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Versions: 00 01 02 03 04 05 06 07 08 RFC 6570

Network Working Group                                   J. Gregorio, Ed.
Internet-Draft
Intended status: Standards Track                          M. Hadley, Ed.
Expires: January 10, 2008                               Sun Microsystems
                                                      M. Nottingham, Ed.

                                                              D. Orchard
                                                       BEA Systems, Inc.
                                                            July 9, 2007


                              URI Template
                     draft-gregorio-uritemplate-01

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   This Internet-Draft will expire on January 10, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   URI Templates are strings that can be transformed into URIs after
   embedded variables are substituted.  This document defines the syntax
   and processing 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.  URI Template  . . . . . . . . . . . . . . . . . . . . . . . . . 4
     3.1.  Template Variables  . . . . . . . . . . . . . . . . . . . . 4
     3.2.  URI Template Substitution . . . . . . . . . . . . . . . . . 4
     3.3.  Using URI Templates . . . . . . . . . . . . . . . . . . . . 5
       3.3.1.  Examples  . . . . . . . . . . . . . . . . . . . . . . . 5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 7
   Appendix A.  Contributors . . . . . . . . . . . . . . . . . . . . . 7
   Appendix B.  Revision History . . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7
   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 is 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 [RFC4234].  See [RFC3986] for the definitions of the URI-
   reference, reserved, and unreserved rules.




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3.  URI Template

   A URI Template is a sequence of characters that contains one or more
   embedded template variables, see Section 3.1.  A URI Template becomes
   a URI when the template variables are substituted with their values
   (see Section 3.2).  For example:

   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

3.1.  Template Variables

   Template variables are the parameterized components of a URI
   Template.  A template variable MUST match the template-var rule.

    template-char = unreserved
    template-name  = 1*template-char
    template-var  = "{" template-name "}"

3.2.  URI Template Substitution

   Evaluating a URI Template ("substitution") consists of replacing all
   template variables with their respective string values.

   During substitution, the string value of a template variable MUST
   have any characters that do not match the reserved or unreserved
   rules (i.e., those characters not legal in URIs without percent
   encoding) percent-encoded, as per [RFC3986], section 2.1.  Specific
   applications of URI Templates MAY specify additional constraints and
   encoding rules in addition to this.

   Any number of template variables MAY appear in a URI Template; a
   single template-name MAY appear multiple times.

   The result of substitution MUST match the URI-reference rule and
   SHOULD also match any known rules for the scheme of the resulting
   URI.

   Typically, this is ensured by the definitions of the template
   variables used.  For example, they may specify that a variable's
   value is not to contain certain characters, or that some characters
   should be percent-encoded before substitution.





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3.3.  Using URI Templates

   Applications using URI Templates will typically need to specify a
   number of things, including;

   o  The template to use.
   o  What template variables are available.
   o  For each of the variables;
      *  What characters are allowed in the template's value.
      *  What encodings should be applied to the value before
         substitutions.
      *  How to handle errors such as the output of substitution being
         an invalid URI.

   URI Template processors SHOULD allow applications to indicate that;

   o  A variable's value is required to contain at least one character
   o  A variable's value is required to match one of a set of supplied
      options
   o  A variable's value is to have all reserved characters, as per
      RFC3986, percent-escaped before substitution

   Processors MAY make additional options available.

3.3.1.  Examples

              Given the following template names and values:

                   +--------+--------------------------+
                   | Name   | Value                    |
                   +--------+--------------------------+
                   | a      | fred                     |
                   | b      | barney                   |
                   | c      | cheeseburger             |
                   | d      | one two three            |
                   | e      | 20% tricky               |
                   | f      |                          |
                   | 20     | this-is-spinal-tap       |
                   | scheme | https                    |
                   | p      | quote=to+be+or+not+to+be |
                   | q      | hullo#world              |
                   +--------+--------------------------+

                                  Table 1

   (Note that the name 'wilma' has not been defined, and the value of
   'f' is the empty string.)




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   The following URI Templates will be expanded as shown:

       http://example.org/page1#{a}
       http://example.org/page1#fred

       http://example.org/{a}/{b}/
       http://example.org/fred/barney/

       http://example.org/{a}{b}/
       http://example.org/fredbarney/

       http://example.com/order/{c}/{c}/{c}/
       http://example.com/order/cheeseburger/cheeseburger/cheeseburger/

       http://example.org/{d}
       http://example.org/one%20two%20three

       http://example.org/{e}
       http://example.org/20%25%20tricky

       http://example.com/{f}/
       http://example.com//

       {scheme}://{20}.example.org?date={wilma}&option={a}
       https://this-is-spinal-tap.example.org?date=&option=fred

       http://example.org?{p}
       http://example.org?quote=to+be+or+not+to+be

       http://example.com/{q}
       http://example.com/hullo#world


4.  Security Considerations

   A URI Template does not contain active or executable content.  Other
   security considerations are the same as those for URIs, see section 7
   of RFC3986.


5.  IANA Considerations

   In common with RFC3986, URI scheme names form a registered namespace
   that is managed by IANA according to the procedures defined in
   [RFC4395].  No IANA actions are required by this document.






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6.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC4234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 4234, October 2005.

   [RFC4395]  Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
              Registration Procedures for New URI Schemes", BCP 115,
              RFC 4395, February 2006.

   [1]  <http://lists.w3.org/Archives/Public/uri/>


Appendix A.  Contributors

   The following people made significant contributions to this
   specification: DeWitt Clinton and James Snell.


Appendix B.  Revision History

   01

   00 - Initial Revision.


Authors' Addresses

   Joe Gregorio (editor)

   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 (editor)

   Email: mnot@pobox.com
   URI:   http://mnot.net/


   David Orchard
   BEA Systems, Inc.

   Email: dorchard@bea.com
   URI:   http://bea.com/








































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