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RFC 3253

 
 
 

Versioning Extensions to WebDAV (Web Distributed Authoring and Versioning)

Part 2 of 4, p. 20 to 51
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3  Version-Control Feature

   The version-control feature provides support for putting a resource
   under version control, creating an associated version-controlled
   resource and version history resource as described in Section 2.2.1.
   A server indicates that it supports the version-control feature by
   including the string "version-control" as a field in the DAV header
   in the response to an OPTIONS request.  The version-control feature
   MUST be supported if any other versioning feature is supported.

3.1 Additional Resource Properties

   The version-control feature introduces the following REQUIRED
   properties for any WebDAV resource.

3.1.1 DAV:comment

   This property is used to track a brief comment about a resource that
   is suitable for presentation to a user.  The DAV:comment of a version
   can be used to indicate why that version was created.

   <!ELEMENT comment (#PCDATA)>
   PCDATA value: string

3.1.2 DAV:creator-displayname

   This property contains a description of the creator of the resource
   that is suitable for presentation to a user.  The DAV:creator-
   displayname of a version can be used to indicate who created that
   version.

   <!ELEMENT creator-displayname (#PCDATA)>
   PCDATA value: string

3.1.3 DAV:supported-method-set (protected)

   This property identifies the methods that are supported by the
   resource.  A method is supported by a resource if there is some state
   of that resource for which an application of that method will

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   successfully satisfy all postconditions of that method, including any
   additional postconditions added by the features supported by that
   resource.

   <!ELEMENT supported-method-set (supported-method*)>
   <!ELEMENT supported-method ANY>
   <!ATTLIST supported-method name NMTOKEN #REQUIRED>
   name value: a method name

3.1.4 DAV:supported-live-property-set (protected)

   This property identifies the live properties that are supported by
   the resource.  A live property is supported by a resource if that
   property has the semantics defined for that property.  The value of
   this property MUST identify all live properties defined by this
   document that are supported by the resource, and SHOULD identify all
   live properties that are supported by the resource.

   <!ELEMENT supported-live-property-set (supported-live-property*)>
   <!ELEMENT supported-live-property name>
   <!ELEMENT prop ANY>
   ANY value: a property element type

3.1.5 DAV:supported-report-set (protected)

   This property identifies the reports that are supported by the
   resource.

   <!ELEMENT supported-report-set (supported-report*)>
   <!ELEMENT supported-report report>
   <!ELEMENT report ANY>
   ANY value: a report element type

3.2 Version-Controlled Resource Properties

   The version-control feature introduces the following REQUIRED
   properties for a version-controlled resource.

3.2.1 DAV:checked-in (protected)

   This property appears on a checked-in version-controlled resource,
   and identifies a version that has the same content and dead
   properties as the version-controlled resource.  This property is
   removed when the resource is checked out, and then added back
   (identifying a new version) when the resource is checked back in.

   <!ELEMENT checked-in (href)>

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3.2.2 DAV:auto-version

   If the DAV:auto-version value is DAV:checkout-checkin, when a
   modification request (such as PUT/PROPPATCH) is applied to a
   checked-in version-controlled resource, the request is automatically
   preceded by a checkout and followed by a checkin operation.

   If the DAV:auto-version value is DAV:checkout-unlocked-checkin, when
   a modification request is applied to a checked-in version-controlled
   resource, the request is automatically preceded by a checkout
   operation.  If the resource is not write-locked, the request is
   automatically followed by a checkin operation.

   If the DAV:auto-version value is DAV:checkout, when a modification
   request is applied to a checked-in version-controlled resource, the
   request is automatically preceded by a checkout operation.

   If the DAV:auto-version value is DAV:locked-checkout, when a
   modification request is applied to a write-locked checked-in
   version-controlled resource, the request is automatically preceded by
   a checkout operation.

   If an update to a write-locked checked-in resource is automatically
   preceded by a checkout of that resource, the checkout is associated
   with the write lock.  When this write lock is removed (e.g. from an
   UNLOCK or a lock timeout), if the resource has not yet been checked
   in, the removal of the write lock is automatically preceded by a
   checkin operation.

   A server MAY refuse to allow the value of the DAV:auto-version
   property to be modified, or MAY only support values from a subset of
   the valid values.

   <!ELEMENT auto-version (checkout-checkin | checkout-unlocked-checkin
     | checkout | locked-checkout)? >
   <!ELEMENT checkout-checkin EMPTY>
   <!ELEMENT checkout-unlocked-checkin EMPTY>
   <!ELEMENT checkout EMPTY>
   <!ELEMENT locked-checkout EMPTY>

3.3 Checked-Out Resource Properties

   The version-control feature introduces the following REQUIRED
   properties for a checked-out resource.

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3.3.1 DAV:checked-out (protected)

   This property identifies the version that was identified by the
   DAV:checked-in property at the time the resource was checked out.
   This property is removed when the resource is checked in.

   <!ELEMENT checked-out (href)>

3.3.2 DAV:predecessor-set

   This property determines the DAV:predecessor-set property of the
   version that results from checking in this resource.

   A server MAY reject attempts to modify the DAV:predecessor-set of a
   version-controlled resource.

   <!ELEMENT predecessor-set (href+)>

3.4 Version Properties

   The version-control feature introduces the following REQUIRED
   properties for a version.

3.4.1 DAV:predecessor-set (protected)

   This property identifies each predecessor of this version.  Except
   for the root version, which has no predecessors, each version has at
   least one predecessor.

   <!ELEMENT predecessor-set (href*)>

3.4.2 DAV:successor-set (computed)

   This property identifies each version whose DAV:predecessor-set
   identifies this version.

   <!ELEMENT successor-set (href*)>

3.4.3 DAV:checkout-set (computed)

   This property identifies each checked-out resource whose
   DAV:checked-out property identifies this version.

   <!ELEMENT checkout-set (href*)>

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3.4.4 DAV:version-name (protected)

   This property contains a server-defined string that is different for
   each version in a given version history.  This string is intended for
   display for a user, unlike the URL of a version, which is normally
   only used by a client and not displayed for a user.

   <!ELEMENT version-name (#PCDATA)>
   PCDATA value: string

3.5 VERSION-CONTROL Method

   A VERSION-CONTROL request can be used to create a version-controlled
   resource at the request-URL.  It can be applied to a versionable
   resource or to a version-controlled resource.

   If the request-URL identifies a versionable resource, a new version
   history resource is created, a new version is created whose content
   and dead properties are copied from the versionable resource, and the
   resource is given a DAV:checked-in property that is initialized to
   identify this new version.

   If the request-URL identifies a version-controlled resource, the
   resource just remains under version-control.  This allows a client to
   be unaware of whether or not a server automatically puts a resource
   under version control when it is created.

   If a VERSION-CONTROL request fails, the server state preceding the
   request MUST be restored.

   Marshalling:

      If a request body is included, it MUST be a DAV:version-control
      XML element.

      <!ELEMENT version-control ANY>

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

      <!ELEMENT version-control-response ANY>

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   Postconditions:

      (DAV:put-under-version-control): If the request-URL identified a
      versionable resource at the time of the request, the request MUST
      have created a new version history and MUST have created a new
      version resource in that version history.  The resource MUST have
      a DAV:checked-in property that identifies the new version.  The
      content, dead properties, and DAV:resourcetype of the new version
      MUST be the same as those of the resource.  Note that an
      implementation can choose to locate the version history and
      version resources anywhere that it wishes.  In particular, it
      could locate them on the same host and server as the version-
      controlled resource, on a different virtual host maintained by the
      same server, on the same host maintained by a different server, or
      on a different host maintained by a different server.

      (DAV:must-not-change-existing-checked-in-out): If the request-URL
      identified a resource already under version control at the time of
      the request, the request MUST NOT change the DAV:checked-in or
      DAV:checked-out property of that version-controlled resource.

3.5.1 Example - VERSION-CONTROL

   >>REQUEST

     VERSION-CONTROL /foo.html HTTP/1.1
     Host: www.webdav.org
     Content-Length: 0

   >>RESPONSE

     HTTP/1.1 200 OK

   In this example, /foo.html is put under version control.  A new
   version history is created for it, and a new version is created that
   has a copy of the content and dead properties of /foo.html.  The
   DAV:checked-in property of /foo.html identifies this new version.

3.6 REPORT Method

   A REPORT request is an extensible mechanism for obtaining information
   about a resource.  Unlike a resource property, which has a single
   value, the value of a report can depend on additional information
   specified in the REPORT request body and in the REPORT request
   headers.

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   Marshalling:

      The body of a REPORT request specifies which report is being
      requested, as well as any additional information that will be used
      to customize the report.

      The request MAY include a Depth header.  If no Depth header is
      included, Depth:0 is assumed.

      The response body for a successful request MUST contain the
      requested report.

      If a Depth request header is included, the response MUST be a 207
      Multi-Status.  The request MUST be applied separately to the
      collection itself and to all members of the collection that
      satisfy the Depth value.  The DAV:prop element of a DAV:response
      for a given resource MUST contain the requested report for that
      resource.

   Preconditions:

      (DAV:supported-report): The specified report MUST be supported by
      the resource identified by the request-URL.

   Postconditions:

      (DAV:no-modification): The REPORT method MUST NOT have changed the
      content or dead properties of any resource.

3.7 DAV:version-tree Report

   The DAV:version-tree report describes the requested properties of all
   the versions in the version history of a version.  If the report is
   requested for a version-controlled resource, it is redirected to its
   DAV:checked-in or DAV:checked-out version.

   The DAV:version-tree report MUST be supported by all version
   resources and all version-controlled resources.

   Marshalling:

      The request body MUST be a DAV:version-tree XML element.

      <!ELEMENT version-tree ANY>
      ANY value: a sequence of zero or more elements, with at most one
      DAV:prop element.
      prop: see RFC 2518, Section 12.11

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      The response body for a successful request MUST be a
      DAV:multistatus XML element.

      multistatus: see RFC 2518, Section 12.9

      The response body for a successful DAV:version-tree REPORT request
      MUST contain a DAV:response element for each version in the
      version history of the version identified by the request-URL.

3.7.1 Example - DAV:version-tree Report

   The version history drawn below would produce the following version
   tree report.

                        foo.html History

                             +---+
                             |   | V1
                             +---+
                            /     \
                           /       \
                       +---+       +---+
                       |   | V2    |   | V2.1.1
                       +---+       +---+

   >>REQUEST

     REPORT /foo.html HTTP/1.1
     Host: www.webdav.org
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:version-tree xmlns:D="DAV:">
       <D:prop>
         <D:version-name/>
         <D:creator-displayname/>
         <D:successor-set/>
       </D:prop>
     </D:version-tree>

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   >>RESPONSE

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://repo.webdav.org/his/23/ver/V1</D:href>
         <D:propstat>
           <D:prop>
             <D:version-name>V1</D:version-name>
             <D:creator-displayname>Fred</D:creator-displayname>
             <D:successor-set>
               <D:href>http://repo.webdav.org/his/23/ver/V2</D:href>
               <D:href>http://repo.webdav.org/his/23/ver/V2.1.1</D:href>
             </D:successor-set>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
       <D:response>
         <D:href>http://repo.webdav.org/his/23/ver/V2</D:href>
         <D:propstat>
           <D:prop>
             <D:version-name>V2</D:version-name>
             <D:creator-displayname>Fred</D:creator-displayname>
             <D:successor-set/>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
       <D:response>
         <D:href>http://repo.webdav.org/his/23/ver/V2.1.1</D:href>
         <D:propstat>
           <D:prop>
             <D:version-name>V2.1.1</D:version-name>
             <D:creator-displayname>Sally</D:creator-displayname>
             <D:successor-set/>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>

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3.8 DAV:expand-property Report

   Many property values are defined as a DAV:href, or a set of DAV:href
   elements.  The DAV:expand-property report provides a mechanism for
   retrieving in one request the properties from the resources
   identified by those DAV:href elements.  This report not only
   decreases the number of requests required, but also allows the server
   to minimize the number of separate read transactions required on the
   underlying versioning store.

   The DAV:expand-property report SHOULD be supported by all resources
   that support the REPORT method.

   Marshalling:

      The request body MUST be a DAV:expand-property XML element.

      <!ELEMENT expand-property (property*)>
      <!ELEMENT property (property*)>
      <!ATTLIST property name NMTOKEN #REQUIRED>
      name value: a property element type
      <!ATTLIST property namespace NMTOKEN "DAV:">
      namespace value: an XML namespace

      The response body for a successful request MUST be a
      DAV:multistatus XML element.

      multistatus: see RFC 2518, Section 12.9

      The properties reported in the DAV:prop elements of the
      DAV:multistatus element MUST be those identified by the
      DAV:property elements in the DAV:expand-property element.  If
      there are DAV:property elements nested within a DAV:property
      element, then every DAV:href in the value of the corresponding
      property is replaced by a DAV:response element whose DAV:prop
      elements report the values of the properties identified by the
      nested DAV:property elements.  The nested DAV:property elements
      can in turn contain DAV:property elements, so that multiple levels
      of DAV:href expansion can be requested.

      Note that a validating parser MUST be aware that the DAV:expand-
      property report effectively modifies the DTD of every property by
      replacing every occurrence of "href" in the DTD with "href |
      response".

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3.8.1 Example - DAV:expand-property

   This example describes how to query a version-controlled resource to
   determine the DAV:creator-display-name and DAV:activity-set of every
   version in the version history of that version-controlled resource.
   This example assumes that the server supports the version-history
   feature (see Section 5).

   >>REQUEST

     REPORT /foo.html HTTP/1.1
     Host: www.webdav.org
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:expand-property xmlns:D="DAV:">
       <D:property name="version-history">
         <D:property name="version-set">
           <D:property name="creator-displayname"/>
           <D:property name="activity-set"/>
         </D:property>
       </D:property>
     </D:expand-property>

   >>RESPONSE

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://www.webdav.org/foo.html</D:href>
         <D:propstat>
           <D:prop>
             <D:version-history>
               <D:response>
                 <D:href>http://repo.webdav.org/his/23</D:href>
                 <D:propstat>
                   <D:prop>
                     <D:version-set>
                       <D:response>
   <D:href>http://repo.webdav.org/his/23/ver/1</D:href>
                         <D:propstat>
                           <D:prop>
   <D:creator-displayname>Fred</D:creator-displayname>

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                             <D:activity-set> <D:href>
                               http://www.webdav.org/ws/dev/sally
                             </D:href> </D:activity-set> </D:prop>
                           <D:status>HTTP/1.1 200 OK</D:status>
                         </D:propstat> </D:response>
                       <D:response>
   <D:href>http://repo.webdav.org/his/23/ver/2</D:href>
                         <D:propstat>
                           <D:prop>
   <D:creator-displayname>Sally</D:creator-displayname>
                             <D:activity-set>
   <D:href>http://repo.webdav.org/act/add-refresh-cmd</D:href>
                             </D:activity-set> </D:prop>
                           <D:status>HTTP/1.1 200 OK</D:status>
                         </D:propstat> </D:response>
                     </D:version-set> </D:prop>
                   <D:status>HTTP/1.1 200 OK</D:status>
                 </D:propstat> </D:response>
             </D:version-history> </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat> </D:response>
     </D:multistatus>

   In this example, the DAV:creator-displayname and DAV:activity-set
   properties of the versions in the DAV:version-set of the
   DAV:version-history of http://www.webdav.org/foo.html are reported.

3.9 Additional OPTIONS Semantics

   If the server supports the version-control feature, it MUST include
   "version-control" as a field in the DAV response header from an
   OPTIONS request on any resource that supports any versioning
   properties, reports, or methods.

3.10 Additional PUT Semantics

   Additional Preconditions:

      (DAV:cannot-modify-version-controlled-content): If the request-URL
      identifies a resource with a DAV:checked-in property, the request
      MUST fail unless DAV:auto-version semantics will automatically
      check out the resource.

      (DAV:cannot-modify-version): If the request-URL identifies a
      version, the request MUST fail.

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      If the request creates a new resource that is automatically placed
      under version control, all preconditions for VERSION-CONTROL apply
      to the request.

   Additional Postconditions:

      (DAV:auto-checkout): If the resource was a checked-in version-
      controlled resource whose DAV:auto-version property indicates it
      should be automatically checked out but not automatically checked
      in for a modification request, then the server MUST have
      automatically checked out the resource prior to executing the
      request.  In particular, the value of the DAV:checked-out property
      of the resource MUST be that of the DAV:checked-in property prior
      to the request, the DAV:checked-in property MUST have been
      removed, and the DAV:predecessor-set property MUST be initialized
      to be the same as the DAV:checked-out property.  If any part of
      the checkout/update sequence failed, the status from the failed
      part of the request MUST be returned, and the server state
      preceding the request sequence MUST be restored.

      (DAV:auto-checkout-checkin): If the resource was a checked-in
      version-controlled resource whose DAV:auto-version property
      indicates it should be automatically checked out and automatically
      checked in for a modification request, then the server MUST have
      automatically checked out the resource prior to executing the
      request and automatically checked it in after the request.  In
      particular, the DAV:checked-in property of the resource MUST
      identify a new version whose content and dead properties are the
      same as those of the resource.  The DAV:predecessor-set of the new
      version MUST identify the version identified by the DAV:checked-in
      property prior to the request.  If any part of the
      checkout/update/checkin sequence failed, the status from the
      failed part of the request MUST be returned, and the server state
      preceding the request sequence MUST be restored.

      If the request creates a new resource, the new resource MAY have
      automatically been placed under version control, and all
      postconditions for VERSION-CONTROL apply to the request.

3.11 Additional PROPFIND Semantics

   A DAV:allprop PROPFIND request SHOULD NOT return any of the
   properties defined by this document.  This allows a versioning server
   to perform efficiently when a naive client, which does not understand
   the cost of asking a server to compute all possible live properties,
   issues a DAV:allprop PROPFIND request.

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   Additional Preconditions:

      (DAV:supported-live-property): If the request attempts to access a
      property defined by this document, the semantics of that property
      MUST be supported by the server.

3.12 Additional PROPPATCH Semantics

   Additional Preconditions:

      (DAV:cannot-modify-version-controlled-property): If the request
      attempts to modify a dead property, same semantics as PUT (see
      Section 3.10).

      (DAV:cannot-modify-version): If the request attempts to modify a
      dead property, same semantics as PUT (see Section 3.10).

      (DAV:cannot-modify-protected-property): An attempt to modify a
      property that is defined by this document, as being protected for
      that kind of resource, MUST fail.

      (DAV:supported-live-property): An attempt to modify a property
      defined by this document, but whose semantics are not enforced by
      the server, MUST fail.  This helps ensure that a client will be
      notified when it is trying to use a property whose semantics are
      not supported by the server.

   Additional Postconditions:

      (DAV:auto-checkout): If the request modified a dead property, same
      semantics as PUT (see Section 3.10).

      (DAV:auto-checkout-checkin): If the request modified a dead
      property, same semantics as PUT (see Section 3.10).

3.13 Additional DELETE Semantics

   Additional Preconditions:

      (DAV:no-version-delete): A server MAY fail an attempt to DELETE a
      version.

   Additional Postconditions:

      (DAV:update-predecessor-set): If a version was deleted, the server
      MUST have replaced any reference to that version in a
      DAV:predecessor-set by a copy of the DAV:predecessor-set of the
      deleted version.

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3.14 Additional COPY Semantics

   Additional Preconditions:

      If the request creates a new resource that is automatically placed
      under version control, all preconditions for VERSION-CONTROL apply
      to the request.

   Additional Postconditions:

      (DAV:must-not-copy-versioning-property): A property defined by
      this document MUST NOT have been copied to the new resource
      created by this request, but instead that property of the new
      resource MUST have the default initial value it would have had if
      the new resource had been created by a non-versioning method such
      as PUT or a MKCOL.

      (DAV:auto-checkout): If the destination is a version-controlled
      resource, same semantics as PUT (see Section 3.10).

      (DAV:auto-checkout-checkin): If the destination is a version-
      controlled resource, same semantics as PUT (see Section 3.10).

      (DAV:copy-creates-new-resource): If the source of a COPY is a
      version-controlled resource or version, and if there is no
      resource at the destination of the COPY, then the COPY creates a
      new non-version-controlled resource at the destination of the
      COPY.  The new resource MAY automatically be put under version
      control, but the resulting version-controlled resource MUST be
      associated with a new version history created for that new
      version-controlled resource, and all postconditions for
      VERSION-CONTROL apply to the request.

3.15 Additional MOVE Semantics

   Additional Preconditions:

      (DAV:cannot-rename-version): If the request-URL identifies a
      version, the request MUST fail.

   Additional Postconditions:

      (DAV:preserve-versioning-properties): When a resource is moved
      from a source URL to a destination URL, a property defined by this
      document MUST have the same value at the destination URL as it had
      at the source URL.

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3.16 Additional UNLOCK Semantics

   Note that these semantics apply both to an explicit UNLOCK request,
   as well as to the removal of a lock because of a lock timeout.  If a
   precondition or postcondition cannot be satisfied, the lock timeout
   MUST NOT occur.

   Additional Preconditions:

      (DAV:version-history-is-tree): If the request-URL identifies a
      checked-out version-controlled resource that will be automatically
      checked in when the lock is removed, then the versions identified
      by the DAV:predecessor-set of the checked-out resource MUST be
      descendants of the root version of the version history for the
      DAV:checked-out version.

   Additional Postconditions:

      (DAV:auto-checkin): If the request-URL identified a checked-out
      version-controlled resource that had been automatically checked
      out because of its DAV:auto-version property, the request MUST
      have created a new version in the version history of the
      DAV:checked-out version.  The request MUST have allocated a URL
      for the version that MUST NOT have previously identified any other
      resource, and MUST NOT ever identify a resource other than this
      version.  The content, dead properties, DAV:resourcetype, and
      DAV:predecessor-set of the new version MUST be copied from the
      checked-out resource.  The DAV:version-name of the new version
      MUST be set to a server-defined value distinct from all other
      DAV:version-name values of other versions in the same version
      history.  The request MUST have removed the DAV:checked-out
      property of the version-controlled resource, and MUST have added a
      DAV:checked-in property that identifies the new version.

4  CHECKOUT-IN-PLACE FEATURE

   With the version-control feature, WebDAV locking can be used to avoid
   the proliferation of versions that would result if every modification
   to a version-controlled resource produced a new version.  The
   checkout-in-place feature provides an alternative mechanism that
   allows a client to explicitly check out and check in a resource to
   create a new version.

4.1 Additional Version Properties

   The checkout-in-place feature introduces the following REQUIRED
   properties for a version.

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4.1.1 DAV:checkout-fork

   This property controls the behavior of CHECKOUT when a version
   already is checked out or has a successor.  If the DAV:checkout-fork
   of a version is DAV:forbidden, a CHECKOUT request MUST fail if it
   would result in that version appearing in the DAV:predecessor-set or
   DAV:checked-out property of more than one version or checked-out
   resource.  If DAV:checkout-fork is DAV:discouraged, such a CHECKOUT
   request MUST fail unless DAV:fork-ok is specified in the CHECKOUT
   request body.

   A server MAY reject attempts to modify the DAV:checkout-fork of a
   version.

   <!ELEMENT checkout-fork ANY>
   ANY value: A sequence of elements with at most one DAV:discouraged
   or DAV:forbidden element.
   <!ELEMENT discouraged EMPTY>
   <!ELEMENT forbidden EMPTY>

4.1.2 DAV:checkin-fork

   This property controls the behavior of CHECKIN when a version already
   has a successor.  If the DAV:checkin-fork of a version is
   DAV:forbidden, a CHECKIN request MUST fail if it would result in that
   version appearing in the DAV:predecessor-set of more than one
   version.  If DAV:checkin-fork is DAV:discouraged, such a CHECKIN
   request MUST fail unless DAV:fork-ok is specified in the CHECKIN
   request body.

   A server MAY reject attempts to modify the DAV:checkout-fork of a
   version.

   <!ELEMENT checkin-fork ANY>
   ANY value: A sequence of elements with at most one DAV:discouraged
   or DAV:forbidden element.
   <!ELEMENT discouraged EMPTY>
   <!ELEMENT forbidden EMPTY>

4.2 Checked-Out Resource Properties

   The checkout-in-place feature introduces the following REQUIRED
   properties for a checked-out resource.

4.2.1 DAV:checkout-fork

   This property determines the DAV:checkout-fork property of the
   version that results from checking in this resource.

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4.2.2 DAV:checkin-fork

   This property determines the DAV:checkin-fork property of the version
   that results from checking in this resource.

4.3 CHECKOUT Method (applied to a version-controlled resource)

   A CHECKOUT request can be applied to a checked-in version-controlled
   resource to allow modifications to the content and dead properties of
   that version-controlled resource.

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

   Marshalling:

      If a request body is included, it MUST be a DAV:checkout XML
      element.

      <!ELEMENT checkout ANY>

      ANY value: A sequence of elements with at most one DAV:fork-ok
      element.

      <!ELEMENT fork-ok EMPTY>

      If a response body for a successful request is included, it MUST
      be a DAV:checkout-response XML element.

      <!ELEMENT checkout-response ANY>

      The response MUST include a Cache-Control:no-cache header.

   Preconditions:

      (DAV:must-be-checked-in): If a version-controlled resource is
      being checked out, it MUST have a DAV:checked-in property.

      (DAV:checkout-of-version-with-descendant-is-forbidden): If the
      DAV:checkout-fork property of the version being checked out is
      DAV:forbidden, the request MUST fail if a version identifies that
      version in its DAV:predecessor-set.

      (DAV:checkout-of-version-with-descendant-is-discouraged): If the
      DAV:checkout-fork property of the version being checked out is
      DAV:discouraged, the request MUST fail if a version identifies
      that version in its DAV:predecessor-set unless DAV:fork-ok is
      specified in the request body.

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      (DAV:checkout-of-checked-out-version-is-forbidden): If the
      DAV:checkout-fork property of the version being checked out is
      DAV:forbidden, the request MUST fail if a checked-out resource
      identifies that version in its DAV:checked-out property.

      (DAV:checkout-of-checked-out-version-is-discouraged): If the
      DAV:checkout-fork property of the version being checked out is
      DAV:discouraged, the request MUST fail if a checked-out resource
      identifies that version in its DAV:checked-out property unless
      DAV:fork-ok is specified in the request body.

   Postconditions:

      (DAV:is-checked-out): The checked-out resource MUST have a
      DAV:checked-out property that identifies the DAV:checked-in
      version preceding the checkout.  The version-controlled resource
      MUST NOT have a DAV:checked-in property.

      (DAV:initialize-predecessor-set): The DAV:predecessor-set property
      of the checked-out resource MUST be initialized to be the
      DAV:checked-out version.

4.3.1 Example - CHECKOUT of a version-controlled resource

   >>REQUEST

     CHECKOUT /foo.html HTTP/1.1
     Host: www.webdav.org
     Content-Length: 0

   >>RESPONSE

     HTTP/1.1 200 OK
     Cache-Control: no-cache

   In this example, the version-controlled resource /foo.html is checked
   out.

4.4 CHECKIN Method (applied to a version-controlled resource)

   A CHECKIN request can be applied to a checked-out version-controlled
   resource to produce a new version whose content and dead properties
   are copied from the checked-out resource.

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

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   Marshalling:

      If a request body is included, it MUST be a DAV:checkin XML
      element.

      <!ELEMENT checkin ANY>
      ANY value: A sequence of elements with at most one
      DAV:keep-checked-out element and at most one DAV:fork-ok element.

      <!ELEMENT keep-checked-out EMPTY>
      <!ELEMENT fork-ok EMPTY>

      If a response body for a successful request is included, it MUST
      be a DAV:checkin-response XML element.

      <!ELEMENT checkin-response ANY>

      The response MUST include a Cache-Control:no-cache header.

   Preconditions:

      (DAV:must-be-checked-out): The request-URL MUST identify a
      resource with a DAV:checked-out property.

      (DAV:version-history-is-tree) The versions identified by the
      DAV:predecessor-set of the checked-out resource MUST be
      descendants of the root version of the version history for the
      DAV:checked-out version.

      (DAV:checkin-fork-forbidden): A CHECKIN request MUST fail if it
      would cause a version whose DAV:checkin-fork is DAV:forbidden to
      appear in the DAV:predecessor-set of more than one version.

      (DAV:checkin-fork-discouraged): A CHECKIN request MUST fail if it
      would cause a version whose DAV:checkin-fork is DAV:discouraged to
      appear in the DAV:predecessor-set of more than one version, unless
      DAV:fork-ok is specified in the request body.

   Postconditions:

      (DAV:create-version): The request MUST have created a new version
      in the version history of the DAV:checked-out version.  The
      request MUST have allocated a distinct new URL for the new

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      version, and that URL MUST NOT ever identify any resource other
      than that version. The URL for the new version MUST be returned in
      a Location response header.

      (DAV:initialize-version-content-and-properties): The content, dead
      properties, DAV:resourcetype, and DAV:predecessor-set of the new
      version MUST be copied from the checked-out resource.  The
      DAV:version-name of the new version MUST be set to a server-
      defined value distinct from all other DAV:version-name values of
      other versions in the same version history.

      (DAV:checked-in): If the request-URL identifies a version-
      controlled resource and DAV:keep-checked-out is not specified in
      the request body, the DAV:checked-out property of the version-
      controlled resource MUST have been removed and a DAV:checked-in
      property that identifies the new version MUST have been added.

      (DAV:keep-checked-out): If DAV:keep-checked-out is specified in
      the request body, the DAV:checked-out property of the checked-out
      resource MUST have been updated to identify the new version.

4.4.1 Example - CHECKIN

   >>REQUEST

     CHECKIN /foo.html HTTP/1.1
     Host: www.webdav.org
     Content-Length: 0

   >>RESPONSE

     HTTP/1.1 201 Created
     Location: http://repo.webdav.org/his/23/ver/32
     Cache-Control: no-cache

   In this example, version-controlled resource /foo.html is checked in,
   and a new version is created at http://repo.webdav.org/his/23/ver/32.

4.5 UNCHECKOUT Method

   An UNCHECKOUT request can be applied to a checked-out version-
   controlled resource to cancel the CHECKOUT and restore the pre-
   CHECKOUT state of the version-controlled resource.

   If an UNCHECKOUT request fails, the server MUST undo any partial
   effects of the UNCHECKOUT request.

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   Marshalling:

      If a request body is included, it MUST be a DAV:uncheckout XML
      element.

      <!ELEMENT uncheckout ANY>

      If a response body for a successful request is included, it MUST
      be a DAV:uncheckout-response XML element.

      <!ELEMENT uncheckout-response ANY>

      The response MUST include a Cache-Control:no-cache header.

   Preconditions:

      (DAV:must-be-checked-out-version-controlled-resource): The
      request-URL MUST identify a version-controlled resource with a
      DAV:checked-out property.

   Postconditions:

      (DAV:cancel-checked-out): The value of the DAV:checked-in property
      is that of the DAV:checked-out property prior to the request, and
      the DAV:checked-out property has been removed.

      (DAV:restore-content-and-dead-properties): The content and dead
      properties of the version-controlled resource are copies of its
      DAV:checked-in version.

4.5.1 Example - UNCHECKOUT

   >>REQUEST

     UNCHECKOUT /foo.html HTTP/1.1
     Host: www.webdav.org
     Content-Length: 0

   >>RESPONSE

     HTTP/1.1 200 OK
     Cache-Control: no-cache

   In this example, the content and dead properties of the version-
   controlled resource identified by http://www.webdav.org/foo.html are
   restored to their values preceding the most recent CHECKOUT of that
   version-controlled resource.

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4.6 Additional OPTIONS Semantics

   If a server supports the checkout-in-place feature, it MUST include
   "checkout-in-place" as a field in the DAV response header from an
   OPTIONS request on any resource that supports any versioning
   properties, reports, or methods.

5  Version-History Feature

   It is often useful to have access to a version history even after all
   version-controlled resources for that version history have been
   deleted.  A server can provide this functionality by supporting
   version history resources.  A version history resource is a resource
   that exists in a server defined namespace and therefore is unaffected
   by any deletion or movement of version-controlled resources.  A
   version history resource is an appropriate place to add a property
   that logically applies to all states of a resource.  The DAV:expand-
   property report (see Section 3.8) can be applied to the DAV:version-
   set of a version history resource to provide a variety of useful
   reports on all versions in that version history.

5.1 Version History Properties

   The DAV:resourcetype of a version history MUST be DAV:version-
   history.

   The version-history feature introduces the following REQUIRED
   properties for a version history.

5.1.1 DAV:version-set (protected)

   This property identifies each version of this version history.

   <!ELEMENT version-set (href+)>

5.1.2 DAV:root-version (computed)

   This property identifies the root version of this version history.

   <!ELEMENT root-version (href)>

5.2 Additional Version-Controlled Resource Properties

   The version-history feature introduces the following REQUIRED
   property for a version-controlled resource.

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5.2.1 DAV:version-history (computed)

   This property identifies the version history resource for the
   DAV:checked-in or DAV:checked-out version of this version-controlled
   resource.

   <!ELEMENT version-history (href)>

5.3 Additional Version Properties

   The version-history feature introduces the following REQUIRED
   property for a version.

5.3.1 DAV:version-history (computed)

   This property identifies the version history that contains this
   version.

   <!ELEMENT version-history (href)>

5.4 DAV:locate-by-history Report

   Many properties identify a version from some version history.  It is
   often useful to be able to efficiently locate a version-controlled
   resource for that version history.  The DAV:locate-by-history report
   can be applied to a collection to locate the collection member that
   is a version-controlled resource for a specified version history
   resource.

   Marshalling:

      The request body MUST be a DAV:locate-by-history XML element.

      <!ELEMENT locate-by-history (version-history-set, prop)>
      <!ELEMENT version-history-set (href+)>
      prop: see RFC 2518, Section 12.11

      The response body for a successful request MUST be a
      DAV:multistatus XML element containing every version-controlled
      resource that is a member of the collection identified by the
      request-URL, and whose DAV:version-history property identifies one
      of the version history resources identified by the request body.
      The DAV:prop element in the request body identifies which
      properties should be reported in the DAV:prop elements in the
      response body.

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   Preconditions:

      (DAV:must-be-version-history): Each member of the DAV:version-
      history-set element in the request body MUST identify a version
      history resource.

5.4.1 Example - DAV:locate-by-history Report

   >>REQUEST

     REPORT /ws/public HTTP/1.1
     Host: www.webdav.org
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:locate-by-history xmlns:D="DAV:">
       <D:version-history-set>
         <D:href>http://repo.webdav.org/his/23</D:href>
         <D:href>http://repo.webdav.org/his/84</D:href>
         <D:href>http://repo.webdav.org/his/129</D:href>
       <D:version-history-set/>
       <D:prop>
         </D:version-history>
       </D:prop>
     </D:locate-by-history>

   >>RESPONSE

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://www.webdav.org/ws/public/x/test.html</D:href>
         <D:propstat>
           <D:prop>
             <D:version-history>
               <D:href>http://repo.webdav.org/his/23</D:href>
             </D:version-history>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>

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   In this example, there is only one version-controlled member of
   /ws/public that is a version-controlled resource for one of the three
   specified version history resources.  In particular,
   /ws/public/x/test.html is the version-controlled resource for
   http://repo.webdav.org/his/23.

5.5 Additional OPTIONS Semantics

   If the server supports the version-history feature, it MUST include
   "version-history" as a field in the DAV response header from an
   OPTIONS request on any resource that supports any versioning
   properties, reports, or methods.

   A DAV:version-history-collection-set element MAY be included in the
   request body to identify collections that may contain version history
   resources.

   Additional Marshalling:

      If an XML request body is included, it MUST be a DAV:options XML
      element.

      <!ELEMENT options ANY>
      ANY value: A sequence of elements with at most one
      DAV:version-history-collection-set element.

      If an XML response body for a successful request is included, it
      MUST be a DAV:options-response XML element.

      <!ELEMENT options-response ANY>
      ANY value: A sequence of elements with at most one
      DAV:version-history-collection-set element.

      <!ELEMENT version-history-collection-set (href*)>

      If DAV:version-history-collection-set is included in the request
      body, the response body for a successful request MUST contain a
      DAV:version-history-collection-set element identifying collections
      that may contain version histories.  An identified collection MAY
      be the root collection of a tree of collections, all of which may
      contain version histories.  Since different servers can control
      different parts of the URL namespace, different resources on the
      same host MAY have different DAV:version-history-collection-set
      values.  The identified collections MAY be located on different
      hosts from the resource.

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5.6 Additional DELETE Semantics

   Additional Postconditions:

      (DAV:delete-version-set): If the request deleted a version
      history, the request MUST have deleted all versions in the
      DAV:version-set of that version history, and MUST have satisfied
      the postconditions for version deletion (see Section 3.13).

      (DAV:version-history-has-root): If the request deleted the root
      version of a version history, the request MUST have updated the
      DAV:root-version of the version history to refer to another
      version that is an ancestor of all other remaining versions in
      that version history.  A result of this postcondition is that
      every version history will have at least one version, and the only
      way to delete all versions is to delete the version history
      resource.

5.7 Additional COPY Semantics

   Additional Preconditions:

      (DAV:cannot-copy-history): If the request-URL identifies a version
      history, the request MUST fail.  In order to create another
      version history whose versions have the same content and dead
      properties, the appropriate sequence of VERSION-CONTROL, CHECKOUT,
      PUT, PROPPATCH, and CHECKIN requests must be made.

5.8 Additional MOVE Semantics

   Additional Preconditions:

      (DAV:cannot-rename-history): If the request-URL identifies a
      version history, the request MUST fail.

5.9 Additional VERSION-CONTROL Semantics

   Additional Postconditions:

      (DAV:new-version-history): If the request created a new version
      history, the request MUST have allocated a new server-defined URL
      for that version history that MUST NOT have previously identified
      any other resource, and MUST NOT ever identify a resource other
      than this version history.

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5.10 Additional CHECKIN Semantics

   Additional Postconditions:

      (DAV:add-to-history): A URL for the new version resource MUST have
      been added to the DAV:version-set of the version history of the
      DAV:checked-out version.

6  Workspace Feature

   In order to allow multiple users to work concurrently on adding
   versions to the same version history, it is necessary to allocate on
   the server multiple checked-out resources for the same version
   history.  Even if only one user is making changes to a resource, that
   user will sometimes wish to create a "private" version, and then to
   expose that version at a later time.  One way to provide this
   functionality depends on the client keeping track of its current set
   of checked-out resources.  This is the working-resource feature
   defined in Section 8.  The other way to provide this functionality
   avoids the need for persistent state on the client, and instead has
   the server maintain a human meaningful namespace for related sets of
   checked-out resources.  This is the workspace feature defined in this
   section.

   The workspace feature introduces a "workspace resource".  A workspace
   resource is a collection whose members are related version-controlled
   and non-version-controlled resources.  Multiple workspaces may be
   used to expose different versions and configurations of a set of
   version-controlled resources concurrently.  In order to make changes
   to a version-controlled resource in one workspace visible in another
   workspace, that version-controlled resource must be checked in, and
   then the corresponding version-controlled resource in the other
   workspace can be updated to display the content and dead properties
   of the new version.

   In order to ensure unambiguous merging (see Section 11) and
   baselining (see Section 12) semantics, a workspace may contain at
   most one version-controlled resource for a given version history.
   This is required for unambiguous merging because the MERGE method
   must identify which version-controlled resource is to be the merge
   target of a given version.  This is required for unambiguous
   baselining because a baseline can only select one version for a given
   version-controlled resource.

   Initially, an empty workspace can be created.  Non-version-controlled
   resources can then be added to the workspace with standard WebDAV
   requests such as PUT and MKCOL.  Version-controlled resources can be
   added to the workspace with VERSION-CONTROL requests.  If the

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   baseline feature is supported, collections in the workspace can be
   placed under baseline control, and then initialized by existing
   baselines.

6.1 Workspace Properties

   The workspace feature introduces the following REQUIRED property for
   a workspace.

6.1.1 DAV:workspace-checkout-set (computed)

   This property identifies each checked-out resource whose
   DAV:workspace property identifies this workspace.

   <!ELEMENT workspace-checkout-set (href*)>

6.2 Additional Resource Properties

   The workspace feature introduces the following REQUIRED property for
   a WebDAV resource.

6.2.1 DAV:workspace (protected)

   The DAV:workspace property of a workspace resource MUST identify
   itself.  The DAV:workspace property of any other type of resource
   MUST be the same as the DAV:workspace of its parent collection.

   <!ELEMENT workspace (href)>

6.3 MKWORKSPACE Method

   A MKWORKSPACE request creates a new workspace resource.  A server MAY
   restrict workspace creation to particular collections, but a client
   can determine the location of these collections from a
   DAV:workspace-collection-set OPTIONS request (see Section 6.4).

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

   Marshalling:

      If a request body is included, it MUST be a DAV:mkworkspace XML
      element.

      <!ELEMENT mkworkspace ANY>

      If a response body for a successful request is included, it MUST
      be a DAV:mkworkspace-response XML element.

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      <!ELEMENT mkworkspace-response ANY>

      The response MUST include a Cache-Control:no-cache header.

   Preconditions:

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

      (DAV:workspace-location-ok): The request-URL MUST identify a
      location where a workspace can be created.

   Postconditions:

      (DAV:initialize-workspace): A new workspace exists at the
      request-URL.  The DAV:resourcetype of the workspace MUST be
      DAV:collection.  The DAV:workspace of the workspace MUST identify
      the workspace.

6.3.1 Example - MKWORKSPACE

   >>REQUEST

     MKWORKSPACE /ws/public HTTP/1.1
     Host: www.webdav.org
     Content-Length: 0

   >>RESPONSE

     HTTP/1.1 201 Created
     Cache-Control: no-cache

   In this example, a new workspace is created at
   http://www.webdav.org/ws/public.

6.4 Additional OPTIONS Semantics

   If a server supports the workspace feature, it MUST include
   "workspace" as a field in the DAV response header from an OPTIONS
   request on any resource that supports any versioning properties,
   reports, or methods.

   If a server supports the workspace feature, it MUST also support the
   checkout-in-place feature and the version-history feature.

   A DAV:workspace-collection-set element MAY be included in the request
   body to identify collections that may contain workspace resources.

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   Additional Marshalling:

      If an XML request body is included, it MUST be a DAV:options XML
      element.

      <!ELEMENT options ANY>
      ANY value: A sequence of elements with at most one
      DAV:workspace-collection-set element.

      If an XML response body for a successful request is included, it
      MUST be a DAV:options-response XML element.

      <!ELEMENT options-response ANY>
      ANY value: A sequence of elements with at most one
      DAV:workspace-collection-set element.

      <!ELEMENT workspace-collection-set (href*)>

      If DAV:workspace-collection-set is included in the request body,
      the response body for a successful request MUST contain a
      DAV:workspace-collection-set element identifying collections that
      may contain workspaces.  An identified collection MAY be the root
      collection of a tree of collections, all of which may contain
      workspaces.  Since different servers can control different parts
      of the URL namespace, different resources on the same host MAY
      have different DAV:workspace-collection-set values.  The
      identified collections MAY be located on different hosts from the
      resource.

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6.4.1 Example - OPTIONS

   >>REQUEST

     OPTIONS /doc HTTP/1.1
     Host: www.webdav.org
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:options xmlns:D="DAV:">
       <D:version-history-collection-set/>
       <D:workspace-collection-set/>
     </D:options>

   >>RESPONSE

     HTTP/1.1 200 OK
     DAV: 1
     DAV: version-control,checkout-in-place,version-history,workspace
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:options-response xmlns:D="DAV:">
       <D:version-history-collection-set>
         <D:href>http://repo.webdav.org/his</D:href>
       </D:version-history-collection-set>
       <D:workspace-collection-set>
         <D:href>http://www.webdav.org/public/ws</D:href>
         <D:href>http://www.webdav.org/private/ws</D:href>
       </D:workspace-collection-set>
     </D:options-response>

   In this example, the server indicates that it provides Class 1 DAV
   support and basic-server-workspace versioning support.  In addition,
   the server indicates the requested locations of the version history
   resources and the workspace resources.

6.5 Additional DELETE Semantics

   Additional Postconditions:

      (DAV:delete-workspace-members): If a workspace is deleted, any
      resource that identifies that workspace in its DAV:workspace
      property MUST be deleted.


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