Network Working Group                                         D. Tessman
Request for Comments: 4198                                      Zelestra
Category: Informational                                    November 2005


    A Uniform Resource Name (URN) Namespace for Federated Content

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 (2005).

Abstract

  This document describes a URN (Uniform Resource Name) namespace for
  identifying content resources within federated content collections.
  A federated content collection often does not have a strong
  centralized authority but relies upon shared naming, metadata, and
  access conventions to provide interoperability among its members.

1.  Introduction

  Federated content collections are often loose constructs of both
  small and large content providers, with an active community, but
  without significant central authority.  Members are bound together by
  shared purpose and interoperate through shared naming, metadata, and
  access conventions.  Federations may also consist of other
  federations, creating complex associations and dependencies.

  A content provider may join or leave a federation at any time and may
  be part of more than one federation at the same time.  Content
  providers may also cease as organizations altogether, freeing their
  domain names for use by others.  In addition, content identifiers are
  spread throughout the members of a federation.  These identifiers are
  stored on various media, sometimes for long durations before being
  used.  Therefore, although they work well in situations without a
  strong content naming authority, URLs are insufficient as content
  identifiers within a federation because they cannot be uniquely and
  permanently tied to a specific content resource.







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  This URN namespace provides a mechanism whereby a central naming
  authority is not required.  Providers maintain naming authority over
  their own content within guidelines that guarantee URNs to be unique
  and permanent.

  A simple identifier resolution convention is also recommended to
  provide a consistent URN resolver interface across all providers.

  This namespace specification is for a formal namespace.

2.  Terminology

  In this document, the key words "MUST", "MUST NOT", "REQUIRED",
  "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
  and "OPTIONAL" are to be interpreted as described in RFC 2119 [1].

3.  Specification Template

  Namespace ID:

     "fdc"

  Registration Information:

     Registration Version Number: 1
     Registration Date: 2005-04-25

  Declared registrant of the namespace:

     Name:       Zelestra
     Address:    2314 Henrietta Avenue
                 La Crescenta, CA 91214-3007
                 USA

     Contact:    Dave Tessman
     E-mail:     [email protected]

  Declaration of syntactic structure:

     The NSS has the following ABNF [2] specification:

     NSS         = ProviderId ":" DateId ":" ResourceId
     ProviderId  = 1*(label ".") toplabel
     DateId      = (CCYY [MM [DD]]) / 1*3(DIGIT)
     ResourceId  = 1*(alphanum / other / ("%" hex hex))
     label       = alphanum / alphanum *(alphanum / "-") alphanum
     toplabel    = ALPHA / ALPHA *(alphanum / "-") alphanum
     CCYY        = 4(DIGIT)



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     MM          = ("0" %x31-39) / ("1" %x30-32)
     DD          = ("0" %x31-39) / (%x31-32 DIGIT) / "30" / "31"
     alphanum    = ALPHA / DIGIT
     hex         = DIGIT / %x41-46 / %x61-66
     other       = "(" / ")" / "+" / "," / "-" / "." / ":" / "=" /
                   "@" / ";" / "$" / "_" / "!" / "*" / "'"

     ProviderId is the content provider's identifier.  ProviderId MUST
     be an Internet domain name and MUST be owned by the organization
     creating the resource and allocating the URN to the resource.

     DateId is a date in ISO 8601 Basic Format (CCYY[MM[DD]]), and MUST
     correspond to a specific day on which the organization allocating
     the URN owned the domain name specified in the ProviderId.  If not
     included, the default value for MM and DD is "01".  DateIds of 1
     to 3 digits are reserved.

     ResourceId MUST be unique among all ResourceIds emanating from the
     same provider and having the same DateId.

  Relevant ancillary documentation:

     None.

  Identifier uniqueness considerations:

     The combination of ProviderId and DateId serves to uniquely
     identify the organization that is allocating the URN.  That
     organization is responsible for ensuring the uniqueness of the
     ResourceId.

  Identifier persistence considerations:

     A URN of this namespace may only be allocated by an organization
     that owns an Internet domain name.  The URN identifies a date on
     which the organization owned that domain name.  The combination of
     domain name and date will serve to uniquely identify that
     organization for all time.

  Process of identifier assignment:

    The organization identified by the ProviderId/DateId combination is
    responsible for allocating a ResourceId that is unique among all
    those that it allocates with that DateId.







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  Process of identifier resolution:

    Content providers are responsible for the provision of a URN
    resolution service, if any, for URNs they have assigned with a
    valid ProviderId/DateId combination.

    Content providers SHOULD support URN resolution by using the HTTP
    protocol convention described in RFC 2169 [3].  The ProviderId
    SHOULD be used as the HTTP server location.

  Rules for Lexical Equivalence:

     In addition to the rules defined in RFC 2141 [4], normalize the
     case of the ProviderId to lower case before comparison.

  Conformance with URN Syntax:

     There are no additional characters reserved.

  Validation mechanism:

     None additional to resolution specified.

  Scope:

     Global

4.  Examples

  The following examples are representative of URNs in this namespace,
  but may not refer to actual resources.

  urn:fdc:example.com:2002:A572007
  urn:fdc:example.net:200406:ivr:51089
  urn:fdc:example.org:20010527:img089322-038

5.  Security Considerations

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

6.  Namespace Considerations

  Distribution of naming authority, identifier flexibility, and a
  recommended URN resolution mechanism make this namespace a unique and
  valuable tool to meet the URN requirements of small content providers
  and federated content collections.




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7.  Community Considerations

  By establishing a simple, flexible, and efficient means for smaller
  content providers to uniquely identify and publish their content,
  this namespace reduces the effort required for these providers to
  participate in federated collections.  A consistent identifier format
  and resolution mechanism also increases the ability of federations to
  accept content references from smaller providers and to aggregate
  themselves into federations of federations.  Increased participation
  and aggregation results in a larger selection of distinctive content
  that is more accessible to the community.

  To make use of this namespace, a content provider should further
  decompose the ResourceId portion of the namespace syntactic structure
  to meet their internal content identification needs and establish an
  internal governance mechanism to ensure that all identifiers created
  follow the requirements of this namespace.  It is also recommended
  that the identifier resolution mechanism described in RFC 2169 [3] be
  provisioned within an HTTP server designated by the ProviderId
  portion of the namespace syntactic structure.

8.  IANA Considerations

  This document includes a URN NID registration that conforms to RFC
  3406 [5] and has been entered into the IANA registry of URN NIDs.

Normative References

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

  [2]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
       Specifications: ABNF", RFC 4234, October 2005.

  [3]  Daniel, R., "A Trivial Convention for using HTTP in URN
       Resolution", RFC 2169, June 1997.

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

Informative References

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







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Author's Address

  Dave Tessman
  Zelestra
  2314 Henrietta Avenue
  La Crescenta, California 91214-3007
  USA

  Phone: +1 818 249 8906
  EMail: [email protected]









































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Full Copyright Statement

  Copyright (C) The Internet Society (2005).

  This document is subject to the rights, licenses and restrictions
  contained in BCP 78, and except as set forth therein, the authors
  retain all their rights.

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Acknowledgement

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







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