Network Working Group A. Brown Internet-Draft G. Clemm Intended status: Informational IBM Expires: May 24, 2010 J. Reschke, Ed. greenbytes November 20, 2009 Link Relations for Simple Version Navigation draft-brown-versioning-link-relations-03 Abstract This specification defines Atom link relations for navigation between a resource and its versions. Editorial Note (To be removed by RFC Editor before publication) Please send comments to the Atom Syntax mailing list (). 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 May 24, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. Brown, et al. Expires May 24, 2010 [Page 1] Internet-Draft Version Navigation Link Relations November 2009 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Link Relations . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. version-history . . . . . . . . . . . . . . . . . . . . . 3 3.2. latest-version . . . . . . . . . . . . . . . . . . . . . . 4 3.3. working-copy . . . . . . . . . . . . . . . . . . . . . . . 4 3.4. predecessor-version . . . . . . . . . . . . . . . . . . . 4 3.5. successor-version . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 4.1. 'version-history' Link Relation Registration . . . . . . . 4 4.2. 'latest-version' Link Relation Registration . . . . . . . 5 4.3. 'working-copy' Link Relation Registration . . . . . . . . 5 4.4. 'predecessor-version' Link Relation Registration . . . . . 5 4.5. 'successor-version' Link Relation Registration . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Normative References . . . . . . . . . . . . . . . . . . . 6 6.2. Informative References . . . . . . . . . . . . . . . . . . 6 Appendix A. Relationship to Java Content Repository (JCR) and WebDAV . . . . . . . . . . . . . . . . . . . . . . . 7 A.1. Example: Use of Link Relations in HTTP Link Header . . . . 8 Appendix B. Contributors . . . . . . . . . . . . . . . . . . . . 9 Appendix C. Change Log (to be removed by RFC Editor before publication) . . . . . . . . . . . . . . . . . . . . 9 C.1. Since draft-brown-link-relations-00 . . . . . . . . . . . 9 C.2. Since draft-brown-link-relations-01 . . . . . . . . . . . 10 C.3. Since draft-brown-link-relations-02 . . . . . . . . . . . 10 Appendix D. Resolved issues (to be removed by RFC Editor before publication) . . . . . . . . . . . . . . . . . 10 D.1. iana . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Appendix E. Open issues (to be removed by RFC Editor prior to publication) . . . . . . . . . . . . . . . . . . . . 10 E.1. edit . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Brown, et al. Expires May 24, 2010 [Page 2] Internet-Draft Version Navigation Link Relations November 2009 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. 2. Terminology Versioned Resource When a resource is put under version control, it becomes a "versioned resource". A versioned resource can be "checked out" to allow modification. Version History A "version history" resource is a resource that contains all the versions of a particular versioned resource. Predecessor, Successor When a versioned resource is checked out and then subsequently checked in, the version that was checked out becomes a "predecessor" of the version created by the checkin. A client can specify multiple predecessors for a new version if the new version is logically a merge of those predecessors. The inverse of the predecessor relation is the "successor" relation. Therefore, if X is a predecessor of Y, then Y is a successor of X. Working Copy A "working copy" is a resource at a server-defined URL that can be modified to create a new version of a versioned resource. 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. Brown, et al. Expires May 24, 2010 [Page 3] Internet-Draft Version Navigation Link Relations November 2009 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. 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. 3.5. 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]: 4.1. 'version-history' Link Relation Registration Attribute Value: version-history Brown, et al. Expires May 24, 2010 [Page 4] Internet-Draft Version Navigation Link Relations November 2009 Description: See Section 3.1. Expected display characteristics: Undefined; this relation can be used for background processing or to provide extended functionality without displaying its value. Security considerations: See Section 5. 4.2. 'latest-version' Link Relation Registration Attribute Value: latest-version Description: See Section 3.2. Expected display characteristics: Undefined; this relation can be used for background processing or to provide extended functionality without displaying its value. Security considerations: See Section 5. 4.3. 'working-copy' Link Relation Registration Attribute Value: working-copy Description: See Section 3.3. Expected display characteristics: Undefined; this relation can be used for background processing or to provide extended functionality without displaying its value. Security considerations: See Section 5. 4.4. 'predecessor-version' Link Relation Registration Attribute Value: predecessor-version Description: See Section 3.4. Expected display characteristics: Undefined; this relation can be used for background processing or to provide extended functionality without displaying its value. Security considerations: See Section 5. Brown, et al. Expires May 24, 2010 [Page 5] Internet-Draft Version Navigation Link Relations November 2009 4.5. 'successor-version' Link Relation Registration Attribute Value: successor-version Description: See Section 3.5. Expected display characteristics: Undefined; this relation can be used for background processing or to provide extended functionality without displaying its value. Security considerations: See Section 5. 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. References 6.1. Normative References [RFC4287] Nottingham, M. and R. Sayre, "The Atom Syndication Format", RFC 4287, December 2005. 6.2. Informative References [JSR-283] Day Software, Nuescheler, D., and P. Piegaze, "Content Repository API for Java[TM] Technology Specification", Java Specification Request 283, August 2009, . [RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. Whitehead, "Versioning Extensions to WebDAV (Web Distributed Authoring and Versioning)", RFC 3253, March 2002. [draft-nottingham-http-link-header] Nottingham, M., "Web Linking", draft-nottingham-http-link-header-06 (work in progress), July 2009. Brown, et al. Expires May 24, 2010 [Page 6] Internet-Draft Version Navigation Link Relations November 2009 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]: version-history WebDAV: the resource identified by the DAV:version-history property ([RFC3253], Sections 5.2.1 and 5.3.1). JCR: the node identified by jcr:versionHistory property ([JSR-283], Section 3.13.2.4) for versionable nodes, the parent folder for version nodes. latest-version WebDAV: for version-controlled resources, DAV:checked-in ([RFC3253], Section 3.2.1) or DAV:checked-out ([RFC3253], Section 3.3.1), depending on checkin state. For version resources, a successor version that itself does not have any successors. JCR: the version node identified by the jcr:baseVersion property ([JSR-283], Section 3.13.2.5) for versionable nodes; for version nodes, a successor version that itself does not have any successors. working-resource WebDAV: for version-controlled resources that are checked-out in place: the resource itself. For version resources: each resource identified by a member of the DAV:checkout-set property (see [RFC3253], Section 3.4.3). JCR: for checked-out versionable nodes: the node itself. predecessor-version WebDAV: each resource identified by a member of DAV:predecessor- set ([RFC3253], Sections 3.3.2 and 3.4.1). JCR: each node identified by a member of jcr:predecessors ([JSR-283], Section 3.13.3.3). successor-version WebDAV: each resource identified by a member of DAV:successor-set ([RFC3253], Section 3.4.2). Brown, et al. Expires May 24, 2010 [Page 7] Internet-Draft Version Navigation Link Relations November 2009 JCR: each node identified by a member of jcr:successors ([JSR-283], Section 3.13.3.4). A.1. Example: Use of Link Relations in HTTP Link Header The "Web Linking" specification ([draft-nottingham-http-link-header]) generalizes Atom link relations, and also re-introduces the HTTP "Link" header as a way to expose link relations in HTTP responses. This will make it possible to expose version links independently from a specific vocabulary, be it the Atom Feed Format ([RFC4287]) or WebDAV properties ([RFC3253]). For instance, a response to an VERSION-CONTROL request ([RFC3253], Section 3.5) could expose newly created version-history and checked-in version as link relations: >> Request: VERSION-CONTROL /docs/test.txt HTTP/1.1 Host: example.net >> Response: HTTP/1.1 200 OK Link: ; rel=latest-version; anchor= Link: ; rel=version-history; anchor= (Note that in this case, the anchor parameter is used, as the response to a VERSION-CONTROL request is not a representation of the resource at the Request-URI) A subsequent HEAD request on that resource could expose the version- history and latest-version relations as well: >> Request: HEAD /docs/test.txt HTTP/1.1 Host: example.net Brown, et al. Expires May 24, 2010 [Page 8] Internet-Draft Version Navigation Link Relations November 2009 >> Response: HTTP/1.1 200 OK Content-Type: text/plain; charset=UTF-8 Content-Length: 12345 Link: ; rel=latest-version Link: ; rel=version-history After creating more versions, following the latest-version would then expose predecessors of a version: >> Request: HEAD /system/v/84345634/3 HTTP/1.1 Host: example.net >> Response: HTTP/1.1 200 OK Content-Type: text/plain; charset=UTF-8 Content-Length: 12323 Link: ; rel=predecessor-version Appendix B. 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 C. Change Log (to be removed by RFC Editor before publication) C.1. Since draft-brown-link-relations-00 Added Geoff Clemm as author. Renamed link relation "all-versions" to "version-history". Fixed description of "working-resource" relation to state that it appears on a version resource. Brown, et al. Expires May 24, 2010 [Page 9] Internet-Draft Version Navigation Link Relations November 2009 C.2. Since draft-brown-link-relations-01 Rewrite terminology and link relations using simpler definitions that can reflect versioning approaches different from WebDAV. Add JCR/WebDAV property table. And reference to Web Linking draft (for now informative) and examples showing use of the Link header. C.3. Since draft-brown-link-relations-02 Add and resolve issue "iana". Appendix D. Resolved issues (to be removed by RFC Editor before publication) Issues that were either rejected or resolved in this version of this document. D.1. iana Type: change julian.reschke@greenbytes.de (2009-11-20): Use proper IANA registration template. Appendix E. Open issues (to be removed by RFC Editor prior to publication) E.1. edit Type: edit julian.reschke@greenbytes.de (2009-11-19): Umbrella issue for editorial fixes/enhancements. Authors' Addresses Al Brown IBM 3565 Harbor Blvd Costa Mesa, California 92626 US Email: albertcbrown@us.ibm.com Brown, et al. Expires May 24, 2010 [Page 10] Internet-Draft Version Navigation Link Relations November 2009 Geoffrey Clemm IBM 20 Maguire Road Lexington, MA 02421 US Email: geoffrey.clemm@us.ibm.com Julian F. Reschke (editor) greenbytes GmbH Hafenweg 16 Muenster, NW 48155 Germany Email: julian.reschke@greenbytes.de URI: http://greenbytes.de/tech/webdav/ Brown, et al. Expires May 24, 2010 [Page 11]