HTTP Extensions for Distributed Authoring - WebDAV RFC2518 bis

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 read- only, 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 which allows a principal to identify a set of properties in which the principal is interested and to set or retrieve just those properties.¶

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 [11] 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.¶

The XML namespace extension [10] is also used in this specification in order to allow for new XML elements to be added without fear of colliding with other element names. Although WebDAV request and response bodies can be extended by arbitrary XML elements, which can be ignored by the message recipient, an XML element in the "DAV:" namespace SHOULD NOT be used in the request or response body unless that XML element is explicitly defined in an IETF RFC reviewed by a WebDAV working group.¶

Note that "DAV:" is a scheme name defined solely to provide a namespace for WebDAV XML elements and property names. This practice is discouraged in part because registration of new scheme names is difficult. "DAV:" was defined as the WebDAV namespace before standard best practices emerged, and this namespace is kept and still used because of significant existing deployments, but this should not be emulated.¶

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 new elements. Older clients will not break when they encounter extensions because they will still have the data specified in the original schema and will 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 a 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.¶

A property is always represented in XML with an XML element consisting of the property name. The simplest example is an empty property, which is different from a property that does not exist.¶

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

The value of a property appears inside the property name element. The value may be any kind of well-formed XML content, including both text-only and mixed content. When the property value contains further XML elements, namespaces that are in scope for that part of the XML document apply within the property value as well, and MUST be preserved in server storage for retransmission later. Namespace prefixes need not be preserved due to the rules of prefix declaration in XML.¶

Attributes on the property name element may convey information about the property, but are not considered part of the value. However, when language information appears in the 'xml:lang' attribute on the property name element, the language information MUST be preserved in server storage for retransmission later. Note that a property only has one value, in one language (or language MAY be left undefined), not multiple values in different languages or a single value in multiple languages.¶

The XML attribute xml:space MUST NOT be used to change white space handling. White space 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 [5], 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 which 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. 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 require 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.¶

Although implicit in RFC2616 [7] and RFC2396 [5], any resource, including collection resources, MAY be identified by more than one URI. For example, a resource could be identified by multiple HTTP URLs.¶

A collection is a resource whose state consists of at least a list of internal member URLs and a set of properties, but which may have additional state such as entity bodies returned by GET. An internal member URL MUST be immediately relative to a base URL of the collection. That is, the internal member URL is equal to a containing collection's URL plus an additional segment for non- collection resources, or additional segment plus trailing slash "/" for collection resources, where segment is defined in section 3.3 of RFC2396 [5].¶

Any given internal member URL MUST only belong to the collection once, i.e., it is illegal to have multiple instances of the same URL in a collection. Properties defined on collections behave exactly as do properties on non-collection resources.¶

For all WebDAV compliant resources A and B, identified by URLs U and V, for which U is immediately relative to V, B MUST be a collection that has U as an internal member URL. So, if the resource with URL http://example.com/bar/blah is WebDAV compliant and if the resource with URL http://example.com/bar/ is WebDAV compliant then the resource with URL http://example.com/bar/ must be a collection and must contain URL http://example.com/bar/blah as an internal member.¶

Collection resources MAY list the URLs of non-WebDAV compliant children in the HTTP URL namespace hierarchy as internal members but are not required to do so. For example, if the resource with URL http://example.com/bar/blah is not WebDAV compliant and the URL http://example.com/bar/ identifies a collection then URL http://example.com/bar/blah may or may not be an internal member of the collection with URL http://example.com/bar/.¶

If a WebDAV compliant resource has no WebDAV compliant children 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.bar/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.bar/blah/. Wherever a server produces a URL referring to a collection, the server MUST include the trailing slash. In general clients SHOULD use the "/" form of collection names.¶

Clients MUST be able to support the case where WebDAV resources are contained inside non-WebDAV resources. For example, if a 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.¶

The most basic form of lock is an exclusive lock. Only one exclusive lock may exist on any resource, whether it is directly or indirectly locked (Section 7.7). Exclusive locks avoid having to merge results, 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 with appropriate access can use the lock.¶

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 owner leaves without unlocking a resource. While both timeouts 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 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.¶

A lock token is a type of state token, represented as a URI, which identifies a particular lock. A lock token is returned in the Lock- Token header in the response to a successful LOCK operation. The lock token also appears in the value of the lockdiscovery property, the value of which is returned in the body of the response to a successful LOCK operation (this property also includes the tokens of other current locks on the resource). Finally, the lockdiscovery property can be queried using PROPFIND and the token can be discovered that way. Each lock has only one unique lock token.¶

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.¶

This specification provides a lock token URI scheme called opaquelocktoken that meets the uniqueness requirements. However resources are free to return any URI scheme so long as it meets the uniqueness requirements. According to current IETF best practices, implementations SHOULD use registered URI schemes to ensure uniqueness.¶

Submitting a lock token does not confer full privilege to use the lock token or modify the locked resource. Anyone can find out anyone else's lock token by performing lock discovery. Write access and other privileges MUST be enforced through normal privilege or authentication mechanisms, not based on the slight obscurity of lock token values.¶

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.¶

urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6¶

The 'opaquelocktoken' URI scheme extends the UUID mechanism slightly while still guaranteeing the lock token to be unique across all resources for all time. With the 'opaquelocktoken' scheme, the server MAY reuse a UUID with extension characters added. If the server does this then the algorithm generating the extensions MUST guarantee that the same extension will never be used twice with the associated UUID.¶

OpaqueLockToken-URI = "opaquelocktoken:" UUID [Extension] ; The UUID production is the string representation of a UUID. Note that white space (LWS) is not allowed between elements of this production.¶

Extension = path ; path is defined in section 3.3 of RFC2396 [5] ¶

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 supportedlock property.¶

Any DAV compliant resource that supports the LOCK method MUST support the 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 lockdiscovery property is provided. This property lists all outstanding locks, describes their type, and where available, provides their lock token.¶

Any DAV compliant resource that supports the LOCK method MUST support the lockdiscovery property.¶

A resource may be made available through more than one URI. However locks apply to resources, not URIs. Therefore a LOCK request on a resource MUST NOT succeed if can not be honored by all the URIs through which the resource is addressable.¶

The creator of the lock is the lock owner. The server MUST restrict the usage of the lock token to the lock owner (both for shared and exclusive locks -- for multi-user shared lock cases, each authenticated principal MUST obtain its own shared lock).¶

The server MAY allow privileged users other than the lock owner to destroy a lock (for example, the resource owner or an administrator) as a special case of lock usage.¶

If an anonymous user requests a lock, the server MAY refuse the request.¶

A server MUST reject any write request that alters a write-locked resource unless a valid lock token is provided. The write operations defined in HTTP and WebDAV are PUT, POST, PROPPATCH, LOCK, UNLOCK, MOVE, COPY (for the destination resource), DELETE, and MKCOL. All other HTTP/WebDAV methods, GET in particular, function independently of the lock. A shared write lock prevents the same operations, however it also allows access by any principal that has a shared write lock on the same resource.¶

Note, however, that as new methods are created it will be necessary to specify how they interact with a write lock.¶

A successful request for an exclusive or shared write lock MUST result in the generation of a unique lock token associated with the requesting principal. Thus if five principals have a shared write lock on the same resource there will be five lock tokens, one for each principal.¶

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 to respect locks 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.¶

It is possible to lock an unmapped URL in order to lock 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 HTTP 1.1). It has the side benefit of locking the new resource immediately for use of the creator.¶

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. In order to immediately lock a collection upon creation, clients may attempt to pipeline the MKCOL and LOCK requests together.¶

A lock request to an unmapped URL SHOULD result in the creation of an locked resource with empty content. A subsequent PUT request with the correct lock token SHOULD normally succeed, and this new request provides the content, content-type, content-language and other information as appropriate.¶

• Responds with a 404 or 405 to any DAV method except for PUT, MKCOL, OPTIONS, PROPFIND, LOCK, UNLOCK.
• Appears as a member of its parent collection.
• Disappears (URI becomes unmapped) if its lock goes away before it is converted to a regular resource. (This must also happen if it is renamed or moved, or if any parent collection is renamed or moved, because locks are tied to URLs).
• May be turned into a regular resource when a PUT request to the URL is successful. Ceases to be a lock-null resource.
• May be turned into a collection when a MKCOL request to the URL is successful. Ceases to be a lock-null resource.
• Has defined values for lockdiscovery and supportedlock properties.

• Can be read, deleted, moved, copied, and in all ways behave as a regular resource, not a lock-null 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)
• SHOULD default to having no content type.
• MAY NOT have values for properties like getcontentlanguage which haven't been specified yet by the client.
• May have content added with a PUT request. MUST be able to change content type.
• MUST NOT be turned into a collection. A MKCOL request must fail as it would to any existing resource.
• MUST have defined values for lockdiscovery and 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 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. When the client uses PUT to overwrite a locked empty resource the client MUST supply a Content-Type if any is known. If the client supplies a Content- Type value the server MUST set that value (this requirement actually applies to any resource that is overwritten but is particularly necessary for locked empty resources which are initially created with no Content-Type.¶

Clients can easily interoperate both with servers that support the deprecated lock-null resources and servers that support simpler locked empty resources by only attempting PUT after a LOCK to an unmapped URL, not MKCOL or GET.¶

A write lock on a collection, whether created by a "Depth: 0" or "Depth: infinity" lock request, prevents the addition or removal of member URLs of the collection by non-lock owners.¶

A zero-depth lock on a collection affects changes to the direct membership of that collection. When a principal issues a write request to create a new resource in a write locked collection, or isses a DELETE, MOVE or other request that would remove an existing internal member URL of a write locked collection or change the binding name, this request MUST fail if the principal does not provide the correct lock token for the locked collection.¶

• DELETE a collection's direct internal member
• MOVE a member out of the collection
• MOVE a member into the collection, unless it overwrites a pre- existing member
• MOVE to rename it within a collection,
• COPY a member into a collection, unless it overwrites a pre- existing member
• PUT or MKCOL request which would create a new 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 descendents of the locked collection. With a depth-infinity lock, the root of the lock is directly locked, and all its descendants are indirectly locked.¶

• Any new resource added as a descendent 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 within the scope of 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 which conflicts with the write lock, the request MUST fail with a 423 (Locked) status code, and the response SHOULD contain the 'missing-lock-token' precondition.¶

If a lock owner 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 added to the lock. This is the only mechanism that allows a resource to be added to a write lock. Thus, 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.¶

If a user agent is not required to have knowledge about a lock when requesting an operation on a locked resource, the following scenario might occur. 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 Aís 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.¶

Example - Write Lock

   
   >>Request 
    
     COPY /~fielding/index.html HTTP/1.1 
     Host: www.ics.uci.edu 
     Destination: http://www.ics.uci.edu/users/f/fielding/index.html 
     If: <http://www.ics.uci.edu/users/f/fielding/index.html> 
         (<opaquelocktoken:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>) 
      
    
   >>Response 
    
     HTTP/1.1 204 No Content 
      
      

In this example, even though both the source and destination are locked, only one lock token must be submitted, for the lock on the destination. This is because the source resource is not modified by a COPY, and hence unaffected by the write lock. In this example, user agent authentication has previously occurred via a mechanism outside the scope of the HTTP protocol, in the underlying transport layer.¶

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 "Depth: infinity", 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, the resource is subject to being added to an existing lock at the destination (see Section 7.7). For example, if the MOVE makes the resource a child of a collection that is locked with "Depth: infinity", then the resource will be added to that collection's lock. Additionally, if a resource locked with "Depth: infinity" is moved to a destination that is within the scope of the same lock (e.g., within the namespace tree covered by the lock), the moved resource will again be a added to the lock. In both these examples, as specified in Section 7.8, 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 method with an If header but without a body. This form of LOCK MUST only be used to "refresh" a lock. Meaning, at minimum, that any timers associated with the lock MUST be re-set.¶

A server may return a Timeout header with a lock refresh that is different than the Timeout header returned when the lock was originally requested. Additionally clients may submit Timeout headers of arbitrary value with their lock refresh requests. Servers, as always, may ignore Timeout headers submitted by the client. Note that timeout is measured in seconds remaining until expiration.¶

If an error is received in response to a refresh LOCK request the client MUST NOT assume that the lock was refreshed.¶

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 13.25) along with all XML elements defined for use with that element.¶

A client may submit a Depth header with a value of "0", "1", or "infinity" with a PROPFIND on a collection resource. Servers MUST support the "0", "1" and "infinity" behaviors on WebDAV-compliant resources. By default, the PROPFIND method without a Depth header MUST act 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 server)
• Request all dead property values, by using 'dead-props' element. This can be combined with retrieving specific live properties named as above. Servers advertising support for RFC2518bis MUST support this feature.
• Request property values for those properties defined in this specification plus dead properties, by using 'allprop' element
• 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 [14] and RFC3744 [15]) 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. A WebDAV server MAY omit certain live properties from other specifications when responding to an allprop request from an older client, and MAY return only custom (dead) properties and those defined in this specification.¶

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. The multistatus contains one response element for each resource in the scope of the request (in no required order) or may be empty if no resources match the request.¶

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 which does not exist is an error and MUST be noted, if the response uses a multistatus XML element, with a response XML element which contains a 404 (Not Found) status value.¶

Consequently, the multistatus XML element for a collection resource with member URLs MUST include a response XML element for each member URL of the collection, to whatever depth was requested. Each response XML element MUST contain an href XML element that gives the URL of the resource on which the properties in the prop XML element are defined. URLs for collections appearing in the results MUST end in a slash character. Results for a PROPFIND on a collection resource with internal member URLs are returned as a flat list whose order of entries is not significant.¶

A server enumerating the members of a collection using absolute URLs in a PROPFIND response MUST use a common prefix in those URLs, and that prefix MUST be the absolute URL used in the response to refer to the parent collection.¶

Unless otherwise notified, clients may expect that the URL for the parent collection in the PROPFIND response will be the same URL that was used to refer to the parent collection in the PROPFIND request. Servers MAY use an alternate URL for the parent collection in a PROPFIND response, but in this case the server MUST include a Content-Location header whose value is the fully-qualified URL used by the server to refer to the parent collection in this response.¶

URLs in a PROPFIND response body MAY be represented as fully- qualified URLs, in which case they must all contain the full parent collection URL (scheme, host, port, and absolute path). Alternatively, these URLs MAY be absolute paths (not containing scheme, host or port), but in this case they must all still contain the full parent collection path.¶

If a server allows resource names to include characters that arenít legal in HTTP URL paths, these characters must be URI-escaped on the wire. For example, it is illegal to use a space character or double- quote in a URI [5]. URIs appearing in PROPFIND or PROPPATCH XML bodies (or other XML marshalling defined in this specification) are still subject to all URI rules, including forbidden characters.¶

Properties may be subject to access control. In the case of allprop and propname, 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.¶

The results of this method SHOULD NOT be cached.¶

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. Instruction processing MUST occur 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 13.23 and section 13.24.¶

The MKCOL method is used to create a new collection. All WebDAV compliant resources MUST support the MKCOL method.¶

MKCOL creates a new collection resource at the location specified by the Request-URI. If the resource identified by the Request-URI is non-null then the MKCOL MUST fail. During MKCOL processing, a server MUST make the Request-URI a 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.¶

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.¶

Locks rooted on a resource MUST be destroyed in a successful DELETE of that resource.¶

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. The state of the resource to be copied is fixed at the point the server begins processing the COPY request.¶

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.¶

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 atomically. The consistency maintenance step allows the server to perform updates caused by the move, such as updating all URLs other than the Request-URI which identify the source resource, to point to the new destination resource. Consequently, 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. However, 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.¶

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

A LOCK method invocation to an unlocked resource creates a lock on the resource identified by the Request-URI, which becomes the root of the lock. Lock method requests to create a new lock MUST have a XML request body which contains an owner XML element and other information for this lock request. The server MUST preserve the information provided by the client in the owner field when the lock information is requested. The LOCK request MAY have a Timeout header.¶

Clients MUST assume that locks may 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.¶

• MUST contain a body with the value of the lockdiscovery property in a prop XML element.
• MUST include the Lock-Token response header with the token associated with the new lock.

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. The If header is not needed to provide the lock token although servers SHOULD still evaluate the If header and treat it as a conditional header.¶

For a successful response to this method, the server MUST remove the lock from the resource identified by the Request-URI and from all other resources included in the lock.¶

If all resources which have been locked under the submitted lock token can not 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 which supports the LOCK method MUST support the UNLOCK method.¶

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 on all OPTIONS responses.¶

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 "bis" compliance. In general, support for one compliance class does not entail support for any other. Please refer to section 16 for more details on compliance classes defined in this specification.¶

This header must also appear on responses to OPTIONS requests to the special '*' Request-URI as defined in HTTP/1.1. In this case it means that the repository supports the named features in at least some internal namespaces.¶

As an optional request header, this header allows the client to advertise compliance with named features. Clients need not advertise 1, 2 or bis because a WebDAV server currently doesn't need that information to decide how to respond to requests defined in this specification or in HTTP/1.1. However, future extensions may define client compliance codes. When used as a request header, the DAV header MAY affect caching so this header SHOULD NOT be used on all GET requests.¶

The Depth request header is used with methods executed on resources which 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 immediate children, ("Depth: 1"), or the resource and all its progeny ("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 which 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 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.¶

Any headers on a method that has a defined interaction with the Depth header MUST be applied to all resources in the scope of the method except where alternative behavior is explicitly defined. For example, an If-Match header will have its value applied against every resource in the method's scope and will cause the method to fail if the header fails to match.¶

If a resource, source or destination, within the scope of the method with a 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 children. If a resource does not have internal children then the Depth header MUST be ignored.¶

Please note, however, that it is always an error to submit a value for the Depth header that is not allowed by the method's definition. Thus submitting a "Depth: 1" on a COPY, even if the resource does not have internal members, will result in a 400 (Bad Request). The method should fail not because the resource doesn't have internal members, but because of the illegal value in the header.¶

Destination = "Destination" ":" ( absoluteURI )¶

The Destination request header specifies the URI which identifies a destination resource for methods such as COPY and MOVE, which take two URIs as parameters. Note that the absoluteURI production is defined in RFC2396 [5].¶

If the Destination value is an absolute URI, 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 with a 502 (Bad Gateway) response. Servers MAY attempt to copy the resource to the remote server using PUT/PROPPATCH or another mechanism.¶

Force-Authentication = "Force-Authentication" ":" Method¶

The Force-Authentication request header is used with the OPTIONS method to specify that the client wants to be challenged for authentication credentials to the resource identified by the Request-URI. If present on a request to a WebDAV-compliant resource, the server MUST respond with either 401 (Unauthorized) or 501 (Not Implemented) status code. The Method value is used for the client to indicate what method it intends to use first on the resource identified in the Request-URI.¶

The If request header is intended to have similar functionality to the If-Match header defined in section 14.24 of RFC2616 [7]. However the If header is intended for use with any URI which represents state information, referred to as a state token, about a resource 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. The <DAV:no-lock> state token is a special token that must never match an actual valid lock token. The purpose of this is described in section 9.5.5.¶

The If header's purpose is to describe a series of state lists. If the state of the resource to which the header is applied does not match any of the specified state lists then the request MUST fail with a 412 (Precondition Failed). If one of the described state lists matches the state of the resource then the request may succeed.¶

The server must parse the If header when it appears on any request, evaluate all the clauses, and if the conditional evaluates to false, fail the request.¶

Note that the absoluteURI production is defined in RFC2396 [5].¶

RFC2518 originally defined the If header without comma separators. This oversight meant that the If header couldn't be divided up among multiple lines according to the HTTP header manipulation rules. Servers supporting "bis" MUST be able to accept commas in If header values. If the header has commas between tokens or clauses, the header can be evaluated simply by removing the commas and proceeding with the evaluation rules.¶

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 the state of a non-null destination resource during a COPY or MOVE. A value of "F" states that the server must not perform the COPY or MOVE operation if the state of the destination resource is non-null. 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 the If-Match: * header of HTTP/1.1, 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.¶

All DAV compliant resources MUST support the Overwrite header.¶

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.¶

Timeout response values MUST use a Second value or Infinite.¶

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 2^32-1.¶

The timeout counter MUST be restarted if a refresh LOCK request is successful. The timeout counter SHOULD NOT be restarted at any other time.¶

If the timeout expires then the lock may be lost. Specifically, if the server wishes to harvest the lock upon time-out, 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. Thus logs should be updated with the disposition of the lock, notifications should be sent, etc., just as they would be for an UNLOCK request.¶

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 off-line.¶

A client MUST NOT assume that just because the time-out has expired the lock has been lost. Likewise, a client MUST NOT assume that just because the time-out has not expired, the lock still exists (and for this reason, clients are strongly advised to use ETags as well).¶

The 102 (Processing) status code is an interim response used to inform the client that the server has accepted the complete request, but has not yet completed it. This status code SHOULD only be sent when the server has a reasonable expectation that the request will take significant time to complete. As guidance, if a method is taking longer than 20 seconds (a reasonable, but arbitrary value) to process the server SHOULD return a 102 (Processing) response. The server MUST send a final response after the request has been completed.¶

Methods can potentially take a long period of time to process, especially methods that support the Depth header. In such cases the client may time-out the connection while waiting for a response. To prevent this the server may return a 102 (Processing) status code to indicate to the client that the server is still processing the method.¶

The 207 (Multi-Status) status code provides status for multiple independent operations (see Section 12 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 the 'missing-lock-token' element and corresponding href in the error body.¶

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 which 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 WebDAV request may be redirected using this status code.¶

Any WebDAV request may be redirected using this status code.¶

• the Host header is missing in any request
• The protocol version is HTTP/1.0
• Any header is improperly formatted
• The request method line is improperly formatted

To be used if the server does not ever accept this method on this kind of resource. For example, if a PUT is not accepted on a collection.¶

The 409 Conflict is most typically returned when a method that attempts to create a new resource must fail, because one of the collections that resource depends on does not exist. However, other types of conflicts are defined in specifications extending RFC2518. Therefore, this can be returned in response to all methods.¶

Any request may contain a conditional header defined in HTTP (If-Match, If-Modified-Since, etc.) or the "If" conditional header defined in this specification. If the request contains a conditional header, and if that condition fails to hold, then this error code may be returned. This status code is not typically appropriate if the client did not include a conditional header in the request.¶

This status code is used in HTTP 1.1 only for Request-URIs, because full URIs arenít used in other headers. WebDAV specifies full URLs in other headers, therefore this error may be used if the URI is too long in other locations as well. This status code may be used in response to any method in this specification.¶

This status code is particularly useful to respond to requests that the server considers a denial-of-service attack, such as excessively large PROPFIND depth infinity requests or requests in quick succession.¶

The 300-303, 305 and 307 responses defined in HTTP 1.1 normally take a Location header to indicate where the client should make the request. The Multi-Status response syntax as defined in RFC2518 did not allow for the Location header information to be included in an unambiguous way, so servers MAY choose not to use these status codes in Multi-Status responses. If a clients receives this status code in Multi-Status, the client MAY reissue the request to the individual resource, so that the server can issue a response with a Location header for each resource.¶

Additionally, this specification defines a new element that servers MAY use in the response element to provide a location value in Multi-Status (see Section 13.29).¶

Name:

activelock

Namespace:

DAV:

Purpose:

Describes a lock on a resource.

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

depth

Namespace:

DAV:

Purpose:

The value of the Depth header.

Value:

"0" | "1" | "infinity"

Extensibility:

MAY be extended with attributes which SHOULD be ignored.

Name:

locktoken

Namespace:

DAV:

Purpose:

The lock token associated with a lock.

Description:

The href contains a single lock token URI which refers to the lock (i.e., the OpaqueLockToken-URI production in section 6.4).

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

lockroot

Namespace:

DAV:

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 contains a URL with the address of the root of the lock. The server SHOULD include this in all lockdiscovery property values and the response to LOCK requests.

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

timeout

Namespace:

DAV:

Purpose:

The number of seconds remaining before a lock expires.

Value:

TimeType (defined in Section 9.8).

Extensibility:

MAY be extended with attributes which SHOULD be ignored.

Name:

collection

Namespace:

DAV:

Purpose:

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

Extensibility:

MAY be extended with child elements or attributes which SHOULD be ignored if not recognized.

Name:

href

Namespace:

DAV:

Purpose:

Identifies the content of the element as a URI. In many situations, this URI MUST be a HTTP URI, and furthermore, it MUST identify a WebDAV resource. There is one exception to this general rule in the lockdiscovery property, where the lock token (which is a URI but may not be a HTTP URI) is inside the href element. Other specifications SHOULD be explicit if the href element is to contain non-HTTP URIs.

Value:

URI (See section 3.2.1 of RFC2616 [7])

Extensibility:

MAY be extended with attributes which SHOULD be ignored.

Name:

lockentry

Namespace:

DAV:

Purpose:

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

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

lockinfo

Namespace:

DAV:

Purpose:

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

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

lockscope

Namespace:

DAV:

Purpose:

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

Extensibility:

SHOULD NOT be extended with child elements. MAY be extended with attributes which SHOULD be ignored.

Name:

exclusive

Namespace:

DAV:

Purpose:

Specifies an exclusive lock

Extensibility:

Normally empty, but MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

shared

Namespace:

DAV:

Purpose:

Specifies a shared lock

Extensibility:

Normally empty, but MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

locktype

Namespace:

DAV:

Purpose:

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

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

write

Namespace:

DAV:

Purpose:

Specifies a write lock.

Extensibility:

Normally empty, but MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

multistatus

Namespace:

DAV:

Purpose:

Contains multiple response messages.

Description

The responsedescription 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.

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

locktype

Namespace:

DAV:

Purpose:

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

Description:

A particular href 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.

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

propstat

Namespace:

DAV:

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.

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

status

Namespace:

DAV:

Purpose:

Holds a single HTTP status-line

Value:

status-line (status-line defined in RFC2616 [7]

Extensibility:

MAY be extended with attributes which SHOULD be ignored.

Name:

responsedescription

Namespace:

DAV:

Purpose:

Contains a message that can be displayed to the user explaining the nature of the response.

Description:

This XML element provides information suitable to be presented to a user.

Extensibility:

MAY be extended with attributes which SHOULD be ignored.

Name:

owner

Namespace:

DAV:

Purpose:

Provides information about the principal taking out a lock.

Description

The owner XML element provides 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 owns a lock. This information is provided by the client, and may only be altered by the server if the owner value provided by the client is empty.

Extensibility

MAY be extended with child elements, mixed content, text content or attributes. Structured content, for example one or more <href> child elements containing URLs, is RECOMMENDED.

Name:

prop

Namespace:

DAV:

Purpose:

Contains properties related to a resource.

Description

The prop XML element is a generic container for properties defined on resources. All elements inside a prop XML element MUST define properties related to the resource. No other elements may be used inside of a prop element.

Extensibility

MAY be extended with attributes which SHOULD be ignored if not recognized. Any child element of this element must be considered to be a property name, however these are not restricted to the property names defined in this document or other standards.

Name:

propertyupdate

Namespace:

DAV:

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. This XML element is multi-valued.

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

remove

Namespace:

DAV:

Purpose:

Lists the DAV 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.

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

set

Namespace:

DAV:

Purpose:

Lists the DAV property values to be set for a resource.

Description:

The set XML element MUST contain only a prop XML element. The elements contained by the prop XML element inside the set XML 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.

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

propfind

Namespace:

DAV:

Purpose:

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

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized, as long as it still contains one of the required elements.

Name:

allprop

Namespace:

DAV:

Purpose:

The allprop XML element 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.

Extensibility:

Normally empty, but MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

propname

Namespace:

DAV:

Purpose:

The propname XML element specifies that only a list of property names on the resource is to be returned.

Extensibility:

Normally empty, but MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

dead-props

Namespace:

DAV:

Purpose:

The dead-props XML element specifies that all dead properties, names and values, should be returned in the response.

Extensibility:

Normally empty, but MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

location

Namespace:

DAV:

Purpose:

In normal responses (not Multi-Status), some status codes go along with a Location header. When these status codes are used in a Multi-Status response, this element is used instead.

Description:

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

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

error

Namespace:

DAV:

Purpose:

Error responses, particularly 403 Forbidden and 409 Conflict, sometimes need more information to indicate what went wrong. When an error response contains a body in WebDAV, the body is in XML with the root element 'error'. The 'error' tag SHOULD include a standard error tag defined in this specification or another specification. The 'error' tag MAY include custom error tags (in custom namespaces) which a client can safely ignore.

Description:

Contains any XML element

Extensibility:

Fully extensible with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

creationdate

Namespace:

DAV:

Purpose:

Records the time and date the resource was created.

Value:

date-time (defined in RFC3339 [8], see the ABNF in section 5.6.)

Protected:

MAY be protected. Some servers allow 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 getetag instead).

COPY/MOVE behaviour:

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 creationdate property should be defined on all DAV compliant resources. If present, it contains a timestamp of the moment when the resource was created (i.e., the moment it had non-null state).

Extensibility:

MAY contain attributes which SHOULD be ignored if not recognized.

Name:

displayname

Namespace:

DAV:

Purpose:

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

Value:

Any text

Protected:

Possibly

COPY/MOVE behaviour:

This property value SHOULD be preserved in local COPY and MOVE operations. It MAY be attempted to be set in a COPY operation to a remote server.

Description:

The displayname property should be defined on all DAV compliant resources. If present, the property contains a description of the resource that is suitable for presentation to a user.

Extensibility:

MAY contain attributes which SHOULD be ignored if not recognized.

Name:

getcontentlanguage

Namespace:

DAV:

Purpose:

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

Value:

language-tag (language-tag is defined in section 14.13 of RFC2616 [7])

Protected:

SHOULD NOT be protected, so that clients can reset the language.

COPY/MOVE behaviour:

This property value SHOULD be preserved in local COPY and MOVE operations. It SHOULD be attempted to be set in a COPY operation to a remote server.

Description:

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

Extensibility:

MAY contain attributes which SHOULD be ignored if not recognized.

Name:

getcontentlength

Namespace:

DAV:

Purpose:

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

Value:

content-length (see section 14.14 of RFC2616 [7])

Protected:

SHOULD be protected so clients cannot set to misleading values

Description:

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

COPY/MOVE behaviour:

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

Extensibility:

MAY contain attributes which SHOULD be ignored if not recognized.

Name:

getcontenttype

Namespace:

DAV:

Purpose:

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

Value:

media-type (defined in section 3.7 of RFC2616 [7])

Protected:

SHOULD NOT be protected, so clients may fix this value

COPY/MOVE behaviour:

This property value SHOULD be preserved in local COPY and MOVE operations. In a remote COPY operation that is implemented through a PUT request, the PUT request must have the appropriate Content-Type header.

Description:

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

Extensibility:

MAY contain attributes which SHOULD be ignored if not recognized.

Name:

getetag

Namespace:

DAV:

Purpose:

Contains the ETag header returned by a GET without accept headers.

Value:

entity-tag (defined in section 3.11 of RFC2616 [7])

Protected:

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

COPY/MOVE behaviour:

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

Description:

The getetag property MUST be defined on any DAV compliant resource that returns the Etag header. Refer to RFC2616 for a complete definition of the semantics of an ETag. Note that changes in properties or lock state MUST not cause a resourceís ETag to change.

Extensibility:

MAY contain attributes which SHOULD be ignored if not recognized.

Name:

getlastmodified

Namespace:

DAV:

Purpose:

Contains the Last-Modified header returned by a GET method without accept headers.

Value:

rfc1123-date (defined in section 3.3.1 of RFC2616 [7])

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 behaviour:

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 'getlastmodified' value, and this is preserved in a MOVE even when the HTTP Last-Modified value SHOULD change. Thus, clients cannot rely on this value for caching and SHOULD use ETags.

Description:

Note that 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 getlastmodified property MUST be defined on any DAV compliant resource that returns the Last- Modified header in response to a GET.

Extensibility:

MAY contain attributes which SHOULD be ignored if not recognized.

Name:

lockdiscovery

Namespace:

DAV:

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 behaviour:

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:

The lockdiscovery property 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. If there are no locks, but the server supports locks, the property will be present but contain zero ëactivelockí elements. If there is one or more lock, an ëactivelockí element appears for each lock on the resource.

Extensibility:

MAY be extended with additional child elements or attributes which SHOULD be ignored if not recognized.

Name:

resourcetype

Namespace:

DAV:

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 behaviour:

Generally a COPY/MOVE of a resource results in the same type of resource at the destination. In a remote COPY, the source server SHOULD NOT attempt to set this property.

Description:

The resourcetype property MUST be defined on all DAV compliant resources. The default value is empty.

Extensibility:

MAY be extended with any child elements or attributes which SHOULD be ignored if not recognized. If the element contains the 'collection' child element plus additional unrecognized elements/attributes, it should generally be treated as a collection. If the element contains no recognized child elements it should be treated as a non- collection WebDAV-compliant resource.

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

Namespace:

DAV:

Purpose:

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

Protected:

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

COPY/MOVE behaviour:

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:

The supportedlock property of a resource returns a listing of the combinations of scope and access types which 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.

Extensibility:

MAY be extended with any child elements or attributes which SHOULD be ignored if not recognized.

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 supportedlock property, the lockdiscovery property, the Time-Out response header and the Lock- Token request header. A class "2" compliant resource SHOULD also support the Time-Out 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. In particular, this allows clients to use the Force-Authentication header on requests. Class 1 must be supported as well. Class 2 MAY be supported.¶

• the Force-Authentication header.
• Any behavior that it supports, in the manner specified in this document, rather than in the manner specified in RFC2518, for all client requests. A server MAY use an older behavior for specific clients that are discovered to have interoperability problems with the requirements of this specification, but MUST NOT use an older behavior indiscriminately.

Example:

         DAV: 1, bis 
      

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 Basic authentication credentials in a WWW-Authenticate header unless the connection is secure. Examples of secure connections include a Transport Layer Security (TLS) connection employing a strong cipher suite with mutual authentication of client and server, or a connection over a network which is physically secure, for example, an isolated network in a building with restricted access.¶

WebDAV applications MUST support the Digest authentication scheme RFC2069 [1]. 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 which 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.¶

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 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 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 XML [11], which instruct 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 [11]. However, XML [11] 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 RFC2376 [13]. Therefore, implementers must be aware that external XML entities should be treated as untrustworthy. If a server implementor chooses not to handle external XML entities, it SHOULD respond to requests containing external entities with the precondition defined above (external-entities-forbidden).¶

There is also the scalability risk that would accompany a widely deployed application which 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 which fields requests for the resource containing the external XML entity.¶

• 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.

The PUT and DELETE methods are defined in HTTP and thus may be used by HTTP clients, but the responses to PUT and DELETE have been extended in this specification, so some special consideration on backward compatibility is worthwhile.¶

First, if a PUT or DELETE request includes a header defined in this specification (Depth or If), the server can assume the request comes from a WebDAV-compatible client. The server may even be able to track a number of requests across a session and know that a client is a WebDAV client. However, this kind of detection may not be necessary.¶

Since any HTTP client ought to handle unrecognized 400-level and 500-level status codes as errors, the following new status codes should not present any issues: 422, 423 and 507. 424 is also a new status code but it appears only in the body of a Multistatus response. So, for example, if a HTTP client attempted to PUT or DELETE a locked resource, the 423 Locked response ought to result in a generic error presented to the user.¶

The 102 Processing response code is new, and indicates that the client may wish to extend its normal timeout period. However, the choice to extend the timeout period is entirely optional, and thus a HTTP client receiving a 102 Processing status response may time out anyway, with no avoidable adverse effects.¶

The 207 Multistatus response is interesting because a HTTP client issuing a DELETE request to a collection might interpret a 207 response as a success, even though it does not realize the resource is a collection and cannot understand that the DELETE operation might have been a complete or partial failure. Thus, a server MAY choose to treat a DELETE of a collection as an atomic operation, and use either 204 No Content in case of success, or some appropriate error response (400 or 500 level) depending on what the error was. This approach would maximize backward compatibility. However, since interoperability tests and working group discussions have not turned up any instances of HTTP clients issuing a DELETE request against a WebDAV collection, this concern may be more theoretical than practical. Thus, servers MAY instead choose to treat any such DELETE request as a WebDAV request, and send a 207 Multistatus containing more detail about what resources could not be deleted.¶