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: dtessman@zelestra.com
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: dtessman@zelestra.com
Tessman Informational [Page 6]
RFC 4198 URN Namespace for Federated Content November 2005
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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