Report from the Joint W3C/IETF URI Planning Interest Group: Uniform Resource Identifiers (URIs), URLs, and Uniform Resource Names (URNs): Clarifications and Recommendations
RFC 3305

Document Type RFC - Informational (August 2002; Errata)
Last updated 2015-10-14
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Network Working Group                                   M. Mealling, Ed.
Request for Comments: 3305                             R. Denenberg, Ed.
Category: Informational                           W3C URI Interest Group
                                                             August 2002

      Report from the Joint W3C/IETF URI Planning Interest Group:
 Uniform Resource Identifiers (URIs), URLs, and Uniform Resource Names
              (URNs): Clarifications and Recommendations

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 (2002).  All Rights Reserved.

Abstract

   This document, a product of the W3C Uniform Resource Identifier (URI)
   Interest Group, addresses and attempts to clarify issues pertaining
   to URIs.  This document addresses how URI space is partitioned and
   the relationship between URIs, URLs, and URNs, describes how URI
   schemes and URN namespaces ids are registered, and presents
   recommendations for continued work on this subject.

Mealling & Denenberg         Informational                      [Page 1]
RFC 3305                  URIs, URLs, and URNs               August 2002

Table of Contents

   1.      The W3C URI Interest Group . . . . . . . . . . . . . . . .  2
   2.      URI Partitioning . . . . . . . . . . . . . . . . . . . . .  2
   2.1     Classical View . . . . . . . . . . . . . . . . . . . . . .  3
   2.2     Contemporary View  . . . . . . . . . . . . . . . . . . . .  3
   2.3     Confusion  . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.      Registration . . . . . . . . . . . . . . . . . . . . . . .  4
   3.1     URI Schemes  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.1.1   Registered URI schemes . . . . . . . . . . . . . . . . . .  4
   3.1.2   Unregistered URI Schemes . . . . . . . . . . . . . . . . .  4
   3.1.2.1 Public Unregistered Schemes  . . . . . . . . . . . . . . .  4
   3.1.2.2 Private Schemes  . . . . . . . . . . . . . . . . . . . . .  5
   3.1.3   Registration of URI Schemes  . . . . . . . . . . . . . . .  5
   3.1.3.1 IETF Tree  . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.1.3.2 Other Trees  . . . . . . . . . . . . . . . . . . . . . . .  5
   3.2     URN Namespaces . . . . . . . . . . . . . . . . . . . . . .  5
   3.2.1   Registered URN NIDs  . . . . . . . . . . . . . . . . . . .  5
   3.2.2   Pending URN NIDs . . . . . . . . . . . . . . . . . . . . .  6
   3.2.3   Unregistered NIDs  . . . . . . . . . . . . . . . . . . . .  7
   3.2.4   Registration Procedures for URN NIDs . . . . . . . . . . .  7
   4.      Additional URI Issues  . . . . . . . . . . . . . . . . . .  7
   5.      Recommendations  . . . . . . . . . . . . . . . . . . . . .  8
   6.      Security Considerations  . . . . . . . . . . . . . . . . .  8
   7.      Acknowledgements . . . . . . . . . . . . . . . . . . . . .  8
           References . . . . . . . . . . . . . . . . . . . . . . . .  9
           Authors' Addresses . . . . . . . . . . . . . . . . . . . . 10
           Full Copyright Statement . . . . . . . . . . . . . . . . . 11

1. The W3C URI Interest Group

   In October, 2000 the W3C formed a planning group whose mission was to
   evaluate the opportunities for W3C work in the area of Uniform
   Resource Identifiers (URIs) and to develop a proposal for continued
   work in this area.  The Interest Group was composed of W3C members
   and invited experts from the IETF to participate as well.  This
   document is a set of recommendations from this group, to the W3C and
   the IETF for work that can and should continue in this area.

2. URI Partitioning

   There is some confusion in the web community over the partitioning of
   URI space, specifically, the relationship among the concepts of URL,
   URN, and URI.  The confusion owes to the incompatibility between two
   different views of URI partitioning, which we call the "classical"
   and "contemporary" views.

Mealling & Denenberg         Informational                      [Page 2]
RFC 3305                  URIs, URLs, and URNs               August 2002

2.1 Classical View

   During the early years of discussion of web identifiers (early to mid
   90s), people assumed that an identifier type would be cast into one
   of two (or possibly more) classes.  An identifier might specify the
   location of a resource (a URL) or its name (a URN), independent of
   location.  Thus a URI was either a URL or a URN.  There was
   discussion about generalizing this by the addition of a discrete
   number of additional classes; for example, a URI might point to
   metadata rather than the resource itself, in which case the URI would
   be a URC (citation).  URI space was thus viewed as partitioned into
   subspaces:  URL, URN, and additional subspaces to be defined.  The
   only such additional space ever proposed was Uniform Resource
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