Network Working Group J. Reschke
Internet-Draft greenbytes
Expires: April 3, 2002 October 3, 2001
Computing the CHECKIN URI in WebDAV versioning
draft-reschke-deltav-compute-checkin-uri-00
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
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
the current draft version of WebDAV deltaV [deltaV], as the version
URI is determined at the time of CHECKIN.
Distribution of this document is unlimited. Please send comments to
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the WebDAV versioning (delta-V) working group at ietf-dav-
versioning@w3.org[1], which may be joined by sending a message with
subject "subscribe" to ietf-dav-versioning-request@w3.org[2].
Discussions of the delta-V working group are archived at URL: http://
lists.w3.org/Archives/Public/ietf-dav-versioning/.
Table of Contents
1. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Changes for CHECKOUT method (when applied to a
version-controlled resource) . . . . . . . . . . . . . . . . . 5
3.1 Example for successful CHECKOUT with computed-checkin-URI . . 5
3.2 Example for successful CHECKOUT without computed-checkin-URI . 6
4. Changes for CHECKIN method (when applied to a
version-controlled resource) . . . . . . . . . . . . . . . . . 7
4.1 Example for successful CHECKIN with computed-checkin-URI . . . 7
4.2 Example for failed CHECKIN with computed-checkin-URI . . . . . 8
5. Compatibility Considerations . . . . . . . . . . . . . . . . . 9
6. Internationalization Considerations . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Copyright . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9. Intellectual Property . . . . . . . . . . . . . . . . . . . . 13
References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 14
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 15
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1. 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 [RFC2119].
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2. Introduction
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
the current draft version of WebDAV deltaV [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 CHECKIN URI" upon CHECKOUT, and using this URI
at time of CHECKIN.
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3. Changes for CHECKOUT method (when applied to a version-controlled
resource)
A client may ask for an "expected CHECKIN URI" upon CHECKOUT. This
is done by placing DAV:compute-expected-checkin-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 CHECKIN URI" by parsing the
response body for a top-level element called DAV:expected-checkin-
URI.
3.1 Example for successful CHECKOUT with computed-checkin-URI
>>Request
CHECKOUT /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml
Content-Length: xxxx
<D:checkout xmlns:D="DAV:">
<D:compute-expected-version-URI />
</D:checkout>
>>Response
HTTP/1.1 200 OK
Cache-Control: no-cache
Content-Type: text/xml
Content-Length: xxxx
<D:checkout-response xmlns:D="DAV:">
<D:expected-version-URI>http://repo.webdav.org/his/23/ver/32</D:expected-version-URI>
</D:checkout-response>
In this example, the server was able to compute the "expected CHECKIN
URI" and returned it in the DAV:expected-version-URI element.
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3.2 Example for successful CHECKOUT without computed-checkin-URI
>>Request
CHECKOUT /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml
Content-Length: xxxx
<D:checkout xmlns:D="DAV:">
<D:compute-expected-version-URI />
</D:checkout>
>>Response
HTTP/1.1 200 OK
Cache-Control: no-cache
In this case, no response body was returned, and thus no "expected
CHECKIN URI" is available. Simarily, the server may also return
>>Response
HTTP/1.1 200 OK
Cache-Control: no-cache
Content-Type: text/xml
Content-Length: xxxx
<D:checkout-response xmlns:D="DAV:">
...other content...
</D:checkout-response>
where a response body is available, but it doesn't contain the
DAV:expected-checkin-URI element.
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4. Changes for CHECKIN method (when applied to a version-controlled
resource)
A client may submit the "expected CHECKIN URI" (obtained during
CHECKOUT) upon a CHECKIN by placing it into a top-level DAV:expected-
checkin-URI element in the request body. A server may
o simply ignore the presence of this information or
o use the information and try to checkin the resource using the
"expected checkin URI" as location for the version resource. A
failure to create a version resource at the "expected checkin URI"
MUST cause the operation to fail with a status code of 403
(forbidden) and a response body containing the top-level element
DAV:cannot-assign-expected-version-URI. In addition, a server MAY
return a new "expected checkin URI" in it's response body.
4.1 Example for successful CHECKIN with computed-checkin-URI
>>Request
CHECKIN /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml
Content-Length: xxxx
<D:checkin xmlns:D="DAV:">
<D:expected-version-URI>http://repo.webdav.org/his/23/ver/32</D:expected-version-URI>
</D:checkin>
>>Response
HTTP/1.1 201 Created
Location: http://repo.webdav.org/his/23/ver/32
Cache-Control: no-cache
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4.2 Example for failed CHECKIN with computed-checkin-URI
>>Request
CHECKIN /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml
Content-Length: xxxx
<D:checkin xmlns:D="DAV:">
<D:expected-version-URI>http://repo.webdav.org/his/23/ver/32</D:expected-version-URI>
</D:checkin>
>>Response
HTTP/1.1 403 Forbidden
Cache-Control: no-cache
Content-Type: text/xml
Content-Length: xxxx
<D:checkin-response xmlns:D="DAV:">
<D:cannot-assign-expected-version-URI />
<D:expected-version-URI>http://repo.webdav.org/his/23/ver/33</D:expected-version-URI>
</D:checkin-response>
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5. Compatibility Considerations
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).
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6. Internationalization Considerations
This proposal builds on [deltaV], and inherits its
internationalizability.
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7. IANA Considerations
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.
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8. Copyright
To be supplied by the RFC Editor.
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9. Intellectual Property
To be supplied by the RFC Editor.
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References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2518] Goland, Y., Whitehead, E., Faizi, A., Carter, S. and D.
Jensen, "HTTP Extensions for Distributed Authoring --
WEBDAV", RFC 2518, February 1999.
[deltaV] Clemm, G., Amsden, J., Ellison, T., Kaler, C. and J.
Whitehead, "Versioning Extensions to WebDAV", ID draft-
ietf-deltav-versioning-18, September 2001, <http://
www.webdav.org/deltav/protocol/draft-ietf-deltav-
versioning-18.htm>.
[1] <mailto:ietf-dav-versioning@w3.org>
[2] <mailto:ietf-dav-versioning-request@w3.org?subject=subscribe>
Author's Address
Julian F. Reschke
greenbytes GmbH
Salzmannstrasse 152
Muenster, NW 48159
Germany
EMail: julian.reschke@greenbytes.de
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