draft-hadley-00.txt

Network Working Group                                   J. Gregorio, Ed.
Internet-Draft                                                       IBM
Expires: April 1, 2007                                    M. Hadley, Ed.
                                                        Sun Microsystems
                                                           M. Nottingham
                                                             Yahoo, Inc.
                                                              D. Orchard
                                                       BEA Systems, Inc.
                                                      September 28, 2006


                              URI Template
                         draft-gregorio-00.txt

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   URI Templates are URIs that contain embedded variables.  This
   document defines the structure and syntax of URI Templates and
   defines a corresponding XML simple type, the URITemplate, that may be



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   used to define elements and attributes that contain URI Templates.

Editorial Note

   To provide feedback on this Internet-Draft, ????.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Notational Conventions . . . . . . . . . . . . . . . . . . . .  3
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  URI Template . . . . . . . . . . . . . . . . . . . . . . . . .  3
     4.1   Template Variables . . . . . . . . . . . . . . . . . . . .  3
     4.2   Evaluating a URI Template  . . . . . . . . . . . . . . . .  4
     4.3   Examples . . . . . . . . . . . . . . . . . . . . . . . . .  4
   5.  URI Template Simple Profile  . . . . . . . . . . . . . . . . .  6
     5.1   Examples . . . . . . . . . . . . . . . . . . . . . . . . .  6
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   8.  Normative References . . . . . . . . . . . . . . . . . . . . .  8
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  8
   A.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . .  9
   B.  Revision History . . . . . . . . . . . . . . . . . . . . . . .  9
       Intellectual Property and Copyright Statements . . . . . . . . 10



























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1.  Introduction

   URI Templates are URIs that contain embedded variables.  This
   document defines the structure and syntax of URI Templates and
   defines a corresponding XML simple type, the URITemplate, that may be
   used to define elements and attributes that contain URI Templates.

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].

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.  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 / reserved /
             "|" / "^" / "<" / ">" / '"' / "\" /
             "`" / "%"

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




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   This specification uses the Augmented Backus-Naur Form (ABNF)
   notation of [RFC2234].  See [RFC3986] for reserved and unreserved
   productions.

   The range of characters allowed in template-name is large.  This was
   intentional as it is expected that follow-on specifications will
   create profiles of URI Templates that may restrict the characters
   allowed for either names or values, or give special meaning to some
   characters under particular applications or contexts.  For example,
   Section 5 defines a profile of URI Templates where any template-name
   that ends with a '?' is optional.

4.2  Evaluating a URI Template

   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
   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.

   If the value of a template variable contains characters outside the
   allowed set for the component of the URI that it parameterizes, such
   characters MUST be encoded as described in RFC 3986.

4.3  Examples

   Given the following template names and values










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       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
       !$&'()*+,;=:/?#[]@|^<>''\`          hello
       e
       ?                                   hullo

   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:

       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/{!$&'()*+,;=:/?#[]@|^<>''\`}
       http://example.com/hello

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

       http://example.com/{?}
       http://example.com/hullo

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




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   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.  URI Template Simple Profile

   This specification defines one profile for URI Templates that
   restricts the allowed set of characters in a template name and also
   defines special handling for the '?' character.  If a URI Template is
   specified as conforming to the Simple Profile then its template
   variables will match the production for simple-template-var.

    simple-template-char = unreserved
    simple-template-name = 1*a-template-char
    simple-template-var  = "{" template-name [ "?" ] "}"

   The optional trailing "?" is given a special significance.  If the
   template variable ends with "?" then the template variable is
   optional and the template processor need not supply a value for that
   variable during substitution.  If the template variable is not
   supplied then the template variable is substituted with a zero length
   string.  The trailing "?" is not considered part of the name of the
   template variable.

5.1  Examples

   Given the following names and values:

       Name                                Value
       ------------------------------------------------------------
       a                                   fred
       c                                   cheeseburger
       p                                   quote=to+bo+or+not+to+be
       e



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       -._~                                hello

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

   The following templates are taken as Simple Profile URI Templates.
   They will be expanded as shown:

       http://example.org/{a}/{c}/
       http://example.org/fred/cheeseburger/

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

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

       http://example.com/{-._~}
       http://example.com/hello

       http://example.com/{-._~}?
       http://example.com/hello?

       http://example.com/{-._~?}
       http://example.com/hello

       http://example.com/{wilma?}
       http://example.com/

       http://example.com/{wilma?}/
       http://example.com//

       http://example.com/{wilma?}?
       http://example.com/?

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

       http://example.com/{e?}/
       http://example.com//


6.  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.




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7.  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.

8.  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.


Authors' Addresses

   Joe Gregorio (editor)
   IBM

   Email: joe@bitworking.org
   URI:   http://ibm.com/


   Mark Hadley (editor)
   Sun Microsystems

   Email: Marc.Hadley@sun.com
   URI:   http://sun.com/


   Mark Nottingham
   Yahoo, Inc.

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








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   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

   Funding for the RFC Editor function is currently provided by the
   Internet Society.















































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