Network Working Group M. Mealling Request for Comments: 3622 VeriSign, Inc. Category: Informational February 2004 A Uniform Resource Name (URN) Namespace for the Liberty Alliance Project 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 (2004). All Rights Reserved.
AbstractThis document describes a Uniform Resource Name (URN) namespace that will identify various objects within the Liberty Architecture for federated network identity. 5], and specifically, XML Schema  and Namespaces . These components require identifiers that will live far beyond the lifetime of the organization that produced them. As such, a URN namespace for those components that adheres to the assumptions and policies of the Liberty specification is required. This namespace specification is for a formal namespace.
section 2.2 of RFC 2141 . In addition, all Liberty 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 (although not in the RFC 2396  sense of 'hierarchy') 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 Liberty NSSs: Liberty-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 Liberty NSS is also a valid RFC 2141 NSS. For example: urn:liberty:schemas:authctx:2002:05 urn:liberty:schemas:core:2002:12 Relevant ancillary documentation: Liberty Architecture Overview  Version 1.1 Liberty Alliance Project January 15, 2003 Identifier uniqueness considerations: Identifiers are assigned by the Liberty Project within its various standards. In the process of publishing a specification all newly minted names are checked against the record of previously assigned names. Identifier persistence considerations: The assignment process guarantees that names are not reassigned and that the binding between the name and its resource is permanent, regardless of any standards or organizational changes. Process of identifier assignment: Names are assigned by the Liberty standards publication process. Process of identifier resolution: At this time no resolution mechanism is specified. Rules for Lexical Equivalence: Lexical equivalence of two Liberty namespace specific strings (NSSs) is defined as an exact, case-sensitive string match. The Liberty Alliance will assign names of immediately subordinate
naming authorities in a case-insensitive fashion, so that there will not be two Liberty-subordinate naming authorities whose names differ only in case. Conformance with URN Syntax: There are no additional characters reserved. Validation mechanism: None other than verifying with the correct Liberty specifications. Scope: Global
 Moats, R., "URN Syntax", RFC 2141, May 1997.  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998.  Hodges, J. and T. Watson, "Liberty Architecture Overview", Liberty 1.1, January 2003, <http://www.projectliberty.org/specs/liberty-architecture- overview-v1.1.pdf>.  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997.  Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, "Extensible Markup Language (XML) 1.0 (2nd ed)", W3C REC-xml, October 2000, <http://www.w3.org/TR/REC-xml>.  Bray, T., Hollander, D. and A. Layman, "Namespaces in XML", W3C REC-xml-names, January 1999, <http://www.w3.org/TR/REC-xml- names>.  Thompson, H., Beech, D., Maloney, M. and N. Mendelsohn, "XML Schema Part 1: Structures", W3C REC-xmlschema-1, May 2001, <http://www.w3.org/TR/xmlschema-1/>.
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