Network Working Group J. Snell
Internet-Draft January 2, 2008
Intended status: Standards Track
Expires: July 5, 2008
Atom Syndication Format Tombstones
draft-snell-atompub-tombstones-03.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This specification defines mechanisms by which Atom Feed publishers
can explicitly indicate that specific Atom Entries have been removed
from an Atom feed.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
3. The atom:deleted-entry element . . . . . . . . . . . . . . . . 3
4. The Trash Link Relation . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6.1. The Link Relation Registration "Trash" . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 7
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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 Atom
entries have been removed from an Atom Feed Document.
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;
"atom": "http://www.w3.org/2005/Atom"
3. The atom:deleted-entry element
The atom:deleted-entry element MAY appear as a child of atom:feed to
represent an Atom Entry that has been removed from the feed.
deletedEntry = element atom:deleted-entry {
atomCommonAttributes,
( & atomID,
& element atom:when { atomDateConstruct }?,
& element atom:by { atomPersonConstruct}?,
& element atom:comment {atomTextConstruct}?,
& extensionElement* )
}
The atom:deleted-entry element MUST contain one atom:id element whose
value specifies the atom:id of the entry that has been removed.
The atom:deleted-entry element MAY contain one atom:when element
whose value is an [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
The atom:deleted-entry element MAY contain one atom:by element used
to identify the entity that removed the entry from the feed. The
atom:by element is an Atom Person Construct as defined by Section 3.2
of [RFC4287].
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The atom:deleted-entry element MAY contain one atom: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 [RFC4287].
Atom Feed Documents MAY contain any number of atom:deleted-entry
elements.
...
tag:example.org,2005:/entries/1tag:example.org,2005:/entries/22005-11-29T12:11:12ZJohn Doejdoe@example.orgRemoved comment spam
...
An Atom feed MAY contain atom:entry elements and atom:deleted-entry
elements sharing the same atom:id value. Atom processors MUST ignore
any atom: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 atom:deleted-entry element's atom:when value. If the
atom:deleted-entry element does not contain an atom:when element, the
atom:deleted-entry sharing the same atom:id as an entry MUST be
ignored.
4. The Trash Link Relation
When an entry is deleted from one feed, a server can choose to move
that entry into another Feed document whose member entries consist
entirely of deleted entries. Such "trash" feeds are similar in
nature to desktop operating system trash folders that are used to
collect, and potentially recover items that have been deleted.
This specification registers a new "trash" link relation to the Atom
Registry of Link Relations defined in Section 7.1 of [RFC4287]. When
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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.
For example,
...
...
5. 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 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.
6. IANA Considerations
6.1. The Link Relation Registration "Trash"
Attribute Value: trash
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.
Expected display characteristics: Undefined; this relation can be
used for background processing or to provide extended
functionality without displaying its value.
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).
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7. 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.
8. 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.
[W3C.REC-xml-names-19990114]
Hollander, D., Layman, A., and T. Bray, "Namespaces in
XML", World Wide Web Consortium FirstEdition REC-xml-
names-19990114, January 1999,
.
Author's Address
James M Snell
Phone:
Email: jasnell@gmail.com
URI: http://snellspace.com
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