Computing the CHECKIN URI in WebDAV versioninggreenbytes GmbHHafenweg 16MuensterNW48155Germany+49 251 2807760+49 251 2807761julian.reschke@greenbytes.dehttp://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 versioning ,
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) 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/.
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
,
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.
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 .
A client may ask for an "expected version URI" upon CHECKOUT (and the
CHECKIN variant with DAV:keep-checked-out request element).
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.
<!ELEMENT cu:compute-expected-version-URI EMPTY >
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.
<!ELEMENT cu:expected-version-URI (href) >
>>Request
CHECKOUT /foo.html HTTP/1.1
Host: www.example.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
<?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>
<D:href>http://repo.example.org/his/23/ver/32</D:href>
</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.
>>Request
CHECKOUT /foo.html HTTP/1.1
Host: www.example.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"
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.
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.
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):
if the server does support the cu:compute-expected-version-URI extension
upon CHECKOUT, it MUST create the new version at the URI specified in the cu:expected-version-URI
or otherwise fail the request.
>>Request
CHECKIN /foo.html HTTP/1.1
Host: www.example.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>
<D:href>http://repo.example.org/his/23/ver/32</D:href>
</cu:expected-version-URI>
</D:checkin>
>>Response
HTTP/1.1 201 Created
Location: http://repo.example.org/his/23/ver/32
Cache-Control: no-cache
>>Request
CHECKIN /foo.html HTTP/1.1
Host: www.example.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>
<D:href>http://repo.example.org/his/23/ver/32</D:href>
</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" ?>
<D:error xmlns:D="DAV:"
xmlns:cu="http://sapportals.com/xmlns/cm/webdav">
<cu:can-assign-expected-version-URI />
<cu:expected-version-URI>
<D:href>http://repo.example.org/his/23/ver/33</D:href>
</cu:expected-version-URI>
</D:error>
Note that 403 (Forbidden) is returned because subsequent request with the
same expected version URI will always fail.
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.
Key words for use in RFCs to Indicate Requirement LevelsHarvard University1350 Mass. Ave.CambridgeMA 02138+1 617 495 3864sob@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.
HTTP Extensions for Distributed Authoring -- WEBDAVMicrosoft Corporationyarong@microsoft.comDept. Of Information and Computer Science, University of California, Irvineejw@ics.uci.eduNetscapeasad@netscape.comNovellsrcarter@novell.comNovelldcjensen@novell.comVersioning Extensions to WebDAVRational Softwaregeoffrey.clemm@rational.comIBMjamsden@us.ibm.comIBMtim_ellison@uk.ibm.comMicrosoftckaler@microsoft.comUC Santa Cruz, Dept. of Computer Scienceejw@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.
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.
Update marshalling to use DAV:href as container for URIs.
Clarify that the extension applies to CHECKOUT on version resources and
to CHECKIN/DAV:keep-checked-out as well.
Replaced domain names in examples according to RFC2606: "webdav.org" by
"example.org".
Remove superfluous IP and copyright sections. Swap "Introduction" and
"Notation" sections. Require server to support both extensions to
make behaviour more predictable.