HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)

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.¶

   <R:title xmlns:R="http://www.example.com/ns/"></R:title>

• [namespace name]
• [local name]
• [attributes] named "xml:lang" or any such attribute in scope
• [children] of type element or character

• [namespace name]
• [local name]
• [attributes]
• [children] of type element or character

• [namespace name]
• [local name]
• [normalized value]

• [character code]

• [prefix]

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.¶

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.¶

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.¶

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.¶

1. A lock either directly or indirectly locks a resource.
2. A resource becomes directly locked when a LOCK request to a URL of that resource creates a new lock. The "lock-root" of the new lock is that URL. If at the time of the request, the URL is not mapped to a resource, a new empty resource is created and directly locked.
3. An exclusive lock (Section 6.2) conflicts with any other kind of lock on the same resource, whether either lock is direct or indirect. A server MUST NOT create conflicting locks on a resource.
4. For a collection that is locked with a depth-infinity lock L, all member resources are indirectly locked. Changes in membership of such a collection affect the set of indirectly locked resources:
   • If a member resource is added to the collection, the new member resource MUST NOT already have a conflicting lock, because the new resource MUST become indirectly locked by L.
   • If a member resource stops being a member of the collection, then the resource MUST no longer be indirectly locked by L.
5. Each lock is identified by a single globally unique lock token (Section 6.5).
6. An UNLOCK request deletes the lock with the specified lock token. After a lock is deleted, no resource is locked by that lock.
7. A lock token is "submitted" in a request when it appears in an "If" header (Section 7, "Write Lock", discusses when token submission is required for write locks).
8. If a request causes the lock-root of any lock to become an unmapped URL, then the lock MUST also be deleted by that request.

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.¶

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.¶

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.¶

• Can be read, deleted, moved, and copied, and in all ways behaves as a regular non-collection resource.
• Appears as a member of its parent collection.
• SHOULD NOT disappear when its lock goes away (clients must therefore be responsible for cleaning up their own mess, as with any other operation or any non-empty resource).
• MAY NOT have values for properties like DAV:getcontentlanguage that haven't been specified yet by the client.
• Can be updated (have content added) with a PUT request.
• MUST NOT be converted into a collection. The server MUST fail a MKCOL request (as it would with a MKCOL request to any existing non-collection resource).
• MUST have defined values for DAV:lockdiscovery and DAV:supportedlock properties.
• The response MUST indicate that a resource was created, by use of the "201 Created" response code (a LOCK request to an existing resource instead will result in 200 OK). The body must still include the DAV:lockdiscovery property, as with a LOCK request to an existing 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.¶

• DELETE a collection's direct internal member,
• MOVE an internal member out of the collection,
• MOVE an internal member into the collection,
• MOVE to rename an internal member within a collection,
• COPY an internal member into a collection, and
• PUT or MKCOL request that would create a new internal member.

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.¶

• Any new resource added as a descendant of a depth-infinity locked collection becomes indirectly locked.
• Any indirectly locked resource moved out of the locked collection into an unlocked collection is thereafter unlocked.
• Any indirectly locked resource moved out of a locked source collection into a depth-infinity locked target collection remains indirectly locked but is now protected by the lock on the target collection (the target collection's lock token will thereafter be required to make further changes).

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.¶

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.¶

   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: ¶

• use dot-segments ("." or ".."), or
• have prefixes that do not match the Request-URI (using the comparison rules defined in Section 3.2.3 of [RFC2616]).

Identifiers for collections SHOULD end in a '/' 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.¶

• For any given URL, the "Last-Modified" value MUST increment every time the representation returned upon GET changes (within the limits of timestamp resolution).
• For any given URL, an "ETag" value MUST NOT be reused for different representations returned by GET.

In practice this means that servers¶

• might have to increment "Last-Modified" timestamps for every resource inside the destination namespace of a namespace operation unless it can do so more selectively, and
• similarly, might have to re-assign "ETag" values for these resources (unless the server allocates entity tags in a way so that they are unique across the whole URL namespace managed by the server).

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.¶

• Request particular property values, by naming the properties desired within the 'prop' element (the ordering of properties in here MAY be ignored by the server),
• Request property values for those properties defined in this specification (at a minimum) plus dead properties, by using the 'allprop' element (the 'include' element can be used with 'allprop' to instruct the server to also include additional live properties that may not have been returned otherwise),
• Request a list of names of all the properties defined on the resource, by using the 'propname' element.

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]).¶

The PROPPATCH method processes instructions specified in the request body to set and/or remove properties defined on the resource identified by the Request-URI.¶

All DAV-compliant resources MUST support the PROPPATCH method and MUST process instructions that are specified using the propertyupdate, set, and remove XML elements. Execution of the directives in this method is, of course, subject to access control constraints. DAV-compliant resources SHOULD support the setting of arbitrary dead properties.¶

The request message body of a PROPPATCH method MUST contain the propertyupdate XML element.¶

Servers MUST process PROPPATCH instructions in document order (an exception to the normal rule that ordering is irrelevant). Instructions MUST either all be executed or none executed. Thus, if any error occurs during processing, all executed instructions MUST be undone and a proper error result returned. Instruction processing details can be found in the definition of the set and remove instructions in Sections 14.23 and 14.26.¶

If a server attempts to make any of the property changes in a PROPPATCH request (i.e., the request is not rejected for high-level errors before processing the body), the response MUST be a Multi-Status response as described in Section 9.2.1.¶

This method is idempotent, but not safe (see Section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.¶

MKCOL creates a new collection resource at the location specified by the Request-URI. If the Request-URI is already mapped to a resource, then the MKCOL MUST fail. During MKCOL processing, a server MUST make the Request-URI an internal member of its parent collection, unless the Request-URI is "/". If no such ancestor exists, the method MUST fail. When the MKCOL operation creates a new collection resource, all ancestors MUST already exist, or the method MUST fail with a 409 (Conflict) status code. For example, if a request to create collection /a/b/c/d/ is made, and /a/b/c/ does not exist, the request must fail.¶

When MKCOL is invoked without a request body, the newly created collection SHOULD have no members.¶

A MKCOL request message may contain a message body. The precise behavior of a MKCOL request when the body is present is undefined, but limited to creating collections, members of a collection, bodies of members, and properties on the collections or members. If the server receives a MKCOL request entity type it does not support or understand, it MUST respond with a 415 (Unsupported Media Type) status code. If the server decides to reject the request based on the presence of an entity or the type of an entity, it should use the 415 (Unsupported Media Type) status code.¶

This method is idempotent, but not safe (see Section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.¶

The semantics of GET are unchanged when applied to a collection, since GET is defined as, "retrieve whatever information (in the form of an entity) is identified by the Request-URI" [RFC2616]. GET, when applied to a collection, may return the contents of an "index.html" resource, a human-readable view of the contents of the collection, or something else altogether. Hence, it is possible that the result of a GET on a collection will bear no correlation to the membership of the collection.¶

Similarly, since the definition of HEAD is a GET without a response message body, the semantics of HEAD are unmodified when applied to collection resources.¶

Since by definition the actual function performed by POST is determined by the server and often depends on the particular resource, the behavior of POST when applied to collections cannot be meaningfully modified because it is largely undefined. Thus, the semantics of POST are unmodified when applied to a collection.¶

DELETE is defined in [RFC2616], Section 9.7, to "delete the resource identified by the Request-URI". However, WebDAV changes some DELETE handling requirements.¶

A server processing a successful DELETE request: ¶

• MUST destroy locks rooted on the deleted resource
• MUST remove the mapping from the Request-URI to any resource.

Thus, after a successful DELETE operation (and in the absence of other actions), a subsequent GET/HEAD/PROPFIND request to the target Request-URI MUST return 404 (Not Found).

The COPY method creates a duplicate of the source resource identified by the Request-URI, in the destination resource identified by the URI in the Destination header. The Destination header MUST be present. The exact behavior of the COPY method depends on the type of the source resource.¶

All WebDAV-compliant resources MUST support the COPY method. However, support for the COPY method does not guarantee the ability to copy a resource. For example, separate programs may control resources on the same server. As a result, it may not be possible to copy a resource to a location that appears to be on the same server.¶

This method is idempotent, but not safe (see Section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.¶

The MOVE operation on a non-collection resource is the logical equivalent of a copy (COPY), followed by consistency maintenance processing, followed by a delete of the source, where all three actions are performed in a single operation. The consistency maintenance step allows the server to perform updates caused by the move, such as updating all URLs, other than the Request-URI that identifies the source resource, to point to the new destination resource.¶

The Destination header MUST be present on all MOVE methods and MUST follow all COPY requirements for the COPY part of the MOVE method. All WebDAV-compliant resources MUST support the MOVE method.¶

Support for the MOVE method does not guarantee the ability to move a resource to a particular destination. For example, separate programs may actually control different sets of resources on the same server. Therefore, it may not be possible to move a resource within a namespace that appears to belong to the same server.¶

If a resource exists at the destination, the destination resource will be deleted as a side-effect of the MOVE operation, subject to the restrictions of the Overwrite header.¶

This method is idempotent, but not safe (see Section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.¶

The following sections describe the LOCK method, which is used to take out a lock of any access type and to refresh an existing lock. These sections on the LOCK method describe only those semantics that are specific to the LOCK method and are independent of the access type of the lock being requested.¶

Any resource that supports the LOCK method MUST, at minimum, support the XML request and response formats defined herein.¶

This method is neither idempotent nor safe (see Section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.¶

The UNLOCK method removes the lock identified by the lock token in the Lock-Token request header. The Request-URI MUST identify a resource within the scope of the lock.¶

Note that use of the Lock-Token header to provide the lock token is not consistent with other state-changing methods, which all require an If header with the lock token. Thus, the If header is not needed to provide the lock token. Naturally, when the If header is present, it has its normal meaning as a conditional header.¶

For a successful response to this method, the server MUST delete the lock entirely.¶

If all resources that have been locked under the submitted lock token cannot be unlocked, then the UNLOCK request MUST fail.¶

A successful response to an UNLOCK method does not mean that the resource is necessarily unlocked. It means that the specific lock corresponding to the specified token no longer exists.¶

Any DAV-compliant resource that supports the LOCK method MUST support the UNLOCK method.¶

This method is idempotent, but not safe (see Section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.¶

  DAV              = "DAV" ":" #( compliance-class ) 
  compliance-class = ( "1" | "2" | "3" | extend ) 
  extend           = Coded-URL | token 
                     ; token is defined in RFC 2616, Section 2.2
  Coded-URL        = "<" absolute-URI ">" 
                     ; No linear whitespace (LWS) allowed in Coded-URL
                     ; absolute-URI defined in RFC 3986, Section 4.3 

This general-header appearing in the response indicates that the resource supports the DAV schema and protocol as specified. All DAV-compliant resources MUST return the DAV header with compliance-class "1" on all OPTIONS responses. In cases where WebDAV is only supported in part of the server namespace, an OPTIONS request to non-WebDAV resources (including "/") SHOULD NOT advertise WebDAV support.¶

The value is a comma-separated list of all compliance class identifiers that the resource supports. Class identifiers may be Coded-URLs or tokens (as defined by [RFC2616]). Identifiers can appear in any order. Identifiers that are standardized through the IETF RFC process are tokens, but other identifiers SHOULD be Coded-URLs to encourage uniqueness.¶

A resource must show class 1 compliance if it shows class 2 or 3 compliance. In general, support for one compliance class does not entail support for any other, and in particular, support for compliance class 3 does not require support for compliance class 2. Please refer to Section 18 for more details on compliance classes defined in this specification.¶

Note that many WebDAV servers do not advertise WebDAV support in response to "OPTIONS *".¶

As a request header, this header allows the client to advertise compliance with named features when the server needs that information. Clients SHOULD NOT send this header unless a standards track specification requires it. Any extension that makes use of this as a request header will need to carefully consider caching implications.¶

   Depth = "Depth" ":" ("0" | "1" | "infinity")

The Depth request header is used with methods executed on resources that could potentially have internal members to indicate whether the method is to be applied only to the resource ("Depth: 0"), to the resource and its internal members only ("Depth: 1"), or the resource and all its members ("Depth: infinity").¶

The Depth header is only supported if a method's definition explicitly provides for such support.¶

The following rules are the default behavior for any method that supports the Depth header. A method may override these defaults by defining different behavior in its definition.¶

Methods that support the Depth header may choose not to support all of the header's values and may define, on a case-by-case basis, the behavior of the method if a Depth header is not present. For example, the MOVE method only supports "Depth: infinity", and if a Depth header is not present, it will act as if a "Depth: infinity" header had been applied.¶

Clients MUST NOT rely upon methods executing on members of their hierarchies in any particular order or on the execution being atomic unless the particular method explicitly provides such guarantees.¶

Upon execution, a method with a Depth header will perform as much of its assigned task as possible and then return a response specifying what it was able to accomplish and what it failed to do.¶

So, for example, an attempt to COPY a hierarchy may result in some of the members being copied and some not.¶

By default, the Depth header does not interact with other headers. That is, each header on a request with a Depth header MUST be applied only to the Request-URI if it applies to any resource, unless specific Depth behavior is defined for that header.¶

If a source or destination resource within the scope of the Depth header is locked in such a way as to prevent the successful execution of the method, then the lock token for that resource MUST be submitted with the request in the If request header.¶

The Depth header only specifies the behavior of the method with regards to internal members. If a resource does not have internal members, then the Depth header MUST be ignored.¶

The Destination request header specifies the URI that identifies a destination resource for methods such as COPY and MOVE, which take two URIs as parameters.¶

   Destination = "Destination" ":" Simple-ref

If the Destination value is an absolute-URI (Section 4.3 of [RFC3986]), it may name a different server (or different port or scheme). If the source server cannot attempt a copy to the remote server, it MUST fail the request. Note that copying and moving resources to remote servers is not fully defined in this specification (e.g., specific error conditions).¶

If the Destination value is too long or otherwise unacceptable, the server SHOULD return 400 (Bad Request), ideally with helpful information in an error body.¶

The If request header is intended to have similar functionality to the If-Match header defined in Section 14.24 of [RFC2616]. However, the If header handles any state token as well as ETags. A typical example of a state token is a lock token, and lock tokens are the only state tokens defined in this specification.¶

   Lock-Token = "Lock-Token" ":" Coded-URL

The Lock-Token request header is used with the UNLOCK method to identify the lock to be removed. The lock token in the Lock-Token request header MUST identify a lock that contains the resource identified by Request-URI as a member.¶

The Lock-Token response header is used with the LOCK method to indicate the lock token created as a result of a successful LOCK request to create a new lock.¶

   Overwrite = "Overwrite" ":" ("T" | "F")

The Overwrite request header specifies whether the server should overwrite a resource mapped to the destination URL during a COPY or MOVE. A value of "F" states that the server must not perform the COPY or MOVE operation if the destination URL does map to a resource. If the overwrite header is not included in a COPY or MOVE request, then the resource MUST treat the request as if it has an overwrite header of value "T". While the Overwrite header appears to duplicate the functionality of using an "If-Match: *" header (see [RFC2616]), If-Match applies only to the Request-URI, and not to the Destination of a COPY or MOVE.¶

If a COPY or MOVE is not performed due to the value of the Overwrite header, the method MUST fail with a 412 (Precondition Failed) status code. The server MUST do authorization checks before checking this or any conditional header.¶

All DAV-compliant resources MUST support the Overwrite header.¶

   TimeOut = "Timeout" ":" 1#TimeType 
   TimeType = ("Second-" DAVTimeOutVal | "Infinite")  
              ; No LWS allowed within TimeType
   DAVTimeOutVal = 1*DIGIT

Clients MAY include Timeout request headers in their LOCK requests. However, the server is not required to honor or even consider these requests. Clients MUST NOT submit a Timeout request header with any method other than a LOCK method.¶

The "Second" TimeType specifies the number of seconds that will elapse between granting of the lock at the server, and the automatic removal of the lock. The timeout value for TimeType "Second" MUST NOT be greater than 2³²-1.¶

See Section 6.6 for a description of lock timeout behavior.¶

The 207 (Multi-Status) status code provides status for multiple independent operations (see Section 13 for more information).¶

The 422 (Unprocessable Entity) status code means the server understands the content type of the request entity (hence a 415(Unsupported Media Type) status code is inappropriate), and the syntax of the request entity is correct (thus a 400 (Bad Request) status code is inappropriate) but was unable to process the contained instructions. For example, this error condition may occur if an XML request body contains well-formed (i.e., syntactically correct), but semantically erroneous, XML instructions.¶

The 423 (Locked) status code means the source or destination resource of a method is locked. This response SHOULD contain an appropriate precondition or postcondition code, such as 'lock-token-submitted' or 'no-conflicting-lock'.¶

The 424 (Failed Dependency) status code means that the method could not be performed on the resource because the requested action depended on another action and that action failed. For example, if a command in a PROPPATCH method fails, then, at minimum, the rest of the commands will also fail with 424 (Failed Dependency).¶

The 507 (Insufficient Storage) status code means the method could not be performed on the resource because the server is unable to store the representation needed to successfully complete the request. This condition is considered to be temporary. If the request that received this status code was the result of a user action, the request MUST NOT be repeated until it is requested by a separate user action.¶

Any request can contain a conditional header defined in HTTP (If-Match, If-Modified-Since, etc.) or the "If" or "Overwrite" conditional headers defined in this specification. If the server evaluates a conditional header, and if that condition fails to hold, then this error code MUST be returned. On the other hand, if the client did not include a conditional header in the request, then the server MUST NOT use this status code.¶

This status code is used in HTTP 1.1 only for Request-URIs, not URIs in other locations.¶

HTTP defines the Location header to indicate a preferred URL for the resource that was addressed in the Request-URI (e.g., in response to successful PUT requests or in redirect responses). However, use of this header creates ambiguity when there are URLs in the body of the response, as with Multi-Status. Thus, use of the Location header with the Multi-Status response is intentionally undefined.¶

Redirect responses (300-303, 305, and 307) defined in HTTP 1.1 normally take a Location header to indicate the new URI for the single resource redirected from the Request-URI. Multi-Status responses contain many resource addresses, but the original definition in [RFC2518] did not have any place for the server to provide the new URI for redirected resources. This specification does define a 'location' element for this information (see Section 14.9). Servers MUST use this new element with redirect responses in Multi-Status.¶

Clients encountering redirected resources in Multi-Status MUST NOT rely on the 'location' element being present with a new URI. If the element is not present, the client MAY reissue the request to the individual redirected resource, because the response to that request can be redirected with a Location header containing the new URI.¶

Sections 9.2.1, 9.1.2, 9.6.1, 9.8.3, and 9.9.2 define various status codes used in Multi-Status responses. This specification does not define the meaning of other status codes that could appear in these responses.¶

Name:

activelock

Purpose:

Describes a lock on a resource.

<!ELEMENT activelock (lockscope, locktype, depth, owner?, timeout?, 
          locktoken?, lockroot)>

Name:

allprop

Purpose:

Specifies that all names and values of dead properties and the live properties defined by this document existing on the resource are to be returned.

<!ELEMENT allprop EMPTY >

Name:

collection

Purpose:

Identifies the associated resource as a collection. The DAV:resourcetype property of a collection resource MUST contain this element. It is normally empty but extensions may add sub-elements.

<!ELEMENT collection EMPTY > 

Name:

depth

Purpose:

Used for representing depth values in XML content (e.g., in lock information).

Value:

"0" | "1" | "infinity"

<!ELEMENT depth (#PCDATA) >

Name:

error

Purpose:

Error responses, particularly 403 Forbidden and 409 Conflict, sometimes need more information to indicate what went wrong. In these cases, servers MAY return an XML response body with a document element of 'error', containing child elements identifying particular condition codes.

Description:

Contains at least one XML element, and MUST NOT contain text or mixed content. Any element that is a child of the 'error' element is considered to be a precondition or postcondition code. Unrecognized elements MUST be ignored.

<!ELEMENT error ANY >

Name:

exclusive

Purpose:

Specifies an exclusive lock.

<!ELEMENT exclusive EMPTY >

Name:

href

Purpose:

MUST contain a URI or a relative reference.

Description:

There may be limits on the value of 'href' depending on the context of its use. Refer to the specification text where 'href' is used to see what limitations apply in each case.

Value:

Simple-ref

<!ELEMENT href (#PCDATA)>

Name:

include

Purpose:

Any child element represents the name of a property to be included in the PROPFIND response. All elements inside an 'include' XML element MUST define properties related to the resource, although possible property names are in no way limited to those property names defined in this document or other standards. This element MUST NOT contain text or mixed content.

<!ELEMENT include ANY >

Name:

location

Purpose:

HTTP defines the "Location" header (see [RFC2616], Section 14.30) for use with some status codes (such as 201 and the 300 series codes). When these codes are used inside a 'multistatus' element, the 'location' element can be used to provide the accompanying Location header value.

Description:

Contains a single href element with the same value that would be used in a Location header.

<!ELEMENT location (href)>

Name:

lockentry

Purpose:

Defines the types of locks that can be used with the resource.

<!ELEMENT lockentry (lockscope, locktype) >

Name:

lockinfo

Purpose:

The 'lockinfo' XML element is used with a LOCK method to specify the type of lock the client wishes to have created.

<!ELEMENT lockinfo (lockscope, locktype, owner?)  >

Name:

lockroot

Purpose:

Contains the root URL of the lock, which is the URL through which the resource was addressed in the LOCK request.

Description:

The href element contains the root of the lock. The server SHOULD include this in all DAV:lockdiscovery property values and the response to LOCK requests.

<!ELEMENT lockroot (href) >

Name:

lockscope

Purpose:

Specifies whether a lock is an exclusive lock, or a shared lock.

<!ELEMENT lockscope (exclusive | shared) >

Name:

locktoken

Purpose:

The lock token associated with a lock.

Description:

The href contains a single lock token URI, which refers to the lock.

<!ELEMENT locktoken (href) >

Name:

locktype

Purpose:

Specifies the access type of a lock. At present, this specification only defines one lock type, the write lock.

<!ELEMENT locktype (write) >

Name:

multistatus

Purpose:

Contains multiple response messages.

Description:

The 'responsedescription' element at the top level is used to provide a general message describing the overarching nature of the response. If this value is available, an application may use it instead of presenting the individual response descriptions contained within the responses.

<!ELEMENT multistatus (response*, responsedescription?)  >

Name:

owner

Purpose:

Holds client-supplied information about the creator of a lock.

Description:

Allows a client to provide information sufficient for either directly contacting a principal (such as a telephone number or Email URI), or for discovering the principal (such as the URL of a homepage) who created a lock. The value provided MUST be treated as a dead property in terms of XML Information Item preservation. The server MUST NOT alter the value unless the owner value provided by the client is empty. For a certain amount of interoperability between different client implementations, if clients have URI-formatted contact information for the lock creator suitable for user display, then clients SHOULD put those URIs in 'href' child elements of the 'owner' element.

Extensibility:

MAY be extended with child elements, mixed content, text content or attributes.

<!ELEMENT owner ANY >

Name:

prop

Purpose:

Contains properties related to a resource.

Description:

A generic container for properties defined on resources. All elements inside a 'prop' XML element MUST define properties related to the resource, although possible property names are in no way limited to those property names defined in this document or other standards. This element MUST NOT contain text or mixed content.

<!ELEMENT prop ANY >

Name:

propertyupdate

Purpose:

Contains a request to alter the properties on a resource.

Description:

This XML element is a container for the information required to modify the properties on the resource.

<!ELEMENT propertyupdate (remove | set)+ >

Name:

propfind

Purpose:

Specifies the properties to be returned from a PROPFIND method. Four special elements are specified for use with 'propfind': 'prop', 'allprop', 'include', and 'propname'. If 'prop' is used inside 'propfind', it MUST NOT contain property values.

<!ELEMENT propfind ( propname | (allprop, include?) | prop ) >

Name:

propname

Purpose:

Specifies that only a list of property names on the resource is to be returned.

<!ELEMENT propname EMPTY >

Name:

propstat

Purpose:

Groups together a prop and status element that is associated with a particular 'href' element.

Description:

The propstat XML element MUST contain one prop XML element and one status XML element. The contents of the prop XML element MUST only list the names of properties to which the result in the status element applies. The optional precondition/postcondition element and 'responsedescription' text also apply to the properties named in 'prop'.

<!ELEMENT propstat (prop, status, error?, responsedescription?) >

Name:

remove

Purpose:

Lists the properties to be removed from a resource.

Description:

Remove instructs that the properties specified in prop should be removed. Specifying the removal of a property that does not exist is not an error. All the XML elements in a 'prop' XML element inside of a 'remove' XML element MUST be empty, as only the names of properties to be removed are required.

<!ELEMENT remove (prop) >

Name:

response

Purpose:

Holds a single response describing the effect of a method on resource and/or its properties.

Description:

The 'href' element contains an HTTP URL pointing to a WebDAV resource when used in the 'response' container. A particular 'href' value MUST NOT appear more than once as the child of a 'response' XML element under a 'multistatus' XML element. This requirement is necessary in order to keep processing costs for a response to linear time. Essentially, this prevents having to search in order to group together all the responses by 'href'. There are, however, no requirements regarding ordering based on 'href' values. The optional precondition/postcondition element and 'responsedescription' text can provide additional information about this resource relative to the request or result.

<!ELEMENT response (href, ((href*, status)|(propstat+)), 
                    error?, responsedescription? , location?) >

Name:

responsedescription

Purpose:

Contains information about a status response within a Multi-Status.

Description:

Provides information suitable to be presented to a user.

<!ELEMENT responsedescription (#PCDATA) >

Name:

set

Purpose:

Lists the property values to be set for a resource.

Description:

The 'set' element MUST contain only a 'prop' element. The elements contained by the 'prop' element inside the 'set' element MUST specify the name and value of properties that are set on the resource identified by Request-URI. If a property already exists, then its value is replaced. Language tagging information appearing in the scope of the 'prop' element (in the "xml:lang" attribute, if present) MUST be persistently stored along with the property, and MUST be subsequently retrievable using PROPFIND.

<!ELEMENT set (prop) >

Name:

shared

Purpose:

Specifies a shared lock.

<!ELEMENT shared EMPTY >

Name:

status

Purpose:

Holds a single HTTP status-line.

Value:

status-line (defined in Section 6.1 of [RFC2616])

<!ELEMENT status (#PCDATA) >

Name:

timeout

Purpose:

The number of seconds remaining before a lock expires.

Value:

TimeType (defined in Section 10.7)

   <!ELEMENT timeout (#PCDATA) >

Name:

write

Purpose:

Specifies a write lock.

<!ELEMENT write EMPTY >

Name:

creationdate

Purpose:

Records the time and date the resource was created.

Value:

date-time (defined in [RFC3339], see the ABNF in Section 5.6.)

Protected:

MAY be protected. Some servers allow DAV:creationdate to be changed to reflect the time the document was created if that is more meaningful to the user (rather than the time it was uploaded). Thus, clients SHOULD NOT use this property in synchronization logic (use DAV:getetag instead).

COPY/MOVE behavior:

This property value SHOULD be kept during a MOVE operation, but is normally re-initialized when a resource is created with a COPY. It should not be set in a COPY.

Description:

The DAV:creationdate property SHOULD be defined on all DAV compliant resources. If present, it contains a timestamp of the moment when the resource was created. Servers that are incapable of persistently recording the creation date SHOULD instead leave it undefined (i.e. report "Not Found").

<!ELEMENT creationdate (#PCDATA) >

Name:

displayname

Purpose:

Provides a name for the resource that is suitable for presentation to a user.

Value:

Any text.

Protected:

SHOULD NOT be protected. Note that servers implementing [RFC2518] might have made this a protected property as this is a new requirement.

COPY/MOVE behavior:

This property value SHOULD be preserved in COPY and MOVE operations.

Description:

Contains a description of the resource that is suitable for presentation to a user. This property is defined on the resource, and hence SHOULD have the same value independent of the Request-URI used to retrieve it (thus, computing this property based on the Request-URI is deprecated). While generic clients might display the property value to end users, client UI designers must understand that the method for identifying resources is still the URL. Changes to DAV:displayname do not issue moves or copies to the server, but simply change a piece of meta-data on the individual resource. Two resources can have the same DAV:displayname value even within the same collection.

<!ELEMENT displayname (#PCDATA) >

Name:

getcontentlanguage

Purpose:

Contains the Content-Language header value (from Section 14.12 of [RFC2616]) as it would be returned by a GET without accept headers.

Value:

language-tag (language-tag is defined in Section 3.10 of [RFC2616])

Protected:

SHOULD NOT be protected, so that clients can reset the language. Note that servers implementing [RFC2518] might have made this a protected property as this is a new requirement.

COPY/MOVE behavior:

This property value SHOULD be preserved in COPY and MOVE operations.

Description:

The DAV:getcontentlanguage property MUST be defined on any DAV-compliant resource that returns the Content-Language header on a GET.

<!ELEMENT getcontentlanguage (#PCDATA) >

Name:

getcontentlength

Purpose:

Contains the Content-Length header returned by a GET without accept headers.

Value:

See Section 14.13 of [RFC2616].

Protected:

This property is computed, therefore protected.

Description:

The DAV:getcontentlength property MUST be defined on any DAV-compliant resource that returns the Content-Length header in response to a GET.

COPY/MOVE behavior:

This property value is dependent on the size of the destination resource, not the value of the property on the source resource.

<!ELEMENT getcontentlength (#PCDATA) >

Name:

getcontenttype

Purpose:

Contains the Content-Type header value (from Section 14.17 of [RFC2616]) as it would be returned by a GET without accept headers.

Value:

media-type (defined in Section 3.7 of [RFC2616])

Protected:

Potentially protected if the server prefers to assign content types on its own (see also discussion in Section 9.7.1).

COPY/MOVE behavior:

This property value SHOULD be preserved in COPY and MOVE operations.

Description:

This property MUST be defined on any DAV-compliant resource that returns the Content-Type header in response to a GET.

<!ELEMENT getcontenttype (#PCDATA) >

Name:

getetag

Purpose:

Contains the ETag header value (from Section 14.19 of [RFC2616]) as it would be returned by a GET without accept headers.

Value:

entity-tag (defined in Section 3.11 of [RFC2616])

Protected:

MUST be protected because this value is created and controlled by the server.

COPY/MOVE behavior:

This property value is dependent on the final state of the destination resource, not the value of the property on the source resource. Also note the considerations in Section 8.8.

Description:

The getetag property MUST be defined on any DAV-compliant resource that returns the Etag header. Refer to Section 3.11 of RFC 2616 for a complete definition of the semantics of an ETag, and to Section 8.6 for a discussion of ETags in WebDAV.

<!ELEMENT getetag (#PCDATA) >

Name:

getlastmodified

Purpose:

Contains the Last-Modified header value (from Section 14.29 of [RFC2616]) as it would be returned by a GET method without accept headers.

Value:

rfc1123-date (defined in Section 3.3.1 of [RFC2616])

Protected:

SHOULD be protected because some clients may rely on the value for appropriate caching behavior, or on the value of the Last-Modified header to which this property is linked.

COPY/MOVE behavior:

This property value is dependent on the last modified date of the destination resource, not the value of the property on the source resource. Note that some server implementations use the file system date modified value for the DAV:getlastmodified value, and this can be preserved in a MOVE even when the HTTP Last-Modified value SHOULD change. Note that since [RFC2616] requires clients to use ETags where provided, a server implementing ETags can count on clients using a much better mechanism than modification dates for offline synchronization or cache control. Also note the considerations in Section 8.8.

Description:

The last-modified date on a resource SHOULD only reflect changes in the body (the GET responses) of the resource. A change in a property only SHOULD NOT cause the last-modified date to change, because clients MAY rely on the last-modified date to know when to overwrite the existing body. The DAV:getlastmodified property MUST be defined on any DAV-compliant resource that returns the Last-Modified header in response to a GET.

<!ELEMENT getlastmodified (#PCDATA) >

Name:

lockdiscovery

Purpose:

Describes the active locks on a resource

Protected:

MUST be protected. Clients change the list of locks through LOCK and UNLOCK, not through PROPPATCH.

COPY/MOVE behavior:

The value of this property depends on the lock state of the destination, not on the locks of the source resource. Recall that locks are not moved in a MOVE operation.

Description:

Returns a listing of who has a lock, what type of lock he has, the timeout type and the time remaining on the timeout, and the associated lock token. Owner information MAY be omitted if it is considered sensitive. If there are no locks, but the server supports locks, the property will be present but contain zero 'activelock' elements. If there are one or more locks, an 'activelock' element appears for each lock on the resource. This property is NOT lockable with respect to write locks (Section 7).

<!ELEMENT lockdiscovery (activelock)* >

Name:

resourcetype

Purpose:

Specifies the nature of the resource.

Protected:

SHOULD be protected. Resource type is generally decided through the operation creating the resource (MKCOL vs PUT), not by PROPPATCH.

COPY/MOVE behavior:

Generally a COPY/MOVE of a resource results in the same type of resource at the destination.

Description:

MUST be defined on all DAV-compliant resources. Each child element identifies a specific type the resource belongs to, such as 'collection', which is the only resource type defined by this specification (see Section 14.3). If the element contains the 'collection' child element plus additional unrecognized elements, it should generally be treated as a collection. If the element contains no recognized child elements, it should be treated as a non-collection resource. The default value is empty. This element MUST NOT contain text or mixed content. Any custom child element is considered to be an identifier for a resource type.

Example: (fictional example to show extensibility)

    <x:resourcetype xmlns:x="DAV:"> 
        <x:collection/> 
        <f:search-results xmlns:f="http://www.example.com/ns"/> 
    </x:resourcetype> 

Name:

supportedlock

Purpose:

To provide a listing of the lock capabilities supported by the resource.

Protected:

MUST be protected. Servers, not clients, determine what lock mechanisms are supported.

COPY/MOVE behavior:

This property value is dependent on the kind of locks supported at the destination, not on the value of the property at the source resource. Servers attempting to COPY to a destination should not attempt to set this property at the destination.

Description:

Returns a listing of the combinations of scope and access types that may be specified in a lock request on the resource. Note that the actual contents are themselves controlled by access controls, so a server is not required to provide information the client is not authorized to see. This property is NOT lockable with respect to write locks (Section 7).

<!ELEMENT supportedlock (lockentry)* >

A class 1 compliant resource MUST meet all "MUST" requirements in all sections of this document.¶

Class 1 compliant resources MUST return, at minimum, the value "1" in the DAV header on all responses to the OPTIONS method.¶

A class 2 compliant resource MUST meet all class 1 requirements and support the LOCK method, the DAV:supportedlock property, the DAV:lockdiscovery property, the Time-Out response header and the Lock-Token request header. A class 2 compliant resource SHOULD also support the Timeout request header and the 'owner' XML element.¶

Class 2 compliant resources MUST return, at minimum, the values "1" and "2" in the DAV header on all responses to the OPTIONS method.¶

A resource can explicitly advertise its support for the revisions to [RFC2518] made in this document. Class 1 MUST be supported as well. Class 2 MAY be supported. Advertising class 3 support in addition to class 1 and 2 means that the server supports all the requirements in this specification. Advertising class 3 and class 1 support, but not class 2, means that the server supports all the requirements in this specification except possibly those that involve locking support.¶

Example:

         DAV: 1, 3

Due to their emphasis on authoring, WebDAV servers need to use authentication technology to protect not just access to a network resource, but the integrity of the resource as well. Furthermore, the introduction of locking functionality requires support for authentication.¶

A password sent in the clear over an insecure channel is an inadequate means for protecting the accessibility and integrity of a resource as the password may be intercepted. Since Basic authentication for HTTP/1.1 performs essentially clear text transmission of a password, Basic authentication MUST NOT be used to authenticate a WebDAV client to a server unless the connection is secure. Furthermore, a WebDAV server MUST NOT send a Basic authentication challenge in a WWW-Authenticate header unless the connection is secure. An example of a secure connection would be a Transport Layer Security (TLS) connection employing a strong cipher suite and server authentication.¶

WebDAV applications MUST support the Digest authentication scheme [RFC2617]. Since Digest authentication verifies that both parties to a communication know a shared secret, a password, without having to send that secret in the clear, Digest authentication avoids the security problems inherent in Basic authentication while providing a level of authentication that is useful in a wide range of scenarios.¶

Denial-of-service attacks are of special concern to WebDAV servers. WebDAV plus HTTP enables denial-of-service attacks on every part of a system's resources.¶

• The underlying storage can be attacked by PUTting extremely large files.
• Asking for recursive operations on large collections can attack processing time.
• Making multiple pipelined requests on multiple connections can attack network connections.

WebDAV servers need to be aware of the possibility of a denial-of-service attack at all levels. The proper response to such an attack MAY be to simply drop the connection. Or, if the server is able to make a response, the server MAY use a 400-level status request such as 400 (Bad Request) and indicate why the request was refused (a 500-level status response would indicate that the problem is with the server, whereas unintentional DoS attacks are something the client is capable of remedying).¶

WebDAV provides, through the PROPFIND method, a mechanism for listing the member resources of a collection. This greatly diminishes the effectiveness of security or privacy techniques that rely only on the difficulty of discovering the names of network resources. Users of WebDAV servers are encouraged to use access control techniques to prevent unwanted access to resources, rather than depending on the relative obscurity of their resource names.¶

When submitting a lock request, a user agent may also submit an 'owner' XML field giving contact information for the person taking out the lock (for those cases where a person, rather than a robot, is taking out the lock). This contact information is stored in a DAV:lockdiscovery property on the resource, and can be used by other collaborators to begin negotiation over access to the resource. However, in many cases, this contact information can be very private, and should not be widely disseminated. Servers SHOULD limit read access to the DAV:lockdiscovery property as appropriate. Furthermore, user agents SHOULD provide control over whether contact information is sent at all, and if contact information is sent, control over exactly what information is sent.¶

Since property values are typically used to hold information such as the author of a document, there is the possibility that privacy concerns could arise stemming from widespread access to a resource's property data. To reduce the risk of inadvertent release of private information via properties, servers are encouraged to develop access control mechanisms that separate read access to the resource body and read access to the resource's properties. This allows a user to control the dissemination of their property data without overly restricting access to the resource's contents.¶

XML supports a facility known as "external entities", defined in Section 4.2.2 of [REC-XML], which instructs an XML processor to retrieve and include additional XML. An external XML entity can be used to append or modify the document type declaration (DTD) associated with an XML document. An external XML entity can also be used to include XML within the content of an XML document. For non-validating XML, such as the XML used in this specification, including an external XML entity is not required by XML. However, XML does state that an XML processor may, at its discretion, include the external XML entity.¶

External XML entities have no inherent trustworthiness and are subject to all the attacks that are endemic to any HTTP GET request. Furthermore, it is possible for an external XML entity to modify the DTD, and hence affect the final form of an XML document, in the worst case, significantly modifying its semantics or exposing the XML processor to the security risks discussed in [RFC3023]. Therefore, implementers must be aware that external XML entities should be treated as untrustworthy. If a server chooses not to handle external XML entities, it SHOULD respond to requests containing external entities with the 'no-external-entities' condition code.¶

There is also the scalability risk that would accompany a widely deployed application that made use of external XML entities. In this situation, it is possible that there would be significant numbers of requests for one external XML entity, potentially overloading any server that fields requests for the resource containing the external XML entity.¶

Furthermore, there's also a risk based on the evaluation of "internal entities" as defined in Section 4.2.2 of [REC-XML]. A small, carefully crafted request using nested internal entities may require enormous amounts of memory and/or processing time to process. Server implementers should be aware of this risk and configure their XML parsers so that requests like these can be detected and rejected as early as possible.¶

This specification encourages the use of "A Universally Unique Identifier (UUID) URN Namespace" ([RFC4122]) for lock tokens (Section 6.5), in order to guarantee their uniqueness across space and time. Version 1 UUIDs (defined in Section 4) MAY contain a "node" field that "consists of an IEEE 802 MAC address, usually the host address. For systems with multiple IEEE addresses, any available one can be used". Since a WebDAV server will issue many locks over its lifetime, the implication is that it may also be publicly exposing its IEEE 802 address.¶

• It is possible to track the movement of hardware from subnet to subnet.
• It may be possible to identify the manufacturer of the hardware running a WebDAV server.
• It may be possible to determine the number of each type of computer running WebDAV.

This risk only applies to host-address-based UUID versions. Section 4 of [RFC4122] describes several other mechanisms for generating UUIDs that do not involve the host address and therefore do not suffer from this risk.¶

HTTP has the ability to host programs that are executed on client machines. These programs can take many forms including Web scripts, executables, plug-in modules, and macros in documents. WebDAV does not change any of the security concerns around these programs, yet often WebDAV is used in contexts where a wide range of users can publish documents on a server. The server might not have a close trust relationship with the author that is publishing the document. Servers that allow clients to publish arbitrary content can usefully implement precautions to check that content published to the server is not harmful to other clients. Servers could do this by techniques such as restricting the types of content that is allowed to be published and running virus and malware detection software on published content. Servers can also mitigate the risk by having appropriate access restriction and authentication of users that are allowed to publish content to the server.¶

This specification defines two URI schemes: ¶

1. the "opaquelocktoken" scheme defined in Appendix C, and
2. the "DAV" URI scheme, which historically was used in [RFC2518] to disambiguate WebDAV property and XML element names and which continues to be used for that purpose in this specification and others extending WebDAV. Creation of identifiers in the "DAV:" namespace is controlled by the IETF.

Note that defining new URI schemes for XML namespaces is now discouraged. "DAV:" was defined before standard best practices emerged.¶

XML namespaces disambiguate WebDAV property names and XML elements. Any WebDAV user or application can define a new namespace in order to create custom properties or extend WebDAV XML syntax. IANA does not need to manage such namespaces, property names, or element names.¶

The message header fields below should be added to the permanent registry (see [RFC3864]).¶

This specification defines the HTTP status codes ¶

• 207 Multi-Status (Section 11.1)
• 422 Unprocessable Entity (Section 11.2),
• 423 Locked (Section 11.3),
• 424 Failed Dependency (Section 11.4) and
• 507 Insufficient Storage (Section 11.5),

to be updated in the registry at <http://www.iana.org/assignments/http-status-codes>.

XML supports two mechanisms for indicating that an XML element does not have any content. The first is to declare an XML element of the form <A></A>. The second is to declare an XML element of the form <A/>. The two XML elements are semantically identical.¶

XML is a flexible data format that makes it easy to submit data that appears legal but in fact is not. The philosophy of "Be flexible in what you accept and strict in what you send" still applies, but it must not be applied inappropriately. XML is extremely flexible in dealing with issues of whitespace, element ordering, inserting new elements, etc. This flexibility does not require extension, especially not in the area of the meaning of elements.¶

There is no kindness in accepting illegal combinations of XML elements. At best, it will cause an unwanted result and at worst it can cause real damage.¶

The following request body for a PROPFIND method is illegal.¶

   <?xml version="1.0" encoding="utf-8" ?> 
   <D:propfind xmlns:D="DAV:"> 
    <D:allprop/> 
    <D:propname/> 
   </D:propfind> 

The definition of the propfind element only allows for the allprop or the propname element, not both. Thus, the above is an error and must be responded to with a 400 (Bad Request).¶

Imagine, however, that a server wanted to be "kind" and decided to pick the allprop element as the true element and respond to it. A client running over a bandwidth limited line who intended to execute a propname would be in for a big surprise if the server treated the command as an allprop.¶

Additionally, if a server were lenient and decided to reply to this request, the results would vary randomly from server to server, with some servers executing the allprop directive, and others executing the propname directive. This reduces interoperability rather than increasing it.¶

The previous example was illegal because it contained two elements that were explicitly banned from appearing together in the propfind element. However, XML is an extensible language, so one can imagine new elements being defined for use with propfind. Below is the request body of a PROPFIND and, like the previous example, must be rejected with a 400 (Bad Request) by a server that does not understand the expired-props element.¶

   <?xml version="1.0" encoding="utf-8" ?> 
   <D:propfind xmlns:D="DAV:" 
   xmlns:E="http://www.example.com/standards/props/"> 
    <E:expired-props/> 
   </D:propfind> 

To understand why a 400 (Bad Request) is returned, let us look at the request body as the server unfamiliar with expired-props sees it.¶

   <?xml version="1.0" encoding="utf-8" ?> 
   <D:propfind xmlns:D="DAV:"   
               xmlns:E="http://www.example.com/standards/props/"> 
   </D:propfind> 

As the server does not understand the 'expired-props' element, according to the WebDAV-specific XML processing rules specified in Section 17, it must process the request as if the element were not there. Thus, the server sees an empty propfind, which by the definition of the propfind element is illegal.¶

   <?xml version="1.0" encoding="utf-8" ?> 
   <D:propfind xmlns:D="DAV:"  
               xmlns:E="http://www.example.com/standards/props/"> 
    <D:propname/> 
    <E:leave-out>*boss*</E:leave-out> 
   </D:propfind> 

The previous example contains the fictitious element leave-out. Its purpose is to prevent the return of any property whose name matches the submitted pattern. If the previous example were submitted to a server unfamiliar with 'leave-out', the only result would be that the 'leave-out' element would be ignored and a propname would be executed.¶

A WebDAV client implemented to this specification might find servers that create lock-null resources (implemented before this specification using [RFC2518]) as well as servers that create locked empty resources. The response to the LOCK request will not indicate what kind of resource was created. There are a few techniques that help the client deal with either type.¶

• If the client wishes to avoid accidentally creating either lock-null or empty locked resources, an "If-Match: *" header can be included with LOCK requests to prevent the server from creating a new resource.
• If a LOCK request creates a resource and the client subsequently wants to overwrite that resource using a COPY or MOVE request, the client should include an "Overwrite: T" header.
• If a LOCK request creates a resource and the client then decides to get rid of that resource, a DELETE request is supposed to fail on a lock-null resource and UNLOCK should be used instead. But with a locked empty resource, UNLOCK doesn't make the resource disappear. Therefore, the client might have to try both requests and ignore an error in one of the two requests.

Collections and Namespace Operations ¶

• The semantics of PROPFIND 'allprop' (Section 9.1) have been relaxed so that servers return results including, at a minimum, the live properties defined in this specification, but not necessarily return other live properties. The 'allprop' directive therefore means something more like "return all properties that are supposed to be returned when 'allprop' is requested" -- a set of properties that may include custom properties and properties defined in other specifications if those other specifications so require. Related to this, 'allprop' requests can now be extended with the 'include' syntax to include specific named properties, thereby avoiding additional requests due to changed 'allprop' semantics.
• Servers are now allowed to reject PROPFIND requests with Depth:Infinity. Clients that used this will need to be able to do a series of Depth:1 requests instead.
• Multi-Status response bodies now can transport the value of HTTP's Location response header in the new 'location' element. Clients may use this to avoid additional roundtrips to the server when there is a 'response' element with a 3xx status (see Section 14.24).
• The definition of COPY has been relaxed so that it doesn't require servers to first delete the target resources anymore (this was a known incompatibility with [RFC3253]). See Section 9.8.

Headers and Marshalling ¶

• The Destination and If request headers now allow absolute paths in addition to full URIs (see Section 8.3). This may be useful for clients operating through a reverse proxy that does rewrite the Host request header, but not WebDAV-specific headers.
• This specification adopts the error marshalling extensions and the "precondition/postcondition" terminology defined in [RFC3253] (see Section 16). Related to that, it adds the "error" XML element inside multistatus response bodies (see Section 14.5, however note that it uses a format different from the one recommended in RFC 3253).
• Senders and recipients are now required to support the UTF-16 character encoding in XML message bodies (see Section 19).
• Clients are now required to send the Depth header on PROPFIND requests, although servers are still encouraged to support clients that don't.

Locking ¶

• RFC 2518's concept of "lock-null resources" (LNRs) has been replaced by a simplified approach, the "locked empty resources" (see Section 7.3). There are some aspects of lock-null resources clients cannot rely on anymore, namely, the ability to use them to create a locked collection or the fact that they disappear upon UNLOCK when no PUT or MKCOL request was issued. Note that servers are still allowed to implement LNRs as per RFC 2518.
• There is no implicit refresh of locks anymore. Locks are only refreshed upon explicit request (see Section 9.10.2).
• Clarified that the DAV:owner value supplied in the LOCK request must be preserved by the server just like a dead property (Section 14.17). Also added the DAV:lockroot element (Section 14.12), which allows clients to discover the root of lock.

Collections and Namespace Operations ¶

• Due to interoperability problems, allowable formats for contents of 'href' elements in multistatus responses have been limited (see Section 8.3).
• Due to lack of implementation, support for the 'propertybehavior' request body for COPY and MOVE has been removed. Instead, requirements for property preservation have been clarified (see Sections 9.8 and 9.9).

Properties ¶

• Strengthened server requirements for storage of property values, in particular persistence of language information (xml:lang), whitespace, and XML namespace information (see Section 4.3).
• Clarified requirements on which properties should be writable by the client; in particular, setting "DAV:displayname" should be supported by servers (see Section 15).
• Only 'rfc1123-date' productions are legal as values for DAV:getlastmodified (see Section 15.7).

Headers and Marshalling ¶

• Servers are now required to do authorization checks before processing conditional headers (see Section 8.5).

Locking ¶

• Strengthened requirement to check identity of lock creator when accessing locked resources (see Section 6.4). Clients should be aware that lock tokens returned to other principals can only be used to break a lock, if at all.
• Section 8.10.4 of [RFC2518] incorrectly required servers to return a 409 status where a 207 status was really appropriate. This has been corrected (Section 9.10).

The definition of collection state has been fixed so it doesn't vary anymore depending on the Request-URI (see Section 5.2).¶

The DAV header now allows non-IETF extensions through URIs in addition to compliance class tokens. It also can now be used in requests, although this specification does not define any associated semantics for the compliance classes defined in here (see Section 10.1).¶

In RFC 2518, the definition of the Depth header (Section 9.2) required that, by default, request headers would be applied to each resource in scope. Based on implementation experience, the default has now been reversed (see Section 10.2).¶

The TimeType format used in the Timeout request header and the "timeout" XML element used to be extensible. Now, only the two formats defined by this specification are allowed (see Section 10.7).¶