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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: April 21, 2005                                         G. Clemm
                                                                     IBM
                                                         J. Reschke, Ed.
                                                              greenbytes
                                                        October 21, 2004



  Web Distributed Authoring and Versioning (WebDAV) Redirect Reference
                               Resources
               draft-ietf-webdav-redirectref-protocol-10


Status of this Memo


   This document is an Internet-Draft and is subject to all provisions
   of section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.


   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 April 21, 2005.


Copyright Notice


   Copyright (C) The Internet Society (2004).


Abstract


   This specification defines redirect reference resources.  A redirect
   reference resource is a resource whose default response is an
   HTTP/1.1 3xx (Redirection) status code (see RFC2616, Section 10.3),




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   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.


Editorial Note (To be removed by RFC Editor before publication)


   Distribution of this document is unlimited.  Please send comments to
   the Distributed Authoring and Versioning (WebDAV) working group at
   <mailto:w3c-dist-auth@w3.org>, which may be joined by sending a
   message with subject "subscribe" to
   <mailto:w3c-dist-auth-request@w3.org>.  Discussions of the WEBDAV
   working group are archived at
   <http://lists.w3.org/Archives/Public/w3c-dist-auth/>.


   An issues list and XML and HTML versions of this draft are available
   from
   <http://greenbytes.de/tech/webdav/#draft-ietf-webdav-redirectref-prot
   ocol>.
































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Table of Contents


   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   5
   2.   Notational Conventions . . . . . . . . . . . . . . . . . . .   6
   3.   Terminology  . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.   Overview of Redirect Reference Resources . . . . . . . . . .   7
   5.   Operations on Redirect Reference Resources . . . . . . . . .   8
   6.   MKREDIRECTREF Method . . . . . . . . . . . . . . . . . . . .   8
     6.1  Example: Creating a Redirect Reference Resource with
          MKREDIRECTREF  . . . . . . . . . . . . . . . . . . . . . .  10
   7.   UPDATEREDIRECTREF Method . . . . . . . . . . . . . . . . . .  10
     7.1  Example: Updating a Redirect Reference Resource with
          UPDATEREDIRECTREF  . . . . . . . . . . . . . . . . . . . .  12
   8.   Operations on Collections That Contain Redirect Reference
        Resources  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     8.1  LOCK on a Collection That Contains Redirect References . .  12
     8.2  Example: PROPFIND on a Collection with Redirect
          Reference Resources  . . . . . . . . . . . . . . . . . . .  13
     8.3  Example: PROPFIND with Apply-To-Redirect-Ref on a
          Collection with Redirect Reference Resources . . . . . . .  15
     8.4  Example: COPY on a Collection That Contains a Redirect
          Reference Resource . . . . . . . . . . . . . . . . . . . .  16
     8.5  Example: LOCK on a Collection That Contains a Redirect
          Reference Resource . . . . . . . . . . . . . . . . . . . .  17
   9.   Operations on Targets of Redirect Reference Resources  . . .  19
   10.  Relative URIs in DAV:reftarget . . . . . . . . . . . . . . .  19
     10.1   Example: Resolving a Relative URI in a Multi-Status
            Response . . . . . . . . . . . . . . . . . . . . . . . .  19
   11.  Redirect References to Collections . . . . . . . . . . . . .  20
   12.  Headers  . . . . . . . . . . . . . . . . . . . . . . . . . .  22
     12.1   Redirect-Ref Response Header . . . . . . . . . . . . . .  22
     12.2   Apply-To-Redirect-Ref Request Header . . . . . . . . . .  22
   13.  Redirect Reference Resource Properties . . . . . . . . . . .  22
     13.1   DAV:redirect-lifetime (protected)  . . . . . . . . . . .  22
     13.2   DAV:reftarget (protected)  . . . . . . . . . . . . . . .  23
   14.  XML Elements . . . . . . . . . . . . . . . . . . . . . . . .  23
     14.1   redirectref XML Element  . . . . . . . . . . . . . . . .  23
   15.  Extensions to the DAV:response XML Element for
        Multi-Status Responses . . . . . . . . . . . . . . . . . . .  23
   16.  Capability Discovery . . . . . . . . . . . . . . . . . . . .  23
     16.1   Example: Discovery of Support for Redirect Reference
            Resources  . . . . . . . . . . . . . . . . . . . . . . .  24
   17.  Security Considerations  . . . . . . . . . . . . . . . . . .  24
     17.1   Privacy Concerns . . . . . . . . . . . . . . . . . . . .  24
     17.2   Redirect Loops . . . . . . . . . . . . . . . . . . . . .  25
     17.3   Redirect Reference Resources and Denial of Service . . .  25
     17.4   Revealing Private Locations  . . . . . . . . . . . . . .  25
   18.  Internationalization Considerations  . . . . . . . . . . . .  25




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   19.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  26
   20.  Contributors . . . . . . . . . . . . . . . . . . . . . . . .  26
   21.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  26
   22.  Normative References . . . . . . . . . . . . . . . . . . . .  26
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  27
   A.   Changes to the WebDAV Document Type Definition . . . . . . .  27
   B.   Change Log (to be removed by RFC Editor before
        publication) . . . . . . . . . . . . . . . . . . . . . . . .  28
     B.1  Since draft-ietf-webdav-redirectref-protocol-02  . . . . .  28
     B.2  Since draft-ietf-webdav-redirectref-protocol-03  . . . . .  28
     B.3  Since draft-ietf-webdav-redirectref-protocol-04  . . . . .  28
     B.4  Since draft-ietf-webdav-redirectref-protocol-05  . . . . .  28
     B.5  Since draft-ietf-webdav-redirectref-protocol-06  . . . . .  28
     B.6  Since draft-ietf-webdav-redirectref-protocol-07  . . . . .  28
     B.7  Since draft-ietf-webdav-redirectref-protocol-08  . . . . .  29
     B.8  Since draft-ietf-webdav-redirectref-protocol-09  . . . . .  29
   C.   Resolved issues (to be removed by RFC Editor before
        publication) . . . . . . . . . . . . . . . . . . . . . . . .  29
     C.1  lc-36-server . . . . . . . . . . . . . . . . . . . . . . .  29
     C.2  lc-33-forwarding . . . . . . . . . . . . . . . . . . . . .  29
     C.3  3-terminology-redirectref  . . . . . . . . . . . . . . . .  30
     C.4  lc-57-noautoupdate . . . . . . . . . . . . . . . . . . . .  30
     C.5  lc-48-s6 . . . . . . . . . . . . . . . . . . . . . . . . .  31
     C.6  lc-58-update . . . . . . . . . . . . . . . . . . . . . . .  31
     C.7  12.1-property-name . . . . . . . . . . . . . . . . . . . .  31
   D.   Open issues (to be removed by RFC Editor prior to
        publication) . . . . . . . . . . . . . . . . . . . . . . . .  32
     D.1  edit . . . . . . . . . . . . . . . . . . . . . . . . . . .  32
     D.2  old_clients  . . . . . . . . . . . . . . . . . . . . . . .  32
        Index  . . . . . . . . . . . . . . . . . . . . . . . . . . .  33
        Intellectual Property and Copyright Statements . . . . . . .  35





















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1.  Introduction


   This specification extends the Web Distributed Authoring Protocol
   (WebDAV) to enable clients to create new access paths to existing
   resources.  This capability is useful for several reasons:


   WebDAV makes it possible to organize HTTP 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:
   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 unrelated systems 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 redirect 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 a HTTP status
   code from the 3xx range (Redirection), 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
   redirect reference resources are implemented using HTTP 3xx
   responses, it generally takes two round trips to submit a request to
   the intended resource.  Redirect references work equally well for
   local resources and for resources that reside on a different system




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   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 defines the semantics of existing methods when applied to
   redirect reference resources.  Section 6 discusses how to create a
   redirect reference resource, and Section 7 discusses updating
   redirect references.  Section 8 discusses their semantics when
   applied to collections that contain redirect reference resources.
   Sections 9 through 11 discuss several other issues raised by the
   existence of redirect reference resources.  Sections 12 through 15
   define the new headers, properties, and XML elements required to
   support redirect reference resources.  Section 16 discusses
   capability discovery.  Sections 17 through 19 present the security,
   internationalization, and IANA concerns raised by this specification.
   The remaining sections provide a variety of supporting information.


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].


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 an
      HTTP status code from the 3xx range, to a defined target resource.


   Non-Reference Resource


      A resource that is not a reference to another resource.





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   Target Resource


      The resource to which requests are redirected by a redirect
      reference resource.  A target resource can be anything that can be
      identified by an absolute URI (see [RFC2396], "absoluteURI").


   This document uses the terms "precondition",  "postcondition" and
   "protected property" as defined in [RFC3253].  Servers MUST report
   pre-/postcondition failures as described in section 1.6 of this
   document.


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 12.1 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 13.2 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 14.1 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 12.2
   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.


   Implementation Note: Operations on the target of a redirect reference




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   usually do not affect the redirect reference itself.  However,
   clients should not rely on this behaviour (for instance, some servers
   may update redirect references as a result of namespace operations on
   the reference's target).


5.  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 3xx range (Redirection) status code,
   unless the request includes an Apply-To-Redirect-Ref header
   specifying "T".  The client and server MUST follow [RFC2616] Section
   10.3, 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 3xx 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).


6.  MKREDIRECTREF Method


   The MKREDIRECTREF method requests the creation of a redirect
   reference resource.


   If a MKREDIRECTREF request fails, the server state preceding the
   request MUST be restored.


   Responses from a MKREDIRECTREF request MUST NOT be cached, as
   MKREDIRECTREF has non-idempotent and non-safe semantics (see
   [RFC2616], section 9.1).




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   Marshalling:


      The request body MUST be a DAV:mkredirectref XML element.


      <!ELEMENT mkredirectref (reftarget, redirect-lifetime?)>
      <!ELEMENT reftarget (href)>
      <!ELEMENT redirect-lifetime (permanent | temporary)>
      <!ELEMENT permanent EMPTY>
      <!ELEMENT temporary EMPTY>


      The DAV:href element is defined in [RFC2518] (Section 12.3) and
      MUST contain either an absoluteURI or a relativeURI (see
      [RFC2396], Section 3 and 5).


      If no DAV:redirect-lifetime element is specified, the server MUST
      behave as if a value of DAV:temporary was specified.


      If the request succeeds, the server MUST return 201 (Created)
      status.


      If a response body for a successful request is included, it MUST
      be a DAV:mkredirectref-response XML element.  Note that this
      document does not define any elements for the MKREDIRECTREF
      response body, but the DAV:mkredirectref-response element is
      defined to ensure interoperability between future extensions that
      do define elements for the response body.


      <!ELEMENT mkredirectref-response ANY>


   Preconditions:


      (DAV:resource-must-be-null): A resource MUST NOT exist at the
      request-URL.


      (DAV:parent-resource-must-be-non-null): The request-URL minus the
      last past segment MUST identify a collection.


      (DAV:name-allowed): The last segment of the request URL is
      available for use as a resource name.


      (DAV:locked-update-allowed): If the collection identified by the
      Request-URL minus the last path segment is write-locked, then the
      appropriate token MUST be specified in an If request header.


      (DAV:redirect-lifetime-supported): If the request body contains a
      DAV:redirect-lifetime element, the server MUST support the
      specified lifetime.  Support for DAV:temporary is REQUIRED, while
      support for DAV:permanent is OPTIONAL.




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   Postconditions:


      (DAV:new-redirectref): a new redirect reference resource is
      created whose DAV:reftarget property has the value specified in
      the request body.



6.1  Example: Creating a Redirect Reference Resource with MKREDIRECTREF


   >> Request:


   MKREDIRECTREF /~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:mkredirectref xmlns:D="DAV:">
     <D:reftarget>
       <D:href>/i-d/draft-webdav-protocol-08.txt</D:href>
     </D:reftarget>
   </D:mkredirectref>


   >> 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
   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 and it's DAV:redirect-lifetime property has the value
   DAV:temporary.


7.  UPDATEREDIRECTREF Method


   The UPDATEREDIRECTREF method requests the update of a redirect
   reference resource.


   If a UPDATEREDIRECTREF request fails, the server state preceding the
   request MUST be restored.


   Responses from a UPDATEREDIRECTREF request MUST NOT be cached, as
   UPDATEREDIRECTREF has non-safe semantics (see [RFC2616], section
   9.1).





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   Marshalling:


      The request body MUST be a DAV:updateredirectref XML element.


      <!ELEMENT updateredirectref (reftarget?, redirect-lifetime?)>
      See Section 6 for a definition of DAV:reftarget and
      DAV:redirect-lifetime.


      If no DAV:reftarget element is specified, the server MUST NOT
      change the target of the redirect reference.


      If no DAV:redirect-lifetime element is specified, the server MUST
      NOT change the lifetime of the redirect reference.


      If a response body for a successful request is included, it MUST
      be a DAV:updateredirectref-response XML element.  Note that this
      document does not define any elements for the UPDATEREDIRECTREF
      response body, but the DAV:updateredirectref-response element is
      defined to ensure interoperability between future extensions that
      do define elements for the response body.


      <!ELEMENT updateredirectref-response ANY>


   Preconditions:


      (DAV:locked-update-allowed): if the resource is write-locked, then
      the appropriate token MUST be specified in an If request header.


      (DAV:must-be-redirectref): the resource identified by the
      request-URI must be a redirect reference resource as defined by
      this specification.


      (DAV:redirect-lifetime-supported): see Section 6.


      (DAV:redirect-lifetime-update-supported): servers MAY support
      changing the DAV:redirect-lifetime property; if they don't, this
      condition code can be used to signal failure.


   Postconditions:


      (DAV:redirectref-updated): the DAV:reftarget and
      DAV:redirect-lifetime properties of the redirect reference have
      been updated accordingly.









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7.1  Example: Updating a Redirect Reference Resource with
    UPDATEREDIRECTREF


   >> Request:


   UPDATEREDIRECTREF /~whitehead/dav/spec08.ref HTTP/1.1
   Host: www.example.com
   Apply-To-Redirect-Ref: T
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxx


   <?xml version="1.0" encoding="utf-8" ?>
   <D:updateredirectref xmlns:D="DAV:">
     <D:reftarget>
       <D:href>/i-d/draft-webdav-protocol-08b.txt</D:href>
     </D:reftarget>
   </D:updateredirectref>


   >> Response:


   HTTP/1.1 200 OK


   This request has updated the redirect reference's DAV:reftarget
   property to "/i-d/draft-webdav-protocol-08b.txt", and has not changed
   the DAV:redirect-lifetime value.  Note that the
   "Apply-To-Redirect-Ref" request header must be used, otherwise the
   request would result in a redirect (3xx) response status.


8.  Operations on Collections That Contain Redirect Reference Resources


   Consistent with the rules in Section 5, the response for each
   redirect reference encountered while processing a collection MUST be
   a 3xx (Redirection) 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 15 below.


   The Apply-To-Redirect-Ref header (defined in Section 12.2) 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.


8.1  LOCK on a Collection That Contains Redirect References


   An attempt to lock (with Depth: infinity) a collection that contains




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   redirect references without specifying "Apply-To-Redirect-Ref: T"
   will always fail.  The Multi-Status response will contain a 3xx
   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.


8.2  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


   >> 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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8.3  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:redirect-lifetime/>
     </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/>




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           <D:redirect-lifetime/>
         </D:prop>
         <D:status>HTTP/1.1 404 Not Found</D:status>
       </D:propstat>
     </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:redirect-lifetime/>
         </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:redirect-lifetime><D:temporary/></D:redirect-lifetime>
         </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.


8.4  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




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        (redirect reference resource) nunavut with target
                                   /Someplace/nunavut.map


   >> 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



8.5  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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9.  Operations on Targets of Redirect Reference Resources


   Operations on targets of redirect reference resources have no effect
   on the reference resource.


10.  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.


10.1  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.


11.  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




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   segment in a Request-URI identifies a redirect reference resource,
   the response SHOULD be a 3xx.  The value of the Location header in
   the  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 3xx responses
   before finally reaching the target resource.  The server responds to
   the initial request with a 3xx with Location: /a/y/z.html, and the
   client resubmits the request to /a/y/z.html.  The server responds to
   this request with a 3xx with Location: /b/z.html, and the client
   resubmits the request to /b/z.html.  The server responds to this
   request with a 3xx with Location: /c/d.html, and the client resubmits
   the request to /c/d.html.  This final request succeeds.





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      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.



12.  Headers


12.1  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 3xx responses from redirect
   reference resources.  The value is the (possibly relative) URI of the
   link target as specified during redirect reference resource creation.


12.2  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
   3xx 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.


13.  Redirect Reference Resource Properties


   The properties defined below are REQUIRED on redirect reference
   resources.


13.1  DAV:redirect-lifetime (protected)


   This property provides information about the lifetime of a redirect.
   It can either be DAV:permanent (HTTP status 301) or DAV:temporary
   (HTTP status 302).  Future protocols may define additional values.


   <!ELEMENT redirect-lifetime (permanent | temporary)>
   <!ELEMENT permanent EMPTY>
   <!ELEMENT temporary EMPTY>







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13.2  DAV:reftarget (protected)


   This property 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 MKREDIRECTREF
   request.  The value is a DAV:href element containing the URI of the
   target resource.


   <!ELEMENT reftarget href >



14.  XML Elements


14.1  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 >



15.  Extensions to the DAV:response XML Element for Multi-Status
    Responses


   As described in Section 8, 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) >



16.  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




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   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 MKREDIRECTREF 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.


16.1  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, MKREDIRECTREF
   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 MKREDIRECTREF requests can be submitted to
   /somecollection/someresource.


17.  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.


17.1  Privacy Concerns


   By creating redirect reference resources on a trusted server, it is
   possible for a hostile agent to induce users to send private




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   information to a target on an unrelated system.  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.)


17.2  Redirect Loops


   Although redirect loops were already possible in HTTP 1.1, the
   introduction of the MKREDIRECTREF 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 MKREDIRECTREF requests that would create loops.
   See also [RFC2616], Section 10.3 "Redirection 3xx."


17.3  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 MKREDIRECTREF 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.


17.4  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.


   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.


18.  Internationalization Considerations


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







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19.  IANA Considerations


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


20.  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.


21.  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,
   Lisa Dusseault, Stefan Eissing, 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.


22  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.


   [RFC3253]  Clemm, G., Amsden, J., Ellison, T., Kaler, C. and J.
              Whitehead, "Versioning Extensions to WebDAV (Web
              Distributed Authoring and Versioning)", RFC 3253, March
              2002.








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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



   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/


Appendix A.  Changes to the WebDAV Document Type Definition


   <!-- Property Elements from Section 13 -->


   <!ELEMENT reftarget href>
   <!ELEMENT location href>


   <!-- XML Elements from Section 14 -->


   <!ELEMENT redirectref EMPTY >


   <!-- Changes to the DAV:response Element from Section 15 -->


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





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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".


B.6  Since draft-ietf-webdav-redirectref-protocol-07


   Closed issue "lc-38-not-hierarchical".  Cleaned up DTD fragments in
   appendix.  Close (reject) issues "lc-55-iana" and "lc-41-no-webdav".




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   Add issue "5_mkresource" and start work on MKREDIRECTREF (issue
   closed, but more work on MKREDIRECTREF needs to be done for updates
   and status codes other than 302).  Start resolution of "lc-85-301",
   replacing "302" by more generic language.  Update issue
   "lc-57-noautoupdate".  Close issue "lc-37-integrity" (duplicate of
   "lc-57-autoupdate").  Started work on "lc-85-301".  Add L.  Dusseault
   and S.  Eissing to Acknowledgments section.


B.7  Since draft-ietf-webdav-redirectref-protocol-08


   Fix index entries for conditions.  Open and resolve issue
   "specify_safeness".  Rewrite editorial section and parts of intro.
   Add more clarifications for issue "lc-85-301" and close it.


B.8  Since draft-ietf-webdav-redirectref-protocol-09


   Resolve issues "lc-33-forwarding", "lc-36-server" and
   "lc-57-noautoupdate".  Close issues "lc-48-s6", "12.1-property-name",
   "3-terminology-redirectref" and "lc-58-update".  Rearrange section 5
   and 6.  Add some more terms to index (no change tracking).


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-36-server


   Type: change


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


   yarong@Exchange.Microsoft.com (2000-02-11): Servers: Replace "server"
   with "unrelated system" throughout.


   Resolution (2004-10-06): Originally proposed resolution: Try
   replacing "server" with "host" in some contexts, rephrasing in
   passive voice in others.  See also issue 40.  Actual resolution:
   replace or remove on a case-by-case basis; use "system" or "unrelated
   system" (host in RFC2616 terminology is something different).


C.2  lc-33-forwarding


   Type: change


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


   yarong@Exchange.Microsoft.com (2000-02-11): Forwarding: Replace
   "forward" with "redirect" throughout.


   Resolution (2004-10-07): Original 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.
   Actual Resolution: change the text so that it always says "redirect"
   when we mean "redirect" and "forward" when we mean "forward"; do not
   add new definitions, though.


C.3  3-terminology-redirectref


   Type: change


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


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


   Resolution (2004-10-08): Retracted (see
   http://lists.w3.org/Archives/Public/w3c-dist-auth/2004OctDec/0009.htm
   l).


C.4  lc-57-noautoupdate


   Type: change


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


   yarong@Exchange.Microsoft.com (2000-02-11): Add language to forbid
   servers from automatically updating redirect resources when their
   targets move.


   julian.reschke@greenbytes.de (2004-01-05): I don't think we can
   forbid that.  This spec consists of (a) clarifications of how a
   server that supports redirects should behave for specific WebDAV
   methods, and (b) extensions to explicitly create them (or to apply a
   method to the redirect itself).  As such, we shouldn't add any
   requirements that HTTP doesn't add.  What we could do is (1) note why
   auto-update may be a bad idea, and possibly (2) define that redirects
   created by MKREDIRECTREF should not behave that way (or alternatively
   define more specific resource types).





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   Resolution (2004-10-07): State that operations on the target of a
   redirect reference usually will not affect the redirect itself; but
   also that clients should not rely on that in general (see also
   http://lists.w3.org/Archives/Public/w3c-dist-auth/2004OctDec/0004.htm
   l).


C.5  lc-48-s6


   Type: change


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


   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 (2004-10-06): Original 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.  Actual
   resolution: the current wording seems to be in line with what Yaron
   proposed back in 2000.


C.6  lc-58-update


   Type: change


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


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


   Resolution (2004-10-19): Agreed.  See also issues 6, 43.  See new
   method UPDATEREDIRECTREF.


C.7  12.1-property-name


   Type: change


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




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   Resolution (2004-10-08): Retracted (see
   http://lists.w3.org/Archives/Public/w3c-dist-auth/2004OctDec/0010.htm
   l).


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


D.1  edit


   Type: edit


   julian.reschke@greenbytes.de (2004-10-03): Umbrella issue for
   editorial changes.


D.2  old_clients


   Type: change


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


   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.












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Index


A
   Apply-To-Redirect-Ref header  22


C
   Condition Names
      DAV:locked-update-allowed (pre)  9, 11
      DAV:must-be-redirectref (pre)  11
      DAV:name-allowed (pre)  9
      DAV:new-redirectref (post)  10
      DAV:parent-resource-must-be-non-null (pre)  9
      DAV:redirect-lifetime-supported (pre)  9, 11
      DAV:redirect-lifetime-update-supported (pre)  11
      DAV:redirectref-updated (post)  11
      DAV:resource-must-be-null (pre)  9


D
   DAV header
      compliance class 'redirectrefs'  23
   DAV:locked-update-allowed precondition  9, 11
   DAV:must-be-redirectref precondition  11
   DAV:name-allowed precondition  9
   DAV:new-redirectref postcondition  10
   DAV:parent-resource-must-be-non-null precondition  9
   DAV:redirect-lifetime property  22
   DAV:redirect-lifetime-supported precondition  9, 11
   DAV:redirect-lifetime-update-supported precondition  11
   DAV:redirectref resource type  23
   DAV:redirectref-updated postcondition  11
   DAV:reftarget property  23
   DAV:resource-must-be-null precondition  9


H
   Headers
      Apply-To-Redirect-Ref  22
      Redirect-Ref  22


M
   Methods
      MKREDIRECTREF  8
      UPDATEREDIRECTREF  10
   MKREDIRECTREF method  8


N
   Non-Reference Resource  6


P




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   Properties
      DAV:redirect-lifetime  22
      DAV:reftarget  23


R
   Redirect-Ref header  22
   Rediret Reference Resource  6
   Resource Types
      DAV:redirectref  23


T
   Target Resource  7


U
   UPDATEREDIRECTREF method  10





































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