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Network Working Group                                           J. Snell
Internet-Draft                                               May 6, 2007
Intended status: Standards Track
Expires: November 7, 2007


              Atom Publishing Protocol Features Extension
                   draft-snell-atompub-feature-03.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   This Internet-Draft will expire on November 7, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document introduces extensions to the Atom Publishing Protocol
   introspection format for expressing metadata about the behaviors,
   functions and capabilities supported by an Atom Publishing Protocol
   server implementation.







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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Notational Conventions . . . . . . . . . . . . . . . . . . . .  3
   3.  The 'f:feature' element  . . . . . . . . . . . . . . . . . . .  3
     3.1.  Example  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  5
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  5
     5.1.  Registry of Atom Publishing Features . . . . . . . . . . .  5
       5.1.1.  Initial Assignments  . . . . . . . . . . . . . . . . .  6
   6.  Normative References . . . . . . . . . . . . . . . . . . . . . 12
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 13
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
   Intellectual Property and Copyright Statements . . . . . . . . . . 14





































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1.  Introduction

   This document introduces extensions for the Atom Publishing Protocol
   introspection format for expressing metadata about the behaviors,
   functions and capabilities supported by an Atom Publishing Protocol
   server implementation.


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 BCP 14, [RFC2119].

   This specification uses XML Namespaces [W3C.REC-xml-names-19990114]
   to uniquely identify XML element names.  It uses the following
   namespace prefix for the indicated namespace URI;

     "f": "http://purl.org/atompub/features/1.0"

   This specification uses terms from the XML Infoset
   [W3C.REC-xml-infoset-20040204].  However, this specification uses a
   shorthand; the phrase "Information Item" is omitted when naming
   Element Information Items.  Therefore, when this specification uses
   the terms "element" and "attribute" it is referring, respectively, to
   the Element and Attribute Information Items in Infoset terms.


3.  The 'f:feature' element

   A feature is an abstract behavior, function and capability supported
   by an Atom Publishing Protocol server.  Examples of features that
   might be supported by an APP server include support for draft
   entries, scheduled publication of entries, use of a particular set of
   Atom format extensions, use of a particular authentication scheme,
   and so on.  The presence of a f:feature element in an app:collection
   element is an indication that the collection supports the feature
   specified and may require that a client wishing to use the endpoint
   use that feature.  Features are identified using permanent,
   universally unique IRI's.

     feature = element f:feature {
       atomCommonAttributes,
       attribute ref { atomUri },
       attribute required { 'yes' | 'no' }?,
       attribute href { atomURI }?,
       attribute label { text }?,
       (extensionElement*)



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     }

   The "ref" attribute specifies an globally unique IRI identifying a
   feature supported by a collection.  The value of the ref attribute
   MUST be compared on a case-sensitive, character-by-character basis.
   Relative references MUST NOT be used.

   A 'required' attribute value of "yes" indicates that clients MUST
   utilize the identified feature when interacting with the collection.
   A server MAY reject requests from clients that do not support or use
   the feature.  If not specified, the value is assumed to be "no".

   An optional 'href' attribute MAY be used to specify the URI of a
   human-readable description of the feature.  Relative references MAY
   be used.

   The optional 'label' attribute MAY be used to specify a human-
   readable label for the feature.  The value of the 'label' attribute
   is Language-Sensitive as defined by Section 2 of [RFC4287].

   The f:feature element MAY contain child elements and attributes other
   than those defined in this specification.  Such "foreign markup" are
   considered to be metadata applicable to the feature identified by the
   f:feature element.  Software agents MUST NOT stop processing or
   signal an error or change their behavior as a result of encountering
   such foreign markup.

   An app:collection element MAY contain zero or more f:feature elements
   but MUST NOT contain more than one with the same ref attribute value.
   The order in which f:feature elements appears is insignificant.





















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3.1.  Example

   The following is an example of a collection supporting one
   hypothetical required feature and a number of optional features.

  <service xmlns="...">
    <workspace title="My Atom Service">
      <collection title="My Atom Collection" href="...">
        ...
        <f:feature ref="http://purl.org/atom/app#drafts" />
        <f:feature ref="http://purl.org/atom/app#xhtml-content" />
        <f:feature ref="http://purl.org/atom/app#preserve-extensions" />
        <f:feature ref="http://purl.org/syndication/thread/1.0" />
        <f:feature ref="http://code.google.com/apis/gdata/GoogleLogin"
          href="http://code.google.com/apis/gdata/"
          label="Google Login"
          required="yes" />
      </collection>
    </workspace>
  </app:server>


4.  Security Considerations

   Specific features supported by a collection may introduce security
   considerations and concerns beyond those discussed by the Atom
   Publishing Protocol and Atom Syndication Format specifications.
   Implementors must refer to the specifications and description of each
   feature to determine the security considerations relevant to each.


5.  IANA Considerations

5.1.  Registry of Atom Publishing Features

   The Registry of Atom Publishing Features is maintained by IANA and
   contains information about known features that can be supported by
   Atom Publishing Protocol implementations.  New assignments are
   subject to IESG approval, as outlined in [RFC2434].  Requests should
   be made by email to IANA, which will then forward the request to the
   IESG, requesting approval.  The request should use the following
   template:

   o  Ref: (A globally unique IRI identifying the feature)
   o  Label: (A human-readable label for the feature)
   o  Description: (A human-readable description of the feature)





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   o  Href: (A URI referencing a document containing a detailed
      definition of the feature)
   o  Security Considerations:

5.1.1.  Initial Assignments

   The Registry of Features initially contains the following
   assignments:

5.1.1.1.  Drafts - http://purl.org/atom/app#drafts

   o  Ref: http://purl.org/atom/app#drafts
   o  Label: Drafts
   o  Description: The "Drafts" feature indicates that a collection
      supports the use of the app:draft control element as defined in
      section 13.1.1 of [I-D.ietf-atompub-protocol].
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.2.  Preserve Entries - http://purl.org/atom/app#preserve-entry

   o  Ref: http://purl.org/atom/app#preserve-entry
   o  Label: Preserve Entries
   o  Description: The "Preserve Entries" feature indicates that a
      server will preserve the semantic content of entries POST and PUT
      to the collection without making any modifications.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.3.  Preserve IDs - http://purl.org/atom/app#preserve-id

   o  Ref: http://purl.org/atom/app#preserve-id
   o  Label: Preserve IDs
   o  Description: The "Preserve IDs" feature indicates that a server
      will preserve the atom:id of entries POSTed to a collection.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.4.  XHTML Content - http://purl.org/atom/app#xhtml-content

   o  Ref: http://purl.org/atom/app#xhtml-content
   o  Label: XHTML Content
   o  Description: The "XHTML Content" feature indicates that a server
      will accept XHTML within the atom:content element.




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   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.5.  HTML Content - http://purl.org/atom/app#html-content

   o  Ref: http://purl.org/atom/app#html-content
   o  Label: HTML Content
   o  Description: The "HTML Content" feature indicates that a server
      will accept escaped HTML within the atom:content element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.6.  Text Content - http://purl.org/atom/app#text-content

   o  Ref: http://purl.org/atom/app#text-content
   o  Label: Text Content
   o  Description: The "Text Content" feature indicates that a server
      will accept plain text within the atom:content element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.7.  XML Content - http://purl.org/atom/app#xml-content

   o  Ref: http://purl.org/atom/app#xml-content
   o  Label: XML Content
   o  Description: The "XML Content" feature indicates that a server
      will accept well-formed XML content within the atom:content
      element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.8.  Binary Content - http://purl.org/atom/app#binary-content

   o  Ref: http://purl.org/atom/app#xhtml-content
   o  Label: Binary Content
   o  Description: The "Binary Content" feature indicates that a server
      will accept Base-64 encoded binary data within the atom:content
      element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:






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5.1.1.9.  Referenced Content - http://purl.org/atom/app#ref-content

   o  Ref: http://purl.org/atom/app#ref-content
   o  Label: XHTML Content
   o  Description: The "Referenced Content" feature indicates that a
      server will accept atom:content elements that use the src
      attribute to reference external content resources.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.10.  XHTML Title - http://purl.org/atom/app#xhtml-title

   o  Ref: http://purl.org/atom/app#xhtml-title
   o  Label: XHTML Title
   o  Description: The "XHTML Title" feature indicates that a server
      will accept XHTML within the atom:title element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.11.  HTML Title - http://purl.org/atom/app#html-title

   o  Ref: http://purl.org/atom/app#html-title
   o  Label: HTML Title
   o  Description: The "HTML Content" feature indicates that a server
      will accept escaped HTML within the atom:title element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.12.  Text Title - http://purl.org/atom/app#text-title

   o  Ref: http://purl.org/atom/app#text-title
   o  Label: Text Title
   o  Description: The "Text Content" feature indicates that a server
      will accept plain text within the atom:title element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.13.  XHTML Summary - http://purl.org/atom/app#xhtml-summary

   o  Ref: http://purl.org/atom/app#xhtml-summary
   o  Label: XHTML Summary
   o  Description: The "XHTML Summary" feature indicates that a server
      will accept XHTML within the atom:summary element.




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   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.14.  HTML Summary - http://purl.org/atom/app#html-summary

   o  Ref: http://purl.org/atom/app#html-summary
   o  Label: HTML Summary
   o  Description: The "HTML Summary" feature indicates that a server
      will accept escaped HTML within the atom:summary element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.15.  Text Summary - http://purl.org/atom/app#text-summary

   o  Ref: http://purl.org/atom/app#text-summary
   o  Label: Text Summary
   o  Description: The "Text Summary" feature indicates that a server
      will accept plain text within the atom:summary element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.16.  Auto Summary - http://purl.org/atom/app#auto-summary

   o  Ref: http://purl.org/atom/app#auto-summary
   o  Label: Auto Summary
   o  Description: The "Auto Summary" feature indicates that a server
      will autogenerate the value of the atom:summary element and will
      either reject or ignore attempts by the client to modify the value
      of atom:summary.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.17.  XHTML Rights - http://purl.org/atom/app#xhtml-rights

   o  Ref: http://purl.org/atom/app#xhtml-rights
   o  Label: XHTML Rights
   o  Description: The "XHTML Rights" feature indicates that a server
      will accept XHTML within the atom:rights element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:






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5.1.1.18.  HTML Rights - http://purl.org/atom/app#html-rights

   o  Ref: http://purl.org/atom/app#html-rights
   o  Label: HTML Rights
   o  Description: The "HTML Rights" feature indicates that a server
      will accept escaped HTML within the atom:rights element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.19.  Text Rights - http://purl.org/atom/app#text-rights

   o  Ref: http://purl.org/atom/app#text-rights
   o  Label: Text Rights
   o  Description: The "Text Rights" feature indicates that a server
      will accept plain text within the atom:rights element.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.20.  Authenticated Author - http://purl.org/atom/app#auth-author

   o  Ref: http://purl.org/atom/app#auth-author
   o  Label: Authenticated Author
   o  Description: The "Authenticated Author" feature indicates that a
      server will use the authenticated identity of the client to
      determine the values to use within the atom:author element.
      Attempts by a client to manually set or modify the author
      information will either be rejected or ignored by the server.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.21.  Preserve Updated - http://purl.org/atom/app#preserve-updated

   o  Ref: http://purl.org/atom/app#preserve-updated
   o  Label: Preserve Updated
   o  Description: The "Preserve Updated" feature indicates that a
      server will preserve the value of the atom:updated element
      provided by a client.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.22.  Preserve Extensions -
           http://purl.org/atom/app#preserve-extensions





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   o  Ref: http://purl.org/atom/app#preserve-extensions
   o  Label: Preserve Extensions
   o  Description: The "Preserve Extensions" feature indicates that a
      server will preserve arbitrary unknown foreign markup contained
      within an entry.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.23.  Preserve Links - http://purl.org/atom/app#preserve-links

   o  Ref: http://purl.org/atom/app#preserve-links
   o  Label: Preserve Links
   o  Description: The "Preserve Links" feature indicates that a server
      will preserve all atom:link elements contained within an entry.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.24.  Preserve Links - http://purl.org/atom/app#preserve-rights

   o  Ref: http://purl.org/atom/app#preserve-rights
   o  Label: Preserve Rights
   o  Description: The "Preserve Rights" feature indicates that a server
      will preserve all atom:rights elements contained within an entry.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.25.  Slug - http://purl.org/atom/app#slug

   o  Ref: http://purl.org/atom/app#slug
   o  Label: Slug
   o  Description: The "Slug" feature indicates that a server will use
      the Slug request header defined in section 9.7 of
      [I-D.ietf-atompub-protocol] to set the URI of newly created
      resources.
   o  Security Considerations:

5.1.1.26.  Multiple Categories -
           http://purl.org/atom/app#multiple-categories

   o  Ref: http://purl.org/atom/app#multiple-categories
   o  Label: Multiple Categories
   o  Description: The "Multiple Categories" feature indicates that a
      server will accept entries that contain multiple atom:category
      elements.




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   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.27.  Contributors - http://purl.org/atom/app#contributors

   o  Ref: http://purl.org/atom/app#contributors
   o  Label: Contributors
   o  Description: The "Contributors" feature indicates that a server
      will accept and preserve atom:contributor elements contained by an
      entry.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.28.  Multiple Authors - http://purl.org/atom/app#multiple-authors

   o  Ref: http://purl.org/atom/app#multiple-authors
   o  Label: Multiple Authors
   o  Description: The "Multiple Authors" feature indicates that a
      server will accept and preserve multiple atom:author elements
      contained by an entry.
   o  Href: http://www.ietf.org/internet-drafts/
      draft-ietf-atompub-protocol-14.txt
   o  Security Considerations:

5.1.1.29.  Feed Thread - http://purl.org/syndication/thread/1.0

   o  Ref: http://purl.org/syndication/thread/1.0
   o  Label: Feed Thread
   o  Description: The Feed Thread feature indicates that the APP server
      accepts entries that contain the in-reply-to element as defined by
      [RFC4685].
   o  Security Considerations:


6.  Normative References

   [I-D.ietf-atompub-protocol]
              Hora, B. and J. Gregorio, "The Atom Publishing Protocol",
              draft-ietf-atompub-protocol-14 (work in progress),
              March 2007.

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

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,



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              October 1998.

   [RFC4287]  Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
              Syndication Format", RFC 4287, December 2005.

   [RFC4685]  Snell, J., "Atom Threading Extensions", RFC 4685,
              September 2006.

   [W3C.REC-xml-infoset-20040204]
              Cowan, J. and R. Tobin, "XML Information Set (Second
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-infoset-20040204, February 2004,
              <http://www.w3.org/TR/2004/REC-xml-infoset-20040204>.

   [W3C.REC-xml-names-19990114]
              Layman, A., Bray, T., and D. Hollander, "Namespaces in
              XML", World Wide Web Consortium FirstEdition REC-xml-
              names-19990114, January 1999,
              <http://www.w3.org/TR/1999/REC-xml-names-19990114>.


Appendix A.  Acknowledgements

   The author acknowledges the feedback from Elias Torres, Robert Yates,
   David Johnson, Byrne Reese, Joe Gregorio and the other members of the
   IETF Atom Publishing working group during the development of this
   specification.


Author's Address

   James M Snell


   Phone:
   Email: jasnell@gmail.com
   URI:   http://snellspace.com














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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


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   The IETF takes no position regarding the validity or scope of any
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   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
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   Copies of IPR disclosures made to the IETF Secretariat and any
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   The IETF invites any interested party to bring to its attention any
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   this standard.  Please address the information to the IETF at
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Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





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