rfc8144
Internet Engineering Task Force (IETF) K. Murchison
Request for Comments: 8144 CMU
Updates: 7240 April 2017
Category: Standards Track
ISSN: 2070-1721
Use of the Prefer Header Field in
Web Distributed Authoring and Versioning (WebDAV)
Abstract
This document defines how the Prefer header field (RFC 7240) can be
used by a Web Distributed Authoring and Versioning (WebDAV) client to
request that certain behaviors be employed by a server while
constructing a response to a request. Furthermore, it defines the
new "depth-noroot" preference.
This document updates RFC 7240.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8144.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Murchison Standards Track [Page 1]
RFC 8144 Prefer Header Field in WebDAV April 2017
Table of Contents
1. Introduction ....................................................3
1.1. Notational Conventions .....................................3
2. Reducing WebDAV Response Verbosity with "return=minimal" ........3
2.1. Minimal PROPFIND and REPORT Responses ......................4
2.2. Minimal PROPPATCH Response .................................5
2.3. Minimal MKCALENDAR and MKCOL Responses .....................5
3. Reducing WebDAV Roundtrips with "return=representation" .........6
3.1. Successful State-Changing Requests .........................6
3.2. Unsuccessful Conditional State-Changing Requests ...........6
4. The "depth-noroot" Processing Preference ........................7
5. Security Considerations .........................................7
6. IANA Considerations .............................................8
6.1. Preference Registration ....................................8
6.2. Method References ..........................................8
6.3. Status Code References .....................................9
7. References ......................................................9
7.1. Normative References .......................................9
7.2. Informative References ....................................10
Appendix A. The Brief and Extended Depth Header Fields ...........12
Appendix B. Examples .............................................12
B.1. PROPFIND ..................................................12
B.2. REPORT ....................................................16
B.3. PROPPATCH .................................................21
B.4. MKCOL .....................................................22
B.5. POST ......................................................23
B.6. PUT .......................................................27
Acknowledgements ..................................................28
Author's Address ..................................................28
Murchison Standards Track [Page 2]
RFC 8144 Prefer Header Field in WebDAV April 2017
1. Introduction
[RFC7240] defines the Prefer header field and the "return=minimal"
preference, which indicate that a client wishes for the server to
return a minimal response to a successful request but states that
what constitutes an appropriate minimal response is left solely to
the discretion of the server. Section 2 of this specification
defines precisely what is expected of a server when constructing
minimal responses to successful WebDAV [RFC4918] requests.
[RFC7240] also defines the "return=representation" preference, which
indicates that a client wishes for the server to include an entity
representing the current state of the resource in the response to a
successful request. Section 3 of this specification makes
recommendations on when this preference should be used by clients and
extends its applicability to 412 (Precondition Failed) [RFC7232]
responses.
Finally, Section 4 of this specification defines the "depth-noroot"
preference that can be used with HTTP methods that support the Depth
header field.
1.1. 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].
This document references XML element types in the "DAV:" [RFC4918],
"urn:ietf:params:xml:ns:caldav" [RFC4791], and
"urn:ietf:params:xml:ns:carddav" [RFC6352] namespaces outside of the
context of an XML fragment. When doing so, the strings "DAV:",
"CALDAV:", and "CARDDAV:" will be prepended to the XML element types,
respectively.
2. Reducing WebDAV Response Verbosity with "return=minimal"
Some payload bodies in responses to WebDAV requests, such as 207
(Multi-Status) [RFC4918] responses, can be quite verbose or even
unnecessary at times. This specification defines how the Prefer
header field, in conjunction with its "return=minimal" preference,
can be used by clients to reduce the verbosity of such responses by
requesting that the server omit those portions of the response that
can be inferred by their absence.
Murchison Standards Track [Page 3]
RFC 8144 Prefer Header Field in WebDAV April 2017
2.1. Minimal PROPFIND and REPORT Responses
When a PROPFIND [RFC4918] request, or a REPORT [RFC3253] request
whose report type results in a 207 (Multi-Status) response, contains
a Prefer header field with a preference of "return=minimal", the
server SHOULD omit all DAV:propstat XML elements containing a
DAV:status XML element of value 404 (Not Found) [RFC7231] from the
207 (Multi-Status) response. If the omission of such a DAV:propstat
element would result in a DAV:response XML element containing zero
DAV:propstat elements, the server MUST substitute one of the
following in its place:
o a DAV:propstat element consisting of an empty DAV:prop element and
a DAV:status element of value 200 (OK) [RFC7231]
o a DAV:status element of value 200 (OK)
The following report types are candidates that could benefit from use
of the "return=minimal" preference. NOTE: This list is not intended
to be normative or exhaustive.
o DAV:expand-property [RFC3253]
o DAV:acl-principal-prop-set [RFC3744]
o DAV:principal-property-search [RFC3744]
o DAV:sync-collection [RFC6578]
o CALDAV:calendar-query [RFC4791]
o CALDAV:calendar-multiget [RFC4791]
o CARDDAV:addressbook-query [RFC6352]
o CARDDAV:addressbook-multiget [RFC6352]
See Appendices B.1 and B.2 for examples.
Murchison Standards Track [Page 4]
RFC 8144 Prefer Header Field in WebDAV April 2017
2.2. Minimal PROPPATCH Response
When a PROPPATCH [RFC4918] request contains a Prefer header field
with a preference of "return=minimal", and all instructions are
processed successfully, the server SHOULD return one of the following
responses rather than a 207 (Multi-Status) response:
o 204 (No Content) [RFC7231]
o 200 (OK) [RFC7231] (preferably with a zero-length message body)
See Appendix B.3 for examples.
2.3. Minimal MKCALENDAR and MKCOL Responses
Both the MKCALENDAR [RFC4791] and Extended MKCOL [RFC5689]
specifications indicate that a server MAY return a message body in
response to a successful request. This specification explicitly
defines the intended behavior in the presence of the Prefer header
field.
When a MKCALENDAR or an extended MKCOL request contains a Prefer
header field with a preference of "return=minimal", and the
collection is created with all requested properties being set
successfully, the server SHOULD return a 201 (Created) [RFC7231]
response with an empty (zero-length) message body.
Note that the rationale for requiring that a minimal success response
have an empty body is twofold:
o [RFC4791], Section 5.3.1 states: "If a response body for a
successful request is included, it MUST be a CALDAV:mkcalendar-
response XML element."
o [RFC5689], Section 3 states: "When an empty response body is
returned with a success request status code, the client can assume
that all properties were set."
See Appendix B.4 for examples.
Murchison Standards Track [Page 5]
RFC 8144 Prefer Header Field in WebDAV April 2017
3. Reducing WebDAV Roundtrips with "return=representation"
[RFC7240] describes the "return=representation" preference as being
intended to provide a means of optimizing communication between the
client and server by eliminating the need for a subsequent GET
request to retrieve the current representation of the resource
following a modification. This preference is equally applicable to
situations where the server itself modifies a resource, and where a
resource has been modified by another client.
3.1. Successful State-Changing Requests
The state-changing methods PUT [RFC7231], COPY/MOVE [RFC4918], PATCH
[RFC5789], and POST [RFC5995] can be used to create or update a
resource. In some instances, such as with Calendaring Extensions to
WebDAV (CalDAV) Scheduling [RFC6638], the created or updated resource
representation may differ from the representation sent in the body of
the request or from that referenced by the effective request URI. In
cases where the client, upon receiving a 2xx (Successful) [RFC7231]
response to its state-changing request, would normally issue a
subsequent GET request to retrieve the current representation of the
resource, the client can instead include a Prefer header field with
the "return=representation" preference in the state-changing request.
When a state-changing request contains a Prefer header field with a
preference of "return=representation", and the resource is created or
updated successfully, the server SHOULD include an entity
representing the current state of the resource in the resulting 201
(Created) or 200 (OK) [RFC7231] response. In addition to coalescing
the create/update and retrieve operations into a single roundtrip, by
returning the current representation of the resource in the response,
the client will know that any changes to the resource were produced
by the server rather than a concurrent client, thus providing a level
of atomicity to the operation.
See Appendix B.5 for examples.
3.2. Unsuccessful Conditional State-Changing Requests
Frequently, clients using a state-changing method such as those
listed above will make them conditional by including either an
If-Match or an If-None-Match [RFC7232] header field in the request.
This is done to prevent the client from accidentally overwriting a
resource whose current state has been modified by another client
acting in parallel. In cases where the client, upon receiving a 412
(Precondition Failed) [RFC7232] response to its conditional state-
changing request, would normally issue a subsequent GET request to
retrieve the current representation of the resource, the client can
Murchison Standards Track [Page 6]
RFC 8144 Prefer Header Field in WebDAV April 2017
instead include a Prefer header field with the
"return=representation" preference in the conditional state-changing
request.
When a conditional state-changing request contains a Prefer header
field with a preference of "return=representation", and the specified
condition evaluates to false, the server SHOULD include an entity
representing the current state of the resource in the resulting 412
(Precondition Failed) [RFC7232] response.
See Appendix B.6 for examples.
4. The "depth-noroot" Processing Preference
The "depth-noroot" preference indicates that the client wishes for
the server to exclude the target (root) resource from processing by
the HTTP method and only apply the HTTP method to the target
resource's subordinate resources.
This preference is only intended to be used with HTTP methods whose
definitions explicitly provide support for the Depth [RFC4918] header
field. Furthermore, this preference only applies when the Depth
header field has a value of "1" or "infinity" (either implicitly or
explicitly).
The "depth-noroot" preference MAY be used in conjunction with the
"return=minimal" preference in a single request.
See Appendix B.1 for examples.
5. Security Considerations
No new security considerations are introduced by use of the Prefer
header field with WebDAV requests, beyond those discussed in
[RFC7240] and those already inherent in those requests.
Murchison Standards Track [Page 7]
RFC 8144 Prefer Header Field in WebDAV April 2017
6. IANA Considerations
6.1. Preference Registration
The following preference has been added to the HTTP Preferences
Registry defined in Section 5.1 of [RFC7240].
Preference: depth-noroot
Description: The "depth-noroot" preference indicates that the client
wishes for the server to exclude the target (root) resource from
processing by the HTTP method and only apply the HTTP method to
the target resource's subordinate resources.
Reference: RFC 8144, Section 4
Notes: This preference is only intended to be used with HTTP methods
whose definitions explicitly provide support for the Depth
[RFC4918] header field. Furthermore, this preference only applies
when the Depth header field has a value of "1" or "infinity"
(either implicitly or explicitly).
6.2. Method References
The following methods have had their references updated in the "HTTP
Method Registry" (http://www.iana.org/assignments/http-methods).
+------------+------+------------+----------------------------------+
| Method | Safe | Idempotent | References |
| Name | | | |
+------------+------+------------+----------------------------------+
| MKCALENDAR | no | yes | RFC 4791, Section 5.3.1; RFC |
| | | | 8144, Section 2.3 |
| MKCOL | no | yes | RFC 4918, Section 9.3; RFC 5689, |
| | | | Section 3; RFC 8144, Section 2.3 |
| PROPFIND | yes | yes | RFC 4918, Section 9.1; RFC 8144, |
| | | | Section 2.1 |
| PROPPATCH | no | yes | RFC 4918, Section 9.2; RFC 8144, |
| | | | Section 2.2 |
| REPORT | yes | yes | RFC 3253, Section 3.6; RFC 8144, |
| | | | Section 2.1 |
+------------+------+------------+----------------------------------+
Murchison Standards Track [Page 8]
RFC 8144 Prefer Header Field in WebDAV April 2017
6.3. Status Code References
The following status code has had its references updated in the "HTTP
Status Codes" registry (http://www.iana.org/assignments/http-status-
codes).
+-------+-------------------+---------------------------------------+
| Value | Description | References |
+-------+-------------------+---------------------------------------+
| 412 | Precondition | RFC 7232, Section 4.2; RFC 8144, |
| | Failed | Section 3.2 |
+-------+-------------------+---------------------------------------+
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J.
Whitehead, "Versioning Extensions to WebDAV (Web
Distributed Authoring and Versioning)", RFC 3253,
DOI 10.17487/RFC3253, March 2002,
<http://www.rfc-editor.org/info/rfc3253>.
[RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault,
"Calendaring Extensions to WebDAV (CalDAV)", RFC 4791,
DOI 10.17487/RFC4791, March 2007,
<http://www.rfc-editor.org/info/rfc4791>.
[RFC4918] Dusseault, L., Ed., "HTTP Extensions for Web Distributed
Authoring and Versioning (WebDAV)", RFC 4918,
DOI 10.17487/RFC4918, June 2007,
<http://www.rfc-editor.org/info/rfc4918>.
[RFC5689] Daboo, C., "Extended MKCOL for Web Distributed Authoring
and Versioning (WebDAV)", RFC 5689, DOI 10.17487/RFC5689,
September 2009, <http://www.rfc-editor.org/info/rfc5689>.
[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
RFC 5789, DOI 10.17487/RFC5789, March 2010,
<http://www.rfc-editor.org/info/rfc5789>.
Murchison Standards Track [Page 9]
RFC 8144 Prefer Header Field in WebDAV April 2017
[RFC5995] Reschke, J., "Using POST to Add Members to Web Distributed
Authoring and Versioning (WebDAV) Collections", RFC 5995,
DOI 10.17487/RFC5995, September 2010,
<http://www.rfc-editor.org/info/rfc5995>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<http://www.rfc-editor.org/info/rfc7231>.
[RFC7232] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Conditional Requests", RFC 7232,
DOI 10.17487/RFC7232, June 2014,
<http://www.rfc-editor.org/info/rfc7232>.
[RFC7240] Snell, J., "Prefer Header for HTTP", RFC 7240,
DOI 10.17487/RFC7240, June 2014,
<http://www.rfc-editor.org/info/rfc7240>.
7.2. Informative References
[MSDN.aa493854]
Microsoft Developer Network, "PROPPATCH Method", June
2006,
<http://msdn.microsoft.com/en-us/library/aa493854.aspx>.
[MSDN.aa563501]
Microsoft Developer Network, "Brief Header", June 2006,
<http://msdn.microsoft.com/en-us/library/aa563501.aspx>.
[MSDN.aa563950]
Microsoft Developer Network, "Depth Header", June 2006,
<http://msdn.microsoft.com/en-us/library/aa563950.aspx>.
[MSDN.aa580336]
Microsoft Developer Network, "PROPFIND Method", June 2006,
<http://msdn.microsoft.com/en-us/library/aa580336.aspx>.
[RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web
Distributed Authoring and Versioning (WebDAV) Access
Control Protocol", RFC 3744, DOI 10.17487/RFC3744, May
2004, <http://www.rfc-editor.org/info/rfc3744>.
[RFC6352] Daboo, C., "CardDAV: vCard Extensions to Web Distributed
Authoring and Versioning (WebDAV)", RFC 6352,
DOI 10.17487/RFC6352, August 2011,
<http://www.rfc-editor.org/info/rfc6352>.
Murchison Standards Track [Page 10]
RFC 8144 Prefer Header Field in WebDAV April 2017
[RFC6578] Daboo, C. and A. Quillaud, "Collection Synchronization for
Web Distributed Authoring and Versioning (WebDAV)",
RFC 6578, DOI 10.17487/RFC6578, March 2012,
<http://www.rfc-editor.org/info/rfc6578>.
[RFC6638] Daboo, C. and B. Desruisseaux, "Scheduling Extensions to
CalDAV", RFC 6638, DOI 10.17487/RFC6638, June 2012,
<http://www.rfc-editor.org/info/rfc6638>.
Murchison Standards Track [Page 11]
RFC 8144 Prefer Header Field in WebDAV April 2017
Appendix A. The Brief and Extended Depth Header Fields
This document is based heavily on the Brief [MSDN.aa563501] and
extended Depth [MSDN.aa563950] header fields. The behaviors
described in Sections 2.1 and 2.2 are identical to those provided by
the Brief header field when used with the PROPFIND [MSDN.aa580336]
and PROPPATCH [MSDN.aa493854] methods, respectively. The behavior
described in Section 4 is identical to that provided by the
"1,noroot" [MSDN.aa563950] and "infinity,noroot" [MSDN.aa563950]
Depth header field values.
Client and server implementations that already support the Brief
header field can add support for the "return=minimal" preference with
nominal effort.
If a server supporting the Prefer header field receives both the
Brief and Prefer header fields in a request, clients can expect the
server to ignore the Brief header field and only use the Prefer
header field preferences.
Appendix B. Examples
B.1. PROPFIND
B.1.1. Typical PROPFIND Request/Response with Depth:1
This example tries to fetch one known and one unknown property from
child resources.
>> Request <<
PROPFIND /container/ HTTP/1.1
Host: webdav.example.com
Content-Type: application/xml; charset=utf-8
Content-Length: 189
Depth: 1
<?xml version="1.0" encoding="UTF-8"?>
<D:propfind xmlns:D="DAV:" xmlns:X="http://ns.example.com/foobar/">
<D:prop>
<D:resourcetype/>
<X:foobar/>
</D:prop>
</D:propfind>
>> Response <<
HTTP/1.1 207 Multi-Status
Murchison Standards Track [Page 12]
RFC 8144 Prefer Header Field in WebDAV April 2017
Content-Type: application/xml; charset=utf-8
Content-Length: 1722
<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:"
xmlns:X="http://ns.example.com/foobar/">
<D:response>
<D:href>/container/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:collection/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop>
<X:foobar/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/container/work/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:collection/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop>
<X:foobar/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/container/home/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:collection/>
</D:resourcetype>
</D:prop>
Murchison Standards Track [Page 13]
RFC 8144 Prefer Header Field in WebDAV April 2017
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop>
<X:foobar/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/container/foo.txt</D:href>
<D:propstat>
<D:prop>
<D:resourcetype/>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop>
<X:foobar/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
</D:multistatus>
B.1.2. Minimal PROPFIND Request/Response with Depth:1
This example tries to fetch one known and one unknown property from
child resources only.
>> Request <<
PROPFIND /container/ HTTP/1.1
Host: webdav.example.com
Content-Type: application/xml; charset=utf-8
Content-Length: 189
Depth: 1
Prefer: return=minimal, depth-noroot
<?xml version="1.0" encoding="UTF-8"?>
<D:propfind xmlns:D="DAV:" xmlns:X="http://ns.example.com/foobar/">
<D:prop>
<D:resourcetype/>
<X:foobar/>
</D:prop>
</D:propfind>
Murchison Standards Track [Page 14]
RFC 8144 Prefer Header Field in WebDAV April 2017
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: application/xml; charset=utf-8
Content-Length: 837
Preference-Applied: return=minimal, depth-noroot
<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>/container/work/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:collection/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/container/home/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:collection/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/container/foo.txt</D:href>
<D:propstat>
<D:prop>
<D:resourcetype/>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
Murchison Standards Track [Page 15]
RFC 8144 Prefer Header Field in WebDAV April 2017
B.1.3. Minimal PROPFIND Request/Response with an Empty DAV:propstat
Element
This example tries to fetch an unknown property from a collection.
>> Request <<
PROPFIND /container/ HTTP/1.1
Host: webdav.example.com
Content-Type: application/xml; charset=utf-8
Content-Length: 166
Prefer: return=minimal
<?xml version="1.0" encoding="UTF-8"?>
<D:propfind xmlns:D="DAV:" xmlns:X="http://ns.example.com/foobar/">
<D:prop>
<X:foobar/>
</D:prop>
</D:propfind>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: application/xml; charset=utf-8
Content-Length: 255
Preference-Applied: return=minimal
<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>/container/</D:href>
<D:propstat>
<D:prop/>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
B.2. REPORT
B.2.1. Typical REPORT Request/Response
This example tries to fetch an unknown property from several
resources via the DAV:expand-property [RFC3253] REPORT type.
>> Request <<
REPORT /dav/principals/ HTTP/1.1
Murchison Standards Track [Page 16]
RFC 8144 Prefer Header Field in WebDAV April 2017
Host: webdav.example.com
Content-type: text/xml; charset=utf-8
Content-length: 847
<?xml version="1.0" encoding="utf-8"?>
<D:expand-property xmlns:D="DAV:">
<D:property name="current-user-principal">
<D:property name="resourcetype"/>
<D:property name="displayname"/>
<D:property name="foobar"
namespace="http://ns.example.com/foobar"/>
<D:property name="calendar-home-set"
namespace="urn:ietf:params:xml:ns:caldav">
<D:property name="resourcetype"/>
<D:property name="foobar"
namespace="http://ns.example.com/foobar"/>
</D:property>
<D:property name="addressbook-home-set"
namespace="urn:ietf:params:xml:ns:carddav">
<D:property name="resourcetype"/>
<D:property name="foobar"
namespace="http://ns.example.com/foobar"/>
</D:property>
</D:property>
</D:expand-property>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: application/xml; charset=utf-8
Content-Length: 2664
<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:"
xmlns:C="urn:ietf:params:xml:ns:caldav"
xmlns:R="urn:ietf:params:xml:ns:carddav"
xmlns:X="http://ns.example.com/foobar">
<D:response>
<D:href>/dav/principals/</D:href>
<D:propstat>
<D:prop>
<D:current-user-principal>
<D:response>
<D:href>/dav/principals/user/ken/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:principal/>
Murchison Standards Track [Page 17]
RFC 8144 Prefer Header Field in WebDAV April 2017
</D:resourcetype>
<D:displayname>ken</D:displayname>
<C:calendar-home-set>
<D:response>
<D:href>/dav/calendars/user/ken/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:collection/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop>
<X:foobar/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
</C:calendar-home-set>
<R:addressbook-home-set>
<D:response>
<D:href>/dav/addressbooks/user/ken/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:collection/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop>
<X:foobar/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
</R:addressbook-home-set>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop>
<X:foobar/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
Murchison Standards Track [Page 18]
RFC 8144 Prefer Header Field in WebDAV April 2017
</D:propstat>
</D:response>
</D:current-user-principal>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
B.2.2. Minimal REPORT Request/Response
This example tries to fetch an unknown property from several
resources via the DAV:expand-property [RFC3253] REPORT type.
>> Request <<
REPORT /dav/principals/ HTTP/1.1
Host: webdav.example.com
Content-Type: application/xml; charset=utf-8
Content-Length: 847
Prefer: return=minimal
<?xml version="1.0" encoding="utf-8"?>
<D:expand-property xmlns:D="DAV:">
<D:property name="current-user-principal">
<D:property name="resourcetype"/>
<D:property name="displayname"/>
<D:property name="foobar"
namespace="http://ns.example.com/foobar"/>
<D:property name="calendar-home-set"
namespace="urn:ietf:params:xml:ns:caldav">
<D:property name="resourcetype"/>
<D:property name="foobar"
namespace="http://ns.example.com/foobar"/>
</D:property>
<D:property name="addressbook-home-set"
namespace="urn:ietf:params:xml:ns:carddav">
<D:property name="resourcetype"/>
<D:property name="foobar"
namespace="http://ns.example.com/foobar"/>
</D:property>
</D:property>
</D:expand-property>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: application/xml; charset=utf-8
Murchison Standards Track [Page 19]
RFC 8144 Prefer Header Field in WebDAV April 2017
Content-Length: 1998
Preference-Applied: return=minimal
<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:"
xmlns:C="urn:ietf:params:xml:ns:caldav"
xmlns:R="urn:ietf:params:xml:ns:carddav"
xmlns:X="http://ns.example.com/foobar">
<D:response>
<D:href>/dav/principals/</D:href>
<D:propstat>
<D:prop>
<D:current-user-principal>
<D:response>
<D:href>/dav/principals/user/ken/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:principal/>
</D:resourcetype>
<D:displayname>ken</D:displayname>
<C:calendar-home-set>
<D:response>
<D:href>/dav/calendars/user/ken/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:collection/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</C:calendar-home-set>
<R:addressbook-home-set>
<D:response>
<D:href>/dav/addressbooks/user/ken/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:collection/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</R:addressbook-home-set>
</D:prop>
Murchison Standards Track [Page 20]
RFC 8144 Prefer Header Field in WebDAV April 2017
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:current-user-principal>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
B.3. PROPPATCH
B.3.1. Typical PROPPATCH Request/Response
>> Request <<
PROPPATCH /container/ HTTP/1.1
Host: webdav.example.com
Content-Type: application/xml; charset=utf-8
Content-Length: 199
<?xml version="1.0" encoding="utf-8"?>
<D:propertyupdate xmlns:D="DAV:">
<D:set>
<D:prop>
<D:displayname>My Container</D:displayname>
</D:prop>
</D:set>
</D:propertyupdate>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: application/xml; charset=utf-8
Content-Length: 297
<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>/container/</D:href>
<D:propstat>
<D:prop>
<D:displayname/>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
Murchison Standards Track [Page 21]
RFC 8144 Prefer Header Field in WebDAV April 2017
B.3.2. Minimal PROPPATCH Request/Response
>> Request <<
PROPPATCH /container/ HTTP/1.1
Host: webdav.example.com
Content-Type: application/xml; charset=utf-8
Content-Length: 199
Prefer: return=minimal
<?xml version="1.0" encoding="utf-8"?>
<D:propertyupdate xmlns:D="DAV:">
<D:set>
<D:prop>
<D:displayname>My Container</D:displayname>
</D:prop>
</D:set>
</D:propertyupdate>
>> Response <<
HTTP/1.1 200 OK
Content-Length: 0
Preference-Applied: return=minimal
B.4. MKCOL
B.4.1. Verbose MKCOL Request/Response
>> Request <<
MKCOL /container/ HTTP/1.1
Host: webdav.example.com
Content-Type: application/xml; charset=utf-8
Content-Length: 181
<?xml version="1.0" encoding="utf-8"?>
<D:mkcol xmlns:D="DAV:">
<D:set>
<D:prop>
<D:displayname>My Container</D:displayname>
</D:prop>
</D:set>
</D:mkcol>
>> Response <<
HTTP/1.1 201 Created
Murchison Standards Track [Page 22]
RFC 8144 Prefer Header Field in WebDAV April 2017
Cache-Control: no-cache
Content-Type: application/xml; charset=utf-8
Content-Length: 224
<?xml version="1.0" encoding="utf-8"?>
<D:mkcol-response xmlns:D="DAV:">
<D:propstat>
<D:prop>
<D:displayname/>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:mkcol-response>
B.4.2. Minimal MKCOL Request/Response
>> Request <<
MKCOL /container/ HTTP/1.1
Host: webdav.example.com
Content-Type: application/xml; charset=utf-8
Content-Length: 181
Prefer: return=minimal
<?xml version="1.0" encoding="utf-8"?>
<D:mkcol xmlns:D="DAV:">
<D:set>
<D:prop>
<D:displayname>My Container</D:displayname>
</D:prop>
</D:set>
</D:mkcol>
>> Response <<
HTTP/1.1 201 Created
Cache-Control: no-cache
Content-Length: 0
Preference-Applied: return=minimal
B.5. POST
B.5.1. Typical Resource Creation and Retrieval via POST + GET
Note that this request is not conditional because by using the POST
[RFC5995] method, the client lets the server choose the resource URI,
thereby guaranteeing that it will not modify an existing resource.
Murchison Standards Track [Page 23]
RFC 8144 Prefer Header Field in WebDAV April 2017
>> Request <<
POST /container/work;add-member/ HTTP/1.1
Host: caldav.example.com
Content-Type: text/calendar; charset=utf-8
Content-Length: 521
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Example Corp.//CalDAV Client//EN
BEGIN:VEVENT
UID:CD87465FA
SEQUENCE:0
DTSTAMP:20120602T185254Z
DTSTART:20120602T160000Z
DTEND:20120602T170000Z
TRANSP:OPAQUE
SUMMARY:Lunch
ORGANIZER;CN="Ken Murchison":mailto:murch@example.com
ATTENDEE;CN="Ken Murchison";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:
mailto:murch@example.com
ATTENDEE;CN="John Doe";CUTYPE=INDIVIDUAL;PARTSTAT
=NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:jdoe@
example.com
END:VEVENT
END:VCALENDAR
>> Response <<
HTTP/1.1 201 Created
Location: /container/work/abc.ics
Content-Length: 0
Note that the server did not include any validator header fields
(e.g., ETag) in the response, signaling that the created
representation differs from the representation sent in the body of
the request. The client has to send a separate GET request to
retrieve the current representation:
>> Request <<
GET /container/work/abc.ics HTTP/1.1
Host: caldav.example.com
>> Response <<
HTTP/1.1 200 OK
Murchison Standards Track [Page 24]
RFC 8144 Prefer Header Field in WebDAV April 2017
Content-Type: text/calendar; charset=utf-8
Content-Length: 541
ETag: "nahduyejc"
Schedule-Tag: "jfd84hgbcn"
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Example Corp.//CalDAV Server//EN
BEGIN:VEVENT
UID:CD87465FA
SEQUENCE:0
DTSTAMP:20120602T185300Z
DTSTART:20120602T160000Z
DTEND:20120602T170000Z
TRANSP:OPAQUE
SUMMARY:Lunch
ORGANIZER;CN="Ken Murchison":mailto:murch@example.com
ATTENDEE;CN="Ken Murchison";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:
mailto:murch@example.com
ATTENDEE;CN="John Doe";CUTYPE=INDIVIDUAL;PARTSTAT
=NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE;SCHEDULE-STATUS=
1.2:mailto:jdoe@example.com
END:VEVENT
END:VCALENDAR
B.5.2. Streamlined Resource Creation and Retrieval via POST
Note that this request is not conditional because by using the POST
[RFC5995] method, the client lets the server choose the resource URI,
thereby guaranteeing that it will not modify an existing resource.
>> Request <<
POST /container/work;add-member/ HTTP/1.1
Host: caldav.example.com
Content-Type: text/calendar; charset=utf-8
Content-Length: 521
Prefer: return=representation
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Example Corp.//CalDAV Client//EN
BEGIN:VEVENT
UID:CD87465FA
SEQUENCE:0
DTSTAMP:20120602T185254Z
DTSTART:20120602T160000Z
DTEND:20120602T170000Z
Murchison Standards Track [Page 25]
RFC 8144 Prefer Header Field in WebDAV April 2017
TRANSP:OPAQUE
SUMMARY:Lunch
ORGANIZER;CN="Ken Murchison":mailto:murch@example.com
ATTENDEE;CN="Ken Murchison";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:
mailto:murch@example.com
ATTENDEE;CN="John Doe";CUTYPE=INDIVIDUAL;PARTSTAT
=NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE:mailto:jdoe@
example.com
END:VEVENT
END:VCALENDAR
>> Response <<
HTTP/1.1 201 Created
Location: /container/work/abc.ics
Content-Type: text/calendar; charset=utf-8
Content-Length: 541
Content-Location: /container/work/abc.ics
ETag: "nahduyejc"
Schedule-Tag: "jfd84hgbcn"
Preference-Applied: return=representation
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Example Corp.//CalDAV Server//EN
BEGIN:VEVENT
UID:CD87465FA
SEQUENCE:0
DTSTAMP:20120602T185300Z
DTSTART:20120602T160000Z
DTEND:20120602T170000Z
TRANSP:OPAQUE
SUMMARY:Lunch
ORGANIZER;CN="Ken Murchison":mailto:murch@example.com
ATTENDEE;CN="Ken Murchison";CUTYPE=INDIVIDUAL;PARTSTAT=ACCEPTED:
mailto:murch@example.com
ATTENDEE;CN="John Doe";CUTYPE=INDIVIDUAL;PARTSTAT
=NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE;SCHEDULE-STATUS=
1.2:mailto:jdoe@example.com
END:VEVENT
END:VCALENDAR
Murchison Standards Track [Page 26]
RFC 8144 Prefer Header Field in WebDAV April 2017
B.6. PUT
B.6.1. Typical Conditional Resource Update Failure and Retrieval via
PUT + GET
>> Request <<
PUT /container/motd.txt HTTP/1.1
Host: dav.example.com
Content-Type: text/plain
Content-Length: 69
If-Match: "asd973"
Either write something worth reading or do something worth writing.
>> Response <<
HTTP/1.1 412 Precondition Failed
Content-Length: 0
The resource has been modified by another user agent (ETag mismatch);
therefore, the client has to send a separate GET request to retrieve
the current representation:
>> Request <<
GET /container/motd.txt HTTP/1.1
Host: dav.example.com
>> Response <<
HTTP/1.1 200 OK
Content-Type: text/plain
Content-Length: 52
ETag: "789sdas"
An investment in knowledge pays the best interest.
B.6.2. Streamlined Conditional Resource Update Failure and Retrieval
via PUT
>> Request <<
PUT /container/motd.txt HTTP/1.1
Host: dav.example.com
Content-Type: text/plain
Murchison Standards Track [Page 27]
RFC 8144 Prefer Header Field in WebDAV April 2017
Content-Length: 69
If-Match: "asd973"
Prefer: return=representation
Either write something worth reading or do something worth writing.
>> Response <<
HTTP/1.1 412 Precondition Failed
Content-Type: text/plain
Content-Length: 52
Content-Location: /container/motd.txt
ETag: "789sdas"
Preference-Applied: return=representation
An investment in knowledge pays the best interest.
Acknowledgements
The author would like to thank the following individuals for
contributing their ideas and support for writing this specification:
Cyrus Daboo, Helge Hess, Andrew McMillan, Arnaud Quillaud, and Julian
Reschke.
The author would also like to thank the Calendaring and Scheduling
Consortium for advice with this specification and for organizing
interoperability testing events to help refine it.
Author's Address
Kenneth Murchison
Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213
United States of America
Phone: +1-412-268-1982
Email: murch@andrew.cmu.edu
Murchison Standards Track [Page 28]
ERRATA
