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rfc:rfc3253

Network Working Group G. Clemm Request for Comments: 3253 Rational Software Category: Standards Track J. Amsden

                                                            T. Ellison
                                                                   IBM
                                                              C. Kaler
                                                             Microsoft
                                                          J. Whitehead
                                                       U.C. Santa Cruz
                                                            March 2002
                  Versioning Extensions to WebDAV
             (Web Distributed Authoring and Versioning)

Status of this Memo

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

Copyright Notice

 Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

 This document specifies a set of methods, headers, and resource types
 that define the WebDAV (Web Distributed Authoring and Versioning)
 versioning extensions to the HTTP/1.1 protocol.  WebDAV versioning
 will minimize the complexity of clients that are capable of
 interoperating with a variety of versioning repository managers, to
 facilitate widespread deployment of applications capable of utilizing
 the WebDAV Versioning services.  WebDAV versioning includes automatic
 versioning for versioning-unaware clients, version history
 management, workspace management, baseline management, activity
 management, and URL namespace versioning.

Table of Contents

 1 Introduction....................................................  6
 1.1 Relationship to WebDAV........................................  7
 1.2 Notational Conventions........................................  8
 1.3 Terms.........................................................  8
 1.4 Property Values............................................... 11
  1.4.1 Initial Property Value..................................... 11

Clemm, et al. Standards Track [Page 1] RFC 3253 Versioning Extensions to WebDAV March 2002

  1.4.2 Protected Property Value................................... 12
  1.4.3 Computed Property Value.................................... 12
  1.4.4 Boolean Property Value..................................... 12
  1.4.5 DAV:href Property Value.................................... 12
 1.5 DAV Namespace XML Elements.................................... 12
 1.6 Method Preconditions and Postconditions....................... 12
  1.6.1 Example - CHECKOUT request................................. 13
 1.7 Clarification of COPY Semantics with Overwrite:T.............. 13
 1.8 Versioning Methods and Write Locks............................ 14
 2 Basic Versioning Features....................................... 14
 2.1 Basic Versioning Packages..................................... 14
 2.2 Basic Versioning Semantics.................................... 16
  2.2.1 Creating a Version-Controlled Resource..................... 16
  2.2.2 Modifying a Version-Controlled Resource.................... 17
  2.2.3 Reporting.................................................. 19
 3 Version-Control Feature......................................... 20
 3.1 Additional Resource Properties................................ 20
  3.1.1 DAV:comment................................................ 20
  3.1.2 DAV:creator-displayname.................................... 20
  3.1.3 DAV:supported-method-set (protected)....................... 20
  3.1.4 DAV:supported-live-property-set (protected)................ 21
  3.1.5 DAV:supported-report-set (protected)....................... 21
 3.2 Version-Controlled Resource Properties........................ 21
  3.2.1 DAV:checked-in (protected)................................. 21
  3.2.2 DAV:auto-version........................................... 22
 3.3 Checked-Out Resource Properties............................... 22
  3.3.1 DAV:checked-out (protected)................................ 23
  3.3.2 DAV:predecessor-set........................................ 23
 3.4 Version Properties............................................ 23
  3.4.1 DAV:predecessor-set (protected)............................ 23
  3.4.2 DAV:successor-set (computed)............................... 23
  3.4.3 DAV:checkout-set (computed)................................ 23
  3.4.4 DAV:version-name (protected)............................... 24
 3.5 VERSION-CONTROL Method........................................ 24
  3.5.1 Example - VERSION-CONTROL.................................. 25
 3.6 REPORT Method................................................. 25
 3.7 DAV:version-tree Report....................................... 26
  3.7.1 Example - DAV:version-tree Report.......................... 27
 3.8 DAV:expand-property Report.................................... 29
  3.8.1 Example - DAV:expand-property.............................. 30
 3.9 Additional OPTIONS Semantics.................................. 31
 3.10 Additional PUT Semantics..................................... 31
 3.11 Additional PROPFIND Semantics................................ 32
 3.12 Additional PROPPATCH Semantics............................... 33
 3.13 Additional DELETE Semantics.................................. 33
 3.14 Additional COPY Semantics.................................... 34
 3.15 Additional MOVE Semantics.................................... 34
 3.16 Additional UNLOCK Semantics.................................. 35

Clemm, et al. Standards Track [Page 2] RFC 3253 Versioning Extensions to WebDAV March 2002

 4 Checkout-In-Place Feature....................................... 35
 4.1 Additional Version Properties................................. 35
  4.1.1 DAV:checkout-fork.......................................... 36
  4.1.2 DAV:checkin-fork........................................... 36
 4.2 Checked-Out Resource Properties............................... 36
  4.2.1 DAV:checkout-fork.......................................... 36
  4.2.2 DAV:checkin-fork........................................... 37
 4.3 CHECKOUT Method............................................... 37
  4.3.1 Example - CHECKOUT......................................... 38
 4.4 CHECKIN Method................................................ 38
  4.4.1 Example - CHECKIN.......................................... 40
 4.5 UNCHECKOUT Method............................................. 40
  4.5.1 Example - UNCHECKOUT....................................... 41
 4.6 Additional OPTIONS Semantics.................................. 42
 5 Version-History Feature......................................... 42
 5.1 Version History Properties.................................... 42
  5.1.1 DAV:version-set (protected)................................ 42
  5.1.2 DAV:root-version (computed)................................ 42
 5.2 Additional Version-Controlled Resource Properties............. 42
  5.2.1 DAV:version-history (computed)............................. 43
 5.3 Additional Version Properties................................. 43
  5.3.1 DAV:version-history (computed)............................. 43
 5.4 DAV:locate-by-history Report.................................. 43
  5.4.1 Example - DAV:locate-by-history Report..................... 44
 5.5 Additional OPTIONS Semantics.................................. 45
 5.6 Additional DELETE Semantics................................... 46
 5.7 Additional COPY Semantics..................................... 46
 5.8 Additional MOVE Semantics..................................... 46
 5.9 Additional VERSION-CONTROL Semantics.......................... 46
 5.10 Additional CHECKIN Semantics................................. 47
 6 Workspace Feature............................................... 47
 6.1 Workspace Properties.......................................... 48
  6.1.1 DAV:workspace-checkout-set (computed)...................... 48
 6.2 Additional Resource Properties................................ 48
  6.2.1 DAV:workspace (protected).................................. 48
 6.3 MKWORKSPACE Method............................................ 48
  6.3.1 Example - MKWORKSPACE...................................... 49
 6.4 Additional OPTIONS Semantics.................................. 49
  6.4.1 Example - OPTIONS.......................................... 51
 6.5 Additional DELETE Semantics................................... 51
 6.6 Additional MOVE Semantics..................................... 52
 6.7 Additional VERSION-CONTROL Semantics.......................... 52
  6.7.1 Example - VERSION-CONTROL.................................. 53
 7 Update Feature.................................................. 53
 7.1 UPDATE Method................................................. 53
  7.1.1 Example - UPDATE........................................... 55
 7.2 Additional OPTIONS Semantics.................................. 55
 8 Label Feature................................................... 56

Clemm, et al. Standards Track [Page 3] RFC 3253 Versioning Extensions to WebDAV March 2002

 8.1 Additional Version Properties................................. 56
  8.1.1 DAV:label-name-set (protected)............................. 56
 8.2 LABEL Method.................................................. 56
  8.2.1 Example - Setting a label.................................. 58
 8.3 Label Header.................................................. 58
 8.4 Additional OPTIONS Semantics.................................. 59
 8.5 Additional GET Semantics...................................... 59
 8.6 Additional PROPFIND Semantics................................. 59
 8.7 Additional COPY Semantics..................................... 60
 8.8 Additional CHECKOUT Semantics................................. 60
 8.9 Additional UPDATE Semantics................................... 61
 9 Working-Resource Feature........................................ 62
 9.1 Additional Version Properties................................. 62
  9.1.1 DAV:checkout-fork.......................................... 62
  9.1.2 DAV:checkin-fork........................................... 63
 9.2 Working Resource Properties................................... 63
  9.2.1 DAV:auto-update (protected)................................ 63
  9.2.2 DAV:checkout-fork.......................................... 63
  9.2.3 DAV:checkin-fork........................................... 63
 9.3 CHECKOUT Method (applied to a version)........................ 63
  9.3.1 Example - CHECKOUT of a version............................ 65
 9.4 CHECKIN Method (applied to a working resource)................ 65
  9.4.1 Example - CHECKIN of a working resource.................... 66
 9.5 Additional OPTIONS Semantics.................................. 67
 9.6 Additional COPY Semantics..................................... 67
 9.7 Additional MOVE Semantics..................................... 67
 10  Advanced Versioning Features.................................. 67
 10.1 Advanced Versioning Packages................................. 68
 10.2 Advanced Versioning Terms.................................... 68
 11  MERGE Feature................................................. 70
 11.1 Additional Checked-Out Resource Properties................... 70
  11.1.1 DAV:merge-set............................................. 70
  11.1.2 DAV:auto-merge-set........................................ 71
 11.2 MERGE Method................................................. 71
  11.2.1 Example - MERGE........................................... 74
 11.3 DAV:merge-preview Report..................................... 75
  11.3.1 Example - DAV:merge-preview Report........................ 76
 11.4 Additional OPTIONS Semantics................................. 77
 11.5 Additional DELETE Semantics.................................. 77
 11.6 Additional CHECKIN Semantics................................. 77
 12  Baseline Feature.............................................. 77
 12.1 Version-Controlled Configuration Properties.................. 78
  12.1.1 DAV:baseline-controlled-collection (protected)............ 78
 12.2 Checked-Out Configuration Properties......................... 78
  12.2.1 DAV:subbaseline-set....................................... 78
 12.3 Baseline Properties.......................................... 78
  12.3.1 DAV:baseline-collection (protected)....................... 79
  12.3.2 DAV:subbaseline-set (protected)........................... 79

Clemm, et al. Standards Track [Page 4] RFC 3253 Versioning Extensions to WebDAV March 2002

 12.4 Additional Resource Properties............................... 79
  12.4.1 DAV:version-controlled-configuration (computed)........... 79
 12.5 Additional Workspace Properties.............................. 80
  12.5.1 DAV:baseline-controlled-collection-set (computed)......... 80
 12.6 BASELINE-CONTROL Method...................................... 80
  12.6.1 Example - BASELINE-CONTROL................................ 82
 12.7 DAV:compare-baseline Report.................................. 84
  12.7.1 Example - DAV:compare-baseline Report..................... 85
 12.8 Additional OPTIONS Semantics................................. 86
 12.9 Additional MKCOL Semantics................................... 86
 12.10 Additional COPY Semantics................................... 86
 12.11 Additional CHECKOUT Semantics............................... 86
 12.12 Additional CHECKIN Semantics................................ 86
 12.13 Additional UPDATE Semantics................................. 87
 12.14 Additional MERGE Semantics.................................. 89
 13  Activity Feature.............................................. 90
 13.1 Activity Properties.......................................... 91
  13.1.1 DAV:activity-version-set (computed)....................... 91
  13.1.2 DAV:activity-checkout-set (computed)...................... 92
  13.1.3 DAV:subactivity-set....................................... 92
  13.1.4 DAV:current-workspace-set (computed)...................... 92
 13.2 Additional Version Properties................................ 92
  13.2.1 DAV:activity-set.......................................... 93
 13.3 Additional Checked-Out Resource Properties................... 93
  13.3.1 DAV:unreserved............................................ 93
  13.3.2 DAV:activity-set.......................................... 93
 13.4 Additional Workspace Properties.............................. 93
  13.4.1 DAV:current-activity-set.................................. 94
 13.5 MKACTIVITY Method............................................ 94
  13.5.1 Example - MKACTIVITY...................................... 95
 13.6 DAV:latest-activity-version Report........................... 95
 13.7 Additional OPTIONS Semantics................................. 96
 13.8 Additional DELETE Semantics.................................. 96
 13.9 Additional MOVE Semantics.................................... 97
 13.10 Additional CHECKOUT Semantics............................... 97
  13.10.1 Example - CHECKOUT with an activity...................... 98
 13.11 Additional CHECKIN Semantics................................ 99
 13.12 Additional MERGE Semantics.................................. 99
 14  Version-Controlled-Collection Feature.........................100
 14.1 Version-Controlled Collection Properties.....................102
  14.1.1 DAV:eclipsed-set (computed)...............................102
 14.2 Collection Version Properties................................103
  14.2.1 DAV:version-controlled-binding-set (protected)............103
 14.3 Additional OPTIONS Semantics.................................103
 14.4 Additional DELETE Semantics..................................103
 14.5 Additional MKCOL Semantics...................................104
 14.6 Additional COPY Semantics....................................104
 14.7 Additional MOVE Semantics....................................104

Clemm, et al. Standards Track [Page 5] RFC 3253 Versioning Extensions to WebDAV March 2002

 14.8 Additional VERSION-CONTROL Semantics.........................104
 14.9 Additional CHECKOUT Semantics................................105
 14.10 Additional CHECKIN Semantics................................105
 14.11 Additional UPDATE and MERGE Semantics.......................106
 15  Internationalization Considerations...........................106
 16  Security Considerations.......................................107
 16.1 Auditing and Traceability....................................107
 16.2 Increased Need for Access Control............................108
 16.3 Security Through Obscurity...................................108
 16.4 Denial of Service............................................108
 17  IANA Considerations...........................................109
 18  Intellectual Property.........................................109
 19  Acknowledgements..............................................109
 20  References....................................................110
 Appendix A - Resource Classification..............................111
 A.1 DeltaV-Compliant Unmapped URL.................................111
 A.2 DeltaV-Compliant Resource.....................................111
 A.3 DeltaV-Compliant Collection...................................112
 A.4 Versionable Resource..........................................112
 A.5 Version-Controlled Resource...................................112
 A.6 Version.......................................................113
 A.7 Checked-In Version-Controlled Resource........................113
 A.8 Checked-Out Resource..........................................113
 A.9 Checked-Out Version-Controlled Resource.......................114
 A.10 Working Resource.............................................114
 A.11 Version History..............................................114
 A.12 Workspace....................................................115
 A.13 Activity.....................................................115
 A.14 Version-Controlled Collection................................115
 A.15 Collection Version...........................................115
 A.16 Version-Controlled Configuration.............................116
 A.17 Baseline.....................................................116
 A.18 Checked-Out Version-Controlled Configuration.................116
 Authors' Addresses................................................117
 Full Copyright Statement..........................................118

1 Introduction

 This document specifies a set of methods, headers, and properties
 that define the WebDAV (Web Distributed Authoring and Versioning)
 versioning extensions to the HTTP/1.1 protocol.  Versioning is
 concerned with tracking and accessing the history of important states
 of a web resource, such as a standalone web page.  The benefits of
 versioning in the context of the worldwide web include:

Clemm, et al. Standards Track [Page 6] RFC 3253 Versioning Extensions to WebDAV March 2002

  1. A resource has an explicit history and a persistent identity

across the various states it has had during the course of that

    history.  It allows browsing through past and alternative versions
    of a resource.  Frequently the modification and authorship history
    of a resource is critical information in itself.
  1. Resource states (versions) are given stable names that can support

externally stored links for annotation and link server support.

    Both annotation and link servers frequently need to store stable
    references to portions of resources that are not under their
    direct control.  By providing stable states of resources, version
    control systems allow not only stable pointers into those
    resources, but also well defined methods to determine the
    relationships of those states of a resource.
 WebDAV Versioning defines both basic and advanced versioning
 functionality.
 Basic versioning allows users to:
  1. Put a resource under version control
  2. Determine whether a resource is under version control
  3. Determine whether a resource update will automatically be captured

as a new version

  1. Create and access distinct versions of a resource
 Advanced versioning provides additional functionality for parallel
 development and configuration management of sets of web resources.
 This document will first define the properties and method semantics
 for the basic versioning features, and then define the additional
 properties and method semantics for the advanced versioning features.
 An implementer that is only interested in basic versioning should
 skip the advanced versioning sections (Section 10 to Section 14).

1.1 Relationship to WebDAV

 To maximize interoperability and the use of existing protocol
 functionality, versioning support is designed as extensions to the
 WebDAV protocol [RFC2518], which itself is an extension to the HTTP
 protocol [RFC2616].  All method marshalling and postconditions
 defined by RFC 2518 and RFC 2616 continue to hold, to ensure that
 versioning unaware clients can interoperate successfully with
 versioning servers.  Although the versioning extensions are designed
 to be orthogonal to most aspects of the WebDAV and HTTP protocols, a
 clarification to RFC 2518 is required for effective interoperable
 versioning.  This clarification is described in Section 1.7.

Clemm, et al. Standards Track [Page 7] RFC 3253 Versioning Extensions to WebDAV March 2002

1.2 Notational Conventions

 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 RFC 2119.
 The term "protected" is placed in parentheses following the
 definition of a protected property (see Section 1.4.2).
 The term "computed" is placed in parentheses following the definition
 of a computed property (see Section 1.4.3).
 When an XML element type in the "DAV:" namespace is referenced in
 this document outside of the context of an XML fragment, the string
 "DAV:" will be prefixed to the element type.
 When a method is defined in this document, a list of preconditions
 and postconditions will be defined for that method.  If the semantics
 of an existing method is being extended, a list of additional
 preconditions and postconditions will be defined.  A precondition or
 postcondition is prefixed by a parenthesized XML element type that
 identifies that precondition or postcondition (see Section 1.6).

1.3 Terms

 This document uses the terms defined in RFC 2616, in RFC 2518, and in
 this section.  Section 2.2 defines the semantic versioning model
 underlying this terminology.
 Version Control, Checked-In, Checked-Out
    "Version control" is a set of constraints on how a resource can be
    updated.  A resource under version control is either in a
    "checked-in" or "checked-out" state, and the version control
    constraints apply only while the resource is in the checked-in
    state.
 Versionable Resource
    A "versionable resource" is a resource that can be put under
    version control.
 Version-Controlled Resource
    When a versionable resource is put under version control, it
    becomes a "version-controlled resource".  A version-controlled
    resource can be "checked out" to allow modification of its content
    or dead properties by standard HTTP and WebDAV methods.

Clemm, et al. Standards Track [Page 8] RFC 3253 Versioning Extensions to WebDAV March 2002

 Checked-Out Resource
    A "checked-out resource" is a resource under version control that
    is in the checked-out state.
 Version Resource
    A "version resource", or simply "version", is a resource that
    contains a copy of a particular state (content and dead
    properties) of a version-controlled resource.  A version is
    created by "checking in" a checked-out resource.  The server
    allocates a distinct new URL for each new version, and this URL
    will never be used to identify any resource other than that
    version.  The content and dead properties of a version never
    change.
 Version History Resource
    A "version history resource", or simply "version history", is a
    resource that contains all the versions of a particular version-
    controlled resource.
 Version Name
    A "version name" is a string chosen by the server to distinguish
    one version of a version history from the other versions of that
    version history.  Versions from different version histories may
    have the same version name.
 Predecessor, Successor, Ancestor, Descendant
    When a version-controlled resource is checked out and then
    subsequently checked in, the version that was checked out becomes
    a "predecessor" of the version created by the checkin.  A client
    can specify multiple predecessors for a new version if the new
    version is logically a merge of those predecessors.  When a
    version is connected to another version by traversing one or more
    predecessor relations, it is called an "ancestor" of that version.
    The inverse of the predecessor and ancestor relations are the
    "successor" and "descendant" relations.  Therefore, if X is a
    predecessor of Y, then Y is a successor of X, and if X is an
    ancestor of Y, then Y is a descendant of X.
 Root Version Resource
    The "root version resource", or simply "root version", is the
    version in a version history that is an ancestor of every other
    version in that version history.

Clemm, et al. Standards Track [Page 9] RFC 3253 Versioning Extensions to WebDAV March 2002

 Workspace Resource
    A "workspace resource", or simply "workspace", is a collection
    that contains at most one version-controlled resource for a given
    version history (see Section 6).
 Working Resource
    A "working resource" is a checked-out resource created by the
    server at a server-defined URL when a version (instead of a
    version-controlled resource) is checked out.  Unlike a checked-out
    version-controlled resource, a working resource is deleted when it
    is checked in.
 Fork, Merge
    When a second successor is added to a version, this creates a
    "fork" in the version history.  When a version is created with
    multiple predecessors, this creates a "merge" in the version
    history.  A server may restrict the version history to be linear
    (with no forks or merges), but an interoperable versioning client
    should be prepared to deal with both forks and merges in the
    version history.

Clemm, et al. Standards Track [Page 10] RFC 3253 Versioning Extensions to WebDAV March 2002

 The following diagram illustrates several of the previous
 definitions.  Each box represents a version and each line between two
 boxes represents a predecessor/successor relationship.  For example,
 it shows V3 is a predecessor of V5, V7 is a successor of V5, V1 is an
 ancestor of V4, and V7 is a descendant of V4.  It also shows that
 there is a fork at version V2 and a merge at version V7.
                     History of foo.html
                             +---+
       Root Version -------> |   | V1
                             +---+           ^
                               |             |
                               |             |
                             +---+           |
       Version Name ----> V2 |   |           | Ancestor
                             +---+           |
                             /    \          |
                            /      \         |
                       +---+       +---+
                       |   | V3    |   | V4
                    ^  +---+       +---+
                    |    |           |       |
       Predecessor  |    |           |       |
                       +---+       +---+     |
                       |   | V5    |   | V6  | Descendant
                       +---+       +---+     |
       Successor    |       \      /         |
                    |        \    /          |
                    v        +---+           v
                             |   | V7
                             +---+
 Label
    A "label" is a name that can be used to select a version from a
    version history.  A label can be assigned by either a client or
    the server.  The same label can be used in different version
    histories.

1.4 Property Values

1.4.1 Initial Property Value

 Unless an initial value of a property of a given type is defined by
 this document, the initial value of a property of that type is
 implementation dependent.

Clemm, et al. Standards Track [Page 11] RFC 3253 Versioning Extensions to WebDAV March 2002

1.4.2 Protected Property Value

 When a property of a specific kind of resource is "protected", the
 property value cannot be updated on that kind of resource except by a
 method explicitly defined as updating that specific property.  In
 particular, a protected property cannot be updated with a PROPPATCH
 request.  Note that a given property can be protected on one kind of
 resource, but not protected on another kind of resource.

1.4.3 Computed Property Value

 When a property is "computed", its value is defined in terms of a
 computation based on the content and other properties of that
 resource, or even of some other resource.  When the semantics of a
 method is defined in this document, the effect of that method on
 non-computed properties will be specified; the effect of that method
 on computed properties will not be specified, but can be inferred
 from the computation defined for those properties.  A computed
 property is always a protected property.

1.4.4 Boolean Property Value

 Some properties take a Boolean value of either "false" or "true".

1.4.5 DAV:href Property Value

 The DAV:href XML element is defined in RFC 2518, Section 12.3.

1.5 DAV Namespace XML Elements in Request and Response Bodies

 Although WebDAV request and response bodies can be extended by
 arbitrary XML elements, which can be ignored by the message
 recipient, an XML element in the DAV namespace MUST NOT be used in
 the request or response body of a versioning method unless that XML
 element is explicitly defined in an IETF RFC.

1.6 Method Preconditions and Postconditions

 A "precondition" of a method describes the state of the server that
 must be true for that method to be performed.  A "postcondition" of a
 method describes the state of the server that must be true after that
 method has been completed.  If a method precondition or postcondition
 for a request is not satisfied, the response status of the request
 MUST be either 403 (Forbidden) if the request should not be repeated
 because it will always fail, or 409 (Conflict) if it is expected that
 the user might be able to resolve the conflict and resubmit the
 request.

Clemm, et al. Standards Track [Page 12] RFC 3253 Versioning Extensions to WebDAV March 2002

 In order to allow better client handling of 403 and 409 responses, a
 distinct XML element type is associated with each method precondition
 and postcondition of a request.  When a particular precondition is
 not satisfied or a particular postcondition cannot be achieved, the
 appropriate XML element MUST be returned as the child of a top-level
 DAV:error element in the response body, unless otherwise negotiated
 by the request.  In a 207 Multi-Status response, the DAV:error
 element would appear in the appropriate DAV:responsedescription
 element.

1.6.1 Example - CHECKOUT request with DAV:must-be-checked-in response

 >>REQUEST
   CHECKOUT /foo.html HTTP/1.1
   Host: www.webdav.org
 >>RESPONSE
   HTTP/1.1 409 Conflict
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxxx
   <?xml version="1.0" encoding="utf-8" ?>
   <D:error xmlns:D="DAV:">
     <D:must-be-checked-in/>
   </D:error>
 In this example, the request to CHECKOUT /foo.html fails because
 /foo.html is not checked in.

1.7 Clarification of COPY Semantics with Overwrite:T

 RFC 2518, Section 8.8.4 states:
 "If a resource exists at the destination and the Overwrite header is
 "T" then prior to performing the copy the server MUST perform a
 DELETE with "Depth: infinity" on the destination resource."
 The purpose of this sentence is to ensure that following a COPY, all
 destination resources have the same content and dead properties as
 the corresponding resources identified by the request-URL (where a
 resource with a given name relative to the Destination URL
 "corresponds" to a resource with the same name relative to the
 request-URL).  If at the time of the request, there already is a
 resource at the destination that has the same resource type as the
 corresponding resource at the request-URL, that resource MUST NOT be
 deleted, but MUST be updated to have the content and dead properties

Clemm, et al. Standards Track [Page 13] RFC 3253 Versioning Extensions to WebDAV March 2002

 of its corresponding member.  If a client wishes all resources at the
 destination to be deleted prior to the COPY, it MUST explicitly issue
 a DELETE request.
 The difference between updating a resource and replacing a resource
 with a new resource is especially important when resource history is
 being maintained (the former adds to an existing history, while the
 latter creates a new history).  In addition, locking and access
 control constraints might allow you to update a resource, but not
 allow you to delete it and create a new one in its place.
 Note that this clarification does not apply to a MOVE request.  A
 MOVE request with Overwrite:T MUST perform the DELETE with
 "Depth:infinity" on the destination resource prior to performing the
 MOVE.

1.8 Versioning Methods and Write Locks

 If a write-locked resource has a non-computed property defined by
 this document, the property value MUST NOT be changed by a request
 unless the appropriate lock token is included in the request.  Since
 every method introduced in this document other than REPORT modifies
 at least one property defined by this document, every versioning
 method other than REPORT is affected by a write lock.  In particular,
 the method MUST fail with a 423 (Locked) status if the resource is
 write-locked and the appropriate token is not specified in an If
 request header.

2 Basic Versioning Features

 Each basic versioning feature defines extensions to existing HTTP and
 WebDAV methods, as well as new resource types, live properties, and
 methods.

2.1 Basic Versioning Packages

 A server MAY support any combination of versioning features.
 However, in order to minimize the complexity of a WebDAV basic
 versioning client, a WebDAV basic versioning server SHOULD support
 one of the following three "packages" (feature sets):
  1. Core-Versioning Package: version-control
  2. Basic-Server-Workspace Package: version-control, workspace,

version-history, checkout

  1. Basic-Client-Workspace Package: version-control, working-

resource, update, label

Clemm, et al. Standards Track [Page 14] RFC 3253 Versioning Extensions to WebDAV March 2002

 The core-versioning package supports linear versioning by both
 versioning-aware and versioning-unaware clients.  A versioning-aware
 client can use reports and properties to access previous versions of
 a version-controlled resource.
 The basic workspace packages support parallel development of
 version-controlled resources.  Each client has its own configuration
 of the shared version-controlled resources, and can make changes to
 its configuration without disturbing that of another client.
 In the basic-server-workspace package, all persistent state is
 maintained on the server.  Each client has its own workspace resource
 allocated on the server, where each workspace identifies a
 configuration of the shared version-controlled resources.  Each
 client makes changes to its workspace, and can transfer changes when
 appropriate from one workspace to another.  The server workspace
 package is appropriate for clients with no local persistent state, or
 for clients that wish to expose their working configurations to other
 clients.
 In the basic-client-workspace package, each client maintains in local
 persistent storage the state for its configuration of the shared
 version-controlled resources.  When a client is ready to make its
 changes visible to other clients, it allocates a set of "working
 resources" on the server, updates the content and dead properties of
 these working resources, and then uses the set of working resources
 to update the version-controlled resources.  The working resources
 are used, instead of directly updating the version-controlled
 resources, so that sets of consistent updates can be prepared in
 parallel by multiple clients.  Also, a working resource allows a
 client to prepare a single update that requires multiple server
 requests (e.g. updating both the content and dead properties of a
 resource requires both a PUT and a PROPPATCH).  The client workspace
 package simplifies the server implementation by requiring each client
 to maintain its own namespace, but this requires that the clients
 have local persistent state, and does not allow clients to expose
 their working configurations to other clients.
 A server that supports both basic workspace packages will
 interoperate with all basic versioning clients.

Clemm, et al. Standards Track [Page 15] RFC 3253 Versioning Extensions to WebDAV March 2002

2.2 Basic Versioning Semantics

2.2.1 Creating a Version-Controlled Resource

 In order to track the history of the content and dead properties of a
 versionable resource, a user can put the resource under version
 control with a VERSION-CONTROL request.  A VERSION-CONTROL request
 performs three distinct operations:
 1) It creates a new "version history resource".  In basic versioning,
    a version history resource is not assigned a URL, and hence is not
    visible in the http scheme URL space.  However, when the version-
    history feature (see Section 5) is supported, this changes, and
    each version history resource is assigned a new distinct and
    unique server-defined URL.
 2) It creates a new "version resource" and adds it to the new version
    history resource.  The body and dead properties of the new version
    resource are a copy of those of the versionable resource.
    The server assigns the new version resource a new distinct and
    unique URL.
 3) It converts the versionable resource into a "version-controlled
    resource".  The version-controlled resource continues to be
    identified by the same URL that identified it as a versionable
    resource.  As part of this conversion, it adds a DAV:checked-in
    property, whose value contains the URL of the new version
    resource.
 Note that a versionable resource and a version-controlled resource
 are not new types of resources (i.e. they introduce no new
 DAV:resourcetype), but rather they are any type of resource that
 supports the methods and live properties defined for them in this
 document, in addition to all the methods and live properties implied
 by their DAV:resourcetype.  For example, a collection (whose
 DAV:resourcetype is DAV:collection) is a versionable resource if it
 supports the VERSION-CONTROL method, and is a version-controlled
 resource if it supports the version-controlled resource methods and
 live properties.
 In the following example, foo.html is a versionable resource that is
 put under version control.  After the VERSION-CONTROL request
 succeeds, there are two additional resources: a new version history
 resource and a new version resource in that version history.  The
 versionable resource is converted into a version-controlled resource,
 whose DAV:checked-in property identifies the new version resource.

Clemm, et al. Standards Track [Page 16] RFC 3253 Versioning Extensions to WebDAV March 2002

 The content and dead properties of a resource are represented by the
 symbol appearing inside the box for that resource (e.g., "S1" in the
 following example).
          ===VERSION-CONTROL==>
                    |                       +----+ version
                    |   version-            |    | history
       versionable  |   controlled          +----+ resource
       resource     |   resource              |
       /foo.html    |   /foo.html             |
                    |                         v
         +----+     |     +----+ checked-in +----+ version
         | S1 |     |     | S1 |----------->| S1 | resource
         +----+     |     +----+            +----+ /his/73/ver/1
 Thus, whereas before the VERSION-CONTROL request there was only one,
 non-version-controlled resource, after VERSION-CONTROL there are
 three separate, distinct resources, each containing its own state and
 properties: the version-controlled resource, the version resource,
 and the version history resource.  Since the version-controlled
 resource and the version resource are separate, distinct resources,
 when a method is applied to a version-controlled resource, it is only
 applied to that version-controlled resource, and is not applied to
 the version resource that is currently identified by the
 DAV:checked-in property of that version-controlled resource.
 Although the content and dead properties of a checked-in version-
 controlled resource are required to be the same as those of its
 current DAV:checked-in version, its live properties may differ.  An
 implementation may optimize storage by retrieving the content and
 dead properties of a checked-in version-controlled resource from its
 current DAV:checked-in version rather than storing them in the
 version-controlled resource, but this is just an implementation
 optimization.
 Normally, a resource is placed under version control with an explicit
 VERSION-CONTROL request.  A server MAY automatically place every new
 versionable resource under version control.  In this case, the
 resulting state on the server MUST be the same as if the client had
 explicitly applied a VERSION-CONTROL request to the versionable
 resource.

2.2.2 Modifying a Version-Controlled Resource

 In order to use methods like PUT and PROPPATCH to directly modify the
 content or dead properties of a version-controlled resource, the
 version-controlled resource must first be checked out.  When the
 checked-out resource is checked in, a new version is created in the

Clemm, et al. Standards Track [Page 17] RFC 3253 Versioning Extensions to WebDAV March 2002

 version history of that version-controlled resource.  The version
 that was checked out is remembered as the predecessor of the new
 version.
 The DAV:auto-version property (see Sections 3.2.2) of a checked-in
 version-controlled resource determines how it responds to a method
 that attempts to modify its content or dead properties.  Possible
 responses include:
  1. Fail the request. The resource requires an explicit CHECKOUT

request for it to be modified (see Sections 4 and 9.2.1).

  1. Automatically checkout the resource, perform the modification, and

automatically checkin the resource. This ensures that every state

    of the resource is tracked by the server, but can result in an
    excessive number of versions being created.
  1. Automatically checkout the resource, perform the modification, and

then if the resource is not write-locked, automatically checkin

    the resource.  If the resource is write-locked, it remains
    checked-out until the write-lock is removed (either explicitly
    through a subsequent UNLOCK request or implicitly through a time-
    out of the write-lock).  This helps a locking client avoid the
    proliferation of versions, while still allowing a non-locking
    client to update the resource.
  1. Automatically checkout the resource, perform the modification, and

then leave the resource checked out. If the resource is write-

    locked, it will be automatically checked in when the write-lock is
    removed, but an explicit CHECKIN operation (see Section 4.4) is
    required for a non-write-locked resource.  This minimizes the
    number of new versions that will be created by a versioning
    unaware client, but only a versioning aware client can create new
    versions of a non-write-locked resource.
  1. Fail the request unless the resource is write-locked. If it is

write-locked, automatically checkout the resource and perform the

    modification.  The resource is automatically checked in when the
    write-lock is removed.  This minimizes the number of new versions
    that will be created by a versioning unaware client, but never
    automatically checks out a resource that will not subsequently be
    automatically checked in.

Clemm, et al. Standards Track [Page 18] RFC 3253 Versioning Extensions to WebDAV March 2002

 The following diagram illustrates the effect of the checkout/checkin
 process on a version-controlled resource and its version history.
 The symbol inside a box (S1, S2, S3) represents the current content
 and dead properties of the resource represented by that box.  The
 symbol next to a box (V1, V2, V3) represents the URL for that
 resource.
            ===checkout==>     ===PUT==>     ===checkin==>
         /foo.html (version-controlled resource)
          +----+    |    +----+    |    +----+    |    +----+
          | S2 |    |    | S2 |    |    | S3 |    |    | S3 |
          +----+    |    +----+    |    +----+    |    +----+
       Checked-In=V2|Checked-Out=V2|Checked-Out=V2|Checked-In=V3
         /his/73 (version history for /foo.html)
         +----+     |   +----+     |   +----+     |   +----+
         | S1 | V1  |   | S1 | V1  |   | S1 | V1  |   | S1 | V1
         +----+     |   +----+     |   +----+     |   +----+
            |       |      |       |      |       |      |
            |       |      |       |      |       |      |
         +----+     |   +----+     |   +----+     |   +----+
         | S2 | V2  |   | S2 | V2  |   | S2 | V2  |   | S2 | V2
         +----+     |   +----+     |   +----+     |   +----+
                    |              |              |      |
                    |              |              |      |
                    |              |              |   +----+
                    |              |              |   | S3 | V3
                    |              |              |   +----+
 Note that a version captures only a defined subset of the state of a
 resource.  In particular, a version of a basic resource captures its
 content and dead properties, but not its live properties.

2.2.3 Reporting

 Some versioning information about a resource requires that parameters
 be specified along with that request for information.  Included in
 basic versioning is the required support for an extensible reporting
 mechanism, which includes a REPORT method as well as a live property
 for determining what reports are supported by a particular resource.
 The REPORT method is required by versioning, but it can be used in
 non-versioning WebDAV extensions.

Clemm, et al. Standards Track [Page 19] RFC 3253 Versioning Extensions to WebDAV March 2002

 To allow a client to query the properties of all versions in the
 version history of a specified version-controlled resource, basic
 versioning provides the DAV:version-tree report (see Section 3.7).  A
 more powerful version history reporting mechanism is provided by
 applying the DAV:expand-property report (see Section 3.8) to a
 version history resource (see Section 5).

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

Clemm, et al. Standards Track [Page 20] RFC 3253 Versioning Extensions to WebDAV March 2002

 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)>

Clemm, et al. Standards Track [Page 21] RFC 3253 Versioning Extensions to WebDAV March 2002

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.

Clemm, et al. Standards Track [Page 22] RFC 3253 Versioning Extensions to WebDAV March 2002

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*)>

Clemm, et al. Standards Track [Page 23] RFC 3253 Versioning Extensions to WebDAV March 2002

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>

Clemm, et al. Standards Track [Page 24] RFC 3253 Versioning Extensions to WebDAV March 2002

 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.

Clemm, et al. Standards Track [Page 25] RFC 3253 Versioning Extensions to WebDAV March 2002

 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

Clemm, et al. Standards Track [Page 26] RFC 3253 Versioning Extensions to WebDAV March 2002

    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>

Clemm, et al. Standards Track [Page 27] RFC 3253 Versioning Extensions to WebDAV March 2002

 >>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>

Clemm, et al. Standards Track [Page 28] RFC 3253 Versioning Extensions to WebDAV March 2002

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".

Clemm, et al. Standards Track [Page 29] RFC 3253 Versioning Extensions to WebDAV March 2002

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>

Clemm, et al. Standards Track [Page 30] RFC 3253 Versioning Extensions to WebDAV March 2002

                           <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.

Clemm, et al. Standards Track [Page 31] RFC 3253 Versioning Extensions to WebDAV March 2002

    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.

Clemm, et al. Standards Track [Page 32] RFC 3253 Versioning Extensions to WebDAV March 2002

 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.

Clemm, et al. Standards Track [Page 33] RFC 3253 Versioning Extensions to WebDAV March 2002

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.

Clemm, et al. Standards Track [Page 34] RFC 3253 Versioning Extensions to WebDAV March 2002

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.

Clemm, et al. Standards Track [Page 35] RFC 3253 Versioning Extensions to WebDAV March 2002

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.

Clemm, et al. Standards Track [Page 36] RFC 3253 Versioning Extensions to WebDAV March 2002

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.

Clemm, et al. Standards Track [Page 37] RFC 3253 Versioning Extensions to WebDAV March 2002

    (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.

Clemm, et al. Standards Track [Page 38] RFC 3253 Versioning Extensions to WebDAV March 2002

 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

Clemm, et al. Standards Track [Page 39] RFC 3253 Versioning Extensions to WebDAV March 2002

    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.

Clemm, et al. Standards Track [Page 40] RFC 3253 Versioning Extensions to WebDAV March 2002

 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.

Clemm, et al. Standards Track [Page 41] RFC 3253 Versioning Extensions to WebDAV March 2002

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.

Clemm, et al. Standards Track [Page 42] RFC 3253 Versioning Extensions to WebDAV March 2002

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.

Clemm, et al. Standards Track [Page 43] RFC 3253 Versioning Extensions to WebDAV March 2002

 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>

Clemm, et al. Standards Track [Page 44] RFC 3253 Versioning Extensions to WebDAV March 2002

 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.

Clemm, et al. Standards Track [Page 45] RFC 3253 Versioning Extensions to WebDAV March 2002

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.

Clemm, et al. Standards Track [Page 46] RFC 3253 Versioning Extensions to WebDAV March 2002

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

Clemm, et al. Standards Track [Page 47] RFC 3253 Versioning Extensions to WebDAV March 2002

 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.

Clemm, et al. Standards Track [Page 48] RFC 3253 Versioning Extensions to WebDAV March 2002

    <!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.

Clemm, et al. Standards Track [Page 49] RFC 3253 Versioning Extensions to WebDAV March 2002

 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.

Clemm, et al. Standards Track [Page 50] RFC 3253 Versioning Extensions to WebDAV March 2002

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.

Clemm, et al. Standards Track [Page 51] RFC 3253 Versioning Extensions to WebDAV March 2002

6.6 Additional MOVE Semantics

 Additional Postconditions:
    (DAV:workspace-member-moved): If the request-URL did not identify
    a workspace, the DAV:workspace of the destination MUST have been
    updated to have the same value as the DAV:workspace of the parent
    collection of the destination.
    (DAV:workspace-moved): If the request-URL identified a workspace,
    any reference to that workspace in a DAV:workspace property MUST
    have been updated to refer to the new location of that workspace.

6.7 Additional VERSION-CONTROL Semantics

 A VERSION-CONTROL request can be used to create a new version-
 controlled resource for an existing version history.  This allows the
 creation of version-controlled resources for the same version history
 in multiple workspaces.
 Additional Marshalling:
    <!ELEMENT version-control ANY>
    ANY value: A sequence of elements with at most one DAV:version
    element.
    <!ELEMENT version (href)>
 Additional Preconditions:
    (DAV:cannot-add-to-existing-history): If the DAV:version-control
    request body element contains a DAV:version element, the request-
    URL MUST NOT identify a resource.
    (DAV:must-be-version): The DAV:href of the DAV:version element
    MUST identify a version.
    (DAV:one-version-controlled-resource-per-history-per-workspace):
    If the DAV:version-control request body specifies a version, and
    if the request-URL is a member of a workspace, then there MUST NOT
    already be a version-controlled member of that workspace whose
    DAV:checked-in or DAV:checked-out property identifies any version
    from the version history of the version specified in the request
    body.

Clemm, et al. Standards Track [Page 52] RFC 3253 Versioning Extensions to WebDAV March 2002

 Additional Postconditions:
    (DAV:new-version-controlled-resource): If the request-URL did NOT
    identify a resource, a new version-controlled resource exists at
    the request-URL whose content and dead properties are initialized
    by those of the version in the request body, and whose
    DAV:checked-in property identifies that version.

6.7.1 Example - VERSION-CONTROL (using an existing version history)

 >>REQUEST
   VERSION-CONTROL /ws/public/bar.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-control xmlns:D="DAV:">
     <D:version>
       <D:href>http://repo.webdav.org/his/12/ver/V3</D:href>
     </D:version>
   </D:version-control>
 >>RESPONSE
   HTTP/1.1 201 Created
   Cache-Control: no-cache
 In this example, a new version-controlled resource is created at
 /ws/public/bar.html.  The content and dead properties of the new
 version-controlled resource are initialized to be the same as those
 of the version identified by http://repo.webdav.org/his/12/ver/V3.

7 UPDATE Feature

 The update feature provides a mechanism for changing the state of a
 checked-in version-controlled resource to be that of another version
 from the version history of that resource.

7.1 UPDATE Method

 The UPDATE method modifies the content and dead properties of a
 checked-in version-controlled resource (the "update target") to be
 those of a specified version (the "update source") from the version
 history of that version-controlled resource.

Clemm, et al. Standards Track [Page 53] RFC 3253 Versioning Extensions to WebDAV March 2002

 The response to an UPDATE request identifies the resources modified
 by the request, so that a client can efficiently update any cached
 state it is maintaining.  Extensions to the UPDATE method allow
 multiple resources to be modified from a single UPDATE request (see
 Section 12.13).
 Marshalling:
    The request body MUST be a DAV:update element.
    <!ELEMENT update ANY>
    ANY value: A sequence of elements with at most one DAV:version
    element and at most one DAV:prop element.
    <!ELEMENT version (href)>
    prop: see RFC 2518, Section 12.11
    The response for a successful request MUST be a 207 Multi-Status,
    where the DAV:multistatus XML element in the response body
    identifies all resources that have been modified by the request.
    multistatus: see RFC 2518, Section 12.9
    The response MUST include a Cache-Control:no-cache header.
 Postconditions:
    (DAV:update-content-and-properties): If the DAV:version element in
    the request body identified a version that is in the same version
    history as the DAV:checked-in version of a version-controlled
    resource identified by the request-URL, then the content and dead
    properties of that version-controlled resource MUST be the same as
    those of the version specified by the DAV:version element, and the
    DAV:checked-in property of the version-controlled resource MUST
    identify that version.  The request-URL MUST appear in a
    DAV:response element in the response body.
    (DAV:report-properties): If DAV:prop is specified in the request
    body, the properties specified in the DAV:prop element MUST be
    reported in the DAV:response elements in the response body.

Clemm, et al. Standards Track [Page 54] RFC 3253 Versioning Extensions to WebDAV March 2002

7.1.1 Example - UPDATE

 >>REQUEST
   UPDATE /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:update xmlns:D="DAV:">
     <D:version>
       <D:href>http://repo.webdav.org/his/23/ver/33</D:href>
     </D:version>
   </D:update>
 >>RESPONSE
   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxxx
   Cache-Control: no-cache
   <?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:status>HTTP/1.1 200 OK</D:status>
     </D:response>
 In this example, the content and dead properties of
 http://repo.webdav.org/his/23/ver/33 are copied to the version-
 controlled resource /foo.html, and the DAV:checked-in property of
 /foo.html is updated to refer to
 http://repo.webdav.org/his/23/ver/33.

7.2 Additional OPTIONS Semantics

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

Clemm, et al. Standards Track [Page 55] RFC 3253 Versioning Extensions to WebDAV March 2002

8 Label Feature

 A version "label" is a string that distinguishes one version in a
 version history from all other versions in that version history.  A
 label can automatically be assigned by a server, or it can be
 assigned by a client in order to provide a meaningful name for that
 version.  A given version label can be assigned to at most one
 version of a given version history, but client assigned labels can be
 reassigned to another version at any time.  Note that although a
 given label can be applied to at most one version from the same
 version history, the same label can be applied to versions from
 different version histories.
 For certain methods, if the request-URL identifies a version-
 controlled resource, a label can be specified in a Label request
 header (see Section 8.3) to cause the method to be applied to the
 version selected by that label from the version history of that
 version-controlled resource.

8.1 Additional Version Properties

 The label feature introduces the following REQUIRED property for a
 version.

8.1.1 DAV:label-name-set (protected)

 This property contains the labels that currently select this version.
 <!ELEMENT label-name-set (label-name*)>
 <!ELEMENT label-name (#PCDATA)>
 PCDATA value: string

8.2 LABEL Method

 A LABEL request can be applied to a version to modify the labels that
 select that version.  The case of a label name MUST be preserved when
 it is stored and retrieved.  When comparing two label names to decide
 if they match or not, a server SHOULD use a case-sensitive URL-
 escaped UTF-8 encoded comparison of the two label names.
 If a LABEL request is applied to a checked in version-controlled
 resource, the operation MUST be applied to the DAV:checked-in version
 of that version-controlled resource.

Clemm, et al. Standards Track [Page 56] RFC 3253 Versioning Extensions to WebDAV March 2002

 Marshalling:
    The request body MUST be a DAV:label element.
    <!ELEMENT label ANY>
    ANY value: A sequence of elements with at most one DAV:add,
    DAV:set, or DAV:remove element.
    <!ELEMENT add (label-name)>
    <!ELEMENT set (label-name)>
    <!ELEMENT remove (label-name)>
    <!ELEMENT label-name (#PCDATA)>
    PCDATA value: string
    The request MAY include a Label header.
    The request MAY include a Depth header.  If no Depth header is
    included, Depth:0 is assumed.  Standard depth semantics apply, and
    the request is applied to the collection identified by the
    request-URL and to all members of the collection that satisfy the
    Depth value.  If a Depth header is included and the request fails
    on any resource, the response MUST be a 207 Multi-Status that
    identifies all resources for which the request has failed.
    If a response body for a successful request is included, it MUST
    be a DAV:label-response XML element.
    <!ELEMENT label-response ANY>
    The response MUST include a Cache-Control:no-cache header.
 Preconditions:
    (DAV:must-be-checked-in): If the request-URL identifies a
    version-controlled resource, the version-controlled resource MUST
    be checked in.
    (DAV:must-select-version-in-history): If a Label request header is
    included and the request-URL identifies a version-controlled
    resource, the specified label MUST select a version in the version
    history of the version-controlled resource.
    (DAV:add-must-be-new-label): If DAV:add is specified in the
    request body, the specified label MUST NOT appear in the
    DAV:label-name-set of any version in the version history of that
    version-controlled resource.

Clemm, et al. Standards Track [Page 57] RFC 3253 Versioning Extensions to WebDAV March 2002

    (DAV:label-must-exist): If DAV:remove is specified in the request
    body, the specified label MUST appear in the DAV:label-name-set of
    that version.
 Postconditions:
    (DAV:add-or-set-label): If DAV:add or DAV:set is specified in the
    request body, the specified label MUST appear in the DAV:label-
    name-set of the specified version, and MUST NOT appear in the
    DAV:label-name-set of any other version in the version history of
    that version.
    (DAV:remove-label): If DAV:remove is specified in the request
    body, the specified label MUST NOT appear in the DAV:label-name-
    set of any version in the version history of that version.

8.2.1 Example - Setting a label

 >>REQUEST
   LABEL /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:label xmlns:D="DAV:">
     <D:set>
       <D:label-name>default</D:label-name>
     </D:set>
   </D:label>
 >>RESPONSE
   HTTP/1.1 200 OK
   Cache-Control: no-cache
 In this example, the label "default" is applied to the DAV:checked-in
 version of /foo.html.

8.3 Label Header

 For certain methods (e.g. GET, PROPFIND), if the request-URL
 identifies a version-controlled resource, a label can be specified in
 a Label request header to cause the method to be applied to the
 version selected by that label from the version history of that
 version-controlled resource.

Clemm, et al. Standards Track [Page 58] RFC 3253 Versioning Extensions to WebDAV March 2002

 The value of a label header is the name of a label, encoded using
 URL-escaped UTF-8.  For example, the label "release B.3" is
 identified by the following header:
   Label: release%20B.3
 A Label header MUST have no effect on a request whose request-URL
 does not identify a version-controlled resource.  In particular, it
 MUST have no effect on a request whose request-URL identifies a
 version or a version history.
 A server MUST return an HTTP-1.1 Vary header containing Label in a
 successful response to a cacheable request (e.g., GET) that includes
 a Label header.

8.4 Additional OPTIONS Semantics

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

8.5 Additional GET Semantics

 Additional Marshalling:
    The request MAY include a Label header.
 Additional Preconditions:
    (DAV:must-select-version-in-history): If a Label request header is
    included and the request-URL identifies a version-controlled
    resource, the specified label MUST select a version in the version
    history of the version-controlled resource.
 Additional Postconditions:
    (DAV:apply-request-to-labeled-version): If the request-URL
    identifies a version-controlled resource and a Label request
    header is included, the response MUST contain the content of the
    specified version rather than that of the version-controlled
    resource.

8.6 Additional PROPFIND Semantics

 Additional Marshalling:
    The request MAY include a Label header.

Clemm, et al. Standards Track [Page 59] RFC 3253 Versioning Extensions to WebDAV March 2002

 Additional Preconditions:
    (DAV:must-select-version-in-history): If a Label request header is
    included and the request-URL identifies a version-controlled
    resource, the specified label MUST select a version in the version
    history of the version-controlled resource.
 Additional Postconditions:
    (DAV:apply-request-to-labeled-version): If the request-URL
    identifies a version-controlled resource and a Label request
    header is included, the response MUST contain the properties of
    the specified version rather than that of the version-controlled
    resource.

8.7 Additional COPY Semantics

 Additional Marshalling:
    The request MAY include a Label header.
 Additional Preconditions:
    (DAV:must-select-version-in-history): If a Label request header is
    included and the request-URL identifies a version-controlled
    resource, the specified label MUST select a version in the version
    history of the version-controlled resource.
 Additional Postconditions:
    (DAV:apply-request-to-labeled-version): If the request-URL
    identifies a version-controlled resource and a Label request
    header is included, the request MUST have copied the properties
    and content of the specified version rather than that of the
    version-controlled resource.

8.8 Additional CHECKOUT Semantics

 If the server supports the working-resource option, a LABEL header
 may be included to check out the version selected by the specified
 label.
 Additional Marshalling:
    The request MAY include a Label header.

Clemm, et al. Standards Track [Page 60] RFC 3253 Versioning Extensions to WebDAV March 2002

 Additional Preconditions:
    (DAV:must-select-version-in-history): If a Label request header is
    included and the request-URL identifies a version-controlled
    resource, the specified label MUST select a version in the version
    history of the version-controlled resource.
    (DAV:must-not-have-label-and-apply-to-version): If a Label request
    header is included, the request body MUST NOT contain a
    DAV:apply-to-version element.
 Additional Postconditions:
    (DAV:apply-request-to-labeled-version): If the request-URL
    identifies a checked-in version-controlled resource, and a Label
    request header is included, the CHECKOUT MUST have been applied to
    the version selected by the specified label, and not to the
    version-controlled resource itself.

8.9 Additional UPDATE Semantics

 If the request body of an UPDATE request contains a DAV:label-name
 element, the update target is the resource identified by the
 request-URL, and the update source is the version selected by the
 specified label from the version history of the update target.
 Additional Marshalling:
    <!ELEMENT update ANY>
    ANY value: A sequence of elements with at most one DAV:label-name
    or DAV:version element (but not both).
    <!ELEMENT label-name (#PCDATA)>
    PCDATA value: string
    The request MAY include a Depth header.  If no Depth header is
    included, Depth:0 is assumed.  Standard depth semantics apply, and
    the request is applied to the collection identified by the
    request-URL and to all members of the collection that satisfy the
    Depth value.  If a Depth header is included and the request fails
    on any resource, the response MUST be a 207 Multi-Status that
    identifies all resources for which the request has failed.
 Additional Preconditions:
    (DAV:must-select-version-in-history): If the request includes a
    DAV:label-name element in the request body, the label MUST select
    a version in the version history of the version-controlled
    resource identified by the request-URL.

Clemm, et al. Standards Track [Page 61] RFC 3253 Versioning Extensions to WebDAV March 2002

    (DAV:depth-update): If the request includes a Depth header,
    standard depth semantics apply, and the request is applied to the
    collection identified by the request-URL and to all members of the
    collection that satisfy the Depth value.  The request MUST be
    applied to a collection before being applied to any members of
    that collection, since an update of a version-controlled
    collection might change the membership of that collection.
 Additional Postconditions:
    (DAV:apply-request-to-labeled-version): If a DAV:label-name
    element appears in the request body, the content and dead
    properties of the version-controlled resource must have been
    updated to be those of the version selected by that label.

9 Working-Resource Feature

 The working-resource feature provides an alternative to the workspace
 feature for supporting parallel development.  Unlike the workspace
 feature, where the desired configuration of versions and checked-out
 resources is maintained on the server, the working-resource feature
 maintains the configuration on the client.  This simplifies the
 server implementation, but does not allow a user to access the
 configuration from clients in different physical locations, such as
 from another office, from home, or while traveling.  Another
 difference is that the workspace feature isolates clients from a
 logical change that involves renaming shared resources, until that
 logical change is complete and tested; with the working resource
 feature, all clients use a common set of shared version-controlled
 resources and every client sees the result of a MOVE as soon as it
 occurs.
 If a server supports the working-resource feature but not the
 checkout-in-place feature, a CHECKOUT request can only be used to
 create a working resource, and cannot be used to check out a
 version-controlled resource.  If a server supports the checkout-in-
 place feature, but not the working-resource feature, a CHECKOUT can
 only be used to change the state of a version-controlled resource
 from checked-in to checked-out.

9.1 Additional Version Properties

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

9.1.1 DAV:checkout-fork

 This property is defined in Section 4.1.1.

Clemm, et al. Standards Track [Page 62] RFC 3253 Versioning Extensions to WebDAV March 2002

9.1.2 DAV:checkin-fork

 This property is defined in Section 4.1.2.

9.2 Working Resource Properties

 The working-resource feature introduces the following REQUIRED
 properties for a working resource.  Since a working resource is a
 checked-out resource, it also has any property defined in this
 document for a checked-out resource.

9.2.1 DAV:auto-update (protected)

 This property identifies the version-controlled resource that will be
 updated when the working resource is checked in.
 <!ELEMENT auto-update (href)>

9.2.2 DAV:checkout-fork

 This property is defined in Section 4.2.1.

9.2.3 DAV:checkin-fork

 This property is defined in Section 4.2.2.

9.3 CHECKOUT Method (applied to a version)

 A CHECKOUT request can be applied to a version to create a new
 working resource.  The content and dead properties of the working
 resource are a copy of the version that was checked out.
 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:apply-to-
    version and at most one DAV:fork-ok element.
    <!ELEMENT apply-to-version EMPTY>
    <!ELEMENT fork-ok EMPTY>
    If a response body for a successful request is included,
    it MUST be a DAV:checkout-response XML element.

Clemm, et al. Standards Track [Page 63] RFC 3253 Versioning Extensions to WebDAV March 2002

    <!ELEMENT checkout-response ANY>
    The response MUST include a Location header.
    The response MUST include a Cache-Control:no-cache header.
 Preconditions:
    (DAV:checkout-of-version-with-descendant-is-forbidden): See
    Section 4.3.
    (DAV:checkout-of-version-with-descendant-is-discouraged): See
    Section 4.3.
    (DAV:checkout-of-checked-out-version-is-forbidden): See Section
    4.3.
    (DAV:checkout-of-checked-out-version-is-discouraged): See Section
    4.3.
 Postconditions:
    (DAV:create-working-resource): If the request-URL identified a
    version, the Location response header MUST contain the URL of a
    new working resource.  The DAV:checked-out property of the new
    working resource MUST identify the version that was checked out.
    The content and dead properties of the working resource MUST be
    copies of the content and dead properties of the DAV:checked-out
    version.  The DAV:predecessor-set property of the working resource
    MUST be initialized to be the version identified by the request-
    URL.  The DAV:auto-update property of the working resource MUST
    NOT exist.
    (DAV:create-working-resource-from-checked-in-version): If the
    request-URL identified a version-controlled resource, and
    DAV:apply-to-version is specified in the request body, the
    CHECKOUT is applied to the DAV:checked-in version of the version-
    controlled resource, and not the version-controlled resource
    itself.  A new working resource is created and the version-
    controlled resource remains checked-in.  The DAV:auto-update
    property of the working resource MUST identify the version-
    controlled resource.

Clemm, et al. Standards Track [Page 64] RFC 3253 Versioning Extensions to WebDAV March 2002

9.3.1 Example - CHECKOUT of a version

 >>REQUEST
   CHECKOUT /his/12/ver/V3 HTTP/1.1
   Host: repo.webdav.org
   Content-Length: 0
 >>RESPONSE
   HTTP/1.1 201 Created
   Location: http://repo.webdav.org/wr/157
   Cache-Control: no-cache
 In this example, the version identified by
 http://repo.webdav.org/his/12/ver/V3 is checked out, and the new
 working resource is located at http://repo.webdav.org/wr/157.

9.4 CHECKIN Method (applied to a working resource)

 A CHECKIN request can be applied to a working resource to produce a
 new version whose content and dead properties are a copy of those of
 the working resource.  If the DAV:auto-update property of the working
 resource was set because the working resource was created by applying
 a CHECKOUT with the DAV:apply-to-version flag to a version-controlled
 resource, the CHECKIN request will also update the content and dead
 properties of that version-controlled resource to be those of the new
 version.
 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:fork-ok
    element.
    <!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.

Clemm, et al. Standards Track [Page 65] RFC 3253 Versioning Extensions to WebDAV March 2002

 Preconditions:
    (DAV:must-be-checked-out): See Section 4.4.
    (DAV:version-history-is-tree) See Section 4.4.
    (DAV:checkin-fork-forbidden): See Section 4.4.
    (DAV:checkin-fork-discouraged): See Section 4.4.
    (DAV:no-overwrite-by-auto-update): If the DAV:auto-update property
    for the checked-out resource identifies a version-controlled
    resource, at least one of the versions identified by the
    DAV:predecessor-set property of the checked-out resource MUST
    identify a version that is either the same as or a descendant of
    the version identified by the DAV:checked-in property of that
    version-controlled resource.
 Postconditions:
    (DAV:create-version): See Section 4.4.
    (DAV:initialize-version-content-and-properties): See Section 4.4.
    (DAV:auto-update): If the DAV:auto-update property of the
    checked-out resource identified a version-controlled resource, an
    UPDATE request with the new version MUST have been applied to that
    version-controlled resource.
    (DAV:delete-working-resource): If the request-URL identifies a
    working resource and if DAV:keep-checked-out is not specified in
    the request body, the working resource is deleted.

9.4.1 Example - CHECKIN of a working resource

 >>REQUEST
   CHECKIN /wr/157 HTTP/1.1
   Host: repo.webdav.org
   Content-Length: 0
 >>RESPONSE
   HTTP/1.1 201 Created
   Location: http://repo.webdav.org/his/23/ver/15
   Cache-Control: no-cache

Clemm, et al. Standards Track [Page 66] RFC 3253 Versioning Extensions to WebDAV March 2002

 In this example, the working resource /wr/157 checked in, and a new
 version is created at http://repo.webdav.org/his/23/ver/15.

9.5 Additional OPTIONS Semantics

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

9.6 Additional COPY Semantics

 Additional Postconditions:
    (DAV:copy-creates-new-resource): The result of copying a working
    resource is 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.

9.7 Additional MOVE Semantics

 Additional Preconditions:
    (DAV:cannot-rename-working-resource): If the request-URL
    identifies a working resource, the request MUST fail.
 Additional Postconditions:
    (DAV:update-auto-update): If the request-URL identified a
    version-controlled resource, any DAV:auto-update properties that
    identified that version-controlled resource MUST have been updated
    to contain the new location of that version-controlled resource.

10 Advanced Versioning Features

 Advanced versioning addresses the problems of parallel development
 and configuration management of multiple sets of interrelated
 resources.  Traditionally, artifacts of software development,
 including requirements, design documents, code, and test cases, have
 been a focus of configuration management.  Web sites, comprising
 multiple inter-linked resources (HTML, graphics, sound, CGI, and
 others), are another class of complex information artifacts that
 benefit from the application of configuration management.  The
 advanced versioning capabilities for coordinating concurrent change
 provide the infrastructure for efficient and controlled management of
 large evolving web sites.

Clemm, et al. Standards Track [Page 67] RFC 3253 Versioning Extensions to WebDAV March 2002

10.1 Advanced Versioning Packages

 Although a server MAY support any combination of advanced versioning
 features, in order to minimize the complexity of a WebDAV advanced
 versioning client, a WebDAV advanced versioning server SHOULD support
 one of the following packages:
 Advanced-Server-Workspace Package: basic-server-workspace package
 plus all advanced features
 Advanced-Client-Workspace Package: basic-client-workspace package
 plus all advanced features
 The advanced-server-workspace package supports advanced versioning
 capabilities for a client with no persistent state.  The advanced-
 client-workspace package supports advanced versioning capabilities
 for a client that maintains configuration state on the client.  A
 server that supports both advanced workspace packages will
 interoperate with all versioning clients.

10.2 Advanced Versioning Terms

 The following additional terms are used by the advanced versioning
 features.
 Collection
    A "collection" is a resource whose state consists of not only
    content and properties, but also a set of named "bindings", where
    a binding identifies what RFC 2518 calls an "internal member" of
    the collection.  Note that a binding is not a resource, but rather
    is a part of the state of a collection that defines a mapping from
    a binding name (a URL segment) to a resource (an internal member
    of the collection).
 Collection Version Resource
    A "collection version resource", or simply "collection version",
    captures the dead properties of a version-controlled collection,
    as well as the names of its version-controlled bindings (see
    Section 14).  A version-controlled binding is a binding to a
    version-controlled resource.  If the checkout-in-place feature is
    supported, a collection version can be created by checking out and
    then checking in a version-controlled collection.  If the
    working-resource feature is supported, a collection version can be
    created by checking out a collection version (to create a "working
    collection") and then checking in the working collection.

Clemm, et al. Standards Track [Page 68] RFC 3253 Versioning Extensions to WebDAV March 2002

 Configuration
    A "configuration" is a set of resources that consists of a root
    collection and all members (not just internal members) of that
    root collection that are not members of another configuration.
    The root collection is called the "configuration root", and the
    members of this set are called the "members of the configuration".
    Note that a collection (which is a single resource) is very
    different from a configuration (which is a set of resources).
 Baseline Resource
    A "baseline resource", or simply "baseline", of a collection is a
    version of the configuration that is rooted at that collection
    (see Section 12).  In particular, a baseline captures the
    DAV:checked-in version of every version-controlled member of that
    configuration.  Note that a collection version (which captures the
    state of a single resource) is very different from a collection
    baseline (which captures the state of a set of resources).
 Baseline-Controlled Collection
    A "baseline-controlled collection" is a collection from which
    baselines can be created (see Section 12).
 Version-Controlled Configuration Resource
    A "version-controlled configuration resource", or simply
    "version-controlled configuration", is a special kind of version-
    controlled resource that is associated with a baseline-controlled
    collection, and is used to create and access baselines of that
    collection (see Section 12).  When a collection is both version-
    controlled and baseline-controlled, a client can create a new
    version of the collection by checking out and checking in that
    collection, and it can create a new baseline of that collection by
    checking out and checking in the version-controlled configuration
    of that collection.
 Activity Resource
    An "activity resource", or simply "activity", is a resource that
    selects a set of versions that correspond to a single logical
    change, where the versions selected from a given version history
    form a single line of descent through that version history (see
    Section 13).

Clemm, et al. Standards Track [Page 69] RFC 3253 Versioning Extensions to WebDAV March 2002

11 Merge Feature

 When a user wants to accept the changes (new versions) created by
 someone else, it is important not just to update the version-
 controlled resources in the user's workspace with those new versions,
 since this could result in "backing out" changes the user has made to
 those version-controlled resources.  Instead, the versions created in
 another workspace should be "merged" into the user's version-
 controlled resources.
 The version history of a version-controlled resource provides the
 information needed to determine the result of the merge.  In
 particular, the merge should select whichever version is later in the
 line of descent from the root version.  In case the versions to be
 merged are on different lines of descent (neither version is a
 descendant of the other), neither version should be selected, but
 instead, a new version should be created that contains the logical
 merge of the content and dead properties of those versions.  The
 MERGE request can be used to check out each version-controlled
 resource that requires such a merge, and set the DAV:merge-set
 property of each checked-out resource to identify the version to be
 merged.  The user is responsible for modifying the content and dead
 properties of the checked-out resource so that it represents the
 logical merge of that version, and then adding that version to the
 DAV:predecessor-set of the checked-out resource.
 If the server is capable of automatically performing the merge, it
 MAY update the content, dead properties, and DAV:predecessor-set of
 the checked-out resource itself.  Before checking in the
 automatically merged resource, the user is responsible for verifying
 that the automatic merge is correct.

11.1 Additional Checked-Out Resource Properties

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

11.1.1 DAV:merge-set

 This property identifies each version that is to be merged into this
 checked-out resource.
 <!ELEMENT merge-set (href*)>

Clemm, et al. Standards Track [Page 70] RFC 3253 Versioning Extensions to WebDAV March 2002

11.1.2 DAV:auto-merge-set

 This property identifies each version that the server has merged into
 this checked-out resource.  The client should confirm that the merge
 has been performed correctly before moving a URL from the DAV:auto-
 merge-set to the DAV:predecessor-set of a checked-out resource.
 <!ELEMENT auto-merge-set (href*)>

11.2 MERGE Method

 The MERGE method performs the logical merge of a specified version
 (the "merge source") into a specified version-controlled resource
 (the "merge target").  If the merge source is neither an ancestor nor
 a descendant of the DAV:checked-in or DAV:checked-out version of the
 merge target, the MERGE checks out the merge target (if it is not
 already checked out) and adds the URL of the merge source to the
 DAV:merge-set of the merge target.  It is then the client's
 responsibility to update the content and dead properties of the
 checked-out merge target so that it reflects the logical merge of the
 merge source into the current state of the merge target.  The client
 indicates that it has completed the update of the merge target, by
 deleting the merge source URL from the DAV:merge-set of the checked-
 out merge target, and adding it to the DAV:predecessor-set.  As an
 error check for a client forgetting to complete a merge, the server
 MUST fail an attempt to CHECKIN a version-controlled resource with a
 non-empty DAV:merge-set.
 When a server has the ability to automatically update the content and
 dead properties of the merge target to reflect the logical merge of
 the merge source, it may do so unless DAV:no-auto-merge is specified
 in the MERGE request body.  In order to notify the client that a
 merge source has been automatically merged, the MERGE request MUST
 add the URL of the auto-merged source to the DAV:auto-merge-set
 property of the merge target, and not to the DAV:merge-set property.
 The client indicates that it has verified that the auto-merge is
 valid, by deleting the merge source URL from the DAV:auto-merge-set,
 and adding it to the DAV:predecessor-set.
 Multiple merge sources can be specified in a single MERGE request.
 The set of merge sources for a MERGE request is determined from the
 DAV:source element of the MERGE request body as follows:
  1. If DAV:source identifies a version, that version is a merge

source.

  1. If DAV:source identifies a version-controlled resource, the

DAV:checked-in version of that version-controlled resource is a

    merge source.

Clemm, et al. Standards Track [Page 71] RFC 3253 Versioning Extensions to WebDAV March 2002

  1. If DAV:source identifies a collection, the DAV:checked-in version

of each version-controlled resource that is a member of that

    collection is a merge source.
 The request-URL identifies the set of possible merge targets.  If the
 request-URL identifies a collection, any member of the configuration
 rooted at the request-URL is a possible merge target.  The merge
 target of a particular merge source is the version-controlled or
 checked-out resource whose DAV:checked-in or DAV:checked-out version
 is from the same version history as the merge source.  If a merge
 source has no merge target, that merge source is ignored.
 The MERGE response identifies the resources that a client must modify
 to complete the merge. It also identifies the resources modified by
 the request, so that a client can efficiently update any cached state
 it is maintaining.
 Marshalling:
    The request body MUST be a DAV:merge element.
    The set of merge sources is determined by the DAV:source element
    in the request body.
    <!ELEMENT merge ANY>
    ANY value: A sequence of elements with one DAV:source element, at
    most one DAV:no-auto-merge element, at most one DAV:no-checkout
    element, at most one DAV:prop element, and any legal set of
    elements that can occur in a DAV:checkout element.
    <!ELEMENT source (href+)>
    <!ELEMENT no-auto-merge EMPTY>
    <!ELEMENT no-checkout EMPTY>
    prop: see RFC 2518, Section 12.11
    The response for a successful request MUST be a 207 Multi-Status,
    where the DAV:multistatus XML element in the response body
    identifies all resources that have been modified by the request.
    multistatus: see RFC 2518, Section 12.9
    The response to a successful request MUST include a Location
    header containing the URL for the new version created by the
    checkin.
    The response MUST include a Cache-Control:no-cache header.

Clemm, et al. Standards Track [Page 72] RFC 3253 Versioning Extensions to WebDAV March 2002

 Preconditions:
    (DAV:cannot-merge-checked-out-resource): The DAV:source element
    MUST NOT identify a checked-out resource.  If the DAV:source
    element identifies a collection, the collection MUST NOT have a
    member that is a checked-out resource.
    (DAV:checkout-not-allowed): If DAV:no-checkout is specified in the
    request body, it MUST be possible to perform the merge without
    checking out any of the merge targets.
    All preconditions of the CHECKOUT operation apply to the checkouts
    performed by the request.
 Postconditions:
    (DAV:ancestor-version): If a merge target is a version-controlled
    or checked-out resource whose DAV:checked-in version or
    DAV:checked-out version is the merge source or is a descendant of
    the merge source, the merge target MUST NOT have been modified by
    the MERGE.
    (DAV:descendant-version): If the merge target was a checked-in
    version-controlled resource whose DAV:checked-in version was an
    ancestor of the merge source, an UPDATE operation MUST have been
    applied to the merge target to set its content and dead properties
    to be those of the merge source.  If the UPDATE method is not
    supported, the merge target MUST have been checked out, the
    content and dead properties of the merge target MUST have been set
    to those of the merge source, and the merge source MUST have been
    added to the DAV:auto-merge-set of the merge target.  The merge
    target MUST appear in a DAV:response XML element in the response
    body.
    (DAV:checked-out-for-merge): If the merge target was a checked-in
    version-controlled resource whose DAV:checked-in version was
    neither a descendant nor an ancestor of the merge source, a
    CHECKOUT MUST have been applied to the merge target.  All XML
    elements in the DAV:merge XML element that could appear in a
    DAV:checkout XML element MUST have been used as arguments to the
    CHECKOUT request.  The merge target MUST appear in a DAV:response
    XML element in the response body.
    (DAV:update-merge-set): If the DAV:checked-out version of the
    merge target is neither equal to nor a descendant of the merge
    source, the merge source MUST be added to either the DAV:merge-set
    or the DAV:auto-merge-set of the merge target.  The merge target
    MUST appear in a DAV:response XML element in the response body.

Clemm, et al. Standards Track [Page 73] RFC 3253 Versioning Extensions to WebDAV March 2002

    If a merge source has been added to the DAV:auto-merge-set, the
    content and dead properties of the merge target MUST have been
    modified by the server to reflect the result of a logical merge of
    the merge source and the merge target.  If a merge source has been
    added to the DAV:merge-set, the content and dead properties of the
    merge target MUST NOT have been modified by the server.  If
    DAV:no-auto-merge is specified in the request body, the merge
    source MUST NOT have been added to the DAV:auto-merge-set.
    (DAV:report-properties): If DAV:prop is specified in the request
    body, the properties specified in the DAV:prop element MUST be
    reported in the DAV:response elements in the response body.

11.2.1 Example - MERGE

 >>REQUEST
   MERGE /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:merge xmlns:D="DAV:">
     <D:source>
       <D:href>http://www.webdav.org/ws/dev/sally</D:href>
     </D:source>
   </D:merge>
 >>RESPONSE
   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxxx
   Cache-Control: no-cache
   <?xml version="1.0" encoding="utf-8" ?>
   <D:multistatus xmlns:D="DAV:">
     <D:response>
 <D:href>http://www.webdav.org/ws/public/src/parse.c</D:href>
 <D:status>HTTP/1.1 200 OK</D:status>
     </D:response>
     <D:response>
 <D:href>http://www.webdav.org/ws/public/doc/parse.html</D:href>
 <D:status>HTTP/1.1 200 OK</D:status>
     </D:response>
   </D:multistatus>

Clemm, et al. Standards Track [Page 74] RFC 3253 Versioning Extensions to WebDAV March 2002

 In this example, the DAV:checked-in versions from the workspace
 http://www.webdav.org/ws/dev/sally are merged into the version-
 controlled resources in the workspace
 http://www.webdav.org/ws/public.  The resources
 /ws/public/src/parse.c and /ws/public/doc/parse.html were modified by
 the request.

11.3 DAV:merge-preview Report

 A merge preview describes the changes that would result if the
 versions specified by the DAV:source element in the request body were
 to be merged into the resource identified by the request-URL
 (commonly, a collection).
 Marshalling:
    The request body MUST be a DAV:merge-preview XML element.
    <!ELEMENT merge-preview (source)>
    <!ELEMENT source (href)>
    The response body for a successful request MUST be a
    DAV:merge-preview-report XML element.
    <!ELEMENT merge-preview-report
     (update-preview | conflict-preview | ignore-preview)*>
    A DAV:update-preview element identifies a merge target whose
    DAV:checked-in property would change as a result of the MERGE, and
    identifies the merge source for that merge target.
    <!ELEMENT update-preview (target, version)>
    <!ELEMENT target (href)>
    <!ELEMENT version (href)>
    A DAV:conflict-preview element identifies a merge target that
    requires a merge.
    <!ELEMENT conflict-preview (target, common-ancestor, version)>
    A DAV:common-ancestor element identifies the version that is a
    common ancestor of both the merge source and the DAV:checked-in or
    DAV:checked-out version of the merge target.
    <!ELEMENT common-ancestor (href)>
    A DAV:ignore-preview element identifies a version that has no
    merge target and therefore would be ignored by the merge.

Clemm, et al. Standards Track [Page 75] RFC 3253 Versioning Extensions to WebDAV March 2002

    <!ELEMENT ignore-preview (version)>

11.3.1 Example - DAV:merge-preview 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:merge-preview xmlns:D="DAV:">
     <D:source>
       <D:href>http://www.webdav.org/ws/dev/fred</D:href>
     </D:source>
   </D:merge-preview>
 >>RESPONSE
   HTTP/1.1 200 OK
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxxx
   <?xml version="1.0" encoding="utf-8" ?>
   <D:merge-preview-report xmlns:D="DAV:">
     <D:conflict-preview>
       <D:target>
         <D:href>http://www.webdav.org/ws/public/foo.html</D:href>
       </D:target>
       <D:common-ancestor>
         <D:href>http://repo.webdav.org/his/23/ver/18</D:href>
       </D:common-ancestor>
       <D:version>
         <D:href>http://repo.webdav.org/his/23/ver/42</D:href>
       </D:version>
     </D:conflict-preview>
     <D:update-preview>
       <D:target>
         <D:href>http://www.webdav.org/ws/public/bar.html</D:href>
       </D:target>
       <D:version>
         <D:href>http://www.repo/his/42/ver/3</D:href>
       </D:version>
     </D:update-preview>
   </D:merge-preview-report>

Clemm, et al. Standards Track [Page 76] RFC 3253 Versioning Extensions to WebDAV March 2002

 In this example, the merge preview report indicates that version
 /his/23/ver/42 would be merged in /ws/public/foo.html, and version
 /his/42/ver/3 would update /ws/public/bar.html if the workspace
 http://www.webdav.org/ws/dev/fred was merged into the workspace
 http://www.webdav.org/ws/public.

11.4 Additional OPTIONS Semantics

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

11.5 Additional DELETE Semantics

 Additional Postconditions:
    (DAV:delete-version-reference): If a version is deleted, any
    reference to that version in a DAV:merge-set or DAV:auto-merge-set
    property MUST be removed.

11.6 Additional CHECKIN Semantics

 Additional Preconditions:
    (DAV:merge-must-be-complete): The DAV:merge-set and DAV:auto-
    merge-set of the checked-out resource MUST be empty or not exist.

12 Baseline Feature

 A configuration is a set of resources that consists of a root
 collection and all members of that root collection except those
 resources that are members of another configuration.  A configuration
 that contains a large number of resources can consume a large amount
 of space on a server.  This can make it prohibitively expensive to
 remember the state of an existing configuration by creating a
 Depth:infinity copy of its root collection.
 A baseline is a version resource that captures the state of each
 version-controlled member of a configuration.  A baseline history is
 a version history whose versions are baselines.  New baselines are
 created by checking out and then checking in a special kind of
 version-controlled resource called a version-controlled
 configuration.
 A collection that is under baseline control is called a baseline-
 controlled collection.  In order to allow efficient baseline
 implementation, the state of a baseline of a collection is limited to

Clemm, et al. Standards Track [Page 77] RFC 3253 Versioning Extensions to WebDAV March 2002

 be a set of versions and their names relative to the collection, and
 the operations on a baseline are limited to the creation of a
 baseline from a collection, and restoring or merging the baseline
 back into a collection.  A server MAY automatically put a collection
 under baseline control when it is created, or a client can use the
 BASELINE-CONTROL method to put a specified collection under baseline
 control.
 As a configuration gets large, it is often useful to break it up into
 a set of smaller configurations that form the logical "components" of
 that configuration.  In order to capture the fact that a baseline of
 a configuration is logically extended by a component configuration
 baseline, the component configuration baseline is captured as a
 "subbaseline" of the baseline.
 The root collection of a configuration is unconstrained with respect
 to its relationship to the root collection of any of its components.
 In particular, the root collection of a configuration can have a
 member that is the root collection of one of its components (e.g.,
 configuration /sys/x can have a component /sys/x/foo), can be a
 member of the root collection of one of its components (e.g.,
 configuration /sys/y/z can have a component /sys/y), or neither
 (e.g., configuration /sys/x can have a component /comp/bar).

12.1 Version-Controlled Configuration Properties

 Since a version-controlled configuration is a version-controlled
 resource, it has all the properties of a version-controlled resource.
 In addition, the baseline feature introduces the following REQUIRED
 property for a version-controlled configuration.

12.1.1 DAV:baseline-controlled-collection (protected)

 This property identifies the collection that contains the version-
 controlled resources whose DAV:checked-in versions are being tracked
 by this version-controlled configuration.  The DAV:version-
 controlled-configuration of the DAV:baseline-controlled-collection of
 a version-controlled configuration MUST identify that version-
 controlled configuration.
 <!ELEMENT baseline-controlled-collection (href)>

12.2 Checked-Out Configuration Properties

 Since a checked-out configuration is a checked-out resource, it has
 all the properties of a checked-out resource.  In addition, the
 baseline feature introduces the following REQUIRED property for a
 checked-out configuration.

Clemm, et al. Standards Track [Page 78] RFC 3253 Versioning Extensions to WebDAV March 2002

12.2.1 DAV:subbaseline-set

 This property determines the DAV:subbaseline-set property of the
 baseline that results from checking in this resource.
 A server MAY reject attempts to modify the DAV:subbaseline-set of a
 checked-out configuration.
 <!ELEMENT subbaseline-set (href*)>

12.3 Baseline Properties

 The DAV:resourcetype of a baseline MUST be DAV:baseline.  Since a
 baseline is a version resource, it has all the properties of a
 version resource.  In addition, the baseline feature introduces the
 following REQUIRED properties for a baseline.

12.3.1 DAV:baseline-collection (protected)

 This property contains a server-defined URL for a collection, where
 each member of this collection MUST either be a version-controlled
 resource with the same DAV:checked-in version and relative name as a
 version-controlled member of the baseline-controlled collection at
 the time the baseline was created, or be a collection needed to
 provide the relative name for a version-controlled resource.
 <!ELEMENT baseline-collection (href)>

12.3.2 DAV:subbaseline-set (protected)

 The URLs in the DAV:subbaseline-set property MUST identify a set of
 other baselines.  The subbaselines of a baseline are the baselines
 identified by its DAV:subbaseline-set and all subbaselines of the
 baselines identified by its DAV:subbaseline-set.
 <!ELEMENT subbaseline-set (href*)>

12.4 Additional Resource Properties

 The baseline feature introduces the following REQUIRED property for a
 resource.

12.4.1 DAV:version-controlled-configuration (computed)

 If the resource is a member of a version-controlled configuration
 (i.e. the resource is a collection under baseline control or is a
 member of a collection under baseline control), this property
 identifies that version-controlled configuration.

Clemm, et al. Standards Track [Page 79] RFC 3253 Versioning Extensions to WebDAV March 2002

 <!ELEMENT version-controlled-configuration (href)>

12.5 Additional Workspace Properties

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

12.5.1 DAV:baseline-controlled-collection-set (computed)

 This property identifies each member of the workspace that is a
 collection under baseline control (as well as the workspace itself,
 if it is under baseline control).
 <!ELEMENT baseline-controlled-collection-set (href*)>

12.6 BASELINE-CONTROL Method

 A collection can be placed under baseline control with a
 BASELINE-CONTROL request.  When a collection is placed under baseline
 control, the DAV:version-controlled-configuration property of the
 collection is set to identify a new version-controlled configuration.
 This version-controlled configuration can be checked out and then
 checked in to create a new baseline for that collection.
 If a baseline is specified in the request body, the DAV:checked-in
 version of the new version-controlled configuration will be that
 baseline, and the collection is initialized to contain version-
 controlled members whose DAV:checked-in versions and relative names
 are determined by the specified baseline.
 If no baseline is specified, a new baseline history is created
 containing a baseline that captures the state of the version-
 controlled members of the collection, and the DAV:checked-in version
 of the version-controlled configuration will be that baseline.
 Marshalling:
    If a request body is included, it MUST be a DAV:baseline-control
    XML element.
    <!ELEMENT baseline-control ANY>
    ANY value: A sequence of elements with at most one DAV:baseline
    element.
    <!ELEMENT baseline (href)>
    If a response body for a successful request is included, it MUST
    be a DAV:baseline-control-response XML element.

Clemm, et al. Standards Track [Page 80] RFC 3253 Versioning Extensions to WebDAV March 2002

    <!ELEMENT baseline-control-response ANY>
    The response MUST include a Cache-Control:no-cache header.
 Preconditions:
    (DAV:version-controlled-configuration-must-not-exist): The
    DAV:version-controlled-configuration property of the collection
    identified by the request-URL MUST not exist.
    (DAV:must-be-baseline): The DAV:href of the DAV:baseline element
    in the request body MUST identify a baseline.
    (DAV:must-have-no-version-controlled-members): If a DAV:baseline
    element is specified in the request body, the collection
    identified by the request-URL MUST have no version-controlled
    members.
    (DAV:one-baseline-controlled-collection-per-history-per-
    workspace):  If the request-URL identifies a workspace or a member
    of a workspace, and if a baseline is specified in a DAV:baseline
    element in the request body, then there MUST NOT be another
    collection in that workspace whose DAV:version-controlled-
    configuration property identifies a version-controlled
    configuration for the baseline history of that baseline.
 Postconditions:
    (DAV:create-version-controlled-configuration): A new version-
    controlled configuration is created, whose DAV:baseline-
    controlled-collection property identifies the collection.
    (DAV:reference-version-controlled-configuration): The
    DAV:version-controlled-configuration of the collection identifies
    the new version-controlled configuration.
    (DAV:select-existing-baseline): If the request body specifies a
    baseline, the DAV:checked-in property of the new version-
    controlled configuration MUST have been set to identify this
    baseline.  A version-controlled member of the collection will be
    created for each version in the baseline, where the version-
    controlled member will have the content and dead properties of
    that version, and will have the same name relative to the
    collection as the corresponding version-controlled resource had
    when the baseline was created.  Any nested collections that are
    needed to provide the appropriate name for a version-controlled
    member will be created.

Clemm, et al. Standards Track [Page 81] RFC 3253 Versioning Extensions to WebDAV March 2002

    (DAV:create-new-baseline): If no baseline is specified in the
    request body, the request MUST have created a new baseline history
    at a server-defined URL, and MUST have created a new baseline in
    that baseline history.  The DAV:baseline-collection of the new
    baseline MUST identify a collection whose members have the same
    relative name and DAV:checked-in version as the version-controlled
    members of the request collection.  The DAV:checked-in property of
    the new version-controlled configuration MUST identify the new
    baseline.

12.6.1 Example - BASELINE-CONTROL

 >>REQUEST
   BASELINE-CONTROL /src 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:baseline-control xmlns:D="DAV:">
     <D:href>http://www.webdav.org/repo/blh/13/ver/8</D:href>
   </D:baseline-control>
 >>RESPONSE
   HTTP/1.1 200 OK
   Cache-Control: no-cache
   Content-Length: 0

Clemm, et al. Standards Track [Page 82] RFC 3253 Versioning Extensions to WebDAV March 2002

 In this example, the collection /src is placed under baseline
 control, and is populated with members from an existing baseline.  A
 new version-controlled configuration (/repo/vcc/128) is created and
 associated with /src, and /src is initialized with version-controlled
 members whose DAV:checked-in versions are those selected by the
 DAV:baseline-collection (/repo/bc/15) of the specified baseline
 (/repo/blh/13/ver/8).  The following diagram illustrates the
 resulting state on the server.
       +-------------------------------------+
       |Baseline-Controlled Collection       |<------+
       |/src                                 |       |
       |-------------------------------------|       |
       |DAV:version-controlled-configuration +---+   |
       +-------------------------------------+   |   |
                                                 |   |
                                                 |   |
       +-------------------------------------+   |   |
       |Version-Controlled Configuration     |<--+   |
       |/repo/vcc/128                        |       |
       |-------------------------------------|       |
       |DAV:baseline-controlled-collection   +-------+
       |-------------------------------------|
       |DAV:checked-in                       +-------+
       +-------------------------------------+       |
       |DAV:version-history                  +---+   |
       +-------------------------------------+   |   |
                                                 |   |
                                                 |   |
       +------------------------+                |   |
       |Baseline History        |<---------------+   |
       |/repo/blh/13            |                    |
       |------------------------+                    |
       |DAV:version-set         +----------------+   |
       +------------------------+    |   |   |   |   |
                                     v   |   v   v   |
                                         |           |
       +------------------------+        |           |
       |Baseline                |<-------+-----------+
       |/repo/blh/13/ver/8      |
       |------------------------+     +--------------+
       |DAV:baseline-collection +---->|Collection    |
       +------------------------+     |/repo/bc/15   |
                                      +--------------+

Clemm, et al. Standards Track [Page 83] RFC 3253 Versioning Extensions to WebDAV March 2002

 In order to create new baselines of /src, /repo/vcc/128 can be
 checked out, new versions can be created or selected by the version-
 controlled members of /src, and then /repo/vcc/128 can be checked in
 to capture the current state of those version-controlled members.

12.7 DAV:compare-baseline Report

 A DAV:compare-baseline report contains the differences between the
 baseline identified by the request-URL (the "request baseline") and
 the baseline specified in the request body (the "compare baseline").
 Marshalling:
    The request body MUST be a DAV:compare-baseline XML element.
    <!ELEMENT compare-baseline (href)>
    The response body for a successful request MUST be a DAV:compare-
    baseline-report XML element.
    <!ELEMENT compare-baseline-report
     (added-version | deleted-version | changed-version)*>
    A DAV:added-version element identifies a version that is the
    DAV:checked-in version of a member of the DAV:baseline-collection
    of the compare baseline, but no version in the version history of
    that version is the DAV:checked-in version of a member of the
    DAV:baseline-collection of the request baseline.
    <!ELEMENT added-version (href)>
    A DAV:deleted-version element identifies a version that is the
    DAV:checked-in version of a member of the DAV:baseline-collection
    of the request baseline, but no version in the version history of
    that version is the DAV:checked-in version of a member of the
    DAV:baseline-collection of the compare baseline.
    <!ELEMENT deleted-version (href)>
    A DAV:changed-version element identifies two different versions
    from the same version history that are the DAV:checked-in version
    of the DAV:baseline-collection of the request baseline and the
    compare baseline, respectively.
    <!ELEMENT changed-version (href, href)>

Clemm, et al. Standards Track [Page 84] RFC 3253 Versioning Extensions to WebDAV March 2002

 Preconditions:
    (DAV:must-be-baseline): The DAV:href in the request body MUST
    identify a baseline.
    (DAV:baselines-from-same-history): A server MAY require that the
    baselines being compared be from the same baseline history.

12.7.1 Example - DAV:compare-baseline Report

 >>REQUEST
   REPORT /bl-his/12/bl/14 HTTP/1.1
   Host: repo.webdav.com
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxxx
   <?xml version="1.0" encoding="utf-8" ?>
   <D:compare-baseline xmlns:D="DAV:">
     <D:href>http://repo.webdav.org/bl-his/12/bl/15</D:href>
   </D:compare-baseline>
 >>RESPONSE
   HTTP/1.1 200 OK
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxxx
   <?xml version="1.0" encoding="utf-8" ?>
   <D:compare-baseline-report xmlns:D="DAV:">
     <D:added-version>
       <D:href>http://repo.webdav.org/his/23/ver/8</D:href>
     </D:added-version>
     <D:changed-version>
       <D:href>http://repo.webdav.org/his/29/ver/12</D:href>
       <D:href>http://repo.webdav.org/his/29/ver/19</D:href>
     </D:changed-version>
     <D:deleted-version>
       <D:href>http://repo.webdav.org/his/12/ver/4</D:href>
     </D:deleted-version>
   </D:compare-baseline-report>
 In this example, the differences between baseline 14 and baseline 15
 of http://repo.webdav.org/bl-his/12 are identified.

Clemm, et al. Standards Track [Page 85] RFC 3253 Versioning Extensions to WebDAV March 2002

12.8 Additional OPTIONS Semantics

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

12.9 Additional MKCOL Semantics

 Additional Postconditions:
    If a server automatically puts a newly created collection under
    baseline control, all postconditions for BASELINE-CONTROL apply to
    the MKCOL.

12.10 Additional COPY Semantics

 Additional Postconditions:
    If the request creates a new collection at the Destination, and a
    server automatically puts a newly created collection under
    baseline control, all postconditions for BASELINE-CONTROL apply to
    the COPY.

12.11 Additional CHECKOUT Semantics

 Additional Preconditions:
    (DAV:must-not-update-baseline-collection): If the request-URL
    identifies a member of the configuration rooted at the
    DAV:baseline-collection of a baseline, the request MUST fail.

12.12 Additional CHECKIN Semantics

 Additional Preconditions:
    (DAV:no-checked-out-baseline-controlled-collection-members): If
    the request-URL identifies a version-controlled configuration, all
    version-controlled members of the DAV:baseline-controlled-
    collection of the version-controlled configuration MUST be
    checked-in.
    (DAV:one-version-per-history-per-baseline): If the request-URL
    identifies a version-controlled configuration, the set of versions
    selected by that version-controlled configuration MUST contain at
    most one version from any version history, where a version is
    selected by a version-controlled configuration if the version is
    identified by the DAV:checked-in property of any member of the

Clemm, et al. Standards Track [Page 86] RFC 3253 Versioning Extensions to WebDAV March 2002

    configuration rooted at the DAV:baseline-controlled collection of
    that version-controlled configuration, or is identified by the
    DAV:checked-in property of any member of the configuration rooted
    at the DAV:baseline-collection of any subbaseline of that
    version-controlled configuration.
    (DAV:cannot-modify-version-controlled-configuration): If the
    request-URL identifies a version-controlled member of a baseline-
    controlled collection whose version-controlled configuration is
    checked-in, the request MUST fail unless the DAV:auto-version
    property of the version-controlled configuration will
    automatically check out that version-controlled configuration when
    it is modified.
 Additional Postconditions:
    (DAV:create-baseline-collection): If the request-URL identifies a
    version-controlled configuration, the DAV:baseline-collection of
    the new baseline identifies a collection whose members have the
    same relative name and DAV:checked-in version as the members of
    the DAV:baseline-controlled-collection of the version-controlled
    configuration at the time of the request.
    (DAV:modify-configuration): If the request-URL identifies a
    version-controlled member of a baseline-controlled collection,
    this is a modification to the version-controlled configuration of
    that baseline-controlled collection, and standard auto-versioning
    semantics apply.

12.13 Additional UPDATE Semantics

 Additional Preconditions:
    (DAV:baseline-controlled-members-must-be-checked-in): If the
    request-URL identifies a version-controlled configuration, then
    all version-controlled members of the DAV:baseline-controlled-
    collection of that version-controlled configuration MUST be
    checked-in.
    (DAV:must-not-update-baseline-collection): If the request-URL
    identifies a member of the configuration rooted at the
    DAV:baseline-collection of a baseline, the request MUST fail.
    (DAV:cannot-modify-version-controlled-configuration): If the
    request updates the DAV:checked-in property of any version-
    controlled member of a baseline-controlled collection whose
    version-controlled configuration is checked-in, the request MUST

Clemm, et al. Standards Track [Page 87] RFC 3253 Versioning Extensions to WebDAV March 2002

    fail unless the DAV:auto-version property of the version-
    controlled configuration will automatically check out that
    version-controlled configuration when it is modified.
 Additional Postconditions:
    (DAV:set-baseline-controlled-collection-members): If the request
    updated the DAV:checked-in property of a version-controlled
    configuration, then the version-controlled members of the
    DAV:baseline-controlled-collection of that version-controlled
    configuration MUST have been updated so that they have the same
    relative name, content, and dead properties as the members of the
    DAV:baseline-collection of the baseline.  In particular:
  1. A version-controlled member for a given version history MUST

have been deleted if there is no version-controlled member for

       that version history in the DAV:baseline-collection of the
       baseline.
    -  A version-controlled member for a given version history MUST
       have been renamed if its name relative to the baseline-
       controlled collection is different from that of the version-
       controlled member for that version history in the
       DAV:baseline-collection of the baseline.
    -  A new version-controlled member MUST have been created for each
       member of the DAV:baseline-collection of the baseline for which
       there is no corresponding version-controlled member in the
       baseline-controlled collection.
    -  An UPDATE request MUST have been applied to each version-
       controlled member for a given version history whose
       DAV:checked-in version is not the same as that of the version-
       controlled member for that version history in the
       DAV:baseline-collection of the baseline.
    (DAV:update-subbaselines): If the request updated a version-
    controlled configuration whose DAV:baseline-controlled-collection
    contains a baseline-controlled member for one of the subbaselines
    of the request baseline, then the DAV:checked-in property of the
    version-controlled configuration of that baseline-controlled
    member MUST have been updated to be that subbaseline.  If the
    request updated a version-controlled configuration whose
    DAV:baseline-controlled-collection is a member of a workspace that
    contains a baseline-controlled member for one of the subbaselines
    of the request baseline, then the DAV:checked-in property of the
    version-controlled configuration of that baseline-controlled
    member MUST have been updated to be that subbaseline.

Clemm, et al. Standards Track [Page 88] RFC 3253 Versioning Extensions to WebDAV March 2002

    (DAV:modify-configuration): If the request updated the
    DAV:checked-in property of any version-controlled member of a
    baseline-controlled collection, and if this DAV:checked-in
    property differs from the DAV:checked-in property of the
    corresponding version-controlled member of the DAV:baseline-
    collection of the DAV:checked-in baseline of the DAV:version-
    controlled-configuration of the baseline-controlled collection,
    then this is a modification to that version-controlled
    configuration, and standard auto-versioning semantics apply.

12.14 Additional MERGE Semantics

 If the merge source is a baseline, the merge target is a version-
 controlled configuration for the baseline history of that baseline,
 where the baseline-controlled collection of that version-controlled
 configuration is a member of the collection identified by the
 request-URL.
 Additional Preconditions:
    (DAV:must-not-update-baseline-collection): Same semantics as
    UPDATE (see Section 12.13).
    (DAV:cannot-modify-version-controlled-configuration): Same
    semantics as UPDATE (see Section 12.13).
 Additional Postconditions:
    (DAV:merge-baseline): If the merge target is a version-controlled
    configuration whose DAV:checked-out baseline is not a descendant
    of the merge baseline, then the merge baseline MUST have been
    added to the DAV:auto-merge-set of a version-controlled
    configuration.  The DAV:checked-in version of each member of the
    DAV:baseline-collection of that baseline MUST have been merged
    into the DAV:baseline-controlled-collection of that version-
    controlled configuration.
    (DAV:merge-subbaselines): If the merge target is a version-
    controlled configuration whose DAV:baseline-controlled-collection
    contains a baseline-controlled member for one of the subbaselines
    of the merge baseline, then that subbaseline MUST have been merged
    into the version-controlled configuration of that baseline-
    controlled member.  If the merge target is a version-controlled
    configuration whose DAV:baseline-controlled-collection is a member
    of a workspace that contains a baseline-controlled member for one
    of the subbaselines of the merge baseline, then that subbaseline
    MUST have been merged into the version-controlled configuration of
    that baseline-controlled member.

Clemm, et al. Standards Track [Page 89] RFC 3253 Versioning Extensions to WebDAV March 2002

    (DAV:set-baseline-controlled-collection-members): Same semantics
    as UPDATE (see Section 12.13).
    (DAV:modify-configuration): Same semantics as UPDATE (see Section
    12.13).

13 Activity Feature

 An activity is a resource that selects a set of versions that are on
 a single "line of descent", where a line of descent is a sequence of
 versions connected by successor relationships.  If an activity
 selects versions from multiple version histories, the versions
 selected in each version history must be on a single line of descent.
 A common problem that motivates the use of activities is that it is
 often desirable to perform several different logical changes in a
 single workspace, and then selectively merge a subset of those
 logical changes to other workspaces.  An activity can be used to
 represent a single logical change, where an activity tracks all the
 resources that were modified to effect that single logical change.
 When a version-controlled resource is checked out, the user specifies
 which activity should be associated with a new version that will be
 created when that version-controlled resource is checked in.  It is
 then possible to select a particular logical change for merging into
 another workspace, by specifying the appropriate activity in a MERGE
 request.
 Another common problem is that although a version-controlled resource
 may need to have multiple lines of descent, all work done by members
 of a given team must be on a single line of descent (to avoid merging
 between team members).  An activity resource provides the mechanism
 for addressing this problem.  When a version-controlled resource is
 checked out, a client can request that an existing activity be used
 or that a new activity be created.  Activity semantics then ensure
 that all versions in a given version history that are associated with
 an activity are on a single line of descent.  If all members of a
 team share a common activity (or sub-activities of a common
 activity), then all changes made by members of that team will be on a
 single line of descent.

Clemm, et al. Standards Track [Page 90] RFC 3253 Versioning Extensions to WebDAV March 2002

 The following diagram illustrates activities.  Version V5 is the
 latest version of foo.html selected by activity Act-2, and version V8
 is the latest version of bar.html selected by activity Act-2.
                foo.html History       bar.html History
                      +---+                  +---+
                 Act-1|   |V1           Act-1|   |V6
                      +---+                  +---+
                        |                      |
                        |                      |
                      +---+                  +---+
                 Act-1|   |V2           Act-2|   |V7
                      +---+                  +---+
                     /     \                   |
                    /       \                  |
               +---+         +---+           +---+
          Act-1|   |V3  Act-2|   |V4    Act-2|   |V8
               +---+         +---+           +---+
                               |               |
                               |               |
                             +---+           +---+
                        Act-2|   |V5    Act-3|   |V9
                             +---+           +---+
 Activities appear under a variety of names in existing versioning
 systems.  When an activity is used to capture a logical change, it is
 commonly called a "change set".  When an activity is used to capture
 a line of descent, it is commonly called a "branch".  When a system
 supports both branches and change sets, it is often useful to require
 that a particular change set occur on a particular branch.  This
 relationship can be captured by making the change set activity be a
 "subactivity" of the branch activity.

13.1 Activity Properties

 The DAV:resourcetype of an activity MUST be DAV:activity.
 The activity feature introduces the following REQUIRED properties for
 an activity.

13.1.1 DAV:activity-version-set (computed)

 This property identifies each version whose DAV:activity-set property
 identifies this activity.  Multiple versions of a single version
 history can be selected by an activity's DAV:activity-version-set

Clemm, et al. Standards Track [Page 91] RFC 3253 Versioning Extensions to WebDAV March 2002

 property, but all DAV:activity-version-set versions from a given
 version history must be on a single line of descent from the root
 version of that version history.
 <!ELEMENT activity-version-set (href*)>

13.1.2 DAV:activity-checkout-set (computed)

 This property identifies each checked-out resource whose
 DAV:activity-set identifies this activity.
 <!ELEMENT activity-checkout-set (href*)>

13.1.3 DAV:subactivity-set

 This property identifies each activity that forms a part of the
 logical change being captured by this activity.  An activity behaves
 as if its DAV:activity-version-set is extended by the DAV:activity-
 version-set of each activity identified in the DAV:subactivity-set.
 In particular, the versions in this extended set MUST be on a single
 line of descent, and when an activity selects a version for merging,
 the latest version in this extended set is the one that will be
 merged.
 A server MAY reject attempts to modify the DAV:subactivity-set of an
 activity.
 <!ELEMENT subactivity-set (href*)>

13.1.4 DAV:current-workspace-set (computed)

 This property identifies each workspace whose DAV:current-activity-
 set identifies this activity.
 <!ELEMENT current-workspace-set (href*)>

13.2 Additional Version Properties

 The activity feature introduces the following REQUIRED property for a
 version.

Clemm, et al. Standards Track [Page 92] RFC 3253 Versioning Extensions to WebDAV March 2002

13.2.1 DAV:activity-set

 This property identifies the activities that determine to which
 logical changes this version contributes, and on which lines of
 descent this version appears.  A server MAY restrict the
 DAV:activity-set to identify a single activity.  A server MAY refuse
 to allow the value of the DAV:activity-set property of a version to
 be modified.
 <!ELEMENT activity-set (href*)>

13.3 Additional Checked-Out Resource Properties

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

13.3.1 DAV:unreserved

 This property of a checked-out resource indicates whether the
 DAV:activity-set of another checked-out resource associated with the
 version history of this version-controlled resource can have an
 activity that is in the DAV:activity-set property of this checked-out
 resource.
 A result of the requirement that an activity must form a single line
 of descent through a given version history is that if multiple
 checked-out resources for a given version history are checked out
 unreserved into a single activity, only the first CHECKIN will
 succeed.  Before another of these checked-out resources can be
 checked in, the user will first have to merge into that checked-out
 resource the latest version selected by that activity from that
 version history, and then modify the DAV:predecessor-set of that
 checked-out resource to identify that version.
 <!ELEMENT unreserved (#PCDATA)>
 PCDATA value: boolean

13.3.2 DAV:activity-set

 This property of a checked-out resource determines the DAV:activity-
 set property of the version that results from checking in this
 resource.

13.4 Additional Workspace Properties

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

Clemm, et al. Standards Track [Page 93] RFC 3253 Versioning Extensions to WebDAV March 2002

13.4.1 DAV:current-activity-set

 This property identifies the activities that currently are being
 performed in this workspace.  When a member of this workspace is
 checked out, if no activity is specified in the checkout request, the
 DAV:current-activity-set will be used.  This allows an activity-
 unaware client to update a workspace in which activity tracking is
 required.  The DAV:current-activity-set MAY be restricted to identify
 at most one activity.
 <!ELEMENT current-activity-set (href*)>

13.5 MKACTIVITY Method

 A MKACTIVITY request creates a new activity resource.  A server MAY
 restrict activity creation to particular collections, but a client
 can determine the location of these collections from a DAV:activity-
 collection-set OPTIONS request.
 Marshalling:
    If a request body is included, it MUST be a DAV:mkactivity XML
    element.
    <!ELEMENT mkactivity ANY>
    If a response body for a successful request is included, it MUST
    be a DAV:mkactivity-response XML element.
    <!ELEMENT mkactivity-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:activity-location-ok): The request-URL MUST identify a
    location where an activity can be created.
 Postconditions:
    (DAV:initialize-activity): A new activity exists at the request-
    URL.  The DAV:resourcetype of the activity MUST be DAV:activity.

Clemm, et al. Standards Track [Page 94] RFC 3253 Versioning Extensions to WebDAV March 2002

13.5.1 Example - MKACTIVITY

 >>REQUEST
   MKACTIVITY /act/test-23 HTTP/1.1
   Host: repo.webdav.org
   Content-Length: 0
 >>RESPONSE
   HTTP/1.1 201 Created
   Cache-Control: no-cache
 In this example, a new activity is created at
 http://repo.webdav.org/act/test-23.

13.6 DAV:latest-activity-version Report

 The DAV:latest-activity-version report can be applied to a version
 history to identify the latest version that is selected from that
 version history by a given activity.
 Marshalling:
    The request body MUST be a DAV:latest-activity-version XML
    element.
    <!ELEMENT latest-activity-version (href)>
    The response body for a successful request MUST be a DAV:latest-
    activity-version-report XML element.
    <!ELEMENT latest-activity-version-report (href)>
    The DAV:href of the response body MUST identify the version of the
    given version history that is a member of the DAV:activity-
    version-set of the given activity and has no descendant that is a
    member of the DAV:activity-version-set of that activity.
 Preconditions:
    (DAV:must-be-activity): The DAV:href in the request body MUST
    identify an activity.

Clemm, et al. Standards Track [Page 95] RFC 3253 Versioning Extensions to WebDAV March 2002

13.7 Additional OPTIONS Semantics

 If the server supports the activity feature, it MUST include
 "activity" 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:activity-collection-set element MAY be included in the request
 body to identify collections that may contain activity 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:activity-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:activity-collection-set element.
    <!ELEMENT activity-collection-set (href*)>
    If DAV:activity-collection-set is included in the request body,
    the response body for a successful request MUST contain a
    DAV:activity-collection-set element identifying collections that
    may contain activities.  An identified collection MAY be the root
    collection of a tree of collections, all of which may contain
    activities.  Since different servers can control different parts
    of the URL namespace, different resources on the same host MAY
    have different DAV:activity-collection-set values.  The identified
    collections MAY be located on different hosts from the resource.

13.8 Additional DELETE Semantics

 Additional Postconditions:
    (DAV:delete-activity-reference): If an activity is deleted, any
    reference to that activity in a DAV:activity-set,
    DAV:subactivity-set, or DAV:current-activity-set MUST be removed.

Clemm, et al. Standards Track [Page 96] RFC 3253 Versioning Extensions to WebDAV March 2002

13.9 Additional MOVE Semantics

 Additional Postconditions:
    (DAV:update-checked-out-reference): If a checked-out resource is
    moved, any reference to that resource in a DAV:activity-checkout-
    set property MUST be updated to refer to the new location of that
    resource.
    (DAV:update-activity-reference): If the request-URL identifies an
    activity, any reference to that activity in a DAV:activity-set,
    DAV:subactivity-set, or DAV:current-activity-set MUST be updated
    to refer to the new location of that activity.
    (DAV:update-workspace-reference): If the request-URL identifies a
    workspace, any reference to that workspace in a DAV:current-
    workspace-set property MUST be updated to refer to the new
    location of that workspace.

13.10 Additional CHECKOUT Semantics

 A CHECKOUT request MAY specify the DAV:activity-set for the checked-
 out resource.
 Additional Marshalling:
    <!ELEMENT checkout ANY> ANY value: A sequence of elements with at
    most one DAV:activity-set and at most one DAV:unreserved.
    <!ELEMENT activity-set (href+ | new)>
    <!ELEMENT new EMPTY>
    <!ELEMENT unreserved EMPTY>
 Additional Preconditions:
    (DAV:one-checkout-per-activity-per-history): If there is a request
    activity set, unless DAV:unreserved is specified, another checkout
    from a version of that version history MUST NOT select an activity
    in that activity set.
    (DAV:linear-activity): If there is a request activity set, unless
    DAV:unreserved is specified, the selected version MUST be a
    descendant of all other versions of that version history that
    select that activity.

Clemm, et al. Standards Track [Page 97] RFC 3253 Versioning Extensions to WebDAV March 2002

 Additional Postconditions:
    (DAV:initialize-activity-set): The DAV:activity-set of the
    checked-out resource is set as follows:
  1. If DAV:new is specified as the DAV:activity-set in the request

body, then a new activity created by the server is used.

  1. Otherwise, if activities are specified in the request body,

then those activities are used.

  1. Otherwise, if the version-controlled resource is a member of a

workspace and the DAV:current-activity-set of the workspace is

       set, then those activities are used.
    -  Otherwise, the DAV:activity-set of the DAV:checked-out version
       is used.
    (DAV:initialize-unreserved): If DAV:unreserved was specified in
    the request body, then the DAV:unreserved property of the
    checked-out resource MUST be "true".

13.10.1 Example - CHECKOUT with an activity

 >>REQUEST
   CHECKOUT /ws/public/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:checkout xmlns:D="DAV:">
     <D:activity-set>
       <D:href>http://repo.webdav.org/act/fix-bug-23</D:href>
     </D:activity-set>
   </D:checkout>
 >>RESPONSE
   HTTP/1.1 200 OK
   Cache-Control: no-cache
 In this example, the CHECKOUT is being performed in the
 http://repo.webdav.org/act/fix-bug-23 activity.

Clemm, et al. Standards Track [Page 98] RFC 3253 Versioning Extensions to WebDAV March 2002

13.11 Additional CHECKIN Semantics

 Additional Preconditions:
    (DAV:linear-activity): Any version which is in the version history
    of the checked-out resource and whose DAV:activity-set identifies
    an activity from the DAV:activity-set of the checked-out resource
    MUST be an ancestor of the checked-out resource.
    (DAV:atomic-activity-checkin): If the request-URL identifies an
    activity, the server MAY fail the request if any of the checked-
    out resources in the DAV:activity-checkout-set of either that
    activity or any subactivity of that activity cannot be checked in.
 Additional Postconditions:
    (DAV:initialize-activity-set): The DAV:activity-set of the new
    version MUST have been initialized to be the same as the
    DAV:activity-set of the checked-out resource.
    (DAV:activity-checkin): If the request-URL identified an activity,
    the server MUST have successfully applied the CHECKIN request to
    each checked-out resource in the DAV:activity-checkout-set of both
    that activity and any subactivity of that activity.

13.12 Additional MERGE Semantics

 If the DAV:source element of the request body identifies an activity,
 then for each version history containing a version selected by that
 activity, the latest version selected by that activity is a merge
 source.  Note that the versions selected by an activity are the
 versions in its DAV:activity-version-set unioned with the versions
 selected by the activities in its DAV:subactivity-set.
 Additional Marshalling:
    <!ELEMENT checkin-activity EMPTY>
 Additional Postconditions:
    (DAV:checkin-activity): If DAV:checkin-activity is specified in
    the request body, and if the DAV:source element in the request
    body identifies an activity, a CHECKIN request MUST have been
    successfully applied to that activity before the merge sources
    were determined.

Clemm, et al. Standards Track [Page 99] RFC 3253 Versioning Extensions to WebDAV March 2002

14 Version-Controlled-Collection Feature

 As with any versionable resource, when a collection is put under
 version control, a version history resource is created to contain
 versions for that version-controlled collection.  In order to
 preserve standard versioning semantics (a version of a collection
 should not be modifiable), a collection version only records
 information about the version-controlled bindings of that collection.
 In order to cleanly separate a modification to the namespace from a
 modification to content or dead properties, a version of a collection
 has no members, but instead records in its DAV:version-controlled-
 binding-set property the binding name and version history resource of
 each version-controlled internal member of that collection.  If,
 instead, a collection version contained bindings to other versions,
 creating a new version of a resource would require creating a new
 version of all the collection versions that contain that resource,
 which would cause activities to become entangled.  For example,
 suppose a "feature-12" activity created a new version of /x/y/a.html.
 If a collection version contained bindings to versions of its
 members, a new version of /x/y would have to be created to contain
 the new version of /x/y/a.html, and a new version of /x would have to
 be created to contain the new version of /x/y.  Now suppose a
 "bugfix-47" activity created a new version of /x/z/b.html.  Again, a
 new version of /x/z and a new version of /x would have to be created
 to contain the new version of /x/y/b.html.  But now it is impossible
 to merge just "bugfix-47" into another workspace without "feature-
 12", because the version of /x that contains the desired version of
 /x/z/b.html also contains version of /x/y/a.html created for
 "feature-12".  If, instead, a collection version just records the
 binding name and version history resource of each version-controlled
 internal member, changing the version selected by a member of that
 collection would not require a new version of the collection.  The
 new version is still in the same version history so no new collection
 version is required, and "feature-12" and "bugfix-47" would not
 become entangled.
 In the following example, there are three version histories, named
 VH14, VH19, and VH24, where VH14 contains versions of a collection.
 The version-controlled collection /x has version V2 of version
 history VH14 as its DAV:checked-in version.  Since V2 has recorded
 two version controlled bindings, one with binding name "a" to version
 history VH19, and the other with binding name "b" to version history
 VH24, /x MUST have two version-controlled bindings, one named "a" to
 a version-controlled resource for history VH19, and the other named
 "b" to a version-controlled resource for history VH24.  The version-

Clemm, et al. Standards Track [Page 100] RFC 3253 Versioning Extensions to WebDAV March 2002

 controlled resource /x/a currently has V4 of VH19 as its
 DAV:checked-in version, while /x/b has V8 of VH24 as its
 DAV:checked-in version.
                                                        VH19
                                                     +---------+
                                                     | +---+   |
                                                     | |   |V4 |
                                                     | +---+   |
                                                     |   |     |
                                                     |   |     |
                                                     | +---+   |
                                                     | |   |V5 |
                                          VH14       | +---+   |
                                      +---------+    |   |     |
                                      | +---+   |    |   |     |
             a  +---+                 | |   |V1 |    | +---+   |
           ---->|   |checked-in=V4    | +---+   | a  | |   |V6 |
          /     +---+                 |   |   ------>| +---+   |
         /                            |   |  /  |    +---------+
    +---+                             | +---+   |
 /x |   |checked-in=V2                | |   |V2 |
    +---+                             | +---+   |       VH24
         \                            |   |  \  | b  +---------+
          \  b  +---+                 |   |   ------>| +---+   |
           ---->|   |checked-in=V8    | +---+   |    | |   |V7 |
                +---+                 | |   |V3 |    | +---+   |
                                      | +---+   |    |   |     |
                                      +---------+    |   |     |
                                                     | +---+   |
                                                     | |   |V8 |
                                                     | +---+   |
                                                     |   |     |
                                                     |   |     |
                                                     | +---+   |
                                                     | |   |V9 |
                                                     | +---+   |
                                                     +---------+
 For any request (e.g., DELETE, MOVE, COPY) that modifies a version-
 controlled binding of a checked-in version-controlled collection, the
 request MUST fail unless the version-controlled collection has a
 DAV:auto-version property that will automatically check out the
 version-controlled collection when it is modified.
 Although a collection version only records the version-controlled
 bindings of a collection, a version-controlled collection MAY contain
 both version-controlled and non-version-controlled bindings.  Non-

Clemm, et al. Standards Track [Page 101] RFC 3253 Versioning Extensions to WebDAV March 2002

 version-controlled bindings are not under version control, and
 therefore can be added or deleted without checking out the version-
 controlled collection.
 Note that a collection version captures only a defined subset of the
 state of a collection.  In particular, a version of a collection
 captures its dead properties and its bindings to version-controlled
 resources, but not its live properties or bindings to non-version-
 controlled resources.
 When a server supports the working-resource feature, a client can
 check out a collection version to create a working collection.
 Unlike a version-controlled collection, which contains bindings to
 version-controlled resources and non-version-controlled resources, a
 working collection contains bindings to version history resources and
 non-version-controlled resources.  In particular, a working
 collection is initialized to contain bindings to the version history
 resources specified by the DAV:version-controlled-binding-set of the
 checked out collection version.  The members of a working collection
 can then be deleted or moved to another working collection.  Non-
 version-controlled resources can be added to a working collection
 with methods such as PUT, COPY, and MKCOL.  When a working collection
 is checked in, a VERSION-CONTROL request is automatically applied to
 every non-version-controlled member of the working collection, and
 each non-version-controlled member is replaced by its newly created
 version history.  The DAV:version-controlled-binding-set of the new
 version resulting from checking in a working collection contains the
 binding name and version history URL for each member of the working
 collection.

14.1 Version-Controlled Collection Properties

 A version-controlled collection has all the properties of a
 collection and of a version-controlled resource.  In addition, the
 version-controlled-collection feature introduces the following
 REQUIRED property for a version-controlled collection.

14.1.1 DAV:eclipsed-set (computed)

 This property identifies the non-version-controlled internal members
 of the collection that currently are eclipsing a version-controlled
 internal member of the collection.
 !ELEMENT eclipsed-set (binding-name*)>
 <!ELEMENT binding-name (#PCDATA)>
 PCDATA value: URL segment

Clemm, et al. Standards Track [Page 102] RFC 3253 Versioning Extensions to WebDAV March 2002

 An UPDATE or MERGE request can give a version-controlled collection a
 version-controlled internal member that has the same name as an
 existing non-version-controlled internal member.  In this case, the
 non-version-controlled internal member takes precedence and is said
 to "eclipse" the new versioned-controlled internal member.  If the
 non-version-controlled internal member is removed (e.g., by a DELETE
 or MOVE), the version-controlled internal member is exposed.

14.2 Collection Version Properties

 A collection version has all the properties of a version.  In
 addition, the version-controlled-collection feature introduces the
 following REQUIRED property for a collection version.

14.2.1 DAV:version-controlled-binding-set (protected)

 This property captures the name and version-history of each version-
 controlled internal member of a collection.
 <!ELEMENT version-controlled-binding-set
  (version-controlled-binding*)>
 <!ELEMENT version-controlled-binding
  (binding-name, version-history)>
 <!ELEMENT binding-name (#PCDATA)>
 PCDATA value: URL segment
 <!ELEMENT version-history (href)>

14.3 Additional OPTIONS Semantics

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

14.4 Additional DELETE Semantics

 Additional Preconditions:
    (DAV:cannot-modify-checked-in-parent): If the request-URL
    identifies a version-controlled resource, the DELETE MUST fail
    when the collection containing the version-controlled resource is
    a checked-in version-controlled collection, unless DAV:auto-
    version semantics will automatically check out the version-
    controlled collection.

Clemm, et al. Standards Track [Page 103] RFC 3253 Versioning Extensions to WebDAV March 2002

14.5 Additional MKCOL 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:
    If the new collection is automatically put under version control,
    all postconditions for VERSION-CONTROL apply to the request.

14.6 Additional COPY Semantics

 Additional Preconditions:
    (DAV:cannot-copy-collection-version): If the source of the request
    is a collection version, the request MUST fail.

14.7 Additional MOVE Semantics

 Additional Preconditions:
    (DAV:cannot-modify-checked-in-parent): If the source of the
    request is a version-controlled resource, the request MUST fail
    when the collection containing the source is a checked-in
    version-controlled collection, unless DAV:auto-version semantics
    will automatically check out that version-controlled collection.
    (DAV:cannot-modify-destination-checked-in-parent): If the source
    of the request is a version-controlled resource, the request MUST
    fail when the collection containing the destination is a checked-
    in version-controlled collection, unless DAV:auto-version
    semantics will automatically check out that version-controlled
    collection.

14.8 Additional VERSION-CONTROL Semantics

 Additional Preconditions:
    (DAV:cannot-modify-checked-in-parent): If the parent of the
    request-URL is a checked-in version-controlled collection, the
    request MUST fail unless DAV:auto-version semantics will
    automatically check out that version-controlled collection.

Clemm, et al. Standards Track [Page 104] RFC 3253 Versioning Extensions to WebDAV March 2002

 Additional Postconditions:
    (DAV:new-version-controlled-collection): If the request body
    identified a collection version, the collection at the request-URL
    MUST contain a version-controlled internal member for each
    DAV:version-controlled-binding specified in the DAV:version-
    controlled-binding-set of the collection version, where the name
    and DAV:version-history of the internal member MUST be the
    DAV:binding-name and the DAV:version-history specified by the
    DAV:version-controlled-binding.  If the internal member is a
    member of a workspace, and there is another member of the
    workspace for the same version history, those two members MUST
    identify the same version-controlled resource; otherwise, a
    VERSION-CONTROL request with a server selected version of the
    version history MUST have been applied to the URL for that
    internal member.

14.9 Additional CHECKOUT Semantics

 Additional Postconditions:
    (DAV:initialize-version-history-bindings): If the request has been
    applied to a collection version, the new working collection MUST
    be initialized to contain a binding to each of the history
    resources identified in the DAV:version-controlled-binding-set of
    that collection version.

14.10 Additional CHECKIN Semantics

 Additional Postconditions:
    (DAV:initialize-version-controlled-bindings): If the request-URL
    identified a version-controlled collection, then the DAV:version-
    controlled-binding-set of the new collection version MUST contain
    a DAV:version-controlled-binding that identifies the binding name
    and version history for each version-controlled binding of the
    version- controlled collection.
    (DAV:version-control-working-collection-members): If the request-
    URL identified a working collection, a VERSION-CONTROL request
    MUST have been automatically applied to every non-version-
    controlled member of the working collection, and each non-
    version-controlled member MUST have been replaced by its newly
    created version history.  If a working collection member was a
    non-version-controlled collection, every member of the non-
    version-controlled collection MUST have been placed under version

Clemm, et al. Standards Track [Page 105] RFC 3253 Versioning Extensions to WebDAV March 2002

    control before the non-version-controlled collection was placed
    under version control.  The DAV:version-controlled-binding-set of
    the new collection version MUST contain a DAV:version-controlled-
    binding that identifies the binding name and the version history
    URL for each member of the working collection.

14.11 Additional UPDATE and MERGE Semantics

 Additional Postconditions:
    (DAV:update-version-controlled-collection-members): If the request
    modified the DAV:checked-in version of a version-controlled
    collection, then the version-controlled members of that version-
    controlled collection MUST have been updated.  In particular:
  1. A version-controlled internal member MUST have been deleted if

its version history is not identified by the DAV:version-

       controlled-binding-set of the new DAV:checked-in version.
    -  A version-controlled internal member for a given version
       history MUST have been renamed if its binding name differs from
       the DAV:binding-name for that version history in the
       DAV:version-controlled-binding-set of the new DAV:checked-in
       version.
    -  A new version-controlled internal member MUST have been created
       when a version history is identified by the DAV:version-
       controlled-binding-set of the DAV:checked-in version, but there
       was no member of the version-controlled collection for that
       version history.  If a new version-controlled member is in a
       workspace that already has a version-controlled resource for
       that version history, then the new version-controlled member
       MUST be just a binding (i.e., another name for) that existing
       version-controlled resource.  Otherwise, the content and dead
       properties of the new version-controlled member MUST have been
       initialized to be those of the version specified for that
       version history by the request.  If no version is specified for
       that version history by the request, the version selected is
       server defined.

15 Internationalization Considerations

 This specification has been designed to be compliant with the IETF
 Policy on Character Sets and Languages [RFC2277].  Specifically,
 where human-readable strings exist in the protocol, either their
 charset is explicitly stated, or XML mechanisms are used to specify
 the charset used.  Additionally, these human-readable strings all
 have the ability to express the natural language of the string.

Clemm, et al. Standards Track [Page 106] RFC 3253 Versioning Extensions to WebDAV March 2002

 Most of the human-readable strings in this protocol appear in
 properties, such as DAV:creator-displayname.  As defined by RFC 2518,
 properties have their values marshaled as XML.  XML has explicit
 provisions for character set tagging and encoding, and requires that
 XML processors read XML elements encoded, at minimum, using the UTF-8
 [RFC2279] encoding of the ISO 10646 multilingual plane.  The charset
 parameter of the Content-Type header, together with the XML
 "encoding" attribute, provide charset identification information for
 MIME and XML processors.  Proper use of the charset header with XML
 is described in RFC 3023.  XML also provides a language tagging
 capability for specifying the language of the contents of a
 particular XML element.  XML uses either IANA registered language
 tags (see RFC 3066) or ISO 639 language tags in the "xml:lang"
 attribute of an XML element to identify the language of its content
 and attributes.
 DeltaV applications, since they build upon WebDAV, are subject to the
 internationalization requirements specified in RFC 2518, Section 16.
 In brief, these requirements mandate the use of XML character set
 tagging, character set encoding, and language tagging capabilities.
 Additionally, they strongly recommend reading RFC 3023 for
 instruction on the use of MIME media types for XML transport and the
 use of the charset header.
 Within this specification, a label is a human-readable string that is
 marshaled in the Label header and as XML in request entity bodies.
 When used in the Label header, the value of the label is URL-escaped
 and encoded using UTF-8.

16 Security Considerations

 All of the security considerations of WebDAV discussed in RFC 2518,
 Section 17 also apply to WebDAV versioning.  Some aspects of the
 versioning protocol help address security risks introduced by WebDAV,
 but other aspects can increase these security risks.  These issues
 are detailed below.

16.1 Auditing and Traceability

 WebDAV increases the ease with which a remote client can modify
 resources on a web site, but this also increases the risk of
 important information being overwritten and lost, either through user
 error or user maliciousness.  The use of WebDAV versioning can help
 address this problem by guaranteeing that previous information is
 saved in the form of immutable versions, and therefore is easily
 available for retrieval or restoration.  In addition, the version
 history provides a log of when changes were made, and by whom.  When
 requests are appropriately authenticated, the history mechanism

Clemm, et al. Standards Track [Page 107] RFC 3253 Versioning Extensions to WebDAV March 2002

 provides a clear audit trail for changes to web resources.  This can
 often significantly improve the ability to identify the source of the
 security problem, and thereby help guard against it in the future.

16.2 Increased Need for Access Control

 WebDAV versioning provides a variety of links between related pieces
 of information.  This can increase the risk that authentication or
 authorization errors allow a client to locate sensitive information.
 For example, if version history is not appropriately protected by
 access control, a client can use the version history of a public
 resource to identify later versions of that resource that the user
 intended to keep private.  This increases the need for reliable
 authentication and accurate authorization.
 A WebDAV versioning client should be designed to handle a mixture of
 200 (OK) and 403 (Forbidden) responses on attempts to access the
 properties and reports that are supported by a resource.  For
 example, a particular user may be authorized to access the content
 and dead properties of a version-controlled resource, but not be
 authorized to access the DAV:checked-in, DAV:checked-out, or
 DAV:version-history properties of that resource.

16.3 Security Through Obscurity

 While it is acknowledged that "obscurity" is not an effective means
 of security, it is often a good technique to keep honest people
 honest.  Within this protocol, version URLs, version history URLs,
 and working resource URLs are generated by the server and can be
 properly obfuscated so as not to draw attention to them.  For
 example, a version of "http://foobar.com/reviews/salaries.html" might
 be assigned a URL such as "http://foobar.com/repo/4934943".

16.4 Denial of Service

 The auto-versioning mechanism provided by WebDAV can result in a
 large number of resources being created on the server, since each
 update to a resource could potentially result in the creation of a
 new version resource.  This increases the risk of a denial of service
 attack that exhausts the storage capability of a server.  This risk
 is especially significant because it can be an unintentional result
 of something like an aggressive auto-save feature provided by an
 editing client.  A server can decrease this risk by using delta
 storage techniques to minimize the cost of additional versions, and
 by limiting auto-versioning to a locking client, and thereby
 decreasing the number of inadvertent version creations.

Clemm, et al. Standards Track [Page 108] RFC 3253 Versioning Extensions to WebDAV March 2002

17 IANA Considerations

 This document uses the namespace defined by RFC 2518 for XML
 elements.  All other IANA considerations from RFC 2518 are also
 applicable to WebDAV Versioning.

18 Intellectual Property

 The following notice is copied from RFC 2026, Section 10.4, and
 describes the position of the IETF concerning intellectual property
 claims made against this document.
 The IETF takes no position regarding the validity or scope of any
 intellectual property or other rights that might be claimed to
 pertain to the implementation or use other technology described in
 this document or the extent to which any license under such rights
 might or might not be available; neither does it represent that it
 has made any effort to identify any such rights.  Information on the
 procedures of the IETF with respect to rights in standards-track and
 standards-related documentation can be found in BCP-11.  Copies of
 claims of rights made available for publication and any assurances of
 licenses to be made available, or the result of an attempt made to
 obtain a general license or permission for the use of such
 proprietary rights by implementers or users of this specification can
 be obtained from the IETF Secretariat.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to practice
 this standard.  Please address the information to the IETF Executive
 Director.

19 Acknowledgements

 This protocol is the collaborative product of the authors and the
 rest of the DeltaV design team: Boris Bokowski, Bruce Cragun
 (Novell), Jim Doubek (Macromedia), David Durand (INSO), Lisa
 Dusseault (Xythos), Chuck Fay (FileNet), Yaron Goland, Mark Hale
 (Interwoven), Henry Harbury (Merant), James Hunt, Jeff McAffer (OTI),
 Peter Raymond (Merant), Juergen Reuter, Edgar Schwarz (Marconi), Eric
 Sedlar (Oracle), Bradley Sergeant, Greg Stein, and John Vasta
 (Rational).  We would like to acknowledge the foundation laid for us
 by the authors of the WebDAV and HTTP protocols upon which this
 protocol is layered, and the invaluable feedback from the WebDAV and
 DeltaV working groups.

Clemm, et al. Standards Track [Page 109] RFC 3253 Versioning Extensions to WebDAV March 2002

20 References

 [ISO639]  ISO, "Code for the representation of names of languages",
           ISO 639:1988, 1998.
 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
           3", BCP 9, RFC 2026, October 1996.
 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
           Languages", BCP 18, RFC 2277, January 1998.
 [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
           RFC 2279, January 1998.
 [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.
 [RFC3023] Murata, M., St.Laurent, S. and D. Kohn, "XML Media Types",
           RFC 3023, January 2001.
 [RFC3066] Alvestrand, H., "Tags for the Identification of Languages",
           BCP 47, RFC 3066, January 2001.

Clemm, et al. Standards Track [Page 110] RFC 3253 Versioning Extensions to WebDAV March 2002

Appendix A - Resource Classification

 This document introduces several different kinds of versioning
 resources, such as version-controlled resources, versions, checked-
 out resources, and version history resources.  As clients discover
 resources on a server, they may find it useful to classify those
 resources (for example, to make UI decisions on choice of icon and
 menu options).
 Clients should classify a resource by examining the values of the
 DAV:supported-method-set (see Section 3.1.3) and DAV:supported-live-
 property-set (see Section 3.1.4) properties of that resource.
 The following list shows the supported live properties and methods
 for each kind of versioning resource.  Where an optional feature
 introduces a new kind of versioning resource, that feature is noted
 in parentheses following the name of that kind of versioning
 resource.  If a live property or method is optional for a kind of
 versioning resource, the feature that introduces that live property
 or method is noted in parentheses following the live property or
 method name.

A.1 DeltaV-Compliant Unmapped URL (a URL that identifies no resource)

 Supported methods:
  1. PUT [RFC2616]
  2. MKCOL [RFC2518]
  3. MKACTIVITY (activity)
  4. VERSION-CONTROL (workspace)
  5. MKWORKSPACE (workspace)

A.2 DeltaV-Compliant Resource

 Supported live properties:
  1. DAV:comment
  2. DAV:creator-displayname
  3. DAV:supported-method-set
  4. DAV:supported-live-property-set
  5. DAV:supported-report-set
  6. all properties defined in WebDAV [RFC2518].

Clemm, et al. Standards Track [Page 111] RFC 3253 Versioning Extensions to WebDAV March 2002

 Supported methods:
  1. REPORT
  2. all methods defined in WebDAV [RFC2518]
  3. all methods defined in HTTP/1.1 [RFC2616].

A.3 DeltaV-Compliant Collection

 Supported live properties:
  1. all DeltaV-compliant resource properties.
 Supported methods:
  1. BASELINE-CONTROL (baseline)
  2. all DeltaV-compliant resource methods.

A.4 Versionable Resource

 Supported live properties:
  1. DAV:workspace (workspace)
  2. DAV:version-controlled-configuration (baseline)
  3. all DeltaV-compliant resource properties.
 Supported methods:
  1. VERSION-CONTROL
  2. all DeltaV-compliant resource methods.

A.5 Version-Controlled Resource

 Supported live properties:
  1. DAV:auto-version
  2. DAV:version-history (version-history)
  3. DAV:workspace (workspace)
  4. DAV:version-controlled-configuration (baseline)
  5. all DeltaV-compliant resource properties.
 Supported methods:
  1. VERSION-CONTROL
  2. MERGE (merge)
  3. all DeltaV-compliant resource methods.

Clemm, et al. Standards Track [Page 112] RFC 3253 Versioning Extensions to WebDAV March 2002

A.6 Version

 Supported live properties:
  1. DAV:predecessor-set
  2. DAV:successor-set
  3. DAV:checkout-set
  4. DAV:version-name
  5. DAV:checkout-fork (in-place-checkout or working resource)
  6. DAV:checkin-fork (in-place-checkout or working resource)
  7. DAV:version-history (version-history)
  8. DAV:label-name-set (label)
  9. DAV:activity-set (activity)
  10. all DeltaV-compliant resource properties.
 Supported methods:
  1. LABEL (label)
  2. CHECKOUT (working-resource)
  3. all DeltaV-compliant resource methods.

A.7 Checked-In Version-Controlled Resource

 Supported live properties:
  1. DAV:checked-in
  2. all version-controlled resource properties.
 Supported methods:
  1. CHECKOUT (checkout-in-place)
  2. UPDATE (update)
  3. all version-controlled resource methods.

A.8 Checked-Out Resource

 Supported live properties:
  1. DAV:checked-out
  2. DAV:predecessor-set
  3. DAV:checkout-fork (in-place-checkout or working resource)
  4. DAV:checkin-fork (in-place-checkout or working resource)
  5. DAV:merge-set (merge)
  6. DAV:auto-merge-set (merge)
  7. DAV:unreserved (activity)
  8. DAV:activity-set (activity)

Clemm, et al. Standards Track [Page 113] RFC 3253 Versioning Extensions to WebDAV March 2002

 Supported methods:
  1. CHECKIN (checkout-in-place or working-resource)
  2. all DeltaV-compliant resource methods.

A.9 Checked-Out Version-Controlled Resource (checkout-in-place)

 Supported live properties:
  1. all version-controlled resource properties.
  2. all checked-out resource properties.
 Supported methods:
  1. UNCHECKOUT
  2. all version-controlled resource methods.
  3. all checked-out resource methods.

A.10 Working Resource (working-resource)

 Supported live properties:
  1. all DeltaV-compliant resource properties
  2. all checked-out resource properties
  3. DAV:auto-update.
 Supported methods:
  1. all checked-out resource methods.

A.11 Version History (version-history)

 Supported live properties:
  1. DAV:version-set
  2. DAV:root-version
  3. all DeltaV-compliant resource properties.
 Supported methods:
  1. all DeltaV-compliant resource methods.

Clemm, et al. Standards Track [Page 114] RFC 3253 Versioning Extensions to WebDAV March 2002

A.12 Workspace (workspace)

 Supported live properties:
  1. DAV:workspace-checkout-set
  2. DAV:baseline-controlled-collection-set (baseline)
  3. DAV:current-activity-set (activity)
  4. all DeltaV-compliant collection properties.
 Supported methods:
  1. all DeltaV-compliant collection methods.

A.13 Activity (activity)

 Supported live properties:
  1. DAV:activity-version-set
  2. DAV:activity-checkout-set
  3. DAV:subactivity-set
  4. DAV:current-workspace-set
  5. all DeltaV-compliant resource properties.
 Supported methods:
  1. all DeltaV-compliant resource methods.

A.14 Version-Controlled Collection (version-controlled-collection)

 Supported live properties:
  1. DAV:eclipsed-set
  2. all version-controlled resource properties.
 Supported methods:
  1. all version-controlled resource methods.

A.15 Collection Version (version-controlled-collection)

 Supported live properties:
  1. DAV:version-controlled-binding-set
  2. all version properties.
 Supported methods:
  1. all version methods.

Clemm, et al. Standards Track [Page 115] RFC 3253 Versioning Extensions to WebDAV March 2002

A.16 Version-Controlled Configuration (baseline)

 Supported live properties:
  1. DAV:baseline-controlled-collection
  2. all version-controlled resource properties.
 Supported methods:
  1. all version-controlled resource methods.

A.17 Baseline (baseline)

 Supported live properties:
  1. DAV:baseline-collection
  2. DAV:subbaseline-set
  3. all version properties.
 Supported methods:
  1. all version methods.

A.18 Checked-Out Version-Controlled Configuration (baseline)

 Supported live properties:
  1. DAV:subbaseline-set
  2. all version-controlled configuration properties.
 Supported methods:
  1. all version-controlled configuration methods.

Clemm, et al. Standards Track [Page 116] RFC 3253 Versioning Extensions to WebDAV March 2002

Authors' Addresses

 Geoffrey Clemm
 Rational Software
 20 Maguire Road, Lexington, MA 02421
 EMail: geoffrey.clemm@rational.com
 Jim Amsden
 IBM
 3039 Cornwallis, Research Triangle Park, NC 27709
 EMail: jamsden@us.ibm.com
 Tim Ellison
 IBM
 Hursley Park, Winchester, UK S021 2JN
 EMail: tim_ellison@uk.ibm.com
 Christopher Kaler
 Microsoft
 One Microsoft Way, Redmond, WA 90852
 EMail: ckaler@microsoft.com
 Jim Whitehead
 UC Santa Cruz, Dept. of Computer Science
 1156 High Street, Santa Cruz, CA 95064
 EMail: ejw@cse.ucsc.edu

Clemm, et al. Standards Track [Page 117] RFC 3253 Versioning Extensions to WebDAV March 2002

Full Copyright Statement

 Copyright (C) The Internet Society (2002).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Clemm, et al. Standards Track [Page 118]

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