WEBDAV Working Group Y.Y. Goland, Microsoft
INTERNET DRAFT E.J. Whitehead, Jr., UC Irvine
<draft-ietf-webdav-protocol-06> A. Faizi, Netscape
S.R. Carter, Novell
D. Jensen, Novell
Expires July, 1998 January 18, 1998
Extensions for Distributed Authoring on the World Wide Web -- WEBDAV
Status of this Memo
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Distribution of this document is unlimited. Please send comments to
the Distributed Authoring and Versioning (WEBDAV) working group at
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Discussions of the WEBDAV working group are archived at
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Abstract
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).
Changes
Changes since draft-ietf-webdav-protocol-06.txt
[Editor's note: This section will not appear in the final form of
this document. Its purpose is to provide a concise list of changes
from the previous revision of the draft for use by reviewers.]
Rationale for many of the changes made in this revision of the draft
can be found in the mailing list archives at:
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http://lists.w3.org/Archives/Public/w3c-dist-auth/1997OctDec/0160.ht
ml.
Where the 200 OK status code was used to indicate a successful
response without a response entity body, 204 No Content is now used.
Because PEP uses 420 and 421 status codes, and since PEP has been
submitted as an Experimental RFC, the WebDAV 420 status code has
been changed to 422, and the WebDAV 421 status code has been changed
to 423.
The 423 Destination Locked status code has been changed to 423
Locked, and now covers all cases where an operand was locked,
preventing the execution of the method.
Removed the Destroy header, since it is not needed in this draft,
but will be needed in the versioning draft.
The Enforce-Live-Properties header was renamed to Property-Behavior,
to more closely represent the meaning of the header now that the
"omit" functionality is included. A keepalive field was added to the
Property-Behavior header to make it more meaningful.
Removed the INDEX method, since the functionality of INDEX can now
be performed by the PROPFIND method. PROPFIND provides more
flexibility in specifying the type and amount of property
information returned than does INDEX, which is important for
returning information on a large number of resources.
Clarified that performing a MOVE as a COPY, then DELETE, performed
atomically, only applies to non-collection resources.
Clarified the semantics of errors that are encountered in infinite
depth move and copy of a hierarchy of resources. For errors copying
internal nodes of the hierarchy tree (i.e., collections), the
operation skips that subtree, and moves on to the next subtree. If
an error is encountered moving/copying a leaf of the tree, then skip
that resource, and move on to the next leaf.
Removed the PATCH method. This will be resubmitted as the document
draft-ietf-webdav-patch-00.
Added language that states that if a PROPPATCH is invoked on a null
resource (e.g., a deleted resource), an empty resource is created,
and the PROPPATCH directives are performed on this new resource.
Added a forward reference to the source link definition (Section
13.11) in Section 4.4.
Changed all Values= to Values:. Also changed all "values" to
"value".
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References to state tokens are now restricted to sections 9.7 and
9.8.
The property-behavior header has been turned into the
propertybehavior XML element because it contained a list of URIs
which can thus have unbounded size. The lock-info header has been
turned into the lockinfo XML element for the same reason. I have
also made the same change of the Propfind header into the Propfind
XML element. We can put the property behavior header into the body
because neither COPY nor MOVE have bodies. However we can't put
lock-token, if-state-match, etc. in the body because they may need
to be used with PUT. However I don't consider this a big deal
because I sincerely doubt that there will be cases where lock-token
or if-state-match will see large numbers of entries.
Also changed omit to mean "copy properties with best effort but
failure is acceptable."
Added the external members property.
Added language to 6.4 making it clear that any new resources created
as the child of a write locked collection is added to the lock.
Made the lock-token response header from a single URL to multiple
URLs. But all the URLs MUST refer to the exact same lock.
<?XML version="1.0"> changed to the correct form: <?xml
version="1.0"?>
Changed the delete rule for collections to read that if a delete in
a collection member fails then it is the ancestors, not the progeny,
who can not be deleted in order to maintain the namespace.
Updated our reference to the XML spec.
Added LOCK and UNLOCK to the list of methods covered by the write
lock. This is necessary so that a lock-token will have to be
submitted in order to make changes, otherwise we defeat the whole
purpose of requiring the lock-token.
Changed the title of section 6.6 from Re-Issuing Write Locks to
Refreshing Write Locks, made it illegal to make the same lock
request twice (you know you are making the same request because you
had to include the lock-token to make it!) and instead made it legal
to submit a LOCK method with no body but with a lock-token header.
I also added a refresh example.
Put in a note that an empty request body for PROPFIND means to
return all names and values of properties on the resources.
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I have added a section on XML processing errors. I know, I know, it
shouldn't be in the standard. I will move it to our compliance draft
as soon as we prepare the first version.
Removed addlocks and replaced with the depth header and the depth
element.
Changed all the as in namespace elements to all lower case.
Moved all XML element declarations to the same section. Removed the
parent description.
Updated the depth section to make it more generic, changed the
wording for how COPY/MOVE are handled with write locks, require that
ALL propfind responses include href, require that if a property is
not found in a propfind then a 404 Not Found must be returned, and
made explicit that PROPFIND responses on resources with internal
members are returned as a flat list with no significance to its
ordering.
Removed reference to efficient update in the introduction since
PATCH is now gone.
Rewrote the write lock and null resource section to deal with the
question of the state of the resource when it is locked and null.
Changed www.ietf.org to www.iana.org.
Changed the response element and added the new propstat element.
With the prohibition that an HREF can only appear once in a
multistatus response we can guarantee linear processing costs.
Added Intellectual Property section, as required by RFC 2026.
Added IANA Considerations section.
Added Authorization headers to LOCK and UNLOCK examples.
Changed lock tokens in examples to use string format of UUID.
Since the latest HTTP revision defines a 418 and 419 status code,
the 418 status code has been changed to 422, 419 to 423, 422 to 424,
and 423 to 425.
Changed implementation of the get* (e.g., getcontentlength)
properties to strength MUST.
Changed definition of XML elements and DAV properties to use XML
element definitions, rather than BNF.
Renumbered all sections
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Contents
STATUS OF THIS MEMO..................................................1
ABSTRACT.............................................................1
CHANGES..............................................................1
Changes since draft-ietf-webdav-protocol-06.txt......................1
CONTENTS.............................................................5
1 INTRODUCTION.......................................................9
2 DATA MODEL FOR RESOURCE PROPERTIES................................10
2.1 The Resource Property Model....................................10
2.2 Existing Metadata Proposals....................................10
2.3 Properties and HTTP Headers....................................11
2.4 Property Values................................................11
2.5 Property Names.................................................12
3 COLLECTIONS OF WEB RESOURCES......................................12
3.1 Collection Resources...........................................12
3.2 Creation and Retrieval of Collection Resources.................13
3.3 HTTP URL Namespace Model.......................................13
3.4 Source Resources and Output Resources..........................14
4 LOCKING...........................................................15
4.1 Exclusive Vs. Shared Locks.....................................15
4.2 Required Support...............................................16
4.3 Lock Tokens....................................................16
4.4 opaquelocktoken Lock Token URI Scheme..........................17
4.5 Lock Capability Discovery......................................17
4.6 Active Lock Discovery..........................................18
5 WRITE LOCK........................................................18
5.1 Methods Restricted by Write Locks..............................18
5.2 Write Locks and Properties.....................................18
5.3 Write Locks and Null Resources.................................18
5.4 Write Locks and Collections....................................19
5.5 Write Locks and COPY/MOVE......................................19
5.6 Refreshing Write Locks.........................................19
5.7 Write Locks and The Lock-Token Request Header..................20
5.7.1 Write Lock Token Example...................................20
6 NOTATIONAL CONVENTIONS............................................21
7 HTTP METHODS FOR DISTRIBUTED AUTHORING............................21
7.1 PROPFIND.......................................................21
7.1.1 Example: Retrieving Named Properties.......................22
7.1.2 Example: Using allprop to Retrieve All Properties..........23
7.1.3 Example: Using propname to Retrieve all Property Names.....26
7.2 PROPPATCH......................................................28
7.2.1 Status Codes...............................................28
7.2.2 Example....................................................28
7.3 MKCOL Method...................................................30
7.3.1 Request....................................................30
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7.3.2 Response Codes.............................................30
7.3.3 Example....................................................31
7.4 ADDREF Method..................................................31
7.4.1 The Request................................................31
7.4.2 Example....................................................31
7.5 DELREF Method..................................................32
7.5.1 The Request................................................32
7.5.2 Example....................................................32
7.6 GET, HEAD for Collections......................................32
7.7 POST for Collections...........................................33
7.8 DELETE.........................................................33
7.8.1 DELETE for Non-Collection Resources........................33
7.8.2 DELETE for Collections.....................................33
7.9 PUT............................................................34
7.9.1 PUT for Non-Collection Resources...........................34
7.9.2 PUT for Collections........................................35
7.10 COPY Method....................................................35
7.10.1 COPY for HTTP/1.1 resources................................35
7.10.2 COPY for Properties........................................35
7.10.3 COPY for Collections.......................................36
7.10.4 Type Interactions..........................................37
7.10.5 Status Codes...............................................37
7.10.6 Overwrite Example..........................................38
7.10.7 No Overwrite Example.......................................38
7.10.8 Collection Example.........................................38
7.11 MOVE Method....................................................39
7.11.1 MOVE for Collections.......................................40
7.11.2 Status Codes...............................................40
7.11.3 Non-Collection Example.....................................41
7.11.4 Collection Example.........................................41
7.12 LOCK Method....................................................42
7.12.1 Operation..................................................43
7.12.2 The Effect of Locks on Properties and Collections..........43
7.12.3 Locking Replicated Resources...............................43
7.12.4 Depth and Locking..........................................43
7.12.5 Interaction with other Methods.............................44
7.12.6 Lock Compatibility Table...................................44
7.12.7 Lock Response..............................................44
7.12.8 Status Codes...............................................44
7.12.9 Example - Simple Lock Request..............................45
7.12.10 Example - Refreshing a Write Lock.........................46
7.12.11 Example - Multi-Resource Lock Request.....................47
7.13 UNLOCK Method..................................................48
7.13.1 Example....................................................48
8 HTTP HEADERS FOR DISTRIBUTED AUTHORING............................49
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8.1 Collection-Member Header.......................................49
8.2 DAV Header.....................................................49
8.3 Depth Header...................................................49
8.4 Destination Header.............................................50
8.5 If-None-State-Match............................................50
8.6 If-State-Match.................................................51
8.7 Lock-Token Request Header......................................51
8.8 Lock-Token Response Header.....................................52
8.9 Overwrite Header...............................................53
8.10 Status-URI Response Header.....................................53
8.11 Timeout Header.................................................53
9 STATUS CODE EXTENSIONS TO HTTP/1.1................................54
9.1 102 Processing.................................................54
9.2 207 Multi-Status...............................................55
9.3 422 Unprocessable Entity.......................................55
9.4 423 Insufficient Space on Resource.............................55
9.5 424 Method Failure.............................................55
9.6 425 Locked.....................................................55
10 MULTI-STATUS RESPONSE...........................................55
11 XML ELEMENT DEFINITIONS.........................................55
11.1 activelock XML Element.........................................56
11.1.1 depth XML Element..........................................56
11.1.2 locktoken XML Element......................................56
11.1.3 timeout XML Element........................................56
11.2 collection XML Element.........................................56
11.3 href XML Element...............................................56
11.4 link XML Element...............................................57
11.4.1 dst XML Element............................................57
11.4.2 src XML Element............................................57
11.5 lockentry XML Element..........................................57
11.6 lockinfo XML Element...........................................57
11.7 lockscope XML Element..........................................58
11.7.1 exclusive XML Element......................................58
11.7.2 shared XML Element.........................................58
11.8 locktype XML Element...........................................58
11.8.1 write XML Element..........................................58
11.9 multistatus XML Element........................................58
11.9.1 response XML Element.......................................59
11.9.2 responsedescription XML Element............................59
11.10 owner XML Element.............................................60
11.11 prop XML element..............................................60
11.12 propertybehavior XML element..................................60
11.12.1 keepalive XML element.....................................60
11.12.2 omit XML element..........................................61
11.13 propertyupdate XML element....................................61
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11.13.1 remove XML element........................................61
11.13.2 set XML element...........................................62
11.14 propfind XML Element..........................................62
11.14.1 allprop XML Element.......................................62
11.14.2 propname XML Element......................................62
12 DAV PROPERTIES..................................................62
12.1 creationdate Property..........................................63
12.2 displayname Property...........................................63
12.3 externalmembers Property.......................................63
12.4 getcontentlanguage Property....................................63
12.5 getcontentlength Property......................................64
12.6 getcontenttype Property........................................64
12.7 getetag Property...............................................64
12.8 getlastmodified Property.......................................64
12.9 lockdiscovery Property.........................................65
12.9.1 Example....................................................65
12.10 resourcetype Property.........................................66
12.11 source Property...............................................66
12.11.1 Example...................................................67
12.12 supportedlock Property........................................67
12.12.1 Example...................................................68
13 DAV COMPLIANCE CLASSES..........................................68
13.1 Class 1........................................................69
13.2 Class 2........................................................69
14 INTERNATIONALIZATION CONSIDERATIONS.............................69
15 SECURITY CONSIDERATIONS.........................................70
15.1 Authentication of Clients......................................71
15.2 Denial of Service..............................................71
15.3 Security through Obscurity.....................................72
15.4 Privacy Issues Connected to Locks..............................72
15.5 Privacy Issues Connected to Properties.........................72
15.6 Reduction of Security due to Source Link.......................72
16 IANA CONSIDERATIONS.............................................73
17 TERMINOLOGY.....................................................73
18 COPYRIGHT.......................................................74
19 INTELLECTUAL PROPERTY...........................................74
20 ACKNOWLEDGEMENTS................................................75
21 REFERENCES......................................................76
22 AUTHORS' ADDRESSES..............................................78
23 APPENDICES......................................................79
23.1 Appendix 1 - WebDAV Document Type Definition...................79
23.2 Appendix 2 - ISO 8601 Date and Time Profile....................80
23.3 Appendix 3 - Notes on Processing XML Elements..................81
23.3.1 XML Syntax Error Example...................................81
23.3.2 Unknown XML Element Example................................81
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1 Introduction
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 related documents, and to
receive a listing of pages at a particular hierarchy level (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 copy and move Web resources
Requirements and rationale for these operations are described in a
companion document, "Requirements for a Distributed Authoring and
Versioning Protocol for the World Wide Web" [Slein et al., 1997].
The sections below provide a detailed introduction to resource
properties (Section 2), collections of resources (Section 3), and
locking operations (Section 4). These sections introduce the
abstractions manipulated by the WebDAV-specific HTTP methods
described in Section 7, "HTTP Methods for Distributed Authoring".
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 Extensible Markup Language (XML) [Bray,
Paoli, Sperberg-McQueen, 1998] 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.
As a rule of thumb, parameters are encoded in XML entity bodies when
they have unbounded length, or when they may be shown to a human
user and hence require encoding in an ISO 10646 character set.
Otherwise, parameters are encoded within HTTP headers. Section 8
describes the new HTTP headers used with WebDAV methods.
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
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input. XML elements used in this specification are defined in
Section 11.
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. New status codes developed for the WebDAV methods are
defined in Section 9. Since some WebDAV methods may operate over
many resources, the Multi-Status status type has been introduced to
return status information for multiple resources. Multi-Status
response is described in Section 10.
WebDAV employs the property mechanism to store information about the
current state of the resource. For example, when a lock is taken
out on a resource, a lock information property describes the current
state of the lock. Section 12 defines the properties used within the
WebDAV specification.
Finishing off the specification are sections on what it means to be
compliant with this specification (Section 13), on
internationalization support (Section 14), and on security (Section
15).
2 Data Model for Resource Properties
2.1 The Resource Property Model
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 that 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. A dead property has its syntax and semantics
enforced by the client; the server merely records the value of the
property verbatim.
2.2 Existing Metadata Proposals
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Properties have long played an essential role in the maintenance of
large document repositories, and many current proposals contain some
notion of a property, or discuss web metadata more generally. These
include PICS [Miller et al., 1996], PICS-NG, XML [Bray, Paoli,
Sperberg-McQueen, 1998], Web Collections, and several proposals on
representing relationships within HTML. Work on PICS-NG and Web
Collections has been subsumed by the Resource Definition Framework
(RDF) metadata activity of the World Wide Web Consortium. RDF
consists of a network-based data model and an XML representation of
that model.
Some proposals come from a digital library perspective. These
include the Dublin Core [Weibel et al., 1995] metadata set and the
Warwick Framework [Lagoze, 1996], a container architecture for
different metadata schemas. The literature includes many examples
of metadata, including MARC [MARC, 1994], a bibliographic metadata
format, and RFC 1807 [Lasher, Cohen, 1995], a technical report
bibliographic format employed by the Dienst system. Additionally,
the proceedings from the first IEEE Metadata conference describe
many community-specific metadata sets.
Participants of the 1996 Metadata II Workshop in Warwick, UK
[Lagoze, 1996], noted that "new metadata sets will develop as the
networked infrastructure matures" and "different communities will
propose, design, and be responsible for different types of
metadata." These observations can be corroborated by noting that
many community-specific sets of metadata already exist, and there is
significant motivation for the development of new forms of metadata
as many communities increasingly make their data available in
digital form, requiring a metadata format to assist data location
and cataloging.
2.3 Properties and HTTP Headers
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.
2.4 Property Values
The value of a property is expressed as a well-formed XML document.
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
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in the original schema and will ignore elements they do not
understand. XML's support for multiple character sets allows any
human-readable property to be encoded and read in a character set
familiar to the user.
2.5 Property Names
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, so long as that property is "live" on the resources in
question.
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.
3 Collections of Web Resources
This section provides a description of a new type of Web resource,
the collection, and discusses its interactions with the HTTP Uniform
Resource Locator (URL) namespace. The purpose of a collection
resource is to model collection-like objects (e.g., filesystem
directories) within a server's namespace.
All DAV compliant resources MUST support the HTTP URL namespace
model specified herein.
3.1 Collection Resources
A collection is a resource whose state consists of an unordered list
of internal members, an unordered list of external members, and a
set of properties. An internal member resource MUST have a URI that
is immediately relative to the base URI of the collection. That is,
the internal member's URI is equal to the parent collection's URI
plus an additional segment where segment is defined in Section 3.2.1
of RFC 2068 [Fielding et al., 1996].
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An external member resource is a resource that could not be an
internal member resource. Any given internal or external Member MUST
only belong to the collection once, i.e., it is illegal to have
multiple instances of the same URI in a collection. Properties
defined on collections behave exactly as do properties on non-
collection resources.
There is a standing convention that when a collection is referred to
by its name without a trailing slash, the trailing slash is
automatically appended. Due to this, a resource MAY accept a URI
without a trailing "/" to point to a collection. In this case it
SHOULD return a location header in the response pointing to the URL
ending with the "/". For example, if a client invokes a method on
http://foo.bar/blah (no trailing slash), the resource
http://foo.bar/blah/ (trailing slash) MAY respond as if the
operation were invoked on it, and SHOULD return a location header
with http://foo.bar/blah/ in it. In general clients SHOULD use the
"/" form of collection names.
3.2 Creation and Retrieval of Collection Resources
This document specifies the MKCOL method to create new collection
resources, rather than using the existing HTTP/1.1 PUT or POST
method, for the following reasons
In HTTP/1.1, the PUT method is defined to store the request body at
the location specified by the Request-URI. While a description
format for a collection can readily be constructed for use with PUT,
the implications of sending such a description to the server are
undesirable. For example, if a description of a collection that
omitted some existing resources were PUT to a server, this might be
interpreted as a command to remove those members. This would extend
PUT to perform DELETE functionality, which is undesirable since it
changes the semantics of PUT, and makes it difficult to control
DELETE functionality with an access control scheme based on methods.
While the POST method is sufficiently open-ended that a "create a
collection" POST command could be constructed, this is undesirable
because it would be difficult to separate access control for
collection creation from other uses of POST.
The exact definition of the behavior of GET and PUT on collections
is defined later in this document.
3.3 HTTP URL Namespace Model
The HTTP URL Namespace is a hierarchical namespace where the
hierarchy is delimited with the "/" character. DAV compliant
resources MUST maintain the consistency of the HTTP URL namespace.
Any attempt to create a resource (excepting the root member of a
namespace) that would not be the internal member of a collection
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MUST fail. For example, if the collection http://www.foo.bar.org/a/
exists, but http://www.foo.bar.org/a/b/does not exist, an attempt to
create http://www.foo.bar.org/a/b/c must fail.
3.4 Source Resources and Output Resources
For many resources, the entity returned by a GET method exactly
matches the persistent state of the resource, for example, a GIF
file stored on a disk. For this simple case, the URL at which a
resource is accessed is identical to the URL at which the source
(the persistent state) of the resource is accessed. This is also
the case for HTML source files that are not processed by the server
prior to transmission.
However, the server can sometimes process HTML resources before they
are transmitted as a return entity body. For example, server-side-
include directives within an HTML file instruct a server to replace
the directive with another value, such as the current date. In this
case, what is returned by GET (HTML plus date) differs from the
persistent state of the resource (HTML plus directive). Typically
there is no way to access the HTML resource containing the
unprocessed directive.
Sometimes the entity returned by GET is the output of a data-
producing process that is described by one or more source resources
(that may not even have a location in the URL namespace). A single
data-producing process may dynamically generate the state of a
potentially large number of output resources. An example of this is
a CGI script that describes a "finger" gateway process that maps
part of the namespace of a server into finger requests, such as
http://www.foo.bar.org/finger_gateway/user@host.
In the absence of distributed authoring capabilities, it is
acceptable to have no mapping of source resource(s) to the URI
namespace. In fact, preventing access to the source resource(s) has
desirable security benefits. However, if remote editing of the
source resource(s) is desired, the source resource(s) should be
given a location in the URI namespace. This source location should
not be one of the locations at which the generated output is
retrievable, since in general it is impossible for the server to
differentiate requests for source resources from requests for
process output resources. There is often a many-to-many
relationship between source resources and output resources.
On WebDAV compliant servers, for all output resources which have a
single source resource (and that source resource has a URI), the URI
of the source resource SHOULD be stored in a link on the output
resource with type http://www.iana.org/standards/dav/source (see
Section 12.11 for a description of the source link). Note that by
storing the source URIs in links on the output resources, the burden
of discovering the source is placed on the authoring client.
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4 Locking
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.
4.1 Exclusive Vs. Shared Locks
The most basic form of lock is an exclusive lock. This is a lock
where the access right in question is only granted to a single
principal. The need for this arbitration results from a desire to
avoid having to constantly merge results.
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 right. Shared locks are provided for this case. A
shared lock allows multiple principals to receive a lock. Hence any
principal with appropriate access can get 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 the
resource. Those who are not, don't. Among those who have access
permission to write 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
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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 write locks are often
too rigid. An exclusive write lock is used to enforce a particular
editing process: take out exclusive write 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.
Despite their potential problems, exclusive write locks are
extremely useful, since often a guarantee of freedom from overwrite
conflicts is what is needed. This specification provides both
exclusive write locks and the less strict mechanism of shared locks.
4.2 Required Support
A WebDAV compliant server is not required to support locking in any
form. If the server 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.
4.3 Lock Tokens
A lock token is a URI that identifies a particular lock. A lock
token is returned by every successful LOCK operation in the Lock-
Token response header, and can also be discovered through lock
discovery on a resource.
Lock token URIs are required to be unique across all resources for
all time. This uniqueness constraint allows lock tokens to be
submitted across resources and servers without fear of confusion.
This specification provides a lock token URI scheme called
opaquelocktoken that meets the uniqueness requirements. However
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resources are free to return any URI scheme so long as it meets the
uniqueness requirements.
4.4 opaquelocktoken Lock Token URI Scheme
The opaquelocktoken URI scheme is designed to be unique across all
resources for all time. Due to this uniqueness quality, a client
MAY submit an opaque lock token in a Lock-Token request header and
an If-[None]-State-Match header on a resource other than the one
that returned it.
All resources MUST recognize the opaquelocktoken scheme and, at
minimum, recognize that the lock token was not generated by the
resource. Note, however, that resources are not required to
generate opaquelocktokens in LOCK method responses.
In order to guarantee uniqueness across all resources for all time
the opaquelocktoken requires the use of the Universally Unique
Identifier (UUID, also known as a Globally Unique Identifier, or
GUID) mechanism, as described in [Leach, Salz, 1998].
Opaquelocktoken generators, however, have a choice of how they
create these tokens. They can either generate a new UUID for every
lock token they create, which is potentially very expensive, or they
can create a single UUID and then add extension characters. If the
second method is selected then the program generating the extensions
MUST guarantee that the same extension will never be used twice with
the associated UUID.
OpaqueLockToken-URI = "opaquelocktoken:" UUID [Extension] ; The
UUID production is the string form of a UUID, as defined in [Leach,
Salz, 1998]. Note that white space (LWS) is not allowed between
elements of this production.
Extension = path ; path is defined in Section 3.2.1 of RFC 2068
[Fielding et al., 1996]
4.5 Lock Capability Discovery
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. Lock capability discovery differs from discovery of
supported access control types, since there may be access control
types without corresponding lock types. A client can determine what
lock types the server supports by retrieving the supportedlock
property.
Any DAV compliant resource that supports the LOCK method MUST
support the supportedlock property.
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4.6 Active Lock Discovery
If another principal locks a resource that a principal wishes to
access, it is useful for the second principal to be able to find out
who the first principal is. For this purpose the lockdiscovery
property is provided. This property lists all outstanding locks,
describes their type, and provides their lock token.
Any DAV compliant resource that supports the LOCK method MUST
support the lockdiscovery property.
5 Write Lock
This section describes the semantics specific to the write access
type for locks. The write lock is a specific instance of a lock
type, and is the only lock type described in this specification. A
DAV compliant resource MAY support the write lock.
5.1 Methods Restricted by Write Locks
A write lock prevents a principal without the lock from successfully
executing a PUT, POST, PROPPATCH, LOCK, UNLOCK, MOVE, DELETE, MKCOL,
ADDREF or DELREF on the locked resource. All other current methods,
GET in particular, function independent of the lock.
Note, however, that as new methods are created it will be necessary
to specify how they interact with a write lock.
5.2 Write Locks and Properties
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.
5.3 Write Locks and Null Resources
It is possible to assert a write lock on a null resource in order to
lock the name. A write locked null resource acts in all ways as a
null resource other than it MUST respond to a PROPFIND request and
MUST support the lockdiscovery and supportedlock properties.
Until a method such as PUT or MKCOL is executed, the resource stays
in the null state with the exception of the behavior stated above.
If the resource is unlocked without a PUT, MKCOL, or similar method
having been executed, the resource is no longer required to support
the PROPFIND method or the lockdiscovery and supportedlock
properties.
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5.4 Write Locks and Collections
A write lock on a collection prevents the addition or removal of
members of the collection by non-lock owners. As a consequence,
when a principal issues a request to create a new internal member of
a write locked collection using PUT or POST, or to remove an
existing internal member of a write locked collection using DELETE,
this request MUST fail if the principal does not have a write lock
on the collection.
However, if a write lock request is issued to a collection
containing internal member resources that are currently locked in a
manner which conflicts with the write lock, the request MUST fail
with a 425 Locked status code.
If a lock owner causes a resource to be added as an internal member
of a locked collection then the new resource is 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
/a/b/c will be added to the write lock.
5.5 Write Locks and COPY/MOVE
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 depth locked then the resource
will be added to the lock.
A MOVE does not move the write lock with the resource. There are two
exceptions to this rule. First, as noted in section 5.4, if the MOVE
makes the resource a child of a collection that is depth locked then
the resource will be under the same lock. Second, if a depth locked
resource is moved to a destination that is within the scope of the
same depth lock (e.g., within the namespace tree covered by the
lock), the moved resource is still a member of the lock. In both
cases a Lock-Token header MUST be submitted containing a lock token
for the lock on the source, if locked, and on the destination.
5.6 Refreshing Write Locks
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 header in order to
make the request for a resource that is already locked.
However, a client MAY submit a LOCK method with a Lock-Token header
but without a body. This form of LOCK MAY only be used to "refresh"
a lock. Currently, refreshing a lock only means that any timers
associated with the lock are re-set.
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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.
If an error is received in response to a refresh LOCK request the
client MUST assume that the lock was not refreshed.
5.7 Write Locks and The Lock-Token Request Header
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 the Lock-Token request header,
defined in Section 8.7, is introduced.
5.7.1 Write Lock Token Example
>>Request
COPY /~fielding/index.html HTTP/1.1
Host: www.ics.uci.edu
Destination: http://www.ics.uci.edu/users/f/fielding/index.html
Lock-Token: <opaquelocktoken:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>
Authorization: Digest username="fielding",
realm="fielding@ics.uci.edu", nonce="...",
uri="/~fielding/index.html", response="...",
opaque="..."
>>Response
HTTP/1.1 204 No Content
In this example, even though both the source and destination are
locked, only one lock token must be submitted, for the lock on the
destination. This is due to the source resource not being modified
during a COPY, and hence unaffected by the write lock. The
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Authorization header provides the Digest authentication credentials
for the principal making the request (note that the nonce, response,
and opaque fields have not been calculated for this example). The
source and the destination resources are both located within the
same authentication realm, therefore only one set of Authorization
credentials needs to be submitted.
6 Notational Conventions
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
[Fielding et al., 1997]. Since this augmented BNF uses the basic
production rules provided in Section 2.2 of [Fielding et al., 1997],
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 RFC 2119 [Bradner,
1997].
7 HTTP Methods for Distributed Authoring
7.1 PROPFIND
The PROPFIND method retrieves properties defined on the Request-URI,
if the resource does not have any internal members, or on the
Request-URI and potentially its member resources, if the resource
does have internal members. All DAV compliant resources MUST
support the PROPFIND method.
A client MAY submit a Depth header with a value of "0", "1", or
"infinity" with a PROPFIND on a resource with internal members. DAV
compliant servers MUST support the "0", "1" and "infinity"
behaviors. 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, all property
values, or a list of the names of the resource's properties. A
client MAY choose not to submit a request body. An empty request
body MUST be treated as a request for the names and values of all
properties.
The response is a text/xml message body that contains a multistatus
XML element that describes the results of the attempts to retrieve
the various properties. If a property was successfully retrieved
then its value MUST be returned in a prop XML element.
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If there is an error retrieving a property then a proper error
result must be included. Requests to retrieve the value of a
property which does not exist is an error and MUST be noted with a
response XML element which contains a 404 Not Found status value.
Consequently, the multistatus XML element for a resource with
members MUST include a response XML element for each member of the
resource, to whatever depth was requested. Each response XML element
MUST contain an href XML element that identifies the resource on
which the properties in the prop XML element are defined. Results
for a PROPFIND on a resource with internal members are returned as a
flat list whose order of entries is not significant.
In the case of allprop and propname, if a principal does not have
the right to know if a particular property exists then a 404 Not
Found MUST be returned.
The results of this method SHOULD NOT be cached.
7.1.1 Example: Retrieving Named Properties
>>Request
PROPFIND /files/ HTTP/1.1
Host: www.foo.bar
Depth: 0
Content-type: text/xml
Content-Length: xyz
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<D:propfind>
<D:href>http://www.foo.bar/boxschema/bigbox</D:href>
<D:href>http://www.foo.bar/boxschema/author</D:href>
<D:href>http://www.foo.bar/boxschema/DingALing</D:href>
<D:href>http://www.foo.bar/boxschema/Random</D:href>
</D:propfind>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<?namespace href="http://www.foo.bar/boxschema" as="R"?>
<D:multistatus>
<D:response>
<D:href>http://www.foo.bar/files/</D:href>
<D:propstat>
<D:prop>
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<R:bigbox>
<R:BoxType>Box type A</R:BoxType>
</R:bigbox>
<R:author>
<R:Name>J.J. Johnson</R:Name>
</R:author>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop><R:DingALing/><R:Random/></D:prop>
<D:status>HTTP/1.1 403 Forbidden</D:status>
<D:responsedescription> The user does not have access to
the DingALing property.
</D:responsedescription>
</D:propstat>
</D:response>
<D:responsedescription> There has been an access violation error.
</D:responsedescription>
</D:multistatus>
In this example, PROPFIND is executed on the collection
http://www.foo.bar/files/. The specified depth is zero, hence the
PROPFIND applies only to the collection itself, and not to any of
its members. 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.
7.1.2 Example: Using allprop to Retrieve All Properties
>>Request
PROPFIND /container/ HTTP/1.1
Host: www.foo.bar
Depth: 1
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<D:propfind>
<D:allprop/>
</D:propfind>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxxx
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<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="S"?>
<?namespace href="http://www.foo.bar/boxschema/" as="R"?>
<S:multistatus>
<S:response>
<S:href>http://www.foo.bar/container/</S:href>
<S:propstat>
<S:prop>
<R:bigbox>
<R:BoxType>Box type A</R:BoxType>
</R:bigbox>
<R:author>
<R:Name>Hadrian</R:Name>
</R:author>
<S:creationdate>
1997-12-01T17:42:21-08:00
</S:creationdate>
<S:displayname>
Example collection
</S:displayname>
<S:externalmembers>
<S:href>http://www.acme.com/front/</S:href>
</S:externalmembers>
<S:resourcetype><S:collection/></S:resourcetype>
<S:supportedlock>
<S:lockentry>
<S:exclusive/><S:write/>
</S:lockentry>
<S:lockentry>
<S:shared/><S:write/>
</S:lockentry>
</S:supportedlock>
</S:prop>
<S:status>HTTP 1.1 200 OK</S:status>
</S:propstat>
</S:response>
<S:response>
<S:href>http://www.foo.bar/container/front.html</S:href>
<S:propstat>
<S:prop>
<R:bigbox>
<R:BoxType>Box type B</R:BoxType>
</R:bigbox>
<S:creationdate>
1997-12-01T18:27:21-08:00
</S:creationdate>
<S:displayname>
Example HTML resource
</S:displayname>
<S:getcontentlength>
4525
</S:getcontentlength>
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<S:getcontenttype>
text/html
</S:getcontenttype>
<S:getetag>
zzyzx
</S:getetag>
<S:getlastmodified>
Monday, 12-Jan-98 09:25:56 GMT
</S:getlastmodified>
<S:resourcetype/>
<S:supportedlock>
<S:lockentry>
<S:exclusive/><S:write/>
</S:lockentry>
<S:lockentry>
<S:shared/><S:write/>
</S:lockentry>
</S:supportedlock>
</S:prop>
<S:status>HTTP 1.1 200 OK</S:status>
</S:propstat>
</S:response>
</S:multistatus>
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 properties defined on each
resource.
The resource http://www.foo.bar/container/ has seven properties
defined on it, named http://www.foo.bar/boxschema/bigbox,
http://www.foo.bar/boxschema/author,
http://www.iana.org/standards/dav/creationdate,
http://www.iana.org/standards/dav/displayname,
http://www.iana.org/standards/dav/externalmembers,
http://www.iana.org/standards/dav/resourcetype, and
http://www.iana.org/standards/dav/supportedlock. The last five
properties are WebDAV-specific, defined in Section 12. Since GET is
not supported on this resource, the get-* properties (e.g., get-
content-length) are not defined on this resource. The DAV-specific
properties assert that "container" was created on December 1, 1997,
at 5:42:21PM, in a time zone 8 hours west of GMT (creationdate), has
a name of "Example collection" (displayname), a single external
member resource, http://www.acme.com/front/ (externalmembers), a
collection resource type (resourcetype), and supports exclusive
write and shared write locks (supportedlock).
The resource http://www.foo.bar/container/front.html has nine
properties defined on it, named http://www.foo.bar/boxschema/bigbox
(another instance of the "bigbox" property type),
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http://www.iana.org/standards/dav/creationdate,
http://www.iana.org/standards/dav/displayname,
http://www.iana.org/standards/dav/getcontentlength,
http://www.iana.org/standards/dav/getcontenttype,
http://www.iana.org/standards/dav/getetag,
http://www.iana.org/standards/dav/getlastmodified,
http://www.iana.org/standards/dav/resourcetype, and
http://www.iana.org/standards/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 (creationdate), has
a name of "Example HTML resource" (displayname), a content length of
4525 (getcontentlength), a MIME type of "text/html"
(getcontenttype), an entity tag of "zzyzx" (getetag), was last
modified on Monday, January 12, 1998, at 09:25:56 GMT
(getlastmodified), has an undefined resource type, meaning that it
is not a collection (resourcetype), and supports both exclusive
write and shared write locks (supportedlock).
7.1.3 Example: Using propname to Retrieve all Property Names
>>Request
PROPFIND /container/ HTTP/1.1
Host: www.foo.bar
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<D:propfind>
<D:propname/>
</D:propfind>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxx
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="D"?>
<?namespace href="http://www.foo.bar/boxschema/" as="R"?>
<D:multistatus>
<D:response>
<D:href>http://www.foo.bar/container/</D:href>
<D:propstat>
<D:prop>
<R:bigbox/>
<R:author/>
<D:creationdate/>
<D:displayname/>
<D:externalmembers/>
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<D:resourcetype/>
<D:supportedlock/>
</D:prop>
<D:status>HTTP 1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://www.foo.bar/container/front.html</D:href>
<D:propstat>
<D:prop>
<R:bigbox/>
<D:creationdate/>
<D:displayname/>
<D:get-content-length/>
<D:get-content-type/>
<D:get-etag/>
<D:get-last-modified/>
<D:resourcetype/>
<D:supportedlock/>
</D:prop>
<D:status>HTTP 1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
In this example, PROPFIND is invoked on the collection resource
http://www.foo.bar/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 progeny should be returned.
Consistent with the previous example, resource
http://www.foo.bar/container/ has seven properties defined on it,
http://www.foo.bar/boxschema/bigbox, and
http://www.foo.bar/boxschema/author,
http://www.iana.org/standards/dav/creationdate,
http://www.iana.org/standards/dav/displayname,
http://www.iana.org/standards/dav/externalmembers,
http://www.iana.org/standards/dav/resourcetype, and
http://www.iana.org/standards/dav/supportedlock. The resource
http://www.foo.bar/container/index.html, a member of the "container"
collection, has nine properties defined on it,
http://www.foo.bar/boxschema/bigbox,
http://www.iana.org/standards/dav/creationdate,
http://www.iana.org/standards/dav/displayname,
http://www.iana.org/standards/dav/get-content-length,
http://www.iana.org/standards/dav/get-content-type,
http://www.iana.org/standards/dav/get-etag,
http://www.iana.org/standards/dav/get-last-modified,
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http://www.iana.org/standards/dav/resourcetype, and
http://www.iana.org/standards/dav/supportedlock.
7.2 PROPPATCH
The PROPPATCH method processes instructions specified in the request
body to set and/or remove properties defined on the resource
identified by 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 of the DAV schema.
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 at least
one propertyupdate XML element. Instruction processing MUST occur in
the order instructions are received (i.e., from top to bottom).
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 Section 11.13.
If PROPPATCH is invoked on a null resource (e.g., a deleted
resource), an empty resource is created, and the PROPPATCH
directives are performed on this new resource.
7.2.1 Status Codes
200 OK - The command succeeded. As there can be a mixture of sets
and removes in a body, a 201 Created seems inappropriate.
403 Forbidden - The client, for reasons the server chooses not to
specify, cannot alter one of the properties.
409 Conflict - The client has provided a value whose semantics are
not appropriate for the property. This includes trying to set read-
only properties.
413 Request Entity Too Long - If a particular property is too long
to be recorded then a composite XML error will be returned
indicating the offending property.
7.2.2 Example
>>Request
PROPPATCH /bar.html HTTP/1.1
Host: www.foo.com
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Content-Type: text/xml
Content-Length: xxxx
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="D"?>
<?namespace href="http://www.w3.com/standards/z39.50/" as="Z"?>
<D:propertyupdate>
<D:set>
<D:prop>
<Z:authors>
<Z:Author>Jim Whitehead</Z:Author>
<Z:Author>Roy Fielding</Z:Author>
</Z:authors>
</D:prop>
</D:set>
<D:remove>
<D:prop><Z:Copyright-Owner/></D:prop>
</D:remove>
</D:propertyupdate>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="D"?>
<?namespace href="http://www.w3.com/standards/z39.50/" as="Z"?>
<D:multistatus>
<D:response>
<D:href>http://www.foo.com/bar</D:href>
<D:propstat>
<D:prop><Z:Authors/></D:prop>
<D:status>HTTP/1.1 424 Method Failure</D:status>
</D:propstat>
<D:propstat>
<D:prop><Z:Copyright-Owner/></D:prop>
<D:status>HTTP/1.1 409 Conflict</D:status>
</D:propstat>
<D:responsedescription> Copyright Owner can not be deleted or
altered.</D:responsedescription>
<D:response>
</D:multistatus>
In this example, the client requests the server to set the value of
the http://www.w3.com/standards/z39.50/Authors property, and to
remove the property http://www.w3.com/standards/z39.50/Copyright-
Owner. Since the Copyright-Owner property could not be removed, no
property modifications occur. The Method Failure status code for
the Authors property indicates this action would have succeeded if
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it were not for the conflict with removing the Copyright-Owner
property.
7.3 MKCOL Method
The MKCOL method is used to create a new collection. All DAV
compliant resources MUST support the MKCOL method.
7.3.1 Request
MKCOL creates a new collection resource at the location specified by
the Request-URI. If the resource identified by the Request-URI is
non-null then the MKCOL must fail. During MKCOL processing, a
server MUST make the Request-URI a member of its parent collection.
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 neither /a/b/ nor /a/b/c/ exists, the request MUST fail.
When MKCOL is invoked without a request body, the newly created
collection has no members.
A MKCOL request message MAY contain a message body. The behavior of
a MKCOL request when the body is present is 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. The exact
behavior of MKCOL for various request media types is undefined in
this document, and will be specified in separate documents.
7.3.2 Response Codes
Responses from a MKCOL request are not cacheable, since MKCOL has
non-idempotent semantics.
201 Created - The collection or structured resource was created in
its entirety.
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 namespace, and 2) The parent collection of the
Request-URI exists but cannot accept members.
405 Method Not Allowed - MKCOL can only be executed on a
deleted/non-existent resource.
409 Conflict - A collection cannot be made at the Request-URI until
one or more intermediate collections have been created.
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415 Unsupported Media Type- The server does not support the request
type of the body.
423 Insufficient Space on Resource - The resource does not have
sufficient space to record the state of the resource after the
execution of this method.
7.3.3 Example
This example creates a collection called /webdisc/xfiles/ on the
server www.server.org.
>>Request
MKCOL /webdisc/xfiles/ HTTP/1.1
Host: www.server.org
>>Response
HTTP/1.1 201 Created
7.4 ADDREF Method
The ADDREF method is used to add external members to a resource.
All DAV compliant collection resources MUST support the ADDREF
method. All other DAV compliant resources MAY support the ADDREF
method as appropriate.
7.4.1 The Request
The ADDREF method adds the URI specified in the Collection-Member
header as an external member to the collection specified by the
Request-URI.
It is not an error if the URI specified in the Collection-Member
header already exists as an external member of the collection.
However, after processing the ADDREF there MUST be only one instance
of the URI in the collection. If the URI specified in the
Collection-Member header already exists as an internal member of the
collection, the ADDREF method MUST fail with a 412 Precondition
Failed status code.
More than one Collection-Member request header MUST NOT be used with
the ADDREF method.
7.4.2 Example
>>Request
ADDREF /~ejw/dav/ HTTP/1.1
Host: www.ics.uci.edu
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Collection-Member: http://www.iana.org/standards/dav/
>>Response
HTTP/1.1 204 No Content
This example adds the URI http://www.iana.org/standards/dav/ as an
external member resource of the collection
http://www.ics.uci.edu/~ejw/dav/.
7.5 DELREF Method
The DELREF method is used to remove external members from a
resource. All DAV compliant collection resources MUST support the
DELREF method. All other DAV compliant resources MUST support the
DELREF method only if they support the ADDREF method.
7.5.1 The Request
The DELREF method removes the URI specified in the Collection-Member
header from the collection specified by the Request-URI.
DELREFing a URI which is not a member of the collection is not an
error. DELREFing an internal member MUST fail with a 412
Precondition Failed status code.
More than one Collection-Member request header MUST NOT be used with
the DELREF method.
7.5.2 Example
>>Request
DELREF /~ejw/dav/ HTTP/1.1
Host: www.ics.udi.edu
Collection-Member: http://www.iana.org/standards/dav/
>>Response
HTTP/1.1 204 No Content
This example removes the URI http://www.iana.org/standards/dav/, an
external member resource, from the collection
http://www.ics.uci.edu/~ejw/dav/.
7.6 GET, HEAD for Collections
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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" [Fielding et al.,
1997]. 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 state 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.
7.7 POST for Collections
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.
7.8 DELETE
7.8.1 DELETE for Non-Collection Resources
If the DELETE method is issued to a non-collection resource which is
an internal member of a collection, then during DELETE processing a
server MUST remove the Request-URI from its parent collection. A
server MAY remove the URI of a deleted resource from any collections
of which the resource is an external member.
7.8.2 DELETE for Collections
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 on a
DELETE on a collection with any value but infinity.
DELETE instructs that the collection specified in the request-URI,
the records of its external member resources, and all its internal
member resources, are to be deleted.
If any member cannot be deleted then all of the member's ancestors
MUST NOT be deleted, so as to maintain the namespace.
Any headers included with DELETE MUST be applied in processing every
resource to be deleted.
When the DELETE method has completed processing it MUST return a
consistent namespace.
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The response SHOULD be a Multi-Status response that describes the
result of the DELETE on each affected resource.
7.8.2.1 Example
>>Request
DELETE /container/ HTTP/1.1
Host: www.foo.bar
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="d"?>
<d:multistatus>
<d:response>
<d:href>http://www.foo.bar/container/resource1</d:href>
<d:href>http://www.foo.bar/container/resource2</d:href>
<d:status>HTTP/1.1 200 OK</d:status>
</d:response>
<d:response>
<d:href>http://www.foo.bar/container/</d:href>
<d:status>HTTP/1.1 424 Method Failure</d:status>
</d:response>
<d:response>
<d:href>http://www.foo.bar/container/resource3</d:href>
<d:status>HTTP/1.1 425 Locked</d:status>
</d:response>
</d:multistatus>
In this example the attempt to delete
http://www.foo.bar/container/resource3 failed because it is locked,
and no lock token was submitted with the request. Consequently, the
attempt to delete http://www.foo.bar/container/ also failed, but
resource1 and resource2 were deleted. Even though a Depth header has
not been included, a depth of infinity is assumed because the method
is on a collection. As this example illustrates, DELETE processing
need not be atomic.
7.9 PUT
7.9.1 PUT for Non-Collection Resources
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 effected.
For example, if a server recognizes the content type of the request
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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.
7.9.2 PUT for Collections
As defined in the HTTP/1.1 specification [Fielding et al., 1997],
the "PUT method requests that the enclosed entity be stored under
the supplied Request-URI." Since submission of an entity
representing a collection would implicitly encode creation and
deletion of resources, this specification intentionally does not
define a transmission format for creating a collection using PUT.
Instead, the MKCOL method is defined to create collections. If a
PUT is invoked on a collection resource it MUST fail.
When the PUT operation creates a new non-collection resource all
ancestors MUST already exist. If all ancestors do not exist, the
method MUST fail with a 409 Conflict status code. For example, if
resource /a/b/c/d.html is to be created and /a/b/c/ does not exist,
then the request must fail.
7.10 COPY Method
The COPY method creates a duplicate of the source resource, given by
the Request-URI, in the destination resource, given by the
Destination header. The Destination header MUST be present. The
exact behavior of the COPY method depends on the type of the source
resource.
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 even be possible to copy a
resource to a location that appears to be on the same server.
7.10.1 COPY for HTTP/1.1 resources
When the source resource is not a collection the body of the
destination resource MUST be octet-for-octet identical to the body
of the source resource. Subsequent alterations to the destination
resource will not modify the source resource. Subsequent
alterations to the source resource will not modify the destination
resource. Thus, all copies are performed "by-value".
All properties on the source resource MUST be duplicated on the
destination resource, subject to modifying headers and XML elements,
following the definition for copying properties.
7.10.2 COPY for Properties
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The following section defines how properties on a resource are
handled during a COPY operation.
Live properties SHOULD be duplicated as identically behaving live
properties at the destination resource. If a property cannot be
copied live, then its value MUST be duplicated, octet-for-octet, in
an identically named, dead property on the destination resource.
The propertybehavior XML element can specify that properties are
copied on best effort, that all live properties MUST be successfully
copied or the method MUST fail, or that a specified list of live
properties MUST be successfully copied or the method must fail. The
propertybehavior XML element is defined in Section 11.12.
If a property on the source already exists on the destination
resource and the Overwrite header is set to "T" then the property at
the destination MUST be overwritten with the property from the
source. If the Overwrite header is "F" and the previous situation
exists, then the COPY MUST fail with a 412 Precondition Failed.
7.10.3 COPY for Collections
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". DAV compliant servers MUST support the "0" and
"infinity" behaviors.
A COPY of depth infinity instructs that the collection specified in
the Request-URI and the records of its external member resources is
to be copied to the location specified 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, the
properties, and the records of its external members, not its
internal members, are to be copied.
Any headers included with a COPY are to be applied in processing
every resource to be copied.
The exception to this rule is the Destination header. This header
only specifies the destination for the Request-URI. When applied to
members of the collection specified in 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" and the destination is "b"
then when a/c/d is processed it MUST use a destination of b/c/d.
When the COPY method has completed processing it MUST have created a
consistent namespace at the destination. However, if an error
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occurs while copying an internal member collection, all members of
this collection MUST NOT be copied. In this case, after detecting
the error, the COPY operation SHOULD try to finish as much of the
original copy operation as possible. 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.
The response is a Multi-Status status code with an entity body that
describes the result of the COPY on each affected resource. The
href XML element in the response refers to the resource that was to
be copied, not the resource that was created as a result of the
copy. In other words, each entry indicates whether the copy on the
resource specified in the href XML element succeeded or failed and
why.
The exception to this rule is for errors that occurred on the
destination. For example, if the destination was locked the
response would indicate the destination URL and a 425 Locked error.
7.10.4 Type Interactions
If the destination resource identifies a collection and the
Overwrite header is "T", prior to performing the copy the server
MUST perform a DELETE operation on the collection.
7.10.5 Status Codes
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. Since there is no entity body in
the response, 204 No Content is used instead of 200 OK.
412 Precondition Failed - This status code MUST be returned if the
server was unable to maintain the liveness of the properties listed
in the propertybehavior XML element, or if the Overwrite header is
"F", and the state of the destination resource is non-null.
423 Insufficient Space on Resource - The destination resource does
not have sufficient space to record the state of the resource after
the execution of this method.
425 Locked - The destination resource was locked and either a valid
Lock-Token header was not submitted, or the Lock-Token header
identifies a lock held by another principal.
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502 Bad Gateway - This may occur when the destination is on another
server and the destination server refuses to accept the resource.
7.10.6 Overwrite Example
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.
>>Request
COPY /~fielding/index.html HTTP/1.1
Host: www.ics.uci.edu
Destination: http://www.ics.uci.edu/users/f/fielding/index.html
>>Response
HTTP/1.1 204 No Content
7.10.7 No Overwrite Example
The following example shows the same copy operation being performed,
except with the Overwrite header set to "F." A response of 412
Precondition Failed is returned because the destination resource has
a non-null state.
>>Request
COPY /~fielding/index.html HTTP/1.1
Host: www.ics.uci.edu
Destination: http://www.ics.uci.edu/users/f/fielding/index.html
Overwrite: F
>>Response
HTTP/1.1 412 Precondition Failed
7.10.8 Collection Example
>>Request
COPY /container/ HTTP/1.1
Host: www.foo.bar
Destination: http://www.foo.bar/othercontainer/
Depth: infinity
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="d"?>
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<d:propertybehavior>
<d:keepalive>*</d:keepalive>
</d:propertybehavior>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="d"?>
<d:multistatus>
<d:response>
<d:href>http://www.foo.bar/othercontainer/resource1</d:href>
<d:href>http://www.foo.bar/othercontainer/resource2</d:href>
<d:href>http://www.foo.bar/othercontainer/</d:href>
<d:status>HTTP/1.1 201 Created</d:status>
</d:response>
<d:response>
<d:href>http://www.foo.bar/othercontainer/R2/</d:href>
<d:href>http://www.foo.bar/othercontainer/R2/D2</d:href>
<d:status>HTTP/1.1 412 Precondition Failed</d:status>
</d:response>
</d:multistatus>
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, most likely due to a problem with maintaining the liveness
of properties (this is specified by the propertybehavior XML
element). Since an error occurred copying R2, R2's member D2 was not
copied.
7.11 MOVE Method
The MOVE operation on a non-collection resource is the logical
equivalent of a copy (COPY) followed by a delete, where the actions
are performed atomically. All DAV 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 even be possible to move
a resource within a namespace that appears to belong to the same
server.
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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.
7.11.1 MOVE for Collections
A MOVE of depth infinity instructs that the collection specified in
the Request-URI, including the records of its external member
resources, is to be moved to the location specified in the
Destination header, and all its internal member resources 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 are to be applied in processing every
resource to be moved.
The exception to this rule is the Destination header. The behavior
of this header is the same as given for COPY on collections.
When the MOVE method has completed processing it MUST have created a
consistent namespace on both the source and destination. However, if
an error occurs while moving an internal member collection, all
members of the failed collection MUST NOT be moved. In this case,
after detecting the error, the move operation SHOULD try to finish
as much of the original move as possible. 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.
As specified in the definition of MOVE, a MOVE of a collection over
another collection causes the destination collection and all its
members to be deleted.
The response is a Multi-Status response that describes the result of
the MOVE on each affected resource. The href XML element in the
response refers to the resource that was to be moved, not the
resource that was created as a result of the move. In other words,
each entry indicates whether the move on the resource specified in
the href succeeded or failed and why.
The exception to this rule is for errors that occurred on the
destination. For example, if the destination was locked the
response would indicate the destination URL and a 425 Locked error.
7.11.2 Status Codes
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201 Created - The source resource was successfully moved, and a new
resource was created at the destination.
204 No Content - The move operation was successful, and the resource
at the destination was overwritten.
412 Precondition Failed - This status code MUST be returned if the
server was unable to maintain the liveness of the properties listed
in the propertybehavior XML element, or if the Overwrite header is
"F", and the state of the destination resource is non-null.
425 Locked - The source or the destination resource was locked and
either a valid Lock-Token header was not submitted, or the Lock-
Token header identifies a lock held by another principal.
502 Bad Gateway - This may occur when the destination is on another
server and the destination server refuses to accept the resource.
7.11.3 Non-Collection Example
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 resource had been non-null. In this case, since
there was nothing at the destination resource, the response code is
201 Created.
>>Request
MOVE /~fielding/index.html HTTP/1.1
Host: www.ics.uci.edu
Destination: http://www.ics.uci.edu/users/f/fielding/index.html
>>Response
HTTP/1.1 201 Created
Location: http://www.ics.uci.edu/users/f/fielding/index.html
7.11.4 Collection Example
>>Request
MOVE /container/ HTTP/1.1
Host: www.foo.bar
Destination: http://www.foo.bar/othercontainer/
Overwrite: F
Lock-Token: <opaquelocktoken:fe184f2e-6eec-41d0-c765-01adc56e6bb4>,
<opaquelocktoken:e454f3f3-acdc-452a-56c7-00a5c91e4b77>
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Content-Type: text/xml
Content-Length: xyz
Authorization: Digest username="rohit",
realm="rohit@www.foo.bar", nonce="...",
uri="/container/", response="...",
opaque="..."
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="d"?>
<d:propertybehavior>
<d:keepalive>*</d:keepalive>
</d:propertybehavior>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: zzz
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="d"?>
<d:multistatus>
<d:response>
<d:href>http://www.foo.bar/container/resource1</d:href>
<d:href>http://www.foo.bar/container/resource2</d:href>
<d:href>http://www.foo.bar/container/</d:href>
<d:status>HTTP/1.1 204 No Content</d:status>
</d:response>
<d:response>
<d:href>http://www.foo.bar/container/C2/R2</d:href>
<d:status>HTTP/1.1 424 Method Failure</d:status>
<d:response>
<d:href>http://www.foo.bar/othercontainer/C2/</d:href>
<d:status>HTTP/1.1 425 Locked</d:status>
</d:response>
</d:multistatus>
In this example the client has submitted a number of lock tokens
with the request. A lock token will need to be submitted for every
resource, both source and destination, anywhere in the scope of the
method, that is locked. In this case the proper lock token was not
submitted for the destination http://www.foo.bar/othercontainer/C2/.
This means that the resource /container/C2/ could not be moved. As
the attempt to move /container/C2/ failed then the resource
/container/C2/R2 MUST also fail since it is a child of
/container/C2/.
7.12 LOCK Method
The following sections describe the LOCK method, which is used to
take out a lock of any access type. These sections on the LOCK
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method describe only those semantics that are specific to the LOCK
method and are independent of the access type of the lock being
requested.
7.12.1 Operation
A LOCK method invocation creates the lock specified by the lockinfo
XML element on the Request-URI. Lock method requests SHOULD have a
XML request body which contains an owner XML element for this lock
request, unless this is a refresh request. The LOCK request MAY have
a Timeout header.
A successful response to a lock invocation MUST include Lock-Token
and Timeout headers. 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,
an administrator 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. The response MUST also contain the value of the
lockdiscovery property in a prop XML element.
7.12.2 The Effect of Locks on Properties and Collections
The scope of a lock is the entire state of the resource, including
its body and associated properties. As a result, a lock on a
resource also locks the resource's properties.
For collections, a lock also affects the ability to add or remove
members. The nature of the effect depends upon the type of access
control involved.
7.12.3 Locking Replicated Resources
Some servers automatically replicate resources across multiple URLs.
In such a circumstance the server MAY only accept a lock on one of
the URLs if the server can guarantee that the lock will be honored
across all the URLs.
7.12.4 Depth and Locking
The Depth header MAY be used with the LOCK method. Values other
than 0 or infinity MUST NOT be used with 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 will
return a single lock token which represents all the resources that
have been locked. If an UNLOCK is executed on this token, all
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associated resources are unlocked. If the lock cannot be granted to
all resources, a 409 Conflict status code MUST be returned with a
response entity body containing a multistatus XML element describing
which resource(s) prevented the lock from being granted. Hence,
partial success is not an option. Either the entire hierarchy is
locked or no resources are locked.
7.12.5 Interaction with other Methods
The interaction of a LOCK with various methods is dependent upon the
lock type. However, independent of lock type, a successful DELETE
of a resource MUST cause all of its locks to be removed.
7.12.6 Lock Compatibility Table
The table below describes the behavior that occurs when a lock
request is made on a resource.
Current lock state/ Shared Lock Exclusive
Lock request Lock
None True True
Shared Lock True False
Exclusive Lock False False*
Legend: True = lock MAY be granted. False = lock MUST NOT be
granted. *=if the principal requesting the lock is the owner of the
lock, the lock MUST be regranted.
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.
If an exclusive or shared lock is re-requested by the principal who
owns the lock, the lock MUST be regranted. If the lock is
regranted, the same lock token that was previously issued MUST be
returned.
7.12.7 Lock Response
A successful lock response MUST contain a Lock-Token response
header, a Timeout header and a prop XML element in the response body
which contains the value of the lockdiscovery property.
7.12.8 Status Codes
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412 Precondition Failed - The included Lock-Token was not
enforceable on this resource or the server could not satisfy the
request in the lockinfo XML element.
425 Locked - The resource is locked, so the method has been
rejected.
7.12.9 Example - Simple Lock Request
>>Request
LOCK /workspace/webdav/proposal.doc HTTP/1.1
Host: webdav.sb.aol.com
Timeout: Infinite, Second-4100000000
Content-Type: text/xml
Content-Length: xyz
Authorization: Digest username="ejw",
realm="ejw@webdav.sb.aol.com", nonce="...",
uri="/workspace/webdav/proposal.doc",
response="...", opaque="..."
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="D"?>
<D:lockinfo>
<D:locktype><D:write/></D:locktype>
<D:lockscope><D:exclusive/></D:lockscope>
<D:owner>
<D:href>http://www.ics.uci.edu/~ejw/contact.html</D:href>
</D:owner>
</D:lockinfo>
>>Response
HTTP/1.1 200 OK
Lock-Token: <opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4>
Timeout: Second-604800
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<D:prop>
<D:lockdiscovery>
<D:activelock>
<D:locktype><D:write/></D:locktype>
<D:lockscope><D:exclusive/></D:lockscope>
<D:owner>
<D:href>http://www.ics.uci.edu/~ejw/contact.html</D:href>
</D:owner>
<D:timeout>Second-604800</D:timeout>
<D:locktoken>
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<D:href>
opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4
</D:href>
</D:locktoken>
</D:activelock>
</D:lockdiscovery>
</D:prop>
This example shows the successful creation of an exclusive write
lock on resource
http://webdav.sb.aol.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). The
response has a Lock-Token header that gives the lock token URL that
uniquely identifies the lock created by this lock request. Note
that the nonce, response, and opaque fields have not been calculated
in the Authorization request header.
7.12.10 Example - Refreshing a Write Lock
>>Request
LOCK /workspace/webdav/proposal.doc HTTP/1.1
Host: webdav.sb.aol.com
Timeout: Infinite, Second-4100000000
Lock-Token: <opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4>
Authorization: Digest username="ejw",
realm="ejw@webdav.sb.aol.com", nonce="...",
uri="/workspace/webdav/proposal.doc",
response="...", opaque="..."
>>Response
HTTP/1.1 200 OK
Lock-Token: <opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4>
Timeout: Second-604800
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<D:prop>
<D:lockdiscovery>
<D:activelock>
<D:locktype><D:write/></D:locktype>
<D:lockscope><D:exclusive/></D:lockscope>
<D:owner>
<D:href>http://www.ics.uci.edu/~ejw/contact.html</D:href>
</D:owner>
<D:timeout>Second-604800</D:timeout>
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<D:locktoken>
<D:href>
opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4
</D:href>
</D:locktoken>
</D:activelock>
</D:lockdiscovery>
</D:prop>
This request would refresh the lock, resetting any time outs.
Notice that the client asked for an infinite time out but the server
choose to ignore the request. In this example, the nonce, response,
and opaque fields have not been calculated in the Authorization
request header.
7.12.11 Example - Multi-Resource Lock Request
>>Request
LOCK /webdav/ HTTP/1.1
Host: webdav.sb.aol.com
Timeout: Infinite, Second-4100000000
Depth: infinity
Authorization: Digest username="ejw",
realm="ejw@webdav.sb.aol.com", nonce="...",
uri="/workspace/webdav/proposal.doc",
response="...", opaque="..."
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="D"?>
<D:lockinfo>
<D:locktype><D:write/></D:locktype>
<D:lockscope><D:exclusive/></D:lockscope>
<D:owner>
<D:href>http://www.ics.uci.edu/~ejw/contact.html</D:href>
</D:owner>
</D:lockinfo>
>>Response
HTTP/1.1 207 Multistatus
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="D"?>
<D:multistatus>
<D:response>
<D:href>http://webdav.sb.aol.com/webdav/proposal.doc</D:href>
<D:href>http://webdav.sb.aol.com/webdav/</D:href>
<D:status>HTTP/1.1 424 Method Failure</D:status>
</D:response>
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<D:response>
<D:href>http://webdav.sb.aol.com/webdav/secret</D:href>
<D:status>HTTP/1.1 403 Forbidden</D:status>
</D:response>
</D:multistatus>
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 424 Method Failure indicates that a lock was not taken out on
these resources due to an error elsewhere. Note that this does not
mean that a lock would have succeeded on these resources had the
other error not occurred. It only means that another error has
occurred and so the entire method has been aborted. The error is a
403 Forbidden response on the resource
http://webdav.sb.aol.com/webdav/secret. Because this resource could
not be locked, none of the resources were locked.
In this example, the nonce, response, and opaque fields have not
been calculated in the Authorization request header.
7.13 UNLOCK Method
The UNLOCK method removes the lock identified by the lock token in
the Lock-Token header from the Request-URI, and all other resources
included in the lock.
Any DAV compliant resource which supports the LOCK method MUST
support the UNLOCK method.
7.13.1 Example
>>Request
UNLOCK /workspace/webdav/info.doc HTTP/1.1
Host: webdav.sb.aol.com
Lock-Token:<opaquelocktoken:a515cfa4-5da4-22e1-f5b5-00a0451e6bf7>
Authorization: Digest username="ejw",
realm="ejw@webdav.sb.aol.com", nonce="...",
uri="/workspace/webdav/proposal.doc",
response="...", opaque="..."
>>Response
HTTP/1.1 204 No Content
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In this example, the lock identified by the lock token
"opaquelocktoken:a515cfa4-5da4-22e1-f5b5-00a0451e6bf7" is
successfully removed from the resource
http://webdav.sb.aol.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 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.
8 HTTP Headers for Distributed Authoring
8.1 Collection-Member Header
CollectionMember = "Collection-Member" ":" absoluteURI ;
absoluteURI is defined in section 3.2.1 of [Fielding et al., 1997]
The Collection-Member header specifies the URI of an external
resource to be added/deleted to/from a collection.
8.2 DAV Header
DAV = "DAV" ":" ["1"] [",2"] ["," 1#extend]
This header indicates that the resource supports the DAV schema and
protocol as specified. All DAV compliant resources MUST return the
DAV header on all OPTIONS responses.
The value is a list of all compliance classes that the resource
supports. Note that above a comma has already been added to the 2.
This is because a resource can not be level 2 compliant unless it is
also level 1 compliant. Please refer to Section 13 for more details.
In general, however, support for one compliance class does not
entail support for any other.
8.3 Depth Header
Depth = "Depth" ":" ("0" | "1" | "infinity")
The Depth 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.
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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. Note that methods MAY provide guarantees on ordering and
atomicity.
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 with a Depth header MUST be applied to all
resources in the scope of the method. 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
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 Lock-Token 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 is 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, MUST 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.
8.4 Destination Header
Destination = "Destination" ":" URI
The Destination header specifies a destination resource for methods
such as COPY and MOVE, which take two URIs as parameters.
8.5 If-None-State-Match
If-None-State-Match = "If-None-State-Match" ":" 1#Coded-URL
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Coded-URL = "<" URI ">"
The If-None-State-Match header is intended to have similar
functionality to the If-None-Match header defined in section 14.26
of [Fielding et al., 1997]. However the If-None-State-Match header
is intended for use with any URI which represents state information
about a resource, referred to as a state token. A typical example
is a lock token.
If any of the state tokens identifies the current state of the
resource, the server MUST NOT perform the requested method.
Instead, if the request method was GET, HEAD, or PROPFIND, the
server SHOULD respond with a 304 Not Modified response, including
the cache-related entity-header fields (particularly ETag) of the
current state of the resource. For all other request methods, the
server MUST respond with a status of 412 Precondition Failed.
If none of the state tokens identifies the current state of the
resource, the server MAY perform the requested method.
If any of the tokens is not recognized, the method MUST fail with a
412 Precondition Failed.
Note that the "AND" and "OR" keywords specified with the If-State-
Match header are intentionally not defined for If-None-State-Match,
because this functionality is not required.
8.6 If-State-Match
If-State-Match = "If-State-Match" ":" ("AND" | "OR") 1#Coded-URL
The If-State-Match header is intended to have similar functionality
to the If-Match header defined in section 14.25 of [Fielding et al.,
1997]. However the If-State-Match header is intended for use with
any URI which represents state information about a resource. A
typical example is a lock token.
If the AND keyword is used and all of the state tokens identify the
state of the resource, then the server MAY perform the requested
method. If the OR keyword is used and any of the state tokens
identifies the current state of the resource, then the server MAY
perform the requested method. If the keyword requirement for the
keyword used is not met, the server MUST NOT perform the requested
method, and MUST return a 412 Precondition Failed response.
If any of the tokens is not recognized, the method MUST fail with a
412 Precondition Failed.
8.7 Lock-Token Request Header
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Lock-Token = "Lock-Token" ":" 1#Coded-URL
The Lock-Token request header, containing a lock token owned by the
requesting principal, is used by the principal to indicate that the
principal is aware of the existence of the lock specified by the
lock token.
If the following conditions are met:
1) The method is restricted by a lock type that requires the
submission of a lock token, such as a write lock,
2) The user-agent has authenticated itself as a given principal,
3) The user-agent is submitting a method request to a resource on
which the principal owns a write lock,
Then:
1) The method request MUST include a Lock-Token header with the lock
token, or,
2) The method MUST fail with a 409 Conflict status code.
If multiple resources are involved with a method, such as the MOVE
method, then the lock tokens, if any, for all affected resources,
MUST be included in the Lock-Token request header.
For example, Program A, used by user A, takes out a write lock on a
resource. Program A then makes a number of PUT requests on the
locked resource. All the requests contain a Lock-Token request
header that includes the write lock token. Program B, also run by
User A, then proceeds to perform a PUT to the locked resource.
However, program B was not aware of the existence of the lock and so
does not include the appropriate Lock-Token request header. The
method is rejected even though principal A is authorized to perform
the PUT. Program B can, if it so chooses, now perform lock
discovery and obtain the lock token. Note that programs A and B can
perform GETs without using the Lock-Token header because the ability
to perform a GET is not affected by a write lock.
Having a lock token provides no special access rights. Anyone can
find out anyone else's lock token by performing lock discovery.
Locks are to be enforced based upon whatever authentication
mechanism is used by the server, not based on the secrecy of the
token values.
8.8 Lock-Token Response Header
Lock-Token = "Lock-Token" ":" 1#Coded-URL
If a resource is successfully locked then a Lock-Token header will
be returned containing the lock token that represents the lock.
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If multiple lock-tokens are returned then they MUST all refer to the
same lock. As the lock tokens all refer to the same lock a client
need only record one of them.
8.9 Overwrite Header
Overwrite = "Overwrite" ":" ("T" | "F")
The Overwrite header specifies whether the server should overwrite
the state of a non-null destination resource during a COPY or MOVE.
A value of "F" states that the server MUST NOT perform the COPY or
MOVE operation if the state of the destination resource is non-null.
By default, the value of Overwrite is "T" and a client MAY omit this
header from a request when its value is "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 409 Conflict status code.
8.10 Status-URI Response Header
The Status-URI response header MAY be used with the 102 Processing
status code to inform the client as to the status of a method.
Status-URI = "Status-URI" ":" *(Status-Code "<" URI ">") ; Status-
Code is defined in 6.1.1 of [Fielding et al., 1997]
The URIs listed in the header are source resources which have been
affected by the outstanding method. The status code indicates the
resolution of the method on the identified resource. So, for
example, if a MOVE method on a collection is outstanding and a 102
"Processing" response with a Status-URI response header is returned,
the included URIs will indicate resources that have had move
attempted on them and what the result was.
8.11 Timeout Header
TimeOut = "Timeout" ":" 1#TimeType
TimeType = ("Second-" DAVTimeOutVal | "Infinite" | Other)
DAVTimeOutVal = 1*digit
Other = Extend field-value ; See section 4.2 of [Fielding et al.,
1997]
Clients MAY include Timeout 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.
A Timeout request header MUST contain at least one TimeType and MAY
contain multiple TimeType entries. The purpose of listing multiple
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TimeType entries is to indicate multiple different values and value
types that are acceptable to the client. The client lists the
TimeType entries in order of preference.
The Timeout response header MUST use a Second value, Infinite, or a
TimeType the client has indicated familiarity with. The server MAY
assume a client is familiar with any TimeType submitted in a Timeout
header.
The "Second" TimeType specifies the number of seconds that MUST
elapse between granting of the lock at the server, and the automatic
removal of the lock. A server MUST not generate a timeout value for
"Second" greater than 2^32-1.
The timeout counter SHOULD be restarted any time an owner of the
lock sends a method to any member of the lock, including unsupported
methods, or methods which are unsuccessful. However the lock MUST
be refreshed if a refresh LOCK method is successfully received.
If the timeout expires then the lock is lost. Specifically 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.
9 Status Code Extensions to HTTP/1.1
The following status codes are added to those defined in HTTP/1.1
[Fielding et al., 1997].
9.1 102 Processing
Methods can potentially take a long period of time to process,
especially methods that support the Depth header. In such cases the
client may time-out the connection while waiting for a response. To
prevent this the server MAY return a 102 status code to indicate to
the client that the server is still processing the method.
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If a method is taking longer than 20 seconds (a reasonable, but
arbitrary value) to process the server SHOULD return a 102
"Processing" response.
9.2 207 Multi-Status
The response provides status for multiple independent operations.
9.3 422 Unprocessable Entity
The server understands the content type of the request entity, but
was unable to process the contained instructions.
9.4 423 Insufficient Space on Resource
The resource does not have sufficient space to record the state of
the resource after the execution of this method.
9.5 424 Method Failure
The method was not executed on a particular resource within its
scope because some part of the method's execution failed causing the
entire method to be aborted. For example, if a resource could not
be moved as part of a MOVE method, all the other resources would
fail with a 424 Method Failure.
9.6 425 Locked
The source or destination resource of a method is locked, and either
the request did not contain a valid Lock-Token header, or the lock
token in the Lock-Token header identifies a lock held by another
principal.
10 Multi-Status Response
The default 207 Multi-Status response body is a text/xml HTTP entity
that contains a single XML element called multistatus, which
contains a set of XML elements called response, one for each 200,
300, 400, and 500 series status code generated during the method
invocation. 100 series status codes MUST NOT be recorded in a
response XML element.
11 XML Element Definitions
In the section below, the final line of each section gives the
element type declaration using the format defined in [Bray, Paoli,
Sperberg-McQueen, 1998]. The "Value" field, where present, specifies
futher restrictions on the allowable contents of the XML element
using BNF (i.e., to further restrict the values of a PCDATA
element).
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11.1 activelock XML Element
Name: activelock
Namespace: http://www.iana.org/standards/dav/
Purpose: Describes a lock on a resource.
<!ELEMENT activelock (locktype, lockscope, depth?, owner, timeout,
locktoken) >
11.1.1 depth XML Element
Name: depth
Namespace: http://www.iana.org/standards/dav/
Purpose: The value of the depth header used to create a lock.
Description: If this element is not included in a lockinfo element
then the client MUST assume that the lock is of depth 0.
Value: "0" | "infinity"
<!ELEMENT depth (#PCDATA) >
11.1.2 locktoken XML Element
Name: locktoken
Namespace: http://www.iana.org/standards/dav/
Purpose: The lock token associated with a lock.
Description: The href contains an opaque lock token URI (i.e., the
OpaqueLockToken-URI production in Section 4.4).
<!ELEMENT locktoken (href) >
11.1.3 timeout XML Element
Name: timeout
Namespace: http://www.iana.org/standards/dav/
Purpose: The timeout associated with a lock
Value: TimeType
<!ELEMENT timeout (#PCDATA) >
11.2 collection XML Element
Name: collection
Namespace: http://www.iana.org/standards/dav/
Purpose: Identifies the associated resource as a collection. The
resourcetype property of a collection resource MUST have this value.
<!ELEMENT collection EMPTY >
11.3 href XML Element
Name: href
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Namespace: http://www.iana.org/standards/dav/
Purpose: Identifies the content of the element as a URI.
Value: URI ; See section 3.2.1 of [Fielding et al., 1997]
<!ELEMENT href (#PCDATA)>
11.4 link XML Element
Name: link
Namespace: http://www.iana.org/standards/dav/
Purpose: Identifies the property as a link and contains the
source and destination of that link.
Description: The link XML element is used to provide the sources and
destinations of a link. The name of the property containing the
link XML element provides the type of the link. Link is a multi-
valued element, so multiple links may be used together to indicate
multiple links with the same type.
<!ELEMENT link (src+, dst+) >
11.4.1 dst XML Element
Name: dst
Namespace: http://www.iana.org/standards/dav/
Purpose: Indicates the destination of a link
Value: URI
<!ELEMENT dst (#PCDATA) >
11.4.2 src XML Element
Name: src
Namespace: http://www.iana.org/standards/dav/
Purpose: Indicates the source of a link.
Value: URI
<!ELEMENT src (#PCDATA) >
11.5 lockentry XML Element
Name: lockentry
Namespace: http://www.iana.org/standards/dav/
Purpose: Defines the types of locks that can be used with the
resource.
<!ELEMENT lockentry (lockscope, locktype) >
11.6 lockinfo XML Element
Name: lockinfo
Namespace: http://www.iana.org/standards/dav/
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Purpose: The lockinfo XML element is used with a LOCK method to
specify the type of lock the client wishes to have created.
<!ELEMENT lockinfo (lockscope, locktype, owner?) >
11.7 lockscope XML Element
Name: lockscope
Namespace: http://www.iana.org/standards/dav/
Purpose: Specifies whether a lock is an exclusive lock, or a
shared lock.
<!ELEMENT lockscope (exclusive | shared) >
11.7.1 exclusive XML Element
Name: exclusive
Namespace: http://www.iana.org/standards/dav/
Purpose: Specifies an exclusive lock
<!ELEMENT exclusive EMPTY >
11.7.2 shared XML Element
Name: shared
Namespace: http://www.iana.org/standards/dav/
Purpose: Specifies a shared lock
<!ELEMENT shared EMPTY >
11.8 locktype XML Element
Name: locktype
Namespace: http://www.iana.org/standards/dav/
Purpose: Specifies the access type of a lock. At present, this
specification only defines one lock type, the write lock.
<!ELEMENT locktype (write) >
11.8.1 write XML Element
Name: write
Namespace: http://www.iana.org/standards/dav/
Purpose: Specifies a write lock.
<!ELEMENT write EMPTY >
11.9 multistatus XML Element
Name: multistatus
Namespace: http://www.iana.org/standards/dav/
Purpose: Contains multiple response messages.
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Description: The responsedescription at the top level is used to
provide a general message describing the overarching nature of the
response. If this value is available an application MAY use it
instead of presenting the individual response descriptions contained
within the responses.
<!ELEMENT multistatus (response+, responsedescription?) >
11.9.1 response XML Element
Name: response
Namespace: http://www.iana.org/standards/dav/
Purpose: Holds a single response describing the effect of a
method on resource and/or its properties.
Description: A particular href MUST NOT appear more than once as the
child of a response XML element under a multistatus XML element.
This requirement is necessary in order to keep processing costs for
a response to linear time. Essentially, this prevents having to
search in order to group together all the responses by href. There
are, however, no requirements regarding ordering based on href
values.
<!ELEMENT response (href, ((href*, status)|(propstat+)),
responsedescription?) >
11.9.1.1 propstat XML Element
Name: propstat
Namespace: http://www.iana.org/standards/dav/
Purpose: Groups together a prop and status element that is
associated with a particular href element.
Description: Prop MUST contain one or more empty XML elements
representing the names of properties. Multiple properties may be
included if the same response applies to them all.
<!ELEMENT propstat (prop, status) >
11.9.1.2 status XML Element
Name: status
Namespace: http://www.iana.org/standards/dav/
Purpose: Holds a single HTTP status-line
Value: status-line ;status-line defined in [Fielding et al.,
1997]
<!ELEMENT status (#PCDATA) >
11.9.2 responsedescription XML Element
Name: responsedescription
Namespace: http://www.iana.org/standards/dav/
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Purpose: Contains a message that can be displayed to the user
explaining the nature of the response.
Description: This XML element provides information suitable to be
presented to a user.
<!ELEMENT responsedescription (#PCDATA) >
11.10 owner XML Element
Name: owner
Namespace: http://www.iana.org/standards/dav/
Purpose: Provides information about the principal taking out a
lock.
Description: The owner XML element provides information sufficient
for either directly contacting a principal (such as a telephone
number or Email URI), or for discovering the principal (such as the
URL of a homepage) who owns a lock.
<!ELEMENT owner (#PCDATA, ANY)* >
11.11 prop XML element
Name: prop
Namespace: http://www.iana.org/standards/dav/
Purpose: Contains properties related to a resource.
Description: The prop XML element is a generic container for
properties defined on resources. All elements inside prop MUST
define properties related to the resource. No other elements may be
used inside of a prop element.
<!ELEMENT prop ANY>
11.12 propertybehavior XML element
Name: propertybehavior
Namespace: http://www.iana.org/standards/dav/
Purpose: Specifies how properties are handled during a COPY or
MOVE.
Description: The propertybehavior XML element specifies how
properties are handled during a COPY or MOVE. If this XML element
is not included in the request body then the server is expected to
act as defined by the default property handling behavior of the
associated method.
<!ELEMENT propertybehavior (omit | keepalive) >
11.12.1 keepalive XML element
Name: keepalive
Namespace: http://www.iana.org/standards/dav/
Purpose: Specifies requirements for the copying/moving of live
properties.
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Description: If a list of URIs is included as the value of keepalive
then the named properties MUST be "live" after they are copied
(moved) to the destination resource of a COPY (or MOVE). If the
value "*" is given for the keepalive XML element, this designates
that all live properties on the source resource MUST be live on the
destination.
Value: "*" ; #PCDATA value can only be "*"
<!ELEMENT keepalive (#PCDATA | href+) >
11.12.2 omit XML element
Name: omit
Namespace: http://www.iana.org/standards/dav/
Purpose: Indicates that the associated method MAY succeed even if
the server is not able to copy/move every property on the source
resource, even in a dead form.
Description: The default behavior for a COPY or MOVE is to copy/move
all properties or fail the method. In certain circumstances, such
as when a server copies a resource over another protocol such as
FTP, it may not be possible to copy/move the properties associated
with the resource. Thus any attempt to copy/move over FTP would
always have to fail because properties could not be moved over, even
as dead properties. The omit XML element instructs the server that
it should use best effort to copy properties but a failure to copy a
property should not cause the method to fail.
<!ELEMENT omit EMPTY >
11.13 propertyupdate XML element
Name: propertyupdate
Namespace: http://www.iana.org/standards/dav/
Purpose: Contains a request to alter the properties on a
resource.
Description: This XML element is a container for the information
required to modify the properties on the resource. This XML element
is multi-valued.
<!ELEMENT propertyupdate (remove | set)+ >
11.13.1 remove XML element
Name: remove
Namespace: http://www.iana.org/standards/dav/
Purpose: Lists the DAV properties to be removed from a resource.
Description: Remove instructs that the properties specified in prop
should be removed. Specifying the removal of a property that does
not exist is not an error. All the XML elements in prop MUST be
empty, as only the names of properties to be removed are required.
<!ELEMENT remove (prop) >
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11.13.2 set XML element
Name: set
Namespace: http://www.iana.org/standards/dav/
Purpose: Lists the DAV property values to be set for a resource.
Value: prop
Description: This XML element MUST contain only a prop XML element.
The elements contained by prop specify the name and value of
properties that are set on the Request-URI. If a property already
exists then its value is replaced.
<!ELEMENT set (prop) >
11.14 propfind XML Element
Name: propfind
Namespace: http://www.iana.org/standards/dav/
Purpose: Specifies the properties to be returned from a PROPFIND
method. Two special elements are specified for use with propfind,
allprop and propname.
<!ELEMENT propfind (allprop | propname | href+) >
11.14.1 allprop XML Element
Name: allprop
Namespace: http://www.iana.org/standards/dav/
Purpose: The allprop XML element specifies that all property
names and values on the resource are to be returned.
<!ELEMENT allprop EMPTY >
11.14.2 propname XML Element
Name: propname
Namespace: http://www.iana.org/standards/dav/
Purpose: the propname XML element specifies that only a list of
property names on the resource is to be returned.
<!ELEMENT propname EMPTY >
12 DAV Properties
For DAV properties, the name of the property is also the same as the
name of the XML element which contains its value. In the section
below, the final line of each section gives the element type
declaration using the format defined in [Bray, Paoli, Sperberg-
McQueen, 1998]. The "Value" field, where present, specifies futher
restrictions on the allowable contents of the XML element using BNF
(i.e., to further restrict the values of a PCDATA element).
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12.1 creationdate Property
Name: creationdate
Namespace: http://www.iana.org/standards/dav/
Purpose: Records the time and date the resource was created.
Value: ;The time and date MUST be given in ISO 8601 format
defined in Appendix 2
Description: This property SHOULD be defined on all DAV compliant
resources. If present, it contains a timestamp of the moment when
the resource was created (i.e., the moment it had non-null state).
<!ELEMENT creationdate (#PCDATA) >
12.2 displayname Property
Name: displayname
Namespace: http://www.iana.org/standards/dav/
Purpose: Provies a name for the resource that is suitable for
presentation to a user.
Description: This 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.
<!ELEMENT displayname (#PCDATA) >
12.3 externalmembers Property
Name: externalmembers
Namespace: http://www.iana.org/standards/dav/
Purpose: Provides the list of external members defined on the
resource.
Description: This property MUST be defined on any DAV compliant
resource with external members. If defined it MUST contain the full
list of external members. Resources MAY make this property read-
only, thus only allowing its value to be altered using the
ADDREF/DELREF methods.
<!ELEMENT externalmembers (href*) >
12.4 getcontentlanguage Property
Name: getcontentlanguage
Namespace: http://www.iana.org/standards/dav/
Purpose: Contains the Content-Language header returned by a GET
without accept headers
Description: This property MUST be defined on any DAV compliant
resource which supports GET, with the exception that if no Content-
Language header is available, this property MUST NOT exist.
Value: language-tag ;language-tag is defined in section 14.13
of [Fielding et al., 1997]
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<!ELEMENT getcontentlanguage (#PCDATA) >
12.5 getcontentlength Property
Name: getcontentlength
Namespace: http://www.iana.org/standards/dav/
Purpose: Contains the Content-Length header returned by a GET
without accept headers. If no Content-Length header is available,
this property MUST NOT exist.
Description: This property MUST be defined on any DAV compliant
resource which returns the Content-Length header in response to a
GET.
Value: content-length ; see section 14.14 of [Fielding et al.,
1997]
<!ELEMENT getcontentlength (#PCDATA) >
12.6 getcontenttype Property
Name: getcontenttype
Namespace: http://www.iana.org/standards/dav/
Purpose: Contains the Content-Type header returned by a GET
without accept headers. If no Content-Type header is available,
this property MUST NOT exist.
Description: This property MUST be defined on any DAV compliant
resource which returns the Content-Type header in response to a GET.
Value: media-type ; defined in Section 3.7 of [Fielding et
al., 1997]
<!ELEMENT getcontenttype (#PCDATA) >
12.7 getetag Property
Name: getetag
Namespace: http://www.iana.org/standards/dav/
Purpose: Contains the ETag header returned by a GET without
accept headers.
Description: Note that the ETag on a resource may reflect changes in
any part of the state of the resource, not necessarily just a change
to the response to the GET method. For example, a change to a
resource's access permissions may cause the ETag to change. This
property MUST be defined on any DAV compliant resource which returns
the Etag header in response to a GET, except for the case if no ETag
header is returned, this property MUST NOT exist.
Value: entity-tag ; defined in Section 3.11 of [Fielding et
al., 1997]
<!ELEMENT getetag (#PCDATA) >
12.8 getlastmodified Property
Name: getlastmodified
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Namespace: http://www.iana.org/standards/dav/
Purpose: Contains the Last-Modified header returned by a GET
method without accept headers.
Description: Note that the last-modified date on a resource may
reflect changes in any part of the state of the resource, not
necessarily just a change to the response to the GET method. For
example, a change in a property may cause the last-modified date to
change. This property MUST be defined on any DAV compliant resource
which returns the Last-Modified header in response to a GET, except
for the case if no Last-Modified header is returned, this property
MUST NOT exist.
Value: HTTP-date ; defined in Section 3.3.1 of [Fielding et
al., 1997]
<!ELEMENT getlastmodified (#PCDATA) >
12.9 lockdiscovery Property
Name: lockdiscovery
Namespace: http://www.iana.org/standards/dav/
Purpose: Describes the active locks on a resource
Description: The lockdiscovery property returns a listing of who has
a lock, what type of lock he has, the timeout type and the time
remaining on the timeout, and the associated lock token. The server
is free to withhold any or all of this information if the requesting
principal does not have sufficient access rights to see the
requested data. A server which supports locks MUST provide the
lockdiscovery property on any resource with locks on it.
<!ELEMENT lockdiscovery (activelock)* >
12.9.1 Example
>>Request
PROPFIND /container/ HTTP/1.1
Host: www.foo.bar
Content-Length: xxxx
Content-Type: text/xml
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="D"?>
<D:propfind>
<D:prop><lockdiscovery/></D:prop>
</D:propfind>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxxx
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<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<D:multistatus>
<D:response>
<D:propstat>
<D:prop>
<D:lockdiscovery>
<D:activelock>
<D:locktype>write</D:locktype>
<D:lockscope>exclusive</D:lockscope>
<D:Depth>0</D:Depth>
<D:owner>Jane Smith</D:owner>
<D:timeout>Infinite</D:timeout>
<D:locktoken>
<D:href>
opaquelocktoken:f81de2ad-7f3d-a1b2-4f3c-00a0c91a9d76
</D:href>
</D:locktoken>
</D:activelock>
</D:lockdiscovery>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
This resource has a single exclusive write lock on it, with an
infinite timeout. Note that the Depth element could have been
omitted as 0 is the default value of Depth.
12.10 resourcetype Property
Name: resourcetype
Namespace: http://www.iana.org/standards/dav/
Purpose: Specifies the nature of the resource.
Description: This property MUST be defined on all DAV compliant
resources. The default value is empty.
<!ELEMENT resourcetype ANY >
12.11 source Property
Name: source
Namespace: http://www.iana.org/standards/dav/link/
Purpose: The destination of the source link identifies the
resource that contains the unprocessed source of the link's source.
Description: The source of the link (src) is typically the URI of
the output resource on which the link is defined, and there is
typically only one destination (dst) of the link, which is the URI
where the unprocessed source of the resource may be accessed. When
more than one link destination exists, this specification asserts no
policy on ordering.
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<!ELEMENT source (link)* >
12.11.1 Example
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="D"?>
<?namespace href="http://www.foocorp.com/Project/" as="F"?>
<D:prop>
<D:source>
<D:link>
<F:projfiles>Source</F:projfiles>
<D:src>http://foo.bar/program</D:src>
<D:dst>http://foo.bar/src/main.c</D:dst>
</D:link>
<D:link>
<F:projfiles>Library</F:projfiles>
<D:src>http://foo.bar/program</D:src>
<D:dst>http://foo.bar/src/main.lib</D:dst>
</D:link>
<D:link>
<F:projfiles>Makefile</F:projfiles>
<D:src>http://foo.bar/program</D:src>
<D:dst>http://foo.bar/src/makefile</D:dst>
</D:link>
</D:source>
</D:prop>
In this example the resource http://foo.bar/program has a source
property that contains three links. Each link contains three
elements, two of which, src and dst, are part of the DAV schema
defined in this document, and one which is defined by the schema
http://www.foocorp.com/project/ (Source, Library, and Makefile). A
client which only implements the elements in the DAV spec will not
understand the foocorp elements and will ignore them, thus seeing
the expected source and destination links. An enhanced client may
know about the foocorp elements and be able to present the user with
additional information about the links. This example demonstrates
the power of XML markup, allowing element values to be enhanced
without breaking older clients.
12.12 supportedlock Property
Name: supportedlock
Namespace: http://www.iana.org/standards/dav/
Purpose: To provide a listing of the lock capabilities supported
by the resource.
Description: The supportedlock property of a resource returns a
listing of the combinations of scope and access types which may be
specified in a lock request on the resource. Note that the actual
contents are themselves controlled by access controls so a server is
not required to provide information the client is not authorized to
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see. If supportedlock is available on "*" then it MUST define the
set of locks allowed on all resources on that server.
<!ELEMENT supportedlock (lockentry)* >
12.12.1 Example
>>Request
PROPFIND /container/ HTTP/1.1
Host: www.foo.bar
Content-Length: xxxx
Content-Type: text/xml
<?xml version="1.0"?>
<?namespace href="http://www.iana.org/standards/dav/" as="D"?>
<D:propfind>
<D:prop><supportedlock/></D:prop>
</D:propfind>
>>Response
HTTP/1.1 207 Multi-Status
Content-Type: text/xml
Content-Length: xxxxx
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<D:multistatus>
<D:response>
<D:propstat>
<D:prop>
<D:supportedlock>
<D:LockEntry>
<D:locktype><D:Write/></D:locktype>
<D:lockscope><D:Exclusive/></D:lockscope>
</D:LockEntry>
<D:LockEntry>
<D:locktype><D:Write/></D:locktype>
<D:lockscope><D:Shared/></D:lockscope>
</D:LockEntry>
</D:supportedlock>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
13 DAV Compliance Classes
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A DAV compliant resource can choose from two 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.
Since this document describes extensions to the HTTP/1.1 protocol,
minimally all DAV compliant resources, clients, and proxies MUST be
compliant with [Fielding et al., 1997].
Compliance classes are not necessarily sequential. A resource that
is class 2 compliant MUST also be class 1 compliant; but if
additional compliance classes are defined later, a resource that is
class 1, 2, and 4 compliant might not be class 3 compliant.
13.1 Class 1
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.
13.2 Class 2
A class 2 compliant resource MUST meet all class 1 requirements and
support the supportedlock property as well as the LOCK method. It
MUST also support the lockdiscovery property, since Section 12.9
specifies that the LOCK method MUST also support the lockdiscovery
property.
Class 2 compliant resources MUST return, at minimum, the value "2"
in the DAV header on all responses to the OPTIONS method.
14 Internationalization Considerations
In the realm of internationalization, this specification complies
with the IETF Character Set Policy [Alvestrand, 1998]. 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 using the UTF-8 and UCS-2 encodings of the ISO 10646 basic
multilingual plane. Furthermore, XML contains provisions for
encoding XML elements using other encoding schemes, notable among
them UCS-4, which permits encoding of characters from any ISO 10646
character plane.
The default character set encoding for XML data in this
specification, and in general, is UTF-8. WebDAV compliant
applications MUST support the UTF-8 and UCS-2 character set
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encodings for XML elements, and SHOULD support the UCS-4 encoding.
The XML character set encoding declaration for each supported
character set MUST also be supported, since it is by using this
encoding declaration that an XML processor determines the encoding
of an element.
XML also provides a language tagging capability for specifying the
language of the contents of a particular XML element. XML uses
either IANA registered language tags (see RFC 1766, [Alvestrand,
1995]) or ISO 639 language tags [ISO-639] in the "xml:lang"
attribute of an XML element to identify the language its content and
attributes.
Names used within this specification fall into three categories:
names of protocol elements such as methods and headers, names of XML
elements, and names of properties. 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 in fact simply long token identifiers,
they do not need to support encoding in multiple character sets.
Similarly, though the names of XML elements used in this
specification are English names encoded in UTF-8, these names are
not visible to the user, and hence do not need to support multiple
character set encodings.
The name of a property defined on a resource is a URI. Although
some applications (e.g., a generic property viewer) will display
property URIs 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 URI 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 URI 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., 425 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.
15 Security Considerations
This section is provided to detail issues concerning security
implications of which WebDAV applications need to be aware.
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All of the security considerations of HTTP/1.1 also apply to WebDAV.
In addition, the security risks inherent in remote authoring require
stronger authentication technology, and introduce several new
privacy concerns, and may increase the hazards from poor server
design. These issues are detailed below.
15.1 Authentication of Clients
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, 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
[Franks, et al., 1997]. 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.
15.2 Denial of Service
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.
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WebDAV servers need to be aware of the possibility of a denial of
service attack at all levels.
15.3 Security through Obscurity
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 which
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.
15.4 Privacy Issues Connected to Locks
When submitting a lock request a user agent may also submit an owner
XML field giving contact information for the person taking out the
lock (for those cases where a person, rather than a robot, is taking
out the lock). This contact information is stored in a lockdiscovery
property on the resource, and can be used by other collaborators to
begin negotiation over access to the resource. However, in many
cases this contact information can be very private, and should not
be widely disseminated. Servers SHOULD limit read access to the
lockdiscovery property as appropriate. Furthermore, user agents
SHOULD provide control over whether contact information is sent at
all, and if contact information is sent, control over exactly what
information is sent.
15.5 Privacy Issues Connected to Properties
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.
15.6 Reduction of Security due to Source Link
HTTP/1.1 warns against providing read access to script code because
it may contain sensitive information. Yet WebDAV, via its source
link facility, can potentially provide a URL for script resources so
they may be authored. For HTTP/1.1, a server could reasonably
prevent access to source resources due to the predominance of read-
only access. WebDAV, with its emphasis on authoring, encourages
read and write access to source resources, and provides the source
link facility to identify the source. This reduces the security
benefits of eliminating access to source resources. Users and
administrators of WebDAV servers should be very cautious when
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allowing remote authoring of scripts, limiting read and write access
to the source resources to authorized principals.
16 IANA Considerations
This document defines two namespaces, the namespace of property
names, and the namespace of WebDAV-specific XML elements used within
property values.
URLs are used for both names, for several reasons. Assignment of a
URL does not require a request to a central naming authority, and
hence allow WebDAV property names and XML elements to be quickly
defined by any WebDAV user or application. URLs also provide a
unique address space, ensuring that the distributed users of WebDAV
will not have collisions among the property names and XML elements
they create.
This specification defines a distinguished set of property names and
XML elements which are understood by all WebDAV applications. The
property names and XML elements in this specification are all
derived from the base URL: http://www.iana.org/standards/dav/ by
adding a suffix to this URL, for example,
http://www.iana.org/standards/dav/creationdate for the
"creationdate" property.
To ensure correct interoperation of this specification, IANA MUST
reserve the URL namespace starting with
http://www.iana.org/standards/dav/ for use by this specification,
its revisions, and related WebDAV specifications.
17 Terminology
Collection - A resource that contains member resources.
Member Resource - A resource contained by a collection. There are
two types of member resources: external and internal.
Internal Member Resource - A member resource of a collection whose
URI is relative to the URI of the collection.
External Member Resource - A member resource of a collection with an
absolute URI that is not relative to its parent's URI.
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, a live "content-length" property would
have its value, the length of the entity returned by a GET request,
automatically calculated by the server.
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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.
18 Copyright
The following copyright notice is copied from RFC 2026 [Bradner,
1996], Section 10.4, and describes the applicable copyright for this
document.
Copyright (C) The Internet Society January 18, 1998. All Rights
Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
19 Intellectual Property
The following notice is copied from RFC 2026 [Bradner, 1996],
Section 10.4, and describes the position of the IETF concerning
intellectual property claims made against this document.
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use other technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
Goland et al. [Page 74]
INTERNET-DRAFT WebDAV January 18, 1998
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances
of licenses to be made available, or the result of an attempt made
to obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification
can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
20 Acknowledgements
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.
Terry Allen, Harald Alvestrand, Alan Babich, 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, Roy Fielding, Mark Fisher,
Alan Freier, George Florentine, Jim Gettys, Phill Hallam-Baker,
Dennis Hamilton, Steve Henning, Alex Hopmann, Andre van der Hoek,
Ben Laurie, Paul Leach, Ora Lassila, Karen MacArthur, Steven Martin,
Larry Masinter, Michael Mealling, Keith Moore, Henrik Nielsen, Kenji
Ota, Bob Parker, Glenn Peterson, Jon Radoff, Saveen Reddy, Henry
Sanders, Christopher Seiwald, Judith Slein, Mike Spreitzer, Einar
Stefferud, 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.
Goland et al. [Page 75]
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21 References
[Alvestrand, 1995] H. T. Alvestrand, "Tags for the Identification of
Languages." RFC 1766. Uninett. March, 1995.
[Alvestrand, 1998] H. T. Alvestrand, "IETF Policy on Character Sets
and Languages." RFC XXXX, BCP YY. Maxware. January, 1998.
[Bradner, 1996] S. Bradner, "The Internet Standards Process -
Revision 3." RFC 2026, BCP 9. Harvard University. October, 1996.
[Bradner, 1997] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels." RFC 2119, BCP 14. Harvard University. March,
1997.
[Bray, Paoli, Sperberg-McQueen, 1998] T. Bray, J. Paoli, C. M.
Sperberg-McQueen, "Extensible Markup Language (XML)." World Wide Web
Consortium Recommendation REC-XML-ZZZZ. http://www.w3.org/TR/PR-xml-
971208.
[Fielding et al., 1997] R. Fielding, J. Gettys, J. Mogul, H.
Frystyk, T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1."
RFC 2068. U.C. Irvine, DEC, MIT/LCS. January, 1997.
[ISO-639] ISO (International Organization for Standardization). ISO
639:1988. "Code for the representation of names of languages."
[ISO-8601] ISO (International Organization for Standardization). ISO
8601:1988. "Data elements and interchange formats - Information
interchange - Representation of dates and times."
[Lasher, Cohen, 1995] R. Lasher, D. Cohen, "A Format for
Bibliographic Records," RFC 1807. Stanford, Myricom. June, 1995.
[Leach, Salz, 1997] P. J. Leach, R. Salz, "UUIDs and GUIDs."
Internet-draft (expired), work-in-progress, February, 1997.
http://www.internic.net/internet-drafts/draft-leach-uuids-guids-
00.txt
[MARC, 1994] Network Development and MARC Standards, Office, ed.
1994. "USMARC Format for Bibliographic Data", 1994. Washington, DC:
Cataloging Distribution Service, Library of Congress.
[Miller et al., 1996] J. Miller, T. Krauskopf, P. Resnick, W.
Treese, "PICS Label Distribution Label Syntax and Communication
Protocols" Version 1.1, World Wide Web Consortium Recommendation
REC-PICS-labels-961031. http://www.w3.org/pub/WWW/TR/REC-PICS-
labels-961031.html.
[Slein et al., 1997] J. A. Slein, F. Vitali, E. J. Whitehead, Jr.,
D. Durand, "Requirements for Distributed Authoring and Versioning
Goland et al. [Page 76]
INTERNET-DRAFT WebDAV January 18, 1998
Protocol for the World Wide Web." RFC XXXX. Xerox, Univ. of Bologna,
U.C. Irvine, Boston Univ. YYY, 1997.
[Weibel et al., 1995] S. Weibel, J. Godby, E. Miller, R. Daniel,
"OCLC/NCSA Metadata Workshop Report."
http://purl.oclc.org/metadata/dublin_core_report.
[Yergeau, 1997] F. Yergeau, "UTF-8, a transformation format of
Unicode and ISO 10646." RFC 2044. Alis Technologies. October, 1996.
Goland et al. [Page 77]
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22 Authors' Addresses
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
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23 Appendices
23.1 Appendix 1 - WebDAV Document Type Definition
This section provides a document type definition, following the
rules in [Bray, Paoli, Sperberg-McQueen, 1998], for the XML elements
used in the protocol stream and in the values of properties. It
collects the element definitions given in Sections 11 and 12.
<!DOCTYPE webdav-1.0 [
<!--============ XML Elements from Section 11 ==================-->
<!ELEMENT activelock (locktype, lockscope, depth?, owner, timeout,
locktoken) >
<!ELEMENT lockentry (lockscope, locktype) >
<!ELEMENT lockinfo (lockscope, locktype, owner?) >
<!ELEMENT locktype (write) >
<!ELEMENT write EMPTY >
<!ELEMENT lockscope (exclusive | shared) >
<!ELEMENT exclusive EMPTY >
<!ELEMENT shared EMPTY >
<!ELEMENT depth (#PCDATA) >
<!ELEMENT owner (#PCDATA, ANY)* >
<!ELEMENT timeout (#PCDATA) >
<!ELEMENT locktoken (href) >
<!ELEMENT href (#PCDATA) >
<!ELEMENT link (src+, dst+) >
<!ELEMENT dst (#PCDATA) >
<!ELEMENT src (#PCDATA) >
<!ELEMENT multistatus (response+, responsedescription?) >
<!ELEMENT response (href, ((href*, status)|(propstat+)),
responsedescription?) >
<!ELEMENT status (#PCDATA) >
<!ELEMENT propstat (prop status) >
<!ELEMENT responsedescription (#PCDATA) >
<!ELEMENT prop ANY >
<!ELEMENT propertybehavior (omit | keepalive) >
<!ELEMENT omit EMPTY >
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<!ELEMENT keepalive (#PCDATA | href+) >
<!ELEMENT propertyupdate (remove | set)+ >
<!ELEMENT remove (prop) >
<!ELEMENT set (prop) >
<!ELEMENT propfind (allprop | propname | href+) >
<!ELEMENT allprop EMPTY >
<!ELEMENT propname EMPTY >
<!ELEMENT collection EMPTY >
<!--=========== Property Elements from Section 12 ===============-->
<!ELEMENT creationdate (#PCDATA) >
<!ELEMENT displayname (#PCDATA) >
<!ELEMENT externalmembers (href*) >
<!ELEMENT getcontentlanguage (#PCDATA) >
<!ELEMENT getcontentlength (#PCDATA) >
<!ELEMENT getcontenttype (#PCDATA) >
<!ELEMENT getetag (#PCDATA) >
<!ELEMENT getlastmodified (#PCDATA) >
<!ELEMENT lockdiscovery (activelock)* >
<!ELEMENT resourcetype ANY >
<!ELEMENT source (link)* >
<!ELEMENT supportedlock (lockentry)* >
]>
23.2 Appendix 2 - ISO 8601 Date and Time Profile
The creationdate property specifies the use of the ISO 8601 date
format. This section defines a profile of the ISO 8601 date format
for use with this specification. This profile is quoted verbatim
from draft-newman-datetime-01.txt (expired).
date-time = full-date "T" full-time
full-date = date-fullyear "-" date-month "-" date-mday
full-time = partial-time time-offset
date-fullyear = 4DIGIT
date-month = 2DIGIT ; 01-12
date-mday = 2DIGIT ; 01-28, 01-29, 01-30, 01-31 based on
month/year
time-hour = 2DIGIT ; 00-23
time-minute = 2DIGIT ; 00-59
time-second = 2DIGIT ; 00-59, 00-60 based on leap second rules
time-secfrac = "." 1*DIGIT
time-numoffset = ("+" / "-") time-hour ":" time-minute
time-offset = "Z" / time-numoffset
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partial-time = time-hour ":" time-minute ":" time-second
[time-secfrac]
Numeric offsets are calculated as local time minus UTC (Coordinated
Universal Time). So the equivalent time in UTC can be determined by
subtracting the offset from the local time. For example, 18:50:00-
04:00 is the same time as 22:58:00Z.
If the time in UTC is known, but the offset to local time is
unknown, this can be represented with an offset of "-00:00". This
differs from an offset of "Z" which implies that UTC is the
preferred reference point for the specified time.
23.3 Appendix 3 - Notes on Processing XML Elements
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.
23.3.1 XML Syntax Error Example
The following request body for a PROPFIND method is illegal.
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<D:propfind>
<D:allprop/>
<D:propname/>
</D:propfind>
The definition of the propfind element only allows for the allprop
or the propname element, not both. Thus the above is an error and
MUST be responded to with a 400 Bad Request.
Imagine, however, that a server wanted to be "kind" and decided to
pick the allprop element as the true element and respond to it. A
client running over a bandwidth limited line who intended to execute
a propname would be in for a big surprise if the server treated the
command as an allprop.
23.3.2 Unknown XML Element Example
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The previous example was illegal because it contained two elements
that were explicitly banned from appearing together in the propfind
element. However, XML is an extensible language, so one can imagine
new elements being defined for use with propfind. Below is the
request body of a PROPFIND and, like the previous example, MUST be
rejected with a 400 Bad Request by a server that does not understand
the expired-props element.
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<?namespace href="http://www.foo.bar/standards/props/" as="E"?>
<D:propfind>
<E:expired-props/>
</D:propfind>
To understand why a 400 Bad Request is returned let us look at the
request body as the server unfamiliar with expired-props sees it.
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<?namespace href="http://www.foo.bar/standards/props/" as="E"?>
<D:propfind>
</D:propfind>
As the server does not understand the expired-props element, by the
rules of XML, 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:
<?xml version="1.0"?>
<?namespace href ="http://www.iana.org/standards/dav/" as="D"?>
<?namespace href="http://www.foo.bar/standards/props/" as="E"?>
<D:propfind>
<D:propname/>
<E:leave-out>*boss*</E:leave-out>
</D:propfind>
The previous example contains the fictitious element leave-out. Its
purpose is to prevent the return of any property whose name matches
the submitted pattern. If the previous example were submitted to a
server unfamiliar with leave-out, the only result would be that the
leave-out element would be ignored and a propname would be executed.
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