Network Working Group J. F. Reschke
Internet Draft greenbytes
Expires: November 2002 May 2002
Computing the CHECKIN URI in WebDAV versioning
draft-reschke-deltav-compute-checkin-uri-02
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. 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 in November 2002.
Copyright Notice
Copyright (C) The Internet Society (2002). 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 WebDAV versioning [RFC3253], as the version URI is
Reschke Expires November 2002 [Page 1]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
determined at the time of CHECKIN.
Distribution of this document is unlimited. Please send comments to
the WebDAV versioning (delta-V) mailing list 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 mailing list are archived at URL:
http://lists.w3.org/Archives/Public/ietf-dav-versioning/.
Reschke Expires November 2002 [Page 2]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
Table of Contents
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . 3
1 Notational Conventions . . . . . . . . . . . . . . . . . . . . 4
2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 Changes for CHECKOUT method (when applied to a version-
controlled resource) . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Example for successful CHECKOUT with computed version URI
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 Example for successful CHECKOUT without computed version
URI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4 Changes for CHECKIN method (when applied to a version-
controlled resource) . . . . . . . . . . . . . . . . . . . . . . 9
4.1 Example for successful CHECKIN with computed version URI . 9
4.2 Example for failed CHECKIN with computed version URI . . . 10
5 Compatibility Considerations . . . . . . . . . . . . . . . . . 12
6 Internationalization Considerations . . . . . . . . . . . . . . 13
7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14
8 Copyright . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9 Intellectual Property . . . . . . . . . . . . . . . . . . . . . 16
References . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17
A Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 18
A.1 Since 'draft-reschke-deltav-compute-checkin-uri-00' . . . . 18
A.2 Since 'draft-reschke-deltav-compute-checkin-uri-01' . . . . 18
Reschke Expires November 2002 [Page 3]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
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].
Reschke Expires November 2002 [Page 4]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
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 WebDAV versioning[RFC3253], 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 versioning 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.
Reschke Expires November 2002 [Page 5]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
3 Changes for CHECKOUT method (when applied to a version-controlled
resource)
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.
Additional Marshalling:
Presence of the cu:compute-expected-version-URI as top-level
element in the request body indicates that the server SHOULD
compute the "expected version URI". 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. Absence of this element (or absence of a response body)
indicates that the server is not able to compute the URI.
3.1 Example for successful CHECKOUT with computed version URI
>>Request
CHECKOUT /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:checkout xmlns:D="DAV:"
xmlns:cu="http://sapportals.com/xmlns/cm/webdav">
<cu:compute-expected-version-URI />
</D:checkout>
>>Response
HTTP/1.1 200 OK
Cache-Control: no-cache
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Reschke Expires November 2002 [Page 6]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
<?xml version="1.0" encoding="utf-8" ?>
<D:checkout-response xmlns:D="DAV:"
xmlns:cu="http://sapportals.com/xmlns/cm/webdav">
<cu:expected-version-URI
>http://repo.webdav.org/his/23/ver/32</cu:expected-version-URI>
</D:checkout-response>
In this example, the server was able to compute the "expected version
URI" and returned it in the cu:expected-version-URI element.
3.2 Example for successful CHECKOUT without computed version URI
>>Request
CHECKOUT /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:checkout xmlns:D="DAV:"
xmlns:cu="http://sapportals.com/xmlns/cm/webdav">
<cu: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
version URI" is available. Simarily, the server may also return
>>Response
HTTP/1.1 200 OK
Cache-Control: no-cache
Content-Type: text/xml; charset="utf-8"
Reschke Expires November 2002 [Page 7]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:checkout-response xmlns:D="DAV:">
...other content...
</D:checkout-response>
where a response body is available, but it doesn't contain the
cu:expected-version-URI element.
Reschke Expires November 2002 [Page 8]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
4 Changes for CHECKIN method (when applied to a version-controlled
resource)
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
o simply ignore the presence of this information or
o 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.
Additional Marshalling:
A top-level element cu:expected-version-URI, when present,
indicates the client's expectation about the URI of the version
that will be created by the CHECKIN operation.
Upon failure, the server MAY return a new "expected version URI"
in the DAV:error response body using the element cu:expected-
version-URI.
Additional Preconditions:
(cu:can-assign-expected-version-URI): the server must be able to
use the specified URI for the version that is going to be created
by the CHECKIN operation.
4.1 Example for successful CHECKIN with computed version URI
>>Request
CHECKIN /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:checkin xmlns:D="DAV:"
xmlns:cu="http://sapportals.com/xmlns/cm/webdav">
<cu:expected-version-URI
>http://repo.webdav.org/his/23/ver/32</cu:expected-version-URI>
Reschke Expires November 2002 [Page 9]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
</D:checkin>
>>Response
HTTP/1.1 201 Created
Location: http://repo.webdav.org/his/23/ver/32
Cache-Control: no-cache
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.
4.2 Example for failed CHECKIN with computed version URI
>>Request
CHECKIN /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:checkin xmlns:D="DAV:"
xmlns:cu="http://sapportals.com/xmlns/cm/webdav">
<cu:expected-version-URI
>http://repo.webdav.org/his/23/ver/32</cu:expected-version-URI>
</D:checkin>
>>Response
HTTP/1.1 403 Forbidden
Cache-Control: no-cache
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
Reschke Expires November 2002 [Page 10]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
<D:error xmlns:D="DAV:"
xmlns:cu="http://sapportals.com/xmlns/cm/webdav">
<cu:can-assign-expected-version-URI />
<cu:expected-version-URI
>http://repo.webdav.org/his/23/ver/33</cu:expected-version-URI>
</D:error>
Note that 403 (Forbidden) is returned because subsequent request with
the same expected version URI will always fail.
Reschke Expires November 2002 [Page 11]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
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).
Reschke Expires November 2002 [Page 12]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
6 Internationalization Considerations
This proposal builds on [RFC3253], and inherits its
internationalizability.
Reschke Expires November 2002 [Page 13]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
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.
Reschke Expires November 2002 [Page 14]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
8 Copyright
To be supplied by the RFC Editor.
Reschke Expires November 2002 [Page 15]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
9 Intellectual Property
To be supplied by the RFC Editor.
Reschke Expires November 2002 [Page 16]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
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.R. and
Jensen, D., "HTTP Extensions for Distributed Authoring --
WEBDAV", RFC 2518, February 1999.
[RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C. and
Whitehead, J., "Versioning Extensions to WebDAV", RFC
3253, March 2002.
Author's Address
Julian F. Reschke
greenbytes GmbH
Salzmannstrasse 152
Muenster, NW 48159
Germany
Phone: +49 251 2807760
Fax: +49 251 2807761
EMail: julian.reschke@greenbytes.de
URI: http://www.greenbytes.de/tech/webdav/
Reschke Expires November 2002 [Page 17]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
A Change Log
A.1 Since 'draft-reschke-deltav-compute-checkin-uri-00'
Made the document element for responses upon failed CHECKIN DAV:error
rather than DAV:checkin-response.
Updated reference to [RFC3253].
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.
A.2 Since 'draft-reschke-deltav-compute-checkin-uri-01'
Updated abstract not to refer to DeltaV WG anymore. Use "WebDAV
versioning" instead of "deltaV".
Changed descriptions to use RFC3253's Marshalling/Precondition
format. Changed name of cu:cannot-assign-expected-version-URI to
cu:can-assign-expected-version-URI as this is a precondition.
Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
Reschke Expires November 2002 [Page 18]
Internet Draft CHECKIN URI in WebDAV versioning May 2002
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC editor function is currently provided by the
Internet Society.
Reschke Expires November 2002 [Page 19]