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rfc:rfc2518

Network Working Group Y. Goland Request for Comments: 2518 Microsoft Category: Standards Track E. Whitehead

                                                           UC Irvine
                                                            A. Faizi
                                                            Netscape
                                                           S. Carter
                                                              Novell
                                                           D. Jensen
                                                              Novell
                                                       February 1999
        HTTP Extensions for Distributed Authoring -- WEBDAV

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1999).  All Rights Reserved.

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).

Table of Contents

 ABSTRACT............................................................1
 1 INTRODUCTION .....................................................5
 2 NOTATIONAL CONVENTIONS ...........................................7
 3 TERMINOLOGY ......................................................7
 4 DATA MODEL FOR RESOURCE PROPERTIES ...............................8
 4.1  The Resource Property Model ...................................8
 4.2  Existing Metadata Proposals ...................................8
 4.3  Properties and HTTP Headers ...................................9
 4.4  Property Values ...............................................9
 4.5  Property Names ...............................................10
 4.6  Media Independent Links ......................................10
 5 COLLECTIONS OF WEB RESOURCES ....................................11

Goland, et al. Standards Track [Page 1] RFC 2518 WEBDAV February 1999

 5.1  HTTP URL Namespace Model .....................................11
 5.2  Collection Resources .........................................11
 5.3  Creation and Retrieval of Collection Resources ...............12
 5.4  Source Resources and Output Resources ........................13
 6 LOCKING .........................................................14
 6.1  Exclusive Vs. Shared Locks ...................................14
 6.2  Required Support .............................................16
 6.3  Lock Tokens ..................................................16
 6.4  opaquelocktoken Lock Token URI Scheme ........................16
  6.4.1  Node Field Generation Without the IEEE 802 Address ........17
 6.5  Lock Capability Discovery ....................................19
 6.6  Active Lock Discovery ........................................19
 6.7  Usage Considerations .........................................19
 7 WRITE LOCK ......................................................20
 7.1  Methods Restricted by Write Locks ............................20
 7.2  Write Locks and Lock Tokens ..................................20
 7.3  Write Locks and Properties ...................................20
 7.4  Write Locks and Null Resources ...............................21
 7.5  Write Locks and Collections ..................................21
 7.6  Write Locks and the If Request Header ........................22
  7.6.1  Example - Write Lock ......................................22
 7.7  Write Locks and COPY/MOVE ....................................23
 7.8  Refreshing Write Locks .......................................23
 8 HTTP METHODS FOR DISTRIBUTED AUTHORING ..........................23
 8.1  PROPFIND .....................................................24
  8.1.1  Example - Retrieving Named Properties .....................25
  8.1.2  Example - Using allprop to Retrieve All Properties ........26
  8.1.3  Example - Using propname to Retrieve all Property Names ...29
 8.2  PROPPATCH ....................................................31
  8.2.1  Status Codes for use with 207 (Multi-Status) ..............31
  8.2.2  Example - PROPPATCH .......................................32
 8.3  MKCOL Method .................................................33
  8.3.1  Request ...................................................33
  8.3.2  Status Codes ..............................................33
  8.3.3  Example - MKCOL ...........................................34
 8.4  GET, HEAD for Collections ....................................34
 8.5  POST for Collections .........................................35
 8.6  DELETE .......................................................35
  8.6.1  DELETE for Non-Collection Resources .......................35
  8.6.2  DELETE for Collections ....................................36
 8.7  PUT ..........................................................36
  8.7.1  PUT for Non-Collection Resources ..........................36
  8.7.2  PUT for Collections .......................................37
 8.8  COPY Method ..................................................37
  8.8.1  COPY for HTTP/1.1 resources ...............................37
  8.8.2  COPY for Properties .......................................38
  8.8.3  COPY for Collections ......................................38
  8.8.4  COPY and the Overwrite Header .............................39

Goland, et al. Standards Track [Page 2] RFC 2518 WEBDAV February 1999

  8.8.5  Status Codes ..............................................39
  8.8.6  Example - COPY with Overwrite .............................40
  8.8.7  Example - COPY with No Overwrite ..........................40
  8.8.8  Example - COPY of a Collection ............................41
 8.9  MOVE Method ..................................................42
  8.9.1  MOVE for Properties .......................................42
  8.9.2  MOVE for Collections ......................................42
  8.9.3  MOVE and the Overwrite Header .............................43
  8.9.4  Status Codes ..............................................43
  8.9.5  Example - MOVE of a Non-Collection ........................44
  8.9.6  Example - MOVE of a Collection ............................44
 8.10 LOCK Method ..................................................45
  8.10.1 Operation .................................................46
  8.10.2 The Effect of Locks on Properties and Collections .........46
  8.10.3 Locking Replicated Resources ..............................46
  8.10.4 Depth and Locking .........................................46
  8.10.5 Interaction with other Methods ............................47
  8.10.6 Lock Compatibility Table ..................................47
  8.10.7 Status Codes ..............................................48
  8.10.8 Example - Simple Lock Request .............................48
  8.10.9 Example - Refreshing a Write Lock .........................49
  8.10.10 Example - Multi-Resource Lock Request ....................50
 8.11 UNLOCK Method ................................................51
  8.11.1 Example - UNLOCK ..........................................52
 9 HTTP HEADERS FOR DISTRIBUTED AUTHORING ..........................52
 9.1  DAV Header ...................................................52
 9.2  Depth Header .................................................52
 9.3  Destination Header ...........................................54
 9.4  If Header ....................................................54
  9.4.1  No-tag-list Production ....................................55
  9.4.2  Tagged-list Production ....................................55
  9.4.3  not Production ............................................56
  9.4.4  Matching Function .........................................56
  9.4.5  If Header and Non-DAV Compliant Proxies ...................57
 9.5  Lock-Token Header ............................................57
 9.6  Overwrite Header .............................................57
 9.7  Status-URI Response Header ...................................57
 9.8  Timeout Request Header .......................................58
 10  STATUS CODE EXTENSIONS TO HTTP/1.1 ............................59
 10.1 102 Processing ...............................................59
 10.2 207 Multi-Status .............................................59
 10.3 422 Unprocessable Entity .....................................60
 10.4 423 Locked ...................................................60
 10.5 424 Failed Dependency ........................................60
 10.6 507 Insufficient Storage .....................................60
 11  MULTI-STATUS RESPONSE .........................................60
 12  XML ELEMENT DEFINITIONS .......................................61
 12.1 activelock XML Element .......................................61

Goland, et al. Standards Track [Page 3] RFC 2518 WEBDAV February 1999

  12.1.1 depth XML Element .........................................61
  12.1.2 locktoken XML Element .....................................61
  12.1.3 timeout XML Element .......................................61
 12.2 collection XML Element .......................................62
 12.3 href XML Element .............................................62
 12.4 link XML Element .............................................62
  12.4.1 dst XML Element ...........................................62
  12.4.2 src XML Element ...........................................62
 12.5 lockentry XML Element ........................................63
 12.6 lockinfo XML Element .........................................63
 12.7 lockscope XML Element ........................................63
  12.7.1 exclusive XML Element .....................................63
  12.7.2 shared XML Element ........................................63
 12.8 locktype XML Element .........................................64
  12.8.1 write XML Element .........................................64
 12.9 multistatus XML Element ......................................64
  12.9.1 response XML Element ......................................64
  12.9.2 responsedescription XML Element ...........................65
 12.10 owner XML Element ...........................................65
 12.11 prop XML element ............................................66
 12.12 propertybehavior XML element ................................66
  12.12.1 keepalive XML element ....................................66
  12.12.2 omit XML element .........................................67
 12.13 propertyupdate XML element ..................................67
  12.13.1 remove XML element .......................................67
  12.13.2 set XML element ..........................................67
 12.14 propfind XML Element ........................................68
  12.14.1 allprop XML Element ......................................68
  12.14.2 propname XML Element .....................................68
 13  DAV PROPERTIES ................................................68
 13.1 creationdate Property ........................................69
 13.2 displayname Property .........................................69
 13.3 getcontentlanguage Property ..................................69
 13.4 getcontentlength Property ....................................69
 13.5 getcontenttype Property ......................................70
 13.6 getetag Property .............................................70
 13.7 getlastmodified Property .....................................70
 13.8 lockdiscovery Property .......................................71
  13.8.1 Example - Retrieving the lockdiscovery Property ...........71
 13.9 resourcetype Property ........................................72
 13.10 source Property .............................................72
  13.10.1 Example - A source Property ..............................72
 13.11 supportedlock Property ......................................73
  13.11.1 Example - Retrieving the supportedlock Property ..........73
 14  INSTRUCTIONS FOR PROCESSING XML IN DAV ........................74
 15  DAV COMPLIANCE CLASSES ........................................75
 15.1 Class 1 ......................................................75
 15.2 Class 2 ......................................................75

Goland, et al. Standards Track [Page 4] RFC 2518 WEBDAV February 1999

 16  INTERNATIONALIZATION CONSIDERATIONS ...........................76
 17  SECURITY CONSIDERATIONS .......................................77
 17.1 Authentication of Clients ....................................77
 17.2 Denial of Service ............................................78
 17.3 Security through Obscurity ...................................78
 17.4 Privacy Issues Connected to Locks ............................78
 17.5 Privacy Issues Connected to Properties .......................79
 17.6 Reduction of Security due to Source Link .....................79
 17.7 Implications of XML External Entities ........................79
 17.8 Risks Connected with Lock Tokens .............................80
 18  IANA CONSIDERATIONS ...........................................80
 19  INTELLECTUAL PROPERTY .........................................81
 20  ACKNOWLEDGEMENTS ..............................................82
 21  REFERENCES ....................................................82
 21.1 Normative References .........................................82
 21.2 Informational References .....................................83
 22  AUTHORS' ADDRESSES ............................................84
 23  APPENDICES ....................................................86
 23.1 Appendix 1 - WebDAV Document Type Definition .................86
 23.2 Appendix 2 - ISO 8601 Date and Time Profile ..................88
 23.3 Appendix 3 - Notes on Processing XML Elements ................89
  23.3.1 Notes on Empty XML Elements ...............................89
  23.3.2 Notes on Illegal XML Processing ...........................89
 23.4 Appendix 4 -- XML Namespaces for WebDAV ......................92
  23.4.1 Introduction ..............................................92
  23.4.2 Meaning of Qualified Names ................................92
 24  FULL COPYRIGHT STATEMENT ......................................94

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 documents and to retrieve
 a hierarchical membership listing (like a directory listing in a file
 system).

Goland, et al. Standards Track [Page 5] RFC 2518 WEBDAV February 1999

 Locking: The ability to keep more than one person from working on a
 document at the same time. This prevents the "lost update problem,"
 in which modifications are lost as first one author then another
 writes changes without merging the other author's changes.
 Namespace Operations: The ability to instruct the server to copy and
 move Web resources.
 Requirements and rationale for these operations are described in a
 companion document, "Requirements for a Distributed Authoring and
 Versioning Protocol for the World Wide Web" [RFC2291].
 The sections below provide a detailed introduction to resource
 properties (section 4), collections of resources (section 5), and
 locking operations (section 6).  These sections introduce the
 abstractions manipulated by the WebDAV-specific HTTP methods
 described in section 8, "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) [REC-XML]
 request entity body, or in an HTTP header.  The use of XML to encode
 method parameters was motivated by the ability to add extra XML
 elements to existing structures, providing extensibility; and by
 XML's ability to encode information in ISO 10646 character sets,
 providing internationalization support. 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 9 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
 input.
 XML elements used in this specification are defined in section 12.
 The XML namespace extension (Appendix 4) is also used in this
 specification in order to allow for new XML elements to be added
 without fear of colliding with other element names.
 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 10.  Since some WebDAV methods may operate over many

Goland, et al. Standards Track [Page 6] RFC 2518 WEBDAV February 1999

 resources, the Multi-Status response has been introduced to return
 status information for multiple resources.  The Multi-Status response
 is described in section 11.
 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 13 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 15), on
 internationalization support (section 16), and on security (section
 17).

2 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 [RFC2068].  Since
 this augmented BNF uses the basic production rules provided in
 section 2.2 of [RFC2068], 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 [RFC2119].

3 Terminology

 URI/URL - A Uniform Resource Identifier and Uniform Resource Locator,
 respectively. These terms (and the distinction between them) are
 defined in [RFC2396].
 Collection - A resource that contains a set of URIs, termed member
 URIs, which identify member resources and meets the requirements in
 section 5 of this specification.
 Member URI - A URI which is a member of the set of URIs contained by
 a collection.
 Internal Member URI - A Member URI that is immediately relative to
 the URI of the collection (the definition of immediately relative is
 given in section 5.2).
 Property - A name/value pair that contains descriptive information
 about a resource.

Goland, et al. Standards Track [Page 7] RFC 2518 WEBDAV February 1999

 Live Property - A property whose semantics and syntax are enforced by
 the server.  For example, the live "getcontentlength" property has
 its value, the length of the entity returned by a GET request,
 automatically calculated by the server.
 Dead Property - A property whose semantics and syntax are not
 enforced by the server.  The server only records the value of a dead
 property; the client is responsible for maintaining the consistency
 of the syntax and semantics of a dead property.
 Null Resource - A resource which responds with a 404 (Not Found) to
 any HTTP/1.1 or DAV method except for PUT, MKCOL, OPTIONS and LOCK.
 A NULL resource MUST NOT appear as a member of its parent collection.

4 Data Model for Resource Properties

4.1 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 its syntax and semantics.
 There are two categories of properties: "live" and "dead".  A live
 property has its syntax and semantics enforced by the server. Live
 properties include cases where a) the value of a property is read-
 only, maintained by the server, and b) the value of the property is
 maintained by the client, but the server performs syntax checking on
 submitted values. All instances of a given live property MUST comply
 with the definition associated with that property name.  A dead
 property has its syntax and semantics enforced by the client; the
 server merely records the value of the property verbatim.

4.2 Existing Metadata Proposals

 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 [REC-PICS], PICS-NG, XML, Web Collections, and several
 proposals on representing relationships within HTML. Work on PICS-NG

Goland, et al. Standards Track [Page 8] RFC 2518 WEBDAV February 1999

 and Web Collections has been subsumed by the Resource Description
 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 [RFC2413] metadata set and the Warwick
 Framework [WF], a container architecture for different metadata
 schemas.  The literature includes many examples of metadata,
 including MARC [USMARC], a bibliographic metadata format, and a
 technical report bibliographic format employed by the Dienst system
 [RFC1807]. 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 [WF],
 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.

4.3 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.

4.4 Property Values

 The value of a property when expressed in XML MUST be well formed.
 XML has been chosen because it is a flexible, self-describing,
 structured data format that supports rich schema definitions, and
 because of its support for multiple character sets.  XML's self-
 describing nature allows any property's value to be extended by
 adding new elements.  Older clients will not break when they
 encounter extensions because they will still have the data specified
 in the original schema and will ignore elements they do not
 understand.  XML's support for multiple character sets allows any
 human-readable property to be encoded and read in a character set
 familiar to the user.  XML's support for multiple human languages,

Goland, et al. Standards Track [Page 9] RFC 2518 WEBDAV February 1999

 using the "xml:lang" attribute, handles cases where the same
 character set is employed by multiple human languages.

4.5 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, on the same and across different servers, so long as that
 property is "live" on the resources in question, and the
 implementation of the live property is faithful to its definition.
 The XML namespace mechanism, which is based on URIs [RFC2396], 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.

4.6 Media Independent Links

 Although HTML resources support links to other resources, the Web
 needs more general support for links between resources of any media
 type (media types are also known as MIME types, or content types).
 WebDAV provides such links. A WebDAV link is a special type of
 property value, formally defined in section 12.4, that allows typed
 connections to be established between resources of any media type.
 The property value consists of source and destination Uniform
 Resource Identifiers (URIs); the property name identifies the link
 type.

Goland, et al. Standards Track [Page 10] RFC 2518 WEBDAV February 1999

5 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 URL
 namespace. The purpose of a collection resource is to model
 collection-like objects (e.g., file system directories) within a
 server's namespace.
 All DAV compliant resources MUST support the HTTP URL namespace model
 specified herein.

5.1 HTTP URL Namespace Model

 The HTTP URL namespace is a hierarchical namespace where the
 hierarchy is delimited with the "/" character.
 An HTTP URL namespace is said to be consistent if it meets the
 following conditions: for every URL in the HTTP hierarchy there
 exists a collection that contains that URL as an internal member.
 The root, or top-level collection of the namespace under
 consideration is exempt from the previous rule.
 Neither HTTP/1.1 nor WebDAV require that the entire HTTP URL
 namespace be consistent.  However, certain WebDAV methods are
 prohibited from producing results that cause namespace
 inconsistencies.
 Although implicit in [RFC2068] and [RFC2396], any resource, including
 collection resources, MAY be identified by more than one URI. For
 example, a resource could be identified by multiple HTTP URLs.

5.2 Collection Resources

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

Goland, et al. Standards Track [Page 11] RFC 2518 WEBDAV February 1999

 For all WebDAV compliant resources A and B, identified by URIs U and
 V, for which U is immediately relative to V, B MUST be a collection
 that has U as an internal member URI. So, if the resource with URL
 http://foo.com/bar/blah is WebDAV compliant and if the resource with
 URL http://foo.com/bar/ is WebDAV compliant then the resource with
 URL http://foo.com/bar/ must be a collection and must contain URL
 http://foo.com/bar/blah as an internal member.
 Collection resources MAY list the URLs of non-WebDAV compliant
 children in the HTTP URL namespace hierarchy as internal members but
 are not required to do so. For example, if the resource with URL
 http://foo.com/bar/blah is not WebDAV compliant and the URL
 http://foo.com/bar/ identifies a collection then URL
 http://foo.com/bar/blah may or may not be an internal member of the
 collection with URL http://foo.com/bar/.
 If a WebDAV compliant resource has no WebDAV compliant children in
 the HTTP URL namespace hierarchy then the WebDAV compliant resource
 is not required to be a collection.
 There is a standing convention that when a collection is referred to
 by its name without a trailing slash, the 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 content-location header in the response pointing to
 the URI 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 content-location header with
 http://foo.bar/blah/ in it.  In general clients SHOULD use the "/"
 form of collection names.
 A resource MAY be a collection but not be WebDAV compliant.  That is,
 the resource may comply with all the rules set out in this
 specification regarding how a collection is to behave without
 necessarily supporting all methods that a WebDAV compliant resource
 is required to support.  In such a case the resource may return the
 DAV:resourcetype property with the value DAV:collection but MUST NOT
 return a DAV header containing the value "1" on an OPTIONS response.

5.3 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:

Goland, et al. Standards Track [Page 12] RFC 2518 WEBDAV February 1999

 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.

5.4 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 URI at which a resource
 is accessed is identical to the URI 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, a server-
 side-include directive within an HTML file might 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 URI 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.

Goland, et al. Standards Track [Page 13] RFC 2518 WEBDAV February 1999

 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 the URI of the source resource(s) may be
 stored in a link on the output resource with type DAV:source (see
 section 13.10 for a description of the source link property).
 Storing the source URIs in links on the output resources places the
 burden of discovering the source on the authoring client.  Note that
 the value of a source link is not guaranteed to point to the correct
 source.  Source links may break or incorrect values may be entered.
 Also note that not all servers will allow the client to set the
 source link value.  For example a server which generates source links
 on the fly for its CGI files will most likely not allow a client to
 set the source link value.

6 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.

6.1 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 merge results.

Goland, et al. Standards Track [Page 14] RFC 2518 WEBDAV February 1999

 However, there are times when the goal of a lock is not to exclude
 others from exercising an access right but rather to provide a
 mechanism for principals to indicate that they intend to exercise
 their access rights.  Shared locks are provided for this case.  A
 shared lock allows multiple principals to receive a lock.  Hence any
 principal with appropriate access can 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 to the
 resource.  Among those who have access permission to write to the
 resource, the set of principals who have taken out a shared lock also
 must trust each other, creating a (typically) smaller trust set
 within the access permission write set.
 Starting with every possible principal on the Internet, in most
 situations the vast majority of these principals will not have write
 access to a given resource.  Of the small number who do have write
 access, some principals may decide to guarantee their edits are free
 from overwrite conflicts by using exclusive write locks.  Others may
 decide they trust their collaborators will not overwrite their work
 (the potential set of collaborators being the set of principals who
 have write permission) and use a shared lock, which informs their
 collaborators that a principal may be working on the resource.
 The WebDAV extensions to HTTP do not need to provide all of the
 communications paths necessary for principals to coordinate their
 activities.  When using shared locks, principals may use any out of
 band communication channel to coordinate their work (e.g., face-to-
 face interaction, written notes, post-it notes on the screen,
 telephone conversation, Email, etc.)  The intent of a shared lock is
 to let collaborators know who else may be working on a resource.
 Shared locks are included because experience from web distributed
 authoring systems has indicated that exclusive locks are often too
 rigid.  An exclusive lock is used to enforce a particular editing
 process: take out an exclusive lock, read the resource, perform
 edits, write the resource, release the lock.  This editing process
 has the problem that locks are not always properly released, for
 example when a program crashes, or when a lock owner leaves without
 unlocking a resource.  While both timeouts and administrative action
 can be used to remove an offending lock, neither mechanism may be
 available when needed; the timeout may be long or the administrator
 may not be available.

Goland, et al. Standards Track [Page 15] RFC 2518 WEBDAV February 1999

6.2 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.

6.3 Lock Tokens

 A lock token is a type of state token, represented as a URI, which
 identifies a particular lock.  A lock token is returned by every
 successful LOCK operation in the lockdiscovery property in the
 response body, and can also be found through lock discovery on a
 resource.
 Lock token URIs MUST be unique across all resources for all time.
 This uniqueness constraint allows lock tokens to be submitted across
 resources and servers without fear of confusion.
 This specification provides a lock token URI scheme called
 opaquelocktoken that meets the uniqueness requirements.  However
 resources are free to return any URI scheme so long as it meets the
 uniqueness requirements.
 Having a lock token provides no special access rights. Anyone can
 find out anyone else's lock token by performing lock discovery.
 Locks MUST be enforced based upon whatever authentication mechanism
 is used by the server, not based on the secrecy of the token values.

6.4 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 an If 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 does not refer to an
 outstanding lock on the resource.

Goland, et al. Standards Track [Page 16] RFC 2518 WEBDAV February 1999

 In order to guarantee uniqueness across all resources for all time
 the opaquelocktoken requires the use of the Universal Unique
 Identifier (UUID) mechanism, as described in [ISO-11578].
 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 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 representation of a UUID, as defined in
 [ISO-11578]. 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
 [RFC2068]

6.4.1 Node Field Generation Without the IEEE 802 Address

 UUIDs, as defined in [ISO-11578], contain a "node" field that
 contains one of the IEEE 802 addresses for the server machine.  As
 noted in section 17.8, there are several security risks associated
 with exposing a machine's IEEE 802 address. This section provides an
 alternate mechanism for generating the "node" field of a UUID which
 does not employ an IEEE 802 address.  WebDAV servers MAY use this
 algorithm for creating the node field when generating UUIDs.  The
 text in this section is originally from an Internet-Draft by Paul
 Leach and Rich Salz, who are noted here to properly attribute their
 work.
 The ideal solution is to obtain a 47 bit cryptographic quality random
 number, and use it as the low 47 bits of the node ID, with the most
 significant bit of the first octet of the node ID set to 1.  This bit
 is the unicast/multicast bit, which will never be set in IEEE 802
 addresses obtained from network cards; hence, there can never be a
 conflict between UUIDs generated by machines with and without network
 cards.
 If a system does not have a primitive to generate cryptographic
 quality random numbers, then in most systems there are usually a
 fairly large number of sources of randomness available from which one
 can be generated. Such sources are system specific, but often
 include:

Goland, et al. Standards Track [Page 17] RFC 2518 WEBDAV February 1999

  1. the percent of memory in use
  2. the size of main memory in bytes
  3. the amount of free main memory in bytes
  4. the size of the paging or swap file in bytes
  5. free bytes of paging or swap file
  6. the total size of user virtual address space in bytes
  7. the total available user address space bytes
  8. the size of boot disk drive in bytes
  9. the free disk space on boot drive in bytes
  10. the current time
  11. the amount of time since the system booted
  12. the individual sizes of files in various system directories
  13. the creation, last read, and modification times of files in

various system directories

  1. the utilization factors of various system resources (heap, etc.)
  2. current mouse cursor position
  3. current caret position
  4. current number of running processes, threads
  5. handles or IDs of the desktop window and the active window
  6. the value of stack pointer of the caller
  7. the process and thread ID of caller
  8. various processor architecture specific performance counters

(instructions executed, cache misses, TLB misses)

 (Note that it is precisely the above kinds of sources of randomness
 that are used to seed cryptographic quality random number generators
 on systems without special hardware for their construction.)
 In addition, items such as the computer's name and the name of the
 operating system, while not strictly speaking random, will help
 differentiate the results from those obtained by other systems.
 The exact algorithm to generate a node ID using these data is system
 specific, because both the data available and the functions to obtain
 them are often very system specific. However, assuming that one can
 concatenate all the values from the randomness sources into a buffer,
 and that a cryptographic hash function such as MD5 is available, then
 any 6 bytes of the MD5 hash of the buffer, with the multicast bit
 (the high bit of the first byte) set will be an appropriately random
 node ID.
 Other hash functions, such as SHA-1, can also be used. The only
 requirement is that the result be suitably random _ in the sense that
 the outputs from a set uniformly distributed inputs are themselves
 uniformly distributed, and that a single bit change in the input can
 be expected to cause half of the output bits to change.

Goland, et al. Standards Track [Page 18] RFC 2518 WEBDAV February 1999

6.5 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.

6.6 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 where available, provides their lock token.
 Any DAV compliant resource that supports the LOCK method MUST support
 the lockdiscovery property.

6.7 Usage Considerations

 Although the locking mechanisms specified here provide some help in
 preventing lost updates, they cannot guarantee that updates will
 never be lost.  Consider the following scenario:
 Two clients A and B are interested in editing the resource '
 index.html'.  Client A is an HTTP client rather than a WebDAV client,
 and so does not know how to perform locking.
 Client A doesn't lock the document, but does a GET and begins
 editing.
 Client B does LOCK, performs a GET and begins editing.
 Client B finishes editing, performs a PUT, then an UNLOCK.
 Client A performs a PUT, overwriting and losing all of B's changes.
 There are several reasons why the WebDAV protocol itself cannot
 prevent this situation.  First, it cannot force all clients to use
 locking because it must be compatible with HTTP clients that do not
 comprehend locking.  Second, it cannot require servers to support
 locking because of the variety of repository implementations, some of
 which rely on reservations and merging rather than on locking.
 Finally, being stateless, it cannot enforce a sequence of operations
 like LOCK / GET / PUT / UNLOCK.

Goland, et al. Standards Track [Page 19] RFC 2518 WEBDAV February 1999

 WebDAV servers that support locking can reduce the likelihood that
 clients will accidentally overwrite each other's changes by requiring
 clients to lock resources before modifying them.  Such servers would
 effectively prevent HTTP 1.0 and HTTP 1.1 clients from modifying
 resources.
 WebDAV clients can be good citizens by using a lock / retrieve /
 write /unlock sequence of operations (at least by default) whenever
 they interact with a WebDAV server that supports locking.
 HTTP 1.1 clients can be good citizens, avoiding overwriting other
 clients' changes, by using entity tags in If-Match headers with any
 requests that would modify resources.
 Information managers may attempt to prevent overwrites by
 implementing client-side procedures requiring locking before
 modifying WebDAV resources.

7 Write Lock

 This section describes the semantics specific to the write lock type.
 The write lock is a specific instance of a lock type, and is the only
 lock type described in this specification.

7.1 Methods Restricted by Write Locks

 A write lock MUST prevent a principal without the lock from
 successfully executing a PUT, POST, PROPPATCH, LOCK, UNLOCK, MOVE,
 DELETE, or MKCOL on the locked resource.  All other current methods,
 GET in particular, function independently of the lock.
 Note, however, that as new methods are created it will be necessary
 to specify how they interact with a write lock.

7.2 Write Locks and Lock Tokens

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

7.3 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.

Goland, et al. Standards Track [Page 20] RFC 2518 WEBDAV February 1999

 Only dead properties and live properties defined to respect locks are
 guaranteed not to change while write locked.

7.4 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, referred to as a lock-null resource,
 MUST respond with a 404 (Not Found) or 405 (Method Not Allowed) to
 any HTTP/1.1 or DAV methods except for PUT, MKCOL, OPTIONS, PROPFIND,
 LOCK, and UNLOCK.  A lock-null resource MUST appear as a member of
 its parent collection.  Additionally the lock-null resource MUST have
 defined on it all mandatory DAV properties.  Most of these
 properties, such as all the get* properties, will have no value as a
 lock-null resource does not support the GET method.  Lock-Null
 resources MUST have defined values for lockdiscovery and
 supportedlock properties.
 Until a method such as PUT or MKCOL is successfully executed on the
 lock-null resource the resource MUST stay in the lock-null state.
 However, once a PUT or MKCOL is successfully executed on a lock-null
 resource the resource ceases to be in the lock-null state.
 If the resource is unlocked, for any reason, without a PUT, MKCOL, or
 similar method having been successfully executed upon it then the
 resource MUST return to the null state.

7.5 Write Locks and Collections

 A write lock on a collection, whether created by a "Depth: 0" or
 "Depth: infinity" lock request, prevents the addition or removal of
 member URIs of the collection by non-lock owners.  As a consequence,
 when a principal issues a PUT or POST request to create a new
 resource under a URI which needs to be an internal member of a write
 locked collection to maintain HTTP namespace consistency, or issues a
 DELETE to remove a resource which has a URI which is an existing
 internal member URI of a write locked collection, 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
 member URIs identifying resources that are currently locked in a
 manner which conflicts with the write lock, the request MUST fail
 with a 423 (Locked) status code.
 If a lock owner causes the URI of a resource to be added as an
 internal member URI of a locked collection then the new resource MUST
 be automatically added to the lock.  This is the only mechanism that

Goland, et al. Standards Track [Page 21] RFC 2518 WEBDAV February 1999

 allows a resource to be added to a write lock.  Thus, for example, if
 the collection /a/b/ is write locked and the resource /c is moved to
 /a/b/c then resource /a/b/c will be added to the write lock.

7.6 Write Locks and the If 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 a lock token MUST be submitted
 by an authorized principal in the If header for all locked resources
 that a method may interact with or the method MUST fail.  For
 example, if a resource is to be moved and both the source and
 destination are locked then two lock tokens must be submitted, one
 for the source and the other for the destination.

7.6.1 Example - Write Lock

 >>Request
 COPY /~fielding/index.html HTTP/1.1
 Host: www.ics.uci.edu
 Destination: http://www.ics.uci.edu/users/f/fielding/index.html
 If: <http://www.ics.uci.edu/users/f/fielding/index.html>
     (<opaquelocktoken:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>)
 >>Response
 HTTP/1.1 204 No Content
 In this example, even though both the source and destination are
 locked, only one lock token must be submitted, for the lock on the
 destination.  This is because the source resource is not modified by
 a COPY, and hence unaffected by the write lock. In this example, user
 agent authentication has previously occurred via a mechanism outside
 the scope of the HTTP protocol, in the underlying transport layer.

Goland, et al. Standards Track [Page 22] RFC 2518 WEBDAV February 1999

7.7 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 locked with "Depth: infinity",
 then the resource will be added to the lock.
 A successful MOVE request on a write locked resource MUST NOT move
 the write lock with the resource. However, the resource is subject to
 being added to an existing lock at the destination, as specified in
 section 7.5. For example, if the MOVE makes the resource a child of a
 collection that is locked with "Depth: infinity", then the resource
 will be added to that collection's lock. Additionally, if a resource
 locked with "Depth: infinity" is moved to a destination that is
 within the scope of the same lock (e.g., within the namespace tree
 covered by the lock), the moved resource will again be a added to the
 lock. In both these examples, as specified in section 7.6, an If
 header must be submitted containing a lock token for both the source
 and destination.

7.8 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 in the If header in
 order to make the request for a resource that is already locked.
 However, a client may submit a LOCK method with an If header but
 without a body.  This form of LOCK MUST only be used to "refresh" a
 lock.  Meaning, at minimum, that any timers associated with the lock
 MUST be re-set.
 A server may return a Timeout header with a lock refresh that is
 different than the Timeout header returned when the lock was
 originally requested.  Additionally clients may submit Timeout
 headers of arbitrary value with their lock refresh requests.
 Servers, as always, may ignore Timeout headers submitted by the
 client.
 If an error is received in response to a refresh LOCK request the
 client SHOULD assume that the lock was not refreshed.

8 HTTP Methods for Distributed Authoring

 The following new HTTP methods use XML as a request and response
 format.  All DAV compliant clients and resources MUST use XML parsers
 that are compliant with [REC-XML].  All XML used in either requests
 or responses MUST be, at minimum, well formed.  If a server receives

Goland, et al. Standards Track [Page 23] RFC 2518 WEBDAV February 1999

 ill-formed XML in a request it MUST reject the entire request with a
 400 (Bad Request).  If a client receives ill-formed XML in a response
 then it MUST NOT assume anything about the outcome of the executed
 method and SHOULD treat the server as malfunctioning.

8.1 PROPFIND

 The PROPFIND method retrieves properties defined on the resource
 identified by the Request-URI, if the resource does not have any
 internal members, or on the resource identified by the Request-URI
 and potentially its member resources, if the resource is a collection
 that has internal member URIs.  All DAV compliant resources MUST
 support the PROPFIND method and the propfind XML element (section
 12.14) along with all XML elements defined for use with that element.
 A client may submit a Depth header with a value of "0", "1", or
 "infinity" with a PROPFIND on a collection resource with internal
 member URIs.  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 PROPFIND request body
 MUST be treated as a request for the names and values of all
 properties.
 All servers MUST support returning a response of content type
 text/xml or application/xml that contains a multistatus XML element
 that describes the results of the attempts to retrieve the various
 properties.
 If there is an error retrieving a property then a proper error result
 MUST be included in the response.  A request to retrieve the value of
 a property which does not exist is an error and MUST be noted, if the
 response uses a multistatus XML element, with a response XML element
 which contains a 404 (Not Found) status value.
 Consequently, the multistatus XML element for a collection resource
 with member URIs MUST include a response XML element for each member
 URI of the collection, to whatever depth was requested. Each response
 XML element MUST contain an href XML element that gives the URI of
 the resource on which the properties in the prop XML element are
 defined.  Results for a PROPFIND on a collection resource with
 internal member URIs are returned as a flat list whose order of
 entries is not significant.

Goland, et al. Standards Track [Page 24] RFC 2518 WEBDAV February 1999

 In the case of allprop and propname, if a principal does not have the
 right to know whether a particular property exists then the property
 should be silently excluded from the response.
 The results of this method SHOULD NOT be cached.

8.1.1 Example - Retrieving Named Properties

 >>Request
 PROPFIND  /file HTTP/1.1
 Host: www.foo.bar
 Content-type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:propfind xmlns:D="DAV:">
   <D:prop xmlns:R="http://www.foo.bar/boxschema/">
        <R:bigbox/>
        <R:author/>
        <R:DingALing/>
        <R:Random/>
   </D:prop>
 </D:propfind>
 >>Response
 HTTP/1.1 207 Multi-Status
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:multistatus xmlns:D="DAV:">
   <D:response>
        <D:href>http://www.foo.bar/file</D:href>
        <D:propstat>
             <D:prop xmlns:R="http://www.foo.bar/boxschema/">
                  <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>

Goland, et al. Standards Track [Page 25] RFC 2518 WEBDAV February 1999

             <D:status>HTTP/1.1 403 Forbidden</D:status>
             <D:responsedescription> The user does not have access to
 the DingALing property.
             </D:responsedescription>
        </D:propstat>
   </D:response>
   <D:responsedescription> There has been an access violation error.
   </D:responsedescription>
 </D:multistatus>
 In this example, PROPFIND is executed on a non-collection resource
 http://www.foo.bar/file.  The propfind XML element specifies the name
 of four properties whose values are being requested. In this case
 only two properties were returned, since the principal issuing the
 request did not have sufficient access rights to see the third and
 fourth properties.

8.1.2 Example - Using allprop to Retrieve All Properties

 >>Request
 PROPFIND  /container/ HTTP/1.1
 Host: www.foo.bar
 Depth: 1
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:propfind xmlns:D="DAV:">
   <D:allprop/>
 </D:propfind>
 >>Response
 HTTP/1.1 207 Multi-Status
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:multistatus xmlns:D="DAV:">
   <D:response>
        <D:href>http://www.foo.bar/container/</D:href>
        <D:propstat>
             <D:prop xmlns:R="http://www.foo.bar/boxschema/">
                  <R:bigbox>
                       <R:BoxType>Box type A</R:BoxType>
                  </R:bigbox>
                  <R:author>

Goland, et al. Standards Track [Page 26] RFC 2518 WEBDAV February 1999

                       <R:Name>Hadrian</R:Name>
                  </R:author>
                  <D:creationdate>
                       1997-12-01T17:42:21-08:00
                  </D:creationdate>
                  <D:displayname>
                       Example collection
                  </D:displayname>
                  <D:resourcetype><D:collection/></D:resourcetype>
                  <D:supportedlock>
                       <D:lockentry>
                            <D:lockscope><D:exclusive/></D:lockscope>
                            <D:locktype><D:write/></D:locktype>
                       </D:lockentry>
                       <D:lockentry>
                            <D:lockscope><D:shared/></D:lockscope>
                            <D:locktype><D:write/></D:locktype>
                       </D:lockentry>
                  </D:supportedlock>
             </D:prop>
             <D:status>HTTP/1.1 200 OK</D:status>
        </D:propstat>
   </D:response>
   <D:response>
        <D:href>http://www.foo.bar/container/front.html</D:href>
        <D:propstat>
             <D:prop xmlns:R="http://www.foo.bar/boxschema/">
                  <R:bigbox>
                       <R:BoxType>Box type B</R:BoxType>
                  </R:bigbox>
                  <D:creationdate>
                       1997-12-01T18:27:21-08:00
                  </D:creationdate>
                  <D:displayname>
                       Example HTML resource
                  </D:displayname>
                  <D:getcontentlength>
                       4525
                  </D:getcontentlength>
                  <D:getcontenttype>
                       text/html
                  </D:getcontenttype>
                  <D:getetag>
                       zzyzx
                  </D:getetag>
                  <D:getlastmodified>
                       Monday, 12-Jan-98 09:25:56 GMT
                  </D:getlastmodified>

Goland, et al. Standards Track [Page 27] RFC 2518 WEBDAV February 1999

                  <D:resourcetype/>
                  <D:supportedlock>
                       <D:lockentry>
                            <D:lockscope><D:exclusive/></D:lockscope>
                            <D:locktype><D:write/></D:locktype>
                       </D:lockentry>
                       <D:lockentry>
                            <D:lockscope><D:shared/></D:lockscope>
                            <D:locktype><D:write/></D:locktype>
                       </D:lockentry>
                  </D:supportedlock>
             </D:prop>
             <D:status>HTTP/1.1 200 OK</D:status>
        </D:propstat>
   </D:response>
 </D: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 six properties defined
 on it:
 http://www.foo.bar/boxschema/bigbox,
 http://www.foo.bar/boxschema/author, DAV:creationdate,
 DAV:displayname, DAV:resourcetype, and DAV:supportedlock.
 The last four properties are WebDAV-specific, defined in section 13.
 Since GET is not supported on this resource, the get* properties
 (e.g., getcontentlength) 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
 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:
 http://www.foo.bar/boxschema/bigbox (another instance of the "bigbox"
 property type), DAV:creationdate, DAV:displayname,
 DAV:getcontentlength, DAV:getcontenttype, DAV:getetag,
 DAV:getlastmodified, DAV:resourcetype, and DAV:supportedlock.

Goland, et al. Standards Track [Page 28] RFC 2518 WEBDAV February 1999

 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 bytes (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 empty resource type, meaning that it is not
 a collection (resourcetype), and supports both exclusive write and
 shared write locks (supportedlock).

8.1.3 Example - Using propname to Retrieve all Property Names

 >>Request
 PROPFIND  /container/ HTTP/1.1
 Host: www.foo.bar
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <propfind xmlns="DAV:">
   <propname/>
 </propfind>
 >>Response
 HTTP/1.1 207 Multi-Status
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <multistatus xmlns="DAV:">
   <response>
        <href>http://www.foo.bar/container/</href>
        <propstat>
             <prop xmlns:R="http://www.foo.bar/boxschema/">
                  <R:bigbox/>
                  <R:author/>
                  <creationdate/>
                  <displayname/>
                  <resourcetype/>
                  <supportedlock/>
             </prop>
             <status>HTTP/1.1 200 OK</status>
        </propstat>
   </response>
   <response>
        <href>http://www.foo.bar/container/front.html</href>

Goland, et al. Standards Track [Page 29] RFC 2518 WEBDAV February 1999

        <propstat>
             <prop xmlns:R="http://www.foo.bar/boxschema/">
                  <R:bigbox/>
                  <creationdate/>
                  <displayname/>
                  <getcontentlength/>
                  <getcontenttype/>
                  <getetag/>
                  <getlastmodified/>
                  <resourcetype/>
                  <supportedlock/>
             </prop>
             <status>HTTP/1.1 200 OK</status>
        </propstat>
   </response>
 </multistatus>
 In this example, PROPFIND is invoked on the collection resource
 http://www.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 six properties defined on it,
 http://www.foo.bar/boxschema/bigbox,
 http://www.foo.bar/boxschema/author, DAV:creationdate,
 DAV:displayname, DAV:resourcetype, and 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, DAV:creationdate,
 DAV:displayname, DAV:getcontentlength, DAV:getcontenttype,
 DAV:getetag, DAV:getlastmodified, DAV:resourcetype, and
 DAV:supportedlock.
 This example also demonstrates the use of XML namespace scoping, and
 the default namespace.  Since the "xmlns" attribute does not contain
 an explicit "shorthand name" (prefix) letter, the namespace applies
 by default to all enclosed elements.  Hence, all elements which do
 not explicitly state the namespace to which they belong are members
 of the "DAV:" namespace schema.

Goland, et al. Standards Track [Page 30] RFC 2518 WEBDAV February 1999

8.2 PROPPATCH

 The PROPPATCH method processes instructions specified in the request
 body to set and/or remove properties defined on the resource
 identified by the Request-URI.
 All DAV compliant resources MUST support the PROPPATCH method and
 MUST process instructions that are specified using the
 propertyupdate, set, and remove XML elements 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 the
 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 12.13.

8.2.1 Status Codes for use with 207 (Multi-Status)

 The following are examples of response codes one would expect to be
 used in a 207 (Multi-Status) response for this method.  Note,
 however, that unless explicitly prohibited any 2/3/4/5xx series
 response code may be used in a 207 (Multi-Status) response.
 200 (OK) - The 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.
 423 (Locked) - The specified resource is locked and the client either
 is not a lock owner or the lock type requires a lock token to be
 submitted and the client did not submit it.
 507 (Insufficient Storage) - The server did not have sufficient space
 to record the property.

Goland, et al. Standards Track [Page 31] RFC 2518 WEBDAV February 1999

8.2.2 Example - PROPPATCH

 >>Request
 PROPPATCH /bar.html HTTP/1.1
 Host: www.foo.com
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:propertyupdate xmlns:D="DAV:"
 xmlns:Z="http://www.w3.com/standards/z39.50/">
   <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; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:multistatus xmlns:D="DAV:"
 xmlns:Z="http://www.w3.com/standards/z39.50">
   <D:response>
        <D:href>http://www.foo.com/bar.html</D:href>
        <D:propstat>
             <D:prop><Z:Authors/></D:prop>
             <D:status>HTTP/1.1 424 Failed Dependency</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>

Goland, et al. Standards Track [Page 32] RFC 2518 WEBDAV February 1999

 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 424 (Failed Dependency) status
 code for the Authors property indicates this action would have
 succeeded if it were not for the conflict with removing the
 Copyright-Owner property.

8.3 MKCOL Method

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

8.3.1 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, unless
 the Request-URI is "/".  If no such ancestor exists, the method MUST
 fail.  When the MKCOL operation creates a new collection resource,
 all ancestors MUST already exist, or the method MUST fail with a 409
 (Conflict) status code.  For example, if a request to create
 collection /a/b/c/d/ is made, and neither /a/b/ nor /a/b/c/ exists,
 the request must fail.
 When MKCOL is invoked without a request body, the newly created
 collection SHOULD have no members.
 A MKCOL request message may contain a message body.  The 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.

8.3.2 Status Codes

 Responses from a MKCOL request MUST NOT be cached as MKCOL has non-
 idempotent semantics.
 201 (Created) - The collection or structured resource was created in
 its entirety.

Goland, et al. Standards Track [Page 33] RFC 2518 WEBDAV February 1999

 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, or 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.
 415 (Unsupported Media Type)- The server does not support the request
 type of the body.
 507 (Insufficient Storage) - The resource does not have sufficient
 space to record the state of the resource after the execution of this
 method.

8.3.3 Example - MKCOL

 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

8.4 GET, HEAD for Collections

 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" [RFC2068].  GET when
 applied to a collection may return the contents of an "index.html"
 resource, a human-readable view of the contents of the collection, or
 something else altogether. Hence it is possible that the result of a
 GET on a collection will bear no correlation to the membership of the
 collection.
 Similarly, since the definition of HEAD is a GET without a response
 message body, the semantics of HEAD are unmodified when applied to
 collection resources.

Goland, et al. Standards Track [Page 34] RFC 2518 WEBDAV February 1999

8.5 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.

8.6 DELETE

 8.6.1 DELETE for Non-Collection Resources
 If the DELETE method is issued to a non-collection resource whose
 URIs are an internal member of one or more collections, then during
 DELETE processing a server MUST remove any URI for the resource
 identified by the Request-URI from collections which contain it as a
 member.

8.6.2 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 with
 a DELETE on a collection with any value but infinity.
 DELETE instructs that the collection specified in the Request-URI and
 all resources identified by its internal member URIs are to be
 deleted.
 If any resource identified by a member URI cannot be deleted then all
 of the member's ancestors MUST NOT be deleted, so as to maintain
 namespace consistency.
 Any headers included with DELETE MUST be applied in processing every
 resource to be deleted.
 When the DELETE method has completed processing it MUST result in a
 consistent namespace.
 If an error occurs with a resource other than the resource identified
 in the Request-URI then the response MUST be a 207 (Multi-Status).
 424 (Failed Dependency) errors SHOULD NOT be in the 207 (Multi-
 Status).  They can be safely left out because the client will know
 that the ancestors of a resource could not be deleted when the client
 receives an error for the ancestor's progeny.  Additionally 204 (No
 Content) errors SHOULD NOT be returned in the 207 (Multi-Status).
 The reason for this prohibition is that 204 (No Content) is the
 default success code.

Goland, et al. Standards Track [Page 35] RFC 2518 WEBDAV February 1999

8.6.2.1 Example - DELETE

 >>Request
 DELETE  /container/ HTTP/1.1
 Host: www.foo.bar
 >>Response
 HTTP/1.1 207 Multi-Status
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <d:multistatus xmlns:d="DAV:">
   <d:response>
        <d:href>http://www.foo.bar/container/resource3</d:href>
        <d:status>HTTP/1.1 423 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. Thus the
 client knows that the attempt to delete http://www.foo.bar/container/
 must have also failed since the parent can not be deleted unless its
 child has also been deleted.  Even though a Depth header has not been
 included, a depth of infinity is assumed because the method is on a
 collection.

8.7 PUT

8.7.1 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 affected.  For
 example, if a server recognizes the content type of the request body,
 it may be able to automatically extract information that could be
 profitably exposed as properties.
 A PUT that would result in the creation of a resource without an
 appropriately scoped parent collection MUST fail with a 409
 (Conflict).

Goland, et al. Standards Track [Page 36] RFC 2518 WEBDAV February 1999

8.7.2 PUT for Collections

 As defined in the HTTP/1.1 specification [RFC2068], 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.
 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.

8.8 COPY Method

 The COPY method creates a duplicate of the source resource,
 identified by the Request-URI, in the destination resource,
 identified by the URI in the Destination header.  The Destination
 header MUST be present.  The exact behavior of the COPY method
 depends on the type of the source resource.
 All WebDAV compliant resources MUST support the COPY method.
 However, support for the COPY method does not guarantee the ability
 to copy a resource. For example, separate programs may control
 resources on the same server.  As a result, it may not be possible to
 copy a resource to a location that appears to be on the same server.

8.8.1 COPY for HTTP/1.1 resources

 When the source resource is not a collection the result of the COPY
 method is the creation of a new resource at the destination whose
 state and behavior match that of the source resource as closely as
 possible.  After a successful COPY invocation, 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.  Since the environment at the
 destination may be different than at the source due to factors
 outside the scope of control of the server, such as the absence of
 resources required for correct operation, it may not be possible to
 completely duplicate the behavior of the resource at the destination.
 Subsequent alterations to the destination resource will not modify
 the source resource.  Subsequent alterations to the source resource
 will not modify the destination resource.

Goland, et al. Standards Track [Page 37] RFC 2518 WEBDAV February 1999

8.8.2. COPY for Properties

 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
 subject to the effects of the propertybehavior XML element.
 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 12.12.

8.8.3 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" Depth header behaviors.
 A COPY of depth infinity instructs that the collection resource
 identified by the Request-URI is to be copied to the location
 identified by the URI in the Destination header, and all its internal
 member resources are to be copied to a location relative to it,
 recursively through all levels of the collection hierarchy.
 A COPY of "Depth: 0" only instructs that the collection and its
 properties but not resources identified by its internal member URIs,
 are to be copied.
 Any headers included with a COPY MUST be applied in processing every
 resource to be copied with the exception of the Destination header.
 The Destination header only specifies the destination URI for the
 Request-URI. When applied to members of the collection identified by
 the Request-URI the value of Destination is to be modified to reflect
 the current location in the hierarchy.  So, if the Request- URI is
 /a/ with Host header value http://fun.com/ and the Destination is
 http://fun.com/b/ then when http://fun.com/a/c/d is processed it must
 use a Destination of http://fun.com/b/c/d.

Goland, et al. Standards Track [Page 38] RFC 2518 WEBDAV February 1999

 When the COPY method has completed processing it MUST have created a
 consistent namespace at the destination (see section 5.1 for the
 definition of namespace consistency).  However, if an error occurs
 while copying an internal collection, the server MUST NOT copy any
 resources identified by members of this collection (i.e., the server
 must skip this subtree), as this would create an inconsistent
 namespace. After detecting an error, the COPY operation SHOULD try to
 finish as much of the original copy operation as possible (i.e., the
 server should still attempt to copy other subtrees and their members,
 that are not descendents of an error-causing collection).  So, for
 example, if an infinite depth copy operation is performed on
 collection /a/, which contains collections /a/b/ and /a/c/, and an
 error occurs copying /a/b/, an attempt should still be made to copy
 /a/c/. Similarly, after encountering an error copying a non-
 collection resource as part of an infinite depth copy, the server
 SHOULD try to finish as much of the original copy operation as
 possible.
 If an error in executing the COPY method occurs with a resource other
 than the resource identified in the Request-URI then the response
 MUST be a 207 (Multi-Status).
 The 424 (Failed Dependency) status code SHOULD NOT be returned in the
 207 (Multi-Status) response from a COPY method.  These responses can
 be safely omitted because the client will know that the progeny of a
 resource could not be copied when the client receives an error for
 the parent.  Additionally 201 (Created)/204 (No Content) status codes
 SHOULD NOT be returned as values in 207 (Multi-Status) responses from
 COPY methods.  They, too, can be safely omitted because they are the
 default success codes.

8.8.4 COPY and the Overwrite Header

 If a resource exists at the destination and the Overwrite header is
 "T" then prior to performing the copy the server MUST perform a
 DELETE with "Depth: infinity" on the destination resource.  If the
 Overwrite header is set to "F" then the operation will fail.

8.8.5 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.
 403 (Forbidden) _ The source and destination URIs are the same.

Goland, et al. Standards Track [Page 39] RFC 2518 WEBDAV February 1999

 409 (Conflict) _ A resource cannot be created at the destination
 until one or more intermediate collections have been created.
 412 (Precondition Failed) - The server was unable to maintain the
 liveness of the properties listed in the propertybehavior XML element
 or the Overwrite header is "F" and the state of the destination
 resource is non-null.
 423 (Locked) - The destination resource was locked.
 502 (Bad Gateway) - This may occur when the destination is on another
 server and the destination server refuses to accept the resource.
 507 (Insufficient Storage) - The destination resource does not have
 sufficient space to record the state of the resource after the
 execution of this method.

8.8.6 Example - COPY with Overwrite

 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

8.8.7 Example - COPY with No Overwrite

 The following example shows the same copy operation being performed,
 but with the Overwrite header set to "F."  A response of 412
 (Precondition Failed) is returned because the destination 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

Goland, et al. Standards Track [Page 40] RFC 2518 WEBDAV February 1999

 >>Response
 HTTP/1.1 412 Precondition Failed

8.8.8 Example - COPY of a Collection

    >>Request
    COPY /container/ HTTP/1.1
    Host: www.foo.bar
    Destination: http://www.foo.bar/othercontainer/
    Depth: infinity
    Content-Type: text/xml; charset="utf-8"
    Content-Length: xxxx
    <?xml version="1.0" encoding="utf-8" ?>
    <d:propertybehavior xmlns:d="DAV:">
      <d:keepalive>*</d:keepalive>
    </d:propertybehavior>
    >>Response
    HTTP/1.1 207 Multi-Status
    Content-Type: text/xml; charset="utf-8"
    Content-Length: xxxx
    <?xml version="1.0" encoding="utf-8" ?>
    <d:multistatus xmlns:d="DAV:">
      <d:response>
           <d:href>http://www.foo.bar/othercontainer/R2/</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).
 Because there was an error copying R2, none of R2's members were
 copied.  However no errors were listed for those members due to the
 error minimization rules given in section 8.8.3.

Goland, et al. Standards Track [Page 41] RFC 2518 WEBDAV February 1999

8.9 MOVE Method

 The MOVE operation on a non-collection resource is the logical
 equivalent of a copy (COPY), followed by consistency maintenance
 processing, followed by a delete of the source, where all three
 actions are performed atomically.  The consistency maintenance step
 allows the server to perform updates caused by the move, such as
 updating all URIs other than the Request-URI which identify the
 source resource, to point to the new destination resource.
 Consequently, the Destination header MUST be present on all MOVE
 methods and MUST follow all COPY requirements for the COPY part of
 the MOVE method.  All 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 be possible to
 move a resource within a namespace that appears to belong to the same
 server.
 If a resource exists at the destination, the destination resource
 will be DELETEd as a side-effect of the MOVE operation, subject to
 the restrictions of the Overwrite header.

8.9.1 MOVE for Properties

 The behavior of properties on a MOVE, including the effects of the
 propertybehavior XML element, MUST be the same as specified in
 section 8.8.2.

8.9.2 MOVE for Collections

 A MOVE with "Depth: infinity" instructs that the collection
 identified by the Request-URI be moved to the URI specified in the
 Destination header, and all resources identified by its internal
 member URIs are to be moved to locations relative to it, recursively
 through all levels of the collection hierarchy.
 The MOVE method on a collection MUST act as if a "Depth: infinity"
 header was used on it.  A client MUST NOT submit a Depth header on a
 MOVE on a collection with any value but "infinity".
 Any headers included with MOVE MUST be applied in processing every
 resource to be moved with the exception of the Destination header.
 The behavior of the Destination header is the same as given for COPY
 on collections.

Goland, et al. Standards Track [Page 42] RFC 2518 WEBDAV February 1999

 When the MOVE method has completed processing it MUST have created a
 consistent namespace at both the source and destination (see section
 5.1 for the definition of namespace consistency). However, if an
 error occurs while moving an internal collection, the server MUST NOT
 move any resources identified by members of the failed collection
 (i.e., the server must skip the error-causing subtree), as this would
 create an inconsistent namespace. In this case, after detecting the
 error, the move operation SHOULD try to finish as much of the
 original move as possible (i.e., the server should still attempt to
 move other subtrees and the resources identified by their members,
 that are not descendents of an error-causing collection).  So, for
 example, if an infinite depth move is performed on collection /a/,
 which contains collections /a/b/ and /a/c/, and an error occurs
 moving /a/b/, an attempt should still be made to try moving /a/c/.
 Similarly, after encountering an error moving a non-collection
 resource as part of an infinite depth move, the server SHOULD try to
 finish as much of the original move operation as possible.
 If an error occurs with a resource other than the resource identified
 in the Request-URI then the response MUST be a 207 (Multi-Status).
 The 424 (Failed Dependency) status code SHOULD NOT be returned in the
 207 (Multi-Status) response from a MOVE method.  These errors can be
 safely omitted because the client will know that the progeny of a
 resource could not be moved when the client receives an error for the
 parent.  Additionally 201 (Created)/204 (No Content) responses SHOULD
 NOT be returned as values in 207 (Multi-Status) responses from a
 MOVE.  These responses can be safely omitted because they are the
 default success codes.

8.9.3 MOVE and the Overwrite Header

 If a resource exists at the destination and the Overwrite header is
 "T" then prior to performing the move the server MUST perform a
 DELETE with "Depth: infinity" on the destination resource.  If the
 Overwrite header is set to "F" then the operation will fail.

8.9.4 Status Codes

 201 (Created) - The source resource was successfully moved, and a new
 resource was created at the destination.
 204 (No Content) - The source resource was successfully moved to a
 pre-existing destination resource.
 403 (Forbidden) _ The source and destination URIs are the same.

Goland, et al. Standards Track [Page 43] RFC 2518 WEBDAV February 1999

 409 (Conflict) _ A resource cannot be created at the destination
 until one or more intermediate collections have been created.
 412 (Precondition Failed) - The server was unable to maintain the
 liveness of the properties listed in the propertybehavior XML element
 or the Overwrite header is "F" and the state of the destination
 resource is non-null.
 423 (Locked) - The source or the destination resource was locked.
 502 (Bad Gateway) - This may occur when the destination is on another
 server and the destination server refuses to accept the resource.

8.9.5 Example - MOVE of a Non-Collection

 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

8.9.6 Example - MOVE of a Collection

 >>Request
 MOVE /container/ HTTP/1.1
 Host: www.foo.bar
 Destination: http://www.foo.bar/othercontainer/
 Overwrite: F
 If: (<opaquelocktoken:fe184f2e-6eec-41d0-c765-01adc56e6bb4>)
     (<opaquelocktoken:e454f3f3-acdc-452a-56c7-00a5c91e4b77>)
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx

Goland, et al. Standards Track [Page 44] RFC 2518 WEBDAV February 1999

 <?xml version="1.0" encoding="utf-8" ?>
 <d:propertybehavior xmlns:d='DAV:'>
   <d:keepalive>*</d:keepalive>
 </d:propertybehavior>
 >>Response
 HTTP/1.1 207 Multi-Status
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <d:multistatus xmlns:d='DAV:'>
   <d:response>
        <d:href>http://www.foo.bar/othercontainer/C2/</d:href>
        <d:status>HTTP/1.1 423 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.
 Because there was an error copying /container/C2/, none of
 /container/C2's members were copied.  However no errors were listed
 for those members due to the error minimization rules given in
 section 8.8.3.  User agent authentication has previously occurred via
 a mechanism outside the scope of the HTTP protocol, in an underlying
 transport layer.

8.10 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
 method describe only those semantics that are specific to the LOCK
 method and are independent of the access type of the lock being
 requested.
 Any resource which supports the LOCK method MUST, at minimum, support
 the XML request and response formats defined herein.

Goland, et al. Standards Track [Page 45] RFC 2518 WEBDAV February 1999

8.10.1 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.
 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 contain
 the value of the lockdiscovery property in a prop XML element.
 In order to indicate the lock token associated with a newly created
 lock, a Lock-Token response header MUST be included in the response
 for every successful LOCK request for a new lock.  Note that the
 Lock-Token header would not be returned in the response for a
 successful refresh LOCK request because a new lock was not created.

8.10.2 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 MUST also lock 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.

8.10.3 Locking Replicated Resources

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

8.10.4 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 on a LOCK
 method.  All resources that support the LOCK method MUST support the
 Depth header.
 A Depth header of value 0 means to just lock the resource specified
 by the Request-URI.

Goland, et al. Standards Track [Page 46] RFC 2518 WEBDAV February 1999

 If the Depth header is set to infinity then the resource specified in
 the Request-URI along with all its internal members, all the way down
 the hierarchy, are to be locked.  A successful result MUST return a
 single lock token which represents all the resources that have been
 locked.  If an UNLOCK is successfully executed on this token, all
 associated resources are unlocked.  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.
 If no Depth header is submitted on a LOCK request then the request
 MUST act as if a "Depth:infinity" had been submitted.

8.10.5 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.

8.10.6 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. *=It is illegal for a principal to request the same lock
 twice.
 The current lock state of a resource is given in the leftmost column,
 and lock requests are listed in the first row.  The intersection of a
 row and column gives the result of a lock request.  For example, if a
 shared lock is held on a resource, and an exclusive lock is
 requested, the table entry is "false", indicating the lock must not
 be granted.

Goland, et al. Standards Track [Page 47] RFC 2518 WEBDAV February 1999

8.10.7 Status Codes

 200 (OK) - The lock request succeeded and the value of the
 lockdiscovery property is included in the body.
 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.
 423 (Locked) - The resource is locked, so the method has been
 rejected.

8.10.8 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; charset="utf-8"
 Content-Length: xxxx
 Authorization: Digest username="ejw",
    realm="ejw@webdav.sb.aol.com", nonce="...",
    uri="/workspace/webdav/proposal.doc",
    response="...", opaque="..."
 <?xml version="1.0" encoding="utf-8" ?>
 <D:lockinfo xmlns:D='DAV:'>
   <D:lockscope><D:exclusive/></D:lockscope>
   <D:locktype><D:write/></D:locktype>
   <D:owner>
        <D:href>http://www.ics.uci.edu/~ejw/contact.html</D:href>
   </D:owner>
 </D:lockinfo>
 >>Response
 HTTP/1.1 200 OK
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:prop xmlns:D="DAV:">
   <D:lockdiscovery>
        <D:activelock>
             <D:locktype><D:write/></D:locktype>
             <D:lockscope><D:exclusive/></D:lockscope>
             <D:depth>Infinity</D:depth>

Goland, et al. Standards Track [Page 48] RFC 2518 WEBDAV February 1999

             <D:owner>
                  <D:href>
                       http://www.ics.uci.edu/~ejw/contact.html
                  </D:href>
             </D:owner>
             <D:timeout>Second-604800</D:timeout>
             <D:locktoken>
                  <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).
 Note that the nonce, response, and opaque fields have not been
 calculated in the Authorization request header.

8.10.9 Example - Refreshing a Write Lock

 >>Request
 LOCK /workspace/webdav/proposal.doc HTTP/1.1
 Host: webdav.sb.aol.com
 Timeout: Infinite, Second-4100000000
 If: (<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
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:prop xmlns:D="DAV:">
   <D:lockdiscovery>
        <D:activelock>
             <D:locktype><D:write/></D:locktype>

Goland, et al. Standards Track [Page 49] RFC 2518 WEBDAV February 1999

             <D:lockscope><D:exclusive/></D:lockscope>
             <D:depth>Infinity</D:depth>
             <D:owner>
                  <D:href>
                  http://www.ics.uci.edu/~ejw/contact.html
                  </D:href>
             </D:owner>
             <D:timeout>Second-604800</D:timeout>
             <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.

8.10.10 Example - Multi-Resource Lock Request

 >>Request
 LOCK /webdav/ HTTP/1.1
 Host: webdav.sb.aol.com
 Timeout: Infinite, Second-4100000000
 Depth: infinity
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 Authorization: Digest username="ejw",
    realm="ejw@webdav.sb.aol.com", nonce="...",
    uri="/workspace/webdav/proposal.doc",
    response="...", opaque="..."
 <?xml version="1.0" encoding="utf-8" ?>
 <D:lockinfo xmlns:D="DAV:">
   <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

Goland, et al. Standards Track [Page 50] RFC 2518 WEBDAV February 1999

 HTTP/1.1 207 Multi-Status
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:multistatus xmlns:D="DAV:">
   <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:response>
        <D:href>http://webdav.sb.aol.com/webdav/</D:href>
        <D:propstat>
             <D:prop><D:lockdiscovery/></D:prop>
             <D:status>HTTP/1.1 424 Failed Dependency</D:status>
        </D:propstat>
   </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 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.  Note also that the
 lockdiscovery property for the Request-URI has been included as
 required.  In this example the lockdiscovery property is empty which
 means that there are no outstanding locks on the resource.
 In this example, the nonce, response, and opaque fields have not been
 calculated in the Authorization request header.

8.11 UNLOCK Method

 The UNLOCK method removes the lock identified by the lock token in
 the Lock-Token request header from the Request-URI, and all other
 resources included in the lock.  If all resources which have been
 locked under the submitted lock token can not be unlocked then the
 UNLOCK request MUST fail.
 Any DAV compliant resource which supports the LOCK method MUST
 support the UNLOCK method.

Goland, et al. Standards Track [Page 51] RFC 2518 WEBDAV February 1999

8.11.1 Example - UNLOCK

 >>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
 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 (No Content) status code is
 used instead of 200 (OK) because there is no response entity body.
 In this example, the nonce, response, and opaque fields have not been
 calculated in the Authorization request header.

9 HTTP Headers for Distributed Authoring

9.1 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 15 for more details.
 In general, however, support for one compliance class does not entail
 support for any other.

9.2 Depth Header

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

Goland, et al. Standards Track [Page 52] RFC 2518 WEBDAV February 1999

 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.
 Methods which support the Depth header may choose not to support all
 of the header's values and may define, on a case by case basis, the
 behavior of the method if a Depth header is not present. For example,
 the MOVE method only supports "Depth: infinity" and if a Depth header
 is not present will act as if a "Depth: infinity" header had been
 applied.
 Clients MUST NOT rely upon methods executing on members of their
 hierarchies in any particular order or on the execution being atomic
 unless the particular method explicitly provides such guarantees.
 Upon execution, a method with a Depth header will perform as much of
 its assigned task as possible and then return a response specifying
 what it was able to accomplish and what it failed to do.
 So, for example, an attempt to COPY a hierarchy may result in some of
 the members being copied and some not.
 Any headers on a method that has a defined interaction with the Depth
 header MUST be applied to all resources in the scope of the method
 except where alternative behavior is explicitly defined. For example,
 an If-Match header will have its value applied against every resource
 in the method's scope and will cause the method to fail if the header
 fails to match.
 If a resource, source or destination, within the scope of the method
 with a Depth header is locked in such a way as to prevent the
 successful execution of the method, then the lock token for that
 resource MUST be submitted with the request in the If request header.
 The Depth header only specifies the behavior of the method with
 regards to internal children.  If a resource does not have internal
 children then the Depth header MUST be ignored.

Goland, et al. Standards Track [Page 53] RFC 2518 WEBDAV February 1999

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

9.3 Destination Header

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

9.4 If Header

 If = "If" ":" ( 1*No-tag-list | 1*Tagged-list)
 No-tag-list = List
 Tagged-list = Resource 1*List
 Resource = Coded-URL
 List = "(" 1*(["Not"](State-token | "[" entity-tag "]")) ")"
 State-token = Coded-URL
 Coded-URL = "<" absoluteURI ">"
 The If header is intended to have similar functionality to the If-
 Match header defined in section 14.25 of [RFC2068].  However the If
 header is intended for use with any URI which represents state
 information, referred to as a state token, about a resource as well
 as ETags.  A typical example of a state token is a lock token, and
 lock tokens are the only state tokens defined in this specification.
 All DAV compliant resources MUST honor the If header.
 The If header's purpose is to describe a series of state lists.  If
 the state of the resource to which the header is applied does not
 match any of the specified state lists then the request MUST fail
 with a 412 (Precondition Failed).  If one of the described state
 lists matches the state of the resource then the request may succeed.
 Note that the absoluteURI production is defined in [RFC2396].

Goland, et al. Standards Track [Page 54] RFC 2518 WEBDAV February 1999

9.4.1 No-tag-list Production

 The No-tag-list production describes a series of state tokens and
 ETags.  If multiple No-tag-list productions are used then one only
 needs to match the state of the resource for the method to be allowed
 to continue.
 If a method, due to the presence of a Depth or Destination header, is
 applied to multiple resources then the No-tag-list production MUST be
 applied to each resource the method is applied to.

9.4.1.1 Example - No-tag-list If Header

 If: (<locktoken:a-write-lock-token> ["I am an ETag"]) (["I am another
 ETag"])
 The previous header would require that any resources within the scope
 of the method must either be locked with the specified lock token and
 in the state identified by the "I am an ETag" ETag or in the state
 identified by the second ETag "I am another ETag".  To put the matter
 more plainly one can think of the previous If header as being in the
 form (or (and <locktoken:a-write-lock-token> ["I am an ETag"]) (and
 ["I am another ETag"])).

9.4.2 Tagged-list Production

 The tagged-list production scopes a list production.  That is, it
 specifies that the lists following the resource specification only
 apply to the specified resource.  The scope of the resource
 production begins with the list production immediately following the
 resource production and ends with the next resource production, if
 any.
 When the If header is applied to a particular resource, the Tagged-
 list productions MUST be searched to determine if any of the listed
 resources match the operand resource(s) for the current method.  If
 none of the resource productions match the current resource then the
 header MUST be ignored.  If one of the resource productions does
 match the name of the resource under consideration then the list
 productions following the resource production MUST be applied to the
 resource in the manner specified in the previous section.
 The same URI MUST NOT appear more than once in a resource production
 in an If header.

Goland, et al. Standards Track [Page 55] RFC 2518 WEBDAV February 1999

9.4.2.1 Example - Tagged List If header

 COPY /resource1 HTTP/1.1
 Host: www.foo.bar
 Destination: http://www.foo.bar/resource2
 If: <http://www.foo.bar/resource1> (<locktoken:a-write-lock-token>
 [W/"A weak ETag"]) (["strong ETag"])
 <http://www.bar.bar/random>(["another strong ETag"])
 In this example http://www.foo.bar/resource1 is being copied to
 http://www.foo.bar/resource2.  When the method is first applied to
 http://www.foo.bar/resource1, resource1 must be in the state
 specified by "(<locktoken:a-write-lock-token> [W/"A weak ETag"])
 (["strong ETag"])", that is, it either must be locked with a lock
 token of "locktoken:a-write-lock-token" and have a weak entity tag
 W/"A weak ETag" or it must have a strong entity tag "strong ETag".
 That is the only success condition since the resource
 http://www.bar.bar/random never has the method applied to it (the
 only other resource listed in the If header) and
 http://www.foo.bar/resource2 is not listed in the If header.

9.4.3 not Production

 Every state token or ETag is either current, and hence describes the
 state of a resource, or is not current, and does not describe the
 state of a resource. The boolean operation of matching a state token
 or ETag to the current state of a resource thus resolves to a true or
 false value.  The not production is used to reverse that value.  The
 scope of the not production is the state-token or entity-tag
 immediately following it.
 If: (Not <locktoken:write1> <locktoken:write2>)
 When submitted with a request, this If header requires that all
 operand resources must not be locked with locktoken:write1 and must
 be locked with locktoken:write2.

9.4.4 Matching Function

 When performing If header processing, the definition of a matching
 state token or entity tag is as follows.
 Matching entity tag: Where the entity tag matches an entity tag
 associated with that resource.
 Matching state token: Where there is an exact match between the state
 token in the If header and any state token on the resource.

Goland, et al. Standards Track [Page 56] RFC 2518 WEBDAV February 1999

9.4.5 If Header and Non-DAV Compliant Proxies

 Non-DAV compliant proxies will not honor the If header, since they
 will not understand the If header, and HTTP requires non-understood
 headers to be ignored.  When communicating with HTTP/1.1 proxies, the
 "Cache-Control: no-cache" request header MUST be used so as to
 prevent the proxy from improperly trying to service the request from
 its cache.  When dealing with HTTP/1.0 proxies the "Pragma: no-cache"
 request header MUST be used for the same reason.

9.5 Lock-Token Header

 Lock-Token = "Lock-Token" ":" Coded-URL
 The Lock-Token request header is used with the UNLOCK method to
 identify the lock to be removed.  The lock token in the Lock-Token
 request header MUST identify a lock that contains the resource
 identified by Request-URI as a member.
 The Lock-Token response header is used with the LOCK method to
 indicate the lock token created as a result of a successful LOCK
 request to create a new lock.

9.6 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.
 If the overwrite header is not included in a COPY or MOVE request
 then the resource MUST treat the request as if it has an overwrite
 header of value "T". While the Overwrite header appears to duplicate
 the functionality of the If-Match: * header of HTTP/1.1, If-Match
 applies only to the Request-URI, and not to the Destination of a COPY
 or MOVE.
 If a COPY or MOVE is not performed due to the value of the Overwrite
 header, the method MUST fail with a 412 (Precondition Failed) status
 code.
 All DAV compliant resources MUST support the Overwrite header.

9.7 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.

Goland, et al. Standards Track [Page 57] RFC 2518 WEBDAV February 1999

 Status-URI = "Status-URI" ":" *(Status-Code Coded-URL) ; Status-Code
 is defined in 6.1.1 of [RFC2068]
 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.

9.8 Timeout Request Header

 TimeOut = "Timeout" ":" 1#TimeType
 TimeType = ("Second-" DAVTimeOutVal | "Infinite" | Other)
 DAVTimeOutVal = 1*digit
 Other = "Extend" field-value   ; See section 4.2 of [RFC2068]
 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
 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.
 Timeout response values 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 will
 elapse between granting of the lock at the server, and the automatic
 removal of the lock.  The timeout value for TimeType "Second" MUST
 NOT be greater than 2^32-1.
 The timeout counter 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 may be lost.  Specifically, if
 the server wishes to harvest the lock upon time-out, the server
 SHOULD act as if an UNLOCK method was executed by the server on the
 resource using the lock token of the timed-out lock, performed with

Goland, et al. Standards Track [Page 58] RFC 2518 WEBDAV February 1999

 its override authority. Thus logs should be updated with the
 disposition of the lock, notifications should be sent, etc., just as
 they would be for an UNLOCK request.
 Servers are advised to pay close attention to the values submitted by
 clients, as they will be indicative of the type of activity the
 client intends to perform.  For example, an applet running in a
 browser may need to lock a resource, but because of the instability
 of the environment within which the applet is running, the applet may
 be turned off without warning.  As a result, the applet is likely to
 ask for a relatively small timeout value so that if the applet dies,
 the lock can be quickly harvested.  However, a document management
 system is likely to ask for an extremely long timeout because its
 user may be planning on going off-line.
 A client MUST NOT assume that just because the time-out has expired
 the lock has been lost.

10 Status Code Extensions to HTTP/1.1

 The following status codes are added to those defined in HTTP/1.1
 [RFC2068].

10.1 102 Processing

 The 102 (Processing) status code is an interim response used to
 inform the client that the server has accepted the complete request,
 but has not yet completed it.  This status code SHOULD only be sent
 when the server has a reasonable expectation that the request will
 take significant time to complete. As guidance, if a method is taking
 longer than 20 seconds (a reasonable, but arbitrary value) to process
 the server SHOULD return a 102 (Processing) response. The server MUST
 send a final response after the request has been completed.
 Methods can potentially take a long period of time to process,
 especially methods that support the Depth header.  In such cases the
 client may time-out the connection while waiting for a response.  To
 prevent this the server may return a 102 (Processing) status code to
 indicate to the client that the server is still processing the
 method.

10.2 207 Multi-Status

 The 207 (Multi-Status) status code provides status for multiple
 independent operations (see section 11 for more information).

Goland, et al. Standards Track [Page 59] RFC 2518 WEBDAV February 1999

10.3 422 Unprocessable Entity

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

10.4 423 Locked

 The 423 (Locked) status code means the source or destination resource
 of a method is locked.

10.5 424 Failed Dependency

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

10.6 507 Insufficient Storage

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

11 Multi-Status Response

 The default 207 (Multi-Status) response body is a text/xml or
 application/xml HTTP entity that contains a single XML element called
 multistatus, which contains a set of XML elements called response
 which contain 200, 300, 400, and 500 series status codes generated
 during the method invocation.  100 series status codes SHOULD NOT be
 recorded in a response XML element.

Goland, et al. Standards Track [Page 60] RFC 2518 WEBDAV February 1999

12 XML Element Definitions

 In the section below, the final line of each section gives the
 element type declaration using the format defined in [REC-XML]. The
 "Value" field, where present, specifies further restrictions on the
 allowable contents of the XML element using BNF (i.e., to further
 restrict the values of a PCDATA element).

12.1 activelock XML Element

 Name:       activelock
 Namespace:  DAV:
 Purpose:    Describes a lock on a resource.
 <!ELEMENT activelock (lockscope, locktype, depth, owner?, timeout?,
 locktoken?) >

12.1.1 depth XML Element

 Name:       depth
 Namespace:  DAV:
 Purpose:    The value of the Depth header.
 Value:      "0" | "1" | "infinity"
 <!ELEMENT depth (#PCDATA) >

12.1.2 locktoken XML Element

 Name:       locktoken
 Namespace:  DAV:
 Purpose:    The lock token associated with a lock.
 Description: The href contains one or more opaque lock token URIs
 which all refer to the same lock (i.e., the OpaqueLockToken-URI
 production in section 6.4).
 <!ELEMENT locktoken (href+) >

12.1.3 timeout XML Element

 Name:       timeout
 Namespace:  DAV:
 Purpose:    The timeout associated with a lock
 Value:      TimeType ;Defined in section 9.8
 <!ELEMENT timeout (#PCDATA) >

Goland, et al. Standards Track [Page 61] RFC 2518 WEBDAV February 1999

12.2 collection XML Element

 Name:       collection
 Namespace:  DAV:
 Purpose:    Identifies the associated resource as a collection. The
 resourcetype property of a collection resource MUST have this value.
 <!ELEMENT collection EMPTY >

12.3 href XML Element

 Name:       href
 Namespace:  DAV:
 Purpose:    Identifies the content of the element as a URI.
 Value:      URI ; See section 3.2.1 of [RFC2068]
 <!ELEMENT href (#PCDATA)>

12.4 link XML Element

 Name:       link
 Namespace:  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.  The values in the href XML elements inside
 the src and dst XML elements of the link XML element MUST NOT be
 rejected if they point to resources which do not exist.
 <!ELEMENT link (src+, dst+) >

12.4.1 dst XML Element

 Name:       dst
 Namespace:  DAV:
 Purpose:    Indicates the destination of a link
 Value:      URI
 <!ELEMENT dst (#PCDATA) >

12.4.2 src XML Element

 Name:       src
 Namespace:  DAV:
 Purpose:    Indicates the source of a link.

Goland, et al. Standards Track [Page 62] RFC 2518 WEBDAV February 1999

 Value:      URI
 <!ELEMENT src (#PCDATA) >

12.5 lockentry XML Element

 Name:       lockentry
 Namespace:  DAV:
 Purpose:    Defines the types of locks that can be used with the
 resource.
 <!ELEMENT lockentry (lockscope, locktype) >

12.6 lockinfo XML Element

 Name:       lockinfo
 Namespace:  DAV:
 Purpose:    The lockinfo XML element is used with a LOCK method to
 specify the type of lock the client wishes to have created.
 <!ELEMENT lockinfo (lockscope, locktype, owner?) >

12.7 lockscope XML Element

 Name:       lockscope
 Namespace:  DAV:
 Purpose:    Specifies whether a lock is an exclusive lock, or a
 shared lock.
 <!ELEMENT lockscope (exclusive | shared) >

12.7.1 exclusive XML Element

 Name:       exclusive
 Namespace:  DAV:
 Purpose:    Specifies an exclusive lock
 <!ELEMENT exclusive EMPTY >

12.7.2 shared XML Element

 Name:       shared
 Namespace:  DAV:
 Purpose:    Specifies a shared lock
 <!ELEMENT shared EMPTY >

Goland, et al. Standards Track [Page 63] RFC 2518 WEBDAV February 1999

12.8 locktype XML Element

 Name:       locktype
 Namespace:  DAV:
 Purpose:    Specifies the access type of a lock.  At present, this
 specification only defines one lock type, the write lock.
 <!ELEMENT locktype (write) >

12.8.1 write XML Element

 Name:       write
 Namespace:  DAV:
 Purpose:    Specifies a write lock.
 <!ELEMENT write EMPTY >

12.9 multistatus XML Element

 Name:       multistatus
 Namespace:  DAV:
 Purpose:    Contains multiple response messages.
 Description: The responsedescription at the top level is used to
 provide a general message describing the overarching nature of the
 response.  If this value is available an application may use it
 instead of presenting the individual response descriptions contained
 within the responses.
 <!ELEMENT multistatus (response+, responsedescription?) >

12.9.1 response XML Element

 Name:       response
 Namespace:  DAV:
 Purpose:    Holds a single response describing the effect of a
 method on resource and/or its properties.
 Description: A particular href MUST NOT appear more than once as the
 child of a response XML element under a multistatus XML element.
 This requirement is necessary in order to keep processing costs for a
 response to linear time.  Essentially, this prevents having to search
 in order to group together all the responses by href.  There are,
 however, no requirements regarding ordering based on href values.
 <!ELEMENT response (href, ((href*, status)|(propstat+)),
 responsedescription?) >

Goland, et al. Standards Track [Page 64] RFC 2518 WEBDAV February 1999

12.9.1.1 propstat XML Element

 Name:       propstat
 Namespace:  DAV:
 Purpose:    Groups together a prop and status element that is
 associated with a particular href element.
 Description: The propstat XML element MUST contain one prop XML
 element and one status XML element.  The contents of the prop XML
 element MUST only list the names of properties to which the result in
 the status element applies.
 <!ELEMENT propstat (prop, status, responsedescription?) >

12.9.1.2 status XML Element

 Name:       status
 Namespace:  DAV:
 Purpose:    Holds a single HTTP status-line
 Value:      status-line   ;status-line defined in [RFC2068]
 <!ELEMENT status (#PCDATA) >

12.9.2 responsedescription XML Element

 Name:       responsedescription
 Namespace:  DAV:
 Purpose:    Contains a message that can be displayed to the user
 explaining the nature of the response.
 Description: This XML element provides information suitable to be
 presented to a user.
 <!ELEMENT responsedescription (#PCDATA) >

12.10 owner XML Element

 Name:       owner
 Namespace:  DAV:
 Purpose:    Provides information about the principal taking out a
 lock.
 Description: The owner XML element provides information sufficient
 for either directly contacting a principal (such as a telephone
 number or Email URI), or for discovering the principal (such as the
 URL of a homepage) who owns a lock.
 <!ELEMENT owner ANY>

Goland, et al. Standards Track [Page 65] RFC 2518 WEBDAV February 1999

12.11 prop XML element

 Name:       prop
 Namespace:  DAV:
 Purpose:    Contains properties related to a resource.
 Description: The prop XML element is a generic container for
 properties defined on resources.  All elements inside a prop XML
 element MUST define properties related to the resource.  No other
 elements may be used inside of a prop element.
 <!ELEMENT prop ANY>

12.12 propertybehavior XML element

 Name:       propertybehavior Namespace:  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.  All WebDAV compliant resources MUST support the
 propertybehavior XML element.
 <!ELEMENT propertybehavior (omit | keepalive) >

12.12.1 keepalive XML element

 Name:       keepalive
 Namespace:  DAV:
 Purpose:    Specifies requirements for the copying/moving of live
 properties.
 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.  If the requirements specified by the keepalive element
 can not be honored then the method MUST fail with a 412 (Precondition
 Failed).  All DAV compliant resources MUST support the keepalive XML
 element for use with the COPY and MOVE methods.
 Value:      "*" ; #PCDATA value can only be "*"
 <!ELEMENT keepalive (#PCDATA | href+) >

Goland, et al. Standards Track [Page 66] RFC 2518 WEBDAV February 1999

12.12.2 omit XML element

 Name:       omit
 Namespace:  DAV:
 Purpose:    The omit XML element instructs the server that it should
 use best effort to copy properties but a failure to copy a property
 MUST NOT cause the method to fail.  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.  All DAV
 compliant resources MUST support the omit XML element on COPY/MOVE
 methods.
 <!ELEMENT omit EMPTY >

12.13 propertyupdate XML element

 Name:       propertyupdate
 Namespace:  DAV:
 Purpose:    Contains a request to alter the properties on a
 resource.
 Description: This XML element is a container for the information
 required to modify the properties on the resource.  This XML element
 is multi-valued.
 <!ELEMENT propertyupdate (remove | set)+ >

12.13.1 remove XML element

 Name:       remove
 Namespace:  DAV:
 Purpose:    Lists the DAV properties to be removed from a resource.
 Description: Remove instructs that the properties specified in prop
 should be removed.  Specifying the removal of a property that does
 not exist is not an error.  All the XML elements in a prop XML
 element inside of a remove XML element MUST be empty, as only the
 names of properties to be removed are required.
 <!ELEMENT remove (prop) >

12.13.2 set XML element

 Name:       set
 Namespace:  DAV:
 Purpose:    Lists the DAV property values to be set for a resource.

Goland, et al. Standards Track [Page 67] RFC 2518 WEBDAV February 1999

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

12.14 propfind XML Element

 Name:       propfind
 Namespace:  DAV:
 Purpose:    Specifies the properties to be returned from a PROPFIND
 method.  Two special elements are specified for use with propfind,
 allprop and propname.  If prop is used inside propfind it MUST only
 contain property names, not values.
 <!ELEMENT propfind (allprop | propname | prop) >

12.14.1 allprop XML Element

 Name:       allprop Namespace:  DAV:  Purpose:    The allprop XML
 element specifies that all property names and values on the resource
 are to be returned.
 <!ELEMENT allprop EMPTY >

12.14.2 propname XML Element

 Name:       propname Namespace:  DAV:  Purpose:    The propname XML
 element specifies that only a list of property names on the resource
 is to be returned.
 <!ELEMENT propname EMPTY >

13 DAV Properties

 For DAV properties, the name of the property is also the same as the
 name of the XML element that contains its value. In the section
 below, the final line of each section gives the element type
 declaration using the format defined in [REC-XML]. The "Value" field,
 where present, specifies further restrictions on the allowable
 contents of the XML element using BNF (i.e., to further restrict the
 values of a PCDATA element).

Goland, et al. Standards Track [Page 68] RFC 2518 WEBDAV February 1999

13.1 creationdate Property

 Name:       creationdate
 Namespace:  DAV:
 Purpose:    Records the time and date the resource was created.
 Value:      date-time ; See Appendix 2
 Description: The creationdate property should be defined on all DAV
 compliant resources.  If present, it contains a timestamp of the
 moment when the resource was created (i.e., the moment it had non-
 null state).
 <!ELEMENT creationdate (#PCDATA) >

13.2 displayname Property

 Name:       displayname
 Namespace:  DAV:
 Purpose:    Provides a name for the resource that is suitable for
 presentation to a user.
 Description: The displayname property should be defined on all DAV
 compliant resources.  If present, the property contains a description
 of the resource that is suitable for presentation to a user.
 <!ELEMENT displayname (#PCDATA) >

13.3 getcontentlanguage Property

 Name:       getcontentlanguage
 Namespace:  DAV:
 Purpose:    Contains the Content-Language header returned by a GET
 without accept headers
 Description: The getcontentlanguage property MUST be defined on any
 DAV compliant resource that returns the Content-Language header on a
 GET.
 Value:      language-tag   ;language-tag is defined in section 14.13
 of [RFC2068]
 <!ELEMENT getcontentlanguage (#PCDATA) >

13.4 getcontentlength Property

 Name:       getcontentlength
 Namespace:  DAV:
 Purpose:    Contains the Content-Length header returned by a GET
 without accept headers.
 Description: The getcontentlength property MUST be defined on any
 DAV compliant resource that returns the Content-Length header in
 response to a GET.

Goland, et al. Standards Track [Page 69] RFC 2518 WEBDAV February 1999

 Value:      content-length ; see section 14.14 of [RFC2068]
 <!ELEMENT getcontentlength (#PCDATA) >

13.5 getcontenttype Property

 Name:       getcontenttype
 Namespace:  DAV:
 Purpose:    Contains the Content-Type header returned by a GET
 without accept headers.
 Description: This getcontenttype property MUST be defined on any DAV
 compliant resource that returns the Content-Type header in response
 to a GET.
 Value:      media-type   ; defined in section 3.7 of [RFC2068]
 <!ELEMENT getcontenttype (#PCDATA) >

13.6 getetag Property

 Name:       getetag
 Namespace:  DAV:
 Purpose:    Contains the ETag header returned by a GET without
 accept headers.
 Description: The getetag property MUST be defined on any DAV
 compliant resource that returns the Etag header.
 Value:      entity-tag  ; defined in section 3.11 of [RFC2068]
 <!ELEMENT getetag (#PCDATA) >

13.7 getlastmodified Property

 Name:       getlastmodified
 Namespace:  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. The getlastmodified property MUST be defined on any DAV
 compliant resource that returns the Last-Modified header in response
 to a GET.
 Value:      HTTP-date  ; defined in section 3.3.1 of [RFC2068]
 <!ELEMENT getlastmodified (#PCDATA) >

Goland, et al. Standards Track [Page 70] RFC 2518 WEBDAV February 1999

13.8 lockdiscovery Property

 Name:       lockdiscovery
 Namespace:  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.
 <!ELEMENT lockdiscovery (activelock)* >

13.8.1 Example - Retrieving the lockdiscovery Property

 >>Request
 PROPFIND /container/ HTTP/1.1
 Host: www.foo.bar
 Content-Length: xxxx
 Content-Type: text/xml; charset="utf-8"
 <?xml version="1.0" encoding="utf-8" ?>
 <D:propfind xmlns:D='DAV:'>
   <D:prop><D:lockdiscovery/></D:prop>
 </D:propfind>
 >>Response
 HTTP/1.1 207 Multi-Status
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:multistatus xmlns:D='DAV:'>
   <D:response>
        <D:href>http://www.foo.bar/container/</D:href>
        <D:propstat>
             <D:prop>
                  <D:lockdiscovery>
                       <D:activelock>
                            <D:locktype><D:write/></D:locktype>
                            <D:lockscope><D:exclusive/></D:lockscope>
                            <D:depth>0</D:depth>
                            <D:owner>Jane Smith</D:owner>
                            <D:timeout>Infinite</D:timeout>
                            <D:locktoken>

Goland, et al. Standards Track [Page 71] RFC 2518 WEBDAV February 1999

                                 <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.

13.9 resourcetype Property

 Name:       resourcetype
 Namespace:  DAV:
 Purpose:    Specifies the nature of the resource.
 Description: The resourcetype property MUST be defined on all DAV
 compliant resources.  The default value is empty.
 <!ELEMENT resourcetype ANY >

13.10 source Property

 Name:       source
 Namespace:  DAV:
 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.
 <!ELEMENT source (link)* >

13.10.1 Example - A source Property

 <?xml version="1.0" encoding="utf-8" ?>
 <D:prop xmlns:D="DAV:" xmlns:F="http://www.foocorp.com/Project/">
   <D:source>
        <D:link>
             <F:projfiles>Source</F:projfiles>
             <D:src>http://foo.bar/program</D:src>

Goland, et al. Standards Track [Page 72] RFC 2518 WEBDAV February 1999

             <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.

13.11 supportedlock Property

 Name:       supportedlock
 Namespace:  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
 see.
 <!ELEMENT supportedlock (lockentry)* >

13.11.1 Example - Retrieving the supportedlock Property

 >>Request
 PROPFIND  /container/ HTTP/1.1

Goland, et al. Standards Track [Page 73] RFC 2518 WEBDAV February 1999

 Host: www.foo.bar
 Content-Length: xxxx
 Content-Type: text/xml; charset="utf-8"
 <?xml version="1.0" encoding="utf-8" ?>
 <D:propfind xmlns:D="DAV:">
   <D:prop><D:supportedlock/></D:prop>
 </D:propfind>
 >>Response
 HTTP/1.1 207 Multi-Status
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:multistatus xmlns:D="DAV:">
   <D:response>
        <D:href>http://www.foo.bar/container/</D:href>
        <D:propstat>
             <D:prop>
                  <D:supportedlock>
                       <D:lockentry>
                            <D:lockscope><D:exclusive/></D:lockscope>
                            <D:locktype><D:write/></D:locktype>
                       </D:lockentry>
                       <D:lockentry>
                            <D:lockscope><D:shared/></D:lockscope>
                            <D:locktype><D:write/></D:locktype>
                       </D:lockentry>
                  </D:supportedlock>
             </D:prop>
             <D:status>HTTP/1.1 200 OK</D:status>
        </D:propstat>
   </D:response>
 </D:multistatus>

14 Instructions for Processing XML in DAV

 All DAV compliant resources MUST ignore any unknown XML element and
 all its children encountered while processing a DAV method that uses
 XML as its command language.
 This restriction also applies to the processing, by clients, of DAV
 property values where unknown XML elements SHOULD be ignored unless
 the property's schema declares otherwise.

Goland, et al. Standards Track [Page 74] RFC 2518 WEBDAV February 1999

 This restriction does not apply to setting dead DAV properties on the
 server where the server MUST record unknown XML elements.
 Additionally, this restriction does not apply to the use of XML where
 XML happens to be the content type of the entity body, for example,
 when used as the body of a PUT.
 Since XML can be transported as text/xml or application/xml, a DAV
 server MUST accept DAV method requests with XML parameters
 transported as either text/xml or application/xml, and DAV client
 MUST accept XML responses using either text/xml or application/xml.

15 DAV Compliance Classes

 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 [RFC2068].
 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.  Also note that
 identifiers other than numbers may be used as compliance class
 identifiers.

15.1 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.

15.2 Class 2

 A class 2 compliant resource MUST meet all class 1 requirements and
 support the LOCK method, the supportedlock property, the
 lockdiscovery property, the Time-Out response header and the Lock-
 Token request header.  A class "2" compliant resource SHOULD also
 support the Time-Out request header and the owner XML element.
 Class 2 compliant resources MUST return, at minimum, the values "1"
 and "2" in the DAV header on all responses to the OPTIONS method.

Goland, et al. Standards Track [Page 75] RFC 2518 WEBDAV February 1999

16 Internationalization Considerations

 In the realm of internationalization, this specification complies
 with the IETF Character Set Policy [RFC2277]. In this specification,
 human-readable fields can be found either in the value of a property,
 or in an error message returned in a response entity body.  In both
 cases, the human-readable content is encoded using XML, which has
 explicit provisions for character set tagging and encoding, and
 requires that XML processors read XML elements encoded, at minimum,
 using the UTF-8 [UTF-8] encoding of the ISO 10646 multilingual plane.
 XML examples in this specification demonstrate use of the charset
 parameter of the Content-Type header, as defined in [RFC2376], as
 well as the XML "encoding" attribute, which together provide charset
 identification information for MIME and XML processors.
 XML also provides a language tagging capability for specifying the
 language of the contents of a particular XML element.  XML uses
 either IANA registered language tags (see [RFC1766]) or ISO 639
 language tags [ISO-639] in the "xml:lang" attribute of an XML element
 to identify the language of its content and attributes.
 WebDAV applications MUST support the character set tagging, character
 set encoding, and the language tagging functionality of the XML
 specification.  Implementors of WebDAV applications are strongly
 encouraged to read "XML Media Types" [RFC2376] for instruction on
 which MIME media type to use for XML transport, and on use of the
 charset parameter of the Content-Type header.
 Names used within this specification fall into 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

Goland, et al. Standards Track [Page 76] RFC 2518 WEBDAV February 1999

 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., 423 (Locked)).  While the possibility exists that
 a poorly crafted user agent would display this message to a user,
 internationalized applications will ignore this message, and display
 an appropriate message in the user's language and character set.
 Since interoperation of clients and servers does not require locale
 information, this specification does not specify any mechanism for
 transmission of this information.

17 Security Considerations

 This section is provided to detail issues concerning security
 implications of which WebDAV applications need to be aware.
 All of the security considerations of HTTP/1.1 (discussed in
 [RFC2068]) and XML (discussed in [RFC2376]) also apply to WebDAV. In
 addition, the security risks inherent in remote authoring require
 stronger authentication technology, introduce several new privacy
 concerns, and may increase the hazards from poor server design.
 These issues are detailed below.

17.1 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 employing a strong cipher
 suite with mutual authentication of client and server, or a
 connection over a network which is physically secure, for example, an
 isolated network in a building with restricted access.

Goland, et al. Standards Track [Page 77] RFC 2518 WEBDAV February 1999

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

17.2 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.
 WebDAV servers need to be aware of the possibility of a denial of
 service attack at all levels.

17.3 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 that rely only on the
 difficulty of discovering the names of network resources.  Users of
 WebDAV servers are encouraged to use access control techniques to
 prevent unwanted access to resources, rather than depending on the
 relative obscurity of their resource names.

17.4 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

Goland, et al. Standards Track [Page 78] RFC 2518 WEBDAV February 1999

 SHOULD provide control over whether contact information is sent at
 all, and if contact information is sent, control over exactly what
 information is sent.

17.5 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.

17.6 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 URI 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 allowing remote
 authoring of scripts, limiting read and write access to the source
 resources to authorized principals.

17.7 Implications of XML External Entities

 XML supports a facility known as "external entities", defined in
 section 4.2.2 of [REC-XML], which instruct an XML processor to
 retrieve and perform an inline include of XML located at a particular
 URI. An external XML entity can be used to append or modify the
 document type declaration (DTD) associated with an XML document.  An
 external XML entity can also be used to include XML within the
 content of an XML document.  For non-validating XML, such as the XML
 used in this specification, including an external XML entity is not
 required by [REC-XML]. However, [REC-XML] does state that an XML
 processor may, at its discretion, include the external XML entity.
 External XML entities have no inherent trustworthiness and are
 subject to all the attacks that are endemic to any HTTP GET request.
 Furthermore, it is possible for an external XML entity to modify the
 DTD, and hence affect the final form of an XML document, in the worst

Goland, et al. Standards Track [Page 79] RFC 2518 WEBDAV February 1999

 case significantly modifying its semantics, or exposing the XML
 processor to the security risks discussed in [RFC2376].  Therefore,
 implementers must be aware that external XML entities should be
 treated as untrustworthy.
 There is also the scalability risk that would accompany a widely
 deployed application which made use of external XML entities.  In
 this situation, it is possible that there would be significant
 numbers of requests for one external XML entity, potentially
 overloading any server which fields requests for the resource
 containing the external XML entity.

17.8 Risks Connected with Lock Tokens

 This specification, in section 6.4, requires the use of Universal
 Unique Identifiers (UUIDs) for lock tokens, in order to guarantee
 their uniqueness across space and time.  UUIDs, as defined in [ISO-
 11578], contain a "node" field which "consists of the IEEE address,
 usually the host address.  For systems with multiple IEEE 802 nodes,
 any available node address can be used."  Since a WebDAV server will
 issue many locks over its lifetime, the implication is that it will
 also be publicly exposing its IEEE 802 address.
 There are several risks associated with exposure of IEEE 802
 addresses.  Using the IEEE 802 address:
  • It is possible to track the movement of hardware from subnet to

subnet.

  • It may be possible to identify the manufacturer of the hardware

running a WebDAV server.

  • It may be possible to determine the number of each type of computer

running WebDAV.

 Section 6.4.1 of this specification details an alternate mechanism
 for generating the "node" field of a UUID without using an IEEE 802
 address, which alleviates the risks associated with exposure of IEEE
 802 addresses by using an alternate source of uniqueness.

18 IANA Considerations

 This document defines two namespaces, the namespace of property
 names, and the namespace of WebDAV-specific XML elements used within
 property values.

Goland, et al. Standards Track [Page 80] RFC 2518 WEBDAV February 1999

 URIs are used for both names, for several reasons. Assignment of a
 URI 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.  URIs 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 that are understood by all WebDAV applications.  The
 property names and XML elements in this specification are all derived
 from the base URI DAV: by adding a suffix to this URI, for example,
 DAV:creationdate for the "creationdate" property.
 This specification also defines a URI scheme for the encoding of lock
 tokens, the opaquelocktoken URI scheme described in section 6.4.
 To ensure correct interoperation based on this specification, IANA
 must reserve the URI namespaces starting with "DAV:" and with
 "opaquelocktoken:" for use by this specification, its revisions, and
 related WebDAV specifications.

19 Intellectual Property

 The following notice is copied from RFC 2026 [RFC2026], 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
 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.

Goland, et al. Standards Track [Page 81] RFC 2518 WEBDAV February 1999

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, Jim Amsden, Becky Anderson, Alan
 Babich, Sanford Barr, Dylan Barrell, Bernard Chester, Tim Berners-
 Lee, Dan Connolly, Jim Cunningham, Ron Daniel, Jr., Jim Davis, Keith
 Dawson, Mark Day, Brian Deen, Martin Duerst, David Durand, Lee
 Farrell, Chuck Fay, Wesley Felter, Roy Fielding, Mark Fisher, Alan
 Freier, George Florentine, Jim Gettys, Phill Hallam-Baker, Dennis
 Hamilton, Steve Henning, Mead Himelstein, Alex Hopmann, Andre van der
 Hoek, Ben Laurie, Paul Leach, Ora Lassila, Karen MacArthur, Steven
 Martin, Larry Masinter, Michael Mealling, Keith Moore, Thomas Narten,
 Henrik Nielsen, Kenji Ota, Bob Parker, Glenn Peterson, Jon Radoff,
 Saveen Reddy, Henry Sanders, Christopher Seiwald, Judith Slein, Mike
 Spreitzer, Einar Stefferud, Greg Stein, Ralph Swick, Kenji Takahashi,
 Richard N. Taylor, Robert Thau, John Turner, Sankar Virdhagriswaran,
 Fabio Vitali, Gregory Woodhouse, and Lauren Wood.
 Two from this list deserve special mention.  The contributions by
 Larry Masinter have been invaluable, both in helping the formation of
 the working group and in patiently coaching the authors along the
 way.  In so many ways he has set high standards we have toiled to
 meet. The contributions of Judith Slein in clarifying the
 requirements, and in patiently reviewing draft after draft, both
 improved this specification and expanded our minds on document
 management.
 We would also like to thank John Turner for developing the XML DTD.

21 References

21.1 Normative References

 [RFC1766]       Alvestrand, H., "Tags for the Identification of
                 Languages", RFC 1766, March 1995.
 [RFC2277]       Alvestrand, H., "IETF Policy on Character Sets and
                 Languages", BCP 18, RFC 2277, January 1998.
 [RFC2119]       Bradner, S., "Key words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.

Goland, et al. Standards Track [Page 82] RFC 2518 WEBDAV February 1999

 [RFC2396]       Berners-Lee, T., Fielding, R. and L. Masinter,
                 "Uniform Resource Identifiers (URI): Generic Syntax",
                 RFC 2396, August 1998.
 [REC-XML]       T. Bray, J. Paoli, C. M. Sperberg-McQueen,
                 "Extensible Markup Language (XML)." World Wide Web
                 Consortium Recommendation REC-xml-19980210.
                 http://www.w3.org/TR/1998/REC-xml-19980210.
 [REC-XML-NAMES] T. Bray, D. Hollander, A. Layman, "Namespaces in
                 XML". World Wide Web Consortium Recommendation REC-
                 xml-names-19990114.  http://www.w3.org/TR/1999/REC-
                 xml-names-19990114/
 [RFC2069]       Franks, J., Hallam-Baker, P., Hostetler, J., Leach,
                 P, Luotonen, A., Sink, E. and L. Stewart, "An
                 Extension to HTTP :  Digest Access Authentication",
                 RFC 2069, January 1997.
 [RFC2068]       Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and
                 T. Berners-Lee, "Hypertext Transfer Protocol --
                 HTTP/1.1", RFC 2068, 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."
 [ISO-11578]     ISO (International Organization for Standardization).
                 ISO/IEC 11578:1996. "Information technology - Open
                 Systems Interconnection - Remote Procedure Call
                 (RPC)"
 [RFC2141]       Moats, R., "URN Syntax", RFC 2141, May 1997.
 [UTF-8]         Yergeau, F., "UTF-8, a transformation format of
                 Unicode and ISO 10646", RFC 2279, January 1998.

21.2 Informational References

 [RFC2026]  Bradner, S., "The Internet Standards Process - Revision
            3", BCP 9, RFC 2026, October 1996.

Goland, et al. Standards Track [Page 83] RFC 2518 WEBDAV February 1999

 [RFC1807]  Lasher, R. and D. Cohen, "A Format for Bibliographic
            Records", RFC 1807, June 1995.
 [WF]       C. Lagoze, "The Warwick Framework: A Container
            Architecture for Diverse Sets of Metadata", D-Lib
            Magazine, July/August 1996.
            http://www.dlib.org/dlib/july96/lagoze/07lagoze.html
 [USMARC]   Network Development and MARC Standards, Office, ed. 1994.
            "USMARC Format for Bibliographic Data", 1994. Washington,
            DC: Cataloging Distribution Service, Library of Congress.
 [REC-PICS] 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.
 [RFC2291]  Slein, J., Vitali, F., Whitehead, E. and D. Durand,
            "Requirements for Distributed Authoring and Versioning
            Protocol for the World Wide Web", RFC 2291, February 1998.
 [RFC2413]  Weibel, S.,  Kunze, J., Lagoze, C. and M. Wolf, "Dublin
            Core Metadata for Resource Discovery", RFC 2413, September
            1998.
 [RFC2376]  Whitehead, E. and M. Murata, "XML Media Types", RFC 2376,
            July 1998.

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

Goland, et al. Standards Track [Page 84] RFC 2518 WEBDAV February 1999

 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

Goland, et al. Standards Track [Page 85] RFC 2518 WEBDAV February 1999

23 Appendices

23.1 Appendix 1 - WebDAV Document Type Definition

 This section provides a document type definition, following the rules
 in [REC-XML], for the XML elements used in the protocol stream and in
 the values of properties. It collects the element definitions given
 in sections 12 and 13.
 <!DOCTYPE webdav-1.0 [
 <!--============ XML Elements from Section 12 ==================-->
 <!ELEMENT activelock (lockscope, locktype, 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 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, responsedescription?) >
 <!ELEMENT responsedescription (#PCDATA) >

Goland, et al. Standards Track [Page 86] RFC 2518 WEBDAV February 1999

 <!ELEMENT prop ANY >
 <!ELEMENT propertybehavior (omit | keepalive) >
 <!ELEMENT omit EMPTY >
 <!ELEMENT keepalive (#PCDATA | href+) >
 <!ELEMENT propertyupdate (remove | set)+ >
 <!ELEMENT remove (prop) >
 <!ELEMENT set (prop) >
 <!ELEMENT propfind (allprop | propname | prop) >
 <!ELEMENT allprop EMPTY >
 <!ELEMENT propname EMPTY >
 <!ELEMENT collection EMPTY >
 <!--=========== Property Elements from Section 13 ===============-->
 <!ELEMENT creationdate (#PCDATA) >
 <!ELEMENT displayname (#PCDATA) >
 <!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)* >
 ]>

Goland, et al. Standards Track [Page 87] RFC 2518 WEBDAV February 1999

23.2 Appendix 2 - ISO 8601 Date and Time Profile

 The creationdate property specifies the use of the ISO 8601 date
 format [ISO-8601].  This section defines a profile of the ISO 8601
 date format for use with this specification.  This profile is quoted
 from an Internet-Draft by Chris Newman, and is mentioned here to
 properly attribute his work.
 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
 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.

Goland, et al. Standards Track [Page 88] RFC 2518 WEBDAV February 1999

23.3 Appendix 3 - Notes on Processing XML Elements

23.3.1 Notes on Empty XML Elements

 XML supports two mechanisms for indicating that an XML element does
 not have any content.  The first is to declare an XML element of the
 form <A></A>.  The second is to declare an XML element of the form
 <A/>.  The two XML elements are semantically identical.
 It is a violation of the XML specification to use the <A></A> form if
 the associated DTD declares the element to be EMPTY (e.g., <!ELEMENT
 A EMPTY>).  If such a statement is included, then the empty element
 format, <A/> must be used.  If the element is not declared to be
 EMPTY, then either form <A></A> or <A/> may be used for empty
 elements.
 23.3.2 Notes on Illegal XML Processing
 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.

23.3.2.1 Example - XML Syntax Error

 The following request body for a PROPFIND method is illegal.
 <?xml version="1.0" encoding="utf-8" ?>
 <D:propfind xmlns:D="DAV:">
   <D:allprop/>
   <D:propname/>
 </D:propfind>
 The definition of the propfind element only allows for the allprop or
 the propname element, not both.  Thus the above is an error and must
 be responded to with a 400 (Bad Request).

Goland, et al. Standards Track [Page 89] RFC 2518 WEBDAV February 1999

 Imagine, however, that a server wanted to be "kind" and decided to
 pick the allprop element as the true element and respond to it.  A
 client running over a bandwidth limited line who intended to execute
 a propname would be in for a big surprise if the server treated the
 command as an allprop.
 Additionally, if a server were lenient and decided to reply to this
 request, the results would vary randomly from server to server, with
 some servers executing the allprop directive, and others executing
 the propname directive. This reduces interoperability rather than
 increasing it.

23.3.2.2 Example - Unknown XML Element

 The previous example was illegal because it contained two elements
 that were explicitly banned from appearing together in the propfind
 element.  However, XML is an extensible language, so one can imagine
 new elements being defined for use with propfind.  Below is the
 request body of a PROPFIND and, like the previous example, must be
 rejected with a 400 (Bad Request) by a server that does not
 understand the expired-props element.
 <?xml version="1.0" encoding="utf-8" ?>
 <D:propfind xmlns:D="DAV:"
 xmlns:E="http://www.foo.bar/standards/props/">
   <E:expired-props/>
 </D:propfind>
 To understand why a 400 (Bad Request) is returned let us look at the
 request body as the server unfamiliar with expired-props sees it.
 <?xml version="1.0" encoding="utf-8" ?>
 <D:propfind xmlns:D="DAV:"
             xmlns:E="http://www.foo.bar/standards/props/">
 </D:propfind>
 As the server does not understand the expired-props element,
 according to the WebDAV-specific XML processing rules specified in
 section 14, 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" encoding="utf-8" ?>
 <D:propfind xmlns:D="DAV:"
             xmlns:E="http://www.foo.bar/standards/props/">

Goland, et al. Standards Track [Page 90] RFC 2518 WEBDAV February 1999

   <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.

Goland, et al. Standards Track [Page 91] RFC 2518 WEBDAV February 1999

23.4 Appendix 4 – XML Namespaces for WebDAV

23.4.1 Introduction

 All DAV compliant systems MUST support the XML namespace extensions
 as specified in [REC-XML-NAMES].

23.4.2 Meaning of Qualified Names

 [Note to the reader: This section does not appear in [REC-XML-NAMES],
 but is necessary to avoid ambiguity for WebDAV XML processors.]
 WebDAV compliant XML processors MUST interpret a qualified name as a
 URI constructed by appending the LocalPart to the namespace name URI.
 Example
 <del:glider xmlns:del="http://www.del.jensen.org/">
   <del:glidername>
        Johnny Updraft
   </del:glidername>
   <del:glideraccidents/>
 </del:glider>
 In this example, the qualified element name "del:glider" is
 interpreted as the URL "http://www.del.jensen.org/glider".
 <bar:glider xmlns:del="http://www.del.jensen.org/">
   <bar:glidername>
        Johnny Updraft
   </bar:glidername>
   <bar:glideraccidents/>
 </bar:glider>
 Even though this example is syntactically different from the previous
 example, it is semantically identical.  Each instance of the
 namespace name "bar" is replaced with "http://www.del.jensen.org/"
 and then appended to the local name for each element tag.  The
 resulting tag names in this example are exactly the same as for the
 previous example.
 <foo:r xmlns:foo="http://www.del.jensen.org/glide">
   <foo:rname>
        Johnny Updraft
   </foo:rname>
   <foo:raccidents/>
 </foo:r>

Goland, et al. Standards Track [Page 92] RFC 2518 WEBDAV February 1999

 This example is semantically identical to the two previous ones.
 Each instance of the namespace name "foo" is replaced with
 "http://www.del.jensen.org/glide" which is then appended to the local
 name for each element tag, the resulting tag names are identical to
 those in the previous examples.

Goland, et al. Standards Track [Page 93] RFC 2518 WEBDAV February 1999

24. Full Copyright Statement

 Copyright (C) The Internet Society (1999).  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 assigns.
 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.

Goland, et al. Standards Track [Page 94]

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