| Network Working Group | L.M. Dusseault, Editor |
| Request for Comments: 4918 | CommerceNet |
| Obsoletes: 2518 | June 2007 |
| Category: Standards Track |
HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the “Internet Official Protocol Standards” (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
Copyright © The IETF Trust (2007). All Rights Reserved.
Web Distributed Authoring and Versioning (WebDAV) consists of a set of methods, headers, and content-types ancillary to HTTP/1.1 for the management of resource properties, creation and management of resource collections, URL namespace manipulation, and resource locking (collision avoidance).
RFC 2518 was published in February 1999, and this specification obsoletes RFC 2518 with minor revisions mostly due to interoperability experience.
This document describes an extension to the HTTP/1.1 protocol that allows clients to perform remote Web content authoring operations. This extension provides a coherent set of methods, headers, request entity body formats, and response entity body formats that provide operations for:
Properties: The ability to create, remove, and query information about Web pages, such as their authors, creation dates, etc.
Collections: The ability to create sets of documents and to retrieve a hierarchical membership listing (like a directory listing in a file system).
Locking: The ability to keep more than one person from working on a document at the same time. This prevents the "lost update problem", in which modifications are lost as first one author, then another, writes changes without merging the other author's changes.
Namespace Operations: The ability to instruct the server to copy and move Web resources, operations that change the mapping from URLs to resources.
Requirements and rationale for these operations are described in a companion document, "Requirements for a Distributed Authoring and Versioning Protocol for the World Wide Web" [RFC2291].
This document does not specify the versioning operations suggested by [RFC2291]. That work was done in a separate document, "Versioning Extensions to WebDAV" [RFC3253].
The sections below provide a detailed introduction to various WebDAV abstractions: resource properties (Section 4), collections of resources (Section 5), locks (Section 6) in general, and write locks (Section 7) specifically.
These abstractions are manipulated by the WebDAV-specific HTTP methods (Section 9) and the extra HTTP headers (Section 10) used with WebDAV methods. General considerations for handling HTTP requests and responses in WebDAV are found in Section 8.
While the status codes provided by HTTP/1.1 are sufficient to describe most error conditions encountered by WebDAV methods, there are some errors that do not fall neatly into the existing categories. This specification defines extra status codes developed for WebDAV methods (Section 11) and describes existing HTTP status codes (Section 12) as used in WebDAV. Since some WebDAV methods may operate over many resources, the Multi-Status response (Section 13) has been introduced to return status information for multiple resources. Finally, this version of WebDAV introduces precondition and postcondition (Section 16) XML elements in error response bodies.
WebDAV uses XML ([REC-XML]) for property names and some values, and also uses XML to marshal complicated requests and responses. This specification contains DTD and text definitions of all properties (Section 15) and all other XML elements (Section 14) used in marshalling. WebDAV includes a few special rules on extending WebDAV XML marshalling in backwards-compatible ways (Section 17).
Finishing off the specification are sections on what it means for a resource to be compliant with this specification (Section 18), on internationalization support (Section 19), and on security (Section 20).
Since this document describes a set of extensions to the HTTP/1.1 protocol, the augmented BNF used herein to describe protocol elements is exactly the same as described in Section 2.1 of [RFC2616], including the rules about implied linear whitespace. Since this augmented BNF uses the basic production rules provided in Section 2.2 of [RFC2616], these rules apply to this document as well. Note this is not the standard BNF syntax used in other RFCs.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
Note that in natural language, a property like the "creationdate" property in the "DAV:" XML namespace is sometimes referred to as "DAV:creationdate" for brevity.
URI/URL - A Uniform Resource Identifier and Uniform Resource Locator, respectively. These terms (and the distinction between them) are defined in [RFC3986].
URI/URL Mapping - A relation between an absolute URI and a resource. Since a resource can represent items that are not network retrievable, as well as those that are, it is possible for a resource to have zero, one, or many URI mappings. Mapping a resource to an "http" scheme URI makes it possible to submit HTTP protocol requests to the resource using the URI.
Path Segment - Informally, the characters found between slashes ("/") in a URI. Formally, as defined in Section 3.3 of [RFC3986].
Collection - Informally, a resource that also acts as a container of references to child resources. Formally, a resource that contains a set of mappings between path segments and resources and meets the requirements defined in Section 5.
Internal Member (of a Collection) - Informally, a child resource of a collection. Formally, a resource referenced by a path segment mapping contained in the collection.
Internal Member URL (of a Collection) - A URL of an internal member, consisting of the URL of the collection (including trailing slash) plus the path segment identifying the internal member.
Member (of a Collection) - Informally, a "descendant" of a collection. Formally, an internal member of the collection, or, recursively, a member of an internal member.
Member URL (of a Collection) - A URL that is either an internal member URL of the collection itself, or is an internal member URL of a member of that collection.
Property - A name/value pair that contains descriptive information about a resource.
Live Property - A property whose semantics and syntax are enforced by the server. For example, the live property DAV:getcontentlength has its value, the length of the entity returned by a GET request, automatically calculated by the server.
Dead Property - A property whose semantics and syntax are not enforced by the server. The server only records the value of a dead property; the client is responsible for maintaining the consistency of the syntax and semantics of a dead property.
Principal - A distinct human or computational actor that initiates access to network resources.
State Token - A URI that represents a state of a resource. Lock tokens are the only state tokens defined in this specification.
Properties are pieces of data that describe the state of a resource. Properties are data about data.
Properties are used in distributed authoring environments to provide for efficient discovery and management of resources. For example, a 'subject' property might allow for the indexing of all resources by their subject, and an 'author' property might allow for the discovery of what authors have written which documents.
The DAV property model consists of name/value pairs. The name of a property identifies the property's syntax and semantics, and provides an address by which to refer to its syntax and semantics.
There are two categories of properties: "live" and "dead". A live property has its syntax and semantics enforced by the server. Live properties include cases where a) the value of a property is protected and maintained by the server, and b) the value of the property is maintained by the client, but the server performs syntax checking on submitted values. All instances of a given live property MUST comply with the definition associated with that property name. A dead property has its syntax and semantics enforced by the client; the server merely records the value of the property verbatim.
Properties already exist, in a limited sense, in HTTP message headers. However, in distributed authoring environments, a relatively large number of properties are needed to describe the state of a resource, and setting/returning them all through HTTP headers is inefficient. Thus, a mechanism is needed that allows a principal to identify a set of properties in which the principal is interested and to set or retrieve just those properties.
The value of a property is always a (well-formed) XML fragment.
XML has been chosen because it is a flexible, self-describing, structured data format that supports rich schema definitions, and because of its support for multiple character sets. XML's self-describing nature allows any property's value to be extended by adding elements. Clients will not break when they encounter extensions because they will still have the data specified in the original schema and MUST ignore elements they do not understand.
XML's support for multiple character sets allows any human-readable property to be encoded and read in a character set familiar to the user. XML's support for multiple human languages, using the "xml:lang" attribute, handles cases where the same character set is employed by multiple human languages. Note that xml:lang scope is recursive, so an xml:lang attribute on any element containing a property name element applies to the property value unless it has been overridden by a more locally scoped attribute. Note that a property only has one value, in one language (or language MAY be left undefined); a property does not have multiple values in different languages or a single value in multiple languages.
A property is always represented with an XML element consisting of the property name, called the "property name element". The simplest example is an empty property, which is different from a property that does not exist:
<R:title xmlns:R="http://www.example.com/ns/"></R:title>
The value of the property appears inside the property name element. The value may be any kind of well-formed XML content, including both text-only and mixed content. Servers MUST preserve the following XML Information Items (using the terminology from [REC-XML-INFOSET]) in storage and transmission of dead properties:
For the property name Element Information Item itself:
On all Element Information Items in the property value:
On Attribute Information Items in the property value:
On Character Information Items in the property value:
Since prefixes are used in some XML vocabularies (XPath and XML Schema, for example), servers SHOULD preserve, for any Information Item in the value:
XML Infoset attributes not listed above MAY be preserved by the server, but clients MUST NOT rely on them being preserved. The above rules would also apply by default to live properties, unless defined otherwise.
Servers MUST ignore the XML attribute xml:space if present and never use it to change whitespace handling. Whitespace in property values is significant.
Consider a dead property 'author' created by the client as follows:
<D:prop xml:lang="en" xmlns:D="DAV:">
<x:author xmlns:x='http://example.com/ns'>
<x:name>Jane Doe</x:name>
<!-- Jane's contact info -->
<x:uri type='email'
added='2005-11-26'>mailto:jane.doe@example.com</x:uri>
<x:uri type='web'
added='2005-11-27'>http://www.example.com</x:uri>
<x:notes xmlns:h='http://www.w3.org/1999/xhtml'>
Jane has been working way <h:em>too</h:em> long on the
long-awaited revision of <![CDATA[<RFC2518>]]>.
</x:notes>
</x:author>
</D:prop>
When this property is requested, a server might return:
<D:prop xmlns:D='DAV:'><author
xml:lang='en'
xmlns:x='http://example.com/ns'
xmlns='http://example.com/ns'
xmlns:h='http://www.w3.org/1999/xhtml'>
<x:name>Jane Doe</x:name>
<x:uri added="2005-11-26" type="email"
>mailto:jane.doe@example.com</x:uri>
<x:uri added="2005-11-27" type="web"
>http://www.example.com</x:uri>
<x:notes>
Jane has been working way <h:em>too</h:em> long on the
long-awaited revision of <RFC2518>.
</x:notes>
</author>
</D:prop>
Note in this example:
Implementation note: there are cases such as editing scenarios where clients may require that XML content is preserved character by character (such as attribute ordering or quoting style). In this case, clients should consider using a text-only property value by escaping all characters that have a special meaning in XML parsing.
A property name is a universally unique identifier that is associated with a schema that provides information about the syntax and semantics of the property.
Because a property's name is universally unique, clients can depend upon consistent behavior for a particular property across multiple resources, on the same and across different servers, so long as that property is "live" on the resources in question, and the implementation of the live property is faithful to its definition.
The XML namespace mechanism, which is based on URIs ([RFC3986]), is used to name properties because it prevents namespace collisions and provides for varying degrees of administrative control.
The property namespace is flat; that is, no hierarchy of properties is explicitly recognized. Thus, if a property A and a property A/B exist on a resource, there is no recognition of any relationship between the two properties. It is expected that a separate specification will eventually be produced that will address issues relating to hierarchical properties.
Finally, it is not possible to define the same property twice on a single resource, as this would cause a collision in the resource's property namespace.
Some HTTP resources are dynamically generated by the server. For these resources, there presumably exists source code somewhere governing how that resource is generated. The relationship of source files to output HTTP resources may be one to one, one to many, many to one, or many to many. There is no mechanism in HTTP to determine whether a resource is even dynamic, let alone where its source files exist or how to author them. Although this problem would usefully be solved, interoperable WebDAV implementations have been widely deployed without actually solving this problem, by dealing only with static resources. Thus, the source vs. output problem is not solved in this specification and has been deferred to a separate document.
This section provides a description of a type of Web resource, the collection, and discusses its interactions with the HTTP URL namespace and with HTTP methods. The purpose of a collection resource is to model collection-like objects (e.g., file system directories) within a server's namespace.
All DAV-compliant resources MUST support the HTTP URL namespace model specified herein.
The HTTP URL namespace is a hierarchical namespace where the hierarchy is delimited with the "/" character.
An HTTP URL namespace is said to be consistent if it meets the following conditions: for every URL in the HTTP hierarchy there exists a collection that contains that URL as an internal member URL. The root, or top-level collection of the namespace under consideration, is exempt from the previous rule. The top-level collection of the namespace under consideration is not necessarily the collection identified by the absolute path '/' -- it may be identified by one or more path segments (e.g., /servlets/webdav/...)
Neither HTTP/1.1 nor WebDAV requires that the entire HTTP URL namespace be consistent -- a WebDAV-compatible resource may not have a parent collection. However, certain WebDAV methods are prohibited from producing results that cause namespace inconsistencies.
As is implicit in [RFC2616] and [RFC3986], any resource, including collection resources, MAY be identified by more than one URI. For example, a resource could be identified by multiple HTTP URLs.
Collection resources differ from other resources in that they also act as containers. Some HTTP methods apply only to a collection, but some apply to some or all of the resources inside the container defined by the collection. When the scope of a method is not clear, the client can specify what depth to apply. Depth can be either zero levels (only the collection), one level (the collection and directly contained resources), or infinite levels (the collection and all contained resources recursively).
A collection's state consists of at least a set of mappings between path segments and resources, and a set of properties on the collection itself. In this document, a resource B will be said to be contained in the collection resource A if there is a path segment mapping that maps to B and that is contained in A. A collection MUST contain at most one mapping for a given path segment, i.e., it is illegal to have the same path segment mapped to more than one resource.
Properties defined on collections behave exactly as do properties on non-collection resources. A collection MAY have additional state such as entity bodies returned by GET.
For all WebDAV-compliant resources A and B, identified by URLs "U" and "V", respectively, such that "V" is equal to "U/SEGMENT", A MUST be a collection that contains a mapping from "SEGMENT" to B. So, if resource B with URL "http://example.com/bar/blah" is WebDAV compliant and if resource A with URL "http://example.com/bar/" is WebDAV compliant, then resource A must be a collection and must contain exactly one mapping from "blah" to B.
Although commonly a mapping consists of a single segment and a resource, in general, a mapping consists of a set of segments and a resource. This allows a server to treat a set of segments as equivalent (i.e., either all of the segments are mapped to the same resource, or none of the segments are mapped to a resource). For example, a server that performs case-folding on segments will treat the segments "ab", "Ab", "aB", and "AB" as equivalent. A client can then use any of these segments to identify the resource. Note that a PROPFIND result will select one of these equivalent segments to identify the mapping, so there will be one PROPFIND response element per mapping, not one per segment in the mapping.
Collection resources MAY have mappings to non-WebDAV-compliant resources in the HTTP URL namespace hierarchy but are not required to do so. For example, if resource X with URL "http://example.com/bar/blah" is not WebDAV compliant and resource A with "URL http://example.com/bar/" identifies a WebDAV collection, then A may or may not have a mapping from "blah" to X.
If a WebDAV-compliant resource has no WebDAV-compliant internal members in the HTTP URL namespace hierarchy, then the WebDAV-compliant resource is not required to be a collection.
There is a standing convention that when a collection is referred to by its name without a trailing slash, the server MAY handle the request as if the trailing slash were present. In this case, it SHOULD return a Content-Location header in the response, pointing to the URL ending with the "/". For example, if a client invokes a method on http://example.com/blah (no trailing slash), the server may respond as if the operation were invoked on http://example.com/blah/ (trailing slash), and should return a Content-Location header with the value http://example.com/blah/. Wherever a server produces a URL referring to a collection, the server SHOULD include the trailing slash. In general, clients SHOULD use the trailing slash form of collection names. If clients do not use the trailing slash form the client needs to be prepared to see a redirect response. Clients will find the DAV:resourcetype property more reliable than the URL to find out if a resource is a collection.
Clients MUST be able to support the case where WebDAV resources are contained inside non-WebDAV resources. For example, if an OPTIONS response from "http://example.com/servlet/dav/collection" indicates WebDAV support, the client cannot assume that "http://example.com/servlet/dav/" or its parent necessarily are WebDAV collections.
A typical scenario in which mapped URLs do not appear as members of their parent collection is the case where a server allows links or redirects to non-WebDAV resources. For instance, "/col/link" might not appear as a member of "/col/", although the server would respond with a 302 status to a GET request to "/col/link"; thus, the URL "/col/link" would indeed be mapped. Similarly, a dynamically-generated page might have a URL mapping from "/col/index.html", thus this resource might respond with a 200 OK to a GET request yet not appear as a member of "/col/".
Some mappings to even WebDAV-compliant resources might not appear in the parent collection. An example for this case are servers that support multiple alias URLs for each WebDAV-compliant resource. A server may implement case-insensitive URLs, thus "/col/a" and "/col/A" identify the same resource, yet only either "a" or "A" is reported upon listing the members of "/col". In cases where a server treats a set of segments as equivalent, the server MUST expose only one preferred segment per mapping, consistently chosen, in PROPFIND responses.
The ability to lock a resource provides a mechanism for serializing access to that resource. Using a lock, an authoring client can provide a reasonable guarantee that another principal will not modify a resource while it is being edited. In this way, a client can prevent the "lost update" problem.
This specification allows locks to vary over two client-specified parameters, the number of principals involved (exclusive vs. shared) and the type of access to be granted. This document defines locking for only one access type, write. However, the syntax is extensible, and permits the eventual specification of locking for other access types.
This section provides a concise model for how locking behaves. Later sections will provide more detail on some of the concepts and refer back to these model statements. Normative statements related to LOCK and UNLOCK method handling can be found in the sections on those methods, whereas normative statements that cover any method are gathered here.
The most basic form of lock is an exclusive lock. Exclusive locks avoid having to deal with content change conflicts, without requiring any coordination other than the methods described in this specification.
However, there are times when the goal of a lock is not to exclude others from exercising an access right but rather to provide a mechanism for principals to indicate that they intend to exercise their access rights. Shared locks are provided for this case. A shared lock allows multiple principals to receive a lock. Hence any principal that has both access privileges and a valid lock can use the locked resource.
With shared locks, there are two trust sets that affect a resource. The first trust set is created by access permissions. Principals who are trusted, for example, may have permission to write to the resource. Among those who have access permission to write to the resource, the set of principals who have taken out a shared lock also must trust each other, creating a (typically) smaller trust set within the access permission write set.
Starting with every possible principal on the Internet, in most situations the vast majority of these principals will not have write access to a given resource. Of the small number who do have write access, some principals may decide to guarantee their edits are free from overwrite conflicts by using exclusive write locks. Others may decide they trust their collaborators will not overwrite their work (the potential set of collaborators being the set of principals who have write permission) and use a shared lock, which informs their collaborators that a principal may be working on the resource.
The WebDAV extensions to HTTP do not need to provide all of the communications paths necessary for principals to coordinate their activities. When using shared locks, principals may use any out-of-band communication channel to coordinate their work (e.g., face-to-face interaction, written notes, post-it notes on the screen, telephone conversation, email, etc.) The intent of a shared lock is to let collaborators know who else may be working on a resource.
Shared locks are included because experience from Web-distributed authoring systems has indicated that exclusive locks are often too rigid. An exclusive lock is used to enforce a particular editing process: take out an exclusive lock, read the resource, perform edits, write the resource, release the lock. This editing process has the problem that locks are not always properly released, for example, when a program crashes or when a lock creator leaves without unlocking a resource. While both timeouts (Section 6.6) and administrative action can be used to remove an offending lock, neither mechanism may be available when needed; the timeout may be long or the administrator may not be available.
A successful request for a new shared lock MUST result in the generation of a unique lock associated with the requesting principal. Thus, if five principals have taken out shared write locks on the same resource, there will be five locks and five lock tokens, one for each principal.
A WebDAV-compliant resource is not required to support locking in any form. If the resource does support locking, it may choose to support any combination of exclusive and shared locks for any access types.
The reason for this flexibility is that locking policy strikes to the very heart of the resource management and versioning systems employed by various storage repositories. These repositories require control over what sort of locking will be made available. For example, some repositories only support shared write locks, while others only provide support for exclusive write locks, while yet others use no locking at all. As each system is sufficiently different to merit exclusion of certain locking features, this specification leaves locking as the sole axis of negotiation within WebDAV.
The creator of a lock has special privileges to use the lock to modify the resource. When a locked resource is modified, a server MUST check that the authenticated principal matches the lock creator (in addition to checking for valid lock token submission).
The server MAY allow privileged users other than the lock creator to destroy a lock (for example, the resource owner or an administrator). The 'unlock' privilege in [RFC3744] was defined to provide that permission.
There is no requirement for servers to accept LOCK requests from all users or from anonymous users.
Note that having a lock does not confer full privilege to modify the locked resource. Write access and other privileges MUST be enforced through normal privilege or authentication mechanisms, not based on the possible obscurity of lock token values.
A lock token is a type of state token that identifies a particular lock. Each lock has exactly one unique lock token generated by the server. Clients MUST NOT attempt to interpret lock tokens in any way.
Lock token URIs MUST be unique across all resources for all time. This uniqueness constraint allows lock tokens to be submitted across resources and servers without fear of confusion. Since lock tokens are unique, a client MAY submit a lock token in an If header on a resource other than the one that returned it.
When a LOCK operation creates a new lock, the new lock token is returned in the Lock-Token response header defined in Section 10.5, and also in the body of the response.
Servers MAY make lock tokens publicly readable (e.g., in the DAV:lockdiscovery property). One use case for making lock tokens readable is so that a long-lived lock can be removed by the resource owner (the client that obtained the lock might have crashed or disconnected before cleaning up the lock). Except for the case of using UNLOCK under user guidance, a client SHOULD NOT use a lock token created by another client instance.
This specification encourages servers to create Universally Unique Identifiers (UUIDs) for lock tokens, and to use the URI form defined by "A Universally Unique Identifier (UUID) URN Namespace" ([RFC4122]). However, servers are free to use any URI (e.g., from another scheme) so long as it meets the uniqueness requirements. For example, a valid lock token might be constructed using the "opaquelocktoken" scheme defined in Appendix C.
Example: "urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6"
A lock MAY have a limited lifetime. The lifetime is suggested by the client when creating or refreshing the lock, but the server ultimately chooses the timeout value. Timeout is measured in seconds remaining until lock expiration.
The timeout counter MUST be restarted if a refresh lock request is successful (see Section 9.10.2). The timeout counter SHOULD NOT be restarted at any other time.
If the timeout expires, then the lock SHOULD be removed. In this case the server SHOULD act as if an UNLOCK method was executed by the server on the resource using the lock token of the timed-out lock, performed with its override authority.
Servers are advised to pay close attention to the values submitted by clients, as they will be indicative of the type of activity the client intends to perform. For example, an applet running in a browser may need to lock a resource, but because of the instability of the environment within which the applet is running, the applet may be turned off without warning. As a result, the applet is likely to ask for a relatively small timeout value so that if the applet dies, the lock can be quickly harvested. However, a document management system is likely to ask for an extremely long timeout because its user may be planning on going offline.
A client MUST NOT assume that just because the timeout has expired, the lock has immediately been removed.
Likewise, a client MUST NOT assume that just because the timeout has not expired, the lock still exists. Clients MUST assume that locks can arbitrarily disappear at any time, regardless of the value given in the Timeout header. The Timeout header only indicates the behavior of the server if extraordinary circumstances do not occur. For example, a sufficiently privileged user may remove a lock at any time, or the system may crash in such a way that it loses the record of the lock's existence.
Since server lock support is optional, a client trying to lock a resource on a server can either try the lock and hope for the best, or perform some form of discovery to determine what lock capabilities the server supports. This is known as lock capability discovery. A client can determine what lock types the server supports by retrieving the DAV:supportedlock property.
Any DAV-compliant resource that supports the LOCK method MUST support the DAV:supportedlock property.
If another principal locks a resource that a principal wishes to access, it is useful for the second principal to be able to find out who the first principal is. For this purpose the DAV:lockdiscovery property is provided. This property lists all outstanding locks, describes their type, and MAY even provide the lock tokens.
Any DAV-compliant resource that supports the LOCK method MUST support the DAV:lockdiscovery property.
This section describes the semantics specific to the write lock type. The write lock is a specific instance of a lock type, and is the only lock type described in this specification.
An exclusive write lock protects a resource: it prevents changes by any principal other than the lock creator and in any case where the lock token is not submitted (e.g., by a client process other than the one holding the lock).
Clients MUST submit a lock-token they are authorized to use in any request that modifies a write-locked resource. The list of modifications covered by a write-lock include:
Of the methods defined in HTTP and WebDAV, PUT, POST, PROPPATCH, LOCK, UNLOCK, MOVE, COPY (for the destination resource), DELETE, and MKCOL are affected by write locks. All other HTTP/WebDAV methods defined so far -- GET in particular -- function independently of a write lock.
The next few sections describe in more specific terms how write locks interact with various operations.
While those without a write lock may not alter a property on a resource it is still possible for the values of live properties to change, even while locked, due to the requirements of their schemas. Only dead properties and live properties defined as lockable are guaranteed not to change while write locked.
Although the write locks provide some help in preventing lost updates, they cannot guarantee that updates will never be lost. Consider the following scenario:
Two clients A and B are interested in editing the resource 'index.html'. Client A is an HTTP client rather than a WebDAV client, and so does not know how to perform locking.
Client A doesn't lock the document, but does a GET, and begins editing.
Client B does LOCK, performs a GET and begins editing.
Client B finishes editing, performs a PUT, then an UNLOCK.
Client A performs a PUT, overwriting and losing all of B's changes.
There are several reasons why the WebDAV protocol itself cannot prevent this situation. First, it cannot force all clients to use locking because it must be compatible with HTTP clients that do not comprehend locking. Second, it cannot require servers to support locking because of the variety of repository implementations, some of which rely on reservations and merging rather than on locking. Finally, being stateless, it cannot enforce a sequence of operations like LOCK / GET / PUT / UNLOCK.
WebDAV servers that support locking can reduce the likelihood that clients will accidentally overwrite each other's changes by requiring clients to lock resources before modifying them. Such servers would effectively prevent HTTP 1.0 and HTTP 1.1 clients from modifying resources.
WebDAV clients can be good citizens by using a lock / retrieve / write /unlock sequence of operations (at least by default) whenever they interact with a WebDAV server that supports locking.
HTTP 1.1 clients can be good citizens, avoiding overwriting other clients' changes, by using entity tags in If-Match headers with any requests that would modify resources.
Information managers may attempt to prevent overwrites by implementing client-side procedures requiring locking before modifying WebDAV resources.
WebDAV provides the ability to send a LOCK request to an unmapped URL in order to reserve the name for use. This is a simple way to avoid the lost-update problem on the creation of a new resource (another way is to use If-None-Match header specified in Section 14.26 of [RFC2616]). It has the side benefit of locking the new resource immediately for use of the creator.
Note that the lost-update problem is not an issue for collections because MKCOL can only be used to create a collection, not to overwrite an existing collection. When trying to lock a collection upon creation, clients can attempt to increase the likelihood of getting the lock by pipelining the MKCOL and LOCK requests together (but because this doesn't convert two separate operations into one atomic operation, there's no guarantee this will work).
A successful lock request to an unmapped URL MUST result in the creation of a locked (non-collection) resource with empty content. Subsequently, a successful PUT request (with the correct lock token) provides the content for the resource. Note that the LOCK request has no mechanism for the client to provide Content-Type or Content-Language, thus the server will use defaults or empty values and rely on the subsequent PUT request for correct values.
A resource created with a LOCK is empty but otherwise behaves in every way as a normal resource. It behaves the same way as a resource created by a PUT request with an empty body (and where a Content-Type and Content-Language was not specified), followed by a LOCK request to the same resource. Following from this model, a locked empty resource:
The client is expected to update the locked empty resource shortly after locking it, using PUT and possibly PROPPATCH.
Alternatively and for backwards compatibility to [RFC2518], servers MAY implement Lock-Null Resources (LNRs) instead (see definition in Appendix D). Clients can easily interoperate both with servers that support the old model LNRs and the recommended model of "locked empty resources" by only attempting PUT after a LOCK to an unmapped URL, not MKCOL or GET, and by not relying on specific properties of LNRs.
There are two kinds of collection write locks. A depth-0 write lock on a collection protects the collection properties plus the internal member URLs of that one collection, while not protecting the content or properties of member resources (if the collection itself has any entity bodies, those are also protected). A depth-infinity write lock on a collection provides the same protection on that collection and also provides write lock protection on every member resource.
Expressed otherwise, a write lock of either kind protects any request that would create a new resource in a write locked collection, any request that would remove an internal member URL of a write locked collection, and any request that would change the segment name of any internal member.
Thus, a collection write lock protects all the following actions:
The collection's lock token is required in addition to the lock token on the internal member itself, if it is locked separately.
In addition, a depth-infinity lock affects all write operations to all members of the locked collection. With a depth-infinity lock, the resource identified by the root of the lock is directly locked, and all its members are indirectly locked.
If a depth-infinity write LOCK request is issued to a collection containing member URLs identifying resources that are currently locked in a manner that conflicts with the new lock (see Section 6.1, point 3), the request MUST fail with a 423 (Locked) status code, and the response SHOULD contain the 'no-conflicting-lock' precondition.
If a lock request causes the URL of a resource to be added as an internal member URL of a depth-infinity locked collection, then the new resource MUST be automatically protected by the lock. For example, if the collection /a/b/ is write locked and the resource /c is moved to /a/b/c, then resource /a/b/c will be added to the write lock.
A user agent has to demonstrate knowledge of a lock when requesting an operation on a locked resource. Otherwise, the following scenario might occur. In the scenario, program A, run by User A, takes out a write lock on a resource. Program B, also run by User A, has no knowledge of the lock taken out by program A, yet performs a PUT to the locked resource. In this scenario, the PUT succeeds because locks are associated with a principal, not a program, and thus program B, because it is acting with principal A's credential, is allowed to perform the PUT. However, had program B known about the lock, it would not have overwritten the resource, preferring instead to present a dialog box describing the conflict to the user. Due to this scenario, a mechanism is needed to prevent different programs from accidentally ignoring locks taken out by other programs with the same authorization.
In order to prevent these collisions, a lock token MUST be submitted by an authorized principal for all locked resources that a method may change or the method MUST fail. A lock token is submitted when it appears in an If header. For example, if a resource is to be moved and both the source and destination are locked, then two lock tokens must be submitted in the If header, one for the source and the other for the destination.
>>Request
COPY /~fielding/index.html HTTP/1.1
Host: www.example.com
Destination: http://www.example.com/users/f/fielding/index.html
If: <http://www.example.com/users/f/fielding/index.html>
(<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>)
>>Response
HTTP/1.1 204 No Content
In this example, even though both the source and destination are locked, only one lock token must be submitted (the one for the lock on the destination). This is because the source resource is not modified by a COPY, and hence unaffected by the write lock. In this example, user agent authentication has previously occurred via a mechanism outside the scope of the HTTP protocol, in the underlying transport layer.
Consider a collection "/locked" with an exclusive, depth-infinity write lock, and an attempt to delete an internal member "/locked/member":
>>Request
DELETE /locked/member HTTP/1.1 Host: example.com
>>Response
HTTP/1.1 423 Locked
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:error xmlns:D="DAV:">
<D:lock-token-submitted>
<D:href>/locked/</D:href>
</D:lock-token-submitted>
</D:error>
Thus, the client would need to submit the lock token with the request to make it succeed. To do that, various forms of the If header (see Section 10.4) could be used.
"No-Tag-List" format:
If: (<urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf>)
"Tagged-List" format, for "http://example.com/locked/":
If: <http://example.com/locked/>
(<urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf>)
"Tagged-List" format, for "http://example.com/locked/member":
If: <http://example.com/locked/member>
(<urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf>)
Note that, for the purpose of submitting the lock token, the actual form doesn't matter; what's relevant is that the lock token appears in the If header, and that the If header itself evaluates to true.
A COPY method invocation MUST NOT duplicate any write locks active on the source. However, as previously noted, if the COPY copies the resource into a collection that is locked with a depth-infinity lock, then the resource will be added to the lock.
A successful MOVE request on a write locked resource MUST NOT move the write lock with the resource. However, if there is an existing lock at the destination, the server MUST add the moved resource to the destination lock scope. For example, if the MOVE makes the resource a child of a collection that has a depth-infinity lock, then the resource will be added to that collection's lock. Additionally, if a resource with a depth-infinity lock is moved to a destination that is within the scope of the same lock (e.g., within the URL namespace tree covered by the lock), the moved resource will again be added to the lock. In both these examples, as specified in Section 7.5, an If header must be submitted containing a lock token for both the source and destination.
A client MUST NOT submit the same write lock request twice. Note that a client is always aware it is resubmitting the same lock request because it must include the lock token in the If header in order to make the request for a resource that is already locked.
However, a client may submit a LOCK request with an If header but without a body. A server receiving a LOCK request with no body MUST NOT create a new lock -- this form of the LOCK request is only to be used to "refresh" an existing lock (meaning, at minimum, that any timers associated with the lock MUST be reset).
Clients may submit Timeout headers of arbitrary value with their lock refresh requests. Servers, as always, may ignore Timeout headers submitted by the client, and a server MAY refresh a lock with a timeout period that is different than the previous timeout period used for the lock, provided it advertises the new value in the LOCK refresh response.
If an error is received in response to a refresh LOCK request, the client MUST NOT assume that the lock was refreshed.
Servers MUST return authorization errors in preference to other errors. This avoids leaking information about protected resources (e.g., a client that finds that a hidden resource exists by seeing a 423 Locked response to an anonymous request to the resource).
In HTTP/1.1, method parameter information was exclusively encoded in HTTP headers. Unlike HTTP/1.1, WebDAV encodes method parameter information either in an XML ([REC-XML]) request entity body, or in an HTTP header. The use of XML to encode method parameters was motivated by the ability to add extra XML elements to existing structures, providing extensibility; and by XML's ability to encode information in ISO 10646 character sets, providing internationalization support.
In addition to encoding method parameters, XML is used in WebDAV to encode the responses from methods, providing the extensibility and internationalization advantages of XML for method output, as well as input.
When XML is used for a request or response body, the Content-Type type SHOULD be application/xml. Implementations MUST accept both text/xml and application/xml in request and response bodies. Use of text/xml is deprecated.
All DAV-compliant clients and resources MUST use XML parsers that are compliant with [REC-XML] and [REC-XML-NAMES]. All XML used in either requests or responses MUST be, at minimum, well formed and use namespaces correctly. If a server receives XML that is not well-formed, then the server MUST reject the entire request with a 400 (Bad Request). If a client receives XML that is not well-formed in a response, then the client MUST NOT assume anything about the outcome of the executed method and SHOULD treat the server as malfunctioning.
Note that processing XML submitted by an untrusted source may cause risks connected to privacy, security, and service quality (see Section 20). Servers MAY reject questionable requests (even though they consist of well-formed XML), for instance, with a 400 (Bad Request) status code and an optional response body explaining the problem.
URLs appear in many places in requests and responses. Interoperability experience with [RFC2518] showed that many clients parsing Multi-Status responses did not fully implement the full Reference Resolution defined in Section 5 of [RFC3986]. Thus, servers in particular need to be careful in handling URLs in responses, to ensure that clients have enough context to be able to interpret all the URLs. The rules in this section apply not only to resource URLs in the 'href' element in Multi-Status responses, but also to the Destination and If header resource URLs.
The sender has a choice between two approaches: using a relative reference, which is resolved against the Request-URI, or a full URI. A server MUST ensure that every 'href' value within a Multi-Status response uses the same format.
WebDAV only uses one form of relative reference in its extensions, the absolute path.
Simple-ref = absolute-URI | ( path-absolute [ "?" query ] )
The absolute-URI, path-absolute and query productions are defined in Sections 4.3, 3.3, and 3.4 of [RFC3986].
Within Simple-ref productions, senders MUST NOT:
Identifiers for collections SHOULD end in a '/' character.
Consider the collection http://example.com/sample/ with the internal member URL http://example.com/sample/a%20test and the PROPFIND request below:
>>Request:
PROPFIND /sample/ HTTP/1.1 Host: example.com Depth: 1
In this case, the server should return two 'href' elements containing either
Note that even though the server may be storing the member resource internally as 'a test', it has to be percent-encoded when used inside a URI reference (see Section 2.1 of [RFC3986]). Also note that a legal URI may still contain characters that need to be escaped within XML character data, such as the ampersand character.
Some of these new methods do not define bodies. Servers MUST examine all requests for a body, even when a body was not expected. In cases where a request body is present but would be ignored by a server, the server MUST reject the request with 415 (Unsupported Media Type). This informs the client (which may have been attempting to use an extension) that the body could not be processed as the client intended.
HTTP defines many headers that can be used in WebDAV requests and responses. Not all of these are appropriate in all situations and some interactions may be undefined. Note that HTTP 1.1 requires the Date header in all responses if possible (see Section 14.18, [RFC2616]).
The server MUST do authorization checks before checking any HTTP conditional header.
HTTP 1.1 recommends the use of ETags rather than modification dates, for cache control, and there are even stronger reasons to prefer ETags for authoring. Correct use of ETags is even more important in a distributed authoring environment, because ETags are necessary along with locks to avoid the lost-update problem. A client might fail to renew a lock, for example, when the lock times out and the client is accidentally offline or in the middle of a long upload. When a client fails to renew the lock, it's quite possible the resource can still be relocked and the user can go on editing, as long as no changes were made in the meantime. ETags are required for the client to be able to distinguish this case. Otherwise, the client is forced to ask the user whether to overwrite the resource on the server without even being able to tell the user if it has changed. Timestamps do not solve this problem nearly as well as ETags.
Strong ETags are much more useful for authoring use cases than weak ETags (see Section 13.3.3 of [RFC2616]). Semantic equivalence can be a useful concept but that depends on the document type and the application type, and interoperability might require some agreement or standard outside the scope of this specification and HTTP. Note also that weak ETags have certain restrictions in HTTP, e.g., these cannot be used in If-Match headers.
Note that the meaning of an ETag in a PUT response is not clearly defined either in this document or in RFC 2616 (i.e., whether the ETag means that the resource is octet-for-octet equivalent to the body of the PUT request, or whether the server could have made minor changes in the formatting or content of the document upon storage). This is an HTTP issue, not purely a WebDAV issue.
Because clients may be forced to prompt users or throw away changed content if the ETag changes, a WebDAV server SHOULD NOT change the ETag (or the Last-Modified time) for a resource that has an unchanged body and location. The ETag represents the state of the body or contents of the resource. There is no similar way to tell if properties have changed.
HTTP and WebDAV did not use the bodies of most error responses for machine-parsable information until the specification for Versioning Extensions to WebDAV introduced a mechanism to include more specific information in the body of an error response (Section 1.6 of [RFC3253]). The error body mechanism is appropriate to use with any error response that may take a body but does not already have a body defined. The mechanism is particularly appropriate when a status code can mean many things (for example, 400 Bad Request can mean required headers are missing, headers are incorrectly formatted, or much more). This error body mechanism is covered in Section 16.
Note that the HTTP response headers "Etag" and "Last-Modified" (see [RFC2616], Sections 14.19 and 14.29) are defined per URL (not per resource), and are used by clients for caching. Therefore servers must ensure that executing any operation that affects the URL namespace (such as COPY, MOVE, DELETE, PUT, or MKCOL) does preserve their semantics, in particular:
In practice this means that servers
Note that these considerations also apply to specific use cases, such as using PUT to create a new resource at a URL that has been mapped before, but has been deleted since then.
Finally, WebDAV properties (such as DAV:getetag and DAV: getlastmodified) that inherit their semantics from HTTP headers must behave accordingly.
The PROPFIND method retrieves properties defined on the resource identified by the Request-URI, if the resource does not have any internal members, or on the resource identified by the Request-URI and potentially its member resources, if the resource is a collection that has internal member URLs. All DAV-compliant resources MUST support the PROPFIND method and the propfind XML element (Section 14.20) along with all XML elements defined for use with that element.
A client MUST submit a Depth header with a value of "0", "1", or "infinity" with a PROPFIND request. Servers MUST support "0" and "1" depth requests on WebDAV-compliant resources and SHOULD support "infinity" requests. In practice, support for infinite-depth requests MAY be disabled, due to the performance and security concerns associated with this behavior. Servers SHOULD treat a request without a Depth header as if a "Depth: infinity" header was included.
A client may submit a 'propfind' XML element in the body of the request method describing what information is being requested. It is possible to:
A client may choose not to submit a request body. An empty PROPFIND request body MUST be treated as if it were an 'allprop' request.
Note that 'allprop' does not return values for all live properties. WebDAV servers increasingly have expensively-calculated or lengthy properties (see [RFC3253] and [RFC3744]) and do not return all properties already. Instead, WebDAV clients can use propname requests to discover what live properties exist, and request named properties when retrieving values. For a live property defined elsewhere, that definition can specify whether or not that live property would be returned in 'allprop' requests.
All servers MUST support returning a response of content type text/xml or application/xml that contains a multistatus XML element that describes the results of the attempts to retrieve the various properties.
If there is an error retrieving a property, then a proper error result MUST be included in the response. A request to retrieve the value of a property that does not exist is an error and MUST be noted with a 'response' XML element that contains a 404 (Not Found) status value.
Consequently, the 'multistatus' XML element for a collection resource MUST include a 'response' XML element for each member URL of the collection, to whatever depth was requested. It SHOULD NOT include any 'response' elements for resources that are not WebDAV-compliant. Each 'response' element MUST contain an 'href' element that contains the URL of the resource on which the properties in the prop XML element are defined. Results for a PROPFIND on a collection resource are returned as a flat list whose order of entries is not significant. Note that a resource may have only one value for a property of a given name, so the property may only show up once in PROPFIND responses.
Properties may be subject to access control. In the case of 'allprop' and 'propname' requests, if a principal does not have the right to know whether a particular property exists, then the property MAY be silently excluded from the response.
Some PROPFIND results MAY be cached, with care, as there is no cache validation mechanism for most properties. This method is both safe and idempotent (see Section 9.1 of [RFC2616]).
This section, as with similar sections for other methods, provides some guidance on error codes and preconditions or postconditions (defined in Section 16) that might be particularly useful with PROPFIND.
403 Forbidden - A server MAY reject PROPFIND requests on collections with depth header of "Infinity", in which case it SHOULD use this error with the precondition code 'propfind-finite-depth' inside the error body.
In PROPFIND responses, information about individual properties is returned inside 'propstat' elements (see Section 14.22), each containing an individual 'status' element containing information about the properties appearing in it. The list below summarizes the most common status codes used inside 'propstat'; however, clients should be prepared to handle other 2/3/4/5xx series status codes as well.
200 OK - A property exists and/or its value is successfully returned.
401 Unauthorized - The property cannot be viewed without appropriate authorization.
403 Forbidden - The property cannot be viewed regardless of authentication.
404 Not Found - The property does not exist.
>>Request
PROPFIND /file HTTP/1.1
Host: www.example.com
Content-type: application/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:propfind xmlns:D="DAV:">
<D:prop xmlns:R="http://ns.example.com/boxschema/">
<R:bigbox/>
<R:author/>
<R:DingALing/>
<R:Random/>
</D:prop>
</D:propfind>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:">
<D:response xmlns:R="http://ns.example.com/boxschema/">
<D:href>http://www.example.com/file</D:href>
<D:propstat>
<D:prop>
<R:bigbox>
<R:BoxType>Box type A</R:BoxType>
</R:bigbox>
<R:author>
<R:Name>J.J. Johnson</R:Name>
</R:author>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop><R:DingALing/><R:Random/></D:prop>
<D:status>HTTP/1.1 403 Forbidden</D:status>
<D:responsedescription> The user does not have access to the
DingALing property.
</D:responsedescription>
</D:propstat>
</D:response>
<D:responsedescription> There has been an access violation error.
</D:responsedescription>
</D:multistatus>
In this example, PROPFIND is executed on a non-collection resource http://www.example.com/file. The propfind XML element specifies the name of four properties whose values are being requested. In this case, only two properties were returned, since the principal issuing the request did not have sufficient access rights to see the third and fourth properties.
>>Request
PROPFIND /container/ HTTP/1.1
Host: www.example.com
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<propfind xmlns="DAV:">
<propname/>
</propfind>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<multistatus xmlns="DAV:">
<response>
<href>http://www.example.com/container/</href>
<propstat>
<prop xmlns:R="http://ns.example.com/boxschema/">
<R:bigbox/>
<R:author/>
<creationdate/>
<displayname/>
<resourcetype/>
<supportedlock/>
</prop>
<status>HTTP/1.1 200 OK</status>
</propstat>
</response>
<response>
<href>http://www.example.com/container/front.html</href>
<propstat>
<prop xmlns:R="http://ns.example.com/boxschema/">
<R:bigbox/>
<creationdate/>
<displayname/>
<getcontentlength/>
<getcontenttype/>
<getetag/>
<getlastmodified/>
<resourcetype/>
<supportedlock/>
</prop>
<status>HTTP/1.1 200 OK</status>
</propstat>
</response>
</multistatus>
In this example, PROPFIND is invoked on the collection resource http://www.example.com/container/, with a propfind XML element containing the propname XML element, meaning the name of all properties should be returned. Since no Depth header is present, it assumes its default value of "infinity", meaning the name of the properties on the collection and all its descendants should be returned.
Consistent with the previous example, resource http://www.example.com/container/ has six properties defined on it: bigbox and author in the "http://ns.example.com/boxschema/" namespace, and creationdate, displayname, resourcetype, and supportedlock in the "DAV:" namespace.
The resource http://www.example.com/container/index.html, a member of the "container" collection, has nine properties defined on it, bigbox in the "http://ns.example.com/boxschema/" namespace and creationdate, displayname, getcontentlength, getcontenttype, getetag, getlastmodified, resourcetype, and supportedlock in the "DAV:" namespace.
This example also demonstrates the use of XML namespace scoping and the default namespace. Since the "xmlns" attribute does not contain a prefix, the namespace applies by default to all enclosed elements. Hence, all elements that do not explicitly state the namespace to which they belong are members of the "DAV:" namespace.
Note that 'allprop', despite its name, which remains for backward-compatibility, does not return every property, but only dead properties and the live properties defined in this specification.
>>Request
PROPFIND /container/ HTTP/1.1
Host: www.example.com
Depth: 1
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:propfind xmlns:D="DAV:">
<D:allprop/>
</D:propfind>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>/container/</D:href>
<D:propstat>
<D:prop xmlns:R="http://ns.example.com/boxschema/">
<R:bigbox><R:BoxType>Box type A</R:BoxType></R:bigbox>
<R:author><R:Name>Hadrian</R:Name></R:author>
<D:creationdate>1997-12-01T17:42:21-08:00</D:creationdate>
<D:displayname>Example collection</D:displayname>
<D:resourcetype><D:collection/></D:resourcetype>
<D:supportedlock>
<D:lockentry>
<D:lockscope><D:exclusive/></D:lockscope>
<D:locktype><D:write/></D:locktype>
</D:lockentry>
<D:lockentry>
<D:lockscope><D:shared/></D:lockscope>
<D:locktype><D:write/></D:locktype>
</D:lockentry>
</D:supportedlock>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/container/front.html</D:href>
<D:propstat>
<D:prop xmlns:R="http://ns.example.com/boxschema/">
<R:bigbox><R:BoxType>Box type B</R:BoxType>
</R:bigbox>
<D:creationdate>1997-12-01T18:27:21-08:00</D:creationdate>
<D:displayname>Example HTML resource</D:displayname>
<D:getcontentlength>4525</D:getcontentlength>
<D:getcontenttype>text/html</D:getcontenttype>
<D:getetag>"zzyzx"</D:getetag>
<D:getlastmodified
>Mon, 12 Jan 1998 09:25:56 GMT</D:getlastmodified>
<D:resourcetype/>
<D:supportedlock>
<D:lockentry>
<D:lockscope><D:exclusive/></D:lockscope>
<D:locktype><D:write/></D:locktype>
</D:lockentry>
<D:lockentry>
<D:lockscope><D:shared/></D:lockscope>
<D:locktype><D:write/></D:locktype>
</D:lockentry>
</D:supportedlock>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propst