Network Working Group P. Stickler
Internet-Draft Nokia Research Center
Expires: July 17, 2002 January 16, 2002
The 'uri:' URI Scheme for URI Reification
draft-pstickler-uri-00
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document describes the 'uri:' Uniform Resource Identifier (URI)
scheme for the reification of arbitrary Uniform Resource Identifiers.
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. BNF for the 'uri:' URI Scheme . . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
References . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 6
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1. Overview
The 'uri:' URI scheme is intended to provide a simple but consistent
means by which URIs (including URI References) may be reified for the
sake of communication between web applications about the URIs
themselves rather than about the resources they may represent.
The ability to differentiate between a particular URI and the web
resource which that URI denotes or represents is important in cases
where we need to make statements about the history, nature, or other
characteristics of the URI itself which are not properties of the
resource which it represents -- such as when the URI was minted, by
whom, and the class of URI to which it belongs.
Examples:
uri:http://www.nokia.com
uri:mailto:patrick.stickler@nokia.com
uri:http://www.abc.com/employees#Bob
uri:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6
uri:voc://nokia.com/MARS-2.2/title
uri:ftp://ftp.abc.com/pub/apps/free
uri:uri:http://www.nokia.com
These examples are provided for illustrative purposes only and do not
necessarily constitute actual URIs. See the BNF definition below for
an explicit definition of 'uri:' URI syntax.
Note that this mechanism of reification is infinitely recursive,
allowing instances of this URI scheme to themselves be reified by
additional encapsulation, as the final example above illustrates.
Clearly, the utility of such recursion diminishes greatly with each
level of encapsulation, but the absence of a finite boundary ensures
that all possible URIs, including instances of this URI scheme, can
be reified as needed.
The 'uri:' URI scheme belongs to the class of URIs known as Uniform
Resource Values (URV) which are themselves a subclass of Uniform
Resource Primitives (URP), a class of URI which constitutes a
"WYSIWYG" URI, one which is not dereferencible to and does not denote
another web resource, but constitutes a self-contained resource where
the full realization of that resource is expressed in the URI itself.
For a full discussion of the properties of URPs and URVs, please see
[1]. Familiarity with the concepts defined therein will facilitate
the full understanding of this document.
Because a URP is not dereferencible, and hence does not permit the
suffixation of a fragment identifier (there is no such thing as a URP
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Reference), it is not necessary to escape any hash marks '#'
occurring in a URI Reference reified by a 'uri:' URI.
2. BNF for the 'uri:' URI Scheme
This is a BNF-like description of the 'uri:' Uniform Resource
Identifier syntax, using the conventions of RFC 822[2], except that
"|" is used to designate alternatives, and brackets [] are used
around optional or repeated elements. Briefly, literals are quoted
with "", optional elements are enclosed in [brackets], and elements
may be preceded with <n>* to designate n or more repetitions of the
following element; n defaults to 0.
This BNF description adopts sub-definitions defined in RFC 2396
"Uniform Resource Identifiers (URI): Generic Syntax" [3] which are
not repeated here.
uri-URI = "uri:" absoluteURI [ "#" fragment ]
absoluteURI = <as defined by RFC 2396>
fragment = <as defined by RFC 2396>
Note that the URI scheme prefix "uri:" is considered to be a valid
URI denoting this URI scheme, though it is not itself a valid URI
according to this URI scheme.
3. Security Considerations
This document raises no known security issues.
References
[1] Stickler, P., "An Extended Class Taxonomy of Uniform Resource
Identifier Schemes", January 2002, <http://www-nrc.nokia.com/sw/
draft-pstickler-uri-taxonomy-00.html>.
[2] Crocker, D., "STANDARD FOR THE FORMAT OF ARPA INTERNET TEXT
MESSAGES", RFC 822, August 1982.
[3] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
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Author's Address
Patrick Stickler
Nokia Research Center
Visiokatu 1
Tampere 33720
FI
EMail: patrick.stickler@nokia.com
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