Network Working Group J. Snell Internet-Draft February 20, 2006 Expires: August 24, 2006 Atom Syndication Format Tombstones draft-snell-atompub-tombstones-02.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 aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 24, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This specification defines mechanisms by which Atom Feed publishers may explicitly indicate that specific Atom Entries have been removed from an Atom feed. Snell Expires August 24, 2006 [Page 1] Internet-Draft Atom Tombstones February 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3 3. The 'deleted-entry' element . . . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Snell Expires August 24, 2006 [Page 2] Internet-Draft Atom Tombstones February 2006 1. Introduction This specification defines mechanisms in the form of Atom Format [RFC4287] extensions that Atom Feed publishers can use to explicitly indicate that specific Atom Entries have been removed from a feed for any reason. 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; {Ed. Note: this namespace MUST be changed to a proper IETF namespace scheme prior to publication} "at": "http://purl.org/atompub/tombstones/1.0" 3. The 'deleted-entry' element The '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 at:deleted-entry { atomCommonAttributes, ( & atomID, & when { atomDateConstruct }, & by?, & comment?, & undefinedContent ) } when = element at:when { atomDateConstruct } by = element at:by { atomPersonConstruct } comment = element at:comment { atomTextConstruct } The 'deleted-entry' element MUST contain one 'atom:id' element whose value specifies the atom:id of the deleted entry. The 'deleted-entry' element MUST contain one 'when' element whose value is an [RFC3339] "date-time" specifying the instant the entry Snell Expires August 24, 2006 [Page 3] Internet-Draft Atom Tombstones February 2006 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 'deleted-entry' element MAY contain one 'by' element used to identify the entity that removed the entry from the feed. The 'deleted-entry' element MAY contain one 'comment' element whose value provides additional information about the deletion operation. The 'comment' element is Language-Sensitive as specified by [RFC4287]. Atom Feed Documents MAY contain any number of 'deleted-entry' elements. ... tag:example.org,2005:/entries/1 2005-11-29T12:12:12Z John Doe jdoe@example.org Removed comment spam tag:example.org,2005:/entries/2 2005-11-29T12:11:12Z John Doe jdoe@example.org Removed comment spam ... An Atom feed MAY contain atom:entry elements and 'deleted-entry' elements sharing the same atom:id value. Atom processors MUST ignore any 'deleted-entry' elements sharing an atom:id value with an atom: entry whose 'updated' element specifies a date and time more recent than the 'deleted-entry' element's 'when' value. 4. Security Considerations As specified in [RFC4287], Atom processors should be aware of the Snell Expires August 24, 2006 [Page 4] Internet-Draft Atom Tombstones February 2006 potential for spoofing attacks where an attacked publishes atom:entry elements with the same atom:id value of entries from other Atom feeds. The same potential exists with the mechanisms defined here in that an attacker may attempt to spoof an application into believing that a given entry has been removed from a feed. To mitigate this issue, Atom processors are advised to ignore '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 There are no IANA considerations introduced by this specification. 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. References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, July 2002. [RFC4287] Nottingham, M. and R. Sayre, "The Atom Syndication Format", RFC 4287, December 2005. [W3C.REC-xml-infoset-20040204] Tobin, R. and J. Cowan, "XML Information Set (Second Edition)", W3C REC REC-xml-infoset-20040204, February 2004. [W3C.REC-xml-names-19990114] Hollander, D., Bray, T., and A. Layman, "Namespaces in XML", W3C REC REC-xml-names-19990114, January 1999. Snell Expires August 24, 2006 [Page 5] Internet-Draft Atom Tombstones February 2006 Author's Address James M Snell Phone: Email: jasnell@gmail.com URI: http://snellspace.com Snell Expires August 24, 2006 [Page 6] Internet-Draft Atom Tombstones February 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity 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 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. Copyright Statement Copyright (C) The Internet Society (2006). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Snell Expires August 24, 2006 [Page 7]