Network Working GroupA. Brown
Internet-DraftG. Clemm
Intended status: InformationalIBM
Expires: June 7, 2010J. Reschke, Editor
December 4, 2009

Link Relations for Simple Version Navigation


This specification defines Atom link relations for navigation between a resource and its versions.

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.

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This Internet-Draft will expire on June 7, 2010.

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. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License.

Editorial Note (To be removed by RFC Editor before publication)

Please send comments to the Atom Syntax mailing list (<>).


Note that although discussion takes place on the Atompub working group's mailing list, this is not a working group document.

XML versions, latest edits and the issues list for this document are available from <>.

 I  edit   (type: edit, status: open)
julian.reschke@greenbytes.de2009-11-19 Umbrella issue for editorial fixes/enhancements.
Associated changes in this document: <#rfc.change.edit.1>, 2, <#rfc.change.edit.3>, A, <#rfc.change.edit.5>, B.
 I  cmis   (type: edit, status: closed)
julian.reschke@greenbytes.de2009-12-01 Add a pointer to the CMIS spec, so AtomPub use cases become clearer.
Associated changes in this document: 1, 7.2, 7.2.

1. Introduction

This specification defines link relations that may be used on a resource that exists in a system that supports versioning to navigate among the different resources available, such as past versions.


These link relations are used in the AtomPub ([RFC5023]) bindings of the "Content Management Interoperability Services" (CMIS). See Section of [CMIS] for further information.

2. Terminology

 I  checked-out   (type: change, status: closed)
algermissen1971@mac.com2009-11-24 It is not clear to me, what the meaning of 'check out' and 'check in'. Also, the text (IMO) creates the impression that versioning can only take place when 'check out' and 'check in' are applied. However, a resource could also be versioned by the server upon any modification made by a client regardless of any 'checking out' or 'checking in'. The link relations specified would still make sense.
Assuming that 'checking out' and 'checking in' are operations on resources, I think the draft should address how clients achieve these operations. This would at least involve another link relation and specification how to use the linked resource to perform a checkout.
2009-12-04Resolution: Rephrased terminology; added explanations for checkin/checkout.
Associated changes in this document: 2, 2.

Versioned Resource

Version History

Predecessor, Successor

Working Copy



  • A "checkout" is an operation on a versioned resource that creates a working copy, or changes the versioned resource to be a working-copy as well ("in-place versioning").


  • A "checkin" is an operation on a working copy that creates a new version of its corresponding versioned resource.
 I  working-copy-of   (type: change, status: open)
algermissen1971@mac.com2009-12-02 ...what is your opinion regarding the introduction of a link relation that is the opposite of working-copy in order to being able to find the versioned resource that the working copy I have is a working copy of?
I am undecided regarding the necessity, but without a working-copy-of relation it seems the client would need to maintain that information (the relationship or the fact that a given resource is a working copy) across requests.
Associated changes in this document: 3, 4, A.

3. Link Relations

The following link relations are defined:

3.1. version-history

When included on a versioned resource, this link points to a resource containing the version history for this resource.

3.2. latest-version

When included on a versioned resource, this link points to a resource containing the latest (e.g., current) version.

The latest version is defined by the system. For linear versioning systems, this is probably the latest version by timestamp. For systems that support branching, there will be multiple latest versions, one for each branch in the version history.

Some systems may allow multiple of these link relations.

3.3. working-copy

When included on a versioned resource, this link points to a working copy for this resource.

Some systems may allow multiple of these link relations.


3.4. working-copy-of

When included on a working copy, this link points to the versioned resource from which this working copy was obtained.

3.5. predecessor-version

When included on a versioned resource, this link points to a resource containing the predecessor version in the version history.

Some systems may allow multiple of these link relations in the case of a multiple branches merging.

3.6. successor-version

When included on a versioned resource, this link points to a resource containing the successor version in the version history.

Some systems may allow multiple of these link relations in order to support branching.

4. IANA Considerations

The link relations below are to be registered by IANA per Section 7.1 of [RFC4287]:


5. Security Considerations

Automated agents should take care when these relation crosses administrative domains (e.g., the URI has a different authority than the current document). Such agents should also take care to detect circular references.


6. Acknowledgments

Thanks to the members of Content Management Interoperability Services (CMIS) Technical Committee (TC) at OASIS for the initial proposal, and to Jan Algermissen for feedback during IETF review.

7. References

7.1. Normative References

Nottingham, M. and R. Sayre, “The Atom Syndication Format”, RFC 4287, December 2005.

7.2. Informative References

Brown, A., Gur-Esh, E., McVeigh, R., and F. Muller, “Content Management Interoperability Services (CMIS) Version 1.0”, OASIS CMIS v1.0 Committee Draft 04, September 2009, <>.
Nottingham, M., “Web Linking”, Internet-Draft draft-nottingham-http-link-header-06 (work in progress), July 2009.
Day Software, Nuescheler, D., and P. Piegaze, “Content Repository API for Java(tm) Technology Specification”, Java Specification Request 283, August 2009, <>.
Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. Whitehead, “Versioning Extensions to WebDAV (Web Distributed Authoring and Versioning)”, RFC 3253, March 2002.
Gregorio, J. and B. de hOra, “The Atom Publishing Protocol”, RFC 5023, October 2007.

Appendix A. Relationship to Java Content Repository (JCR) and WebDAV

The link relations defined in Section 3 correspond to various properties used in WebDAV Versioning [RFC3253] and JCR [JSR-283]:



working- I resourcecopy






del-1. Contributors

The content and concepts within are a product of the Content Management Interoperability Services (CMIS) Technical Committee (TC) at OASIS.

All members of the TC have contributed.

Appendix B. Change Log (to be removed by RFC Editor before publication)


Authors' Addresses

Al Brown
3565 Harbor Blvd
Costa Mesa, California 92626
Geoffrey Clemm
20 Maguire Road
Lexington, MA 02421
Julian F. Reschke (editor)
greenbytes GmbH
Hafenweg 16
Muenster, NW 48155