Network Working Group C. Daboo

Network Working Group C. Daboo
Request for Comments: 5689 Apple Inc.
Updates: 4791, 4918 September 2009
Category: Standards Track

Extended MKCOL for Web Distributed Authoring and Versioning (WebDAV)

Abstract

This specification extends the Web Distributed Authoring and
Versioning (WebDAV) MKCOL (Make Collection) method to allow
collections of arbitrary resourcetype to be created and to allow
properties to be set at the same time.

Status of This Memo

This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

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document authors. All rights reserved.

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Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may

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RFC 5689 Extended MKCOL for WebDAV September 2009

not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. WebDAV Extended MKCOL . . . . . . . . . . . . . . . . . . . . 4
3.1. Extended MKCOL Support . . . . . . . . . . . . . . . . . . 5
3.1.1. Example: Using OPTIONS for the Discovery of
Support for Extended MKCOL . . . . . . . . . . . . . . 5
3.2. Status Codes . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Additional Precondition for Extended MKCOL . . . . . . . . 5
3.4. Example: Successful Extended MKCOL Request . . . . . . . . 6
3.5. Example: Unsuccessful Extended MKCOL Request . . . . . . . 6
4. Using Extended MKCOL as an Alternative for MKxxx Methods . . . 8
4.1. MKCALENDAR Alternative . . . . . . . . . . . . . . . . . . 8
4.1.1. Example: Using MKCOL Instead of MKCALENDAR . . . . . . 8
5. XML Element Definitions . . . . . . . . . . . . . . . . . . . 10
5.1. mkcol XML Element . . . . . . . . . . . . . . . . . . . . 10
5.2. mkcol-response XML Element . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
8. Normative References . . . . . . . . . . . . . . . . . . . . . 11

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1. Introduction

WebDAV [RFC4918] defines the HTTP [RFC2616] method MKCOL. This
method is used to create WebDAV collections on the server. However,
several WebDAV-based specifications (e.g., CalDAV [RFC4791]) define
"special" collections -- ones that are identified by additional
values in the DAV:resourcetype property assigned to the collection
resource or by other means. These "special" collections are created
by new methods (e.g., MKCALENDAR). The addition of a new MKxxx
method for each new "special" collection adds to server complexity
and is detrimental to overall reliability due to the need to make
sure intermediaries are aware of these methods.

This specification defines an extension to the WebDAV MKCOL method
that adds a request body allowing a client to specify WebDAV
properties to be set on the newly created collection or resource. In
particular, the DAV:resourcetype property can be used to create a
"special" collection; alternatively, other properties can be used to
create a "special" resource. This avoids the need to invent new
MKxxx methods.

2. Conventions Used in This 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 [RFC2119].

This document uses XML DTD fragments (Section 3.2 of
[W3C.REC-xml-20081126]) as a purely notational convention. WebDAV
request and response bodies cannot be validated by a DTD due to the
specific extensibility rules defined in Section 17 of [RFC4918] and
due to the fact that all XML elements defined by this specification
use the XML namespace name "DAV:". In particular:

1. Element names use the "DAV:" namespace.

2. Element ordering is irrelevant unless explicitly stated.

3. Extension elements (elements not already defined as valid child
elements) may be added anywhere, except when explicitly stated
otherwise.

4. Extension attributes (attributes not already defined as valid for
this element) may be added anywhere, except when explicitly
stated otherwise.

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RFC 5689 Extended MKCOL for WebDAV September 2009

When an XML element type in the "DAV:" namespace is referenced in
this document outside of the context of an XML fragment, the string
"DAV:" will be prefixed to the element type.

This document inherits, and sometimes extends, DTD productions from
Section 14 of [RFC4918].

3. WebDAV Extended MKCOL

The WebDAV MKCOL request is extended to allow the inclusion of a
request body. The request body is an XML document containing a
single DAV:mkcol XML element as the root element. The Content-Type
request header MUST be set appropriately for an XML body (e.g., set
to "text/xml" or "application/xml"). XML-typed bodies for an MKCOL
request that do not have DAV:mkcol as the root element are reserved
for future usage.

One or more DAV:set XML elements may be included in the DAV:mkcol XML
element to allow setting properties on the collection as it is
created. In particular, to create a collection of a particular type,
the DAV:resourcetype XML element MUST be included in a DAV:set XML
element and MUST specify the expected resource type elements for the
new resource, which MUST include the DAV:collection element that
needs to be present for any WebDAV collection.

As per the PROPPATCH method (Section 9.2 of [RFC4918]), servers MUST
process any DAV:set instructions in document order (an exception to
the normal rule that ordering is irrelevant). If any one instruction
fails to execute successfully, all instructions MUST fail (i.e.,
either all succeed or all fail). Thus, if any error occurs during
processing, all executed instructions MUST be undone and a proper
error result returned. Failure to set a property value on the
collection MUST result in a failure of the overall MKCOL request --
i.e., the collection is not created.

The response to an extended MKCOL request MUST be an XML document
containing a single DAV:mkcol-response XML element, which MUST
contain DAV:propstat XML elements with the status of each property
when the request fails due to a failure to set one or more of the
properties specified in the request body. The server MAY return a
response body in the case where the request is successful, indicating
success for setting each property specified in the request body.
When an empty response body is returned with a success request status
code, the client can assume that all properties were set.

In all other respects, the behavior of the extended MKCOL request
follows that of the standard MKCOL request.

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3.1. Extended MKCOL Support

A server supporting the features described in this document MUST
include "extended-mkcol" as a field in the DAV response header from
an OPTIONS request on any URI that supports use of the extended MKCOL
method.

3.1.1. Example: Using OPTIONS for the Discovery of Support for Extended
MKCOL

>> Request <<

OPTIONS /addressbooks/users/ HTTP/1.1
Host: addressbook.example.com

>> Response <<

HTTP/1.1 200 OK
Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE
Allow: MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, REPORT, ACL
DAV: 1, 2, 3, access-control, extended-mkcol
Date: Sat, 11 Nov 2006 09:32:12 GMT
Content-Length: 0

3.2. Status Codes

As per Section 9.3.1 of [RFC4918].

3.3. Additional Precondition for Extended MKCOL

WebDAV ([RFC4918], Section 16) defines preconditions and
postconditions for request behavior. This specification adds the
following precondition for the extended MKCOL request.

Name: valid-resourcetype

Namespace: DAV:

Use with: Typically 403 (Forbidden)

Purpose: (precondition) -- The server MUST support the specified
resourcetype value for the specified collection.

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3.4. Example: Successful Extended MKCOL Request

This example shows how the extended MKCOL request is used to create a
collection of a fictitious type "special-resource". The response
body is empty as the request completed successfully.

>> Request <<

MKCOL /home/special/ HTTP/1.1
Host: special.example.com
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx

<?xml version="1.0" encoding="utf-8" ?>
<D:mkcol xmlns:D="DAV:"
xmlns:E="http://example.com/ns/">
<D:set>
<D:prop>
<D:resourcetype>
<D:collection/>
<E:special-resource/>
</D:resourcetype>
<D:displayname>Special Resource</D:displayname>
</D:prop>
</D:set>
</D:mkcol>

>> Response <<

HTTP/1.1 201 Created
Cache-Control: no-cache
Date: Sat, 11 Nov 2006 09:32:12 GMT

3.5. Example: Unsuccessful Extended MKCOL Request

This example shows an attempt to use the extended MKCOL request to
create a collection of a fictitious type "special-resource", which is
not actually supported by the server. The response body shows that
an error occurred specifically with the DAV:resourcetype property.

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>> Request <<

MKCOL /home/special/ HTTP/1.1
Host: special.example.com
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx

<?xml version="1.0" encoding="utf-8" ?>
<D:mkcol xmlns:D="DAV:"
xmlns:E="http://example.com/ns/">
<D:set>
<D:prop>
<D:resourcetype>
<D:collection/>
<E:special-resource/>
</D:resourcetype>
<D:displayname>Special Resource</D:displayname>
</D:prop>
</D:set>
</D:mkcol>

>> Response <<

HTTP/1.1 403 Forbidden
Cache-Control: no-cache
Date: Sat, 11 Nov 2006 09:32:12 GMT
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx

<?xml version="1.0" encoding="utf-8" ?>
<D:mkcol-response xmlns:D="DAV:">
<D:propstat>
<D:prop>
<D:resourcetype/>
</D:prop>
<D:status>HTTP/1.1 403 Forbidden</D:status>
<D:error><D:valid-resourcetype /></D:error>
<D:responsedescription>Resource type is not
supported by this server</D:responsedescription>
</D:propstat>
<D:propstat>
<D:prop>
<D:displayname/>
</D:prop>
<D:status>HTTP/1.1 424 Failed Dependency</D:status>
</D:propstat>
</D:mkcol-response>

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RFC 5689 Extended MKCOL for WebDAV September 2009

4. Using Extended MKCOL as an Alternative for MKxxx Methods

One of the goals of this extension is to eliminate the need for other
extensions to define their own variant of MKCOL to create the special
collections they need. This extension can be used as an alternative
to existing MKxxx methods in other extensions as detailed below. If
a server supports this extension and the other extension listed, then
the server MUST support use of the extended MKCOL method to achieve
the same result as the MKxxx method of the other extension.

4.1. MKCALENDAR Alternative

CalDAV defines the MKCALENDAR method to create a calendar collection
as well as to set properties during creation (Section 5.3.1 of
[RFC4791]).

The extended MKCOL method can be used instead by specifying both DAV:
collection and CALDAV:calendar-collection XML elements in the DAV:
resourcetype property, set during the extended MKCOL request.

4.1.1. Example: Using MKCOL Instead of MKCALENDAR

The first example below shows an MKCALENDAR request containing a
CALDAV:mkcalendar XML element in the request body and returning a
CALDAV:mkcalendar-response XML element in the response body.

>> MKCALENDAR Request <<

MKCALENDAR /home/lisa/calendars/events/ HTTP/1.1
Host: calendar.example.com
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx

<?xml version="1.0" encoding="utf-8" ?>
<C:mkcalendar xmlns:D="DAV:"
xmlns:C="urn:ietf:params:xml:ns:caldav">
<D:set>
<D:prop>
<D:displayname>Lisa's Events</D:displayname>
</D:prop>
</D:set>
</C:mkcalendar>

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RFC 5689 Extended MKCOL for WebDAV September 2009

>> MKCALENDAR Response <<

HTTP/1.1 201 Created
Cache-Control: no-cache
Date: Sat, 11 Nov 2006 09:32:12 GMT
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx

<?xml version="1.0" encoding="utf-8" ?>
<C:mkcalendar-response xmlns:D="DAV:"
xmlns:C="urn:ietf:params:xml:ns:caldav">
<D:propstat>
<D:prop>
<D:displayname/>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</C:mkcalendar-response>

The second example shows the equivalent extended MKCOL request with
the same request and response XML elements.

>> MKCOL Request <<

MKCOL /home/lisa/calendars/events/ HTTP/1.1
Host: calendar.example.com
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx

<?xml version="1.0" encoding="utf-8" ?>
<D:mkcol xmlns:D="DAV:"
xmlns:C="urn:ietf:params:xml:ns:caldav">
<D:set>
<D:prop>
<D:resourcetype>
<D:collection/>
<C:calendar/>
</D:resourcetype>
<D:displayname>Lisa's Events</D:displayname>
</D:prop>
</D:set>
</D:mkcol>

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RFC 5689 Extended MKCOL for WebDAV September 2009

>> MKCOL Response <<

HTTP/1.1 201 Created
Cache-Control: no-cache
Date: Sat, 11 Nov 2006 09:32:12 GMT
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx

<?xml version="1.0" encoding="utf-8" ?>
<D:mkcol-response xmlns:D="DAV:"
xmlns:C="urn:ietf:params:xml:ns:caldav">
<D:propstat>
<D:prop>
<D:resourcetype/>
<D:displayname/>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:mkcol-response>

5. XML Element Definitions

5.1. mkcol XML Element

Name: mkcol

Namespace: DAV:

Purpose: Used in a request to specify properties to be set in an
extended MKCOL request, as well as any additional information
needed when creating the resource.

Description: This XML element is a container for the information
required to modify the properties on a collection resource as it
is created in an extended MKCOL request.

Definition:

<!ELEMENT mkcol (set+)>

5.2. mkcol-response XML Element

Name: mkcol-response

Namespace: DAV:

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RFC 5689 Extended MKCOL for WebDAV September 2009

Purpose: Used in a response to indicate the status of properties
that were set or failed to be set during an extended MKCOL
request.

Description: This XML element is a container for the information
returned about a resource that has been created in an extended
MKCOL request.

Definition:

<!ELEMENT mkcol-response (propstat+)>

6. Security Considerations

This extension does not introduce any new security concerns beyond
those already described in HTTP [RFC2616] and WebDAV [RFC4918].

7. Acknowledgments

Thanks to Bernard Desruisseaux, Mike Douglass, Alexey Melnikov,
Julian Reschke, and Simon Vaillancourt.

8. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

[RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault,
"Calendaring Extensions to WebDAV (CalDAV)", RFC 4791,
March 2007.

[RFC4918] Dusseault, L., "HTTP Extensions for Web Distributed
Authoring and Versioning (WebDAV)", RFC 4918, June 2007.

[W3C.REC-xml-20081126]
Maler, E., Yergeau, F., Paoli, J., Bray, T., and C.
Sperberg-McQueen, "Extensible Markup Language (XML) 1.0
(Fifth Edition)", World Wide Web Consortium
Recommendation REC-xml-20081126, November 2008,
<http://www.w3.org/TR/2008/REC-xml-20081126>.

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Author's Address

Cyrus Daboo
Apple Inc.
1 Infinite Loop
Cupertino, CA 95014
USA

EMail: [email protected]
URI: http://www.apple.com/

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