Network Working Group J. Snell Internet-Draft February 27, 2006 Expires: August 31, 2006 Atom Syndication Format Revision Tracking draft-snell-atompub-revision-00.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 31, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This specification defines metadata extensions for use with the Atom Syndication Format to track revisions of entries. Snell Expires August 31, 2006 [Page 1] Internet-Draft Atom Revisions February 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3 3. The 'revision' element . . . . . . . . . . . . . . . . . . . . 3 4. The 'host' Element . . . . . . . . . . . . . . . . . . . . . . 5 5. The 'comment' Element . . . . . . . . . . . . . . . . . . . . 6 6. The 'deleted-entry' element . . . . . . . . . . . . . . . . . 7 7. The 'history' Link Relation . . . . . . . . . . . . . . . . . 8 8. The 'diff' Link Relation . . . . . . . . . . . . . . . . . . . 9 9. The 'initial-revision' Link Relation . . . . . . . . . . . . . 10 10. The 'current-revision' Link Relation . . . . . . . . . . . . . 10 11. The 'this-revision' Link Relation . . . . . . . . . . . . . . 10 12. The 'prior-revision' Link Relation . . . . . . . . . . . . . . 11 13. The 'next-revision' Link Relation . . . . . . . . . . . . . . 11 14. Security Considerations . . . . . . . . . . . . . . . . . . . 12 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 16. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15 Intellectual Property and Copyright Statements . . . . . . . . . . 16 Snell Expires August 31, 2006 [Page 2] Internet-Draft Atom Revisions February 2006 1. Introduction This specification defines metadata extensions for use with the Atom Syndication Format [RFC4287] to track revisions of entries. The extensions include versioning of entries, links to change summaries and histories, and indicators as to the relative importance, or significance of the revision. 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} "ar": "http://purl.org/atompub/revision/1.0" 3. The 'revision' element The 'revision' element MAY appear as a child of an atom:entry element to identify a "revision number" for the entry. revision = element ar:revision { atomCommonAttributes, attribute number { text }, attribute scheme { atomIRI }?, attribute label { text }?, attribute when { date-time }?, attribute initial { 'yes' | 'no' }?, attribute final { 'yes' | 'no' }?, attribute significant { 'yes' | 'no' }?, ( atomTextConstruct ) } The 'revision' element is an extension of the Atom Text Construct that is used to identify a "revision number" for an entry. The revision element MUST contain a 'number' attribute whose value identifies the revision number of the entry. The text value of the element MAY be used to provide a summary of the revision. Within the number attribute, escaped versions of characters such as "&" and ">" Snell Expires August 31, 2006 [Page 3] Internet-Draft Atom Revisions February 2006 represent those characters, not markup. The 'scheme' attribute MAY be used to provide an IRI identifying the scheme used to produce the revision number specified by the 'number' attribute. If the scheme attribute is not specified, the value of the 'number' attribute MUST be a non-negative numeric value. The 'label' attribute MAY be used to associate a simple human readable text label with the revision. Within the value, escaped versions of characters such as "&" and ">" represent those characters, not markup. The 'when' attribute MAY be used to provide an RFC3339 date-time specifying the date and time that the revision was performed. 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 'initial' attribute indicates whether or not this revision represents the initial version of an entry. The value is either "yes" or "no". When missing, the value is considered to be "no". The 'final' attribute indicates whether or not this revision represents the final version of an entry. The value is either "yes" or "no". Feed publishers SHOULD NOT continue to update atom:entry's that have been marked as "final" revisions. Atom processors MAY ignore atom:entry elements with revision element values and atom: updated values greater than those specified in a "final" revision. When missing, the value is considered to be "no". The 'significant' attribute indicates whether or not the revision should be considered to be "significant" or not. The value is either "yes" or "no". Atom processors MAY choose to process or present significant revisions differently than non-significant revisions. When missing, the value is considered to be "no". Snell Expires August 31, 2006 [Page 4] Internet-Draft Atom Revisions February 2006 For example, ... ... Fixed typographical and factual errors ... An Atom entry is a revision of a prior entry only if the two entries share the same atom:id value and the revision number attribute and atom:updated element values are both greater than the previous version of the entry. 4. The 'host' Element Atom Person Constructs contained within an atom entry MAY contain a 'host' element whose value is either the IP Address or Domain host name from which the person created or modified the entry. Within value of the 'host' element, the escaped versions of characters such as "&" and ">" represent those characters, not markup. host = element ar:host { text } Snell Expires August 31, 2006 [Page 5] Internet-Draft Atom Revisions February 2006 For example, ... ... James 192.168.1.106 ... 5. The 'comment' Element Atom entry and feed elements MAY contain zero or more 'comment' elements that provide the equivalent to editorial notes. comment = element ar:comment { atomCommonAttributes, (atomAuthor?, atomUpdated, atomSummary, undefinedContent) } The 'comment' element SHOULD contain an atom:author element identifying the person or entity that created the comment. The 'comment' element MUST contain one atom:updated element that specifies the date and time that the comment was created and added to the entry or feed. The 'comment' element MUST contain one atom:summary element that contains containing the text of the comment. Snell Expires August 31, 2006 [Page 6] Internet-Draft Atom Revisions February 2006 For example, ... ... James 2006-02-21T00:00:00Z We still need to fix the factual errors in this entry ... 6. 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, & revision?, & when, & by?, & undefinedContent ) } when = element at:when { atomDateConstruct } by = element at:by { atomPersonConstruct } The 'deleted-entry' element MUST contain one 'atom:id' element whose value specifies the atom:id of the deleted entry. The 'deleted-entry' MAY contain one revision element. One 'when' element MUST be provided specifying the instant the entry was deleted. The 'when' element is an Atom Date Construct as defined by [RFC4287]. One 'by' element MAY by provided to identify the person or entity that removed the entry from the feed. The 'by' element is an Atom Person Construct as defined by [RFC4287]. Snell Expires August 31, 2006 [Page 7] Internet-Draft Atom Revisions February 2006 Atom Feed Documents MAY contain any number of 'deleted-entry' elements. ... tag:example.org,2005:/entries/1 Removed comment spam 2005-11-29T12:12:12Z John Doe jdoe@example.org 192.168.1.106 ... 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. 7. The 'history' Link Relation Atom entry elements MAY contain an atom:link element with a rel attribute value of 'history' whose href attribute identifies a resource describing the revision history of the entry. If the history link points to an Atom Feed Document, the referenced feed MUST contain one or more atom:entry or 'deleted-entry' elements, each of which represents one revision of the entry. The entry and deleted-entry elements MUST have the same atom:id value and MUST have different 'revision', atom:updated or when values. ... ... ... Snell Expires August 31, 2006 [Page 8] Internet-Draft Atom Revisions February 2006 An example History Feed ... tag:example.org,2006:entries/1 2006-02-27T00:00:00Z tag:example.org,2006:entries/1 2006-02-26T00:00:00Z Fixed typos ... tag:example.org,2006:entries/1 2006-02-25T00:00:00Z ... 8. The 'diff' Link Relation Atom entry elements MAY contain an atom:link element with a rel attribute value of 'diff' whose href attribute identifies a resource describing the deltas between this revision of the entry and the previous revision. ... ... ... Snell Expires August 31, 2006 [Page 9] Internet-Draft Atom Revisions February 2006 9. The 'initial-revision' Link Relation Atom entry elements MAY contain an atom:link element with a rel attribute value of 'initial-revision' whose href attribute specifies the URI of an Atom Entry Document representing the initial version of the entry. ... ... ... 10. The 'current-revision' Link Relation Atom entry elements MAY contain an atom:link element with a rel attribute value of 'current-revision' whose href attribute specifies the URI of an Atom Entry Document representing the current version of the entry. ... ... ... 11. The 'this-revision' Link Relation Atom entry elements MAY contain an atom:link element with a rel attribute value of 'this-revision' whose href attribute specifies the URI of an Atom Entry Document representing the this version of the entry. Snell Expires August 31, 2006 [Page 10] Internet-Draft Atom Revisions February 2006 ... ... ... 12. The 'prior-revision' Link Relation Atom entry elements MAY contain an atom:link element with a rel attribute value of 'prior-revision' whose href attribute specifies the URI of an Atom Entry Document representing the previous version of the entry. ... ... ... 13. The 'next-revision' Link Relation Atom entry elements MAY contain an atom:link element with a rel attribute value of 'next-revision' whose href attribute specifies the URI of an Atom Entry Document representing the subsequent version of the entry. ... ... ... Snell Expires August 31, 2006 [Page 11] Internet-Draft Atom Revisions February 2006 14. Security Considerations The extensions defined in this specification are subject to the same security considerations as discussed in [RFC4287]. 15. IANA Considerations This specification defines seven new link relations for the IANA Registry of Link Relations as defined by [RFC4287]. Snell Expires August 31, 2006 [Page 12] Internet-Draft Atom Revisions February 2006 Attribute Value: history Description: identifies a resource describing the revision history of an atom:entry Display characteristics: None Security considerations: Same as Attribute Value: diff Description: identifies a resource describing the deltas between the current revision of an atom:entry and its prior version. Display characteristics: None Security considerations: Same as Attribute Value: initial-revision Description: identifies an Atom Entry Document describing the initial version of a resource Display characteristics: None Security considerations: Same as Attribute Value: current-revision Description: identifies an Atom Entry Document describing the current version of a resource Display characteristics: None Security considerations: Same as Attribute Value: this-revision Description: identifies an Atom Entry Document describing the version of the resource containing the this-revision link. Display characteristics: None Security considerations: Same as Attribute Value: prior-revision Description: identifies an Atom Entry Document describing the previous version of a resource Display characteristics: None Security considerations: Same as Attribute Value: next-revision Description: identifies an Atom Entry Document describing the next version of a resource Display characteristics: None Security considerations: Same as 16. Acknowledgements The author gratefully acknowledges the feedback from the members of Snell Expires August 31, 2006 [Page 13] Internet-Draft Atom Revisions February 2006 the Atom Publishing Format and Protocol working group during the development of this specification. Some of the language included in this draft has been adapted directly from the Atom Syndication Format [RFC4287] in order to maintain a stylistic and technical alignment to that specification. 17. 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-names-19990114] Hollander, D., Bray, T., and A. Layman, "Namespaces in XML", W3C REC REC-xml-names-19990114, January 1999. Snell Expires August 31, 2006 [Page 14] Internet-Draft Atom Revisions February 2006 Author's Address James M Snell Phone: Email: jasnell@gmail.com URI: http://snellspace.com Snell Expires August 31, 2006 [Page 15] Internet-Draft Atom Revisions 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 31, 2006 [Page 16]