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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 RFC 4437

WEBDAV Working Group                                        J. Whitehead
Internet-Draft                                           U.C. Santa Cruz
Expires: May 17, 2004                                           G. Clemm
                                                                     IBM
                                                         J. Reschke, Ed.
                                                              greenbytes
                                                       November 17, 2003


                  WebDAV Redirect Reference Resources
               draft-ietf-webdav-redirectref-protocol-07

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on May 17, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   This specification defines redirect reference resources.  A redirect
   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



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   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 . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.   Notational Conventions . . . . . . . . . . . . . . . . . . .   6
   3.   Terminology  . . . . . . . . . . . . . . . . . . . . . . . .   7
   4.   Overview of Redirect Reference Resources . . . . . . . . . .   8
   5.   Creating a Redirect Reference Resource . . . . . . . . . . .   9
   5.1  MKRESOURCE . . . . . . . . . . . . . . . . . . . . . . . . .   9
   5.2  Example: Creating a Redirect Reference Resource with
        MKRESOURCE . . . . . . . . . . . . . . . . . . . . . . . . .  10
   6.   Operations on Redirect Reference Resources . . . . . . . . .  12
   7.   Operations on Collections That Contain Redirect Reference
        Resources  . . . . . . . . . . . . . . . . . . . . . . . . .  13
   7.1  LOCK on a Collection That Contains Redirect References . . .  13
   7.2  Example: PROPFIND on a Collection with Redirect Reference
        Resources  . . . . . . . . . . . . . . . . . . . . . . . . .  13
   7.3  Example: PROPFIND with Apply-To-Redirect-Ref on a
        Collection with Redirect Reference Resources . . . . . . . .  16
   7.4  Example: COPY on a Collection That Contains a Redirect
        Reference Resource . . . . . . . . . . . . . . . . . . . . .  17
   7.5  Example: LOCK on a Collection That Contains a Redirect
        Reference Resource . . . . . . . . . . . . . . . . . . . . .  18
   8.   Operations on Targets of Redirect Reference Resources  . . .  20
   9.   Relative URIs in DAV:reftarget . . . . . . . . . . . . . . .  21
   9.1  Example: Resolving a Relative URI in a Multi-Status
        Response . . . . . . . . . . . . . . . . . . . . . . . . . .  21
   10.  Redirect References to Collections . . . . . . . . . . . . .  23
   11.  Headers  . . . . . . . . . . . . . . . . . . . . . . . . . .  25
   11.1 Redirect-Ref Response Header . . . . . . . . . . . . . . . .  25
   11.2 Apply-To-Redirect-Ref Request Header . . . . . . . . . . . .  25
   12.  Properties . . . . . . . . . . . . . . . . . . . . . . . . .  26
   12.1 reftarget Property . . . . . . . . . . . . . . . . . . . . .  26
   13.  XML Elements . . . . . . . . . . . . . . . . . . . . . . . .  27
   13.1 redirectref XML Element  . . . . . . . . . . . . . . . . . .  27
   14.  Extensions to the DAV:response XML Element for
        Multi-Status Responses . . . . . . . . . . . . . . . . . . .  28
   15.  Capability Discovery . . . . . . . . . . . . . . . . . . . .  29
   15.1 Example: Discovery of Support for Redirect Reference
        Resources  . . . . . . . . . . . . . . . . . . . . . . . . .  29
   16.  Security Considerations  . . . . . . . . . . . . . . . . . .  30
   16.1 Privacy Concerns . . . . . . . . . . . . . . . . . . . . . .  30



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   16.2 Redirect Loops . . . . . . . . . . . . . . . . . . . . . . .  30
   16.3 Redirect Reference Resources and Denial of Service . . . . .  30
   16.4 Revealing Private Locations  . . . . . . . . . . . . . . . .  30
   17.  Internationalization Considerations  . . . . . . . . . . . .  32
   18.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  33
   19.  Contributors . . . . . . . . . . . . . . . . . . . . . . . .  34
   20.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  35
        Normative References . . . . . . . . . . . . . . . . . . . .  36
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  36
   A.   Changes to the WebDAV Document Type Definition . . . . . . .  38
   B.   Change Log (to be removed by RFC Editor before
        publication) . . . . . . . . . . . . . . . . . . . . . . . .  39
   B.1  Since draft-ietf-webdav-redirectref-protocol-02  . . . . . .  39
   B.2  Since draft-ietf-webdav-redirectref-protocol-03  . . . . . .  39
   B.3  Since draft-ietf-webdav-redirectref-protocol-04  . . . . . .  39
   B.4  Since draft-ietf-webdav-redirectref-protocol-05  . . . . . .  39
   B.5  Since draft-ietf-webdav-redirectref-protocol-06  . . . . . .  39
   C.   Resolved issues (to be removed by RFC Editor before
        publication) . . . . . . . . . . . . . . . . . . . . . . . .  40
   C.1  lc-19-direct-ref . . . . . . . . . . . . . . . . . . . . . .  40
   C.2  rfc2606-compliance . . . . . . . . . . . . . . . . . . . . .  40
   C.3  lc-28-lang . . . . . . . . . . . . . . . . . . . . . . . . .  40
   C.4  lc-29-lang . . . . . . . . . . . . . . . . . . . . . . . . .  40
   C.5  lc-44-pseudo . . . . . . . . . . . . . . . . . . . . . . . .  41
   C.6  lc-61-pseudo . . . . . . . . . . . . . . . . . . . . . . . .  41
   C.7  lc-62-oldclient  . . . . . . . . . . . . . . . . . . . . . .  41
   C.8  lc-63-move . . . . . . . . . . . . . . . . . . . . . . . . .  42
   C.9  lc-53-s10  . . . . . . . . . . . . . . . . . . . . . . . . .  42
   C.10 lc-76-location . . . . . . . . . . . . . . . . . . . . . . .  42
   C.11 lc-80-i18n . . . . . . . . . . . . . . . . . . . . . . . . .  43
   D.   Open issues (to be removed by RFC Editor before
        publication) . . . . . . . . . . . . . . . . . . . . . . . .  44
   D.1  old_clients  . . . . . . . . . . . . . . . . . . . . . . . .  44
   D.2  lc-85-301  . . . . . . . . . . . . . . . . . . . . . . . . .  44
   D.3  lc-38-not-hierarchical . . . . . . . . . . . . . . . . . . .  45
   D.4  lc-36-server . . . . . . . . . . . . . . . . . . . . . . . .  45
   D.5  lc-33-forwarding . . . . . . . . . . . . . . . . . . . . . .  45
   D.6  lc-37-integrity  . . . . . . . . . . . . . . . . . . . . . .  46
   D.7  3-terminology-redirectref  . . . . . . . . . . . . . . . . .  46
   D.8  lc-41-no-webdav  . . . . . . . . . . . . . . . . . . . . . .  46
   D.9  lc-58-update . . . . . . . . . . . . . . . . . . . . . . . .  46
   D.10 lc-24-properties . . . . . . . . . . . . . . . . . . . . . .  47
   D.11 lc-48-s6 . . . . . . . . . . . . . . . . . . . . . . . . . .  47
   D.12 lc-57-noautoupdate . . . . . . . . . . . . . . . . . . . . .  47
   D.13 12.1-property-name . . . . . . . . . . . . . . . . . . . . .  48
   D.14 lc-55-iana . . . . . . . . . . . . . . . . . . . . . . . . .  48
        Index  . . . . . . . . . . . . . . . . . . . . . . . . . . .  49
        Intellectual Property and Copyright Statements . . . . . . .  50



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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 with properties but no body of its
   own.  Properties of a redirect reference resource can contain such
   information as who created the reference, when, and why. Since



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   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. A target resource can be anything that can be identified
      by an absolute URI (see [RFC2396], "absoluteURI").






























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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, 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
   standard HTTP/WebDAV behaviour (redirection with a 3xx status code)
   should occur.  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 new MKRESOURCE method is used to create new redirect reference
   resources.  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 redirect reference
   resource and initialization of its properties 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], specifying a DAV:resourcetype of "DAV:redirectref".

   Postconditions:

      If the response status code is 201, a new resource exists at the
      Request-URI.

      The properties of the new resource are as specified by the
      DAV:propertyupdate request body, using PROPPATCH semantics.

      If the response status code is not 201, then a new resource is not
      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.



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      The following status codes can be expected in responses to
      MKRESOURCE:

      201 (Created): The new resource was successfully created.

      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.example.com
   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>/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 http://www.example.com/~whitehead/dav/spec08.ref, which
   points to the resource identified by the DAV:reftarget property. In



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   this example, the target resource is identified by the URI http://
   www.example.com/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 specifying "T". 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, 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: T" header in order to operate on the
   reference resource itself. In this case, the request MUST be applied
   to the reference resource itself, and a 302 response MUST NOT be
   returned.

   As redirect references do not have bodies, GET and PUT requests with
   "Apply-To-Redirect-Ref: T" MUST fail with status 403 (forbidden).




















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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: T" header is included
   with the request.  The overall response will therefore be a 207
   (Multi-Status). For each DAV:response element representing a redirect
   reference, the server MUST include an additional DAV:location
   element, specifying the value of the "Location" header that would be
   returned otherwise. The extension is defined in Section 14 below.

   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 LOCK on a Collection That Contains Redirect References

   An attempt to lock (with Depth: infinity) a collection that contains
   redirect references without specifying "Apply-To-Redirect-Ref: T"
   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.

7.2 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:

   /MyCollection/
        (non-reference resource) diary.html
        (redirect reference resource) nunavut













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   >> Request:

   PROPFIND /MyCollection/ HTTP/1.1
   Host: example.com
   Depth: infinity
   Apply-To-Redirect-Ref: F
   Content-Type: text/xml
   Content-Length: xxxx

   <?xml version="1.0" ?>
   <D:propfind xmlns:D="DAV: ">
     <D:prop xmlns:J="http://example.com/jsprops/">
       <D:resourcetype/>
       <J:keywords/>
     </D:prop>
   </D:propfind>



































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   >> 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://example.com/jsprops/">
     <D:response>
       <D:href>/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>/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>/MyCollection/nunavut</D:href>
       <D:status>HTTP/1.1 302 Found</D:status>
       <D:location>
         <D:href>http://example.ca/art/inuit/</D:href>
       </D:location>
     </D:response>
   </D:multistatus>

   In this example the Depth header is set to infinity, and the
   Apply-To-Redirect-Ref header is set to "F".  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:location extension element 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.)




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7.3 Example: PROPFIND with Apply-To-Redirect-Ref on a Collection with
    Redirect Reference Resources

   Suppose a PROPFIND request with "Apply-To-Redirect-Ref: T" and Depth:
   infinity is submitted to the following collection, with the members
   shown here:

   /MyCollection/
        (non-reference resource) diary.html
        (redirect reference resource) nunavut

   >> Request:

   PROPFIND /MyCollection/ HTTP/1.1
   Host: example.com
   Depth: infinity
   Apply-To-Redirect-Ref: T
   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>/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>



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     </D:response>
     <D:response>
       <D:href>/MyCollection/diary.html</D:href>
       <D:propstat>
         <D:prop>
           <D:resourcetype/>
         </D:prop>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat>
       <D:propstat>
         <D:prop><D:reftarget/></D:prop>
         <D:status>HTTP/1.1 404 Not Found</D:status>
       </D:propstat>
     </D:response>
     <D:response>
       <D:href>/MyCollection/nunavut</D:href>
       <D:propstat>
         <D:prop>
           <D:resourcetype><D:redirectref/></D:resourcetype>
           <D:reftarget>
             <D:href>http://example.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: T" header is present, the response
   shows the properties of the redirect reference resource in the
   collection rather than reporting a 302 status.

7.4 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









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   >> Request:

   COPY /MyCollection/ HTTP/1.1
   Host: example.com
   Depth: infinity
   Destination: http://example.com/OtherCollection/

   >> Response:

   HTTP/1.1 207 Multi-Status
   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>/MyCollection/nunavut</D:href>
       <D:status>HTTP/1.1 302 Found</D:status>
       <D:location>
         <D:href>http://example.com//Someplace/nunavut.map</D:href>
       </D:location>
     </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


7.5 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









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   >> Request:

   LOCK /MyCollection/ HTTP/1.1
   Host: example.com
   Apply-To-Redirect-Ref: F
   Content-Type: text/xml

   <?xml version="1.0" ?>
   <D:lockinfo xmlns:D="DAV:">
     <D:lockscope><D:exclusive/></D:lockscope>
     <D:locktype><D:write/></D:locktype>
   </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>/MyCollection/</D:href>
       <D:status>HTTP/1.1 424 Failed Dependency</D:status>
     </D:response>
     <D:response>
       <D:href>/MyCollection/diary.html</D:href>
       <D:status>HTTP/1.1 424 Failed Dependency</D:status>
     </D:response>
     <D:response>
       <D:href>/MyCollection/nunavut</D:href>
       <D:status>HTTP/1.1 302 Found</D:status>
       <D:location>
         <D:href>http://example.ca/art/inuit/</D:href>
       </D:location>
     </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 element 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 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 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 Multi-Status Response

   >> Request:

   PROPFIND /geog/ HTTP/1.1
   Host: example.com
   Apply-To-Redirect-Ref: T
   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>















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   >> 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>
       <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://example.com/geog/stats.html.  This is
   the base URI for resolving the relative URI in reftarget.  The
   absolute URI of reftarget is http://example.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 SHOULD be 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.

      Note: the behavior described above may have a very serious impact
      on the efficiency of mapping Request-URIs to resources in HTTP
      request processing. Therefore servers MAY respond with a 404
      status code if the cost of checking all leading path segments for
      redirect references seems prohibitive.









































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11. Headers

11.1 Redirect-Ref Response Header

   Redirect-Ref = "Redirect-Ref:" (absoluteURI | relativeURI)
                  ; see sections 3 and 5 of [RFC2396]

   The Redirect-Ref header is used in all 302 responses from redirect
   reference resources. The value is the (possibly relative) URI of the
   link target as specified during redirect reference resource creation.

11.2 Apply-To-Redirect-Ref Request Header

   Apply-To-Redirect-Ref = "Apply-To-Redirect-Ref" ":" ("T" | "F")

   The optional Apply-To-Redirect-Ref header can be used on any request
   to a redirect reference resource.  When it is present and set to "T",
   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
   MUST 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 >































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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 element 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.

   Consequently, the definition of the DAV:response XML element changes
   to the following:

   <!ELEMENT response (href, ((href*, status)|(propstat+)),
                       responsedescription?, location?) >
   <!ELEMENT location (href) >





































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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 header and 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: example.org

   >> Response:

   HTTP/1.1 200 OK
   Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE
   Allow: 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.













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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.)

   This risk is no greater than the similar risk posed by HTML links.












































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17. Internationalization Considerations

   All internationalization considerations mentioned in [RFC2518] also
   apply to this document.















































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18. IANA Considerations

   All IANA considerations mentioned in [RFC2518] also apply to this
   document.















































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19. Contributors

   Many thanks to Jason Crawford, Jim Davis, Chuck Fay and Judith Slein
   who can take credit for big parts of the original design of this
   specification.














































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20. Acknowledgements

   This document 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

   [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.

   [1]  <mailto:w3c-dist-auth@w3.org>

   [2]  <mailto:w3c-dist-auth-request@w3.org?subject=subscribe>


Authors' Addresses

   Jim Whitehead
   UC Santa Cruz, Dept. of Computer Science
   1156 High Street
   Santa Cruz, CA  95064
   US

   EMail: ejw@cse.ucsc.edu


   Geoff Clemm
   IBM
   20 Maguire Road
   Lexington, MA  02421
   US

   EMail: geoffrey.clemm@us.ibm.com











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   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.

B.3 Since draft-ietf-webdav-redirectref-protocol-04

   More editorial fixes. Clarify that MKRESOURCE can only be used to
   create redirect references (switch to new method in a future draft).
   Clarify that redirect references do not have bodies.

B.4 Since draft-ietf-webdav-redirectref-protocol-05

   Close (accept) issue "lc-79-accesscontrol". Add issue
   "rfc2606-compliance". Close issues "lc-50-blindredirect",
   "lc-71-relative", "lc-74-terminology". Update contact info for Geoff
   Clemm. Moved some of the original authors names to new Contributors
   section. Add and close issue "9-MKRESOURCE-vs-relative-URI".  Close
   issue "lc-72-trailingslash".  Close issue "lc-60-ex". Update issue
   "lc-85-301" with proposal. Close issue "lc-06-reftarget-relative"
   (9-MKRESOURCE-vs-relative-URI was a duplicate of this one). Also
   remove section 9.1 (example for MKRESOURCE vs relative URIs).  Add
   and resolve issue "11.2-apply-to-redirect-ref-syntax" (header now has
   values "T" and "F"). Also some cleanup for "rfc2606-compliance".
   Typo fixes. Add and resolve "15.1-options-response".

B.5 Since draft-ietf-webdav-redirectref-protocol-06

   Resolve issues "lc-19-direct-ref", "lc-28-lang", "lc-29-lang",
   "lc-44-pseudo", "lc-53-s10", "lc-61-pseudo", "lc-63-move",
   "lc-80-i18n" and "rfc2606-compliance". Start work on index. Add new
   issue "old_clients".








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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-19-direct-ref

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0266.html>

   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 (2003-11-04): Change these passages so that the contrast
   is between applying the method to the redirect reference and
   responding with a 302.

C.2 rfc2606-compliance

   Type: editor

   julian.reschke@greenbytes.de (2003-10-02): Ensure that examples use
   only sample domains as per RFC2606.

C.3 lc-28-lang

   Type: edit

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0266.html>

   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 (2003-11-04): Agreed. See also issue 48.

C.4 lc-29-lang

   Type: edit

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0266.html>




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   reuterj@ira.uka.de (2000-02-07): Section 6, para 4: Obvious, doesn't
   need to be stated. Maybe note in an example.

   Resolution (2003-11-04): Agreed. See also issue 48.

C.5 lc-44-pseudo

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0302.html>

   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.
   See issue 61.

C.6 lc-61-pseudo

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0316.html>

   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 (2003-10-31): 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.

C.7 lc-62-oldclient

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0316.html>

   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.



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   Resolution (2003-10-31): Remove last sentence of the paragraph that
   recommends changes to RFC 2518.

C.8 lc-63-move

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0316.html>

   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 (2003-11-11): Remove 7.1. Reword 7.2 to avoid concerns
   with "poses special problems" and "due to atomicity".

C.9 lc-53-s10

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0304.html>

   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 (2003-11-04): 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.)

C.10 lc-76-location

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0359.html>

   reuterj@ira.uka.de (2000-02-22): 12.2: Make DAV:location a real



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   (live) property, get rid of the DAV:reftarget property

   Resolution (2003-10-31): Pseudo-property was removed.

C.11 lc-80-i18n

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0359.html>

   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].

   julian.reschke@greenbytes.de (2003-10-02): True, but I note that
   other specs have re-stated these considerations as well. Opinions?

   Resolution (2003-11-11): Just point to RFC2518. Remove RFC2277 and
   XML from references (not needed anymore).































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Appendix D. Open issues (to be removed by RFC Editor before publication)

D.1 old_clients

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2003OctDec/
   0180.html>

   julian.reschke@greenbytes.de (2003-11-10): There are (at least) two
   major design goals, but unfortunately both are in direct
   contradiction: #1: Maximum consistency with HTTP/1.1 (RFC2616). This
   means that any request that addresses a redirect reference resource
   MUST result in a 3xx status code (obviously the whole point is that
   GET MUST result in a redirection, and if it does, it's hard to say
   why other methods such as PUT or DELETE should behave differently).
   Therefore, the redirect reference protocol introduces a new request
   header ("Apply-To-Redirect-Ref") through which a client can indicate
   that the request indeed should be applied to the redirect reference
   resource itself. #2: Maximum usability with existing clients. For
   instance, the Microsoft Webfolder client will not be able to DELETE a
   redirect reference resource unless the server deviates from #1. Right
   now I'm not sure about the best way to resolve this. Currently the
   spec chooses #1 (back when this decision was made, there was probably
   the assumption that existing clients would quickly be updated --
   something that probably isn't true today). However this may result in
   implementers either just ignoring these rules, or adding special
   workarounds based on "User Agent" detection.

D.2 lc-85-301

   Type: change

   ejw@cse.ucsc.edu (2000-01-03): Support creation of other than 302
   redirects, especially 301.

   julian.reschke@greenbytes.de (2003-10-13): HTTP seems to distinguish
   the following use cases: (a) permanent redirect (301), (b) temporary
   redirect (302 or 307), (c) redirect to a GET location after POST
   (303) and (d) agent-driven negotiation (300). Among these, (a) and
   (b) seem to be well understood, so we should support both. (c)
   doesn't seem to be applicable. (d) may become interesting when user
   agents start supporting it, so the spec should be flexible enough to
   support a feature extension for that. For now I propose that the
   client is able to specify the redirection type as a resource type,
   such as "DAV:permanent-redirect-reference" and
   "DAV:temporary-redirect-reference". This spec would only define the
   behaviour for these two resource types and would allow future



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   extensions using new resource types and suggested response codes.

D.3 lc-38-not-hierarchical

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0289.html>

   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.4 lc-36-server

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0285.html>

   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.5 lc-33-forwarding

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0284.html>

   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
   on to the target with no client action needed). Define these two
   terms. See also issue 40.





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D.6 lc-37-integrity

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0288.html>

   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

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0290.html>

   julian.reschke@greenbytes.de (2003-07-27): Consider global rename of
   "redirect reference resource" to "redirect resource".

D.8 lc-41-no-webdav

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0292.html>

   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.9 lc-58-update

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0308.html>

   yarong@Exchange.Microsoft.com (2000-02-11): There needs to be a way
   to update the target of a redirect reference.



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   Resolution: Agreed. See also issues 6, 43.

D.10 lc-24-properties

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0266.html>

   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.11 lc-48-s6

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0298.html>

   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.

D.12 lc-57-noautoupdate

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0307.html>



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   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.13 12.1-property-name

   Type: change

   julian.reschke@greenbytes.de (2003-10-06): Sync names for
   DAV:reftarget property and "Redirect-Ref" response headers.

D.14 lc-55-iana

   Type: change

   <http://lists.w3.org/Archives/Public/w3c-dist-auth/2000JanMar/
   0305.html>

   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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Index

A
   Apply-To-Redirect-Ref header  25

D
   DAV header
      compliance class 'redirectrefs'  29
   DAV:redirectref resource type  27
   DAV:reftarget property  26

H
   Headers
      Apply-To-Redirect-Ref  25
      Redirect-Ref  25

M
   Methods
      MKRESOURCE  9
   MKRESOURCE method  9

P
   Properties
      DAV:reftarget  26

R
   Redirect-Ref header  25
   Resource Types
      DAV:redirectref  27






















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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgment

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