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).
AbstractThis 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.
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. RFC 2119 . 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)
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.
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 . The ProviderId SHOULD be used as the HTTP server location. Rules for Lexical Equivalence: In addition to the rules defined in RFC 2141 , 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
RFC 2169  be provisioned within an HTTP server designated by the ProviderId portion of the namespace syntactic structure. RFC 3406  and has been entered into the IANA registry of URN NIDs.  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 4234, October 2005.  Daniel, R., "A Trivial Convention for using HTTP in URN Resolution", RFC 2169, June 1997.  Moats, R., "URN Syntax", RFC 2141, May 1997.  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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