.3
   and related text has been modified accordingly.

   s4.4.4: substantially revised (comments from Lars Svensson et al.).

   IANA Cons. (s6): Added request to IANA to clarify the procedures for
   Formal NIDs in the list of ptorocol parameter registries.

   Updated and expanded Acknowledgements.

   References: RFC 3339 demoted to Informational; you don't need to read
   it to insert the date into the registration template, the applicable
   pattern is shown there directly; this change avoids a potential
   normative downref.

   Clarified role of Appendices.

   Appendix A:
   Clarified purpose of the explanations in curly braces embedded in the
   annotated registration template.  Use term "clause" throughout.
   Removed Notes from template that served to explain previous changes.
   Template now provided in both annotated and bare form (suggestion
   from SM); once finalized, both forms will be provided in xml2rfc
   format (location to be decided: IETF Tools and/or IANA).
   Added new items to registration template for Purpose of Namespace
   (short description of named resources), applicability of <query> part
   and supported query instructions (if any), and applicability of
   <fragment> part.

   Appendix B: The document organization is carried over from RFC 3406.
   Modified title of App. B, declared it Informative.

   This Appendix C.5 added; previous Appendix D (Issues) dropped.

   Multiple editorial fixes and enhancements.

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Author's Address

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


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