One document matched: draft-snell-atompub-tombstones-04.xml

<?xml version="1.0"?>

<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
    <!ENTITY rfc2119 PUBLIC '' 
      'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml'>
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<rfc category="std" ipr="full3978" updates="4287" docName="draft-snell-atompub-tombstones-04.txt">
<?rfc toc="yes" ?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="yes"?>
<?rfc strict="yes" ?>
<?rfc toc="yes"?>
<?rfc compact="yes"?>

<?rfc strict="yes" ?>
<?rfc toc="yes"?>
<?rfc compact="yes"?>
<front>
<title abbrev="Atom Tombstones">Atom Syndication Format Tombstones</title>
<author initials="J.M." surname="Snell" fullname="James M Snell">
<organization></organization>
<address>
<postal>
<street></street>
<city></city> <region></region> <code></code>
<country></country>
</postal>
<phone></phone>
<email>jasnell@gmail.com</email>
<uri>http://snellspace.com</uri>
</address>
</author>
<date month="January" year="2008" />
<area>General</area>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>XML</keyword>
<keyword>Extensible Markup Language</keyword>
<keyword>Atom</keyword>
<keyword>RSS</keyword>
<keyword>Syndication</keyword>
<abstract><t>This specification adds mechanisms to the Atom Syndication Format 
which Atom Feed publishers can use to explicitly indicate that specific Atom 
entries have been removed from an Atom feed.</t></abstract>
</front>
<middle>
<section title="Introduction">

<t>This specification adds a new element to the Atom Syndication Format 
<xref target="RFC4287" /> that can be used to explicitly indicate that
specific Atom entries have been removed from an Atom Feed Document.</t>

</section>

<section title="Notational Conventions">

<t>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, <xref target="RFC2119" /></t>

<t>This specification uses XML Namespaces <xref target="W3C.REC-xml-names-19990114"/>
to uniquely identify XML element names.  It uses the following namespace prefix 
for the indicated namespace URI;</t>

<figure><artwork><![CDATA[
 "at": "http://purl.org/atompub/tombstones/1.0"
]]></artwork></figure>

</section>

<section title="The at:deleted-entry element">

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

<figure><artwork><![CDATA[
  deletedEntry = element at:deleted-entry {
    atomCommonAttributes,
    attribute ref { atomUri },
    attribute when { atomDateConstruct }?,
    ( element at:by { atomPersonConstruct}?,
    & element at:comment {atomTextConstruct}?,
    & extensionElement* )
  }
]]></artwork></figure>

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

<t>The at:deleted-entry element MAY contain a when element whose value is an 
<xref target="RFC3339"/> "date-time" specifying the instant the entry was deleted.
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</t>

<t>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 element is an Atom Person
Construct as defined by Section 3.2 of <xref target="RFC4287" />.</t>

<t>The at:deleted-entry element MAY contain one at:comment element whose value 
provides additional information about the deletion operation.  The atom:comment
element is an Atom Text Construct as defined by Section 3.1 of <xref target="RFC4287" />.</t>

<t>Atom Feed Documents MAY contain any number of at:deleted-entry elements, but 
MUST NOT contain more than one with the same ref attribute value.</t>

<figure><artwork><![CDATA[
  <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" />
     
     <!-- 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>
]]></artwork></figure>

<t>An Atom feed MAY contain atom:entry elements and at:deleted-entry elements 
sharing the same atom:id value.  Atom processors MUST 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 the at:deleted-entry element's when 
value.  If the at:deleted-entry element does not contain a when element, the 
at:deleted-entry sharing the same atom:id as an entry MUST be ignored.</t>

</section>

<section title="The Trash Link Relation">

<t>This specification registers a new "trash" link relation to the Atom Registry
of Link Relations defined in Section 7.1 of <xref target="RFC4287" />.  When appearing
on atom:link elements within either the atom:feed or atom:source elements, The 
"trash" rel attribute value signifies that the IRI in the value of href attribute 
identifies a resource listing entries that have been deleted from the Feed document.
If the linked resource is an Atom Feed Document, each of the entries in that feed
will contain copies of the atom:entry elements removed from the feed containing
the trash links.</t>

<figure><preamble>For example,</preamble><artwork><![CDATA[
  <feed xmlns="http://www.w3.org/2005/Atom">
    ...
    <link rel="trash" type="application/atom+xml" href="trash.xml" />
    <link rel="trash" type="application/xhtml+xml" href="trash.xml" />
    ...
  </feed>
]]></artwork></figure>

<t>A single linked trash resource may list entries deleted from
multiple feed documents. In such cases, each entry in the trash resource SHOULD
reference the feed from which the entry was removed. For instance, if the 
trash resource is an Atom Feed Document, each entry would contain an atom:source
element identifying the feed the entry was deleted from.</t>

<t>Linked "trash" resources are orthogonal to the at:deleted-entry element and 
are intended to provide servers with a way of allowing clients to recover deleted 
entries. For instance, the entries in a feed may be managed by two separate 
authors, one of whom may delete an entry that the other author wishes to later 
recover.  If a trash feed is provided, the second author can look for a copy of 
the deleted entry there.</t>

<t>While it will be common for servers to provide only a single trash 
resource per feed, or to have multiple feeds share a single trash resource, 
it is possible for a single feed to contain multiple trash links. The relationship 
between multiple trash links is undefined. Individual entries deleted from the 
feed containing the linked trash resources MAY appear in any, all or none of the 
linked trash resources.  It is up to the server implementation to decide whether 
to provide a trash resource and whether or not to add deleted entries to those 
resources.</t>

</section>

<section title="Security Considerations">
  <t>As specified in <xref target="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 atom: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.</t>
</section>

<section title="IANA Considerations">
  
<section title="The Link Relation Registration "Trash"">
  <t>
    <list style="hanging">
      <t hangText="Attribute Value:">trash</t>
      <t hangText="Description:">An IRI of a resource listing deleted resources.
        When appearing within an atom:feed or atom:source elements, signifies 
        that the IRI in the value of the href attribute identifies a resource
        listing entries that have been deleted from the Feed document.
      </t>
      <t hangText="Expected display characteristics:">
          Undefined; this relation can be used for
          background processing or to provide extended functionality without
          displaying its value.
      </t> 
      <t hangText="Security considerations:">                   
          Automated agents should take care when this
          relation crosses administrative domains (e.g., the URI has a different
          authority than the current document).
      </t>
    </list>
  </t>
</section>
  
</section>

<section title="Acknowledgements">
<t>The author gratefully acknowledges the feedback from the members of the 
Atom Publishing Format and Protocol working group during the development of 
this specification.</t>
</section>

</middle>

<back>
<references title="Normative References">
  &rfc2119;
  &rfc3339;
  &rfc4287;
  &xmlnames;
</references>
</back>
</rfc>