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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 RFC 6721

Network Working Group                                           J. Snell
Internet-Draft                                              May 19, 2010
Updates: 4287 (if approved)
Intended status: Informational
Expires: November 20, 2010


                    The Atom "deleted-entry" Element
                 draft-snell-atompub-tombstones-08.txt

Abstract

   This specification adds mechanisms to the Atom Syndication Format
   which Atom Feed publishers can use to explicitly identify Atom
   entries that have been removed from an Atom feed.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 20, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . . . 3
   3.  The at:deleted-entry element  . . . . . . . . . . . . . . . . . 3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6









































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1.  Introduction

   This specification adds a new element to the Atom Syndication Format
   [RFC4287] that can be used to explicitly indicate that specific
   entries have been removed from a feed.


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;

    "at": "http://purl.org/atompub/tombstones/1.0"


3.  The at:deleted-entry element

   The at:deleted-entry element MAY appear as a child of atom:feed to
   represent an Atom Entry that has been removed from a feed.

     deletedEntry = element at:deleted-entry {
       atomCommonAttributes,
       attribute ref { atomUri },
       attribute when { atomDateConstruct },
       ( element at:by { atomPersonConstruct}?,
       & element at:comment {atomTextConstruct}?,
       & element atom:link*,
       & element atom:source?,
       & extensionElement* )
     }

   The at:deleted-entry element MUST contain a ref attribute whose value
   specifies the value of the atom:id of the entry that has been
   removed.

   The at:deleted-entry element MUST contain a when attribute whose
   value is an [RFC3339] "date-time" specifying the instant the entry
   was removed from the feed.  An uppercase "T" character MUST be used
   to separate date and time, and an uppercase "Z" character MUST be
   present in the absence of a numeric time zone offset

   The at:deleted-entry element MAY contain one at:by element used to
   identify the entity that removed the entry from the feed.  The at:by



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   element is an Atom Person Construct as defined by Section 3.2 of
   [RFC4287].

   The at:deleted-entry element MAY contain one at:comment element whose
   value provides additional, language-sensitive information about the
   deletion operation.  The atom:comment element is an Atom Text
   Construct as defined by Section 3.1 of [RFC4287].

   The at:deleted-entry element MAY contain any number of atom:link
   elements as specified by Section 4.2.7 of [RFC4287].

   The at:deleted-entry element MAY contain one atom:source element.  If
   the at:deleted-entry is copied from one feed into another feed, the
   source atom:feed's metadata MAY be preserved within the copied at:
   deleted-entry by adding an atom:source child element and including
   the source atom:feed's metadata elements as children of the atom:
   source.

   An Atom feed MAY contain any number of at:deleted-entry elements, but
   MUST NOT contain more than one with the same combination of ref and
   when attribute values.

     <feed xmlns="http://www.w3.org/2005/Atom"
           xmlns:at="http://purl.org/atompub/tombstones/1.0">
        ...
        <!-- Minimal deleted-entry -->
        <at:deleted-entry
          ref="tag:example.org,2005:/entries/1"
          when="2005-11-29T12:11:12Z"/>

        <!-- Extended deleted-entry -->
        <at:deleted-entry
          ref="tag:example.org,2005:/entries/2"
          when="2005-11-29T12:11:12Z">
          <at:by>
            <name>John Doe</name>
            <email>jdoe@example.org</email>
          </at:by>
          <at:comment>Removed comment spam</at:comment>
        </at:deleted-entry>
        ...
     </feed>

   An Atom feed MAY contain atom:entry elements and at:deleted-entry
   elements sharing the same atom:id value.  Atom processors SHOULD
   ignore any at:deleted-entry elements sharing an atom:id value with an
   atom:entry whose atom:updated element specifies a date and time more
   recent than or equal to the at:deleted-entry element's when value.



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   Elements and attributes from other XML vocabularies MAY be used
   within an at:deleted-entry element following the same model defined
   by Section 6 of [RFC4287].  Processors encountering such markup MUST
   NOT stop processing or signal an error.  It might be the case that
   the Processor is able to process the foreign markup correctly and
   does so.  When unknown markup is encountered as a child of at:
   deleted-entry, Processors MAY bypass the markup and any textual
   content and MUST NOT change their behavior as a result of the
   markup's presence.


4.  Security Considerations

   As specified in [RFC4287], Atom processors should be aware of the
   potential for spoofing attacks where an attacker publishes atom:entry
   or atom:deleted-entry elements using the same atom:id values as
   entries from other Atom feeds.  An attacker may attempt to trick an
   application into believing that a given entry has either been removed
   from or added to a feed.  To mitigate this issue, Atom processors are
   advised to ignore at:deleted-entry elements referencing entries that
   have not previously appeared within the containing Feed document and
   should take steps to verify the origin of the Atom feed before
   considering the entries to be removed.


5.  IANA Considerations

   No IANA actions are required by this document.


6.  Acknowledgements

   The author gratefully acknowledges the feedback from the members of
   the Atom Publishing Format and Protocol working group during the
   development of this specification.


7.  Normative References

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

   [RFC3339]  Klyne, G., Ed. and C. Newman, "Date and Time on the
              Internet: Timestamps", RFC 3339, July 2002.

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




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


Author's Address

   James M Snell


   Phone:
   Email: jasnell@us.ibm.com
   URI:   http://ibm.com




































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