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.
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.
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-
firstname.lastname@example.org and the newsgroup comp.infosystems.www is
preferable for beginner's questions. The mailing list uri-
email@example.com has discussion related particularly to the URI
issue. The author may be contacted as firstname.lastname@example.org.
This document is available in hypertext form at:
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