Versioning Extensions to WebDAV (Web Distributed Authoring and Versioning)

This document specifies a set of methods, headers, and properties that define the WebDAV (Web Distributed Authoring and Versioning) versioning extensions to the HTTP/1.1 protocol. Versioning is concerned with tracking and accessing the history of important states of a web resource, such as a standalone web page. The benefits of versioning in the context of the worldwide web include: 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. Resource states (versions) are given stable names that can support externally stored links for annotation and link server support. Both annotation and link servers frequently need to store stable references to portions of resources that are not under their direct control. By providing stable states of resources, version control systems allow not only stable pointers into those resources, but also well defined methods to determine the relationships of those states of a resource. WebDAV Versioning defines both basic and advanced versioning functionality. Basic versioning allows users to: Put a resource under version control Determine whether a resource is under version control Determine whether a resource update will automatically be captured as a new version Create and access distinct versions of a resource Advanced versioning provides additional functionality for parallel development and configuration management of sets of web resources. This document will first define the properties and method semantics for the basic versioning features, and then define the additional properties and method semantics for the advanced versioning features. An implementer that is only interested in basic versioning should skip the advanced versioning sections ( to ).

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

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

This document uses the terms defined in RFC 2616, in RFC 2518, and in this section. defines the semantic versioning model underlying this terminology. Version Control, Checked-In, Checked-Out "Version control" is a set of constraints on how a resource can be updated. A resource under version control is either in a "checked-in" or "checked-out" state, and the version control constraints apply only while the resource is in the checked-in state. Versionable Resource A "versionable resource" is a resource that can be put under version control. Version-Controlled Resource When a versionable resource is put under version control, it becomes a "version-controlled resource". A version-controlled resource can be "checked out" to allow modification of its content or dead properties by standard HTTP and WebDAV methods. Checked-Out Resource A "checked-out resource" is a resource under version control that is in the checked-out state. Version Resource A "version resource", or simply "version", is a resource that contains a copy of a particular state (content and dead properties) of a version-controlled resource. A version is created by "checking in" a checked-out resource. The server allocates a distinct new URL for each new version, and this URL will never be used to identify any resource other than that version. The content and dead properties of a version never change. Version History Resource A "version history resource", or simply "version history", is a resource that contains all the versions of a particular version-controlled resource. Version Name A "version name" is a string chosen by the server to distinguish one version of a version history from the other versions of that version history. Versions from different version histories may have the same version name. Predecessor, Successor, Ancestor, Descendant When a version-controlled resource is checked out and then subsequently checked in, the version that was checked out becomes a "predecessor" of the version created by the checkin. A client can specify multiple predecessors for a new version if the new version is logically a merge of those predecessors. When a version is connected to another version by traversing one or more predecessor relations, it is called an "ancestor" of that version. The inverse of the predecessor and ancestor relations are the "successor" and "descendant" relations. Therefore, if X is a predecessor of Y, then Y is a successor of X, and if X is an ancestor of Y, then Y is a descendant of X. Root Version Resource The "root version resource", or simply "root version", is the version in a version history that is an ancestor of every other version in that version history. Workspace Resource A "workspace resource", or simply "workspace", is a collection that contains at most one version-controlled resource for a given version history (see ). Working Resource A "working resource" is a checked-out resource created by the server at a server-defined URL when a version (instead of a version-controlled resource) is checked out. Unlike a checked-out version-controlled resource, a working resource is deleted when it is checked in. Fork, Merge When a second successor is added to a version, this creates a "fork" in the version history. When a version is created with multiple predecessors, this creates a "merge" in the version history. A server may restrict the version history to be linear (with no forks or merges), but an interoperable versioning client should be prepared to deal with both forks and merges in the version history. The following diagram illustrates several of the previous definitions. Each box represents a version and each line between two boxes represents a predecessor/successor relationship. For example, it shows V3 is a predecessor of V5, V7 is a successor of V5, V1 is an ancestor of V4, and V7 is a descendant of V4. It also shows that there is a fork at version V2 and a merge at version V7.

History of foo.html +---+ Root Version -------> | | V1 +---+ ^ | | | | +---+ | Version Name ----> V2 | | | Ancestor +---+ | / \ | / \ | +---+ +---+ | | V3 | | V4 ^ +---+ +---+ | | | | Predecessor | | | | +---+ +---+ | | | V5 | | V6 | Descendant +---+ +---+ | Successor | \ / | | \ / | v +---+ v | | V7 +---+ Label A "label" is a name that can be used to select a version from a version history. A label can be assigned by either a client or the server. The same label can be used in different version histories.

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.

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.

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.

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

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

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

A "precondition" of a method describes the state of the server that must be true for that method to be performed. A "postcondition" of a method describes the state of the server that must be true after that method has been completed. If a method precondition or postcondition for a request is not satisfied, the response status of the request MUST be either 403 (Forbidden) if the request should not be repeated because it will always fail, or 409 (Conflict) if it is expected that the user might be able to resolve the conflict and resubmit the request. In order to allow better client handling of 403 and 409 responses, a distinct XML element type is associated with each method precondition and postcondition of a request. When a particular precondition is not satisfied or a particular postcondition cannot be achieved, the appropriate XML element MUST be returned as the child of a top-level DAV:error element in the response body, unless otherwise negotiated by the request. In a 207 Multi-Status response, the DAV:error element would appear in the appropriate DAV:responsedescription element.

>>REQUEST CHECKOUT /foo.html HTTP/1.1 Host: www.webdav.org

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

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

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

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

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

In order to track the history of the content and dead properties of a versionable resource, a user can put the resource under version control with a VERSION-CONTROL request. A VERSION-CONTROL request performs three distinct operations: It creates a new "version history resource". In basic versioning, a version history resource is not assigned a URL, and hence is not visible in the http scheme URL space. However, when the version-history feature (see ) is supported, this changes, and each version history resource is assigned a new distinct and unique server-defined URL. It creates a new "version resource" and adds it to the new version history resource. The body and dead properties of the new version resource are a copy of those of the versionable resource. The server assigns the new version resource a new distinct and unique URL. It converts the versionable resource into a "version-controlled resource". The version-controlled resource continues to be identified by the same URL that identified it as a versionable resource. As part of this conversion, it adds a DAV:checked-in property, whose value contains the URL of the new version resource. Note that a versionable resource and a version-controlled resource are not new types of resources (i.e. they introduce no new DAV:resourcetype), but rather they are any type of resource that supports the methods and live properties defined for them in this document, in addition to all the methods and live properties implied by their DAV:resourcetype. For example, a collection (whose DAV:resourcetype is DAV:collection) is a versionable resource if it supports the VERSION-CONTROL method, and is a version-controlled resource if it supports the version-controlled resource methods and live properties. In the following example, foo.html is a versionable resource that is put under version control. After the VERSION-CONTROL request succeeds, there are two additional resources: a new version history resource and a new version resource in that version history. The versionable resource is converted into a version-controlled resource, whose DAV:checked-in property identifies the new version resource. The content and dead properties of a resource are represented by the symbol appearing inside the box for that resource (e.g., "S1" in the following example).

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

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. The DAV:auto-version property (see ) of a checked-in version-controlled resource determines how it responds to a method that attempts to modify its content or dead properties. Possible responses include: Fail the request. The resource requires an explicit CHECKOUT request for it to be modified (see Sections and ). Automatically checkout the resource, perform the modification, and automatically checkin the resource. This ensures that every state of the resource is tracked by the server, but can result in an excessive number of versions being created. Automatically checkout the resource, perform the modification, and then if the resource is not write-locked, automatically checkin the resource. If the resource is write-locked, it remains checked-out until the write-lock is removed (either explicitly through a subsequent UNLOCK request or implicitly through a time-out of the write-lock). This helps a locking client avoid the proliferation of versions, while still allowing a non-locking client to update the resource. Automatically checkout the resource, perform the modification, and then leave the resource checked out. If the resource is write-locked, it will be automatically checked in when the write-lock is removed, but an explicit CHECKIN operation (see ) is required for a non-write-locked resource. This minimizes the number of new versions that will be created by a versioning unaware client, but only a versioning aware client can create new versions of a non-write-locked resource. Fail the request unless the resource is write-locked. If it is write-locked, automatically checkout the resource and perform the modification. The resource is automatically checked in when the write-lock is removed. This minimizes the number of new versions that will be created by a versioning unaware client, but never automatically checks out a resource that will not subsequently be automatically checked in. The following diagram illustrates the effect of the checkout/checkin process on a version-controlled resource and its version history. The symbol inside a box (S1, S2, S3) represents the current content and dead properties of the resource represented by that box. The symbol next to a box (V1, V2, V3) represents the URL for that resource.

===checkout==> ===PUT==> ===checkin==> /foo.html (version-controlled resource) +----+ | +----+ | +----+ | +----+ | S2 | | | S2 | | | S3 | | | S3 | +----+ | +----+ | +----+ | +----+ Checked-In=V2|Checked-Out=V2|Checked-Out=V2|Checked-In=V3 /his/73 (version history for /foo.html) +----+ | +----+ | +----+ | +----+ | S1 | V1 | | S1 | V1 | | S1 | V1 | | S1 | V1 +----+ | +----+ | +----+ | +----+ | | | | | | | | | | | | | | +----+ | +----+ | +----+ | +----+ | S2 | V2 | | S2 | V2 | | S2 | V2 | | S2 | V2 +----+ | +----+ | +----+ | +----+ | | | | | | | | | | | +----+ | | | | S3 | V3 | | | +----+ Note that a version captures only a defined subset of the state of a resource. In particular, a version of a basic resource captures its content and dead properties, but not its live properties.

Some versioning information about a resource requires that parameters be specified along with that request for information. Included in basic versioning is the required support for an extensible reporting mechanism, which includes a REPORT method as well as a live property for determining what reports are supported by a particular resource. The REPORT method is required by versioning, but it can be used in non-versioning WebDAV extensions. To allow a client to query the properties of all versions in the version history of a specified version-controlled resource, basic versioning provides the DAV:version-tree report (see ). A more powerful version history reporting mechanism is provided by applying the DAV:expand-property report (see ) to a version history resource (see ).

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

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

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

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

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

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

This property identifies the methods that are supported by the resource. A method is supported by a resource if there is some state of that resource for which an application of that method will successfully satisfy all postconditions of that method, including any additional postconditions added by the features supported by that resource.

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

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

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

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

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

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

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

<!ELEMENT checked-in (href)>

If the DAV:auto-version value is DAV:checkout-checkin, when a modification request (such as PUT/PROPPATCH) is applied to a checked-in version-controlled resource, the request is automatically preceded by a checkout and followed by a checkin operation. If the DAV:auto-version value is DAV:checkout-unlocked-checkin, when a modification request is applied to a checked-in version-controlled resource, the request is automatically preceded by a checkout operation. If the resource is not write-locked, the request is automatically followed by a checkin operation. If the DAV:auto-version value is DAV:checkout, when a modification request is applied to a checked-in version-controlled resource, the request is automatically preceded by a checkout operation. If the DAV:auto-version value is DAV:locked-checkout, when a modification request is applied to a write-locked checked-in version-controlled resource, the request is automatically preceded by a checkout operation. If an update to a write-locked checked-in resource is automatically preceded by a checkout of that resource, the checkout is associated with the write lock. When this write lock is removed (e.g. from an UNLOCK or a lock timeout), if the resource has not yet been checked in, the removal of the write lock is automatically preceded by a checkin operation. A server &MAY; refuse to allow the value of the DAV:auto-version property to be modified, or &MAY; only support values from a subset of the valid values.

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

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

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

<!ELEMENT checked-out (href)>

This property determines the DAV:predecessor-set property of the version that results from checking in this resource. A server &MAY; reject attempts to modify the DAV:predecessor-set of a version-controlled resource.

<!ELEMENT predecessor-set (href+)>

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

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

<!ELEMENT predecessor-set (href*)>

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

<!ELEMENT successor-set (href*)>

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

<!ELEMENT checkout-set (href*)>

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

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

A VERSION-CONTROL request can be used to create a version-controlled resource at the request-URL. It can be applied to a versionable resource or to a version-controlled resource. If the request-URL identifies a versionable resource, a new version history resource is created, a new version is created whose content and dead properties are copied from the versionable resource, and the resource is given a DAV:checked-in property that is initialized to identify this new version. If the request-URL identifies a version-controlled resource, the resource just remains under version-control. This allows a client to be unaware of whether or not a server automatically puts a resource under version control when it is created. If a VERSION-CONTROL request fails, the server state preceding the request MUST be restored. Marshalling: If a request body is included, it MUST be a DAV:version-control XML element.

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

<!ELEMENT version-control-response ANY> Postconditions: (DAV:put-under-version-control): If the request-URL identified a versionable resource at the time of the request, the request MUST have created a new version history and MUST have created a new version resource in that version history. The resource MUST have a DAV:checked-in property that identifies the new version. The content, dead properties, and DAV:resourcetype of the new version MUST be the same as those of the resource. Note that an implementation can choose to locate the version history and version resources anywhere that it wishes. In particular, it could locate them on the same host and server as the version-controlled resource, on a different virtual host maintained by the same server, on the same host maintained by a different server, or on a different host maintained by a different server. (DAV:must-not-change-existing-checked-in-out): If the request-URL identified a resource already under version control at the time of the request, the request &MUST-NOT; change the DAV:checked-in or DAV:checked-out property of that version-controlled resource.

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

>>RESPONSE HTTP/1.1 200 OK In this example, /foo.html is put under version control. A new version history is created for it, and a new version is created that has a copy of the content and dead properties of /foo.html. The DAV:checked-in property of /foo.html identifies this new version.

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. If no Depth header is included, Depth:0 is assumed. The response body for a successful request MUST contain the requested report. If a Depth request header is included, the response MUST be a 207 Multi-Status. The request MUST be applied separately to the collection itself and to all members of the collection that satisfy the Depth value. The DAV:prop element of a DAV:response for a given resource MUST contain the requested report for that resource. Preconditions: (DAV:supported-report): The specified report MUST be supported by the resource identified by the request-URL. Postconditions: (DAV:no-modification): The REPORT method &MUST-NOT; have changed the content or dead properties of any resource.

The DAV:version-tree report describes the requested properties of all the versions in the version history of a version. If the report is requested for a version-controlled resource, it is redirected to its DAV:checked-in or DAV:checked-out version. The DAV:version-tree report MUST be supported by all version resources and all version-controlled resources. Marshalling: The request body MUST be a DAV:version-tree XML element.

<!ELEMENT version-tree ANY> ANY value: a sequence of zero or more elements, with at most one DAV:prop element. prop: see RFC 2518, The response body for a successful request MUST be a DAV:multistatus XML element.

multistatus: see RFC 2518, The response body for a successful DAV:version-tree REPORT request MUST contain a DAV:response element for each version in the version history of the version identified by the request-URL.

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

foo.html History +---+ | | V1 +---+ / \ / \ +---+ +---+ | | V2 | | V2.1.1 +---+ +---+

>>REQUEST REPORT /foo.html HTTP/1.1 Host: www.webdav.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:version-tree xmlns:D="DAV:"> <D:prop> <D:version-name/> <D:creator-displayname/> <D:successor-set/> </D:prop> </D:version-tree>

>>RESPONSE HTTP/1.1 207 Multi-Status Content-Type: text/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:multistatus xmlns:D="DAV:"> <D:response> <D:href>http://repo.webdav.org/his/23/ver/V1</D:href> <D:propstat> <D:prop> <D:version-name>V1</D:version-name> <D:creator-displayname>Fred</D:creator-displayname> <D:successor-set> <D:href>http://repo.webdav.org/his/23/ver/V2</D:href> <D:href>http://repo.webdav.org/his/23/ver/V2.1.1</D:href> </D:successor-set> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> <D:response> <D:href>http://repo.webdav.org/his/23/ver/V2</D:href> <D:propstat> <D:prop> <D:version-name>V2</D:version-name> <D:creator-displayname>Fred</D:creator-displayname> <D:successor-set/> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> <D:response> <D:href>http://repo.webdav.org/his/23/ver/V2.1.1</D:href> <D:propstat> <D:prop> <D:version-name>V2.1.1</D:version-name> <D:creator-displayname>Sally</D:creator-displayname> <D:successor-set/> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> </D:multistatus>

Many property values are defined as a DAV:href, or a set of DAV:href elements. The DAV:expand-property report provides a mechanism for retrieving in one request the properties from the resources identified by those DAV:href elements. This report not only decreases the number of requests required, but also allows the server to minimize the number of separate read transactions required on the underlying versioning store. The DAV:expand-property report &SHOULD; be supported by all resources that support the REPORT method. Marshalling: The request body MUST be a DAV:expand-property XML element.

<!ELEMENT expand-property (property*)> <!ELEMENT property (property*)> <!ATTLIST property name NMTOKEN #REQUIRED> name value: a property element type <!ATTLIST property namespace NMTOKEN "DAV:"> namespace value: an XML namespace The response body for a successful request MUST be a DAV:multistatus XML element.

multistatus: see RFC 2518, The properties reported in the DAV:prop elements of the DAV:multistatus element MUST be those identified by the DAV:property elements in the DAV:expand-property element. If there are DAV:property elements nested within a DAV:property element, then every DAV:href in the value of the corresponding property is replaced by a DAV:response element whose DAV:prop elements report the values of the properties identified by the nested DAV:property elements. The nested DAV:property elements can in turn contain DAV:property elements, so that multiple levels of DAV:href expansion can be requested. Note that a validating parser MUST be aware that the DAV:expand-property report effectively modifies the DTD of every property by replacing every occurrence of "href" in the DTD with "href | response".

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

>>REQUEST REPORT /foo.html HTTP/1.1 Host: www.webdav.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:expand-property xmlns:D="DAV:"> <D:property name="version-history"> <D:property name="version-set"> <D:property name="creator-displayname"/> <D:property name="activity-set"/> </D:property> </D:property> </D:expand-property>

>>RESPONSE HTTP/1.1 207 Multi-Status Content-Type: text/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:multistatus xmlns:D="DAV:"> <D:response> <D:href>http://www.webdav.org/foo.html</D:href> <D:propstat> <D:prop> <D:version-history> <D:response> <D:href>http://repo.webdav.org/his/23</D:href> <D:propstat> <D:prop> <D:version-set> <D:response> <D:href>http://repo.webdav.org/his/23/ver/1</D:href> <D:propstat> <D:prop> <D:creator-displayname>Fred</D:creator-displayname> <D:activity-set> <D:href> http://www.webdav.org/ws/dev/sally </D:href> </D:activity-set> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> <D:response> <D:href>http://repo.webdav.org/his/23/ver/2</D:href> <D:propstat> <D:prop> <D:creator-displayname>Sally</D:creator-displayname> <D:activity-set> <D:href>http://repo.webdav.org/act/add-refresh-cmd</D:href> </D:activity-set> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> </D:version-set> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> </D:version-history> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> </D:multistatus> In this example, the DAV:creator-displayname and DAV:activity-set properties of the versions in the DAV:version-set of the DAV:version-history of http://www.webdav.org/foo.html are reported.

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

Additional Preconditions: (DAV:cannot-modify-version-controlled-content): If the request-URL identifies a resource with a DAV:checked-in property, the request MUST fail unless DAV:auto-version semantics will automatically check out the resource. (DAV:cannot-modify-version): If the request-URL identifies a version, the request MUST fail. If the request creates a new resource that is automatically placed under version control, all preconditions for VERSION-CONTROL apply to the request. Additional Postconditions: (DAV:auto-checkout): If the resource was a checked-in version-controlled resource whose DAV:auto-version property indicates it should be automatically checked out but not automatically checked in for a modification request, then the server MUST have automatically checked out the resource prior to executing the request. In particular, the value of the DAV:checked-out property of the resource MUST be that of the DAV:checked-in property prior to the request, the DAV:checked-in property MUST have been removed, and the DAV:predecessor-set property MUST be initialized to be the same as the DAV:checked-out property. If any part of the checkout/update sequence failed, the status from the failed part of the request MUST be returned, and the server state preceding the request sequence MUST be restored. (DAV:auto-checkout-checkin): If the resource was a checked-in version-controlled resource whose DAV:auto-version property indicates it should be automatically checked out and automatically checked in for a modification request, then the server MUST have automatically checked out the resource prior to executing the request and automatically checked it in after the request. In particular, the DAV:checked-in property of the resource MUST identify a new version whose content and dead properties are the same as those of the resource. The DAV:predecessor-set of the new version MUST identify the version identified by the DAV:checked-in property prior to the request. If any part of the checkout/update/checkin sequence failed, the status from the failed part of the request MUST be returned, and the server state preceding the request sequence MUST be restored. If the request creates a new resource, the new resource &MAY; have automatically been placed under version control, and all postconditions for VERSION-CONTROL apply to the request.

A DAV:allprop PROPFIND request &SHOULD-NOT; return any of the properties defined by this document. This allows a versioning server to perform efficiently when a naive client, which does not understand the cost of asking a server to compute all possible live properties, issues a DAV:allprop PROPFIND request. Additional Preconditions: (DAV:supported-live-property): If the request attempts to access a property defined by this document, the semantics of that property MUST be supported by the server.

Additional Preconditions: (DAV:cannot-modify-version-controlled-property): If the request attempts to modify a dead property, same semantics as PUT (see ). (DAV:cannot-modify-version): If the request attempts to modify a dead property, same semantics as PUT (see ). (DAV:cannot-modify-protected-property): An attempt to modify a property that is defined by this document, as being protected for that kind of resource, MUST fail. (DAV:supported-live-property): An attempt to modify a property defined by this document, but whose semantics are not enforced by the server, MUST fail. This helps ensure that a client will be notified when it is trying to use a property whose semantics are not supported by the server. Additional Postconditions: (DAV:auto-checkout): If the request modified a dead property, same semantics as PUT (see ). (DAV:auto-checkout-checkin): If the request modified a dead property, same semantics as PUT (see ).

Additional Preconditions: (DAV:no-version-delete): A server &MAY; fail an attempt to DELETE a version. Additional Postconditions: (DAV:update-predecessor-set): If a version was deleted, the server MUST have replaced any reference to that version in a DAV:predecessor-set by a copy of the DAV:predecessor-set of the deleted version.

Additional Preconditions: If the request creates a new resource that is automatically placed under version control, all preconditions for VERSION-CONTROL apply to the request. Additional Postconditions: (DAV:must-not-copy-versioning-property): A property defined by this document &MUST-NOT; have been copied to the new resource created by this request, but instead that property of the new resource MUST have the default initial value it would have had if the new resource had been created by a non-versioning method such as PUT or a MKCOL. (DAV:auto-checkout): If the destination is a version-controlled resource, same semantics as PUT (see ). (DAV:auto-checkout-checkin): If the destination is a version-controlled resource, same semantics as PUT (see ). (DAV:copy-creates-new-resource): If the source of a COPY is a version-controlled resource or version, and if there is no resource at the destination of the COPY, then the COPY creates a new non-version-controlled resource at the destination of the COPY. The new resource &MAY; automatically be put under version control, but the resulting version-controlled resource MUST be associated with a new version history created for that new version-controlled resource, and all postconditions for VERSION-CONTROL apply to the request.

Additional Preconditions: (DAV:cannot-rename-version): If the request-URL identifies a version, the request MUST fail. Additional Postconditions: (DAV:preserve-versioning-properties): When a resource is moved from a source URL to a destination URL, a property defined by this document MUST have the same value at the destination URL as it had at the source URL.

Note that these semantics apply both to an explicit UNLOCK request, as well as to the removal of a lock because of a lock timeout. If a precondition or postcondition cannot be satisfied, the lock timeout &MUST-NOT; occur. Additional Preconditions: (DAV:version-history-is-tree): If the request-URL identifies a checked-out version-controlled resource that will be automatically checked in when the lock is removed, then the versions identified by the DAV:predecessor-set of the checked-out resource MUST be descendants of the root version of the version history for the DAV:checked-out version. Additional Postconditions: (DAV:auto-checkin): If the request-URL identified a checked-out version-controlled resource that had been automatically checked out because of its DAV:auto-version property, the request MUST have created a new version in the version history of the DAV:checked-out version. The request MUST have allocated a URL for the version that &MUST-NOT; have previously identified any other resource, and &MUST-NOT; ever identify a resource other than this version. The content, dead properties, DAV:resourcetype, and DAV:predecessor-set of the new version MUST be copied from the checked-out resource. The DAV:version-name of the new version MUST be set to a server-defined value distinct from all other DAV:version-name values of other versions in the same version history. The request MUST have removed the DAV:checked-out property of the version-controlled resource, and MUST have added a DAV:checked-in property that identifies the new version.

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

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

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

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

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

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

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

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

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

A CHECKOUT request can be applied to a checked-in version-controlled resource to allow modifications to the content and dead properties of that version-controlled resource. If a CHECKOUT request fails, the server state preceding the request MUST be restored. Marshalling: If a request body is included, it MUST be a DAV:checkout XML element.

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

<!ELEMENT fork-ok EMPTY> If a response body for a successful request is included, it MUST be a DAV:checkout-response XML element.

<!ELEMENT checkout-response ANY> The response MUST include a Cache-Control:no-cache header. Preconditions: (DAV:must-be-checked-in): If a version-controlled resource is being checked out, it MUST have a DAV:checked-in property. (DAV:checkout-of-version-with-descendant-is-forbidden): If the DAV:checkout-fork property of the version being checked out is DAV:forbidden, the request MUST fail if a version identifies that version in its DAV:predecessor-set. (DAV:checkout-of-version-with-descendant-is-discouraged): If the DAV:checkout-fork property of the version being checked out is DAV:discouraged, the request MUST fail if a version identifies that version in its DAV:predecessor-set unless DAV:fork-ok is specified in the request body. (DAV:checkout-of-checked-out-version-is-forbidden): If the DAV:checkout-fork property of the version being checked out is DAV:forbidden, the request MUST fail if a checked-out resource identifies that version in its DAV:checked-out property. (DAV:checkout-of-checked-out-version-is-discouraged): If the DAV:checkout-fork property of the version being checked out is DAV:discouraged, the request MUST fail if a checked-out resource identifies that version in its DAV:checked-out property unless DAV:fork-ok is specified in the request body. Postconditions: (DAV:is-checked-out): The checked-out resource MUST have a DAV:checked-out property that identifies the DAV:checked-in version preceding the checkout. The version-controlled resource &MUST-NOT; have a DAV:checked-in property. (DAV:initialize-predecessor-set): The DAV:predecessor-set property of the checked-out resource MUST be initialized to be the DAV:checked-out version.

>>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.

A CHECKIN request can be applied to a checked-out version-controlled resource to produce a new version whose content and dead properties are copied from the checked-out resource. If a CHECKIN request fails, the server state preceding the request MUST be restored. Marshalling: If a request body is included, it MUST be a DAV:checkin XML element.

<!ELEMENT checkin ANY> ANY value: A sequence of elements with at most one DAV:keep-checked-out element and at most one DAV:fork-ok element. <!ELEMENT keep-checked-out EMPTY> <!ELEMENT fork-ok EMPTY> If a response body for a successful request is included, it MUST be a DAV:checkin-response XML element.

<!ELEMENT checkin-response ANY> The response MUST include a Cache-Control:no-cache header. Preconditions: (DAV:must-be-checked-out): The request-URL MUST identify a resource with a DAV:checked-out property. (DAV:version-history-is-tree) The versions identified by the DAV:predecessor-set of the checked-out resource MUST be descendants of the root version of the version history for the DAV:checked-out version. (DAV:checkin-fork-forbidden): A CHECKIN request MUST fail if it would cause a version whose DAV:checkin-fork is DAV:forbidden to appear in the DAV:predecessor-set of more than one version. (DAV:checkin-fork-discouraged): A CHECKIN request MUST fail if it would cause a version whose DAV:checkin-fork is DAV:discouraged to appear in the DAV:predecessor-set of more than one version, unless DAV:fork-ok is specified in the request body. Postconditions: (DAV:create-version): The request MUST have created a new version in the version history of the DAV:checked-out version. The request MUST have allocated a distinct new URL for the new version, and that URL &MUST-NOT; ever identify any resource other than that version. The URL for the new version MUST be returned in a Location response header. (DAV:initialize-version-content-and-properties): The content, dead properties, DAV:resourcetype, and DAV:predecessor-set of the new version MUST be copied from the checked-out resource. The DAV:version-name of the new version MUST be set to a server-defined value distinct from all other DAV:version-name values of other versions in the same version history. (DAV:checked-in): If the request-URL identifies a version-controlled resource and DAV:keep-checked-out is not specified in the request body, the DAV:checked-out property of the version-controlled resource MUST have been removed and a DAV:checked-in property that identifies the new version MUST have been added. (DAV:keep-checked-out): If DAV:keep-checked-out is specified in the request body, the DAV:checked-out property of the checked-out resource MUST have been updated to identify the new version.

>>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.

An UNCHECKOUT request can be applied to a checked-out version-controlled resource to cancel the CHECKOUT and restore the pre-CHECKOUT state of the version-controlled resource. If an UNCHECKOUT request fails, the server MUST undo any partial effects of the UNCHECKOUT request. Marshalling: If a request body is included, it MUST be a DAV:uncheckout XML element.

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

<!ELEMENT uncheckout-response ANY> The response MUST include a Cache-Control:no-cache header. Preconditions: (DAV:must-be-checked-out-version-controlled-resource): The request-URL MUST identify a version-controlled resource with a DAV:checked-out property. Postconditions: (DAV:cancel-checked-out): The value of the DAV:checked-in property is that of the DAV:checked-out property prior to the request, and the DAV:checked-out property has been removed. (DAV:restore-content-and-dead-properties): The content and dead properties of the version-controlled resource are copies of its DAV:checked-in version.

>>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.

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

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

The DAV:resourcetype of a version history MUST be DAV:version-history. The version-history feature introduces the following &REQUIRED; properties for a version history.

This property identifies each version of this version history.

<!ELEMENT version-set (href+)>

This property identifies the root version of this version history.

<!ELEMENT root-version (href)>

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

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

<!ELEMENT version-history (href)>

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

This property identifies the version history that contains this version.

<!ELEMENT version-history (href)>

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

<!ELEMENT locate-by-history (version-history-set, prop)> <!ELEMENT version-history-set (href+)> prop: see RFC 2518, The response body for a successful request MUST be a DAV:multistatus XML element containing every version-controlled resource that is a member of the collection identified by the request-URL, and whose DAV:version-history property identifies one of the version history resources identified by the request body. The DAV:prop element in the request body identifies which properties should be reported in the DAV:prop elements in the response body. 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.

>>REQUEST REPORT /ws/public HTTP/1.1 Host: www.webdav.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:locate-by-history xmlns:D="DAV:"> <D:version-history-set> <D:href>http://repo.webdav.org/his/23</D:href> <D:href>http://repo.webdav.org/his/84</D:href> <D:href>http://repo.webdav.org/his/129</D:href> <D:version-history-set/> <D:prop> </D:version-history> </D:prop> </D:locate-by-history>

If the server supports the version-history feature, it MUST include "version-history" as a field in the DAV response header from an OPTIONS request on any resource that supports any versioning properties, reports, or methods. A DAV:version-history-collection-set element &MAY; be included in the request body to identify collections that may contain version history resources. Additional Marshalling: If an XML request body is included, it MUST be a DAV:options XML element.

<!ELEMENT options ANY> ANY value: A sequence of elements with at most one DAV:version-history-collection-set element. If an XML response body for a successful request is included, it MUST be a DAV:options-response XML element.

<!ELEMENT options-response ANY> ANY value: A sequence of elements with at most one DAV:version-history-collection-set element. <!ELEMENT version-history-collection-set (href*)> If DAV:version-history-collection-set is included in the request body, the response body for a successful request MUST contain a DAV:version-history-collection-set element identifying collections that may contain version histories. An identified collection &MAY; be the root collection of a tree of collections, all of which may contain version histories. Since different servers can control different parts of the URL namespace, different resources on the same host &MAY; have different DAV:version-history-collection-set values. The identified collections &MAY; be located on different hosts from the resource.

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

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.

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

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

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.

In order to allow multiple users to work concurrently on adding versions to the same version history, it is necessary to allocate on the server multiple checked-out resources for the same version history. Even if only one user is making changes to a resource, that user will sometimes wish to create a "private" version, and then to expose that version at a later time. One way to provide this functionality depends on the client keeping track of its current set of checked-out resources. This is the working-resource feature defined in . The other way to provide this functionality avoids the need for persistent state on the client, and instead has the server maintain a human meaningful namespace for related sets of checked-out resources. This is the workspace feature defined in this section. The workspace feature introduces a "workspace resource". A workspace resource is a collection whose members are related version-controlled and non-version-controlled resources. Multiple workspaces may be used to expose different versions and configurations of a set of version-controlled resources concurrently. In order to make changes to a version-controlled resource in one workspace visible in another workspace, that version-controlled resource must be checked in, and then the corresponding version-controlled resource in the other workspace can be updated to display the content and dead properties of the new version. In order to ensure unambiguous merging (see ) and baselining (see ) semantics, a workspace may contain at most one version-controlled resource for a given version history. This is required for unambiguous merging because the MERGE method must identify which version-controlled resource is to be the merge target of a given version. This is required for unambiguous baselining because a baseline can only select one version for a given version-controlled resource. Initially, an empty workspace can be created. Non-version-controlled resources can then be added to the workspace with standard WebDAV requests such as PUT and MKCOL. Version-controlled resources can be added to the workspace with VERSION-CONTROL requests. If the baseline feature is supported, collections in the workspace can be placed under baseline control, and then initialized by existing baselines.

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

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

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

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

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

<!ELEMENT workspace (href)>

A MKWORKSPACE request creates a new workspace resource. A server &MAY; restrict workspace creation to particular collections, but a client can determine the location of these collections from a DAV:workspace-collection-set OPTIONS request (see ). If a MKWORKSPACE request fails, the server state preceding the request MUST be restored. Marshalling: If a request body is included, it MUST be a DAV:mkworkspace XML element.

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

<!ELEMENT mkworkspace-response ANY> The response MUST include a Cache-Control:no-cache header. Preconditions: (DAV:resource-must-be-null): A resource &MUST-NOT; exist at the request-URL. (DAV:workspace-location-ok): The request-URL MUST identify a location where a workspace can be created. Postconditions: (DAV:initialize-workspace): A new workspace exists at the request-URL. The DAV:resourcetype of the workspace MUST be DAV:collection. The DAV:workspace of the workspace MUST identify the workspace.

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

>>RESPONSE HTTP/1.1 201 Created Cache-Control: no-cache In this example, a new workspace is created at http://www.webdav.org/ws/public.

If a server supports the workspace feature, it MUST include "workspace" as a field in the DAV response header from an OPTIONS request on any resource that supports any versioning properties, reports, or methods. If a server supports the workspace feature, it MUST also support the checkout-in-place feature and the version-history feature. A DAV:workspace-collection-set element &MAY; be included in the request body to identify collections that may contain workspace resources. Additional Marshalling: If an XML request body is included, it MUST be a DAV:options XML element.

<!ELEMENT options ANY> ANY value: A sequence of elements with at most one DAV:workspace-collection-set element. If an XML response body for a successful request is included, it MUST be a DAV:options-response XML element.

<!ELEMENT options-response ANY> ANY value: A sequence of elements with at most one DAV:workspace-collection-set element. <!ELEMENT workspace-collection-set (href*)> If DAV:workspace-collection-set is included in the request body, the response body for a successful request MUST contain a DAV:workspace-collection-set element identifying collections that may contain workspaces. An identified collection &MAY; be the root collection of a tree of collections, all of which may contain workspaces. Since different servers can control different parts of the URL namespace, different resources on the same host &MAY; have different DAV:workspace-collection-set values. The identified collections &MAY; be located on different hosts from the resource.

>>REQUEST OPTIONS /doc HTTP/1.1 Host: www.webdav.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:options xmlns:D="DAV:"> <D:version-history-collection-set/> <D:workspace-collection-set/> </D:options>

>>RESPONSE HTTP/1.1 200 OK DAV: 1 DAV: version-control,checkout-in-place,version-history,workspace Content-Type: text/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:options-response xmlns:D="DAV:"> <D:version-history-collection-set> <D:href>http://repo.webdav.org/his</D:href> </D:version-history-collection-set> <D:workspace-collection-set> <D:href>http://www.webdav.org/public/ws</D:href> <D:href>http://www.webdav.org/private/ws</D:href> </D:workspace-collection-set> </D:options-response> In this example, the server indicates that it provides Class 1 DAV support and basic-server-workspace versioning support. In addition, the server indicates the requested locations of the version history resources and the workspace resources.

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

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

A VERSION-CONTROL request can be used to create a new version-controlled resource for an existing version history. This allows the creation of version-controlled resources for the same version history in multiple workspaces. Additional Marshalling:

<!ELEMENT version-control ANY> ANY value: A sequence of elements with at most one DAV:version element. <!ELEMENT version (href)> Additional Preconditions: (DAV:cannot-add-to-existing-history): If the DAV:version-control request body element contains a DAV:version element, the request-URL &MUST-NOT; identify a resource. (DAV:must-be-version): The DAV:href of the DAV:version element MUST identify a version. (DAV:one-version-controlled-resource-per-history-per-workspace): If the DAV:version-control request body specifies a version, and if the request-URL is a member of a workspace, then there &MUST-NOT; already be a version-controlled member of that workspace whose DAV:checked-in or DAV:checked-out property identifies any version from the version history of the version specified in the request body. Additional Postconditions: (DAV:new-version-controlled-resource): If the request-URL did NOT identify a resource, a new version-controlled resource exists at the request-URL whose content and dead properties are initialized by those of the version in the request body, and whose DAV:checked-in property identifies that version.

>>REQUEST VERSION-CONTROL /ws/public/bar.html HTTP/1.1 Host: www.webdav.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:version-control xmlns:D="DAV:"> <D:version> <D:href>http://repo.webdav.org/his/12/ver/V3</D:href> </D:version> </D:version-control>

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

The