WEBDAV Working Group J. Slein
Internet-Draft Xerox
Expires: March 10, 2004 J. Whitehead
U.C. Santa Cruz
J. Davis
CourseNet
G. Clemm
Rational
C. Fay
FileNet
J. Crawford
IBM
J. Reschke, Ed.
greenbytes
September 10, 2003
WebDAV Redirect Reference Resources
draft-ietf-webdav-redirectref-protocol-04
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
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groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
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The list of current Internet-Drafts can be accessed at http://
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This Internet-Draft will expire on March 10, 2004.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This specification defines redirect reference resources. A redirect
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reference resource is a resource whose default response is an HTTP/
1.1 302 (Found) status code, redirecting the client to a different
resource, the target resource. A redirect reference makes it
possible to access the target resource indirectly, through any URI
mapped to the redirect reference resource. There are no integrity
guarantees associated with redirect reference resources.
Distribution of this document is unlimited. Please send comments to
the Distributed Authoring and Versioning (WebDAV) working group at
w3c-dist-auth@w3.org [1], which may be joined by sending a message
with subject "subscribe" to w3c-dist-auth-request@w3.org [2].
Discussions of the WEBDAV working group are archived at URL: http://
lists.w3.org/Archives/Public/w3c-dist-auth/.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 7
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Overview of Redirect Reference Resources . . . . . . . . . . 9
5. Creating a Redirect Reference Resource . . . . . . . . . . . 10
5.1 MKRESOURCE . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.2 Example: Creating a Redirect Reference Resource with
MKRESOURCE . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Operations on Redirect Reference Resources . . . . . . . . . 13
6.1 Example: GET on a Redirect Reference Resource . . . . . . . 14
6.2 Example: PUT on a Redirect Reference Resource with
Apply-To-Redirect-Ref . . . . . . . . . . . . . . . . . . . 14
6.3 Example: PROPPATCH on a Redirect Reference Resource . . . . 15
7. Operations on Collections That Contain Redirect Reference
Resources . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1 MOVE and DELETE on Collections That Contain Redirect
References . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.2 LOCK on a Collection That Contains Redirect References . . . 17
7.3 Example: PROPFIND on a Collection with Redirect Reference
Resources . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.4 Example: PROPFIND with Apply-To-Redirect-Ref on a
Collection with Redirect Reference Resources . . . . . . . . 18
7.5 Example: COPY on a Collection That Contains a Redirect
Reference Resource . . . . . . . . . . . . . . . . . . . . . 20
7.6 Example: LOCK on a Collection That Contains a Redirect
Reference Resource . . . . . . . . . . . . . . . . . . . . . 21
8. Operations on Targets of Redirect Reference Resources . . . 24
9. Relative URIs in DAV:reftarget . . . . . . . . . . . . . . . 25
9.1 Example: Resolving a Relative URI in a MKRESOURCE Request . 25
9.2 Example: Resolving a Relative URI in a Multi-Status
Response . . . . . . . . . . . . . . . . . . . . . . . . . . 26
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10. Redirect References to Collections . . . . . . . . . . . . . 28
11. Headers . . . . . . . . . . . . . . . . . . . . . . . . . . 30
11.1 Redirect-Ref Response Header . . . . . . . . . . . . . . . . 30
11.2 Apply-To-Redirect-Ref Request Header . . . . . . . . . . . . 30
12. Properties . . . . . . . . . . . . . . . . . . . . . . . . . 31
12.1 reftarget Property . . . . . . . . . . . . . . . . . . . . . 31
12.2 location Pseudo-Property . . . . . . . . . . . . . . . . . . 31
13. XML Elements . . . . . . . . . . . . . . . . . . . . . . . . 32
13.1 redirectref XML Element . . . . . . . . . . . . . . . . . . 32
14. Extensions to the DAV:response XML Element for
Multi-Status Responses . . . . . . . . . . . . . . . . . . . 33
15. Capability Discovery . . . . . . . . . . . . . . . . . . . . 34
15.1 Example: Discovery of Support for Redirect Reference
Resources . . . . . . . . . . . . . . . . . . . . . . . . . 34
16. Security Considerations . . . . . . . . . . . . . . . . . . 35
16.1 Privacy Concerns . . . . . . . . . . . . . . . . . . . . . . 35
16.2 Redirect Loops . . . . . . . . . . . . . . . . . . . . . . . 35
16.3 Redirect Reference Resources and Denial of Service . . . . . 35
16.4 Revealing Private Locations . . . . . . . . . . . . . . . . 35
17. Internationalization Considerations . . . . . . . . . . . . 37
18. IANA Considerations . . . . . . . . . . . . . . . . . . . . 38
19. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 39
Normative References . . . . . . . . . . . . . . . . . . . . 40
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 40
A. Changes to the WebDAV Document Type Definition . . . . . . . 42
B. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . . . . . 43
B.1 Since draft-ietf-webdav-redirectref-protocol-02 . . . . . . 43
B.2 Since draft-ietf-webdav-redirectref-protocol-03 . . . . . . 43
C. Resolved issues (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . . . . . 44
C.1 lc-07-bind . . . . . . . . . . . . . . . . . . . . . . . . . 44
C.2 lc-08-bind . . . . . . . . . . . . . . . . . . . . . . . . . 44
C.3 lc-34-bind . . . . . . . . . . . . . . . . . . . . . . . . . 44
C.4 lc-83-bind . . . . . . . . . . . . . . . . . . . . . . . . . 44
C.5 lc-12-bind . . . . . . . . . . . . . . . . . . . . . . . . . 45
C.6 lc-35-bind . . . . . . . . . . . . . . . . . . . . . . . . . 45
C.7 lc-01-body . . . . . . . . . . . . . . . . . . . . . . . . . 45
C.8 lc-14-bind . . . . . . . . . . . . . . . . . . . . . . . . . 45
C.9 lc-15-direct-ref . . . . . . . . . . . . . . . . . . . . . . 46
C.10 lc-39-no-reference-or-direct-resource . . . . . . . . . . . 46
C.11 lc-40-direct . . . . . . . . . . . . . . . . . . . . . . . . 46
C.12 lc-45-apply-to-rr . . . . . . . . . . . . . . . . . . . . . 47
C.13 lc-01A-body . . . . . . . . . . . . . . . . . . . . . . . . 47
C.14 lc-31-MKCOL . . . . . . . . . . . . . . . . . . . . . . . . 47
C.15 lc-67-redirectref . . . . . . . . . . . . . . . . . . . . . 47
C.16 lc-54-s10 . . . . . . . . . . . . . . . . . . . . . . . . . 48
C.17 lc-78-directory . . . . . . . . . . . . . . . . . . . . . . 48
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C.18 lc-82-iana . . . . . . . . . . . . . . . . . . . . . . . . . 48
D. Open issues (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . . . . . 49
D.1 lc-85-301 . . . . . . . . . . . . . . . . . . . . . . . . . 49
D.2 lc-38-not-hierarchical . . . . . . . . . . . . . . . . . . . 49
D.3 lc-36-server . . . . . . . . . . . . . . . . . . . . . . . . 49
D.4 lc-33-forwarding . . . . . . . . . . . . . . . . . . . . . . 49
D.5 lc-56-notjusthttp . . . . . . . . . . . . . . . . . . . . . 50
D.6 lc-37-integrity . . . . . . . . . . . . . . . . . . . . . . 50
D.7 3-terminology-redirectref . . . . . . . . . . . . . . . . . 50
D.8 lc-43-webdav . . . . . . . . . . . . . . . . . . . . . . . . 50
D.9 lc-19-direct-ref . . . . . . . . . . . . . . . . . . . . . . 51
D.10 lc-04-standard-data-container . . . . . . . . . . . . . . . 51
D.11 lc-05-standard-data-container . . . . . . . . . . . . . . . 51
D.12 lc-20-intro-mkresource . . . . . . . . . . . . . . . . . . . 51
D.13 lc-22-coll . . . . . . . . . . . . . . . . . . . . . . . . . 52
D.14 lc-25-atomic . . . . . . . . . . . . . . . . . . . . . . . . 52
D.15 lc-41-no-webdav . . . . . . . . . . . . . . . . . . . . . . 52
D.16 lc-42-no-webdav . . . . . . . . . . . . . . . . . . . . . . 52
D.17 lc-58-update . . . . . . . . . . . . . . . . . . . . . . . . 53
D.18 lc-23-body . . . . . . . . . . . . . . . . . . . . . . . . . 53
D.19 lc-24-properties . . . . . . . . . . . . . . . . . . . . . . 53
D.20 lc-47-207 . . . . . . . . . . . . . . . . . . . . . . . . . 54
D.21 lc-48-s6 . . . . . . . . . . . . . . . . . . . . . . . . . . 54
D.22 lc-28-lang . . . . . . . . . . . . . . . . . . . . . . . . . 55
D.23 lc-29-lang . . . . . . . . . . . . . . . . . . . . . . . . . 55
D.24 lc-49-put . . . . . . . . . . . . . . . . . . . . . . . . . 55
D.25 lc-44-pseudo . . . . . . . . . . . . . . . . . . . . . . . . 55
D.26 lc-61-pseudo . . . . . . . . . . . . . . . . . . . . . . . . 56
D.27 lc-60-ex . . . . . . . . . . . . . . . . . . . . . . . . . . 56
D.28 lc-62-oldclient . . . . . . . . . . . . . . . . . . . . . . 56
D.29 lc-63-move . . . . . . . . . . . . . . . . . . . . . . . . . 56
D.30 lc-06-reftarget-relative . . . . . . . . . . . . . . . . . . 57
D.31 lc-57-noautoupdate . . . . . . . . . . . . . . . . . . . . . 57
D.32 lc-71-relative . . . . . . . . . . . . . . . . . . . . . . . 57
D.33 lc-53-s10 . . . . . . . . . . . . . . . . . . . . . . . . . 58
D.34 lc-72-trailingslash . . . . . . . . . . . . . . . . . . . . 58
D.35 lc-50-blindredirect . . . . . . . . . . . . . . . . . . . . 58
D.36 lc-74-terminology . . . . . . . . . . . . . . . . . . . . . 59
D.37 lc-75-ignore . . . . . . . . . . . . . . . . . . . . . . . . 59
D.38 lc-76-location . . . . . . . . . . . . . . . . . . . . . . . 59
D.39 lc-79-accesscontrol . . . . . . . . . . . . . . . . . . . . 59
D.40 lc-80-i18n . . . . . . . . . . . . . . . . . . . . . . . . . 60
D.41 lc-55-iana . . . . . . . . . . . . . . . . . . . . . . . . . 60
Intellectual Property and Copyright Statements . . . . . . . 61
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1. Introduction
This is one of a pair of specifications that extend the WebDAV
Distributed Authoring Protocol to enable clients to create new access
paths to existing resources. This capability is useful for several
reasons:
URIs of WebDAV-compliant resources are hierarchical and correspond to
a hierarchy of collections in resource space. The WebDAV Distributed
Authoring Protocol makes it possible to organize these resources into
hierarchies, placing them into groupings, known as collections, which
are more easily browsed and manipulated than a single flat
collection. However, hierarchies require categorization decisions
that locate resources at a single location in the hierarchy, a
drawback when a resource has multiple valid categories. For example,
in a hierarchy of vehicle descriptions containing collections for
cars and boats, a description of a combination car/boat vehicle could
belong in either collection. Ideally, the description should be
accessible from both. Allowing clients to create new URIs that access
the existing resource lets them put that resource into multiple
collections.
Hierarchies also make resource sharing more difficult, since
resources that have utility across many collections are still forced
into a single collection. For example, the mathematics department at
one university might create a collection of information on fractals
that contains bindings to some local resources, but also provides
access to some resources at other universities. For many reasons, it
may be undesirable to make physical copies of the shared resources on
the local server: to conserve disk space, to respect copyright
constraints, or to make any changes in the shared resources visible
automatically. Being able to create new access paths to existing
resources in other collections or even on other servers is useful for
this sort of case.
The redirect reference resources defined here provide a mechanism for
creating alternative access paths to existing resources. A redirect
reference resource is a resource in one collection whose purpose is
to forward requests to another resource (its target), possibly in a
different collection. In this way, it allows clients to submit
requests to the target resource from another collection. It
redirects most requests to the target resource using the HTTP 302
(Found) status code, thereby providing a form of mediated access to
the target resource.
A redirect reference is a resource, and so can have properties and a
body of its own. Properties of a redirect reference resource can
contain such information as who created the reference, when, and why.
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Since redirect reference resources are implemented using HTTP 302
responses, it generally takes two round trips to submit a request to
the intended resource. Servers are not required to enforce the
integrity of redirect references. Redirect references work equally
well for local resources and for resources that reside on a different
server from the reference.
The remainder of this document is structured as follows: Section 3
defines terms that will be used throughout the specification.
Section 4 provides an overview of redirect reference resources.
Section 5 discusses how to create a redirect reference resource.
Section 6 defines the semantics of existing methods when applied to
redirect reference resources, and Section 7 discusses their semantics
when applied to collections that contain redirect reference
resources. Sections 8 through 10 discuss several other issues raised
by the existence of redirect reference resources. Sections 11
through 14 define the new headers, properties, and XML elements
required to support redirect reference resources. Section 15
discusses capability discovery. Sections 16 through 18 present the
security, internationalization, and IANA concerns raised by this
specification. The remaining sections provide a variety of supporting
information.
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2. Notational Conventions
Since this document describes a set of extensions to the WebDAV
Distributed Authoring Protocol [RFC2518], itself an extension to the
HTTP/1.1 protocol, the augmented BNF used here to describe protocol
elements is exactly the same as described in Section 2.1 of
[RFC2616]. Since this augmented BNF uses the basic production rules
provided in Section 2.2 of [RFC2616], these rules apply to this
document as well.
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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3. Terminology
The terminology used here follows and extends that in the WebDAV
Distributed Authoring Protocol specification [RFC2518]. Definitions
of the terms resource, Uniform Resource Identifier (URI), and Uniform
Resource Locator (URL) are provided in [RFC2396].
Redirect Reference Resource
A resource created to redirect all requests made to it, using 302
(Found), to a defined target resource.
Non-Reference Resource
A resource that is not a reference to another resource.
Target Resource
The resource to which requests are forwarded by a reference
resource.
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4. Overview of Redirect Reference Resources
For all operations submitted to a redirect reference resource, the
default response is a 302 (Found), accompanied by the Redirect-Ref
header (defined in Section 11.1 below) and the Location header set to
the URI of the target resource. With this information, the client
can resubmit the request to the URI of the target resource.
A redirect reference resource never automatically forwards requests
to its target resource. Redirect resources bring the same benefits as
links in HTML documents. They can be created and maintained without
the involvement or even knowledge of their target resource. This
reduces the cost of linking between resources."
If the client is aware that it is operating on a redirect reference
resource, it can resolve the reference by retrieving the reference
resource's DAV:reftarget property (defined in Section 12.1 below),
whose value contains the URI of the target resource. It can then
submit requests to the target resource.
A redirect reference resource is a new type of resource. To
distinguish redirect reference resources from non-reference
resources, a new value of the DAV:resourcetype property (defined in
[RFC2518]), DAV:redirectref, is defined in Section 13.1 below.
Since a redirect reference resource is a resource, it can have its
own properties and body, and methods can be applied to the reference
resource as well as to its target resource. The
Apply-To-Redirect-Ref request header (defined in Section 11.2 below)
is provided so that referencing-aware clients can control whether an
operation is applied to the redirect reference resource or to its
target resource. The Apply-To-Redirect-Ref header can be used with
most requests to redirect reference resources. This header is
particularly useful with PROPFIND, to retrieve the reference
resource's own properties.
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5. Creating a Redirect Reference Resource
The MKRESOURCE method is used to create new redirect reference
resources. As defined in Section 5.1, MKRESOURCE can be used to
create a resource of any type other than standard data containers and
collections. In order to create a redirect reference resource using
MKRESOURCE, the values of two properties must be set in the body of
the MKRESOURCE request. The value of DAV:resourcetype MUST be set to
DAV:redirectref, a new value of DAV:resourcetype defined in Section
13.1. The value of DAV:reftarget MUST be set to the URI of the target
resource.
Used in this way, the MKRESOURCE method creates a redirect reference
resource whose target is identified by the DAV:reftarget property.
5.1 MKRESOURCE
The MKRESOURCE method requests the creation of a resource and
initialization of its properties. It allows resources other than
standard data containers and collections to be created and their
properties initialized in one atomic operation.
Preconditions:
A resource MUST NOT exist at the Request-URI.
Request Marshalling:
The location of the new resource to be created is specified by the
Request-URI.
The request body of the MKRESOURCE method MUST consist of the
DAV:propertyupdate XML element defined in Section 12.13 of
[RFC2518].
Postconditions:
If the response status code is 201, a new resource exists at the
Request-URI.
The body of the new resource is empty.
The properties of the new resource are as specified by the
DAV:propertyupdate request body, using PROPPATCH semantics. If the
DAV:propertyupdate does not specify a DAV:resourcetype, the
resource will be a standard data container.
If the response status code is not 201, then a new resource is not
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created at the Request-URI, and any existing resource at the
Request-URI is unaffected.
Response Marshalling:
Responses from a MKRESOURCE request MUST NOT be cached, as
MKRESOURCE has non-idempotent semantics.
The following status codes can be expected in responses to
MKRESOURCE:
201 (Created): The new resource was successfully created.
207 (Multi-Status): This response is generated if an error was
encountered while initializing the properties of the resource, in
which case the response is as defined in Section 8.2.1 of
[RFC2518].
403 (Forbidden): The server does not allow the creation of the
requested resource type at the requested location, or the parent
collection of the Request-URI exists but cannot accept members.
409 (Conflict): A resource cannot be created at the Request-URI
because the parent collection for the resource does not exist, or
because there is already a resource at that request-URL.
423 (Locked): The Request-URI is locked, and the lock token was
not passed with the request.
507 (Insufficient Storage): The server does not have sufficient
space to record the state of the resource.
5.2 Example: Creating a Redirect Reference Resource with MKRESOURCE
>> Request:
MKRESOURCE /~whitehead/dav/spec08.ref HTTP/1.1
Host: www.ics.uci.edu
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<D:propertyupdate xmlns:D="DAV:">
<D:set>
<D:prop>
<D:resourcetype><D:redirectref/></D:resourcetype>
<D:reftarget>
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<D:href>/i-d/draft-webdav-protocol-08.txt</D:href>
</D:reftarget>
</D:prop>
</D:set>
</D:propertyupdate>
>> Response:
HTTP/1.1 201 Created
This request resulted in the creation of a new redirect reference
resource at www.ics.uci.edu/~whitehead/dav/spec08.ref, which points
to the resource identified by the DAV:reftarget property. In this
example, the target resource is identified by the URI http://
www.ics.uci.edu/i-d/draft-webdav-protocol-08.txt. The redirect
reference resource's DAV:resourcetype property is set to
DAV:redirectref.
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6. Operations on Redirect Reference Resources
Although non-referencing-aware clients cannot create reference
resources, they should be able to submit requests through the
reference resources created by reference-aware WebDAV clients. They
should be able to follow any references to their targets. To make
this possible, a server that receives any request made via a redirect
reference resource MUST return a 302 (Found) status code, unless the
request includes an Apply-To-Redirect-Ref header. The client and
server MUST follow [RFC2616] Section 10.3.3 "302 Found," but with
these additional rules:
o The Location response header MUST contain an absolute URI that
identifies the target of the reference resource.
o The response MUST include the Redirect-Ref header. This header
allows reference-aware WebDAV clients to recognize the resource as
a reference resource and understand the reason for the
redirection.
A reference-aware WebDAV client can act on this response in one of
two ways. It can, like a non-referencing client, resubmit the
request to the URI in the Location header in order to operate on the
target resource. Alternatively, it can resubmit the request to the
URI of the redirect reference resource with the Apply-To-Redirect-Ref
header in order to operate on the reference resource itself. If the
Apply-To-Redirect-Ref header is present, the request MUST be applied
to the reference resource itself, and a 302 response MUST NOT be
returned.
A reference-aware client may know before submitting its request that
the Request-URI identifies a redirect reference resource. In this
case, if the client wants to apply the method to the reference
resource, it can save the round trip caused by the 302 response by
using an Apply-To-Redirect-Ref header in its initial request to the
URI.
A few methods need additional explanation:
The Apply-To-Redirect-Ref header can be used with GET or HEAD to
retrieve the entity headers of a redirect reference resource. When
Apply-To-Redirect-Ref is used with GET or HEAD, the Redirect-Ref
entity header MUST be returned.
A redirect reference resource MAY have a body, though none is defined
for it in this specification. The PUT method can be used, with
Apply-To-Redirect-Ref, to create or replace the body of a redirect
reference resource.
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6.1 Example: GET on a Redirect Reference Resource
>> Request:
GET /bar.html HTTP/1.1
Host: www.foo.com
>> Response:
HTTP/1.1 302 Found
Location: http://www.svr.com/Internet/xxspec08.html
Redirect-Ref:
Since /bar.html is a redirect reference resource and the
Apply-To-Redirect-Ref header is not included in the request, the
response is a 302 (Found). The Redirect-Ref header informs a
reference-aware client that this is not an ordinary HTTP 1.1
redirect, but is a redirect reference resource. The URI of the
target resource is provided in the Location header so that the client
can resubmit the request to the target resource.
6.2 Example: PUT on a Redirect Reference Resource with
Apply-To-Redirect-Ref
>> Request:
PUT /bar.html HTTP/1.1
Host: www.foo.com
Apply-To-Redirect-Ref:
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
. . . some content . . .
>> Response:
HTTP/1.1 200 OK
Although /bar.html is a redirect reference resource, the presence of
the Apply-To-Redirect-Ref header prevents a 302 response, and instead
causes the request to be applied to the reference resource. The
result in this case is that the reference resource is replaced by a
non-reference resource having the content submitted with the request.
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6.3 Example: PROPPATCH on a Redirect Reference Resource
>> Request:
PROPPATCH /bar.html HTTP/1.1
Host: www.foo.com
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:propertyupdate xmlns:D="DAV:"
xmlns:Z="http://www.w3.com/standards/z39.50/">
<D:set>
<D:prop>
<Z:authors>
<Z:Author>Jim Whitehead</Z:Author>
<Z:Author>Roy Fielding</Z:Author>
</Z:authors>
</D:prop>
</D:set>
<D:remove>
<D:prop>
<Z:Copyright-Owner/>
</D:prop>
</D:remove>
</D:propertyupdate>
>> Response:
HTTP/1.1 302 Found
Location: http://www.svr.com/Internet/xxspec08.html
Redirect-Ref:
Since /bar.html is a redirect reference resource and the
Apply-To-Redirect-Ref header is not included in the request, the
response is a 302 (Found). The Redirect-Ref header informs a
reference-aware client that this is not an ordinary HTTP 1.1
redirect, but is a redirect reference resource. The URI of the
target resource is provided in the Location header so that the client
can resubmit the request to the target resource.
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7. Operations on Collections That Contain Redirect Reference Resources
Consistent with the rules in Section 6, the response for each
redirect reference encountered while processing a collection MUST be
a 302 (Found) unless a Apply-To-Redirect-Ref header is included with
the request. The overall response will therefore be a 207
(Multi-Status). Since a Location header and Redirect-Ref header
cannot be returned for each redirect reference encountered, the same
information is provided using properties in the response elements for
those resources. The DAV:location pseudo-property and the
DAV:resourcetype property MUST be included with the 302 status code.
This necessitates an extension to the syntax of the DAV:response
element that was defined in [RFC2518]. The extension is defined in
Section 14 below.
A referencing-aware client can tell from the DAV:resourcetype
property that the collection contains a redirect reference resource.
The DAV:location pseudo-property contains the absolute URI of the
target resource. A referencing-aware client can either use the URI
value of the DAV:location pseudo-property to resubmit its request to
the target resource, or it can submit the request to the redirect
reference resource with Apply-To-Redirect-Ref.
It is recommended that future editors of [RFC2518] define the
DAV:location pseudo-property in [RFC2518], so that non-referencing
clients will also be able to use the response to operate on the
target resource. (This will also enable clients to operate on
traditional HTTP/1.1 302 responses in Multi-Status responses.) Until
then, non-referencing clients will not be able to process 302
responses from redirect reference resources encountered while
processing a collection.
The Apply-To-Redirect-Ref header (defined in Section 11.2) MAY be
used with any request on a collection. If present, it will be
applied to all redirect reference resources encountered while
processing the collection.
7.1 MOVE and DELETE on Collections That Contain Redirect References
DELETE removes the binding that corresponds to the Request-URI. MOVE
removes that binding and creates a new binding to the same resource.
In cases where DELETE and MOVE are applied to a collection, these
operations affect all the descendents of the collection, but they do
so indirectly. There is no need to visit each descendent in order to
process the request. Consequently, even if there are redirect
reference resources in a tree that is being deleted or moved, there
will be no 302 responses from the redirect reference resources.
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7.2 LOCK on a Collection That Contains Redirect References
LOCK poses special problems because it is atomic. An attempt to lock
(with Depth: infinity) a collection that contains redirect references
will always fail. The Multi-Status response will contain a 302
response for each redirect reference.
Reference-aware clients can lock the collection by using
Apply-To-Redirect-Ref, and, if desired, lock the targets of the
redirect references individually.
Non-referencing clients must resort to locking each resource
individually.
7.3 Example: PROPFIND on a Collection with Redirect Reference Resources
Suppose a PROPFIND request with Depth: infinity is submitted to the
following collection, with the members shown here:
http://www.svr.com/MyCollection/
(non-reference resource) diary.html
(redirect reference resource) nunavut
>> Request:
PROPFIND /MyCollection/ HTTP/1.1
Host: www.svr.com
Depth: infinity
Content-Type: text/xml
Content-Length: xxxx
<?xml version="1.0" ?>
<D:propfind xmlns:D="DAV: ">
<D:prop xmlns:J="http://www.svr.com/jsprops/">
<D:resourcetype/>
<J:keywords/>
</D:prop>
</D:propfind>
>> Response:
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxx
<?xml version="1.0" ?>
<D:multistatus xmlns:D="DAV:" xmlns:J="http://www.svr.com/jsprops/">
<D:response>
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<D:href>http://www.svr.com/MyCollection/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype><D:collection/></D:resourcetype>
<J:keywords>diary, interests, hobbies</J:keywords>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://www.svr.com/MyCollection/diary.html</D:href>
<D:propstat>
<D:prop>
<D:resourcetype/>
<J:keywords>diary, travel, family, history</J:keywords>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://www.svr.com/MyCollection/nunavut</D:href>
<D:status>HTTP/1.1 302 Found</D:status>
<D:prop>
<D:location>
<D:href>http://www.inac.gc.ca/art/inuit/</D:href>
</D:location>
<D:resourcetype><D:redirectref/></D:resourcetype>
</D:prop>
</D:response>
</D:multistatus>
In this example the Depth header is set to infinity, and the
Apply-To-Redirect-Ref header is not used. The collection contains
one URI that identifies a redirect reference resource. The response
element for the redirect reference resource has a status of 302
(Found), and includes a DAV:prop element with the DAV:location
pseudo-property and the DAV:resourcetype property to allow clients to
retrieve the properties of its target resource. (The response
element for the redirect reference resource does not include the
requested properties. The client can submit another PROPFIND request
to the URI in the DAV:location pseudo-property to retrieve those
properties.)
7.4 Example: PROPFIND with Apply-To-Redirect-Ref on a Collection with
Redirect Reference Resources
Suppose a PROPFIND request with Apply-To-Redirect-Ref and Depth:
infinity is submitted to the following collection, with the members
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shown here:
/MyCollection/
(non-reference resource) diary.html
(redirect reference resource) nunavut
>> Request:
PROPFIND /MyCollection/ HTTP/1.1
Host: www.svr.com
Depth: infinity
Apply-To-Redirect-Ref:
Content-Type: text/xml
Content-Length: xxxx
<?xml version="1.0" ?>
<D:propfind xmlns:D="DAV:">
<D:prop>
<D:resourcetype/>
<D:reftarget/>
</D:prop>
</D:propfind>
>> Response:
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxx
<?xml version="1.0" ?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://www.svr.com/MyCollection/</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><D:reftarget/></D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://www.svr.com/MyCollection/diary.html</D:href>
<D:propstat>
<D:prop>
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<D:resourcetype/>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop><D:reftarget/></D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://www.svr.com/MyCollection/nunavut</D:href>
<D:propstat>
<D:prop>
<D:resourcetype><D:redirectref/></D:resourcetype>
<D:reftarget>
<D:href>http://www.inac.gc.ca/art/inuit/</D:href>
</D:reftarget>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
Since the Apply-To-Redirect-Ref header is present, the response shows
the properties of the redirect reference resource in the collection
rather than reporting a 302 status.
7.5 Example: COPY on a Collection That Contains a Redirect Reference
Resource
Suppose a COPY request is submitted to the following collection, with
the members shown:
/MyCollection/
(non-reference resource) diary.html
(redirect reference resource) nunavut with target
/Someplace/nunavut.map
>> Request:
COPY /MyCollection/ HTTP/1.1
Host: www.svr.com
Depth: infinity
Destination: http://www.svr.com/OtherCollection/
>> Response:
HTTP/1.1 207 Multi-Status
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Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://www.svr.com/MyCollection/nunavut</D:href>
<D:status>HTTP/1.1 302 Found</D:status>
<D:prop>
<D:location>
<D:href>http://www.svr.com//Someplace/nunavut.map</D:href>
</D:location>
<D:resourcetype><D:redirectref/></D:resourcetype>
</D:prop>
</D:response>
</D:multistatus>
In this case, since /MyCollection/nunavut is a redirect reference
resource, the COPY operation was only a partial success. The
redirect reference resource was not copied, but a 302 response was
returned for it. So the resulting collection is as follows:
/OtherCollection/
(non-reference resource) diary.html
7.6 Example: LOCK on a Collection That Contains a Redirect Reference
Resource
Suppose a LOCK request is submitted to the following collection, with
the members shown:
/MyCollection/
(non-reference resource) diary.html
(redirect reference resource) nunavut
>> Request:
LOCK /MyCollection/ HTTP/1.1
Host: www.svr.com
Content-Type: text/xml
Content-Length: nnnn
Authorizaton: Digest username="jas",
realm=jas@webdav.sb.aol.com, nonce=". . . ",
uri="/MyCollection/tuva",
response=". . . ", opaque=". . . "
<?xml version="1.0" ?>
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<D:lockinfo xmlns:D="DAV:">
<D:lockscope><D:exclusive/></D:lockscope>
<D:locktype><D:write/></D:locktype>
<D:owner>
<D:href>http://www.svr.com/~jas/contact.html</D:href>
</D:owner>
</D:lockinfo>
>> Response:
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: nnnn
<?xml version="1.0" ?>
<D:multistatus xmlns:D="Dav:">
<D:response>
<D:href>http://www.svr.com/MyCollection/</D:href>
<D:propstat>
<D:prop><D:lockdiscovery/></D:prop>
<D:status>HTTP/1.1 424 Failed Dependency</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://www.svr.com/MyCollection/diary.html</D:href>
<D:status>HTTP/1.1 424 Failed Dependency</D:status>
</D:response>
<D:response>
<D:href>http://www.svr.com/MyCollection/nunavut</D:href>
<D:status>HTTP/1.1 302 Found</D:status>
<D:prop>
<D:location>
<D:href>http://www.inac.gc.ca/art/inuit/</D:href>
</D:location>
<D:resourcetype><D:redirectref/></D:resourcetype>
</D:prop>
</D:response>
</D:multistatus>
The server returns a 302 response code for the redirect reference
resource in the collection. Consequently, neither the collection nor
any of the resources identified by its internal member URIs were
locked. A referencing-aware client can submit a separate LOCK request
to the URI in the DAV:location pseudo-property returned for the
redirect reference resource, and can resubmit the LOCK request with
the Apply-To-Redirect-Ref header to the collection. At that point
both the reference resource and its target resource will be locked
(as well as the collection and all the resources identified by its
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other members).
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8. Operations on Targets of Redirect Reference Resources
Operations on targets of redirect reference resources have no effect
on the reference resource.
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9. Relative URIs in DAV:reftarget
The URI in the href in a DAV:reftarget property MAY be a relative
URI. In this case, the base URI to be used for resolving the relative
URI to absolute form is the URI used in the HTTP message to identify
the redirect reference resource to which the DAV:reftarget property
belongs.
When DAV:reftarget occurs in the body of a MKRESOURCE request, the
base URI is constructed as follows: Its scheme component is "http",
its authority component is the value of the Host header in the
request, and its path component is the Request-URI in the request.
See Section 5 of [RFC2396] for a discussion of relative URI
references and how to resolve them.
When DAV:reftarget appears in the context of a Multi-Status response,
it is in a DAV:response element that contains a single DAV:href
element. The value of this DAV:href element serves as the base URI
for resolving a relative URI in DAV:reftarget. The value of DAV:href
may itself be relative, in which case it must be resolved first in
order to serve as the base URI for the relative URI in DAV:reftarget.
If the DAV:href element is relative, its base URI is constructed from
the scheme component "http", the value of the Host header in the
request, and the request-URI.
9.1 Example: Resolving a Relative URI in a MKRESOURCE Request
>> Request:
MKRESOURCE /north/inuvik HTTP/1.1
Host: www.somehost.edu
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<D:propertyupdate xmlns:D="DAV:">
<D:set>
<D:prop>
<D:resourcetype><D:redirectref/></D:resourcetype>
<D:reftarget>
<D:href>mapcollection/inuvik.gif</D:href>
</D:reftarget>
</D:prop>
</D:set>
</D:propertyupdate>
>> Response:
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HTTP/1.1 201 Created
In this example, the base URI is http://www.somehost.edu/north/
inuvik. Then, following the rules in [RFC2396] Section 5, the
relative URI in DAV:reftarget resolves to the absolute URI http://
www.somehost.edu/north/mapcollection/inuvik.gif.
9.2 Example: Resolving a Relative URI in a Multi-Status Response
>> Request:
PROPFIND /geog/ HTTP/1.1
Host: www.xxsvr.com
Apply-To-Redirect-Ref:
Depth: 1
Content-Type: text/xml
Content-Length: nnn
<?xml version="1.0" ?>
<D:propfind xmlns:D="DAV:">
<D:prop>
<D:resourcetype/>
<D:reftarget/>
</D:prop>
</D:propfind>
>> Response:
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: nnn
<?xml version="1/0" ?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>/geog/</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><D:reftarget/></D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
<D:response>
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<D:href>/geog/stats.html</D:href>
<D:propstat>
<D:prop>
<D:resourcetype><D:redirectref/></D:resourcetype>
<D:reftarget>
<D:href>statistics/population/1997.html</D:href>
</D:reftarget>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
In this example, the relative URI statistics/population/1997.html is
returned as the value of reftarget for the reference resource
identified by href /geog/stats.html. The href is itself a relative
URI, which resolves to http://www.xxsrv.com/geog/stats.html. This is
the base URI for resolving the relative URI in reftarget. The
absolute URI of reftarget is http://www.xxsrv.com/geog/statistics/
population/1997.html.
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10. Redirect References to Collections
In a Request-URI /segment1/segment2/segment3, any of the three
segments may identify a redirect reference resource. (See [RFC2396],
Section 3.3, for definitions of "path" and "segment".) If any
segment in a Request- URI identifies a redirect reference resource,
the response is a 302. The value of the Location header in the 302
response is as follows:
The leftmost path segment of the request-URI that identifies a
redirect reference resource, together with all path segments and
separators to the left of it, is replaced by the value of the
redirect reference resource's DAV:reftarget property (resolved to an
absolute URI). The remainder of the request-URI is concatenated to
this path.
Note: If the DAV:reftarget property ends with a "/" and the remainder
of the Request-URI is non-empty (and therefore must begin with a "/
"), the final "/" in the DAV:reftarget property is dropped before the
remainder of the Request-URI is appended.
Consider Request-URI /x/y/z.html. Suppose that /x/ is a redirect
reference resource whose target resource is collection /a/, which
contains redirect reference resource y whose target resource is
collection /b/, which contains redirect reference resource z.html
whose target resource is /c/d.html.
/x/y/z.html
|
| /x -> /a
|
v
/a/y/z.html
|
| /a/y -> /b
|
v
/b/z.html
|
| /b/z.html -> /c/d.html
|
v
/c/d.html
In this case the client must follow up three separate 302 responses
before finally reaching the target resource. The server responds to
the initial request with a 302 with Location: /a/y/z.html, and the
client resubmits the request to /a/y/z.html. The server responds to
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this request with a 302 with Location: /b/z.html, and the client
resubmits the request to /b/z.html. The server responds to this
request with a 302 with Location: /c/d.html, and the client resubmits
the request to /c/d.html. This final request succeeds.
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11. Headers
11.1 Redirect-Ref Response Header
Redirect-Ref = "Redirect-Ref:"
The Redirect-Ref header is used in all 302 responses from redirect
reference resources. Its presence informs reference-aware clients
that the response is not a plain HTTP/1.1 redirect, but is a response
from a redirect reference resource.
11.2 Apply-To-Redirect-Ref Request Header
Apply-To-Redirect-Ref = "Apply-To-Redirect-Ref" ":"
The optional Apply-To-Redirect-Ref header can be used on any request
to a redirect reference resource. When it is used, the request MUST
be applied to the reference resource itself, and a 302 response MUST
NOT be returned.
If the Apply-To-Redirect-Ref header is used on a request to any other
sort of resource besides a redirect reference resource, the server
SHOULD ignore it.
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12. Properties
12.1 reftarget Property
Name: reftarget
Namespace: DAV:
Purpose: A property of redirect reference resources that provides an
efficient way for clients to discover the URI of the target
resource. This is a read-only property after its initial
creation. Its value can only be set in a MKRESOURCE request.
Value: href containing the URI of the target resource. This value
MAY be a relative URI. The reftarget property can occur in the
entity bodies of MKRESOURCE requests and of responses to PROPFIND
requests.
<!ELEMENT reftarget href >
12.2 location Pseudo-Property
Name: location
Namespace: DAV:
Purpose: For use with 302 (Found) response codes in Multi-Status
responses. It contains the absolute URI of the temporary location
of the resource. In the context of redirect reference resources,
this value is the absolute URI of the target resource. It is
analogous to the Location header in HTTP 302 responses defined in
[RFC2616] Section 10.3.3 "302 Found." Including the location
pseudo-property in a Multi- Status response requires an extension
to the syntax of the DAV:response element defined in [RFC2518],
which is defined in Section 14 below. This pseudo-property is not
expected to be stored on the reference resource. It is modeled as
a property only so that it can be returned inside a DAV:prop
element in a Multi-Status response.
Value: href containing the absolute URI of the target resource.
<!ELEMENT location href >
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13. XML Elements
13.1 redirectref XML Element
Name: redirectref
Namespace: DAV:
Purpose: Used as the value of the DAV:resourcetype property to
specify that the resource type is a redirect reference resource.
<!ELEMENT redirectref EMPTY >
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14. Extensions to the DAV:response XML Element for Multi-Status
Responses
As described in Section 7, the DAV:location pseudo-property and the
DAV:resourcetype property may be returned in the DAV:response element
of a 207 Multi-Status response, to allow clients to resubmit their
requests to the target resource of a redirect reference resource.
Whenever these properties are included in a Multi-Status response,
they are placed in a DAV:prop element associated with the href to
which they apply. This structure provides a framework for future
extensions by other standards that may need to include additional
properties in their responses.
Consequently, the definition of the DAV:response XML element changes
to the following:
<!ELEMENT response (href, ((href*, status, prop?) | (propstat+)),
responsedescription?) >
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15. Capability Discovery
Sections 9.1 and 15 of [RFC2518] describe the use of compliance
classes with the DAV header in responses to OPTIONS, to indicate
which parts of the WebDAV Distributed Authoring protocols the
resource supports. This specification defines an OPTIONAL extension
to [RFC2518]. It defines a new compliance class, called
redirectrefs, for use with the DAV header in responses to OPTIONS
requests. If a resource does support redirect references, its
response to an OPTIONS request may indicate that it does, by listing
the new redirectrefs compliance class in the DAV headerand by listing
the MKRESOURCE method as one it supports.
When responding to an OPTIONS request, any type of resource can
include redirectrefs in the value of the DAV header. Doing so
indicates that the server permits a redirect reference resource at
the request URI.
15.1 Example: Discovery of Support for Redirect Reference Resources
>> Request:
OPTIONS /somecollection/someresource HTTP/1.1
HOST: somehost.org
>> Response:
HTTP/1.1 200 OK
Date: Tue, 20 Jan 1998 20:52:29 GMT
Connection: close
Accept-Ranges: none
Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE,
MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, MKRESOURCE
DAV: 1, 2, redirectrefs
The DAV header in the response indicates that the resource /
somecollection/someresource is level 1 and level 2 compliant, as
defined in [RFC2518]. In addition, /somecollection/someresource
supports redirect reference resources. The Allow header indicates
that MKRESOURCE requests can be submitted to /somecollection/
someresource. The Public header shows that other Request-URIs on the
server support additional methods.
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16. Security Considerations
This section is provided to make applications that implement this
protocol aware of the security implications of this protocol.
All of the security considerations of HTTP/1.1 and the WebDAV
Distributed Authoring Protocol specification also apply to this
protocol specification. In addition, redirect reference resources
introduce several new security concerns and increase the risk of some
existing threats. These issues are detailed below.
16.1 Privacy Concerns
By creating redirect reference resources on a trusted server, it is
possible for a hostile agent to induce users to send private
information to a target on a different server. This risk is
mitigated somewhat, since clients are required to notify the user of
the redirection for any request other than GET or HEAD. (See
[RFC2616], Section 10.3.3 302 Found.)
16.2 Redirect Loops
Although redirect loops were already possible in HTTP 1.1, the
introduction of the MKRESOURCE method creates a new avenue for
clients to create loops accidentally or maliciously. If the
reference resource and its target are on the same server, the server
may be able to detect MKRESOURCE requests that would create loops.
See also [RFC2616], Section 10.3 "Redirection 3xx."
16.3 Redirect Reference Resources and Denial of Service
Denial of service attacks were already possible by posting URLs that
were intended for limited use at heavily used Web sites. The
introduction of MKRESOURCE creates a new avenue for similar denial of
service attacks. Clients can now create redirect reference resources
at heavily used sites to target locations that were not designed for
heavy usage.
16.4 Revealing Private Locations
There are several ways that redirect reference resources may reveal
information about collection structures. First, the DAV:reftarget
property of every redirect reference resource contains the URI of the
target resource. Anyone who has access to the reference resource can
discover the collection path that leads to the target resource. The
owner of the target resource may have wanted to limit knowledge of
this collection structure.
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Sufficiently powerful access control mechanisms can control this risk
to some extent. Property-level access control could prevent users
from examining the DAV:reftarget property. (The Location header
returned in responses to requests on redirect reference resources
reveals the same information, however.) In some environments, the
owner of a resource might be able to use access control to prevent
others from creating references to that resource.
This risk is no greater than the similar risk posed by HTML links.
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17. Internationalization Considerations
This specification follows the practices of [RFC2518] in encoding all
human-readable content using XML [XML] and in the treatment of names.
Consequently, this specification complies with the IETF Character Set
Policy [RFC2277].
WebDAV applications MUST support the character set tagging, character
set encoding, and the language tagging functionality of the XML
specification. This constraint ensures that the human-readable
content of this specification complies with [RFC2277].
As in [RFC2518], names in this specification fall into three
categories: names of protocol elements such as methods and headers,
names of XML elements, and names of properties. Naming of protocol
elements follows the precedent of HTTP, using English names encoded
in USASCII for methods and headers. The names of XML elements used
in this specification are English names encoded in UTF-8.
For error reporting, [RFC2518] follows the convention of HTTP/1.1
status codes, including with each status code a short, English
description of the code (e.g., 423 Locked). Internationalized
applications will ignore this message, and display an appropriate
message in the user's language and character set.
This specification introduces no new strings that are displayed to
users as part of normal, error-free operation of the protocol.
For rationales for these decisions and advice for application
implementors, see [RFC2518].
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18. IANA Considerations
All IANA considerations mentioned in [RFC2518] also apply to this
document.
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19. Acknowledgements
This draft has benefited from thoughtful discussion by Jim Amsden,
Peter Carlson, Steve Carter, Tyson Chihaya, Ken Coar, Ellis Cohen,
Bruce Cragun, Spencer Dawkins, Mark Day, Rajiv Dulepet, David Durand,
Roy Fielding, Yaron Goland, Fred Hitt, Alex Hopmann, James Hunt,
Marcus Jager, Chris Kaler, Manoj Kasichainula, Rohit Khare, Daniel
LaLiberte, Steve Martin, Larry Masinter, Jeff McAffer, Joe Orton,
Surendra Koduru Reddy, Juergen Reuter, Max Rible, Sam Ruby, Bradley
Sergeant, Nick Shelness, John Stracke, John Tigue, John Turner, Kevin
Wiggen, and others.
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Normative References
[RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
Languages", BCP 18, RFC 2277, January 1998.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998.
[RFC2518] Goland, Y., Whitehead, E., Faizi, A., Carter, S. and D.
Jensen, "HTTP Extensions for Distributed Authoring --
WEBDAV", RFC 2518, February 1999.
[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.
[XML] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
"Extensible Markup Language (XML) 1.0 (2nd ed)", W3C
REC-xml, October 2000, <http://www.w3.org/TR/2000/
REC-xml-20001006>.
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Authors' Addresses
J. Slein
Xerox Corporation
800 Phillips Road, 105-50C
Webster, NY 14580
EMail: jslein@crt.xerox.com
Jim Whitehead
UC Santa Cruz, Dept. of Computer Science
1156 High Street
Santa Cruz, CA 95064
US
EMail: ejw@cse.ucsc.edu
J. Davis
CourseNet Systems
170 Capp Street
San Francisco, CA 94110
EMail: jrd3@alum.mit.edu
G. Clemm
Rational Software Corporation
20 Maguire Road
Lexington, MA 02173-3104
EMail: geoffrey.clemm@us.ibm.com
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C. Fay
FileNet Corporation
3565 Harbor Boulevard
Costa Mesa, CA 92626-1420
EMail: cfay@filenet.com
J. Crawford
IBM Research
P.O. Box 704
Yorktown Heights, NY 10598
EMail: ccjason@us.ibm.com
Julian F. Reschke (editor)
greenbytes GmbH
Salzmannstrasse 152
Muenster, NW 48159
Germany
Phone: +49 251 2807760
Fax: +49 251 2807761
EMail: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/
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Appendix A. Changes to the WebDAV Document Type Definition
<!-- XML Elements from Section 13 -->
<!ELEMENT redirectref EMPTY >
<!-- -->Property Elements from Section 12 -->
<!ELEMENT reftarget href>
<!ELEMENT location href>
<!-- Changes to the DAV:response Element from Section 14 -->
<!ELEMENT response (href, ((href*, status, prop?) | (propstat+)),
responsedescription?) >
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Appendix B. Change Log (to be removed by RFC Editor before publication)
B.1 Since draft-ietf-webdav-redirectref-protocol-02
Julian Reschke takes editorial role (added to authors list). Cleanup
XML indentation. Start adding all unresolved last call issues. Update
some author's contact information. Update references, split into
"normative" and "informational". Remove non-RFC2616 headers
("Public") from examples. Fixed width problems in artwork. Start
resolving editorial issues.
B.2 Since draft-ietf-webdav-redirectref-protocol-03
Added Joe Orton and Juergen Reuter to Acknowledgements section. Close
more editorial issues. Remove dependencies on BIND spec.
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Appendix C. Resolved issues (to be removed by RFC Editor before
publication)
Issues that were either rejected or resolved in this version of this
document.
C.1 lc-07-bind
Type: change
[3]
reuterj@ira.uka.de (2000-02-07): Abstract should discuss only
redirect references, not bindings. Expand discussion of redirect
references.
Resolution: Abstract will discuss only redirect references. See also
issue 34.
C.2 lc-08-bind
Type: change
[4]
reuterj@ira.uka.de (2000-02-07): Get rid of cross-references to the
binding spec: in the abstract, in the introduction, in the definition
of Reference Resource.
Resolution: Cross-references to bindings will be removed. See also
issue 34.
C.3 lc-34-bind
Type: change
[5]
yarong@Exchange.Microsoft.com (2000-02-11): NoBind: Remove all
cross-references to the binding spec. Prefer also removing all
mention of bindings.
Resolution: Agreed. See also issues 7, 8, 14
C.4 lc-83-bind
Type: change
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[6]
reuterj@ira.uka.de (2000-02-22): References: Get rid of the reference
to the bindings spec.
Resolution: Agreed.
C.5 lc-12-bind
Type: change
[7]
reuterj@ira.uka.de (2000-02-07): First 3 paragraphs of Introduction
are identical to those in binding spec. Make sure that any changes
made there are also incorporated here.
Resolution: These paragraphs will change as necessary to make the
redirect spec completely independent of the rest of WebDAV.
C.6 lc-35-bind
Type: change
[8]
yarong@Exchange.Microsoft.com (2000-02-11): ReallyNoBind: Remove
paras. 6 and 8 from Intro.
Resolution: Agreed. See also issue 14.
C.7 lc-01-body
Type: change
[9]
joe@orton.demon.co.uk (2000-01-26): Entity Bodies for Redirect
References: Clarify: Are there 2 resources, one that redirects and
one that responds with its own entity body? Clarify: What is the
effect of PUT for a URI that currently maps to a redirect reference?
Resolution: Redirect resource MUST NOT have a body. See also issue
last call issue 23.
C.8 lc-14-bind
Type: change
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[10]
reuterj@ira.uka.de (2000-02-07): Limit the discussion of bindings to
just what is needed to understand the differences from redirect
references. Maybe the paragraph in the Intro that starts "By
contrast, a BIND request . . ." is all that is needed.
Resolution: Get rid of discussion of bindings altogether. See also
issue 34, 35.
C.9 lc-15-direct-ref
Type: change
[11]
reuterj@ira.uka.de (2000-02-07): Don't define Direct Reference
Resource, since direct references are out of scope. (If you do keep
the definition, say explicitly that a direct reference resource is a
type of reference resource.)
Resolution: Remove definition of Direct Reference Resource. See also
issue 39.
C.10 lc-39-no-reference-or-direct-resource
Type: change
[12]
yarong@Exchange.Microsoft.com (2000-02-11):
NoReferenceOrDirectResource: Remove the definitions of "Reference"
and "Direct Reference Resource." Change the definition of "Redirect
Reference Resource" to be: Redirect Resource: A resource created to
redirect all requests made to it, using 302 (Found), to a defined
target resource.
julian.reschke@greenbytes.de (2003-07-27): (Rename from "redirect
reference resource" to "redirect resource" delayed for now).
Resolution: Agreed. See also issue 15.
C.11 lc-40-direct
Type: change
[13]
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yarong@Exchange.Microsoft.com (2000-02-11): Assorted changes to
Section 4, para 2 to get rid of the word "forward" and the word
"server" and remove comparison with direct references.
Resolution: See also issue 33 (forward). See also issue 36 (server).
Remove discussion of direct references.
C.12 lc-45-apply-to-rr
Type: change
[14]
yarong@Exchange.Microsoft.com (2000-02-11): Suggested replacement
text for this paragraph, which briefly introduces
Apply-To-Redirect-Ref. Includes a note that even with this header,
the response may be a 302.
Resolution: See issue 19 for replacement text. Disagree. Redirect
reference will never respond to Apply-To-RR with 302.
C.13 lc-01A-body
Type: change
[15]
joe@orton.demon.co.uk (2000-01-26): In the definition of MKRESOURCE,
"Body" needs to be defined or else terminology changed.
Resolution: We will use MKREF instead of MKRESOURCE.
C.14 lc-31-MKCOL
Type: edit
[16]
reuterj@ira.uka.de (2000-02-07): Section 6, para on MKRESOURCE and
MKCOL is obvious and doesn't need to be stated. Maybe show in an
example.
Resolution: Agreed. See also issue 48.
C.15 lc-67-redirectref
Type: change
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[17]
reuterj@ira.uka.de (2000-02-14): 7.4: The explanation should not
contrast displaying the properties of the redirect ref with
displaying the properties of its target, but with returning a 302.
Resolution: Revise as recommended.
C.16 lc-54-s10
Type: change
[18]
yarong@Exchange.Microsoft.com (2000-02-11): The Note: in section 10
has the same problem pointed out in Bindings.NoSlash and needs to be
fixed. It contradicts RFC 2518 and 2616, which both assume that a URL
and the same URL + "/" may map to different resources.
Resolution: Agreed in mailing list discussions that no change is
needed.
C.17 lc-78-directory
Type: change
[19]
reuterj@ira.uka.de (2000-02-22): Section 16.4: Change "directory" to
"collection". Not new to this protocol. Holds for any protocol that
has hierarchical access paths.
C.18 lc-82-iana
Type: change
[20]
reuterj@ira.uka.de (2000-02-22): Section 18: Just reference [WebDAV]
and say this protocol does not introduce any new considerations.
Resolution: Simplify, then resolve issue 55.
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Appendix D. Open issues (to be removed by RFC Editor before publication)
D.1 lc-85-301
Type: change
ejw@cse.ucsc.edu (2000-01-03): Support creation of other than 302
redirects, especially 301.
D.2 lc-38-not-hierarchical
Type: change
[21]
yarong@Exchange.Microsoft.com (2000-02-11): Not Hierarchical: The
first sentence of the second paragraph of the introduction of the
redirect spec asserts that the URIs of WebDAV compliant resources
match to collections. The WebDAV standard makes no such requirement.
I therefore move that this sentence be stricken.
Resolution: State the more general HTTP rationale first (alternative
names for the same resource), then introduce the collection hierarchy
rationale, which applies only if you are in a WebDAV-compliant space.
D.3 lc-36-server
Type: change
[22]
yarong@Exchange.Microsoft.com (2000-02-11): Servers: Replace "server"
with "unrelated system" throughout.
Resolution: Try replacing "server" with "host" in some contexts,
rephrasing in passive voice in others. See also issue 40.
D.4 lc-33-forwarding
Type: change
[23]
yarong@Exchange.Microsoft.com (2000-02-11): Forwarding: Replace
"forward" with "redirect" throughout.
Resolution: Use "redirect" for the behavior redirect resources do
exhibit. Use "forward" for the contrasting behavior (passing a method
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on to the target with no client action needed). Define these two
terms. See also issue 40.
D.5 lc-56-notjusthttp
Type: change
[24]
yarong@Exchange.Microsoft.com (2000-02-11): Make it clear in examples
and text that the redirection URI could be non-HTTP.
Resolution: We agree that it is possible to create redirect
references to non-HTTP resources. Add example.
D.6 lc-37-integrity
Type: change
[25]
yarong@Exchange.Microsoft.com (2000-02-11): Integrity: Intro, para 7
"Servers are not required to enforce the integrity of redirect
references." Integrity is not defined. Replace with something
clearer.
Resolution: Rewrite to say that the server MUST NOT update the target
See also issue 6.
D.7 3-terminology-redirectref
Type: change
[26]
julian.reschke@greenbytes.de (2003-07-27): Consider global rename of
"redirect reference resource" to "redirect resource".
D.8 lc-43-webdav
Type: change
[27]
yarong@Exchange.Microsoft.com (2000-02-11): Get rid of the
DAV:reftarget property.
Resolution: DAV:reftarget is readonly and is present only for
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redirect references that are also WebDAV resources. We'll also have a
method for setting target; Redirect-Ref header (returned on all 302
responses) will have the target as its value. See also issue 6, 17,
50.
D.9 lc-19-direct-ref
Type: change
[28]
reuterj@ira.uka.de (2000-02-07): Section 4, para 5 and Section 6,
para 3 discussions of the Apply-to-Redirect-Ref header make it sound
as if we are specifying direct reference behavior.
Resolution: Change these passages so that the contrast is between
applying the method to the redirect reference and responding with a
302.
D.10 lc-04-standard-data-container
Type: change
[29]
joe@orton.demon.co.uk (2000-01-26): "Standard data container" needs
to be defined in the context of MKRESOURCE
Resolution: Not relevant once we switch to MKREF.
D.11 lc-05-standard-data-container
Type: change
[30]
joe@orton.demon.co.uk (2000-01-26): Inconsistency about whether a
"standard data container" can be created with MKRESOURCE or not.
Resolution: Not relevant once we switch to MKREF.
D.12 lc-20-intro-mkresource
Type: change
[31]
reuterj@ira.uka.de (2000-02-07): Section 5: Start with "The new
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MKRESOURCE method" to make it clear that it is being introduced for
the first time here.
Resolution: Say "The MKREF method defined normatively here . . ."
D.13 lc-22-coll
Type: change
[32]
reuterj@ira.uka.de (2000-02-07): Inconsistency about whether
collections can be created with MKRESOURCE.
Resolution: Not relevant for MKREF.
D.14 lc-25-atomic
Type: change
[33]
reuterj@ira.uka.de (2000-02-07): Is MKRESOURCE atomic as viewed by a
client? Can another client access the new resource's properties
before they have been fully initialized? Maybe the MKRESOURCE request
should let the client ask for it to be atomic.
Resolution: No longer relevant once we switch to MKREF with no
request body.
D.15 lc-41-no-webdav
Type: change
[34]
yarong@Exchange.Microsoft.com (2000-02-11): Make redirect references
independent of the rest of WebDAV. The creation method for redirect
references shouldn't require an XML request body.
Resolution: We will make redirect references independent of the rest
of WebDAV. MKREF will not have an XML request body.
D.16 lc-42-no-webdav
Type: change
[35]
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yarong@Exchange.Microsoft.com (2000-02-11): Use a creation method
that creates only redirect references. The MKRESOURCE method hinders
experiment because a user of a server who wishes to add support for
the creation of a new resource type can't simply throw in another
Apache module and allow it to provide the code for the new resource
type. They have to find the code used for MKRESOURCE and change it to
support the new resource type.
Resolution: We will replace MKRESOURCE with MKREF, which creates only
redirect reference resources.
D.17 lc-58-update
Type: change
[36]
yarong@Exchange.Microsoft.com (2000-02-11): There needs to be a way
to update the target of a redirect reference.
Resolution: Agreed. See also issues 6, 43.
D.18 lc-23-body
Type: change
[37]
reuterj@ira.uka.de (2000-02-07): Section 5.1: Get rid of the
statement that the body of the resource is empty (PostConditions). It
would be good if the response to GET included a response body that
could be shown to a user by a client that doesn't do automatic
redirection. There is a related problem in Section 6 on PUT. It is
wrong to assume that what is PUT to a resource is what GET will
return. In Section 6, say "A PUT with Apply-To-RR MAY contain a
request body. The semantics of the request body is out of scope for
this specification..." Also fix the discussion of example 6.2.
Resolution: Redirect references cannot have bodies. GET with
Apply-To-RR MUST fail with 403. PUT with Apply-To-RR MUST fail with
403. See also issue 1.
D.19 lc-24-properties
Type: change
[38]
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reuterj@ira.uka.de (2000-02-07): Section 5.1: Replace the sentence
"The properties of the new resource are as specified by the
DAV:propertyupdate request body, using PROPPATCH semantics" with the
following: "The MKRESOURCE request MAY contain a DAV:propertyupdate
request body to initialize resource properties. Herein, the semantics
is the same as when sending a MKRESOURCE request without a request
body, followed by a PROPPATCH with the DAV:propertyupdate request
body."
Resolution: No longer relevant once we switch to MKREF with no
request body.
D.20 lc-47-207
Type: change
[39]
yarong@Exchange.Microsoft.com (2000-02-11): In line with his wish to
get rid of the request message body of MKRESOURCE, 207 would not be
an appropriate response code. The description of 409 might lead
someone to believe that you can't create redirect references outside
of WebDAV namespaces. Suggests a different description.
Resolution: No longer relevant - MKREF can't get a 207 response.
Revise to make it clear that the first condition will only occur in
WebDAV-compliant namespaces.
D.21 lc-48-s6
Type: change
[40]
yarong@Exchange.Microsoft.com (2000-02-11): Replace all of section 6
with just this: A redirect resource, upon receiving a request without
an Apply-To-Redirect-Ref header, MUST respond with a 302 (Found)
response. The 302 (Found) response MUST include a location header
identifying the target and a Redirect-Ref header. If a redirect
resource receives a request with an Apply-To-Redirect-Ref header then
the redirect reference resource MUST apply the method to itself
rather than blindly returning a 302 (Found) response.
Resolution: Keep a summary along the lines of Yaron's proposal (don't
use the word "blindly"). Keep the bullets detailing the headers to be
returned. Delete the rest, including the examples. See also issue 28,
29, 30, 31, 32.
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D.22 lc-28-lang
Type: edit
[41]
reuterj@ira.uka.de (2000-02-07): Section 6: Get rid of the sentence
"A reference-aware WebDAV client can act on this response in one of
two ways." A client can act on the response in any way it wants.
Resolution: Agreed. See also issue 48.
D.23 lc-29-lang
Type: edit
[42]
reuterj@ira.uka.de (2000-02-07): Section 6, para 4: Obvious, doesn't
need to be stated. Maybe note in an example.
Resolution: Agreed. See also issue 48.
D.24 lc-49-put
Type: change
[43]
yarong@Exchange.Microsoft.com (2000-02-11): Remove the last sentence
of Example 6.2, which says that PUT replaces the reference with a
different resource.
Resolution: No longer relevant. Deleted this example in response to
issue 48.
D.25 lc-44-pseudo
Type: change
[44]
yarong@Exchange.Microsoft.com (2000-02-11): Instead of adding an
optional prop XML element to the response element in 207 responses,
define a new location XML element and a new refresource XML element.
Resolution: Agree to define new XML elements that are not
pseudo-properties. Disagreement about whether refresource is needed.
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See issue 61.
D.26 lc-61-pseudo
Type: change
[45]
reuterj@ira.uka.de (2000-02-14): Section 7: It doesn't make sense to
ask future editors of RFC 2518 to define DAV:location with the
semantics it has here. RFC 2518 should provide the information in the
Location header somehow in multistatus responses, but not by using
properties.
Resolution: Define an XML element for location that is not a
pseudo-property. We'll keep the recommendation that RFC 2518 add this
for 302 responses. See also issue 44.
D.27 lc-60-ex
Type: change
[46]
reuterj@ira.uka.de (2000-02-14): Section 7, para 3: Make it clear
that these are just examples of client behavior, and are not meant to
limit the client's behavior to these options.
Resolution: Agreed to delete this paragraph. Continue discussion of
what information should be returned with 302 in multistatus. Just
location? Also redirectref?
D.28 lc-62-oldclient
Type: change
[47]
reuterj@ira.uka.de (2000-02-14): Section 7: It's too strong to claim
that non-referencing clients can't process 302 responses occurring in
Multi-Status responses. They just have an extra round trip for each
302.
Resolution: Remove last sentence of the paragraph that recommends
changes to RFC 2518.
D.29 lc-63-move
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Type: change
[48]
reuterj@ira.uka.de (2000-02-14): Section 7.1: Is MOVE atomic from the
perspective of a client? Agrees that there should be no 302s for
member redirect references, but finds the rationale dubious.
Resolution: Remove 7.1. Reword 7.2 to avoid concerns with "poses
special problems" and "due to atomicity".
D.30 lc-06-reftarget-relative
Type: change
[49]
joe@orton.demon.co.uk (2000-01-29): Why does the spec talk about
relative URIs in DAV:reftarget in MKRESOURCE requests? Is the server
required to resolve the relative URI and store it as absolute? Is the
server required to keep DAV:reftarget pointing to the target resource
as the reference / target move, or is DAV:reftarget a dead property?
Resolution: DAV:reftarget is readonly and present only on redirect
references that are also WebDAV resources. Add a method for setting
the target. Change definition of Redirect-Ref header so that it has
the target as its value (comes back on all 302 responses). Server
MUST store the target exactly as it is set. It MUST NOT resolve
relatives to absolutes and MUST NOT update if target resource moves.
See also issue 17, 43, 50, 57
D.31 lc-57-noautoupdate
Type: change
[50]
yarong@Exchange.Microsoft.com (2000-02-11): Add language to forbid
servers from automatically updating redirect resources when their
targets move.
Resolution: Agreed. See also issue 6.
D.32 lc-71-relative
Type: change
[51]
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reuterj@ira.uka.de (2000-02-14): Section 9: Base URI should be the
Request-URI or href minus its final segment.
Resolution: Fix this.
D.33 lc-53-s10
Type: change
[52]
yarong@Exchange.Microsoft.com (2000-02-11): The behavior described in
this section would have a very serious impact on the efficiency of
mapping Request-URIs to resources in HTTP request processing. Also
specify another type of redirect resource that does not behave as in
section 10, but instead would "expose the behavior we see today in
various HTTP servers that allow their users to create 300 resources."
Be sure we know what behavior will be if the redirect location is not
an HTTP URL, but, say ftp.
Resolution: We won't define 2 sorts of redirect references here.
Servers SHOULD respond with 302 as described here, but if they can't
do that, respond with 404 Not Found. (It's hard to modularize the
behavior specified - it impacts processing Not Found cases of all
methods, so you can't just add it to an HTTP server in a redirect ref
module.)
D.34 lc-72-trailingslash
Type: change
[53]
reuterj@ira.uka.de (2000-02-14): Section 10: Forbid DAV:reftarget
from ending in "/"
Resolution: Make the note warn about the possibility of two slashes
in a row, recommend against ending target with a slash, since that
could result in two slashes in a row.
D.35 lc-50-blindredirect
Type: change
[54]
yarong@Exchange.Microsoft.com (2000-02-11): Replace current language
explaining the purpose of the Redirect-Ref header with language that
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simply states that it marks blind 302 responses from redirect
resources. (Section 6.3, 11.1)
Resolution: Section 6.3 was removed in response to issue 48. In 11.1,
change the definition of the Redirect-Ref header to have the value of
the target (relative URI) as its value. Then we don't need a method
for retrieving the target's relative URI. Presence of the
Redirect-Ref header lets the client know that the resource accepts
Apply-To-RR header and the new method for updating target. Reject
Yaron's suggested language, but make the above changes.
D.36 lc-74-terminology
Type: change
[55]
reuterj@ira.uka.de (2000-02-14): "plain HTTP/1.1 redirect" - find
some good name for this an use it consistently
D.37 lc-75-ignore
Type: change
[56]
reuterj@ira.uka.de (2000-02-14): 11.2: "If the Apply-To-Redirect-Ref
header is used on a request to any other sort of resource besides a
redirect reference resource, the server SHOULD ignore it." Don't need
to say this since HTP already says that any header that is not
understood should be ignored.
D.38 lc-76-location
Type: change
[57]
reuterj@ira.uka.de (2000-02-22): 12.2: Make DAV:location a real
(live) property, get rid of the DAV:reftarget property
D.39 lc-79-accesscontrol
Type: change
[58]
reuterj@ira.uka.de (2000-02-22): Section 16.4: "In some environments,
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the owner of a resource might be able to use access control to
prevent others from creating references to that resource." That would
not be consistent with the concept of redirect references as weak
links (e.g. think of moving a resource to a different locationo that
is already the target of some redirection reference.
D.40 lc-80-i18n
Type: change
[59]
reuterj@ira.uka.de (2000-02-22): Section 17: Could get rid of a lot
of this section, since this protocol extends WebDAV. Just reference
[WebDAV].
D.41 lc-55-iana
Type: change
[60]
yarong@Exchange.Microsoft.com (2000-02-11): Expand the IANA section
to list all methods, headers, XML elements, MIME types, URL schemes,
etc., defined by the spec.
Resolution: Agreed.
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