Network Working Group J. Gregorio, Ed.
Internet-Draft individual
Expires: May 1, 2007 M. Hadley, Ed.
Sun Microsystems
M. Nottingham
individual
D. Orchard
BEA Systems, Inc.
October 28, 2006
URI Template
draft-gregorio-uritemplate-00.txt
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Copyright (C) The Internet Society (2006).
Abstract
URI Templates are strings that can be transformed into URIs after
embedded variables are substituted. This document defines the
structure and syntax of URI Templates.
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Editorial Note
To provide feedback on this Internet-Draft, join the W3C URI mailing
list (http://lists.w3.org/Archives/Public/uri/) [1].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. URI Template . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1 Template Variables . . . . . . . . . . . . . . . . . . . . 4
4.2 URI Template Substitution . . . . . . . . . . . . . . . . 4
4.3 Examples . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 7
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 8
B. Revision History . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . 9
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1. Introduction
URI Templates are strings that contain embedded variables that are
transformed into URIs after embedded variables are substituted. This
document defines the structure and syntax of URI Templates.
URI Templates are useful when it's necessary to convey the structure
of a URI in a well-defined way. For example, documentation of an
interface exposed by a Web site might use a template to show people
how to find information about a user;
http://www.example.com/users/{userid}
URI Templates can also be thought of as the basis of a machine-
readable forms language; by allowing clients to form their own
identifiers based on templates given to them by the URI's authority,
it's possible to construct dynamic systems that use more of the URI
than traditional HTML forms are able to. For example,
http://www.example.org/products/{upc}/buyers?page={page_num}
Finally, URI Templates can be used to compose URI-centric protocols
without impinging on authorities' control of their URIs. For
example, there are many emerging conventions for passing around login
information between sites using URIs. Forcing people to use a well-
known query parameter isn't good practice, but using a URI parameter
allows different sites to specify local ways of conveying the same
information;
http://login.example.org/login?back={return-uri}
http://auth.example.com/userauth;{return-uri}
This specification defines the basic syntax and processing of URI
Templates. Each application of URI Templates will need to define its
own profile of this specification that indicates what template
variables are available, how to convey them to clients, and what
their appropriate use is in that context.
2. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
This specification uses the Augmented Backus-Naur Form (ABNF)
notation of [RFC2234]. See [RFC3986] for reserved and unreserved
productions.
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3. Motivation
URI Templates are useful in a number of scenarios including web
service documentation and application code. A standard syntax and
well-defined substitution rules will improve interop.
4. URI Template
A URI Template is a sequence of characters that contains one or more
embedded template variables Section 4.1. A URI Template becomes a
URI when the template variables are substituted with the template
variables string values, see Section 4.2. The following shows an
example URI Template:
http://example.com/widgets/{widget_id}
If the value of the widget_id variable is "xyzzy", the resulting URI
after substitution is:
http://example.com/widgets/xyzzy
4.1 Template Variables
Template variables are the parameterized components of a URI
Template, their representation is described below. A template
variable MUST match the template-var production.
template-char = unreserved
template-name = 1*template-char
template-var = "{" template-name "}"
4.2 URI Template Substitution
Evaluating a URI Template consists of replacing each occurrence of a
template variable with the string value of that variable. Obtaining
the string value of a template variable is an application-specific
process, this specification places no constraints on the mechanism
employed. Template variables MAY appear in a URI Template any number
of times.
If the value of a template variable would conflict with a reserved
character's purpose as a delimiter, then the conflicting data must be
percent-encoded before substitution. That is, merely doing rote
substitution on template variables could result in the generation of
an invalid URI for a particular scheme. Specifications that use URI
Templates are expected to take this into consideration in how they
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use such templates.
When the values of any template variables have been substituted into
a URI template, the resulting string MUST match the URI-reference
production of RFC 3986 and MUST also match the productions for the
scheme in the final URI.
This specification presumes that the value of a template variable
does not contain characters outside the allowed set for the
component(s) of the URI that it parameterizes.
4.3 Examples
Given the following template names and values
Name Value
------------------------------------------------------------
a fred
b barney
c cheeseburger
20 this-is-spinal-tap
a~b none%20of%20the%20above
schema https
p quote=to+bo+or+not+to+be
e
q hullo#world
Note that the name 'wilma' has not been defined, and the value of 'e'
is the empty string.
The following URI Templates will be expanded as shown:
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http://example.org/{a}/{b}/
http://example.org/fred/barney/
http://example.org/{a}{b}/
http://example.org/fredbarney/
http://example.org/page1#{a}
http://example.org/page1#fred
{scheme}://{20}.example.org?date={wilma}&option={a}
https://this-is-spinal-tap.example.org?date=&option=fred
http://example.org/{a~b}
http://example.org/none%20of%20the%20above
http://example.org?{p}
http://example.org?quote=to+bo+or+not+to+be
http://example.com/order/{c}/{c}/{c}/
http://example.com/order/cheeseburger/cheeseburger/cheeseburger/
http://example.com/{q}
http://example.com/hullo#world
http://example.com/{e}/
http://example.com//
The following are examples of URI Template expansions that are not
legal.
Name Value
------------------------------------------------------------
a fred barney
b %
The following URI Templates are expanded with the given values and do
not produce legal URIs.
http://example.org/{a}
http://example.org/fred barney
http://example.org/{b}/
http://example.org/%/
5. Security Considerations
A URI Template does not contain active or executable content. Other
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security considerations are the same as those for URIs, see section 7
of RFC3986.
6. IANA Considerations
In common with RFC3986, URI scheme names form a registered namespace
that is managed by IANA according to the procedures defined in
[RFC2717]. No IANA actions are required by this document.
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2717] Petke, R. and I. King, "Registration Procedures for URL
Scheme Names", BCP 35, RFC 2717, November 1999.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[1] <http://lists.w3.org/Archives/Public/uri/>
Authors' Addresses
Joe Gregorio (editor)
individual
Email: joe@bitworking.org
URI: http://bitworking.org/
Marc Hadley (editor)
Sun Microsystems
Email: Marc.Hadley@sun.com
URI: http://sun.com/
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Mark Nottingham
individual
Email: mnot@pobox.com
URI: http://mnot.net/
David Orchard
BEA Systems, Inc.
Email: dorchard@bea.com
URI: http://bea.com/
Appendix A. Contributors
The following people made significant contributions to this
specification: DeWitt Clinton and James Snell.
Appendix B. Revision History
00 - Initial Revision.
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Acknowledgment
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