Network Working Group A. Brown
Internet-Draft G. Clemm
Intended status: Informational IBM
Expires: May 23, 2010 J. Reschke, Ed.
greenbytes
November 19, 2009
Link Relations for Simple Version Navigation
draft-brown-versioning-link-relations-02
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
(<http://www.imc.org/atom-syntax/>).
Status of this Memo
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Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Link Relations . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . . 5
Appendix A. Relationship to Java Content Repository (JCR) and
WebDAV . . . . . . . . . . . . . . . . . . . . . . . . 5
A.1. Example: Use of Link Relations in HTTP Link Header . . . . 6
Appendix B. Contributors . . . . . . . . . . . . . . . . . . . . . 8
Appendix C. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . . 8
C.1. Since draft-brown-link-relations-00 . . . . . . . . . . . . 8
C.2. Since draft-brown-link-relations-01 . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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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:
version-history
When included on a versioned resource, this link points to a
resource containing the version history for this resource.
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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.
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.
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.
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. 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).
5. IANA Considerations
The link relations defined in Section 3 are to be registered by IANA
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per [RFC4287]. [[lhdraft: Will be updated to follow
[draft-nottingham-http-link-header] once approved by the IESG.
--jre]]
All link relations defined in this document will have the following
expected display characteristics:
Undefined; this relation can be used for background processing or
to provide extended functionality without displaying its value.
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,
<http://www.day.com/specs/jcr/2.0/>.
[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.
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
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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).
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]).
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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: </system/v/84345634/1>; rel=latest-version;
anchor=</docs/test.txt>
Link: </system/vh/84345634>; rel=version-history;
anchor=</docs/test.txt>
(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
>> Response:
HTTP/1.1 200 OK
Content-Type: text/plain; charset=UTF-8
Content-Length: 12345
Link: </system/v/84345634/1>; rel=latest-version
Link: </system/vh/84345634>; rel=version-history
After creating more versions, following the latest-version would then
expose predecessors of a version:
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>> 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: </system/v/84345634/2>; 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.
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.
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Authors' Addresses
Al Brown
IBM
3565 Harbor Blvd
Costa Mesa, California 92626
US
Email: albertcbrown@us.ibm.com
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/
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