Network Working Group J. Snell Internet-Draft June 8, 2009 Updates: 4287 (if approved) Intended status: Informational Expires: December 10, 2009 The Atom "deleted-entry" Element draft-snell-atompub-tombstones-06.txt 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), 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 December 10, 2009. Copyright Notice Copyright (c) 2009 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 Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This specification adds mechanisms to the Atom Syndication Format which Atom Feed publishers can use to explicitly identify Atom Snell Expires December 10, 2009 [Page 1] Internet-Draft Atom deleted-entry June 2009 entries that have been removed from an Atom feed. 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 . . . . . . . . . . . . . . . . . . . . . . . . . 5 Snell Expires December 10, 2009 [Page 2] Internet-Draft Atom deleted-entry June 2009 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}?, & 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 element is an Atom Person Construct as defined by Section 3.2 of [RFC4287]. Snell Expires December 10, 2009 [Page 3] Internet-Draft Atom deleted-entry June 2009 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]. 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. ... John Doe jdoe@example.org Removed comment spam ... 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 the at:deleted-entry element's when value. 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. Snell Expires December 10, 2009 [Page 4] Internet-Draft Atom deleted-entry June 2009 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 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. 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. [W3C.REC-xml-names-19990114] Bray, T., Hollander, D., and A. Layman, "Namespaces in XML", World Wide Web Consortium FirstEdition REC-xml- names-19990114, January 1999, . Snell Expires December 10, 2009 [Page 5] Internet-Draft Atom deleted-entry June 2009 Author's Address James M Snell Phone: Email: jasnell@us.ibm.com URI: http://ibm.com Snell Expires December 10, 2009 [Page 6]