greenbytes GmbH

Salzmannstrasse 152 MuensterNW48159 Germany +49 251 2807760 +49 251 2807761 julian.reschke@greenbytes.de http://www.greenbytes.de/tech/webdav/

In many cases, a versioning-aware client might want to display/include the URI of the version it's editing while it's being edited. For instance, an editor might include this as meta information, or the author of a document might want to know the URI of the version before it's checked in. A well-known example is the W3C way of referring to document versions in recommendations: it contains references to "the current version", to "this version" and to the "previous version". Something like this is currently impossible with WebDAV deltaV , as the version URI is determined at the time of CHECKIN. Distribution of this document is unlimited. Please send comments to the WebDAV versioning (delta-V) working group at ietf-dav-versioning@w3.org, which may be joined by sending a message with subject "subscribe" to ietf-dav-versioning-request@w3.org. Discussions of the delta-V working group are archived at URL: http://lists.w3.org/Archives/Public/ietf-dav-versioning/.

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 .

In many cases, a versioning-aware client might want to display/include the URI of the version it's editing while it's being edited. For instance, an editor might include this as meta information, or the author of a document might want to know the URI of the version before it's checked in. A well-known example is the W3C way of referring to document versions in recommendations: it contains references to "the current version", to "this version" and to the "previous version". Something like this is currently impossible with WebDAV deltaV , as the version URI is determined at the time of CHECKIN. This specification builds on the infrastructure provided by the WebDAV Versioning Protocol, adding support for servers willing to compute an "expected version URI" upon CHECKOUT, and using this URI at time of CHECKIN. This document defines an extension element that could ultimately become part of the WebDAV deltaV protocol. Being just an individual submission, it currently defines it in the proprietary namespace

http://sapportals.com/xmlns/cm/webdav

instead of the "DAV:" namespace. It uses a prefix of "cu:" for referring to elements in this namespace. However, WebDAV server and clients are free to use any prefix, provided that there is a namespace declaration that binds the prefix to the URI of the same namespace.

A client may ask for an "expected version URI" upon CHECKOUT. This is done by placing cu:compute-expected-version-URI as top-level element into the request body. The server is free to either ignore the request, or to return it's best guess about what the URI for a version resource created upon CHECKIN would be. The client can detect the "expected version URI" by parsing the response body for a top-level element called cu:expected-version-URI.

>>Request ]]>

>>Response http://repo.webdav.org/his/23/ver/32 ]]>

In this example, the server was able to compute the "expected version URI" and returned it in the cu:expected-version-URI element.

>>Request ]]>

>>Response

In this case, no response body was returned, and thus no "expected version URI" is available. Simarily, the server may also return

>>Response ...other content... ]]>

where a response body is available, but it doesn't contain the cu:expected-version-URI element.

A client may submit the "expected version URI" (obtained during CHECKOUT) upon a CHECKIN by placing it into a top-level cu:expected-version-URI element in the request body. A server may simply ignore the presence of this information or use the information and try to checkin the resource using the "expected version URI" as location for the version resource. A failure to create a version resource at the "expected version URI" MUST cause the operation to fail with a status code of 403 (forbidden) and a response body containing the top-level element cu:cannot-assign-expected-version-URI. In addition, a server MAY return a new "expected version URI" in it's response body.

>>Request http://repo.webdav.org/his/23/ver/32 ]]>

>>Response

Note that the client can not rely on the server signaling an error if the expected version URI could not be applied. It will have to compare the URI returned in the HTTP "Location" header with the requested version URI, and in the case of mismatch it MAY have to report the situation to the user.

>>Request http://repo.webdav.org/his/23/ver/32 ]]>

>>Response http://repo.webdav.org/his/23/ver/33 ]]>

This specification does introduce new protocol elements for the request and response bodies for CHECKIN and CHECKOUT. Clients not aware of this specification will never submit the new protocol elements in a request and therefore never will see the new response elements. Servers not aware of this specification will ignore the additional two request body elements which is legal behaviour according to this protocol (indicating that the protocol extension is not available).

This proposal builds on , and inherits its internationalizability.

This proposal does not introduce any new IANA considerations, since it does not specify any new namespaces (in the general sense), but merely uses existing ones.

To be supplied by the RFC Editor.

To be supplied by the RFC Editor.

Harvard University

1350 Mass. Ave. Cambridge MA 02138 +1 617 495 3864 sob@harvard.edu

General keyword In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. Authors who follow these guidelines should incorporate this phrase near the beginning of their document: 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 RFC 2119. Note that the force of these words is modified by the requirement level of the document in which they are used. Microsoft Corporation

yarong@microsoft.com

Dept. Of Information and Computer Science, University of California, Irvine

ejw@ics.uci.edu

Netscape

asad@netscape.com

Novell

srcarter@novell.com

Novell

dcjensen@novell.com

Rational Software

geoffrey.clemm@rational.com

IBM

jamsden@us.ibm.com

IBM

tim_ellison@uk.ibm.com

Microsoft

ckaler@microsoft.com

UC Santa Cruz, Dept. of Computer Science

ejw@cse.ucsc.edu

Made the document element for responses upon failed CHECKIN DAV:error rather than DAV:checkin-response. Updated reference to . Moved extension elements out of DAV: namespace. Changed examples to explicitly use utf-8 encoding for HTTP content type and XML encoding. Globally replaced the term "CHECKIN URI" by "version URI" Added note about how to discover whether the server actually applied the expected version URI. Made sure artwork (figures) fits into 72 columns.