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Uniform Resource Names (URN) Namespace Definition Mechanisms
RFC 3406

Document Type RFC - Best Current Practice (October 2002) Errata
Obsoleted by RFC 8141
Obsoletes RFC 2611
Authors Dirk-Willem van Gulik , Patrik Fältström , Leslie Daigle , Dr. Renato Iannella
Last updated 2020-01-21
RFC stream Internet Engineering Task Force (IETF)
Additional resources Mailing list discussion
IESG Responsible AD (None)
Send notices to (None)
RFC 3406
Network Working Group                                          L. Daigle
Request for Comments: 3406                      Thinking Cat Enterprises
BCP: 66                                                   D.W. van Gulik
Obsoletes: 2611                                               WebWeaving
Category: Best Current Practice                              R. Iannella
                                                             IPR Systems
                                                            P. Faltstrom
                                                            October 2002

      Uniform Resource Names (URN) Namespace Definition Mechanisms

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.


   This document lays out general definitions of and mechanisms for
   establishing Uniform Resource Names (URN) "namespaces".  The URN WG
   has defined a syntax for URNs in RFC 2141, as well as some proposed
   mechanisms for their resolution and use in Internet applications in
   RFC 3401 and RFC 3405.  The whole rests on the concept of individual
   "namespaces" within the URN structure.  Apart from proof-of-concept
   namespaces, the use of existing identifiers in URNs has been
   discussed in RFC 2288.

Table of Contents

   1.0 Introduction ................................................. 2
   2.0 What is a URN Namespace? ..................................... 3
   3.0 URN Namespace (Registration) Types ........................... 3
   3.1 Experimental Namespaces .....................................  4
   3.2 Informal Namespaces .........................................  4
   3.3 Formal Namespaces ...........................................  4
   4.0 URN Namespace Registration, Update, and NID Assignment
       Process .....................................................  6
   4.1 Experimental ................................................  6
   4.2 Informal ....................................................  6
   4.3 Formal ......................................................  7
   5.0 Security Considerations .....................................  9

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   6.0 IANA Considerations .........................................  9
   7.0 References ..................................................  9
   Appendix A -- URN Namespace Definition Template ................. 11
   Appendix B -- Illustration ...................................... 15
   B.1 Example Template ............................................ 15
   B.2 Registration steps in practice .............................. 17
   Appendix C -- Changes from RFC 2611 ............................. 18
   C.1 Detailed Document Changes ................................... 19
   Authors' Addresses .............................................. 21
   Full Copyright Statement ........................................ 22

1.0 Introduction

   Uniform Resource Names (URNs) are resource identifiers with the
   specific requirements for enabling location independent
   identification of a resource, as well as longevity of reference.
   URNs are part of the larger Uniform Resource Identifier (URI) family
   [RFC3305] with the specific goal of providing persistent naming of

   There are 2 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 namespaces (per the URN
      syntax definition) are valid URN namespaces.  A URN namespace must
      have a recognized definition in order to be valid.

   The purpose of this document is to outline a mechanism and provide a
   template for explicit namespace definition, as well as provide the
   mechanism for associating an identifier (called a "Namespace ID", or
   NID) which is registered with the Internet Assigned Numbers Authority

   Note that this document restricts itself to the description of
   processes for the creation of URN namespaces.  If "resolution" of any
   so-created URN identifiers is desired, a separate process of
   registration in a global NID directory, such as that provided by the

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   DDDS system [RFC3401], is necessary.  See [RFC3405] for information
   on obtaining registration in the DDDS global NID directory.

2.0 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 1 resource, nor are they ever re-assigned to a different
   resource.  A single resource, however, may have more than one URN
   assigned to it for different purposes.  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

   For example, many identifier systems may 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 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, etc); they are beyond the scope of the IETF URN

   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.

3.0 URN Namespace (Registration) Types

   There are three categories 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 4.0.

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3.1  Experimental Namespaces

   These are not explicitly registered with IANA.  They take the form:


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

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 an
   alphanumeric NID to registered informal namespaces, per the process
   outlined in Section 4.0.

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
   communities or networks not connected to the Internet.  For example,
   a NID that is meant for naming of physics research is requested.  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 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 have openly-
   published access protocols.

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   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 community benefit from formally establishing
   the proposed URN namespace.

   Additionally, since the goal of URNs is to provide persistent
   identification, some consideration as to the longevity and
   maintainability of the namespace must be given.  The URN WG discussed
   at length the issue of finding objective measures for predicting (a
   priori) the continued success of a namespace.  No conclusion was
   reached -- much depends on factors that are completely beyond the
   technical scope of the namespace.  However, the collective experience
   of the IETF community does contain a wealth of information on
   technical factors that will prevent longevity of identification.  The
   IESG may elect not to publish a proposed namespace RFC if the IETF
   community consensus is that it contains technical flaws that will
   prevent (or seriously impair the possibility of) persistent

   The kinds of things the URN WG discussed included:

      -  the organization maintaining the URN namespace should
         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;

      - it should demonstrate ability and competency in name assignment.
         This should improve the likelihood of persistence (e.g. to
         minimize the likelihood of conflicts);

      -  it should commit to not re-assigning existing names and
         allowing old names to continue to be valid, even if the owners
         or assignees of those names are no longer members or customers
         of that organization.  This does not mean that there must be
         resolution of such names, but that they must not resolve the
         name to false or stale information, and that they must not be

   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 namespace.

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4.0 URN Namespace Registration, Update, and NID Assignment Process

   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 or may request a
   particular identifier.  The  "IANA Considerations" document [RFC2434]
   suggests the need to specify update mechanisms for registrations --
   who is given the authority to do so, from time to time, and what are
   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 maintained by IANA.
   URN namespace registrations are currently being posted in the
   anonymous FTP directory:

   See [RFC3232] for the current location of IANA registry.

   The registration and maintenance procedures vary slightly from one
   namespace type (as defined in Section 3.0) to another.

4.1 Experimental

   These are not explicitly registered with IANA.  They take the form:


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

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

4.2 Informal

   These are registered with IANA and are assigned a number sequence as
   an identifier, in the format:

      "urn-" <number>

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   where <number> is chosen by the IANA on a First Come First Served
   basis (see [RFC2434]).

   Registrants should send a copy of the registration template (see
   Appendix A), duly completed, to:

   and allow for a 2 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 a NID to:

   The only restrictions on <number> are that it consist strictly of
   digits and that it not cause the NID to exceed length limitations
   outlined in the URN syntax ([RFC2141]).

   Registrations may be updated by the original registrant, or an entity
   designated by the registrant, by updating the registration template,
   submitting it to the discussion list for a further 2 week discussion
   period, and finally resubmitting it to IANA, as described above.

4.3 Formal

   Formal NIDs are assigned via IETF Consensus, as defined in [RFC2434]:

      "IETF Consensus - New values are assigned through the IETF
      consensus process.  Specifically, new assignments are made via
      RFCs approved by the IESG.  Typically, the IESG will seek input on
      prospective assignments from appropriate persons (e.g., a relevant
      Working Group if one exists)."

   Thus, the Formal NID application is made via publication of an RFC
   through standard IETF processes.  The RFC need not be standards-
   track, but it will be subject to IESG review and acceptance pursuant
   to the guidelines written here (as well as standard RFC publication
   guidelines).  The template defined in Appendix A may be included as
   part of an RFC defining some other aspect of the namespace, or it may
   be put forward as an RFC in its own right.  The proposed template
   should be sent to the:

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   mailing list to allow for a two week discussion period for clarifying
   the expression of the registration information, before the IESG
   reviews the document.

   The RFC must include a "Namespace Considerations" section, which
   outlines the perceived need for a new namespace (i.e., where existing
   namespaces fall short of the proposer's requirements).

   Considerations might include:

      -  URN assignment procedures
      -  URN resolution/delegation
      -  type of resources to be identified
      -  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.

   The RFC must also include a "Community Considerations" section, which
   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.  Potential considerations include:

      -  open assignment and use of identifiers within the namespace
      -  open operation of resolution servers for the namespace (server)
      -  creation of software that can meaningfully resolve and access
         services for the namespace (client)

   The RFC must include an "IANA Considerations" section, indicating
   that the document includes a URN NID registration that is to be
   entered into the IANA registry of URN NIDs.

   A particular NID string is requested, and is assigned by IETF
   consensus (as defined in [RFC2434]), with the additional constraints
   that the NID string must:

      -  not be an already-registered NID
      -  not start with "x-" (see Type I above)
      -  not start with "urn-" (see Type II above)
      -  not start with "XY-", where XY is any combination of 2 ASCII
         letters  (see NOTE, below)
      -  be more than 2 letters long

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   NOTE: ALL two-letter combinations, and two-letter combinations
   followed by "-" and any sequence of valid NID characters are reserved
   for potential 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.

   Registrations may be revised by updating the RFC through standard
   IETF RFC update processes (see [RFC2606] for a discussion of IETF
   process).  In any case, a revised document, in the form of a new
   Internet-Draft, must be published, and the proposed updated template
   must be circulated on the urn-nid discussion list, allowing for a 2
   week review period before pursuing publication of the new RFC

5.0 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.

6.0 IANA Considerations

   This document outlines the processes for registering URN namespaces,
   and has implications for the IANA in terms of registries to be
   maintained.  In all cases, the IANA should assign the appropriate NID
   (informal or formal), as described above, once an IESG-designated
   expert has confirmed that the requisite registration process steps
   have been completed.  This document defines processes to replace
   those outlined in [RFC2611].

7.0 References

   [ISO8601] ISO 8601 : 1988 (E), "Data elements and interchange formats
             - Information interchange - Representation of dates and

   [RFC1737] Sollins, K. and L. Masinter, "Functional Requirements for
             Uniform Resource Names", RFC 1737, December 1994.

   [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
             3", BCP 9, RFC 2026, October 1996.

   [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997.

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

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

   [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
             IANA Considerations Section in RFCs", BCP 26, RFC 2434,
             October 1998.

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

   [RFC3232] Reynolds, J, Editor, "Assigned Numbers: RFC 1700 is
             Replaced by an On-line Database", RFC 3232, January 2002.

   [RFC3305] Mealling, M. (Ed.) and R. Denenberg (Ed.), "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.

   [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", RFC 3405,
             October 2002.

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Appendix A -- URN Namespace Definition Template

   Definition of a URN namespace is accomplished by completing the
   following information template.  Apart from providing a mechanism for
   disclosing structure of the URN namespace, this information is
   designed to be useful for

      -  entities seeking to have a URN assigned in a namespace (if
      -  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" and "IANA
   Considerations", as described in Section 4.3.

   Information in the template is as follows:

   Namespace ID:

      Assigned by IANA.  In the case of a Formal NID registration, a
      particular NID string may be requested.

   Registration Information:

      This is information to identify the particular version of
      registration information:

      -  registration version number: starting with 1, incrementing by 1
         with each new version
      -  registration date: date submitted to the IANA, using the format
         outlined in [ISO8601]:


   Declared registrant of the namespace:
      This includes:
         Registering organization
         Designated contact person
            Coordinates (at least one of: e-mail, phone, postal address)

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   Declaration of syntactic structure:

      This section 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 sections.  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

   Relevant ancillary documentation:

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

      Answers might include, but are not limited to:

      -  RFCs outlining syntax of the namespace
      -  Other of the defining community's (e.g., ISO) documents
         outlining syntax of the identifiers in the namespace
      -  Explanatory material introducing the namespace

   Identifier uniqueness considerations:

      This section 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:

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

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   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 section 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 algorithm
      -  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:

      If a namespace is intended to be accessible for global resolution,
      it must be registered in an RDS (Resolution Discovery System, see
      [RFC2276]) such as DDDS.  Resolution then proceeds according to
      standard URI resolution processes, and the mechanisms of the RDS.
      What this section 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

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   Rules for Lexical Equivalence:

      If there are particular algorithms for determining equivalence
      between two identifiers in the underlying namespace (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.

   Conformance with URN Syntax:

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

      For example, see the section on SICIs in [RFC2288].

   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

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      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


      This section should outline the scope of the use of the
      identifiers in this namespace.  Apart from considerations of
      private vs. public namespaces, this section is critical in
      evaluating the applicability of a requested NID.  For example, a
      namespace claiming to deal in "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".

Appendix B -- Illustration

B.1 Example Template

   The following example is provided for the purposes of illustrating
   the URN NID template described in Appendix A.  Although it is based
   on a hypothetical "generic Internet namespace" that has been
   discussed informally within the URN WG, there are still technical and
   infrastructural issues that would have to be resolved before such a
   namespace could be properly and completely described.

   Namespace ID:

      To be assigned

   Registration Information:

      Version 1
      Date: <when submitted>

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   Declared registrant of the namespace:

      Name:           Thinking Cat Enterprises
      Address:        1 ThinkingCat Way
                      Trupville, NewCountry
      Contact:           L. Daigle

   Declaration of structure:

      The identifier structure is as follows:

      URN:<assigned number>:<FQDN>:<assigned string>

      where FQDN is a fully-qualified domain name, and the assigned
      string is conformant to URN syntax requirements.

   Relevant ancillary documentation:

      Definition of domain names, found in:

      RFC 1035, November 1987.

   Identifier uniqueness considerations:

      Uniqueness is guaranteed as long as the assigned string is never
      reassigned for a given FQDN, and that the FQDN is never

      N.B.:  operationally, there is nothing that prevents a domain name
      from being reassigned;  indeed, it is not an uncommon occurrence.
      This is one of the reasons that this example makes a poor URN
      namespace in practice, and is therefore not seriously being
      proposed as it stands.

   Identifier persistence considerations:

      Persistence of identifiers is dependent upon suitable delegation
      of resolution at the level of "FQDN"s, and persistence of FQDN

      Same note as above.

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   Process of identifier assignment:

      Assignment of these URNs is delegated to individual domain name
      holders (for FQDNs).  The holder of the FQDN registration is
      required to maintain an entry (or delegate it) in the DDDS.
      Within each of these delegated name partitions, the string may be
      assigned per local requirements.

      e.g., urn:<assigned number>

   Process for identifier resolution:

      Domain name holders are responsible for operating or delegating
      resolution servers for the FQDN in which they have assigned URNs.

   Rules for Lexical Equivalence:

      FQDNs are case-insensitive.  Thus, the portion of the URN

                  urn:<assigned number>:<FQDN>:

      is case-insensitive for matches.  The remainder of the identifier
      must be considered case-sensitive.

   Conformance with URN Syntax:

      No special considerations.

   Validation mechanism:

      None specified.



B.2 Registration steps in practice

   The key steps for registration of informal or formal namespaces
   typically play out as follows:

   Informal NID:

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

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      2. Communicate the registration template to
         for technical review -- as a published I-D, or text e-mail
         message containing the template.

      3. Update the registration template as necessary from comments,
         and repeat steps 2 and 3 as necessary.

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

   Formal NID:

      1. Write an Internet-Draft describing the namespace and include
         the registration template, duly completed.  Be sure to include
         "Namespace Considerations", "Community Considerations" and
         "IANA Considerations" sections, as described in Section 4.3.

      2. Send the Internet-Draft to the I-D editor, and send a copy to for technical review.

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

      4. Send a request to the IESG to publish the I-D as an RFC.  The
         IESG may request further changes (published as I-D revisions)
         and/or direct discussion to designated working groups, area
         experts, etc.

      5. If the IESG approves the document for publication as an RFC,
         send a request to IANA to register the requested NID.

Appendix C -- Changes from RFC 2611

   This revision of [RFC2611] adds more detail describing the process of
   registering a URN namespace identifier (in terms of mechanical

   This version of the document also separates the process (mechanics)
   from the discussion of the requirements for namespaces, attempting to
   make the latter as objective as possible.

   Throughout the document, references have been updated to the current
   versions of the DDDS and related documentation (which collectively
   obsolete [RFC2168] and related drafts).

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C.1 Detailed Document Changes

   Added table of contents

   Section 2

   Clarified the definition of a URN namespace, the uniqueness of
   assignment, and that a single resource may have more than one
   identifier associated with it.

   Clarified the "number example" -- that the same string may appear in
   2 different namespaces, and be applied to different resources.
   Originally used ISBN/ISSN example, but structurally this is not

   Section 3 (new)

   This section explicitly defines the 3 categories of namespace --
   Experimental, Informal and Formal.  This section provides a
   description of the intended use of the different namespace types, as
   well as some acceptability guidelines for Formal namespaces (which
   require IETF review).

   Section 4.0

   Spelled out the name of RFC 2434 ("IANA Considerations").

   Provided a pointer to the IANA URN namespace registry.

   Sections 4.1-4.3

   New subsection divisions of the existing discussion of individual
   namespace types.

   Section 4.2

   Corrected reference to URN Syntax document (RFC 2141, not RFC 2168).

   Section 4.3

   Added clarifying text as to the intended nature of Formal namespaces
   and processes for registering them.

   Added text to describe the requirement for a "Namespace
   Considerations" section in RFCs defining Formal namespaces.  Defined
   the required content of that section.

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   Added text to describe the new requirement for a "Community
   Considerations" section in RFCs defining Formal namespaces.  Defined
   the required content of that section.

   Added text to explicitly call out the need for an "IANA
   Considerations" section in such RFCs, in order to alert IANA to
   required action.

   Added text to further clarify the (IETF) process for revising Formal
   namespace registrations through the RFC and IETF review process.

   Section 6

   New section -- added text to describe the IANA considerations for
   this document.

   Section 7 -- References

   Added references to revised NAPTR documentation ([RFC3401]), and the
   previous version of this document ([RFC2611]).

   Appendix A

   Section created by moving the "URN Namespace Definition Template"
   (RFC2611's Section 3) to an appendix.

   Added references to the new requirements for "Namespace
   Considerations", "Community Considerations", and "IANA
   Considerations" sections for Formal namespace registrations.

   Clarified the "Declared registrant of the namespace" template

   Added text to describe the purpose and scope of the "Validating

   Appendix B

   Section B.1 is the "example template" that was "Section 5" in RFC

   Update the sample "declared registrant" data per the changes to the
   template description.

   Removed the reference to "US-ASCII" in the "namespace specific
   string" of the example namespace.

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   Section B.2 (new)

   This added section is a step-by-step walkthrough of the process for
   registering Informal namespaces and Formal namespaces.

Authors' Addresses

   Leslie L. Daigle
   Thinking Cat Enterprises


   Dirk-Willem van Gulik
   WebWeaving Internet Engineering
   Nieuwsteeg 37A
   2311 RZ Leiden
   The Netherlands


   Renato Iannella
   IPR Systems Pty Ltd.


   Patrik Faltstrom
   Cisco Systems Inc
   170 W Tasman Drive SJ-13/2
   San Jose CA 95134


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