HTTP Extensions for Distributed Authoring - WebDAV
Open Source Application Foundation2064 Edgewood Dr.Palo AltoCA94303USlisa@osafoundation.org
Applications
WebDAVwebdavhttpauthoringwebWebDAV consists of a set of methods, headers, and content-types
ancillary to HTTP/1.1 for the management of resource properties,
creation and management of resource collections, URL namespace
manipulation, and resource locking (collision avoidance).
RFC2518 was published in February 1999, and this specification makes minor
revisions mostly due to interoperability experience.
This document describes an extension to the HTTP/1.1 protocol that
allows clients to perform remote web content authoring operations.
This extension provides a coherent set of methods, headers, request
entity body formats, and response entity body formats that provide
operations for:
Properties: The ability to create, remove, and query information
about Web pages, such as their authors, creation dates, etc. Also,
the ability to link pages of any media type to related pages.
Collections: The ability to create sets of documents and to retrieve
a hierarchical membership listing (like a directory listing in a
file system).
Locking: The ability to keep more than one person from working on a
document at the same time. This prevents the "lost update problem",
in which modifications are lost as first one author then another
writes changes without merging the other author's changes.
Namespace Operations: The ability to instruct the server to copy and
move Web resources, operations which change the URL.
Requirements and rationale for these operations are described in a
companion document, "Requirements for a Distributed Authoring and
Versioning Protocol for the World Wide Web" .
This standard does not specify the versioning operations suggested
by . That work was done in a separate document,
"Versioning Extensions to WebDAV" .
The sections below provide a detailed introduction to various WebDAV abstractions:
resource properties,
collections of resources,
locks in general and
write locks specifically.
These abstractions are manipulated by the
WebDAV-specific HTTP methods
and the new HTTP headers used with WebDAV methods.
While the status codes provided by HTTP/1.1 are sufficient to
describe most error conditions encountered by WebDAV methods, there
are some errors that do not fall neatly into the existing
categories. This specification defines new status
codes developed for WebDAV methods and describes
existing HTTP status codes as used in
WebDAV. Since some WebDAV methods may operate over many resources, the
Multi-Status response has been
introduced to return status information for multiple resources. Finally, this
version of WebDAV introduces precondition and postcondition
XML elements in error response bodies.
WebDAV uses for property names and some values, and also uses
XML to marshal complicated request and response. This specification contains
DTD and text definitions of all all properties
and all other XML elements used in marshalling.
WebDAV includes a few special rules on how to process
XML appearing in WebDAV so that it truly is extensible.
Finishing off the specification are sections on what it means for a resource to be
compliant with this specification, on
internationalization support, and on
security.
Since this document describes a set of extensions to the HTTP/1.1
protocol, the augmented BNF used herein to describe protocol
elements is exactly the same as described in section 2.1 of
, including the rules about
implied linear white-space.
Since this augmented BNF uses the basic production rules provided in
section 2.2 of , these rules apply to this document as
well.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in .
Note that in natural language, a property like the
"creationdate" property in the "DAV:" XML namespace is sometimes
referred to as "DAV:creationdate" for brevity.
URI/URL - A Uniform Resource Identifier and Uniform Resource
Locator, respectively. These terms (and the distinction between
them) are defined in .
URI/URL Mapping - A relation between an absolute URI and a resource. Since
a resource can represent items that are not network retrievable, as well
as those that are, it is possible for a resource to have zero, one, or many
URI mappings. Mapping a resource to an "http" scheme URI makes it possible
to submit HTTP protocol requests to the resource using the URI.
Collection - A resource that contains a set of URLs, which identify
and locate member resources and which meet the collections
requirements.
Member URL - A URL which is a member of the set of URLs contained by
a collection.
Internal Member URL - A Member URL that is immediately relative to
the URL of the collection (the definition of immediately relative is
given later).
Property - A name/value pair that contains descriptive information
about a resource.
Live Property - A property whose semantics and syntax are enforced
by the server. For example, the live property DAV:getcontentlength
has its value, the length of the entity returned by a GET request,
automatically calculated by the server.
Dead Property - A property whose semantics and syntax are not
enforced by the server. The server only records the value of a dead
property; the client is responsible for maintaining the consistency
of the syntax and semantics of a dead property.
Principal -
A "principal" is a distinct human or computational actor that
initiates access to network resources.
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
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 MIME 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.
The XML namespace extension
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:" uses a scheme name defined solely for
the purpose of creating this XML namespace. Defining new URI schemes for namespaces
is discouraged. "DAV:" was defined before
standard best practices emerged, and this namespace is
still used only because of significant existing deployments.
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 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 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.
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.
A property is always represented in XML with an XML element
consisting of the property name, called the "property name element".
The simplest example is an empty
property, which is different from a property that does not exist:
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. In the latter case, servers MUST preserve
certain aspects of the content (described using the terminology
from ). For the property name Element Information Item itself:[namespace name][local name][attributes] named "xml:lang" or any such attribute in scope[children] of type element or characterOn all Element Information Items in the value:[namespace name][local name][attributes][children] of type element or characterOn Attribute Information Items in the value:[namespace name][local name][normalized value]On Character Information Items in the value:[character code]Since prefixes are used in some XML query/handling tools, servers
SHOULD preserve, for any Information Item in the value:[prefix]In dead properties (considered as content, like document bodies)
servers are encouraged to (MAY) preserve, for any Comment Information Item
in the value:[content]
XML Infoset attributes not listed above MAY be preserved by the
server, but clients MUST NOT rely on them being preserved.
The XML attribute xml:space MUST NOT be used to change white space
handling. White space in property values is significant.
Consider a dead property 'author' created by the client as follows:When this property is requested, a server might return:Note in this example:The [prefix] for the property name itself was not preserved, being
non-significantattribute values have been rewritten with double quotes instead of
single quotes (quoting style is not significant), and attribute
order has not been preserved,the xml:lang attribute has been returned on the property name element
itself (it was in scope when the property was set, but the exact
position in the response is not considered significant as long as it
is in scope),whitespace between tags has been preserved everywhere (whitespace
between attributes not so),CDATA encapsulation was replaced with character escaping (the reverse
would also be legal),the comment item was stripped (as would have been a processing
instruction item).
Implementation note: there are cases such as editing scenarios where clients may
require that XML content is preserved character-by-character (such
as attribute ordering or quoting style). In this case, clients
should consider using a text-only property value by escaping all
characters that have a special meaning in XML parsing.
A property name is a universally unique identifier that is
associated with a schema that provides information about the syntax
and semantics of the property.
Because a property's name is universally unique, clients can depend
upon consistent behavior for a particular property across multiple
resources, on the same and across different servers, so long as that
property is "live" on the resources in question, and the
implementation of the live property is faithful to its definition.
The XML namespace mechanism, which is based on URIs (), 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.
This section provides a description of a new type of Web resource,
the collection, and discusses its interactions with the HTTP URL
namespace. The purpose of a collection resource is to model
collection-like objects (e.g., file system directories) within a
server's namespace.
All DAV compliant resources MUST support the HTTP URL namespace
model specified herein.
The HTTP URL namespace is a hierarchical namespace where the
hierarchy is delimited with the "/" character.
An HTTP URL namespace is said to be consistent if it meets the
following conditions: for every URL in the HTTP hierarchy there
exists a collection that contains that URL as an internal member.
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 and
, 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
.
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.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 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 ability to lock a resource provides a mechanism for serializing
access to that resource. Using a lock, an authoring client can
provide a reasonable guarantee that another principal will not
modify a resource while it is being edited. In this way, a client
can prevent the "lost update" problem.
This specification allows locks to vary over two client-specified
parameters, the number of principals involved (exclusive vs. shared)
and the type of access to be granted. This document defines locking
for only one access type, write. However, the syntax is extensible,
and permits the eventual specification of locking for other access
types.
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. 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. 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.
When a LOCK operation creates a new lock, the new lock token is
returned in the Lock-Token response header defined in
,
and also in the body of the response.
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.
This specification encourages servers to create UUIDs for lock tokens,
and to use the URI form defined by "A Universally Unique
Identifier (UUID) URN Namespace" (). 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 .
Example: "urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6"
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.
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.
This section describes the semantics specific to the write lock
type. The write lock is a specific instance of a lock type, and is
the only lock type described in this specification.
An exclusive write lock will prevent parallel changes to a resource by
any principal other than the write lock holder. In general
terms, changes affected by write locks include changes to:
the content of the resource any dead property of the resource any live property defined to be lockable (all properties defined
in this specification are lockable) the direct membership of the resource, if it is a collection the URL/location of a resource
The next few sections describe in more specific terms how write
locks interact with various operations.
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.
Although the write locks provide some help in
preventing lost updates, they cannot guarantee that updates will
never be lost. Consider the following scenario:
Two clients A and B are interested in editing the resource
'index.html'. Client A is an HTTP client rather than a WebDAV
client, and so does not know how to perform locking.
Client A doesn't lock the document, but does a GET and begins
editing.
Client B does LOCK, performs a GET and begins editing.
Client B finishes editing, performs a PUT, then an UNLOCK.
Client A performs a PUT, overwriting and losing all of B's changes.
There are several reasons why the WebDAV protocol itself cannot
prevent this situation. First, it cannot force all clients to use
locking because it must be compatible with HTTP clients that do not
comprehend locking. Second, it cannot require servers to support
locking because of the variety of repository implementations, some
of which rely on reservations and merging rather than on locking.
Finally, being stateless, it cannot enforce a sequence of operations
like LOCK / GET / PUT / UNLOCK.
WebDAV servers that support locking can reduce the likelihood that
clients will accidentally overwrite each other's changes by
requiring clients to lock resources before modifying them. Such
servers would effectively prevent HTTP 1.0 and HTTP 1.1 clients from
modifying resources.
WebDAV clients can be good citizens by using a lock / retrieve /
write /unlock sequence of operations (at least by default) whenever
they interact with a WebDAV server that supports locking.
HTTP 1.1 clients can be good citizens, avoiding overwriting other
clients' changes, by using entity tags in If-Match headers with any
requests that would modify resources.
Information managers may attempt to prevent overwrites by
implementing client-side procedures requiring locking before
modifying WebDAV resources.
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. When trying to lock a collection upon
creation, clients may 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 an
locked resource with empty content. Subsequently, a successful PUT request (with the correct
lock token) provides the content for the resource, and the server MUST also use
the content-type and content-language information from this request.
In this situation, a WebDAV server that was implemented from
MAY create "lock-null" resources which are special and unusual
resources. Historically, a lock-null resource:
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 DAV:lockdiscovery and DAV:supportedlock
properties.
However, interoperability and compliance problems have been found
with lock-null resources. Therefore, they are deprecated. WebDAV
servers SHOULD create regular locked empty resources, which are and
behave in every way as normal resources. A locked empty resource:
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 DAV: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 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. 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.
This means that if a collection is locked (depth 0 or infinity), its
lock-token is required in all these cases:
DELETE a collection's direct internal member MOVE a member out of the collectionMOVE a member into the collectionMOVE to rename a member within a collectionCOPY a member into a collectionPUT 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 'lock-token-present' 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 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.
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 ).
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
URL namespace tree covered by the lock), the moved resource will again
be a added to the lock. In both these examples, as specified in
, 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.
Some of the following new HTTP methods use XML as a request and
response format. All DAV compliant clients and resources MUST use
XML parsers that are compliant with
and XML Namespaces. 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 ). 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.
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 they 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, ).
HTTP 1.1 recommends the use of the ETag header in responses to GET
and PUT requests. 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 whether it has changed.
Timestamps do not solve this problem nearly as well as ETags.
WebDAV servers SHOULD support strong ETags for all resources that
may be PUT. If ETags are supported for a resource, the server MUST
return the ETag header in all PUT and GET responses to that
resource, as well as provide the same value for the DAV:getetag
property.
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 DAV:getlastmodified value) for a resource that has an unchanged
body. 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 DeltaV introduced a mechanism to
include more specific information in the body of an error response
(section 1.6 of ). The 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 mechanism does not take the place of using a correct numeric
error code as defined here or in HTTP, because the client MUST
always be able to take a reasonable course of action based only on
the numeric error. However, it does remove the need to define new
numeric error codes, avoiding the confusion of who is allowed to
define such new codes. The codes used in this mechanism are XML
elements in a namespace, so naturally any group defining a new error
code can use their own namespace. As always, the "DAV:" namespace is
reserved for use by IETF-chartered WebDAV working groups.
A server supporting "bis" SHOULD include a specific XML error code
in a "DAV:error" response body element, when a specific XML error
code is defined in this document. The DAV:error element may
contain multiple elements describing specific errors. For error
conditions not specified in this document, the server MAY simply
choose an appropriate numeric status and leave the response body
blank.
In this specification, both the numeric and the XML error code are
defined for some failure situations, in which case the XML error
code must have the "DAV:" namespace, appear in the "error" root
element, and be returned in a body with the numeric error code
specified.
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 () 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.
A client may submit a 'propfind' XML element in the body of the
request method describing what information is being requested. It
is possible to:
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 this specification 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 and
)
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.
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 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 with internal member URLs are returned as a flat list whose
order of entries is not significant.
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.
The results of this method SHOULD NOT be cached.
A server MAY fail an entire PROPFIND request with an appropriate status code and
MAY redirect the entire request. In addition, the following error codes are
specifically defined for PROPFIND requests:
403 Forbidden - A server MAY reject all
PROPFIND requests on collections with depth header of "Infinity", in
which case it SHOULD use this error with the precondition code
'propfind-finite-depth' inside the error body.
The following status codes
are defined for use within the PROPFIND Multi-Status response:
200 OK - A property exists and/or its value is successfully returned.401 Unauthorized - The property cannot be viewed without appropriate authorization.403 Forbidden - The property cannot be viewed regardless of authentication.404 Not Found - The property does not exist.
In this example, PROPFIND is executed on a non-collection resource
http://www.example.com/file. The propfind XML element specifies the
name of four properties whose values are being requested. In this
case only two properties were returned, since the principal issuing
the request did not have sufficient access rights to see the third
and fourth properties.
In this example, PROPFIND is executed on a collection resource
http://www.example.com/mycol/. The client requests the values of
two specific live properties plus all dead properties (names and
values). The response is not shown.
In this example, PROPFIND is invoked on the collection resource
http://www.example.com/container/, with a propfind XML element
containing the propname XML element, meaning the name of all
properties should be returned. Since no Depth header is present, it
assumes its default value of "infinity", meaning the name of the
properties on the collection and all its descendents should be
returned.
Consistent with the previous example, resource
http://www.example.com/container/ has six properties defined on it:
bigbox and author in the "http://www.example.com/boxschema/"
namespace, and creationdate, displayname, resourcetype, and
supportedlock in the "DAV:" namespace.
The resource http://www.example.com/container/index.html, a member
of the "container" collection, has nine properties defined on it,
bigbox in the "http://www.example.com/boxschema/" namespace and,
creationdate, displayname, getcontentlength, getcontenttype,
getetag, getlastmodified, resourcetype, and supportedlock in the
"DAV:" namespace.
This example also demonstrates the use of XML namespace scoping and
the default namespace. Since the "xmlns" attribute does not contain
a prefix, the namespace applies by default to all enclosed elements.
Hence, all elements which do not explicitly state the namespace to
which they belong are members of the "DAV:" namespace.
Note that 'allprop', despite its name which remains for backward-compatibility,
does not return every property, but only dead properties and the live properties
defined in this specification.
In this example, PROPFIND was invoked on the resource
http://www.foo.bar/container/ with a Depth header of 1, meaning the
request applies to the resource and its children, and a propfind XML
element containing the allprop XML element, meaning the request
should return the name and value of all the dead properties defined
on the resources, plus the name and value of all the properties defined
in this specification. This example illustrates the use of relative references
in the 'href' elements of the response.
The resource http://www.foo.bar/container/ has six properties defined
on it:
'bigbox' and 'author in the "http://www.foo.bar/boxschema/" namespace,
DAV:creationdate, DAV:displayname, DAV:resourcetype, and DAV:supportedlock.
The last four properties are WebDAV-specific, defined in .
Since GET is not supported on this resource, the get* properties
(e.g., DAV:getcontentlength) are not defined on this resource. The WebDAV-specific
properties assert that "container" was created on December
1, 1997, at 5:42:21PM, in a time zone 8 hours west of GMT
(DAV:creationdate), has a name of "Example collection" (DAV:displayname), a
collection resource type (DAV:resourcetype), and supports exclusive write
and shared write locks (DAV:supportedlock).
The resource http://www.foo.bar/container/front.html has nine
properties defined on it:
'bigbox' in the "http://www.foo.bar/boxschema/" namespace (another instance of the "bigbox"
property type), DAV:creationdate, DAV:displayname,
DAV:getcontentlength, DAV:getcontenttype, DAV:getetag,
DAV:getlastmodified, DAV:resourcetype, and DAV:supportedlock.
The DAV-specific properties assert that "front.html" was created on
December 1, 1997, at 6:27:21PM, in a time zone 8 hours west of GMT
(DAV:creationdate), has a name of "Example HTML resource" (DAV:displayname),
a content length of 4525 bytes (DAV:getcontentlength), a MIME type of
"text/html" (DAV:getcontenttype), an entity tag of "zzyzx" (DAV:getetag), was
last modified on Monday, January 12, 1998, at 09:25:56 GMT
(DAV:getlastmodified), has an empty resource type, meaning that it is not
a collection (DAV:resourcetype), and supports both exclusive write and
shared write locks (DAV:supportedlock).
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 and .
The following are examples of response codes one would expect to be
used in a 207 (Multi-Status) response for this method. Note,
however, that unless explicitly prohibited any 2/3/4/5xx series
response code may be used in a 207 (Multi-Status) response.
200 (OK) - The property set or change succeeded. Note that if this
appears for one property, it appears for every property in the response,
due to the atomicity of PROPPATCH.
403 (Forbidden) - The client, for reasons the server chooses not to
specify, cannot alter one of the properties.
403 (Forbidden): The client has attempted to set a read-only
property, such as DAV:getetag. If returning this error, the server
SHOULD use the precondition code 'writable-property' inside the response body.
409 (Conflict) - The client has provided a value whose semantics are
not appropriate for the property.
424 (Failed Dependency) - The property change could not be made because
of another property change that failed.
507 (Insufficient Storage) - The server did not have sufficient
space to record the property.
In this example, the client requests the server to set the value of
the "Authors" property in the "http://www.w3.com/standards/z39.50/"
namespace, and to remove the property "Copyright-Owner" in the
"http://www.w3.com/standards/z39.50/" namespace. Since the
Copyright-Owner property could not be removed, no property
modifications occur. The 424 (Failed Dependency) status code for
the Authors property indicates this action would have succeeded if
it were not for the conflict with removing the Copyright-Owner
property.
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 Request-URI is already mapped to a resource
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.
Responses from a MKCOL request MUST NOT be cached as MKCOL has non-idempotent
semantics. In addition to the general status codes possible, the following
status codes have specific applicability to MKCOL:
201 (Created) - The collection was created.
403 (Forbidden) - This indicates at least one of two conditions: 1)
the server does not allow the creation of collections at the given
location in its URL namespace, or 2) the parent collection of the
Request-URI exists but cannot accept members.
405 (Method Not Allowed) - MKCOL can only be executed on an unmapped
URL.
409 (Conflict) - A collection cannot be made at the Request-URI
until one or more intermediate collections have been created. The
server MUST NOT create those intermediate collections automatically.
415 (Unsupported Media Type) - The server does not support the
request body type (since this specification does not define any body
for MKCOL requests).
507 (Insufficient Storage) - The resource does not have sufficient
space to record the state of the resource after the execution of
this method.
This example creates a collection called /webdisc/xfiles/ on the
server www.example.com.
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 , 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 DELETE method on a collection MUST act as if a "Depth: infinity"
header was used on it. A client MUST NOT submit a Depth header with
a DELETE on a collection with any value but infinity.
DELETE instructs that the collection specified in the Request-URI
and all resources identified by its internal member URLs are to be
deleted.
If any resource identified by a member URL cannot be deleted then
all of the member's ancestors MUST NOT be deleted, so as to maintain
URL namespace consistency.
Any headers included with DELETE MUST be applied in processing every
resource to be deleted.
When the DELETE method has completed processing it MUST result in a
consistent URL namespace.
If an error occurs deleting an internal resource (a resource other
than the resource identified in the Request-URI) then the response
can be a 207 (Multi-Status). Multi-Status is used here to indicate
which internal resources could NOT be deleted, including an error
code which should help the client understand which resources caused
the failure. For example, the Multi-Status body could include a
response with status 423 (Locked) if an internal resource was
locked.
The server MAY return a 4xx status response, rather than a Multi-Status,
if the request failed.
424 (Failed Dependency) status codes SHOULD NOT be in the 207 (Multi-Status)
response for DELETE. They can be safely left out because the client will know
that the ancestors of a resource could not be deleted when the
client receives an error for the ancestor's progeny. Additionally
204 (No Content) errors SHOULD NOT be returned in the 207 (Multi-Status). The
reason for this prohibition is that 204 (No Content)
is the default success code.
In this example the attempt to delete
http://www.example.com/container/resource3 failed because it is
locked, and no lock token was submitted with the request.
Consequently, the attempt to delete
http://www.example.com/container/ also failed. Thus the client knows
that the attempt to delete http://www.example.com/container/ must
have also failed since the parent can not be deleted unless its
child has also been deleted. Even though a Depth header has not
been included, a depth of infinity is assumed because the method is
on a collection.
A PUT performed on an existing resource replaces the GET response
entity of the resource. Properties defined on the resource may be
recomputed during PUT processing but are not otherwise affected.
For example, if a server recognizes the content type of the request
body, it may be able to automatically extract information that could
be profitably exposed as properties.
A PUT that would result in the creation of a resource without an
appropriately scoped parent collection MUST fail with a 409
(Conflict).
This specification does not define the behavior of the PUT method
for existing collections. A PUT request to an existing collection MAY
be treated as an error (405 Method Not Allowed).
The MKCOL method is defined to create collections.
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.
When the source resource is not a collection the result of the COPY
method is the creation of a new resource at the destination whose
state and behavior match that of the source resource as closely as
possible. Since the environment at the destination may be different
than at the source due to factors outside the scope of control of
the server, such as the absence of resources required for correct
operation, it may not be possible to completely duplicate the
behavior of the resource at the destination. Subsequent alterations
to the destination resource will not modify the source resource.
Subsequent alterations to the source resource will not modify the
destination resource.
After a successful COPY invocation, all dead properties on the
source resource MUST be duplicated on the destination resource,
along with all properties as appropriate. Live properties described
in this document SHOULD be duplicated as identically behaving live
properties at the destination resource, but not necessarily with the
same values. Servers SHOULD NOT convert live properties into dead
properties on the destination resource, because clients may then draw
incorrect conclusions about the state or functionality of a resource.
Note that some live properties are defined such that the absence of the property
has a specific meaning (e.g. a flag with one meaning if present and the opposite if
absent), and in these cases, a successful COPY might result in the
property being reported as "Not Found" in subsequent requests.
A COPY operation creates a new resource, much like a PUT operation
does. Live properties which are related to resource creation (such
as DAV:creationdate) should have their values set accordingly.
The COPY method on a collection without a Depth header MUST act as
if a Depth header with value "infinity" was included. A client may
submit a Depth header on a COPY on a collection with a value of "0"
or "infinity". Servers MUST support the "0" and "infinity" Depth
header behaviors on WebDAV-compliant resources.
A COPY of depth infinity instructs that the collection resource
identified by the Request-URI is to be copied to the location
identified by the URI in the Destination header, and all its
internal member resources are to be copied to a location relative to
it, recursively through all levels of the collection hierarchy.
A COPY of "Depth: 0" only instructs that the collection and its
properties but not resources identified by its internal member URLs,
are to be copied.
Any headers included with a COPY MUST be applied in processing every
resource to be copied with the exception of the Destination header.
The Destination header only specifies the destination URI for the
Request-URI. When applied to members of the collection identified by
the Request-URI the value of Destination is to be modified to
reflect the current location in the hierarchy. So, if the Request-URI
is /a/ with Host header value http://example.com/ and the
Destination is http://example.com/b/ then when
http://example.com/a/c/d is processed it must use a Destination of
http://example.com/b/c/d.
When the COPY method has completed processing it MUST have created a
consistent URL namespace at the destination
(see for the
definition of namespace consistency). However, if an error occurs
while copying an internal collection, the server MUST NOT copy any
resources identified by members of this collection (i.e., the server
must skip this subtree), as this would create an inconsistent
namespace. After detecting an error, the COPY operation SHOULD try
to finish as much of the original copy operation as possible (i.e.,
the server should still attempt to copy other subtrees and their
members, that are not descendents of an error-causing collection).
So, for example, if an infinite depth copy operation is performed on
collection /a/, which contains collections /a/b/ and /a/c/, and an
error occurs copying /a/b/, an attempt should still be made to copy
/a/c/. Similarly, after encountering an error copying a non-collection
resource as part of an infinite depth copy, the server
SHOULD try to finish as much of the original copy operation as
possible.
If an error in executing the COPY method occurs with a resource
other than the resource identified in the Request-URI then the
response MUST be a 207 (Multi-Status), and the URL of the resource
causing the failure MUST appear with the specific error.
The 424 (Failed Dependency) status code SHOULD NOT be returned in
the 207 (Multi-Status) response from a COPY method. These responses
can be safely omitted because the client will know that the progeny
of a resource could not be copied when the client receives an error
for the parent. Additionally 201 (Created)/204 (No Content) status
codes SHOULD NOT be returned as values in 207 (Multi-Status)
responses from COPY methods. They, too, can be safely omitted
because they are the default success codes.
If a COPY request has an Overwrite header with a value of "F",
and a resource exists at the Destination URL, the server MUST fail
the request.
When a server executes a COPY request and overwrites a destination
resource, the exact behavior MAY depend on many factors, including
WebDAV extension capabilities (see particularly ).
Some considerations:
When an ordinary resource is overwritten, the server could
delete the target resource before doing the copy, or could
do an in-place overwrite to preserve live properties.When a collection is overwritten, the source collection
membership could completely replace the destination collection
membership, or the source collection membership could be combined
with the destination collection membership.In general, if clients require the state of the destination URL to be
wiped out prior to a COPY (e.g. to force live properties to be reset or to
force collection membership to be reset), then the client could send a
DELETE to the destination before the COPY request to ensure this reset.
In addition to the general status codes possible, the following
status codes have specific applicability to COPY:
201 (Created) - The source resource was successfully copied. The
COPY operation resulted in the creation of a new resource.
204 (No Content) - The source resource was successfully copied to a
pre-existing destination resource.
207 (Multi-Status) - Multiple resources were to be affected by the
COPY, but errors on some of them prevented the operation from taking
place. Specific error messages, together with the most appropriate
of the source and destination URLs, appear in the body of the multi-status
response. E.g. if a destination resource was locked and could
not be overwritten, then the destination resource URL appears with
the 423 (Locked) status.
403 (Forbidden) - The operation is forbidden. A special case for COPY
could be that the source and destination resources are the same resource.
409 (Conflict) - A resource cannot be created at the destination
until one or more intermediate collections have been created. The
server MUST NOT create those intermediate collections automatically.
412 (Precondition Failed) - A precondition header check failed, e.g. the
Overwrite header is "F" and the destination URL is already mapped to a resource.
423 (Locked) - The destination resource, or resource within the destination
collection, was locked. This response SHOULD
contain the 'lock-token-present' precondition element.
502 (Bad Gateway) - This may occur when the destination is on
another server, repository or URL namespace. Either the source
namespace does not support copying to the destination namespace, or
the destination namespace refuses to accept the resource. The client
may wish to try GET/PUT and PROPFIND/PROPPATCH instead.
507 (Insufficient Storage) - The destination resource does not have
sufficient space to record the state of the resource after the
execution of this method.
This example shows resource
http://www.ics.uci.edu/~fielding/index.html being copied to the
location http://www.ics.uci.edu/users/f/fielding/index.html. The
204 (No Content) status code indicates the existing resource at the
destination was overwritten.
The following example shows the same copy operation being performed,
but with the Overwrite header set to "F." A response of 412
(Precondition Failed) is returned because the destination URL is already mapped to a resource.
The Depth header is unnecessary as the default behavior of COPY on a
collection is to act as if a "Depth: infinity" header had been
submitted. In this example most of the resources, along with the
collection, were copied successfully. However the collection R2
failed because the destination R2 is locked. Because there was an
error copying R2, none of R2's members were copied. However no
errors were listed for those members due to the error minimization
rules.
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.
Live properties described in this document SHOULD be moved along with
the resource, such that the resource has identically behaving live
properties at the destination resource, but not necessarily with the
same values.
Note that some live properties are defined such that the absence of the property
has a specific meaning (e.g. a flag with one meaning if present and the opposite if
absent), and in these cases, a successful MOVE might result in the
property being reported as "Not Found" in subsequent requests.
If the live properties will not work the same way at
the destination, the server MAY fail the request.
MOVE is frequently used by clients to rename a file without changing
its parent collection, so it's not appropriate to reset all live
properties which are set at resource creation. For example, the
DAV:creationdate property value SHOULD remain the same after a MOVE.
Dead properties MUST be moved along with the resource.
A MOVE with "Depth: infinity" instructs that the collection
identified by the Request-URI be moved to the address specified in
the Destination header, and all resources identified by its internal
member URLs are to be moved to locations relative to it, recursively
through all levels of the collection hierarchy.
The MOVE method on a collection MUST act as if a "Depth: infinity"
header was used on it. A client MUST NOT submit a Depth header on a
MOVE on a collection with any value but "infinity".
Any headers included with MOVE MUST be applied in processing every
resource to be moved with the exception of the Destination header.
The behavior of the Destination header is the same as given for COPY
on collections.
When the MOVE method has completed processing it MUST have created a
consistent URL namespace at both the source and destination (see section
5.1 for the definition of namespace consistency). However, if an
error occurs while moving an internal collection, the server MUST
NOT move any resources identified by members of the failed
collection (i.e., the server must skip the error-causing subtree),
as this would create an inconsistent namespace. In this case, after
detecting the error, the move operation SHOULD try to finish as much
of the original move as possible (i.e., the server should still
attempt to move other subtrees and the resources identified by their
members, that are not descendents of an error-causing collection).
So, for example, if an infinite depth move is performed on
collection /a/, which contains collections /a/b/ and /a/c/, and an
error occurs moving /a/b/, an attempt should still be made to try
moving /a/c/. Similarly, after encountering an error moving a non-collection
resource as part of an infinite depth move, the server
SHOULD try to finish as much of the original move operation as
possible.
If an error occurs with a resource other than the resource
identified in the Request-URI then the response MUST be a 207
(Multi-Status), and the errored resource's URL MUST appear with the
specific error.
The 424 (Failed Dependency) status code SHOULD NOT be returned in
the 207 (Multi-Status) response from a MOVE method. These errors
can be safely omitted because the client will know that the progeny
of a resource could not be moved when the client receives an error
for the parent. Additionally 201 (Created)/204 (No Content)
responses SHOULD NOT be returned as values in 207 (Multi-Status)
responses from a MOVE. These responses can be safely omitted
because they are the default success codes.
If a resource exists at the destination and the Overwrite header is
"T" then prior to performing the move the server MUST perform a
DELETE with "Depth: infinity" on the destination resource. If the
Overwrite header is set to "F" then the operation will fail.
In addition to the general status codes possible, the following
status codes have specific applicability to MOVE:
201 (Created) - The source resource was successfully moved, and a
new URL mapping was created at the destination.
204 (No Content) - The source resource was successfully moved to a URL
that was already mapped.
207 (Multi-Status) - Multiple resources were to be affected by the
MOVE, but errors on some of them prevented the operation from taking
place. Specific error messages, together with the most appropriate
of the source and destination URLs, appear in the body of the multi-status
response. E.g. if a source resource was locked and could not
be moved, then the source resource URL appears with the 423 (Locked)
status.
403 (Forbidden) - Among many possible reasons for forbidding a MOVE operation,
this status code is recommended for use when the source and destination
resources are the same.
409 (Conflict) - A resource cannot be created at the destination
until one or more intermediate collections have been created. The
server MUST NOT create those intermediate collections automatically.
Or, the server was unable to
preserve the behavior of the live properties and still move the
resource to the destination (see 'preserved-live-properties' postcondition).
412 (Precondition Failed) - A condition header failed. Specific to MOVE, this could
mean that the Overwrite
header is "F" and the state of the destination URL is already mapped to a resource.
423 (Locked) - The source or the destination resource, the source or destination
resource parent, or some resource
within the source or destination collection, was locked. This response SHOULD
contain the 'lock-token-present' precondition element.
502 (Bad Gateway) - This may occur when the destination is on
another server and the destination server refuses to accept the
resource. This could also occur when the destination is on another
sub-section of the same server namespace.
This example shows resource
http://www.ics.uci.edu/~fielding/index.html being moved to the
location http://www.ics.uci.edu/users/f/fielding/index.html. The
contents of the destination resource would have been overwritten if
the destination URL was already mapped to a resource. In this case, since
there was nothing at the destination resource, the response code is
201 (Created).
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.
When a new lock is created, the LOCK response: MUST contain a body with the value of the
DAV:lockdiscovery property in a prop XML element. This MUST
contain the full information about the lock just granted, while
information about other (shared) locks is OPTIONAL.MUST include the Lock-Token response header with the
token associated with the new lock.
A lock is refreshed by sending a LOCK request without a request body to the URL
of a resource within the scope of the lock. This request MUST specify which lock
to refresh by using the 'Lock-Token' header with a single lock token (only one
lock may be refreshed at a time). It MAY contain a Timeout header, which a
server MAY accept to change the duration remaining on the lock to the new value.
A server MUST ignore the Depth header on a LOCK refresh.
If the resource has other (shared) locks, those locks are unaffected
by a lock refresh. Additionally, those locks do not prevent the
named lock from being refreshed.
Note that in RFC2518, clients were indicated through the example in
the text to use the If header to specify what lock to refresh
(rather than the Lock-Token header). Servers are encouraged to
continue to support this as well as the Lock-Token header.
Note that the
Lock-Token header is not be returned in the response for a
successful refresh LOCK request, but the LOCK response body MUST
contain the new value for the DAV:lockdiscovery body.
The Depth header may be used with the LOCK method. Values other
than 0 or infinity MUST NOT be used with the Depth header on a LOCK
method. All resources that support the LOCK method MUST support the
Depth header.
A Depth header of value 0 means to just lock the resource specified
by the Request-URI.
If the Depth header is set to infinity then the resource specified
in the Request-URI along with all its internal members, all the way
down the hierarchy, are to be locked. A successful result MUST
return a single lock token which represents all the resources that
have been locked. If an UNLOCK is successfully executed on this
token, all associated resources are unlocked.
Hence, partial success is not an option. Either the
entire hierarchy is locked or no resources are locked.
If the lock cannot be granted to all resources, the server MUST return
a Multi-Status response with a 'response' element for
at least one resource which prevented the lock from being granted,
along with a suitable status code for that failure (e.g. 403 (Forbidden) or
423 (Locked)). Additionally, if the resource causing the failure was not the
resource requested, then the server MUST include a 'response' element
for the Request-URI as well, with a 'status' element containing 424 Failed Dependency.
If no Depth header is submitted on a LOCK request then the request
MUST act as if a "Depth:infinity" had been submitted.
A successful LOCK method MUST result in the creation of an empty
resource which is locked (and which is not a collection), when a
resource did not previously exist at that URL. Later on, the lock
may go away but the empty resource remains. Empty resources MUST
then appear in PROPFIND responses including that URL in the response
scope. A server MUST respond successfully to a GET request to an
empty resource, either by using a 204 No Content response, or by
using 200 OK with a Content-Length header indicating zero length and
no Content-Type.
The table below describes the behavior that occurs when a lock
request is made on a resource.
Current StateShared Lock OKExclusive Lock OKNoneTrueTrueShared LockTrueFalseExclusive LockFalseFalse*
Legend: True = lock may be granted. False = lock MUST NOT be
granted. *=It is illegal for a principal to request the same lock
twice.
The current lock state of a resource is given in the leftmost
column, and lock requests are listed in the first row. The
intersection of a row and column gives the result of a lock request.
For example, if a shared lock is held on a resource, and an
exclusive lock is requested, the table entry is "false", indicating
the lock must not be granted.
In addition to the general status codes possible, the following
status codes have specific applicability to LOCK:
200 (OK) - The LOCK request succeeded and the value of the
DAV:lockdiscovery property is included in the response body.
201 (Created) - The LOCK request was to an unmapped URL, the request
succeeded and resulted in the creation of a new resource, and the
value of the DAV:lockdiscovery property is included in the response body.
409 (Conflict) - A resource cannot be created at the destination
until one or more intermediate collections have been created. The
server MUST NOT create those intermediate collections automatically.
423 (Locked) - The resource is locked already.
400 (Bad Request), with 'lock-token-matches-request-uri' precondition code -
The LOCK request was made with a Lock-Token header, indicating that the
client wishes to refresh the given lock. However, the Request-URI did not
fall within the scope of the lock identified by the token. The lock may have
a scope that does not include the Request-URI, or the lock could have disappeared,
or the token may be invalid.
This example shows the successful creation of an exclusive write
lock on resource http://example.com/workspace/webdav/proposal.doc.
The resource http://www.ics.uci.edu/~ejw/contact.html contains
contact information for the owner of the lock. The server has an
activity-based timeout policy in place on this resource, which
causes the lock to automatically be removed after 1 week (604800
seconds). Note that the nonce, response, and opaque fields have not
been calculated in the Authorization request header.
This example shows a request for an exclusive write lock on a
collection and all its children. In this request, the client has
specified that it desires an infinite length lock, if available,
otherwise a timeout of 4.1 billion seconds, if available. The
request entity body contains the contact information for the
principal taking out the lock, in this case a web page URL.
The error is a 403 (Forbidden) response on the resource
http://example.com/webdav/secret. Because this resource could not
be locked, none of the resources were locked. Note also that the
a 'response' element for the Request-URI itself has been included as
required.
In this example, the nonce, response, and opaque fields have not
been calculated in the Authorization request header.
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 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 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.
In addition to the general status codes possible, the following
status codes have specific applicability to UNLOCK:
204 (No Content) - Normal success response (rather than 200 OK, since 200 OK
would imply a response body, and an UNLOCK success response does not
normally contain a body)
400 (Bad Request) - No lock token was provided (see 'lock-token-present' precondition),
or request was made to a Request-URI that was not within the scope of the lock
(see 'lock-token-matches-request-uri' precondition).
403 (Forbidden) - The currently authenticated principal does not have permission
to remove the lock.
409 (Conflict) - The resource was not locked and thus could not be unlocked.
In this example, the lock identified by the lock token
"urn:uuid:a515cfa4-5da4-22e1-f5b5-00a0451e6bf7" is
successfully removed from the resource
http://example.com/workspace/webdav/info.doc. If this lock included
more than just one resource, the lock is removed from all resources
included in the lock. The 204 (No Content) status code is used
instead of 200 (OK) because there is no response entity body.
In this example, the nonce, response, and opaque fields have not
been calculated in the Authorization request header.
All DAV headers follow the same basic formatting rules as HTTP
headers. This includes rules like line continuation and how to
combine (or separate) multiple instances of the same header using
commas. WebDAV adds two new conditional headers to the set defined in HTTP:
the If and Overwrite headers.
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.
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 URL namespaces.
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.
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.
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 absolute-URI production is
defined in .
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.
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 . 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 an example of a state token that will never
match an actual valid lock token. The purpose of this is described
in .
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 absolute-URI production is defined in .
The No-tag-list production describes a series of state tokens and
ETags. If multiple No-tag-list productions are used then one only
needs to match the state of the resource for the method to be
allowed to continue. All untagged tokens apply to the resource
identified in the Request-URI.
The previous header would require that the resource identified in
the Request-URI be locked with the specified lock token and in the
state identified by the "I am an ETag" ETag or in the state
identified by the second ETag "I am another ETag". To put the
matter more plainly one can think of the previous If header as being
in the form (or (and <urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> ["I am an
ETag"]) (and ["I am another ETag"])).
The tagged-list production may be used instead of the no-tag-list production,
in order to scope each token to a specific resource. That is, it
specifies that the lists following the resource specification only
apply to the specified resource. The scope of the resource
production begins with the list production immediately following the
resource production and ends with the next resource production, if
any. All clauses must be evaluated. If
the state of the resource named in the tag does not
match any of the associated state lists then the request MUST fail
with a 412 (Precondition Failed).
The same URI MUST NOT appear more than once in a resource production
in an If header.
In this example http://www.example.com/resource1 is being copied to
http://www.example.com/resource2. When the method is first applied
to http://www.example.com/resource1, resource1 must be in the state
specified by "(<urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> [W/"A weak ETag"])
(["strong ETag"])", that is, it either must be locked with a lock
token of "urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2" and have a weak entity tag
W/"A weak ETag" or it must have a strong entity tag "strong ETag".
That is the only success condition since the resource
http://www.example.com/random never has the method applied to it (the
only other resource listed in the If header) and
http://www.example.com/resource2 is not listed in the If header.
Every state token or ETag is either current, and hence describes the
state of a resource, or is not current, and does not describe the
state of a resource. The boolean operation of matching a state token
or ETag to the current state of a resource thus resolves to a true
or false value. The "Not" production is used to reverse that value.
The scope of the not production is the state-token or entity-tag
immediately following it.
When submitted with a request, this If header requires that all
operand resources must not be locked with
urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2 and must
be locked with urn:uuid:58f202ac-22cf-11d1-b12d-002035b29092.
The Not production is particularly useful with the "<DAV:no-lock>"
state token. The clause "Not <DAV:no-lock>" MUST evaluate to true.
Thus, any "OR" statement containing the clause "Not <DAV:no-lock>"
MUST also evaluate to true.
When performing If header processing, the definition of a matching
state token or entity tag is as follows.
Identifying a resource: The resource is identified by the URI
along with the token, in tagged list production, or by the
Request-URI in untagged list production.
Matching entity tag: Where the entity tag matches an entity tag
associated with the identified resource.
Matching state token: Where there is an exact match between the
state token in the If header and any state token on the identified resource.
A lock state token is considered to match if the resource is anywhere
in the scope of the lock.
Non-DAV aware proxies will not honor the If header, since they will
not understand the If header, and HTTP requires non-understood
headers to be ignored. When communicating with HTTP/1.1 proxies,
the "Cache-Control: no-cache" request header MUST be used so as to
prevent the proxy from improperly trying to service the request from
its cache. When dealing with HTTP/1.0 proxies the "Pragma: no-cache"
request header MUST be used for the same reason.
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.
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 state of 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 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 following status codes are added to those defined in HTTP/1.1
.
The 207 (Multi-Status) status code provides status for multiple
independent operations (see
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 'lock-token-present' precondition 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.
These HTTP codes are not redefined, but their use is somewhat extended by
WebDAV methods and requirements. In general, many HTTP status codes can be
used in response to any request, not just in cases described in this document.
Note also that WebDAV servers are known
to use 300-level redirect responses (and early interoperability tests found clients
unprepared to see those responses).
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 request contains a conditional
header, and if that condition fails to hold, then this error code MUST
be returned unless some other error is returned. On the other hand,
if the client did not include a conditional header in the request,
then the server MUST NOT use this error.
This status code is used in HTTP 1.1 only for Request-URIs, because
full URIs aren't 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.
A Multi-Status response 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.
The default 207 (Multi-Status) response body is a text/xml or
application/xml HTTP entity that contains a single XML element
called 'multistatus', which contains a set of XML elements called
response which contain 200, 300, 400, and 500 series status codes
generated during the method invocation. 100 series status codes
SHOULD NOT be recorded in a 'response' XML element. The 207 status
code itself MUST NOT be considered a success response, it is only
completely successful if all 'response' elements inside contain
success status codes.
The body of a 207 Multi-Status response MUST contain a URL
associated with each specific status code, so that the client can
tell whether the error occurred with the source resource,
destination resource or some other resource in the scope of the
request.
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.
A Multi-Status body contains one or more 'response' elements. Each response element
describes a resource, and has an 'href' element identifying the resource.
The 'href' element MUST contain an absolute URI or relative reference.
It MUST NOT include "." or ".." as path elements.
If a 'href' element contains a relative reference, it MUST be resolved against the
Request-URI. A relative reference MUST be an absolute path (note that clients are not
known to support relative paths).
Identifiers for collections appearing in the results SHOULD end in
a '/' character.
If a server allows resource names to include characters that aren't
legal in HTTP URL paths, these characters must be percent-encoded on the
wire (see , section 2.1).
For example, it is illegal to use a space character or double-quote
in a URI. 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.
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 ).
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., ,
, and
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.
In this section, the final line of each section gives the
element type declaration using the format defined in
. The
"Value" field, where present, specifies further restrictions on the
allowable contents of the XML element using BNF (i.e., to further
restrict the values of a PCDATA element). The "Extensibility" field
discusses how the element may be extended in the future (or in
existing extensions to WebDAV.
All of the elements defined here may be extended by the addition of
attributes and child elements not defined in this specification. All
elements defined here are in the "DAV:" namespace.
activelockDescribes a lock on a resource. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. allprop 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. Normally empty, but MAY be extended with additional
child elements or attributes which SHOULD be ignored if not
recognized. collection 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. MAY be extended with child elements or attributes
which SHOULD be ignored if not recognized. dead-props Specifies that all dead
properties, names and values, should be returned in the
response. Normally empty, but MAY be extended with additional
child elements or attributes which SHOULD be ignored if not
recognized. depthThe value of the Depth header. "0" | "1" | "infinity" MAY be extended with attributes which SHOULD be
ignored.errorError 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' element SHOULD include a standard precondition element defined in this
specification or another specification. The 'error' tag MAY include custom
error tags (in custom XML namespaces) which a client can safely ignore.Contains any XML element Fully extensible with additional child elements or
attributes which SHOULD be ignored if not recognized. exclusiveSpecifies an exclusive lock Normally empty, but MAY be extended with additional
child elements or attributes which SHOULD be ignored if not
recognized. hrefIdentifies the content of the element as a URI or a
relative reference. 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.URI (See section 3 of ) MAY be extended with attributes which SHOULD be
ignored if not recognized. location HTTP defines the "Location" header (section 14.30) to provide the new
URI in the response to a request for a single redirected resource.
When a redirection status code is used
in a Multi-Status response, this element MAY be used to provide that new URI.Contains a single href element with the same value that
would be used in a Location header.MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized.lockentry Defines the types of locks that can be used with the
resource. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. lockinfoThe 'lockinfo' XML element is used with a LOCK method to
specify the type of lock the client wishes to have created. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. lockroot Contains the root URL of the lock, which is the URL through
which the resource was addressed in the LOCK request. The href contains a HTTP URL with the address of the root of
the lock. The server SHOULD include this in all
DAV:lockdiscovery property values and the response to LOCK
requests. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. lockscopeSpecifies whether a lock is an exclusive lock, or a shared
lock. SHOULD NOT be extended with child elements. MAY be
extended with attributes which SHOULD be ignored. locktoken The lock token associated with a lock. The href contains a single lock token URI which refers
to the lock. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. locktypeSpecifies the access type of a lock. At present, this
specification only defines one lock type, the write lock. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. multistatusContains multiple response messages. 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. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. owner Provides information about the principal taking out a lock. 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. MAY be extended with child elements, mixed content,
text content or attributes. Structured content, for
example one or more 'href' child elements containing URIs of any kind,
is RECOMMENDED.propContains properties related to a resource. 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. 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. propertyupdate Contains a request to alter the properties on a resource. This XML element is a container for the
information required to modify the properties on the
resource. This XML element is multi-valued. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. propfind 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. 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. propname Specifies that only a list of
property names on the resource is to be returned. Normally empty, but MAY be extended with additional
child elements or attributes which SHOULD be ignored if not
recognized. propstat Groups together a prop and status element that is
associated with a particular 'href' element. 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. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. remove Lists the DAV properties to be removed from a resource.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. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. responseHolds a single response describing the effect of a method
on resource and/or its properties. The 'href' element contains a 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. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. responsedescription Contains information about a status response within a Multi-Status. This XML element provides either information suitable to be
presented to a user (PCDATA) or a machine readable error code.MAY be extended with additional attributes which SHOULD be
ignored if not recognized. set Lists the DAV property values to be set for a resource. 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. MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. sharedSpecifies a shared lockNormally empty, but MAY be extended with additional
child elements or attributes which SHOULD be ignored if not
recognized. status Holds a single HTTP status-line status-line (status-line defined in Section 6.1 of )
MAY be extended with attributes which SHOULD be
ignored. timeoutThe number of seconds remaining before a lock expires. TimeType (defined in ). MAY be extended with attributes which SHOULD be
ignored. writeSpecifies a write lock. Normally empty, but MAY be extended with additional
child elements or attributes which SHOULD be ignored if not
recognized.
For DAV properties, the name of the property is also the same as the
name of the XML element that contains its value. In the section
below, the final line of each section gives the element type
declaration using the format defined in .
The "Value"
field, where present, specifies further restrictions on the
allowable contents of the XML element using BNF (i.e., to further
restrict the values of a PCDATA element). 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 or PROPPATCH requests.
Some property values are calculated by the server and it is not
appropriate to allow client changes, thus they are protected.
Existing server implementations already have different sets of
RFC2518 properties protected, but clients can have some expectations
which properties are normally protected. The value of a protected
property may not be changed even by a user with permission to edit
other properties. The value of an unprotected property may be
changed by some users with appropriate permissions.
COPY and MOVE behavior refers to local COPY and MOVE operations.For properties defined based on HTTP GET response headers (DAV:get*),
the value could include LWS as defined in , section 4.2.
Server implementors SHOULD NOT include extra LWS in these values, however client
implementors MUST be prepared to handle extra LWS.creationdate Records the time and date the resource was created. date-time (defined in , see the ABNF in section
5.6.) 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). 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. 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")MAY contain attributes which SHOULD be ignored if not
recognized. displayname Provides a name for the resource that is suitable for
presentation to a user. Any text SHOULD NOT be protected This property value SHOULD be preserved in
COPY and MOVE operations. The DAV: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. MAY contain attributes which SHOULD be ignored if not
recognized. getcontentlanguage Contains the Content-Language header returned by a GET
without accept headers language-tag (language-tag is defined in section 14.13 of
) SHOULD NOT be protected, so that clients can reset the
language. This property value SHOULD be preserved in
COPY and MOVE operations. The DAV:getcontentlanguage property MUST be defined on any
DAV compliant resource that returns the Content-Language
header on a GET. MAY contain attributes which SHOULD be ignored if not
recognized. getcontentlength Contains the Content-Length header returned by a GET
without accept headers. content-length (see section 14.14 of ) SHOULD be protected so clients cannot set to misleading
values The DAV:getcontentlength property MUST be defined on any
DAV compliant resource that returns the Content-Length
header in response to a GET. This property value is dependent on the size of
the destination resource, not the value of the property on
the source resource. MAY contain attributes which SHOULD be ignored if not
recognized. getcontenttype Contains the Content-Type header returned by a GET without
accept headers. media-type (defined in section 3.7 of ) SHOULD NOT be protected, so clients may fix this value This property value SHOULD be preserved in
COPY and MOVE operations. This property MUST be defined on
any DAV compliant resource that returns the Content-Type
header in response to a GET. MAY contain attributes which SHOULD be ignored if not
recognized. getetag Contains the ETag header returned by a GET without accept
headers. entity-tag (defined in section 3.11 of ) MUST be protected because this value is created and
controlled by the server. This property value is dependent on the final
state of the destination resource, not the value of the
property on the source resource. 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 resource's ETag to change. MAY contain attributes which SHOULD be ignored if not
recognized. getlastmodified Contains the Last-Modified header returned by a GET method
without accept headers. rfc1123-date (defined in section 3.3.1 of ) 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. 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 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. 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 DAV:getlastmodified property MUST be defined
on any DAV compliant resource that returns the Last-Modified
header in response to a GET. MAY contain attributes which SHOULD be ignored if not
recognized. lockdiscoveryDescribes the active locks on a resource MUST be protected. Clients change the list of locks
through LOCK and UNLOCK, not through PROPPATCH. 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. 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
'activelock' elements. If there is one or more lock, an
'activelock' element appears for each lock on the resource.MAY be extended with additional child elements or
attributes which SHOULD be ignored if not recognized. resourcetype Specifies the nature of the resource. SHOULD be protected. Resource type is generally decided
through the operation creating the resource (MKCOL vs PUT),
not by PROPPATCH. Generally a COPY/MOVE of a resource results in
the same type of resource at the destination.MUST be defined on all DAV
compliant resources. The default value is empty. 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. supportedlockTo provide a listing of the lock capabilities supported by
the resource. MUST be protected. Servers determine what lock mechanisms
are supported, not clients. 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. 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. MAY be extended with any child elements or attributes
which SHOULD be ignored if not recognized.
The numerical status codes used in HTTP responses are not
sufficiently granular or informative for all purposes. Some extensions
to HTTP have used the error response body along with some status codes
in order to provide additional machine-readable response detail. The
machine-readable codes are XML elements classified as preconditions and
postconditions. Even if clients do not automatically recognize the error bodies
they can be quite useful in interoperability testing and debugging.A "precondition" of a method describes the state of the server that
must be true for that method to be performed. A "postcondition" of a
method describes the state of the server that must be true after that
method has been completed. If a method precondition or postcondition
for a request is not satisfied, the response status of the request
MUST be either 403 (Forbidden) if the request should not be repeated
because it will always fail, or 409 (Conflict) if it is expected that
the user might be able to resolve the conflict and resubmit the
request.
The XML element associated with the precondition or postcondition
MUST be returned as the child of a top-level
DAV:error element in the response body, unless otherwise negotiated
by the request. In a 207 Multi-Status response, the DAV:error
element would appear in the appropriate DAV:responsedescription
element.
Some useful preconditions and postconditions have been defined in other specifications
extending this one, such as (see particularly section 7.1.1),
, and .
All these elements are in the "DAV:" namespace.
no-external-entities403 Forbidden(precondition) -- If the server rejects a client
request because the request body contains an external entity, the
server SHOULD use this error.
lock-token-matches-request-uri400 Bad Request(precondition) --
A request may include a Lock-Token header to identify a lock for the purposes of
an operation such as refresh LOCK or UNLOCK. However, if the Request-URI doe not
fall within the scope of the lock identified by the token, the server SHOULD use
this error. The lock may have
a scope that does not include the Request-URI, or the lock could have disappeared,
or the token may be invalid.preserved-live-properties409 Conflict(postcondition) -- The server received an
otherwise-valid MOVE or COPY request, but cannot maintain the live
properties with the same behavior at the destination.
It may be that the server only supports some live properties
in some parts of the repository, or simply has an internal error.
writable-property403 Forbidden(precondition) -- The client attempted to set
a read-only property in a PROPPATCH (such as DAV:getetag).
propfind-finite-depth403 Forbidden(precondition) -- This server does not allow
infinite-depth PROPFIND requests on collections.
lock-token-present4xx responses, e.g. 400 Bad Request or 423 Locked(precondition) -- The request could not succeed
because a lock token should have been provided. This element, if
present, MUST contain at least one URL of a locked resource that prevented
the request. In
cases of MOVE, COPY and DELETE where collection locks are involved,
it can be difficult for the client to find out which locked resource
made the request fail -- but the server is only resonsible for returning
one such locked resource. The server MAY return every locked resource
that prevented the request from succeeding if it knows them all.
All DAV compliant resources MUST ignore any unknown XML element and
all its children encountered while processing a DAV method that uses
XML as its command language.
This restriction also applies to the processing, by clients, of DAV
property values where unknown XML elements SHOULD be ignored unless
the property's schema declares otherwise.
This restriction does not apply to setting dead DAV properties on
the server where the server MUST record unknown XML elements.
Additionally, this restriction does not apply to the use of XML
where XML happens to be the content type of the entity body, for
example, when used as the body of a PUT.
Since XML can be transported as text/xml or application/xml, a DAV
server MUST accept DAV method requests with XML parameters
transported as either text/xml or application/xml, and a DAV client
MUST accept XML responses using either text/xml or application/xml.
XML DTD fragments are included for all the XML elements defined in
this specification. However, legal XML may not be valid according to
any DTD due to namespace usage and extension rules, so the DTD is
only informational. A recipient of a WebDAV message with an XML
body MUST NOT validate the XML document according to any hard-coded
or dynamically-declared DTD.
A DAV compliant resource can advertise several classes of
compliance. A client can discover the compliance classes of a
resource by executing OPTIONS on the resource, and examining the
"DAV" header which is returned. Note particularly that resources
are spoken of as being compliant, rather than servers. That is
because theoretically some resources on a server could support
different feature sets. E.g. a server could have a sub-repository
where an advanced feature like server was supported, even if that
feature was not supported on all servers.
Since this document describes extensions to the HTTP/1.1 protocol,
minimally all DAV compliant resources, clients, and proxies MUST be
compliant with .
A resource that is class 2 compliant must also be class 1 compliant,
and a resource that is compliant with "bis" must also be class 1
compliant.
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 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.
A resource that supports "bis" MUST support:
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.
In the realm of internationalization, this specification complies
with the IETF Character Set Policy . In this specification,
human-readable fields can be found either in the value of a
property, or in an error message returned in a response entity body.
In both cases, the human-readable content is encoded using XML,
which has explicit provisions for character set tagging and
encoding, and requires that XML processors read XML elements
encoded, at minimum, using the UTF-8 and UTF-16 encodings of
the ISO 10646 multilingual plane. XML examples in this
specification demonstrate use of the charset parameter of the
Content-Type header, as defined in , as well as the XML
declarations which provide charset identification information for
MIME and XML processors.
XML also provides a language tagging capability for specifying the
language of the contents of a particular XML element. The
"xml:lang" attribute appears on an XML element to identify the
language of its content and attributes. See for
definitions of values and scoping.
WebDAV applications MUST support the character set tagging,
character set encoding, and the language tagging functionality of
the XML specification. Implementors of WebDAV applications are
strongly encouraged to read "XML Media Types" for
instruction on which MIME media type to use for XML transport, and
on use of the charset parameter of the Content-Type header.
Names used within this specification fall into four categories:
names of protocol elements such as methods and headers, names of XML
elements, names of properties, and names of conditions. Naming of
protocol elements follows the precedent of HTTP, using English names
encoded in USASCII for methods and headers. Since these protocol
elements are not visible to users, and are simply long token
identifiers, they do not need to support multiple languages.
Similarly, the names of XML elements used in this specification are
not visible to the user and hence do not need to support multiple
languages.
WebDAV property names are qualified XML names (pairs of XML
namespace name and local name). Although some applications (e.g., a
generic property viewer) will display property names directly to
their users, it is expected that the typical application will use a
fixed set of properties, and will provide a mapping from the
property name and namespace to a human-readable field when
displaying the property name to a user. It is only in the case
where the set of properties is not known ahead of time that an
application need display a property name to a user. We recommend
that applications provide human-readable property names wherever
feasible.
For error reporting, we follow the convention of HTTP/1.1 status
codes, including with each status code a short, English description
of the code (e.g., 423 (Locked)). While the possibility exists that
a poorly crafted user agent would display this message to a user,
internationalized applications will ignore this message, and display
an appropriate message in the user's language and character set.
Since interoperation of clients and servers does not require locale
information, this specification does not specify any mechanism for
transmission of this information.
This section is provided to detail issues concerning security
implications of which WebDAV applications need to be aware.
All of the security considerations of HTTP/1.1 (discussed in
) and XML (discussed in
) also apply to WebDAV. In
addition, the security risks inherent in remote authoring require
stronger authentication technology, introduce several new privacy
concerns, and may increase the hazards from poor server design.
These issues are detailed below.
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
. 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. 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 , 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. 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 .
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
(no-external-entities).
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.
Furthermore, there's also a risk based on the evaluation of "internal entities"
as defined in section 4.2.2 of .
A small, carefully crafted request using nested internal entities
may require enormous amounts of memory and/or processing time to process. Server
implementors 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" () for lock tokens
, in order to guarantee
their uniqueness across space and time.
Variant 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".
There are several risks associated with exposure of IEEE 802 addresses. Using
the 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 describes several other mechanisms for generating
UUIDs that do involve the host address and therefore do not suffer
from this risk.
HTTP has the ability to host scripts which are executed on client machines.
These scripts can be used to read another user's cookies and therefore may
provide an attacker the ability to use another user's session, assume their
identity temporarily and gain access to their resources. Other attacks are
also possible with client-executed scripts.WebDAV may worsen this situation only by making it easier for a Web server
to host content provided by many different authors (making it harder to trust
the content providers) and to host content with restricted access alongside
public pages (see particularly RFC3744).HTTP servers may mitigate some of these threats by filtering content in
areas where many authors contribute pages -- the server could, for example,
remove script from HTML pages.This vulnerability should provide yet another reason for server implementors
and administrators not to replace authentication mechanisms with cookie-based
session tokens if there's any sensitive information relying on the authenticated
identity. HTTP and WebDAV client implementors might consider locking down the use of
scripts and cookies based on these considerations.
This specification defines two URI schemes:
the "opaquelocktoken" scheme defined in , and
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.
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.
A specification such as this thrives on piercing critical review and
withers from apathetic neglect. The authors gratefully acknowledge
the contributions of the following people, whose insights were so
valuable at every stage of our work.
Contributors to RFC2518
Terry Allen, Harald Alvestrand, Jim Amsden, Becky Anderson, Alan
Babich, Sanford Barr, Dylan Barrell, Bernard Chester, Tim Berners-Lee,
Dan Connolly, Jim Cunningham, Ron Daniel, Jr., Jim Davis, Keith
Dawson, Mark Day, Brian Deen, Martin Duerst, David Durand, Lee
Farrell, Chuck Fay, Wesley Felter, Roy Fielding, Mark Fisher, Alan
Freier, George Florentine, Jim Gettys, Phill Hallam-Baker, Dennis
Hamilton, Steve Henning, Mead Himelstein, Alex Hopmann, Andre van
der Hoek, Ben Laurie, Paul Leach, Ora Lassila, Karen MacArthur,
Steven Martin, Larry Masinter, Michael Mealling, Keith Moore, Thomas
Narten, Henrik Nielsen, Kenji Ota, Bob Parker, Glenn Peterson, Jon
Radoff, Saveen Reddy, Henry Sanders, Christopher Seiwald, Judith
Slein, Mike Spreitzer, Einar Stefferud, Greg Stein, Ralph Swick,
Kenji Takahashi, Richard N. Taylor, Robert Thau, John Turner, Sankar
Virdhagriswaran, Fabio Vitali, Gregory Woodhouse, and Lauren Wood.
Two from this list deserve special mention. The contributions by
Larry Masinter have been invaluable, both in helping the formation
of the working group and in patiently coaching the authors along the
way. In so many ways he has set high standards we have toiled to
meet. The contributions of Judith Slein in clarifying the
requirements, and in patiently reviewing draft after draft, both
improved this specification and expanded our minds on document
management.
We would also like to thank John Turner for developing the XML DTD.
The authors of RFC2518 were Yaron Goland, Jim Whitehead, A. Faizi,
Steve Carter and D. Jensen. Although their names had to be removed
due to IETF author count restrictions they can take credit for the
majority of the design of WebDAV.
Additional Contributors to This Specification
Valuable contributions to this specification came from some already named.
New contributors must also be gratefully acknowledged. Julian
Reschke, Geoff Clemm, Joel Soderberg, and Dan Brotsky hashed out
specific text on the list or in meetings. Ilya Kirnos supplied text
for Force-Authentication header. Joe Hildebrand contributed as
co-chair. Barry Lind described an additional security consideration.
Jason Crawford tracked issue status for this document for a period of
years, followed by Elias Sinderson.
Y. Y. Goland,
Microsoft Corporation,
One Microsoft Way,
Redmond, WA 98052-6399.
Email: yarong@microsoft.com.
E. J. Whitehead, Jr.,
Dept. Of Information and Computer Science,
University of California, Irvine,
Irvine, CA 92697-3425.
Email: ejw@ics.uci.edu.
A. Faizi,
Netscape,
685 East Middlefield Road,
Mountain View, CA 94043.
Email: asad@netscape.com.
S. R. Carter,
Novell,
1555 N. Technology Way,
M/S ORM F111,
Orem, UT 84097-2399.
Email: srcarter@novell.com.
D. Jensen,
Novell,
1555 N. Technology Way,
M/S ORM F111,
Orem, UT 84097-2399.
Email: dcjensen@novell.com.
Key words for use in RFCs to Indicate Requirement LevelsHarvard University1350 Mass. Ave.CambridgeMA 02138- +1 617 495 3864sob@harvard.edu
General
keyword
In many standards track documents several words are used to signify
the requirements in the specification. These words are often
capitalized. This document defines these words as they should be
interpreted in IETF documents. Authors who follow these guidelines
should incorporate this phrase near the beginning of their document:
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
RFC 2119.
Note that the force of these words is modified by the requirement
level of the document in which they are used.
IETF Policy on Character Sets and LanguagesUNINETTP.O.Box 6883 ElgeseterN-7002 TRONDHEIMNORWAY+47 73 59 70 94Harald.T.Alvestrand@uninett.no
Applications
Internet Engineering Task Forcecharacter encodingHypertext Transfer Protocol -- HTTP/1.1Department of Information and Computer ScienceUniversity of California, IrvineIrvineCA92697-3425+1(949)824-1715fielding@ics.uci.eduWorld Wide Web ConsortiumMIT Laboratory for Computer Science, NE43-356545 Technology SquareCambridgeMA02139+1(617)258-8682jg@w3.orgCompaq Computer CorporationWestern Research Laboratory250 University AvenuePalo AltoCA94305mogul@wrl.dec.comWorld Wide Web ConsortiumMIT Laboratory for Computer Science, NE43-356545 Technology SquareCambridgeMA02139+1(617)258-8682frystyk@w3.orgXerox CorporationMIT Laboratory for Computer Science, NE43-3563333 Coyote Hill RoadPalo AltoCA94034masinter@parc.xerox.comMicrosoft Corporation1 Microsoft WayRedmondWA98052paulle@microsoft.comWorld Wide Web ConsortiumMIT Laboratory for Computer Science, NE43-356545 Technology SquareCambridgeMA02139+1(617)258-8682timbl@w3.org
The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypermedia information
systems. It is a generic, stateless, protocol which can be used for
many tasks beyond its use for hypertext, such as name servers and
distributed object management systems, through extension of its
request methods, error codes and headers . A feature of HTTP is
the typing and negotiation of data representation, allowing systems
to be built independently of the data being transferred.
HTTP has been in use by the World-Wide Web global information
initiative since 1990. This specification defines the protocol
referred to as "HTTP/1.1", and is an update to RFC 2068 .
HTTP Authentication: Basic and Digest Access AuthenticationNorthwestern University, Department of MathematicsNorthwestern UniversityEvanstonIL60208-2730USAjohn@math.nwu.eduVerisign Inc.301 Edgewater PlaceSuite 210WakefieldMA01880USApbaker@verisign.comAbiSource, Inc.6 Dunlap CourtSavoyIL61874USAjeff@AbiSource.comAgranat Systems, Inc.5 Clocktower PlaceSuite 400MaynardMA01754USAlawrence@agranat.comMicrosoft Corporation1 Microsoft WayRedmondWA98052USApaulle@microsoft.comNetscape Communications Corporation501 East Middlefield RoadMountain ViewCA94043USAOpen Market, Inc.215 First StreetCambridgeMA02142USAstewart@OpenMarket.com
"HTTP/1.0", includes the specification for a Basic Access
Authentication scheme. This scheme is not considered to be a secure
method of user authentication (unless used in conjunction with some
external secure system such as SSL ), as the user name and
password are passed over the network as cleartext.
This document also provides the specification for HTTP's
authentication framework, the original Basic authentication scheme
and a scheme based on cryptographic hashes, referred to as "Digest
Access Authentication". It is therefore also intended to serve as a
replacement for RFC 2069 . Some optional elements specified by
RFC 2069 have been removed from this specification due to problems
found since its publication; other new elements have been added for
compatibility, those new elements have been made optional, but are
strongly recommended.
Like Basic, Digest access authentication verifies that both parties
to a communication know a shared secret (a password); unlike Basic,
this verification can be done without sending the password in the
clear, which is Basic's biggest weakness. As with most other
authentication protocols, the greatest sources of risks are usually
found not in the core protocol itself but in policies and procedures
surrounding its use.
Date and Time on the Internet: TimestampsClearswift Corporation1310 WatersideArlington Business ParkThealeReadingRG7 4SAUK+44 11 8903 8903+44 11 8903 9000GK@ACM.ORGSun Microsystems1050 Lakes Drive, Suite 250West CovinaCA91790USAchris.newman@sun.com
This document defines a date and time format for use in Internet
protocols that is a profile of the ISO 8601 standard for
representation of dates and times using the Gregorian calendar.
UTF-8, a transformation format of ISO 10646ISO/IEC 10646-1 defines a large character set called the Universal Character Set (UCS) which encompasses most of the world's writing systems. The originally proposed encodings of the UCS, however, were not compatible with many current applications and protocols, and this has led to the development of UTF-8, the object of this memo. UTF-8 has the characteristic of preserving the full US-ASCII range, providing compatibility with file systems, parsers and other software that rely on US-ASCII values but are transparent to other values. This memo obsoletes and replaces RFC 2279. Uniform Resource Identifier (URI): Generic SyntaxWorld Wide Web ConsortiumMassachusetts Institute of Technology77 Massachusetts AvenueCambridgeMA02139USA+1-617-253-5702+1-617-258-5999timbl@w3.orghttp://www.w3.org/People/Berners-Lee/Day Software5251 California Ave., Suite 110IrvineCA92617USA+1-949-679-2960+1-949-679-2972fielding@gbiv.comhttp://roy.gbiv.com/Adobe Systems Incorporated345 Park AveSan JoseCA95110USA+1-408-536-3024LMM@acm.orghttp://larry.masinter.net/
Applications
uniform resource identifierURIURLURNWWWresource
A Uniform Resource Identifier (URI) is a compact sequence of characters
that identifies an abstract or physical resource. This specification
defines the generic URI syntax and a process for resolving URI references
that might be in relative form, along with guidelines and security
considerations for the use of URIs on the Internet.
The URI syntax defines a grammar that is a superset of all valid URIs,
allowing an implementation to parse the common components of a URI
reference without knowing the scheme-specific requirements of every
possible identifier. This specification does not define a generative
grammar for URIs; that task is performed by the individual
specifications of each URI scheme.
A Universally Unique IDentifier (UUID) URN NamespaceMicrosoft1 Microsoft WayRedmondWA98052US+1 425-882-8080paulle@microsoft.comRefactored Networks, LLC1635 Old Hwy 41Suite 112, Box 138KennesawGA30152US+1-678-581-9656michael@refactored-networks.comhttp://www.refactored-networks.comDataPower Technology, Inc.1 Alewife CenterCambridgeMA02142US+1 617-864-0455rsalz@datapower.comhttp://www.datapower.comURN, UUIDThis specification defines a Uniform Resource Name namespace for
UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally
Unique IDentifier). A UUID is 128 bits long, and can
guarantee uniqueness across space and time. UUIDs were originally
used in the Apollo Network Computing System and later in the Open
Software Foundation's (OSF) Distributed Computing Environment (DCE),
and then in Microsoft Windows platforms.This specification is derived from the DCE specification with the
kind permission of the OSF (now known as The Open Group). Information from earlier versions of the DCE specification have been
incorporated into this document.Namespaces in XMLExtensible Markup Language (XML) 1.0 (Third Edition)Textuality and Netscapetbray@textuality.comMicrosoftjeanpa@microsoft.comUniversity of Illinois at Chicago and Text Encoding Initiativecmsmcq@uic.eduSun Microsystemseve.maler@east.sun.comfrancois@yergeau.comRequirements for a Distributed Authoring and Versioning Protocol for the World Wide WebXerox Corporation800 Phillips Road 128-29EWebsterNY14580slein@wrc.xerox.comDepartment of Computer Science, University of Bolognafabio@cs.unibo.itDept. Of Information and Computer Science,
University of California, IrvineIrvineCA92697-3425714-824-4056ejw@ics.uci.eduDepartment of Computer Science,
Boston UniversityBostonMAdgd@cs.bu.edu
Applications
Current World Wide Web (WWW or Web) standards provide simple support
for applications which allow remote editing of typed data. In
practice, the existing capabilities of the WWW have proven inadequate
to support efficient, scalable remote editing free of overwriting
conflicts. This document presents a list of features in the form of
requirements for a Web Distributed Authoring and Versioning protocol
which, if implemented, would improve the efficiency of common remote
editing operations, provide a locking mechanism to prevent overwrite
conflicts, improve link management support between non-HTML data
types, provide a simple attribute-value metadata facility, provide
for the creation and reading of container data types, and integrate
versioning into the WWW.
HTTP Extensions for Distributed Authoring -- WEBDAVMicrosoft CorporationOne Microsoft WayRedmondWA98052-6399yarong@microsoft.comDept. Of Information and Computer Science,
University of California, IrvineIrvineCA92697-3425ejw@ics.uci.eduNetscape685 East Middlefield RoadMountain ViewCA94043asad@netscape.comNovell1555 N. Technology WayM/S ORM F111OremUT84097-2399srcarter@novell.comNovell1555 N. Technology WayM/S ORM F111OremUT84097-2399dcjensen@novell.com
This document specifies a set of methods, headers, and content-types
ancillary to HTTP/1.1 for the management of resource properties,
creation and management of resource collections, namespace
manipulation, and resource locking (collision avoidance).
XML Media TypesThis document standardizes five new media types -- text/xml, application/xml, text/xml-external-parsed-entity, application/xml- external-parsed-entity, and application/xml-dtd -- for use in exchanging network entities that are related to the Extensible Markup Language (XML). This document also standardizes a convention (using the suffix '+xml') for naming media types outside of these five types when those media types represent XML MIME (Multipurpose Internet Mail Extensions) entities. [STANDARDS TRACK] Versioning Extensions to WebDAV (Web Distributed Authoring and Versioning)Rational Software20 Maguire RoadLexingtonMA02421USgeoffrey.clemm@rational.comIBM3039 CornwallisResearch Triangle ParkNC27709USjamsden@us.ibm.comIBMHursley ParkWinchesterS021 2JNUKtim_ellison@uk.ibm.comMicrosoftOne Microsoft WayRedmondWA90852USckaler@microsoft.comUC Santa Cruz, Dept. of Computer Science1156 High StreetSanta CruzCA95064USejw@cse.ucsc.edu
This document specifies a set of methods, headers, and resource types
that define the WebDAV (Web Distributed Authoring and Versioning)
versioning extensions to the HTTP/1.1 protocol. WebDAV versioning
will minimize the complexity of clients that are capable of
interoperating with a variety of versioning repository managers, to
facilitate widespread deployment of applications capable of utilizing
the WebDAV Versioning services. WebDAV versioning includes automatic
versioning for versioning-unaware clients, version history
management, workspace management, baseline management, activity
management, and URL namespace versioning.
Web Distributed Authoring and Versioning (WebDAV) Ordered Collections ProtocolUC Santa Cruz, Dept. of Computer Science1156 High StreetSanta CruzCA95064USejw@cse.ucsc.edugreenbytes GmbHSalzmannstrasse 152MuensterNW48159Germany+49 251 2807760+49 251 2807761julian.reschke@greenbytes.dehttp://greenbytes.de/tech/webdav/WEBDAV Working GroupWebDAVorderingordered collectionsprotocolORDERPATCH methodPosition headerOrdering-Type header
This specification extends the Web Distributed Authoring and Versioning (WebDAV) Protocol
to support the server-side ordering of collection members. Of particular
interest are orderings that are not based on property values, and so
cannot be achieved using a search protocol's ordering option and cannot
be maintained automatically by the server. Protocol elements are
defined to let clients specify the position in the ordering of each
collection member, as well as the semantics governing the ordering.
Web Distributed Authoring and Versioning (WebDAV) Access Control ProtocolIBM20 Maguire RoadLexingtonMA02421geoffrey.clemm@us.ibm.comgreenbytes GmbHSalzmannstrasse 152MuensterNW48159Germanyjulian.reschke@greenbytes.deOracle Corporation500 Oracle ParkwayRedwood ShoresCA94065eric.sedlar@oracle.comU.C. Santa Cruz, Dept. of Computer Science1156 High StreetSanta CruzCA95064ejw@cse.ucsc.edu
This document specifies a set of methods, headers, message bodies,
properties, and reports that define Access Control extensions to the
WebDAV Distributed Authoring Protocol. This protocol permits a client to
read and modify access control lists that instruct a server whether to
allow or deny operations upon a resource (such as HyperText Transfer
Protocol (HTTP) method invocations) by a given principal. A lightweight
representation of principals as Web resources supports integration of a
wide range of user management repositories. Search operations allow
discovery and manipulation of principals using human names.
XML Information Set (Second Edition)
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 white space, 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.
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.
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.
As the server does not understand the 'expired-props' element,
according to the WebDAV-specific XML processing rules specified in
, it must ignore it. Thus the server sees an empty
propfind, which by the definition of the propfind element is
illegal.
Please note that had the extension been additive it would not
necessarily have resulted in a 400 (Bad Request). For example,
imagine the following request body for a 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.
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 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.
The 'opaquelocktoken' URI scheme was defined in RFC2518 (and registered
by IANA) in order
to create syntactically correct and easy-to-generate URIs out of UUIDs,
intended to be used as lock tokens and to be unique across all
resources for all time.An opaquelocktoken URI is constructed by concatenating the 'opaquelocktoken'
scheme with a UUID, along with an optional extension.
Servers can create new UUIDs for each new lock token. If a server wishes to
reuse UUIDs the server MUST add an extension and
the algorithm generating the extension MUST guarantee that the same
extension will never be used twice with the associated UUID.
This section describes changes that are likely to result in implementation
changes due to tightened requirements or changed behavior.Tightened requirements for storing property
values when "xml:lang" appears and also when values are XML fragments
(specifically on preserving prefixes, namespaces and whitespace.)Several tightened requirements for general response
handling, including response bodies for use with errors,
ETag and Location header, and reminder to use Date header.Tightened requirements for URL construction in PROPFIND
responses. Tightened requirements for checking identity of lock
owners during operations affected by locks.Tightened requirements for copying properties
and moving properties.Tightened requirements on preserving owner field in locks.
Added "lockroot" element to lockdiscovery information.New value for "DAV:" header to advertise
support for this specification.Tightened requirement for "Destination:"
header to work with path valuesNew "Force-Authentication:" header added.Some changes for "If:" header, including
"DAV:no-lock" state token.Support for UTF-16 now required (ref).Removed definition of "source" property and special handling for dynamic resourcesReplaced lock-null resources with simpler
locked empty resources. Lock-null resources
are now not compliant with the requirements in this specification.Encouraged servers to change ETags
only when body of resource changes.The definition of the 102 Processing response was removed and servers ought
to stop sending that response when they implement this specification.Previously, servers were encouraged to return 409 status code in response to
a collection LOCK request if some resource could not be locked. Now servers
should use 207 Multi-Status instead.Only 'rfc1123-date' productions are legal as values for DAV:getlastmodified.Tightened requirements for supporting WebDAV
collections within resources that do not support WebDAV (e.g. servlet containers).Redefined 'allprop' PROPFIND requests so that the server does not have
to return all properties.Required to handle empty multistatus responses in PROPFIND
responsesNo more "propertybehavior" specification allowed in MOVE and COPY requestsThe change in behavior of LOCK with an unmapped URL might affect client implementations
that counted on lock-null resources disappearing when the lock expired. Clients can no
longer rely on that cleanup happening.Support for UTF-16 now required (ref).Removed definition of "source" property and special handling for dynamic resources.The definition of the 102 Processing response was removed and clients can safely
remove code (if any) that deals with this.Specified that a successful LOCK request to an unmapped URL creates a
new, empty locked resource.
Resolved UNLOCK_NEEDS_IF_HEADER by clarifying that only Lock-Token
header is needed on UNLOCK.Added on preconditions and postconditions
and defined a number of preconditions and postconditions. The 'lock-token-present'
precondition resolves the REPORT_OTHER_RESOURCE_LOCKED issue.Added example of matching lock token to URI in the case of a collection
lock in the If header section.Removed ability for Destination header to take "abs_path" in order
to keep consistent with other places where client provides URLs
(If header, href element in request body)Clarified the href element - that it generally contains HTTP URIs but not
always.Attempted to fix the BNF describing the If header to allow commasClarified presence of Depth header on LOCK refresh requests.Added text to "COPY and the Overwrite Header" section to resolve
issue OVERWRITE_DELETE_ALL_TOO_STRONG.
Added text to "HTTP URL Namespace Model" section to provide more clarification
and examples on what consistency means and what is not required, to resolve
issue CONSISTENCY.Resolve DEFINE_PRINCIPAL by importing definition of principal from RFC3744.Resolve INTEROP_DELETE_AND_MULTISTATUS by adding appendix 3 discussing
backward-compatibility concerns.Resolve DATE_FORMAT_GETLASTMODIFIED by allowing only rfc1123-date, not HTTP-date
for getlastmodified.Resolve COPY_INTO_YOURSELF_CLARIFY by adding sentence to first para. of COPY
section.Confirm that WHEN_TO_MULTISTATUS_FOR_DELETE_1 and WHEN_TO_MULTISTATUS_FOR_DELETE_2
are resolved and tweak language in DELETE section slightly to be clearly consistent.More text clarifications to deal with several of the issues in LOCK_ISSUES.
This may not completely resolve that set but we need feedback from the originator
of the issues at this point.Resolved COPY_INTO_YOURSELF_CLARIFY with new sentence in Copy For Collections
section.Double checked that LEVEL_OR_CLASS is resolved by using class, not level.Further work to resolve IF_AND_AUTH and LOCK_SEMANTICS, clarifying text
on using locks and being authenticated.Added notes on use of 503 status response to resolve issue PROPFIND_INFINITYRemoved section on other uses of Metadata (and associated references)Added reference to RFC4122 for lock tokens and removed section on generating
UUIDsExplained that even with language variation, a property has only one value
(section 4.5).Added section on lock owner (7.1) and what to do if lock requested by
unauthenticated userRemoved section 4.2 -- justification on why to have metadata, not needed nowRemoved paragraph in section 5.2 about collections with resource type
"DAV:collection" but which are non-WebDAV compliant -- not implemented.Added security considerations section on scripts and cookie sessions,
suggested by Barry LindClarified which error codes are defined and undefined in MultiStatusMoved opaquelocktoken definition to an appendix and refer to RFC4122 for use of
'urn:uuid:' URI scheme; fix all lock token examples to use this.Multi-status responses contain URLs which MUST either be absolute (and begin
with the Request-URI or MUST be relative with new limitations. (bug 12)Moved status code sections before example sections within PROPFIND section
for section ordering consistency.Clarified use of Location header with Multi-StatusBugzilla issue resolutions: bugs 9, 12, 14, 19, 20, 29, 30, 34, 36, 102 and 172.Bugzilla editorial issues: bugs 30, 57, 63, 68, 88, 89, 168, 180, 182, 185, 187.More clarity between URL namespaces and XML namespaces, particularly at the beginning
of paragraphs using the word namespace More consistency in referring to properties with the namespace, as in "DAV:lockdiscovery",
and referring to XML element names in single quotes, e.g. 'allprop' element.Figure (example) formatting fixesBugzilla issues: bugs 24, 37, 39, 43, 45, 27, 25Replaced references to "non-null state" of resources with more clear language about
URLs that are mapped to resources, bug 25. Also added definition of URL/URI mapping. Bug 40.Bugzilla issues: bug 7, 8, 9, 41, 47, 51, 62, 93, 171, 172. Bugs 28 and 94 were iterated on.Bugzilla issues: 56, 59, 79, 99, 103, 175, 178. Part of bug 23. Iteration on bug 10.Iteration on bugs 10, 46 and 47. Bug 11.Remove "102 Processing" responseFix bug 46, 105, 107, 120, 140 and 201.Another stab at bug 12 - relative v. absolute URLs in Multi-Status response hrefsFix bug 6, 11, 15, 16, 28, 32, 42, 51, 52, 53, 58, 60, 62, 186, 189, 191, 199, 200Fix bug 96