Network Working Group                                     T. Berners-Lee
Request for Comments: 1630                                          CERN
Category: Informational                                        June 1994


                 Universal Resource Identifiers in WWW

                A Unifying Syntax for the Expression of
             Names and Addresses of Objects on the Network
                     as used in the World-Wide Web

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

IESG Note:

   Note that the work contained in this memo does not describe an
   Internet standard.  An Internet standard for general Resource
   Identifiers is under development within the IETF.

Introduction

   This document defines the syntax used by the World-Wide Web
   initiative to encode the names and addresses of objects on the
   Internet.  The web is considered to include objects accessed using an
   extendable number of protocols, existing, invented for the web
   itself, or to be invented in the future.  Access instructions for an
   individual object under a given protocol are encoded into forms of
   address string.  Other protocols allow the use of object names of
   various forms.  In order to abstract the idea of a generic object,
   the web needs the concepts of the universal set of objects, and of
   the universal set of names or addresses of objects.

   A Universal Resource Identifier (URI) is a member of this universal
   set of names in registered name spaces and addresses referring to
   registered protocols or name spaces.  A Uniform Resource Locator
   (URL), defined elsewhere, is a form of URI which expresses an address
   which maps onto an access algorithm using network protocols. Existing
   URI schemes which correspond to the (still mutating) concept of IETF
   URLs are listed here. The Uniform Resource Name (URN) debate attempts
   to define a name space (and presumably resolution protocols) for
   persistent object names. This area is not addressed by this document,
   which is written in order to document existing practice and provide a
   reference point for URL and URN discussions.





 
RFC 1630                      URIs in WWW                      June 1994


   The world-wide web protocols are discussed on the mailing list www-
   talk-request@info.cern.ch and the newsgroup comp.infosystems.www is
   preferable for beginner's questions. The mailing list uri-
   request@bunyip.com has discussion related particularly to the URI
   issue.  The author may be contacted as timbl@info.cern.ch.

   This document is available in hypertext form at:

   http://info.cern.ch/hypertext/WWW/Addressing/URL/URI_Overview.html

The Need For a Universal Syntax

   This section describes the concept of the URI and does not form part
   of the specification.

   Many protocols and systems for document search and retrieval are
   currently in use, and many more protocols or refinements of existing
   protocols are to be expected in a field whose expansion is explosive.

   These systems are aiming to achieve global search and readership of
   documents across differing computing platforms, and despite a
   plethora of protocols and data formats.  As protocols evolve,
   gateways can allow global access to remain possible. As data formats
   evolve, format conversion programs can preserve global access.  There
   is one area, however, in which it is impractical to make conversions,
   and that is in the names and addresses used to identify objects.
   This is because names and addresses of objects are passed on in so
   many ways, from the backs of envelopes to hypertext objects, and may
   have a long life.

   A common feature of almost all the data models of past and proposed
   systems is something which can be mapped onto a concept of "object"
   and some kind of name, address, or identifier for that object.  One
   can therefore define a set of name spaces in which these objects can
   be said to exist.

   Practical systems need to access and mix objects which are part of
   different existing and proposed systems.  Therefore, the concept of