INTERNET-DRAFT Geoffrey Clemm, Rational Software
draft-ietf-deltav-versioning-12 Jim Amsden, IBM
Chris Kaler, Microsoft
Jim Whitehead, U.C. Santa Cruz
Expires July 20, 2001 January 20, 2001
Versioning Extensions to WebDAV
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of RFC 2026, Section 10.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This document specifies a set of methods, headers, and resource types
that define the WebDAV 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:
- version history management,
- automatic versioning for versioning-unaware clients,
- workspace management,
- baseline management,
- activity management,
- variant management, and
- URL namespace versioning.
Clemm, et al. [Page 1]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Table of Contents
1 INTRODUCTION...........................................6
1.1 Rationale............................................7
1.2 Relationship to DAV..................................8
1.3 Terms................................................8
1.3.1 Optional Versioning Terms........................10
1.4 Notational Conventions..............................12
1.5 Property Values.....................................13
1.5.1 Initial Property Value...........................13
1.5.2 Protected Property Value.........................13
1.5.3 Computed Property Value..........................13
1.5.4 Property Value Locking...........................13
1.5.5 Boolean Property Value...........................13
1.5.6 String Property Value............................14
1.5.7 DAV:href Property Value..........................14
2 CORE VERSIONING.......................................14
2.1 Core Versioning Semantics...........................14
2.1.1 Creating a Version-Controlled Resource...........14
2.1.2 Modifying a Version-Controlled Resource..........15
2.2 Version-Controlled Resource Properties..............16
2.2.1 DAV:checked-in (protected).......................16
2.2.2 DAV:checked-out (protected)......................17
2.2.3 DAV:predecessor-set..............................17
2.2.4 DAV:precursor-set................................17
2.2.5 DAV:auto-version.................................17
2.3 Version Properties..................................18
2.3.1 DAV:version (protected)..........................18
2.3.2 DAV:predecessor-set (protected)..................18
2.3.3 DAV:successor-set (computed).....................18
2.3.4 DAV:checkout-set (computed)......................18
2.3.5 DAV:version-name (protected).....................18
2.3.6 DAV:precursor-set (protected)....................19
2.4 VERSION-CONTROL Method..............................19
2.4.1 Example - VERSION-CONTROL........................20
2.5 DAV:version-tree REPORT.............................20
2.5.1 Example - DAV:version-tree REPORT................21
2.6 Additional OPTIONS Semantics........................22
2.7 Additional PUT Semantics............................22
2.8 Additional PROPPATCH Semantics......................23
2.9 Additional DELETE Semantics.........................24
2.10 Additional COPY Semantics..........................24
2.11 Additional MOVE Semantics..........................25
2.12 Additional UNLOCK Semantics........................25
3 CHECKOUT OPTION.......................................26
3.1 CHECKOUT Method.....................................26
3.1.1 Example - CHECKOUT of a version-controlled res...27
3.2 CHECKIN Method......................................27
3.2.1 Example - CHECKIN................................28
3.3 UNCHECKOUT Method...................................29
3.3.1 Example - UNCHECKOUT.............................29
Clemm, et al. [Page 2]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
3.4 Additional OPTIONS Semantics........................29
4 UPDATE OPTION.........................................30
4.1 UPDATE Method.......................................30
4.1.1 Example - UPDATE.................................30
4.2 Additional OPTIONS Semantics........................31
5 VERSION-HISTORY OPTION................................31
5.1 Version History Properties..........................31
5.1.1 DAV:version-set (protected)......................31
5.1.2 DAV:root-version (computed)......................32
5.2 Additional Version-Controlled Resource Properties...32
5.2.1 DAV:version-history (computed)...................32
5.3 Additional Version Properties.......................32
5.3.1 DAV:version-history (computed)...................32
5.4 DAV:locate-history REPORT...........................32
5.4.1 Example - DAV:locate-history REPORT..............33
5.5 Additional OPTIONS Semantics........................34
5.6 Additional DELETE Semantics.........................34
5.7 Additional COPY Semantics...........................35
5.8 Additional MOVE Semantics...........................35
5.9 Additional VERSION-CONTROL Semantics................35
5.10 Additional CHECKIN Semantics.......................35
6 WORKING-RESOURCE OPTION...............................35
6.1 Working Resource Properties.........................36
6.2 Additional OPTIONS Semantics........................36
6.3 Additional COPY Semantics...........................36
6.4 Additional MOVE Semantics...........................37
6.5 Additional CHECKOUT Semantics.......................37
6.5.1 Example - CHECKOUT of a version..................37
6.6 Additional CHECKIN Semantics........................38
6.6.1 Example - CHECKIN of a working resource..........38
7 WORKSPACE OPTION......................................38
7.1 Workspace Properties................................39
7.1.1 DAV:workspace-checkout-set (computed)............39
7.2 Additional Resource Properties......................40
7.2.1 DAV:workspace (protected)........................40
7.3 MKWORKSPACE Method..................................40
7.3.1 Example - MKWORKSPACE............................40
7.4 Additional OPTIONS Semantics........................41
7.5 Additional DELETE Semantics.........................42
7.6 Additional MOVE Semantics...........................42
7.7 Additional VERSION-CONTROL Semantics................42
7.7.1 Example - VERSION-CONTROL........................43
8 MERGE OPTION..........................................43
8.1 Additional Version-Controlled Resource Properties...44
8.1.1 DAV:merge-set....................................44
8.1.2 DAV:auto-merge-set...............................44
8.2 MERGE Method........................................44
8.2.1 Example - MERGE..................................47
8.3 DAV:merge-preview REPORT............................48
Clemm, et al. [Page 3]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
8.3.1 Example - DAV:merge-preview REPORT...............49
8.4 Additional OPTIONS Semantics........................50
8.5 Additional DELETE Semantics.........................50
8.6 Additional CHECKIN Semantics........................50
9 LABEL OPTION..........................................50
9.1 Additional Version Properties.......................51
9.1.1 DAV:label-name-set (protected)...................51
9.2 LABEL Method........................................51
9.2.1 Example - Setting a label........................52
9.3 Label Header........................................53
9.4 Additional OPTIONS Semantics........................53
9.5 Additional GET Semantics............................53
9.6 Additional PROPFIND Semantics.......................54
9.7 Additional COPY Semantics...........................54
9.8 Additional CHECKOUT Semantics.......................55
9.9 Additional UPDATE Semantics.........................55
10 BASELINE OPTION.....................................56
10.1 Baseline Selector Properties.......................56
10.1.1 DAV:baseline-controlled-collection (computed)...56
10.1.2 DAV:subbaseline-set.............................57
10.2 Baseline Properties................................57
10.2.1 DAV:baseline-collection (protected).............57
10.2.2 DAV:subbaseline-set (protected).................57
10.3 Additional Collection Properties...................57
10.3.1 DAV:baseline-selector (protected)...............57
10.4 Additional Workspace Properties....................58
10.4.1 DAV:baseline-controlled-collection-set(computed)58
10.5 BASELINE-CONTROL Method............................58
10.5.1 Example - BASELINE-CONTROL......................59
10.6 DAV:baseline-comparison REPORT.....................60
10.6.1 Example - DAV:baseline-comparison REPORT........61
10.7 Additional OPTIONS Semantics.......................62
10.8 Additional MKCOL Semantics.........................62
10.9 Additional COPY Semantics..........................62
10.10 Additional CHECKIN Semantics......................62
10.11 Additional UPDATE Semantics.......................63
10.12 Additional MERGE Semantics........................63
11 ACTIVITY OPTION.....................................64
11.1 Activity Properties................................65
11.1.1 DAV:activity-version-set (computed).............65
11.1.2 DAV:activity-checkout-set (computed)............65
11.1.3 DAV:subactivity-set.............................66
11.1.4 DAV:current-workspace-set (computed)............66
11.2 Additional Version Properties......................66
11.2.1 DAV:activity-set................................66
11.3 Additional Version-Controlled Resource Properties..66
11.3.1 DAV:unreserved..................................66
11.3.2 DAV:activity-set................................67
11.4 Additional Workspace Properties....................67
11.4.1 DAV:current-activity-set........................67
11.5 MKACTIVITY Method..................................67
Clemm, et al. [Page 4]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
11.5.1 Example - MKACTIVITY............................68
11.6 DAV:latest-activity-version REPORT.................68
11.7 Additional OPTIONS Semantics.......................69
11.8 Additional DELETE Semantics........................69
11.9 Additional MOVE Semantics..........................70
11.10 Additional CHECKOUT Semantics.....................70
11.10.1 Example - CHECKOUT with an activity............71
11.11 Additional CHECKIN Semantics......................71
11.12 Additional MERGE Semantics........................72
12 VERSION-CONTROLLED-COLLECTION OPTION................72
12.1 Eclipsed Version-Controlled Bindings...............75
12.2 Working Collections................................75
12.3 Collection Version Properties......................75
12.3.1 DAV:version-controlled-binding-set..............76
12.4 Version-Controlled Collection Properties...........76
12.4.1 DAV:eclipsed-set (computed).....................76
12.5 Additional OPTIONS Semantics.......................76
12.6 Additional DELETE Semantics........................76
12.7 Additional MKCOL Semantics.........................77
12.8 Additional MOVE Semantics..........................77
12.9 Additional VERSION-CONTROL Semantics...............77
12.10 Additional CHECKOUT Semantics.....................77
12.11 Additional CHECKIN Semantics......................78
12.12 Additional UPDATE and MERGE Semantics.............78
13 FORK-CONTROL OPTION.................................79
13.1 Additional Version Properties......................79
13.1.1 DAV:checkout-fork...............................79
13.1.2 DAV:checkin-fork................................79
13.2 Additional Version-Controlled Resource Properties..80
13.2.1 DAV:checkout-fork...............................80
13.2.2 DAV:checkin-fork................................80
13.3 Additional OPTIONS Semantics.......................80
13.4 Additional CHECKOUT Semantics......................80
13.5 Additional CHECKIN Semantics.......................81
14 VARIANT OPTION......................................81
14.1 Variant-Controlled Resource Properties.............82
14.1.1 DAV:variant-set (protected).....................82
14.1.2 DAV:default-variant (protected).................82
14.2 Additional DELETE Semantics........................82
14.3 Additional MOVE Semantics..........................82
14.4 Additional VERSION-CONTROL Semantics...............83
14.5 Additional CHECKIN Semantics.......................83
14.6 Additional UPDATE Semantics........................83
15 INTERNATIONALIZATION CONSIDERATIONS.................84
16 SECURITY CONSIDERATIONS.............................85
17 AUTHENTICATION......................................85
18 IANA CONSIDERATIONS.................................85
Clemm, et al. [Page 5]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
19 INTELLECTUAL PROPERTY...............................85
20 ACKNOWLEDGEMENTS....................................86
21 REFERENCES..........................................86
22 AUTHORS' ADDRESSES..................................87
23 APPENDIX A: CLARIFICATIONS AND EXTENSIONS TO RFC 251887
23.1 Additional Resource Properties.....................87
23.1.1 DAV:comment.....................................87
23.1.2 DAV:creator-displayname.........................88
23.2 Response Bodies for 403 and 409 Status Responses...88
23.2.1 Example - CHECKOUT request with DAV:must-not-be-checked-out
response...............................................88
23.3 Clarification of COPY Semantics with Overwrite:T...89
23.4 REPORT Method......................................89
23.4.1 Example - weather REPORT........................90
23.4.2 Example - REPORT with Depth.....................90
23.5 DAV:expand-property REPORT.........................91
23.5.1 Example - DAV:expand-property...................92
23.6 Additional OPTIONS Semantics.......................93
23.6.1 Example - OPTIONS...............................95
1 INTRODUCTION
This document defines WebDAV Versioning extensions, an application
of HTTP/1.1 for handling resource versioning in a WebDAV
environment. WebDAV Versioning defines both core and optional
versioning functionality. Core versioning allows authors to create
and access distinct versions of a resource, and provides automatic
versioning for versioning-unaware clients. All core versioning
functionality MUST be provided by a server that supports
versioning. An implementer that is only interested in core
versioning should read Section 1 (Introduction), Section 2 (Core
Versioning), and Section 23 (Appendix A: Clarifications and
Extensions to RFC 2518).
Versioning options provide additional capabilities such as
workspace management, baselining, logical change tracking, merging,
and URL namespace versioning. The optional versioning capabilities
provided by a particular server can be discovered with an OPTIONS
request. The versioning options have been designed to be logically
orthogonal, so that a client can easily deal with servers that
support different sets of options. The exception is the working-
resource and workspace options. These provide the same logical
functionality but with significantly different client/server
performance/complexity tradeoffs. It is expected that only a
limited number of servers will support both the working-resource
and the workspace options.
Clemm, et al. [Page 6]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
This document will first define the properties and method semantics
for core versioning, and then define the additional properties and
method semantics for each versioning option.
1.1 Rationale
Versioning, parallel development, and configuration management are
important features for remote authoring of Web content. Version
management is concerned with tracking and accessing the history of
important states of a single Web resource, such as a standalone Web
page. Parallel development provides additional resource
availability in multi-user, distributed environments and lets
authors make changes on the same resource at the same time, and
merge those changes at some later date. Configuration management
addresses the problems of tracking and accessing multiple
interrelated resources over time as sets of resources, not simply
individual resources. Traditionally, artifacts of software
development, including code, design, test cases, requirements, and
help files, have been a focus of configuration management. Web
sites, comprised of 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 benefits of versioning in the context of the worldwide web
include:
- It provides infrastructure for efficient and controlled
management of large evolving web sites. Modern configuration
management systems are built on some form of repository that can
track the version history of individual resources, and provide the
higher-level tools to manage those saved versions. Basic
versioning capabilities are required to support such systems.
- It allows parallel development and update of single resources.
Since versioning systems register change by creating new objects,
they enable simultaneous write access by allowing the creation of
multiple versions. Many also provide merge support to ease the
reverse operation.
- It provides a framework for coordinating changes to resources.
While specifics vary, most systems provide some method of
controlling or tracking access to enable collaborative resource
development.
- It represents the fact that 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.
Clemm, et al. [Page 7]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
- It provides 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.
1.2 Relationship to DAV
To maximize interoperability and the use of existing protocol
functionality, versioning support is designed as extensions to the
WebDAV protocol [RFC2518]. The versioning extensions are designed
to be orthogonal to most aspects of the HTTP and WebDAV protocols,
but certain clarifications and extensions to RFC 2518 are required
for effective interoperable versioning. These clarifications and
extensions are described in Section 23.
1.3 Terms
This document uses the terms defined in RFC 2616 and RFC 2518. In
addition, the following terms are defined.
Core Versioning
"Core versioning" is the set of properties and method semantics
that MUST be supported by all versioning servers.
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.
Version Resource
A "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 content and dead properties of a version MUST NOT
change. The server MUST allocate a distinct new URL for each new
version, and that URL MUST NOT ever identify any resource other
than that version.
Clemm, et al. [Page 8]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Version History Resource
A "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.
Precursor
When a version resource is copied, that version is the "precursor"
of the new resource created at the destination of the copy.
Root Version Resource
The "root version" is the version in a version history that is an
ancestor of every other version in that version history.
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.
Clemm, et al. [Page 9]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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
+---+
1.3.1Optional Versioning Terms
The following additional terms are used to define the versioning
options.
Working Resource
A "working resource" is a modifiable resource that results from
checking out a version. A working resource can be checked in to
create a new version.
Workspace Resource
A "workspace" is a collection whose members are both version-
controlled and non-version-controlled resources. A workspace MUST
NOT contain two different version-controlled resources for the same
version history.
Clemm, et al. [Page 10]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
Collection Resource
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).
Version-Controlled Collection Resource
A "version-controlled collection" is a collection that is under
version control.
Collection Version Resource
A "collection version" captures the content, dead properties, and
version-controlled bindings of a version-controlled collection. A
version-controlled binding is a binding to a version-controlled
resource.
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. A Depth:infinity request effectively applies to the
configuration whose root collection is identified by the request-
URL. Note that in a versioning context, a collection (which is a
single resource) is very different from a configuration (which is a
set of resources).
Baseline Resource
A "baseline" of a collection is a version of the configuration that
is rooted at that collection. 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 Resource
A "baseline-controlled collection" is a collection from which
baselines can be created.
Clemm, et al. [Page 11]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Baseline Selector Resource
A "baseline selector" 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.
When a collection is both version-controlled and baseline-
controlled, a client can create a new version of the collection by
checking in and checking out that collection, while it can create a
new baseline of that collection by checking in and checking out the
baseline selector of that collection.
Activity Resource
An "activity" is a non-versionable 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.
Variant Resource
A "variant" is a special kind of version-controlled resource whose
name is allocated by the server.
Variant-Controlled Resource
A "variant-controlled resource" is a special kind of version-
controlled resource that maintains a set of variants. Each variant
of a variant-controlled resource selects a version from the version
history of that variant-controlled resource.
1.4 Notational Conventions
The augmented BNF used by this document to describe protocol
elements is defined in RFC 2068, Section 2.1. Because this
augmented BNF uses the basic production rules provided in RFC 2068,
Section 2.2, those rules apply to this document as well.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC 2119.
The term "protected" is placed in parentheses following the
definition of a protected property (see section 1.5.2).
The term "computed" is placed in parentheses following the
definition of a computed property (see section 1.5.3).
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 precondition or postcondition of a method is defined in this
document, it can be prefixed by a parenthesized XML element type.
Clemm, et al. [Page 12]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
If a precondition is violated by a request or a postcondition
cannot be satisfied, the XML element of the violated precondition
or unsatisfied postcondition will be returned in the response body
(see Section 23.2).
1.5 Property Values
1.5.1Initial 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.
1.5.2Protected 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.
1.5.3Computed 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.
1.5.4Property Value Locking
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.
1.5.5Boolean Property Value
Some properties take a Boolean value of either "false" or "true".
Clemm, et al. [Page 13]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
1.5.6String Property Value
A string is a sequence of characters. When a string is marshaled
in the header of an HTTP request, the characters are encoded using
the UTF-8 encoding scheme.
1.5.7DAV:href Property Value
The DAV:href XML element is defined in RFC 2518, Section 12.3.
2 CORE VERSIONING
Core versioning defines extensions to existing HTTP and WebDAV
methods, as well as new resource types, new live properties and new
methods. A server indicates that it supports core versioning by
including the string "version-control" as a field in the DAV header
in the response to an OPTIONS request. All methods, properties,
and behavior defined in core versioning MUST be supported by a
versioning server.
2.1 Core Versioning Semantics
2.1.1Creating a Version-Controlled Resource
In order to track the history of the content and dead properties of
a versionable resource, an author can put the resource under
version control with a VERSION-CONTROL request. This creates a new
version history resource and creates a version in this version
history whose content and dead properties are a copy of the current
content and dead properties of the resource. The DAV:checked-in
property of the version-controlled resource is then set to identify
this version. In core versioning, a version is exposed as an HTTP
resource with a server-defined URL, but a version history is
exposed as an HTTP resource only when the server supports the
version-history option (see Section 5).
Note that a version-controlled resource and the current
DAV:checked-in version of that version-controlled resource are two
distinct resources, with their own content and properties. When a
method is applied to a version-controlled resource, it is applied
to that version-controlled resource and not to the DAV:checked-in
version 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.
Clemm, et al. [Page 14]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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
new version resource is identified by the DAV:checked-in property
of the resource that is now under version control. 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 history
| +----+
| |
/foo.html | /foo.html |
| |
+----+ | +----+ checked-in +----+
| S1 | | | S1 | ---------- | S1 | version
+----+ | +----+ +----+
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.
2.1.2Modifying 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 version history of that version-controlled resource. The
version that was checked out is remembered as the predecessor of
the new version.
A PUT or PROPPATCH to a version-controlled resource with the
DAV:auto-version property set will automatically check out that
resource prior to executing the PUT or PROPPATCH. If that resource
is write-locked, the resource remains checked-out until the
resource is unlocked, at which time the resource is checked in and
a new version is created in the version history of that resource.
If the resource is not write-locked, the resource is automatically
checked in and a new version is created immediately after each
successful PUT or PROPPATCH.
This means that if /foo.html is a write-locked auto-versioned
resource, a successful PUT to /foo.html (i.e. one by an authorized
client with the appropriate lock-token) will automatically check it
out, and it will remain checked out for the duration of the lock.
Clemm, et al. [Page 15]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
When the lock is removed (for any reason, including a lock
timeout), /foo.html will automatically be checked in and a new
version in the version history of /foo.html will be created. If
/foo.html is not write-locked, a PUT to /foo.html will not only
automatically check it out and update it, but will also
automatically check it back in. This allows clients that are not
aware of versioning semantics to continue to function normally.
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
| | | +----+
2.2 Version-Controlled Resource Properties
WebDAV versioning introduces the following properties for a
version-controlled resource.
2.2.1DAV:checked-in (protected)
This property appears on a checked-in version-controlled resource,
and identifies a version that has the same content and dead
Clemm, et al. [Page 16]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
2.2.2DAV:checked-out (protected)
This property appears on a checked-out version-controlled resource,
and identifies the DAV:checked-in version at the time the resource
was checked out.
2.2.3DAV:predecessor-set
This property appears on a checked-out version-controlled resource,
and 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.
2.2.4DAV:precursor-set
This property appears on a checked-out version-controlled resource,
and determines the DAV:precursor-set property of the version that
results from checking in this resource.
2.2.5DAV:auto-version
When the DAV:auto-version property of a non-write-locked checked-in
version-controlled resource contains DAV:when-unlocked, a
modification request (such as PUT/PROPPATCH) is automatically
preceded by a checkout operation and automatically followed by a
checkin operation.
When the DAV:auto-version property of a write-locked checked-in
version-controlled resource contains DAV:when-locked, a
modification request is automatically preceded by a checkout
operation, and an automatic checkin operation is applied when the
write lock is removed.
A server MAY refuse to allow the value of the DAV:auto-version
property to be modified.
ANY value: A sequence of elements with at most one DAV:when-
unlocked element and at most one DAV:when-locked element.
Clemm, et al. [Page 17]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
2.3 Version Properties
WebDAV versioning introduces the following properties for a
version.
2.3.1DAV:version (protected)
This property contains a server-defined URL that identifies this
version. This URL MUST NOT have previously identified any other
resource, and MUST NOT ever identify a resource other than this
version.
2.3.2DAV: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.
2.3.3DAV:successor-set (computed)
This property identifies each version whose DAV:predecessor-set
identifies this version.
2.3.4DAV:checkout-set (computed)
This property identifies each checked-out resource whose
DAV:checked-out property identifies this version.
2.3.5DAV: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 to a user, unlike the URL of a version, which
is normally only used by a client and not displayed to a user.
PCDATA value: string
Clemm, et al. [Page 18]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
2.3.6DAV:precursor-set (protected)
This property identifies each version from a different version
history that was copied or merged into the checked-out resource
that created this version.
2.4 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 those of 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
request is ignored. 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 response body is included, it MUST be a DAV:version-control
XML element.
ANY value: A sequence of elements with at most one DAV:already-
version-controlled element.
The response MUST include a Cache-Control:no-cache header.
Postconditions:
(DAV:put-under-version-control): If the request-URL identified a
versionable resource at the time of the request, a new version
history is created and a new version resource is created in the new
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
Clemm, et al. [Page 19]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
by the same server, on the same host maintained by a different
server, or on a different host maintained by a different server.
(DAV:already-under-version-control): If the request-URL identified
a resource already under version control at the time of the
request, the VERSION-CONTROL request MUST NOT change the state of
that version-controlled resource, and the DAV:checkout-response
body MUST contain a DAV:already-version-controlled element.
2.4.1Example - VERSION-CONTROL
>>REQUEST
VERSION-CONTROL /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, /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.
2.5 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.
Marshalling:
The DAV:version-tree REPORT request body MUST be a DAV:version-tree
XML element.
ANY value: a sequence of zero or more elements, with at most one
DAV:prop element.
prop: see RFC 2518, Section 12.11
The DAV:version-tree REPORT response body MUST be a DAV:multistatus
XML element.
multistatus: see RFC 2518, Section 12.9
Clemm, et al. [Page 20]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
The response body MUST contain a DAV:response element for each
version in the version history of the version identified by the
request-URL.
2.5.1Example - 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
>>RESPONSE
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
http://repo.webdav.org/his/23/ver/V1
V1
Fred
Clemm, et al. [Page 21]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
http://repo.webdav.org/his/23/ver/V2
http://repo.webdav.org/his/23/ver/V2.1.1
HTTP/1.1 200 OK
http://repo.webdav.org/his/23/ver/V2
V2
Fred
HTTP/1.1 200 OK
http://repo.webdav.org/his/23/ver/V2.1.1
V2.1.1
Sally
HTTP/1.1 200 OK
2.6 Additional OPTIONS Semantics
If the server supports versioning, 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.
2.7 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 PUT MUST
fail unless DAV:auto-version is set for that resource.
(DAV:cannot-modify-version): If the request-URL identifies a
version, the PUT MUST fail.
Clemm, et al. [Page 22]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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-when-locked): If the resource was a write-
locked, checked-in, version-controlled resource whose DAV:auto-
version property was DAV:when-locked, then the resource MUST have
been automatically checked out 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 be empty, 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-version-when-unlocked): If the resource was a non-write-
locked, checked-in, version-controlled resource whose DAV:auto-
version property was DAV:when-unlocked, then the resource MUST have
been automatically checked out prior to executing the request and
automatically checked 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.
2.8 Additional PROPPATCH Semantics
Additional Preconditions:
(DAV:cannot-modify-version-controlled-property): If the request-URL
identifies a checked-in version-controlled resource, an attempt to
modify a dead property MUST fail unless DAV:auto-version is set for
that version-controlled resource.
(DAV:cannot-modify-version): If the request-URL identifies a
version, an attempt to modify a dead property MUST fail.
(DAV:cannot-modify-protected-property): An attempt to use PROPPATCH
to modify a property (either core or optional) defined by this
document as being protected for that kind of resource MUST fail.
Clemm, et al. [Page 23]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
(DAV:cannot-modify-unsupported-property): An attempt to modify a
property defined by this document (either core or optional) 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-when-locked): Same semantics as PUT (see section
2.7).
(DAV:auto-version-when-unlocked): Same semantics as PUT (see
section 2.7).
2.9 Additional DELETE Semantics
Additional Preconditions:
(DAV:cannot-delete-root-version): The root version of a version
history MUST NOT be deleted.
(DAV:cannot-delete-referenced-version): A version that is
identified in a DAV:checked-in or DAV:checked-out property MUST NOT
be deleted.
(DAV:no-version-delete): An implementation MAY fail an attempt to
DELETE a version.
Additional Postconditions:
(DAV:update-predecessor-set): If a version is deleted, any
reference to that version in a DAV:predecessor-set MUST be replaced
by a copy of the DAV:predecessor-set of the deleted version.
2.10Additional 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:initialize-precursor): If the source of the COPY was a version
and if the destination of the COPY supports the DAV:precursor-set
property, the DAV:precursor-set of the destination MUST identify
that version. If the source of the COPY was a version-controlled
resource, the DAV:precursor-set MUST identify the DAV:checked-in or
DAV:checked-out version of that resource.
Clemm, et al. [Page 24]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
(DAV:auto-checkout-when-locked): If the destination is a version-
controlled resource, same semantics as PUT (see section 2.7).
(DAV:auto-version-when-unlocked): If the destination is a version-
controlled resource, same semantics as PUT (see section 2.7).
The result of copying a version-controlled resource or a version 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, and all postconditions for VERSION-CONTROL
apply to the request.
2.11Additional MOVE Semantics
Additional Preconditions:
(DAV:cannot-rename-resource): If the request-URL identifies a
version, the request MUST fail.
Additional Postconditions:
(DAV:preserve-history): When the request-URL identifies a version-
controlled resource, its DAV:checked-in and DAV:checked-out
properties MUST be the same before and after the request.
2.12Additional UNLOCK Semantics
Additional Preconditions:
(DAV:version-history-is-tree): If the request-URL identifies a
version-controlled resource that was automatically checked out
because DAV:auto-version was DAV:when-locked, 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:create-version): If the request-URL identified a version-
controlled resource that was automatically checked out because
DAV:auto-version was DAV:when-locked, a new version MUST have been
created in the version history of the DAV:checked-out version. The
content, dead properties, DAV:resourcetype, and DAV:predecessor-set
of the new version MUST be those of 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 version history of that version. The DAV:version
of the new version MUST be set to a new server-allocated URL that
MUST NOT have previously identified any other resource, and MUST
NOT ever identify a resource other than this version. The
Clemm, et al. [Page 25]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
3 CHECKOUT OPTION
In core versioning, 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 option provides an alternative mechanism that avoids the
complexity of the locking protocol. In particular, it does not
require the client to maintain any local state (such as a lock
token). Instead, a CHECKOUT method is provided for checking out a
version-controlled resource, a CHECKIN method is provided for
creating a new version by checking in a checked-out resource, and
an UNCHECKOUT method is provided for canceling a checkout and
returning the version-controlled resource to its state before the
checkout.
Although the CHECKOUT method provides some value as it is defined
by the checkout option, the major value of this method is in its
extended semantics defined by other options. For example, the
working-resource option (see Section 6) and the workspace option
(see Section 7) use CHECKOUT to allow parallel development of a
single resource, the activity option (see Section 11) uses CHECKOUT
to track a logical change that affects several resources, and the
variant option (see Section 14) uses CHECKOUT to add new variants
to a resource.
3.1 CHECKOUT Method
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.
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 value.
Clemm, et al. [Page 26]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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 value.
(DAV:initialize-predecessor-set): The DAV:predecessor-set property
of the checked-out resource MUST be initialized to be the
DAV:checked-out version.
3.1.1Example - 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.
3.2 CHECKIN Method
A CHECKIN request can be applied to a checked-out version-
controlled resource to produce a new version whose content and dead
properties are those of the checked-out resource.
If a CHECKIN request fails, the server state preceding the request
MUST be restored.
Marshalling:
If a request body is included, it MUST be a DAV:checkin XML
element.
ANY value: A sequence of elements with at most one DAV:keep-
checked-out element.
The response MUST include a Location header.
The response MUST include a Cache-Control:no-cache header.
Clemm, et al. [Page 27]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
Postconditions:
(DAV:create-version): A new version MUST have been created in the
version history of the DAV:checked-out 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 those of 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 version history of that version. The DAV:version
of the new version MUST be set to a new server-allocated URL that
MUST NOT have previously identified any other resource, and MUST
NOT ever identify a resource other than this version.
(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 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.
3.2.1Example - 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.
Clemm, et al. [Page 28]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
3.3 UNCHECKOUT Method
An UNCHECKOUT request can be applied to a checked-out version-
controlled resource to cancel the CHECKOUT.
If an UNCHECKOUT request fails, the server state preceding the
request MUST be restored.
Marshalling:
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 no longer is set.
(DAV:restore-content-and-dead-properties): The content and dead
properties of the version-controlled resource are those of its
DAV:checked-in version.
3.3.1Example - 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.
3.4 Additional OPTIONS Semantics
If a server supports the checkout option, it MUST include
"checkout" 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. [Page 29]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
4 UPDATE OPTION
The update option provides a mechanism for restoring a previous
state of the version-controlled resource.
4.1 UPDATE Method
The UPDATE method modifies the content and dead properties of a
checked-in version-controlled resource to be those of a specified
version from the version history of that version-controlled
resource.
Marshalling:
The request-URL MUST identify the resource to be updated.
The request body MUST be a DAV:update element.
ANY value: A sequence of elements with at most one DAV:version
element.
The response MUST include a Cache-Control:no-cache header.
Preconditions:
(DAV:must-be-checked-in-version-controlled-resource): The request-
URL MUST identify a checked-in version-controlled resource.
(DAV:must-select-version-in-same-history): The DAV:version element
in the request body MUST identify a version in the same version
history as the DAV:checked-in version of the version-controlled
resource identified by the request-URL.
Postconditions:
(DAV:update-content-and-dead-properties): The content and dead
properties of the version-controlled resource MUST be the same as
those of the version specified by the DAV:version element in the
request body.
(DAV:update-checked-in-property): The DAV:checked-in property of
the version-controlled resource MUST contain the value of the
DAV:version element in the request body.
4.1.1Example - UPDATE
>>REQUEST
UPDATE /foo.html HTTP/1.1
Host: www.webdav.org
Clemm, et al. [Page 30]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Content-type: text/xml; charset="utf-8"
Content-Length: xxxx
http://repo.webdav.org/his/23/ver/33
>>RESPONSE
HTTP/1.1 200 OK
Cache-Control: no-cache
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.
4.2 Additional OPTIONS Semantics
If the server supports the update option, 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.
5 VERSION-HISTORY OPTION
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 exists in a
server defined namespace and therefore is unaffected by any
deletion or movement of version-controlled resources.
5.1 Version History Properties
The DAV:resourcetype of a version history MUST be DAV:version-
history.
The version-history option introduces the following properties for
a version history.
5.1.1DAV:version-set (protected)
This property identifies each version of this version history.
Clemm, et al. [Page 31]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
5.1.2DAV:root-version (computed)
This property identifies the root version of this version history.
5.2 Additional Version-Controlled Resource Properties
The version-history option introduces the following properties for
a version-controlled resource.
5.2.1DAV: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.
5.3 Additional Version Properties
The version-history option introduces the following properties for
a version.
5.3.1DAV:version-history (computed)
This property identifies the version history that contains this
version.
5.4 DAV:locate-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-
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 DAV:locate-history REPORT request body MUST be a DAV:locate-
history XML element.
prop: see RFC 2518, Section 12.11
The DAV:locate-history REPORT response body MUST be a
DAV:multistatus XML element containing every version-controlled
resource that is a member of the collection identified by the
Clemm, et al. [Page 32]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
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.
5.4.1Example - DAV:locate-history REPORT
>>REQUEST
REPORT /ws/public HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
http://repo.webdav.org/his/23
http://repo.webdav.org/his/84
http://repo.webdav.org/his/129
>>RESPONSE
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
http://www.webdav.org/ws/public/x/test.html
http://repo.webdav.org/his/23
HTTP/1.1 200 OK
Clemm, et al. [Page 33]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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 option, 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.
The DAV:version-history-collection-set identifies collections that
may contain version history resources. A version history
collection MAY be the root collection of a tree of collections, all
of which may contain version history resources. 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 collections identified in the
DAV:version-history-collection-set MAY be located on different
hosts from the resource.
Additional Marshalling:
If a request body is included, it MUST be a DAV:options XML
element.
ANY value: A sequence of elements with at most one DAV:version-
history-collection-set element.
If a response body is included, it MUST be a DAV:options-response
XML element.
ANY value: A sequence of elements with at most one DAV:version-
history-collection-set element.
If a DAV:version-history-collection-set element is included in the
request body, the response body MUST contain a DAV:version-history-
collection-set element identifying which collections may contain
version history resources.
5.6 Additional DELETE Semantics
Additional Postconditions:
Clemm, et al. [Page 34]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
(DAV:delete-version-set): If a version history is deleted, all
versions in the DAV:version-set of that version history MUST be
deleted.
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-resource): 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 resulted in the creation
of a new version history, the server MUST allocate 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.
5.10Additional 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 WORKING-RESOURCE OPTION
In order to allow two users to work concurrently on making changes
to the same resource, it is necessary to provide multiple checked
out resources for the same version history. Even if only one user
is making changes to a resource, it is sometimes desirable to be
able to make those changes (new versions) "in private" and then
expose that work at an appropriate later time. One way to provide
this functionality depends on maintaining the desired configuration
of resources in persistent state on the client (usually a copy of
Clemm, et al. [Page 35]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
the content and dead properties of each resource in the
configuration, but minimally a URL list). This is the working-
resource option defined in this section. The other way to provide
this functionality maintains the configuration on the server. This
is the workspace option defined in Section 7.
6.1 Working Resource Properties
A "working resource" is a 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. If
a working resource is deleted before being checked in, this
effectively cancels the CHECKOUT request that created the working
resource.
A working resource has all the properties of a checked-out version-
controlled resource. In particular, it has a DAV:checked-out,
DAV:predecessor-set, DAV:precursor-set, and DAV:auto-version
property. If the version-history option is supported, it has a
DAV:version-history property. If the workspace option is
supported, it can have a DAV:workspace property. If the merge
option is supported, it can have a DAV:merge-set and DAV:auto-
merge-set property. If the baseline option is supported and the
working resource resulted from checking out a baseline, it can have
a DAV:subbaseline-set property. If the activity option is
supported, it can have a DAV:unreserved and DAV:activity-set
property. If the fork-control option is supported, it can have a
DAV:checkout-fork and DAV:checkin-fork property.
6.2 Additional OPTIONS Semantics
If the server supports the working-resource option, 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.
6.3 Additional COPY Semantics
Additional Postconditions:
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.
Clemm, et al. [Page 36]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
6.4 Additional MOVE Semantics
Additional Preconditions:
(DAV:cannot-rename-resource): If the request-URL identifies a
working resource, the request MUST fail.
6.5 Additional CHECKOUT Semantics
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.
Additional Marshalling:
ANY value: A sequence of elements with at most one DAV:apply-to-
version element.
The response MAY include a Location header.
Additional 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 the
same as the content and dead properties of the DAV:checked-out
version.
(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.
6.5.1Example - CHECKOUT of a version
>>REQUEST
CHECKOUT /his/12/ver/V3 HTTP/1.1
Host: repo.webdav.org
Content-Type: text/xml; charset="utf-8"
Content-Length: 0
>>RESPONSE
Clemm, et al. [Page 37]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
6.6 Additional CHECKIN Semantics
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. Note that checking in a working resource
does not change the content or dead properties of any version-
controlled resource, therefore an UPDATE or MERGE request must be
used to update a version-controlled resource with the content and
dead properties of a version created by checking in a working
resource.
Additional Postconditions:
(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.
6.6.1Example - 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
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.
7 WORKSPACE OPTION
The workspace option introduces a "workspace resource". A
workspace resource is a collection whose members are related
version-controlled and non-version-controlled resources. In order
to concurrently expose different versions and configurations of a
set of version-controlled resources, multiple workspaces may be
used. In order to make a change made to a version-controlled
resource in one workspace visible in another workspace, that
Clemm, et al. [Page 38]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
The workspace option provides an alternative to the working-
resource option for supporting parallel development. Unlike the
working-resource option, where the desired configuration of
versions and checked-out resources is maintained on the client, the
workspace option maintains the configuration on the server. This
allows a user to access the configuration from clients in different
physical locations, such as from another office, from home, or
while traveling. Sometimes it is even desirable to provide shared
access to the configuration for several closely cooperating users
(using WebDAV locking to avoid overwrite problems).
Another benefit of the workspace option is that it isolates clients
from a logical change that involves renaming shared resources,
until that logical change is complete and tested. When all clients
use a common set of shared version-controlled resources, every
client sees the result of a MOVE as soon as it occurs.
In order to ensure unambiguous merging (see Section 8) and
baselining (see Section 10) 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. Alternatively, collections in the workspace can be
placed under baseline control, and then initialized by existing
baselines.
7.1 Workspace Properties
The workspace option introduces the following properties for a
workspace.
7.1.1DAV:workspace-checkout-set (computed)
This property identifies each checked-out resource whose
DAV:workspace property identifies this workspace.
Clemm, et al. [Page 39]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
7.2 Additional Resource Properties
The workspace option introduces the following properties for a
WebDAV resource.
7.2.1DAV:workspace (protected)
If the resource is associated with a workspace, this property
identifies this workspace.
The DAV:workspace property of a workspace MUST identify that
workspace. The DAV:workspace property of any other type of
resource MUST be the same as the DAV:workspace of its parent
collection.
7.3 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.
If a MKWORKSPACE request fails, the server state preceding the
request MUST be restored.
Marshalling:
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.
7.3.1Example - MKWORKSPACE
>>REQUEST
MKWORKSPACE /ws/public HTTP/1.1
Host: www.webdav.org
Clemm, et al. [Page 40]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
7.4 Additional OPTIONS Semantics
If a server supports the workspace option, 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 option, it MUST also support the
checkout option and the version-history option.
Often a versioning implementation constrains where a workspace can
be located in the URL space. The DAV:workspace-collection-set
identifies collections that may contain workspaces. A workspace
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 collections identified by the DAV:workspace-
collection-set MAY be located on different hosts from the resource.
Additional Marshalling:
If a request body is included, it MUST be a DAV:options XML
element.
ANY value: A sequence of elements with at most one DAV:workspace-
collection-set element.
If a response body is included, it MUST be a DAV:options-response
XML element.
ANY value: A sequence of elements with at most one DAV:workspace-
collection-set element.
If DAV:workspace-collection-set is included in the request body,
the response body MUST contain a DAV:workspace-collection-set
element identifying which collections may contain workspaces.
Clemm, et al. [Page 41]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
7.5 Additional DELETE Semantics
Additional Postconditions:
(DAV:delete-workspace-members): If a workspace is deleted, any
resource that identifies that workspace in is DAV:workspace
property MUST be deleted.
7.6 Additional MOVE Semantics
Additional Postconditions:
(DAV:workspace-member-moved): The DAV:workspace of the destination
MUST be updated to have the same value as the DAV:workspace of the
parent collection of the destination.
(DAV:workspace-moved): If the request-URL identifies a workspace,
any reference to that workspace in a DAV:workspace property MUST be
updated to refer to the new location of that workspace.
7.7 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:
ANY value: A sequence of elements with at most one DAV:version
element.
Additional Preconditions:
(DAV:cannot-add-to-existing-history): If the request-URL identifies
a versionable resource or a version-controlled resource, the
DAV:version-control request body element MUST NOT contain a
DAV:version element.
(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. [Page 42]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Additional Postconditions:
(DAV:new-version-controlled-resource): If the request-URL
identified a null 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.
7.7.1Example - 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
http://repo.webdav.org/his/12/ver/V3
>>RESPONSE
HTTP/1.1 201 Created
Cache-Control: no-cache
In this example, the null resource /ws/public/bar.html is put under
version control, and 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.
8 MERGE OPTION
When an author wants to accept the changes (new versions) created
by someone else, it is important not to just update the version-
controlled resources in the author's workspace with those new
versions, since this could result in "backing out" changes the
author has made to those version-controlled resources. Instead,
the versions created in another workspace should be "merged" into
the author's version-controlled resources.
The version history of a version-controlled resource provides the
information needed to determine what should be 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
Clemm, et al. [Page 43]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
those versions. The MERGE request can be used to check out each
version-controlled resource with such a conflict, and set the
DAV:merge-set property of each checked-out resource to identify the
version to be merged. The author 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 author is responsible for
verifying that the automatic merge is correct.
8.1 Additional Version-Controlled Resource Properties
The merge option introduces the following properties for a version-
controlled resource.
8.1.1DAV:merge-set
This property of a checked-out version-controlled resource
identifies each version that is to be merged into this version-
controlled resource.
8.1.2DAV:auto-merge-set
This property of a checked-out version-controlled resource
identifies each version that the server has merged into this
version-controlled 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
version-controlled resource.
8.2 MERGE Method
The MERGE method performs a logical merge of a specified version
into a specified version-controlled resource. If the specified
version is neither an ancestor nor a descendant of the DAV:checked-
in or DAV:checked-out version of the version-controlled resource,
the MERGE checks out the version-controlled resource (if it is not
already checked out) and adds the URL of the specified version to
the DAV:merge-set of the version-controlled resource. It is then
the client's responsibility to update the content and dead
properties of the checked-out version-controlled resource so that
it reflects the logical merge of the specified version into the
current state of the version-controlled resource. The client
indicates that it has completed the update of the version-
Clemm, et al. [Page 44]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
controlled resource, by deleting the version URL from the
DAV:merge-set of the checked-out version-controlled resource, 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 version-controlled resource to reflect
the logical merge of the specified version, it may do so unless
DAV:no-auto-merge is specified in the MERGE request body. In order
to notify the client that a version has been automatically merged,
the MERGE request MUST add the URL of the auto-merged version to
the DAV:auto-merge-set property of the version-controlled resource,
and not to the DAV:merge-set property. The client indicates that
it has verified that the auto-merge is valid, by deleting the
version URL from the DAV:auto-merge-set, and adding it to the
DAV:predecessor-set.
In general, a MERGE request identifies a "merge source" that
specifies a set of versions (the "merge versions") and a "merge
destination" that specifies a set of version-controlled resources
(the "merge targets"). The set of merge versions is determined as
follows:
- If the merge source is a version, that version is the merge
version.
- If the merge source is a version-controlled resource, the
DAV:checked-in version of that version-controlled resource is the
merge version.
- If the merge source is a collection, the DAV:checked-in version
of each version-controlled resource in that collection (as well as
the DAV:checked-in version of the collection if it is version-
controlled) is a merge version.
For each merge version, the server determines the "merge target"
for that merge version. The merge target is the member of the
merge destination that is a version-controlled resource whose
DAV:checked-in or DAV:checked-out version is from the same version
history as the merge version. If a merge version has no merge
target, that merge version is reported by the MERGE as having been
ignored.
Marshalling:
The merge destination is identified by the request-URL.
The merge source is identified by the DAV:source element in the
request body.
The request body MUST be a DAV:merge element.
Clemm, et al. [Page 45]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
prop: see RFC 2518, Section 12.11
The response body MUST contain a DAV:merge-response element.
ANY value: A sequence of elements with at most one DAV:updated-set
element, at most one DAV:merged-set element, and at most one
DAV:ignored-set element.
response: see RFC 2518, Section 12.9.1
The response MUST include a Cache-Control:no-cache header.
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.
The checkouts performed to resolve conflicts MUST NOT violate any
of the pre-conditions of the CHECKOUT operation.
(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.
Postconditions:
(DAV:ancestor-version): If the merge target is a version-controlled
resource whose DAV:checked-in version or DAV:checked-out version is
a descendant of the merge version, 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 version, an UPDATE request MUST have been
applied to the merge target to set its content and dead properties
to be those of the merge version, and the merge target MUST appear
in the DAV:updated-set XML element in the response body. 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 version, the merge version
Clemm, et al. [Page 46]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
MUST have been added to the DAV:auto-merge-set of the merge target,
and the merge target MUST appear in the DAV:merged-set.
(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 version, 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:checkin XML element MUST have been used as arguments to the
CHECKOUT request.
(DAV:update-merge-set): If the merge target was checked out by the
MERGE (or was already checked out before the MERGE), and if the
DAV:checked-out version of the merge target is not a descendant of
the merge version, the merge version MUST be added to either the
DAV:merge-set or the DAV:auto-merge-set of the merge target, and
the merge target MUST appear in the DAV:merged-set element in the
response body. If a merge version 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 version and the merge target. If a merge
version 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 version MUST NOT have been added to the DAV:auto-merge-set.
(DAV:report-ignored-set): If a merge version has no merge target, a
URL for the merge version MUST appear in the DAV:ignored-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 DAV:updated-set and
DAV:merged-set.
8.2.1Example - MERGE
>>REQUEST
MERGE /ws/public HTTP/1.1
Host: www.webdav.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxxx
http://www.webdav.org/ws/dev/sally
>>RESPONSE
HTTP/1.1 200 OK
Clemm, et al. [Page 47]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Cache-Control: no-cache
http://www.webdav.org/ws/public/src/parse.c
http://www.webdav.org/ws/public/doc/parse.html
http://repo.webdav.org/his/23/ver/42
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. Two resources in the workspace
were updated, and one version was ignored.
8.3 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 merged into the resource identified by the request-URL
(commonly, a collection).
Marshalling:
The DAV:merge-preview REPORT request body MUST be a DAV:merge-
preview XML element.
The DAV:merge-preview REPORT response body MUST be a DAV:merge-
preview-response XML element.
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 version for that merge target.
Clemm, et al. [Page 48]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
A DAV:conflict element identifies a merge target that requires a
merge.
A DAV:common-ancestor element identifies the version that is a
common ancestor of both the merge version and the DAV:checked-in or
DAV:checked-out version of the merge target.
A DAV:ignored-preview element identifies a version that has no
merge target and therefore would be ignored by the merge.
8.3.1Example - 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
http://www.webdav.org/ws/dev/fred
>>RESPONSE
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
http://www.webdav.org/ws/public/foo.html
http://repo.webdav.org/his/23/ver/18
http://repo.webdav.org/his/23/ver/42
Clemm, et al. [Page 49]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
http://www.webdav.org/ws/public/bar.html
http://www.repo/his/42/ver/3
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.
8.4 Additional OPTIONS Semantics
If the server supports the merge option, 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.
8.5 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.
8.6 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.
9 LABEL OPTION
A version "label" is a string that distinguishes one version of a
version history from all other versions of 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.
Clemm, et al. [Page 50]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
For certain methods, if the request-URL identifies a version-
controlled resource, a label can be specified in a Label request
header (see section 9.3) to cause the method to be applied to the
version selected by that label from the version history of that
version-controlled resource.
Note that it is hard for a distributed versioning server to support
labels. In order to ensure that a label does not get assigned to
multiple versions of the same version history, only one server
could assign labels to a given version history. Otherwise, two
temporarily disconnected servers that have copies of a version
history could assign the same label to different versions of that
version history, resulting in two versions in that version history
with the same label when the two servers are synchronized.
9.1 Additional Version Properties
The label option introduces the following properties for a version.
9.1.1DAV:label-name-set (protected)
This property contains the labels that currently select this
version.
PCDATA value: string
9.2 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 octet-by-octet comparison of the two label names.
If a LABEL request is applied to a version-controlled resource, the
operation MUST be applied to the DAV:checked-in version of that
version-controlled resource.
Marshalling:
The request body MUST be a DAV:label element.
ANY value: A sequence of elements with at most one DAV:add,
DAV:set, or DAV:remove element.
Clemm, et al. [Page 51]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
PCDATA value: string
The request MAY include a Label header.
The request MAY include 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. 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.
The response MUST include a Cache-Control:no-cache header.
Preconditions:
(DAV:must-not-be-checked-out): If the request-URL identifies a
version-controlled resource, the version-controlled resource MUST
NOT be checked out.
(DAV:must-select-version-in-same-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-be-new-label): If DAV:add is specified in the request
body, the specified label MUST NOT currently select a version of
the version history of that version-controlled resource.
(DAV:label-must-exist): If DAV:remove is specified in the request
body, the specified label MUST select that version.
Postconditions:
(DAV:add-label): If DAV:add or DAV:set is specified in the request
body, the specified label selects the version.
(DAV:remove-label): If DAV:remove is specified in the request body,
the specified label no longer selects any version of the version
history of the version-controlled resource.
9.2.1Example - Setting a label
>>REQUEST
LABEL /foo.html HTTP/1.1
Host: www.webdav.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxxx
released
Clemm, et al. [Page 52]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
>>RESPONSE
HTTP/1.1 200 OK
Cache-Control: no-cache
In this example, the label "released" is applied to the
DAV:checked-in version of /foo.html.
9.3 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.
The following defines the BNF for the Label header:
Label := "Label" ":" string
An example of a Label header is:
Label: released
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, PROPFIND)
that includes a Label header.
9.4 Additional OPTIONS Semantics
If the server supports the label option, 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.
9.5 Additional GET Semantics
Additional Marshalling:
The request MAY include a Label header.
Additional Preconditions:
(DAV:must-select-version-in-same-history): If a Label request
header is included and the request-URL identifies a version-
Clemm, et al. [Page 53]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
controlled resource, the specified label MUST select a version in
the version history of the version-controlled resource.
Additional Postconditions:
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.
9.6 Additional PROPFIND Semantics
Additional Marshalling:
The request MAY include a Label header.
Additional Preconditions:
(DAV:must-select-version-in-same-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:
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.
9.7 Additional COPY Semantics
Additional Marshalling:
The request MAY include a Label header.
Additional Preconditions:
(DAV:must-select-version-in-same-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:
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.
Clemm, et al. [Page 54]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
9.8 Additional CHECKOUT Semantics
Additional Marshalling:
The request MAY include a Label header.
Additional Preconditions:
(DAV:must-select-version-in-same-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:
If the request-URL identifies a 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. A new working resource
MUST have been created and the version-controlled resource MUST
remain checked in.
9.9 Additional UPDATE Semantics
A label can be specified to update the content and dead properties
of the version-controlled resource to be those of the version
selected by the specified label from the version history of the
version-controlled resource identified.
Additional Marshalling:
ANY value: A sequence of elements with at most one DAV:label-name
element.
PCDATA value: string
The request MAY include a Depth header.
Additional Preconditions:
(DAV:must-not-have-label-and-apply-to-version): The request body
MUST NOT include both a DAV:label-name element and a DAV:apply-to-
version element.
(DAV:must-select-version-in-same-history): If the request includes
a DAV:label 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.
(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
Clemm, et al. [Page 55]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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:
If a Label request header is included, the content and dead
properties of the version-controlled resource are updated to be
those of the version selected by that label.
10 BASELINE OPTION
A "configuration" of a collection consists of the state of that
collection and the state of all members of that collection. 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 copy of its root collection. A
"baseline" is a special kind of version resource that captures the
state of the version-controlled members of a configuration. In
particular, it captures the DAV:checked-in version of each version-
controlled resource that is a member of the root collection, as
well as the DAV:checked-in version of the collection if the
collection itself is a version-controlled resource. A "baseline
history" is a special kind of 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
"baseline selector".
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 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.
10.1Baseline Selector Properties
Since a baseline selector is a version-controlled resource, it has
all the properties of a version-controlled resource. In addition,
the baseline option introduces the following properties for a
baseline selector.
10.1.1 DAV:baseline-controlled-collection (computed)
This property identifies the collection that contains the version-
controlled resources whose DAV:checked-in versions are being
tracked by this baseline selector. The DAV:baseline-selector of
Clemm, et al. [Page 56]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
the DAV:baseline-controlled-collection of a baseline selector MUST
identify that baseline selector.
10.1.2 DAV:subbaseline-set
This property appears on a checked-out baseline selector, and
determines the DAV:subbaseline-set property of the baseline that
results from checking in this resource.
10.2Baseline 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 option introduces the
following properties for a baseline.
10.2.1 DAV:baseline-collection (protected)
This property contains a server-defined URL for a collection of
checked-in version-controlled resources, where each member of this
collection has the same DAV:checked-in version and relative name as
a member of the baseline-controlled collection at the time the
baseline was created. At most one member of this collection can
have a DAV:checked-in version from a given version history.
10.2.2 DAV:subbaseline-set (protected)
The URL's in the DAV:subbaseline-set property MUST identify a set
of other baselines. The set of versions captured by the
DAV:baseline-collection of a baseline is logically extended by the
versions captured by these other baselines. This extended version
set MUST NOT contain more than one version from any version
history. A server that supports the baseline option MAY choose to
not support the DAV:subbaseline-set property.
10.3Additional Collection Properties
The baseline option introduces the following properties for a
collection.
10.3.1 DAV:baseline-selector (protected)
This property indicates that the collection is under baseline
control. It identifies the baseline selector that is used to
Clemm, et al. [Page 57]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
access baselines of this collection. A server MAY automatically
assign a DAV:baseline-selector property to a collection when it is
created, or a client can use the BASELINE-CONTROL method to request
that a baseline selector be created for a specified collection.
10.4Additional Workspace Properties
The baseline option introduces the following properties for a
workspace.
10.4.1 DAV:baseline-controlled-collection-set (computed)
This property identifies the members of the collection that are
under baseline control.
10.5BASELINE-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:baseline-selector property of the collection is
set to identify a new baseline selector. This baseline selector
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 baseline selector 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, and
the DAV:checked-in version of the baseline selector will be a new
baseline in that baseline history. This new baseline captures the
DAV:checked-in version and relative name of each version-controlled
members of the collection at the time of the request.
Marshalling:
If a request body is included, it MUST be a DAV:baseline-control
XML element.
ANY value: A sequence of elements with at most one DAV:baseline
element.
Clemm, et al. [Page 58]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Preconditions:
(DAV:baseline-selector-must-be-empty): The DAV:baseline-selector
property of the collection identified by the request-URL MUST be
empty.
(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 the DAV:baseline element in the request body
identifies a baseline history, then there MUST NOT be another
collection in that workspace whose DAV:baseline-selector property
identifies a baseline selector for that baseline history.
Postconditions:
(DAV:create-baseline-selector): A new baseline selector is created,
whose DAV:baseline-controlled-collection property identifies the
collection.
(DAV:reference-baseline-selector): The DAV:baseline-selector of the
collection identifies the new baseline selector.
(DAV:select-existing-baseline): If the request body specifies a
baseline, the DAV:checked-in property of the new baseline selector
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.
(DAV:create-empty-baseline): If no baseline is specified in the
request body, a new baseline history with an empty root baseline is
created at a server-defined URL, and the DAV:checked-in property of
the new baseline selector identifies the root baseline of the new
baseline history.
10.5.1 Example - BASELINE-CONTROL
>>REQUEST
BASELINE-CONTROL /src HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml; charset="utf-8"
Clemm, et al. [Page 59]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Content-Length: xxxx
http://repo.webdav.org/bl-his/22/bl/17
>>RESPONSE
HTTP/1.1 200 OK
In this example, the collection identified by
http://www.webdav.org/src is placed under baseline control and is
initialized with version-controlled members whose DAV:checked-in
versions are those selected by the baseline identified by
http://repo.webdav.org/bl-his/22/bl/17.
10.6DAV:baseline-comparison REPORT
A DAV:baseline-comparison 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 DAV:baseline-comparison REPORT request body MUST be a
DAV:baseline-comparison XML element.
The DAV:baseline-comparison REPORT response body MUST be a
DAV:baseline-comparison-report XML element.
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.
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.
Clemm, et al. [Page 60]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
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.
10.6.1 Example - DAV:baseline-comparison 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
http://repo.webdav.org/bl-his/12/bl/15
>>RESPONSE
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
http://repo.webdav.org/his/23/ver/8
http://repo.webdav.org/his/29/ver/12
http://repo.webdav.org/his/29/ver/19
http://repo.webdav.org/his/12/ver/4
In this example, the differences between baseline 14 and baseline
15 of http://repo.webdav.org/bl-his/12 are identified.
Clemm, et al. [Page 61]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
10.7Additional OPTIONS Semantics
If a server supports the baseline option, 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.
10.8Additional 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.
10.9Additional COPY Semantics
Additional Postconditions:
If a server automatically puts a newly created collection under
baseline control, all postconditions for BASELINE-CONTROL apply to
the COPY.
10.10 Additional CHECKIN Semantics
Additional Preconditions:
(DAV:no-checked-out-baseline-controlled-collection-members): If the
request-URL identifies a baseline selector, all version-controlled
members of the DAV:baseline-controlled-collection of the baseline
selector MUST be checked-in.
Additional Postconditions:
(DAV:create-baseline-collection): If the request-URL identifies a
baseline selector, 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 baseline-
controlled-collection of the baseline selector at the time of the
request.
(DAV:auto-baseline): If the request updated the DAV:checked-in
property of any version-controlled member of a baseline-controlled
collection, and if DAV:auto-version is set for the baseline
selector of that baseline-controlled collection, then standard
auto-versioning semantics apply.
Clemm, et al. [Page 62]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
10.11 Additional UPDATE Semantics
Additional Preconditions:
(DAV:baseline-controlled-members-must-be-checked-in): If the
request-URL identifies a baseline selector, then all version-
controlled members of the DAV:baseline-controlled-collection of
that baseline selector MUST be checked-in.
Additional Postconditions:
(DAV:set-baseline-controlled-collection-members): If the request-
URL identifies a baseline selector and the DAV:version element
identifies a baseline, then the version-controlled members of the
DAV:baseline-controlled-collection of that baseline selector 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:
- 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:auto-baseline): If the request modified the DAV:checked-in
property of any version-controlled member of a baseline-controlled
collection, and if DAV:auto-version is set for the baseline
selector of that baseline-controlled collection, then standard
auto-versioning semantics apply.
10.12 Additional MERGE Semantics
If the merge version is a baseline, the merge target is a baseline
selector for the baseline history of that baseline, where the
baseline-controlled collection of that baseline selector is a
member of the merge destination of the request.
Additional Postconditions:
(DAV:merge-baseline): If the merge target is a baseline selector
whose DAV:checked-out baseline is not a descendant of the merge
Clemm, et al. [Page 63]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
baseline, then the merge baseline MUST have been added to the
DAV:auto-merge-set of a baseline selector. Each baseline in the
DAV:subbaseline-set of that baseline MUST have been merged into the
merge destination, and 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 baseline
selector.
(DAV:auto-baseline): If the request updated the DAV:checked-in
property of any version-controlled member of a baseline-controlled
collection, and if DAV:auto-version is set for the baseline
selector of that baseline-controlled collection, then standard
auto-versioning semantics apply.
11 ACTIVITY OPTION
An "activity" is a non-versionable 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 author
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.
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.
Clemm, et al. [Page 64]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
foo.html History bar.html History
+---+ +---+
Act-1| |V1 Act-1| |V6
+---+ +---+
| |
| |
+---+ +---+
Act-1| |V2 Act-2| |V7
+---+ +---+
/ \ |
/ \ |
+---+ +---+ +---+
Act-1| | 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".
11.1Activity Properties
The activity option introduces the following properties for an
activity.
11.1.1 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 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.
11.1.2 DAV:activity-checkout-set (computed)
This property identifies each checked-out resource whose
DAV:activity-set identifies this activity.
Clemm, et al. [Page 65]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
11.1.3 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 that supports the
activity option MAY choose to not support the DAV:subactivity-set
property.
11.1.4 DAV:current-workspace-set (computed)
This property identifies each workspace whose DAV:current-activity-
set identifies this activity.
11.2Additional Version Properties
The activity option introduces the following properties for a
version.
11.2.1 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.
11.3Additional Version-Controlled Resource Properties
The activity option introduces the following properties for a
version-controlled resource.
11.3.1 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.
Clemm, et al. [Page 66]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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 author 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.
PCDATA value: boolean
11.3.2 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.
11.4Additional Workspace Properties
The activity option introduces the following properties for a
workspace.
11.4.1 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.
11.5MKACTIVITY 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:
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.
Clemm, et al. [Page 67]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
(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.
The DAV:activity-version-set, DAV:subactivity-set, and DAV:current-
workspace-set of the activity MUST be empty.
11.5.1 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.
11.6DAV: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 DAV:latest-activity-version REPORT request body MUST be a
DAV:latest-activity-version XML element.
The DAV:latest-activity-version REPORT response body MUST be a
DAV:latest-activity-version-report XML element.
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 ancestor that is a member of
the DAV:activity-version-set of the given activity.
Clemm, et al. [Page 68]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Preconditions:
(DAV:must-be-activity): The DAV:href in the request body MUST
identify an activity.
11.7Additional OPTIONS Semantics
If the server supports the activity option, 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.
Often a versioning implementation constrains where an activity can
be located in the URL space. The DAV:activity-collection-set
identifies collections that may contain activities. An activity
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 collections identified by the DAV:activity-collection-
set MAY be located on different hosts from the resource.
Additional Marshalling:
If a request body is included, it MUST be a DAV:options XML
element.
ANY value: A sequence of elements with at most one DAV:activity-
collection-set element.
If a response body is included, it MUST be a DAV:options-response
XML element.
ANY value: A sequence of elements with at most one DAV:activity-
collection-set element.
If DAV:activity-collection-set is included in the request body, the
response body MUST contain a DAV:activity-collection-set element
identifying which collections may contain activities.
11.8Additional 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. [Page 69]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
11.9Additional 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
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.
11.10 Additional CHECKOUT Semantics
A CHECKOUT request MAY specify the DAV:activity-set for the
checked-out resource.
Additional Marshalling:
ANY value: A sequence of elements with at most one DAV:activity-set
and at most one DAV:unreserved.
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.
Additional Postconditions:
(DAV:initialize-activity-set): The DAV:activity-set of the checked-
out resource is set as follows:
- If DAV:new is specified as the DAV:activity-set in the request
body, then a new activity created by the server is used.
Clemm, et al. [Page 70]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
- Otherwise, if activities are specified in the request body, then
those activities are used.
- 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".
11.10.1 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
http://repo.webdav.org/act/fix-bug-23
>>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.
11.11 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.
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.
Clemm, et al. [Page 71]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
11.12 Additional MERGE Semantics
If the DAV:source element of the request body identifies an
activity, then all checked-out resources in that activity (or any
subactivity of that activity) are checked in, and then for each
version history containing a version selected by that activity, the
latest version selected by that activity is a merge version. 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.
A checked-out baseline in the activity is checked-in only after all
other checked-out resources have been checked in and merged to
their merge target. This ensures that modifications to members of
a collection are captured by any new baseline of that collection.
If a working baseline is checked in, the baseline-controlled
collection that determines the DAV:baseline-collection of the new
baseline is the merge target of that working baseline.
Additional Preconditions:
(DAV:atomic-activity-checkin): If the DAV:source element identifies
an activity, the server MAY fail the request if any of the checked-
out resources in the DAV:activity-checkout-set of the activity
cannot be checked in.
Additional Postconditions:
(DAV:checkin-activity): If the DAV:source element identified an
activity, before determining the merge versions, the server MUST
have checked in each checked-out resource that was in the
DAV:activity-checkout-set. Before checking in a checked-out
baseline, the server MUST have already checked in and merged all
checked-out non-baseline resources. If a checked-out baseline was
a working baseline, the baseline-controlled collection that
determined the DAV:baseline-collection for the new baseline MUST
have been the merge target for that new baseline.
12 VERSION-CONTROLLED-COLLECTION OPTION
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 is not itself a collection, but just records in its
DAV:version-controlled-binding-set property the binding name and
version history resource of each version-controlled internal member
Clemm, et al. [Page 72]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
Clemm, et al. [Page 73]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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" and
version history VH19, and the other with binding name "b" and
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-controlled resource /x/a currently has
V4 of VH19 as its DAV:checked-in version, while /x/b has V8 of
VH24as 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. If the version-controlled collection
has a DAV:auto-version property, standard auto-versioning semantics
Clemm, et al. [Page 74]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
apply. This functionality allows a versioning unaware client to
add a version to the collection version history.
12.1Eclipsed Version-Controlled Bindings
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-version-controlled bindings are not under version
control, and therefore can be added or deleted without checking out
the version-controlled collection. This feature is essential for
the support of lock null resources, since a lock null resource is a
temporary internal member of a collection that should only exist
for the duration of the lock, and should not be captured in the
version history of that collection.
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.
12.2Working Collections
When a server supports the working-resource option, 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
resource is initialized to contain bindings to the version history
resources specified by the DAV:version-controlled-binding-set of
the checked out 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.
12.3Collection Version Properties
A collection has all the properties of a version. In addition, the
version-controlled-collection option introduces the following
properties for a collection version.
Clemm, et al. [Page 75]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
12.3.1 DAV:version-controlled-binding-set
This property determines the DAV:version-controlled-binding-set
property of the collection version that results from checking in
this resource.
PCDATA value: URL segment
12.4Version-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 option introduces the following
properties for a version-controlled collection.
12.4.1 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.
12.5Additional OPTIONS Semantics
If the server supports the version-controlled-collection option, 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.
12.6Additional 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
is set for that version-controlled collection.
Clemm, et al. [Page 76]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
12.7Additional 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.
12.8Additional 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 is set for 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 is set for
that version-controlled collection.
12.9Additional 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 is set for that version-
controlled collection.
12.10 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.
Clemm, et al. [Page 77]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
12.11 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
members 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 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.
12.12 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:
- 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
root version of that version history MUST have been used.
Clemm, et al. [Page 78]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
13 FORK-CONTROL OPTION
Some servers provide the ability for a client to control whether a
fork can be created from a given version. Note that fork-control
does not guarantee the absence of forking, because in a distributed
versioning system, a server does not always have access to all
other servers that allow successors to be created for a given
version. For example, if a version has no successors and is
available on two temporarily disconnected servers, even if that
version is marked as being non-forking, each server would allow it
to be given a single successor, and when the servers are
synchronized, the version will end up with two successors.
13.1Additional Version Properties
The fork-control option introduces the following properties for a
version.
13.1.1 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.
ANY value: A sequence of elements with at most one DAV:ok,
DAV:discouraged, or DAV:forbidden element.
13.1.2 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.
ANY value: A sequence of elements with at most one DAV:ok,
DAV:discouraged, or DAV:forbidden element.
Clemm, et al. [Page 79]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
13.2Additional Version-Controlled Resource Properties
The fork-control option introduces the following properties for a
version-controlled resource.
13.2.1 DAV:checkout-fork
This property of a checked-out version-controlled resource
determines the DAV:checkout-fork property of the version that
results from checking in this version-controlled resource.
13.2.2 DAV:checkin-fork
This property of a checked-out version-controlled resource
determines the DAV:checkin-fork property of the version that
results from checking in this version-controlled resource.
13.3Additional OPTIONS Semantics
If the server supports the fork-control option, it MUST include
"fork-control" as a field in the DAV response header from an
OPTIONS request on any resource that supports any versioning
properties, reports, or methods.
13.4Additional CHECKOUT Semantics
Additional Marshalling:
ANY value: A sequence of elements with at most one DAV:fork-ok
element.
Additional Preconditions:
(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.
(DAV:checkout-of-checked-out-version-is-forbidden): If the
DAV:checkout-fork property of the version being checked out is
Clemm, et al. [Page 80]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
13.5Additional CHECKIN Semantics
Additional Marshalling:
ANY value: A sequence of elements with at most one DAV:fork-ok
element.
Additional Preconditions:
(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.
14 VARIANT OPTION
The variant option provides a mechanism for a server to expose a
subset of the versions from the history of a version-controlled
resource as a set of special version-controlled resources called
"variants" of that version-controlled resource. When variants of a
version-controlled resource are being maintained, that version-
controlled resource is called a "variant-controlled resource".
Variants of a resource might be distinguished by language, format,
or any other category of interest to a client.
Like any other version-controlled resource, a variant can be
checked out in order to modify its content or dead properties.
When a variant of a variant-controlled resource is checked in, a
new version is added to the version history of the variant-
controlled resource. When the variant-controlled resource itself
is checked out and checked in, both a new version and a new variant
is created. The new variant becomes the "default variant" of that
variant-controlled resource.
Unlike the URL for a version, which uniquely identifies exactly
that version and is therefore inevitably quite obscure, the URL for
Clemm, et al. [Page 81]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
a variant is intended to be meaningful to a user, but there is no
guarantee that a URL for a variant will continue to identify that
variant. In particular, the URL for a variant of a version-
controlled resource will usually change whenever that version-
controlled resource is moved.
14.1Variant-Controlled Resource Properties
Since a variant-controlled resource is a version-controlled
resource, it has all the properties of a version-controlled
resource. In addition, the variant option introduces the following
properties for a variant-controlled resource.
14.1.1 DAV:variant-set (protected)
This property identifies each variant of the variant-controlled
resource.
14.1.2 DAV:default-variant (protected)
This property identifies the default variant of the variant-
controlled resource. Whenever the DAV:checked-in value of the
default variant is updated, the content, dead properties, and
DAV:checked-in property of the variant-controlled resource are
updated to be those of the default variant.
14.2Additional DELETE Semantics
Additional Preconditions:
(DAV:delete-variant-reference): The request-URL MUST NOT identify a
variant identified by the DAV:default-variant of a variant-
controlled resource.
Additional Postconditions:
(DAV:delete-variant-reference): If the request-URL identifies a
variant, any reference to that variant in a DAV:variant-set MUST be
removed.
14.3Additional MOVE Semantics
Additional Preconditions:
(DAV:cannot-rename-variant): If the request-URL identifies a
variant, the request MUST fail.
Clemm, et al. [Page 82]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
14.4Additional VERSION-CONTROL Semantics
A VERSION-CONTROL request may specify that variants MUST be
maintained for the version-controlled resource.
Additional Marshalling:
ANY value: A sequence of elements with at most one DAV:variant-
control element.
Additional Postconditions:
(DAV:variant-control): The DAV:default-variant property of the
version-controlled resource MUST identify a new variant resource
whose DAV:checked-in property identifies the new version. The
DAV:variant-set of the version-controlled resource MUST contain a
URL for this new variant.
14.5Additional CHECKIN Semantics
Additional Postconditions:
(DAV:create-new-variant): If the request-URL identifies a variant-
controlled resource, the DAV:default-variant of the variant-
controlled resource MUST have been updated to identify a new
variant whose DAV:checked-in property identifies the new version,
and the DAV:variant-set of the variant-controlled resource MUST
have been updated to contain a URL for this new variant.
(DAV:update-variant-controlled-resource): If the request-URL
identifies the default variant of a variant-controlled resource,
then the DAV:checked-in property of the variant-controlled resource
MUST have been updated to identify the new version. If the
variant-controlled resource is checked in, then the content and
dead properties of the variant-controlled resource MUST have been
updated to be those of the new version.
(DAV:delete-variant-predecessor): If the DAV:checked-in property of
a variant is modified, the version previously identified by the
DAV:checked-in property MAY have been automatically deleted by the
server.
14.6Additional UPDATE Semantics
Additional Marshalling:
ANY value: A sequence of elements with at most one DAV:variant
element.
Clemm, et al. [Page 83]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Preconditions:
(DAV:must-select-variant): If the request-URL identifies a variant-
controlled resource, the request body MUST contain a DAV:variant
element that identifies a variant in the DAV:variant-set of the
variant-controlled resource.
Additional Postconditions:
(DAV:update-default-variant): If the request-URL identifies a
variant-controlled resource, the DAV:default-variant property of
the variant-controlled resource MUST have been updated to identify
the variant identified by the DAV:variant element in the request
body. The content, dead properties, and DAV:checked-in property of
the variant-controlled resource MUST have been updated to be those
of that variant.
(DAV:update-variant-controlled-resource): If the request-URL
identifies the default variant of a variant-controlled resource,
then the DAV:checked-in property of the variant-controlled resource
MUST have been updated to identify the new version. If the
variant-controlled resource is checked in, then the content and
dead properties of the version-controlled resource MUST have been
updated to be those of the new version.
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.
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 2376. 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 1766) or ISO 639 language tags in
the "xml:lang" attribute of an XML element to identify the language
of its content and attributes.
Clemm, et al. [Page 84]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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
2376 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
encoded using UTF-8.
16 SECURITY CONSIDERATIONS
Security considerations from RFC 2518 are also applicable to WebDAV
Versioning.
17 AUTHENTICATION
Authentication mechanisms defined in WebDAV will also apply to
WebDAV Versioning.
18 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.
19 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.
Clemm, et al. [Page 85]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
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.
20 ACKNOWLEDGEMENTS
This protocol is the collaborative product of the authors and the
rest of the DeltaV design team: Boris Bokowski (OTI), Bruce Cragun
(Novell), Jim Doubek (Macromedia), David Durand (INSO), Lisa
Dusseault (Xythos), Tim Ellison (OTI), Chuck Fay (FileNet), Yaron
Goland, Mark Hale (Interwoven), Henry Harbury (Merant), James Hunt,
Jeff McAffer (OTI), Juergen Reuter, Edgar Schwarz, 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.
21 REFERENCES
[ISO639] ISO, "Code for the representation of names of languages",
ISO 639:1988, 1998.
[RFC1766] H.T.Alvestrand, "Tags for the Identification of
Languages", Uninett, 1995.
[RFC2026] S.Bradner, "The Internet Standards Process", Harvard,
1996.
[RFC2119] S.Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", Harvard, 1997.
[RFC2277] H.T.Alvestrand, "IETF Policy on Character Sets and
Languages", BCP 18, Uninett, 1998.
[RFC2279] F.Yergeau, "UTF-9, a transformation format of Unicode and
ISO 10646", Alis Technologies, 1998.
[RFC2376] E.Whitehead, M.Murata, "XML Media Types", U.C.Irvine,
Fuji-Xerox, 1998.
[RFC2396] T.Berners-Lee, R.Fielding, L.Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", MIT, U.C.Irvine, Xerox, 1998.
[RFC2518] Y.Goland, E.Whitehead, A.Faizi, S.R.Carter, D.Jensen,
"HTTP Extensions for Distributed Authoring - WEBDAV", Microsoft,
U.C.Irvine, Netscape, Novell, 1999.
Clemm, et al. [Page 86]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
[RFC2616] R.Fielding, J.Gettys, J.C.Mogul, H.Frystyk, L.Masinter,
P.Leach, and T.Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", U.C.Irvine, Compaq, Xerox, Microsoft, MIT/LCS, 1999.
22 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
Christopher Kaler
Microsoft
One Microsoft Way, Redmond, WA 90852
Email: ckaler@microsoft.com
Jim Whitehead
University of California, Santa Cruz
Santa Cruz, CA
Email: ejw@cse.ucsc.edu
23 APPENDIX A: CLARIFICATIONS AND EXTENSIONS TO RFC 2518
In order for clients and servers to successfully interoperate
through the versioning protocol, the following clarifications and
extensions to RFC 2518 are required. These clarifications and
extensions are included in this document, so that the
implementation of versioning clients and servers is not delayed
until a new revision of RFC 2518 has been accepted.
23.1Additional Resource Properties
WebDAV versioning introduces the following properties for any
WebDAV resource.
23.1.1 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.
Clemm, et al. [Page 87]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
23.1.2 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.
23.2Response Bodies for 403 and 409 Status Responses
A 403 (Forbidden) status indicates that an error has occurred that
the client cannot resolve, and therefore the request should not be
resubmitted. A 409 (Conflict) status indicates that an error has
occurred that the client can resolve, after which the request could
be resubmitted. According to RFC 2616, Section 10.4: "The 4xx
class of status code is intended for cases in which the client
seems to have erred. Except when responding to a HEAD request, the
server SHOULD include an entity containing an explanation of the
error situation, and whether it is a temporary or permanent
condition."
In order to allow better client handling of 403 and 409 responses,
a distinct XML element type can be associated with each method
precondition and postcondition of a request. When a particular
precondition is violated or a particular postcondition cannot be
satisfied, the appropriate XML element MUST be returned as the top-
level element in the response body unless otherwise negotiated by
the request. In a 207 Multi-Status response, this element would
appear in the appropriate DAV:response-description element.
23.2.1 Example - CHECKOUT request with DAV:must-not-be-checked-out
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
In this example, the request to CHECKOUT /foo.html fails because
/foo.html is already checked out.
Clemm, et al. [Page 88]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
23.3Clarification 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 resources 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 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.
23.4REPORT 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.
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.
The response body MUST contain the requested report.
Clemm, et al. [Page 89]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
Postconditions:
The REPORT method MUST NOT change the content or dead properties of
any resource managed by the server.
If a Depth request header is included, the response MUST be a 207
Multi-Status. The REPORT 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.
23.4.1 Example - weather REPORT
>>REQUEST
REPORT /usa/texas HTTP/1.1
Host: www.geography.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
01/03/2000
>>RESPONSE
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Sunny and Cool
In this example, the weather in Texas on January 3, 2000 is
reported as being sunny and cool.
23.4.2 Example - REPORT with Depth
>>REQUEST
REPORT /usa/texas HTTP/1.1
Host: www.geography.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Depth: infinity
01/03/2000
Clemm, et al. [Page 90]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
>>RESPONSE
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
http://www.geography.org/usa/texas
Sunny and Cool
HTTP/1.1 200 OK
http://www.geography.org/usa/texas/austin
Cloudy and Cool
HTTP/1.1 200 OK
In this example, the weather in Texas on January 3, 2000 is
reported as being sunny and cool, while the weather in Austin (the
only member of the Texas collection) is reported as being cloudy
and cool.
23.5DAV:expand-property REPORT
Many properties consist of a set of one or more 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.
Marshalling:
The DAV:expand-property REPORT request body MUST be a DAV:expand-
property XML element.
name value: a property element type
The request MAY include a Depth header.
Clemm, et al. [Page 91]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
The DAV:expand-property REPORT response body 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.
23.5.1 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.
>>REQUEST
REPORT /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
>>RESPONSE
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
http://www.webdav.org/foo.html
Clemm, et al. [Page 92]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
http://repo.webdav.org/his/23
http://repo.webdav.org/his/23/ver/1
Fred
http://www.webdav.org/ws/dev/sally
HTTP/1.1 200 OK
http://repo.webdav.org/his/23/ver/2
Sally
http://repo.webdav.org/act/add-refresh-
cmd
HTTP/1.1 200 OK
HTTP/1.1 200 OK
HTTP/1.1 200 OK
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.
23.6Additional OPTIONS Semantics
An OPTIONS request can be used to determine the methods, live
properties, and reports that are supported by the resource
identified by the request
Additional Marshaling:
If a request body is included, it MUST be a DAV:options XML
element.
Clemm, et al. [Page 93]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
ANY value: A sequence of elements with at most one DAV:supported-
method-set, DAV:supported-live-property-set, and DAV:supported-
report-set element.
name value: a method name
name value: a property element type
namespace value: an XML namespace
name value: a report element type
namespace value: an XML namespace
If a response body is included, it MUST be a DAV:options-response
XML element.
ANY value: A sequence of elements with at most one DAV:supported-
method-set, DAV:supported-live-property-set, and DAV:supported-
report-set element.
If DAV:supported-method-set is included in the request body, the
response body MUST contain a DAV:supported-method-set element
identifying which of the specified methods are supported by the
resource identified by the request-URL. If the DAV:supported-
method-set in the request body is empty, then the response body
MUST identify all methods supported by the resource.
If DAV:supported-live-property-set is included in the request body,
the response body MUST contain a DAV:supported-live-property-set
element identifying which of the specified live properties are
supported by the resource identified by the request-URL. If the
DAV:supported-live-property-set in the request body is empty, then
the response body MUST identify all live properties supported by
the resource.
If DAV:supported-report-set is included in the request body, the
response body MUST contain a DAV:supported-report-set element
identifying which of the specified reports are supported by the
resource identified by the request-URL. If the DAV:supported-
report-set in the request body is empty, then the response body
MUST identify all reports supported by the resource.
Clemm, et al. [Page 94]
INTERNET-DRAFT WebDAV Versioning January 20, 2001
23.6.1 Example - OPTIONS
>>REQUEST
OPTIONS /foo.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
>>RESPONSE
HTTP/1.1 200 OK
DAV: 1, 2, version-control
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
In this example, the server indicates that it is a class 2 WebDAV
versioning server, that the resource /foo.html supports the method
VERSION-CONTROL but not the method BASELINE-CONTROL, that the
resource /foo.html does not support the DAV:version-history live
property, and that the resource /foo.html supports the DAV:expand-
property report.
Clemm, et al. [Page 95]