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RFC 3613 - Definition of a Uniform Resource Name (URN) Namespace


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Network Working Group                                          R. Morgan
Request for Comments: 3613                           Univ. of Washington
Category: Informational                                      K. Hazelton
                                              Univ. of Wisconsin-Madison
                                                            October 2003

     Definition of a Uniform Resource Name (URN) Namespace for the
         Middleware Architecture Committee for Education (MACE)

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   This document describes a Uniform Resource Name (URN) namespace for
   the Internet2 Middleware Architecture Committee for Education (MACE).
   This namespace is for naming persistent resources defined by MACE,
   its working groups and other designated subordinates.

1.  Introduction and Community Considerations

   The Internet2 Middleware Architecture Committee for Education (MACE)
   produces many kinds of documents: specifications, working drafts,
   object classes, schemas, stylesheets, etc.  It also defines directory
   attributes and controlled vocabularies for the values of some of
   those attributes.

   MACE wishes to provide global, distributed, persistent, location-
   independent names for these resources.  The Uniform Resource Name
   (URN) variant of URIs meets these requirements.

   MACE working groups and other MACE-affiliated groups will benefit
   from the MACE URN namespace by having an easy, efficient way to
   assign globally unique, persistent identifiers to resources that they
   create.  The nature of MACE work is that serves the needs of one or
   more communities of interest.  A namespace managed so as to
   facilitate the creation, registration and resolution of unique,
   persistent identifiers will be of great value for MACE, its
   affiliates and the higher education community generally.

   This URN namespace specification is for a formal namespace.

2.  Specification Template

   Namespace ID:

      "mace"

   Registration Information:

      Registration Version Number 1

      Registration Date: 2003-08-01

   Registrant of the namespace:

      Middleware Architecture Committee for Education (MACE)
      ATTN: Lisa Hogeboom
      Internet2
      3025 Boardwalk  Suite 200
      Ann Arbor, MI 48108

      Phone: +1 734 913 4250

      Contact: Keith Hazelton

      Affiliation: Univ.  of Wisconsin-Madison
      1210 W.  Dayton St.
      Madison, WI  53706
      Phone: +1 608 262 0771

      hazelton@doit.wisc.edu

   Syntactic structure:

      The Namespace Specific Strings (NSS) of all URNs assigned by MACE
      will conform to the syntax defined in section 2.2 of RFC 2141,
      "URN Syntax" [1].  In addition, all MACE URN NSSs will consist of
      a left-to-right series of tokens delimited by colons.  The left-
      to-right sequence of colon-delimited tokens corresponds to
      descending nodes in a tree.  To the right of the lowest naming
      authority node there may be zero, one or more levels of
      hierarchical naming nodes terminating in a rightmost leaf node.
      See the section entitled "Identifier assignment" below for more on
      the semantics of NSSs.  This syntax convention is captured in the
      following normative ABNF rules for MACE NSSs (see RFC 2234) [2]:

      MACE-NSS        =   1*(subStChar) 0*(":" 1*(subStChar))

      subStChar       =   trans / "%" HEXDIG HEXDIG

      trans           =   ALPHA / DIGIT / other / reserved

      other           =   "(" / ")" / "+" / "," / "-" / "." /

                           "=" / "@" / ";" / "$" /

                           "_" / "!" / "*" / "'"

      reserved        =   "%" / "/" / "?" / "#"

      The exclusion of the colon from the list of "other" characters
      means that the colon can only occur as a delimiter between string
      tokens.  Note that this ABNF rule set guarantees that any valid
      MACE NSS is also a valid RFC 2141 NSS.

   Relevant ancillary documentation:

      None.

   Identifier uniqueness:

      It is the responsibility of MACE directors to guarantee uniqueness
      of the names of immediately subordinate naming authorities.  Each
      lower-level naming authority in turn inherits the responsibility
      of guaranteeing uniqueness of names in their branch of the naming
      tree.

   Identifier persistence:

      MACE directors bear ultimate responsibility for maintaining the
      usability of MACE URNs over time.  This responsibility may be
      delegated to subordinate naming authorities per the discussion in
      the section below on identifier assignment.  That section provides
      a mechanism for the delegation to be revoked in case a subordinate
      naming authority ceases to function.

   Identifier assignment:

      MACE directors will create an initial series of immediately
      subordinate naming authorities, and will define a process for
      adding to that list of authorities.  Each top-level working group
      of MACE will be invited to designate a naming authority and to
      suggest one or more candidate names for that authority.  The
      MACE-Shibboleth group, for example, might propose creating a

      naming authority under "urn:mace:shib," "urn:mace:shibboleth" or
      some other name.

      Institutions and communities affiliated with MACE may request,
      through their designated MACE liaison, that they be granted MACE-
      subordinate naming authority status.  They may propose candidate
      names for that authority.  One way for such entities to guarantee
      uniqueness of their proposed name is to base it on a DNS name.
      That is, if Georgetown University wished to be designated a
      subordinate naming authority under MACE, the institutional MACE
      liaison could propose to MACE directors that they be delegated
      control over names beginning with "urn:mace:georgetown.edu".
      Institutions seeking affiliation with MACE should send email to
      mace-submit@internet2.edu, nominating an institutional liaison and
      providing contact information for that person.

      On at least an annual basis, MACE directors will contact the
      liaisons or directors of each immediately subordinate naming
      authority.  If there is no response, or if the respondent
      indicates that they wish to relinquish naming authority, the
      authority over that branch of the tree reverts to MACE.  This
      process will be enforced recursively by each naming authority on
      its subordinates.  This process guarantees that responsibility for
      each branch of the tree will lapse for less than one year at worst
      before being reclaimed by a superior authority.

      Lexical equivalence of two MACE namespace specific strings (NSSs)
      is defined below as an exact, case-sensitive string match.  MACE
      will assign names of immediately subordinate naming authorities in
      a case-insensitive fashion, so that there will not be two MACE-
      subordinate naming authorities whose names differ only in case.

   Identifier resolution:

      MACE directors will maintain an index of all MACE and MACE
      workgroup assigned URNs at the web site
      http://middleware.internet2.edu/urn-mace/urn-mace.html.  That
      index will map URNs to resource identifiers or resource
      specifications (e.g., protocol parameters).  MACE-affiliated
      naming authorities will specify how to resolve the URNs they
      assign if they are resolvable.

   Lexical equivalence:

      Lexical equivalence of two MACE namespace specific strings (NSSs)
      is defined as an exact, case-sensitive string match.

   Conformance with URN syntax:

      All MACE NSSs fully conform to RFC 2141 syntax rules for NSSs.

   Validation mechanism:

      As specified in the "Identifier resolution" section above, MACE
      directors will maintain an index of all MACE and MACE workgroup
      assigned URNs on its web site,
      http://middleware.internet2.edu/urn-mace/urn-mace.html.  Presence
      in that index implies that a given URN is valid.  MACE-affiliated
      naming authorities will specify how to validate the URNs they
      assign.

   Scope:

      Global.

3. Security Considerations

   There are no additional security considerations beyond those normally
   associated with the use and resolution of URNs in general.

4.  Namespace Considerations

   Registration of an NID specific to MACE is reasonable given the
   following considerations:

   1. MACE would like to assign URNs to some very fine-grained objects
      (such as specific controlled vocabulary values of an attribute in
      MACE-defined LDAP object classes).  This does not seem to be the
      primary intended use of the XMLORG namespace (RFC 3120) [3], let
      alone the more tightly controlled OASIS namespace (RFC 3121) [4].

   2. MACE seeks naming autonomy.  We understand that the XMLORG
      registrants left the door open to subordinate naming authorities,
      "OASIS may assign portions of its XMLORG namespace for assignment
      by other parties" (RFC 3120) [3], but there is no specified
      process for such assignment.  That would in any case mean having a
      fixed XMLORG-assigned prefix on every single object to which we
      assign a URN.  MACE has a number of active work groups that may
      well generate a growing number of subordinate naming authorities.
      Moreover, MACE is not a member of OASIS, so becoming a subordinate
      naming authority under the OASIS URN space is currently not an
      option.

   3. MACE will want to assign URNs to non-XML objects as well.  That is
      another reason that XMLORG may not be an appropriate higher-level
      naming authority for MACE.

   Some MACE-developed schema and namespaces may be good candidates for
   inclusion in the XMLORG registry.  The fact that such an object might
   already have a MACE-assigned URN shouldn't be a hindrance.  Work is
   in progress to update RFC 2611 [5], which includes an explicit
   statement that two or more URNs may point to the same resource.  A
   resource with a MACE-assigned namespace-specific-string would, of
   course, be given an XMLORG namespace-specific-string at the time it
   enters the XMLORG registry.

5.  IANA Considerations

   The IANA has formally registered URN namespace 13 to MACE, within the
   IANA registry of URN NIDs.

6.  Normative References

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

   [2]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
        Specifications: ABNF", RFC 2234, November 1997.

   [3]  Best, K. and N. Walsh, "A URN Namespace for XML.org", RFC 3120,
        June 2001.

   [4]  Best, K. and N. Walsh, "A URN Namespace for OASIS", RFC 3121,
        June 2001.

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

7.  Authors' Addresses

   RL "Bob" Morgan
   4545 15th Ave. NE
   Seattle, WA  98105
   U.S.A.

   EMail: rlmorgan@washington.edu

   Keith D. Hazelton
   University of Wisconsin-Madison
   1210 W. Dayton St.
   Madison, WI  53706
   U.S.A.

   EMail: hazelton@doit.wisc.edu

8.  Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
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   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
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   The limited permissions granted above are perpetual and will not be
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   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.

 

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