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Versions: (RFC 2518) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 RFC 4918

                                                   Y. Goland, Microsoft
  Internet Draft                                     E. Whitehead, UCSC
  Document: draft-ietf-webdav-rfc2518bis-01.txt      A. Faizi, Netscape
  Expires: Dec 2002                                   S. Carter, Novell
                                                      D. Jensen, Novell
                                                   L. Dusseault, Xythos


      HTTP Extensions for Distributed Authoring - WebDAV RFC2518 bis


Status of this Memo

   This document is an Internet-Draft and is in full conformance
   with all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.
   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
        http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
        http://www.ietf.org/shadow.html.

   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].

Abstract

   WebDAV consists of a set of methods, headers, and content-types
   ancillary to HTTP/1.1 for the management of resource properties,
   creation and management of resource collections, namespace
   manipulation, and resource locking (collision avoidance).

   RFC2518 was published in February 1998, and this draft makes only
   minor revisions mostly due to interoperability experience.


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Table of Contents

  1  Introduction...................................................6
  2  Notational Conventions.........................................7
  3  Terminology....................................................8
  4  Data Model for Resource Properties.............................8
  4.1  The Resource Property Model..................................8
  4.2  Existing Metadata Proposals..................................9
  4.3  Properties and HTTP Headers..................................9
  4.4  Property Values.............................................10
  4.5  Property Names..............................................10
  4.6  Media Independent Links.....................................11
  5  Collections of Web Resources..................................11
  5.1  HTTP URL Namespace Model....................................11
  5.2  Collection Resources........................................12
  5.3  Source Resources and Output Resources.......................13
  6  Locking.......................................................14
  6.1  Exclusive Vs. Shared Locks..................................14
  6.2  Required Support............................................15
  6.3  Lock Tokens.................................................16
  6.4  opaquelocktoken Lock Token URI Scheme.......................16
  6.5  Lock Capability Discovery...................................17
  6.6  Active Lock Discovery.......................................17
  6.7  Usage Considerations........................................17
  7  Write Lock....................................................18
  7.1  Methods Restricted by Write Locks...........................18
  7.2  Write Locks and Lock Tokens.................................18
  7.3  Write Locks and Properties..................................19
  7.4  Write Locks and Unmapped URLs...............................19
  7.5  Write Locks and Collections.................................20
  7.6  Write Locks and the If Request Header.......................20
  7.6.1 Example - Write Lock........................................21
  7.7  Write Locks and COPY/MOVE...................................21
  7.8  Refreshing Write Locks......................................22
  8  HTTP Methods for Distributed Authoring........................22
  8.1  PROPFIND....................................................23
  8.1.1 Example - Retrieving Named Properties.......................24
  8.1.2 Example - Using propname to Retrieve all Property Names.....25
  8.2  PROPPATCH...................................................27
  8.2.1 Status Codes for use with 207 (Multi-Status)................27
  8.2.2 Example - PROPPATCH.........................................28
  8.3  MKCOL Method................................................29
  8.3.1 Request.....................................................29
  8.3.2 Status Codes................................................29
  8.3.3 Example - MKCOL.............................................30
  8.4  GET, HEAD for Collections...................................30
  8.5  POST for Collections........................................31

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  8.6  DELETE......................................................31
  8.6.1 DELETE for Non-Collection Resources.........................31
  8.6.2 DELETE for Collections......................................31
  8.7  PUT.........................................................32
  8.7.1 PUT for Non-Collection Resources............................32
  8.7.2 PUT for Collections.........................................33
  8.8  COPY Method.................................................33
  8.8.1 COPY for HTTP/1.1 resources.................................33
  8.8.2 COPY for Properties.........................................33
  8.8.3 COPY for Collections........................................34
  8.8.4 COPY and the Overwrite Header...............................35
  8.8.5 Status Codes................................................35
  8.8.6 Example - COPY with Overwrite...............................36
  8.8.7 Example - COPY with No Overwrite............................36
  8.8.8 Example - COPY of a Collection..............................36
  8.9  MOVE Method.................................................37
  8.9.1 MOVE for Properties.........................................38
  8.9.2 MOVE for Collections........................................38
  8.9.3 MOVE and the Overwrite Header...............................39
  8.9.4 Status Codes................................................39
  8.9.5 Example - MOVE of a Non-Collection..........................39
  8.9.6 Example - MOVE of a Collection..............................40
  8.10  LOCK Method................................................41
  8.10.1 Operation..................................................41
  8.10.2 The Effect of Locks on Properties and Collections..........41
  8.10.3 Locking Replicated Resources...............................42
  8.10.4 Depth and Locking..........................................42
  8.10.5 Interaction with other Methods.............................42
  8.10.6 Lock Compatibility Table...................................42
  8.10.7 Status Codes...............................................43
  8.10.8 Example - Simple Lock Request..............................43
  8.10.9 Example - Refreshing a Write Lock..........................44
  8.10.10 Example - Multi-Resource Lock Request.....................45
  8.11  UNLOCK Method..............................................47
  8.11.1 Example - UNLOCK...........................................47
  9  HTTP Headers for Distributed Authoring........................47
  9.1  DAV Header..................................................48
  9.2  Depth Header................................................48
  9.3  Destination Header..........................................49
  9.4  If Header...................................................49
  9.4.1 No-tag-list Production......................................50
  9.4.2 Tagged-list Production......................................50
  9.4.3 not Production..............................................51
  9.4.4 Matching Function...........................................51
  9.4.5 If Header and Non-DAV Compliant Proxies.....................52
  9.5  Lock-Token Header...........................................52
  9.6  Overwrite Header............................................52

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  9.7  Status-URI Response Header..................................53
  9.8  Timeout Request Header......................................53
  10 Status Code Extensions to HTTP/1.1............................54
  10.1  102 Processing.............................................54
  10.2  207 Multi-Status...........................................54
  10.3  422 Unprocessable Entity...................................55
  10.4  423 Locked.................................................55
  10.5  424 Failed Dependency......................................55
  10.6  507 Insufficient Storage...................................55
  11 Multi-Status Response.........................................55
  12 XML Element Definitions.......................................56
  12.1  activelock XML Element.....................................56
  12.1.1 depth XML Element..........................................56
  12.1.2 locktoken XML Element......................................56
  12.1.3 timeout XML Element........................................56
  12.2  collection XML Element.....................................57
  12.3  href XML Element...........................................57
  12.4  link XML Element...........................................57
  12.4.1 dst XML Element............................................57
  12.4.2 src XML Element............................................58
  12.5  lockentry XML Element......................................58
  12.6  lockinfo XML Element.......................................58
  12.7  lockscope XML Element......................................58
  12.7.1 exclusive XML Element......................................59
  12.7.2 shared XML Element.........................................59
  12.8  locktype XML Element.......................................59
  12.8.1 write XML Element..........................................59
  12.9  multistatus XML Element....................................59
  12.9.1 response XML Element.......................................60
  12.9.2 responsedescription XML Element............................60
  12.10 owner XML Element..........................................61
  12.11 prop XML element...........................................61
  12.12 propertyupdate XML element.................................61
  12.12.1 remove XML element........................................62
  12.12.2 set XML element...........................................62
  12.13 propfind XML Element.......................................62
  12.13.1 allprop XML Element.......................................62
  12.13.2 propname XML Element......................................63
  13 DAV Properties................................................64
  13.1  creationdate Property......................................64
  13.2  displayname Property.......................................64
  13.3  getcontentlanguage Property................................64
  13.4  getcontentlength Property..................................65
  13.5  getcontenttype Property....................................65
  13.6  getetag Property...........................................65
  13.7  getlastmodified Property...................................66
  13.8  lockdiscovery Property.....................................66

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  13.8.1 Example - Retrieving the lockdiscovery Property............66
  13.9  resourcetype Property......................................67
  13.10 source Property............................................68
  13.10.1 Example - A source Property...............................68
  13.11 supportedlock Property.....................................69
  13.11.1 Example - Retrieving the supportedlock Property...........69
  14 Instructions for Processing XML in DAV........................70
  15 DAV Compliance Classes........................................71
  15.1  Class 1....................................................71
  15.2  Class 2....................................................71
  16 Internationalization Considerations...........................71
  17 Security Considerations.......................................73
  17.1  Authentication of Clients..................................73
  17.2  Denial of Service..........................................73
  17.3  Security through Obscurity.................................74
  17.4  Privacy Issues Connected to Locks..........................74
  17.5  Privacy Issues Connected to Properties.....................74
  17.6  Reduction of Security due to Source Link...................75
  17.7  Implications of XML External Entities......................75
  17.8  Risks Connected with Lock Tokens...........................75
  18 IANA Considerations...........................................76
  19 Intellectual Property.........................................77
  20 Acknowledgements..............................................77
  21 References....................................................79
  21.1  Normative References.......................................79
  21.2  Informational References...................................80
  22 Authors' Addresses............................................82
  23 Appendices....................................................83
  23.1  Appendix 1 - WebDAV Document Type Definition...............83
  23.2  Appendix 2 - ISO 8601 Date and Time Profile................84
  23.3  Appendix 3 - Notes on Processing XML Elements..............85
  23.3.1 Notes on Empty XML Elements................................85
  23.3.2 Notes on Illegal XML Processing............................85
  23.4  Appendix 4: Node Field Generation Without the IEEE 802 Address
       87
  24 Full Copyright Statement......................................88

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1 Introduction

  This document describes an extension to the HTTP/1.1 protocol that
  allows clients to perform remote web content authoring operations.
  This extension provides a coherent set of methods, headers, request
  entity body formats, and response entity body formats that provide
  operations for:

  Properties: The ability to create, remove, and query information
  about Web pages, such as their authors, creation dates, etc. Also,
  the ability to link pages of any media type to related pages.

  Collections: The ability to create sets of documents and to retrieve
  a hierarchical membership listing (like a directory listing in a
  file system).

  Locking: The ability to keep more than one person from working on a
  document at the same time. This prevents the "lost update problem",
  in which modifications are lost as first one author then another
  writes changes without merging the other author's changes.

  Namespace Operations: The ability to instruct the server to copy and
  move Web resources.

  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].

  This standard does not specify the versioning operations suggested
  by [RFC2291]. That work was done in a separate document, "Versioning
  Extensions to WebDAV" [RFC3253].

  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.

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  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. A
  DTD is provided in Appendix 1.  However, legal XML may not be valid
  according to this DTD, because unknown XML elements may appear in
  WebDAV syntax without making the syntax illegal.

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

  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 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].

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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.

  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.


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  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
  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

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  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,
  using the "xml:lang" attribute (in the case of WebDAV properties,
  this attribute is placed on the æpropÆ element), handles cases where
  the same character set is employed by multiple human languages.

  Other XML attributes in property values are significant.  The server
  MUST persistently store the XML attribute information stored on XML
  elements contained by the XML element whose name is the name of the
  property.  Attributes on the property name element SHOULD be
  persistently stored and restored in PROPFIND responses (other than
  the "xml:lang" and namespace attributes which MUST be stored).  The
  XML attribute xml:space MUST not be used to change white space
  handling.

  White space in property values is significant.

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

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  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 Error! Reference source
  not found., 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.


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.


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  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.

  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

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  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.

  Clients MUST be able to support the case where WebDAV resources are
  contained inside non-WebDAV resources.  For example, if a OPTIONS
  response from "http://foo.bar/servlet/dav/collection" indicates
  WebDAV support, the client cannot assume that
  "http://foo.bar/servlet/dav/" or its parent necessarily are WebDAV
  collections.

5.3 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.

  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

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                     WebDAV (RFC2518) bis             June 2002

  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.

  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

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                     WebDAV (RFC2518) bis             June 2002

  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.

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.


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                     WebDAV (RFC2518) bis             June 2002

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.

  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]

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                     WebDAV (RFC2518) bis             June 2002


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

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                     WebDAV (RFC2518) bis             June 2002

  of which rely on reservations and merging rather than on locking.
  Finally, being stateless, it cannot enforce a sequence of operations
  like LOCK / GET / PUT / UNLOCK.

  WebDAV servers that support locking can reduce the likelihood that
  clients will accidentally overwrite each other's changes by
  requiring clients to lock resources before modifying them.  Such
  servers would effectively prevent HTTP 1.0 and HTTP 1.1 clients from
  modifying resources.

  WebDAV clients can be good citizens by using a lock / retrieve /
  write /unlock sequence of operations (at least by default) whenever
  they interact with a WebDAV server that supports locking.

  HTTP 1.1 clients can be good citizens, avoiding overwriting other
  clients' changes, by using entity tags in If-Match headers with any
  requests that would modify resources.

  Information managers may attempt to prevent overwrites by
  implementing client-side procedures requiring locking before
  modifying WebDAV resources.


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.


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                     WebDAV (RFC2518) bis             June 2002

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

7.4 Write Locks and Unmapped URLs

  It is possible to lock an unmapped URL in order to lock the name for
  use.  This is a simple way to avoid the lost-update problem on the
  creation of a new resource (another way is to use If-None-Match
  header specified in HTTP 1.1).  It has the side benefit of locking
  the new resource immediately for use of the creator.

  The lost-update problem is not an issue for collections because
  MKCOL can only be used to create a collection, not to overwrite an
  existing collection.  In order to immediately lock a collection upon
  creation, clients may attempt to pipeline the MKCOL and LOCK
  requests together.

  A lock request to an unmapped URL should result in the creation of a
  resource that is locked.  A subsequent PUT request with the correct
  lock token should normally succeed, and provides the content,
  content-type, content-language and other information as appropriate.

  In this situation, WebDAV servers compliant with RFC2518 MAY create
  "lock-null" resources which are special and unusual resources.  A
  lock-null resource:

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

  However, interoperability and compliance problems have been found
  with lock-null resources.  Therefore, they are deprecated.  WebDAV
  servers compliant with this document SHOULD create regular locked
  empty resources, which behave in every way as if they were a normal
  resource.  A locked empty resource:

  -    Can be downloaded, deleted, moved, copied, and in all ways behave
     as a regular resource, not a lock-null resource.

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                     WebDAV (RFC2518) bis             June 2002

  -    Appears as a member of its parent collection.
  -    SHOULD NOT disappear when its lock goes away (clients must
     therefore be responsible for cleaning up their own mess, as with
     any other operation)
  -    SHOULD default to a content-type of "application/octet-stream".
  -    SHOULD default to reasonable, or reasonably blank, values for
     other properties like getcontentlanguage.
  -    May have content added with a PUT request.  MUST be able to change
     content type.
  -    MUST NOT be turned into a collection.  A MKCOL request must fail
     as it would to any existing resource.
  -    MUST have defined values for lockdiscovery and supportedlock
     properties.
  -    The response MUST indicate that a resource was created, by use of
     the "201 Created" response code (a LOCK request to an existing
     resource instead will result in 200 OK).  The body must still
     include the lockdiscovery property, as with a LOCK request to an
     existing resource.

  Clients can easily interoperate with either kind of server (both
  exist) by only attempting PUT after a LOCK to an unmapped URL, not
  MKCOL or GET.

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 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


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                     WebDAV (RFC2518) bis             June 2002

  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 AÆs 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.

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

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                     WebDAV (RFC2518) bis             June 2002

  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
                                                                  Comment                                                                       :                                                                                                                                                If a resource has   in section 7.5. For example, if the MOVE makes the resource a child      a "move lock" on it (a new   of a collection that is locked with "Depth: infinity", then the         type I just made up) then   resource will be added to that collection's lock. Additionally, if a     the MOVE should fail JUST                                                                   because it is locked.   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 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.


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                     WebDAV (RFC2518) bis             June 2002

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 Error! Reference source not found.) 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 resourceÆs 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.

  Clients MUST not send allprop requests in any form (either the empty
  body PROPFIND or the specific allprop element), because allprop is
  being removed. WebDAV servers increasingly have expensively-
  calculated or lengthy properties (see [RFC3253] and [TODO: ref ACL
  RFC when available]) and do not return all properties already.
  Instead, WebDAV clients can use propname requests to discover what
  properties exist, and request named properties when retrieving
  values.  A WebDAV server MAY omit certain live properties from other
  specifications when responding to an allprop request from an older
  client, and MAY return only custom (dead) properties and those
  defined in this specification.

  All servers MUST support returning a response of content type
  text/xml or application/xml that contains a multistatus XML element
  that describes the results of the attempts to retrieve the various
  properties.

  If there is an error retrieving a property then a proper error
  result MUST be included in the response.  A request to retrieve the
  value of a property which does not exist is an error and MUST be
  noted, if the response uses a multistatus XML element, with a
  response XML element which contains a 404 (Not Found) status value.

  Consequently, the multistatus XML element for a collection resource
  with member 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

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                     WebDAV (RFC2518) bis             June 2002

  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.

  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 xmlns:R="http://www.foo.bar/boxschema/">
      <D:href>http://www.foo.bar/file</D:href>
      <D:propstat>
       <D:prop>
        <R:bigbox>
         <R:BoxType>Box type A</R:BoxType>
        </R:bigbox>
        <R:author>
         <R:Name>J.J. Johnson</R:Name>
        </R:author>
       </D:prop>

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                     WebDAV (RFC2518) bis             June 2002

       <D:status>HTTP/1.1 200 OK</D:status>
      </D:propstat>
      <D:propstat>
       <D:prop><R:DingALing/><R:Random/></D:prop>
       <D:status>HTTP/1.1 403 Forbidden</D:status>
       <D:responsedescription> The user does not have access to the
    DingALing property.
       </D:responsedescription>
      </D:propstat>
     </D:response>
     <D:responsedescription> There has been an access violation error.
     </D:responsedescription>
    </D:multistatus>

  In this example, PROPFIND is executed on 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 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/>

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                     WebDAV (RFC2518) bis             June 2002

        <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>
      <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.


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  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.

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 Error! Reference source not found..

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.


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                     WebDAV (RFC2518) bis             June 2002

  507 (Insufficient Storage) - The server did not have sufficient
  space to record the property.

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>

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                     WebDAV (RFC2518) bis             June 2002

      <D:responsedescription> Copyright Owner can not be deleted or
    altered.</D:responsedescription>
     </D:response>
    </D:multistatus>

  In this example, the client requests the server to set the value of
  the "Authors" property in the "http://www.w3.com/standards/z39.50/"
  namespace, and to remove the property "Copyright-Owner" in the
  "http://www.w3.com/standards/z39.50/" namespace.  Since the
  Copyright-Owner property could not be removed, no property
  modifications occur.  The 424 (Failed Dependency) status code for
  the Authors property indicates this action would have succeeded if
  it were not for the conflict with removing the Copyright-Owner
  property.

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.

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                     WebDAV (RFC2518) bis             June 2002


  201 (Created) - The collection or structured resource was created in
  its entirety.

  403 (Forbidden) - This indicates at least one of two conditions: 1)
  the server does not allow the creation of collections at the given
  location in its namespace, 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.


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                     WebDAV (RFC2518) bis             June 2002

  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.

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.

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                     WebDAV (RFC2518) bis             June 2002

  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.

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).

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                     WebDAV (RFC2518) bis             June 2002


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.

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.

8.8.2     COPY for Properties

  Live properties described in this document SHOULD be duplicated as
  identically behaving live properties at the destination resource.
  If a property cannot be copied live, then its value MUST be

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                     WebDAV (RFC2518) bis             June 2002

  duplicated, octet-for-octet, in an identically named, dead property
  on the destination resource.

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.

  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.


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  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.

  207 (Multi-Status) - Multiple resources were to be affected by the
  COPY, but errors on some of them prevented the operation from taking
  place.  Specific error messages, together with the most appropriate
  of the source and destination URLs, appear in the body of the multi-
  status response. E.g. if a destination resource was locked and could
  not be overwritten, then the destination resource URL appears with
  the 423 (Locked) status.

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

  409 (Conflict) û A resource cannot be created at the destination
  until one or more intermediate collections have been created.

  412 (Precondition Failed) û A precondition failed, e.g. 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.


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                     WebDAV (RFC2518) bis             June 2002

  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

  >>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/

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                     WebDAV (RFC2518) bis             June 2002

    Depth: infinity

  >>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/1.1 423 Locked</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 because the destination R2 is locked.  Because there was an
  error copying R2, none of R2's members were copied.  However no
  errors were listed for those members due to the error minimization
  rules given in section 8.8.3.

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.


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8.9.1     MOVE for Properties

  The behavior of properties on a MOVE 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.

  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)

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  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.

  207 (Multi-Status) - Multiple resources were to be affected by the
  MOVE, but errors on some of them prevented the operation from taking
  place.  Specific error messages, together with the most appropriate
  of the source and destination URLs, appear in the body of the multi-
  status response. E.g. if a source resource was locked and could not
  be moved, then the source resource URL appears with the 423 (Locked)
  status.

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

  409 (Conflict) û A resource cannot be created at the destination
  until one or more intermediate collections have been created.

  412 (Precondition Failed) û A condition failed, e.g. 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).

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  >>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>)


  >>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

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                     WebDAV (RFC2518) bis             June 2002

  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.

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 server MUST preserve
  the information provided by the client in the owner field when the
  lock information is requested.  The LOCK request may have a Timeout
  header.

  Clients MUST assume that locks may arbitrarily disappear at any
  time, regardless of the value given in the Timeout header.  The
  Timeout header only indicates the behavior of the server if
  "extraordinary" circumstances do not occur.  For example, a
  sufficiently privileged user may remove a lock at any time or the
  system may crash in such a way that it loses the record of the
  lock's existence. 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.


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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.

  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       EXCLUSIVE
     LOCK REQUEST             LOCK         LOCK
     None                    True         True
     Shared Lock              True         False
     Exclusive Lock           False        False*


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  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.

8.10.7      Status Codes

  200 (OK) - The lock request succeeded and the value of the
  lockdiscovery property is included in the body.

  409 (Conflict) û A resource cannot be created at the destination
  until one or more intermediate collections have been created.

  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>

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  >>Response

    HTTP/1.1 200 OK
    Lock-Token: <opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4>
    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>
       <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.

  Note that the locktoken href element would not contain any
  whitespace.  The line return appearing in this document is only for
  formatting.

8.10.9      Example - Refreshing a Write Lock

  >>Request

    LOCK /workspace/webdav/proposal.doc HTTP/1.1

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    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>
       <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

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    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

    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

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  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.

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


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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 Error! Reference
  source not found. 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")

  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.


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

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

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

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

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.

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  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].

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

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  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.

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.


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  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.

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.

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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.

  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 NOT 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.


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  If the timeout expires then the lock may be lost.  Specifically, if
  the server wishes to harvest the lock upon time-out, the server
  SHOULD act as if an UNLOCK method was executed by the server on the
  resource using the lock token of the timed-out lock, performed with
  its override authority. Thus logs should be updated with the
  disposition of the lock, notifications should be sent, etc., just as
  they would be for an UNLOCK request.

  Servers are advised to pay close attention to the values submitted
  by clients, as they will be indicative of the type of activity the
  client intends to perform.  For example, an applet running in a
  browser may need to lock a resource, but because of the instability
  of the environment within which the applet is running, the applet
  may be turned off without warning.  As a result, the applet is
  likely to ask for a relatively small timeout value so that if the
  applet dies, the lock can be quickly harvested.  However, a document
  management system is likely to ask for an extremely long timeout
  because its user may be planning on going off-line.

  A client MUST NOT assume that just because the time-out has expired
  the lock has been lost.


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


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  The 207 (Multi-Status) status code provides status for multiple
  independent operations (see section Error! Reference source not
  found. for more information).

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.

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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

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  Value:  TimeType ;Defined in section 23.2.

  <!ELEMENT timeout (#PCDATA) >

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

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  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.
  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) >


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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 >

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.

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  <!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?) >

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

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  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>

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  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)+ >


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12.12.1       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) >

12.12.2       set XML element

  Name:   set
  Namespace:  DAV:
  Purpose: Lists the DAV property values to be set for a resource.
  Description:       The set XML element MUST contain only a prop
          XML element.  The elements contained by the prop XML
          element inside the set XML element MUST specify the name
          and value of properties that are set on the resource
          identified by Request-URI.  If a property already exists
          then its value is replaced. Language tagging information 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) >

12.13  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) >

12.13.1       allprop XML Element


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  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 >

12.13.2       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 >


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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).

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).  This property is
          live and protected.

  <!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. This property is live and MAY be
          protected.

  <!ELEMENT displayname (#PCDATA) >

13.3   getcontentlanguage Property

  Name:   getcontentlanguage
  Namespace:  DAV:
  Purpose: Contains the Content-Language header returned by a GET
          without accept headers

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  Description:       The getcontentlanguage property MUST be defined
          on any DAV compliant resource that returns the Content-
          Language header on a GET.  This property is live and MAY be
          protected.
  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.  This property is live
          and protected.
  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. This property is live and MAY
          be protected.
  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.

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  Description:       The getetag property MUST be defined on any DAV
          compliant resource that returns the Etag header.  This
          property is live and protected.
  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. This
          property is live and protected.
  Value:  HTTP-date  ; defined in section 3.3.1 of [RFC2068]

  <!ELEMENT getlastmodified (#PCDATA) >

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.  This
          property is live and protected.

  <!ELEMENT lockdiscovery (activelock)* >

13.8.1      Example - Retrieving the lockdiscovery Property

  >>Request

    PROPFIND /container/ HTTP/1.1

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    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>
          <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:

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  Purpose: Specifies the nature of the resource.
  Description:       The resourcetype property MUST be defined on
          all DAV compliant resources.  The default value is empty.
          This property is live and protected.

  <!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 linkÆs 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. This property is live and MAY be protected.

  <!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>
       <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>

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  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.
          This property is live and protected.

  <!ELEMENT supportedlock (lockentry)* >

13.11.1       Example - Retrieving the supportedlock 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:supportedlock/></D:prop>
    </D:propfind>

  >>Response

    HTTP/1.1 207 Multi-Status
    Content-Type: text/xml; charset="utf-8"

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    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.

  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.


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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.


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

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  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 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.



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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.

  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.

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  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
  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.


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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 include additional XML. An external XML entity can be
  used to append or modify the document type declaration (DTD)
  associated with an XML document.  An external XML entity can also be
  used to include XML within the content of an XML document.  For non-
  validating XML, such as the XML used in this specification,
  including an external XML entity is not required by [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 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,

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  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 23.4 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.

  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.


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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.

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

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  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.


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21 References

21.1   Normative References

  [RFC1766]   H. T. Alvestrand, "Tags for the Identification of
        Languages." RFC 1766. Uninett. March, 1995.

  [RFC2277]   H. T. Alvestrand, "IETF Policy on Character Sets and
        Languages." RFC 2277, BCP 18. Uninett. January, 1998.

  [RFC2119]   S. Bradner, "Key words for use in RFCs to Indicate
        Requirement Levels."  RFC 2119, BCP 14. Harvard University.
        March, 1997.

  [RFC2396]   T. Berners-Lee, R. Fielding, L. Masinter, "Uniform
        Resource Identifiers (URI): Generic Syntax." RFC 2396.
        MIT/LCS, U.C. Irvine, Xerox. 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, "Name Spaces in
        XML" World Wide Web Consortium Recommendation REC-xml-names.
        http://www.w3.org/TR/REC-xml-names-19990114/

  [RFC2069]   J. Franks, P. Hallam-Baker, J. Hostetler, P. Leach, A.
        Luotonen, E. Sink, and L. Stewart. "An Extension to HTTP :
        Digest Access Authentication" RFC 2069. Northwestern
        University, CERN, Spyglass Inc., Microsoft Corp., Netscape
        Communications Corp., Spyglass Inc., Open Market Inc. January
        1997.

  [RFC2068]   R. Fielding, J. Gettys, J. Mogul, H. Frystyk, T.
        Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1." RFC
        2068. U.C. Irvine, DEC, MIT/LCS. January, 1997.

  [ISO-639]   ISO (International Organization for Standardization).
        ISO 639:1988. "Code for the representation of names of
        languages."

  [ISO-8601]  ISO (International Organization for Standardization).
        ISO 8601:1988. "Data elements and interchange formats -
        Information interchange - Representation of dates and times."

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  [ISO-11578] ISO (International Organization for Standardization).
        ISO/IEC 11578:1996. "Information technology - Open Systems
        Interconnection - Remote Procedure Call (RPC)"

  [RFC2141]   R. Moats, "URN Syntax." RFC 2141. AT&T. May, 1997.

  [UTF-8]     F. Yergeau, "UTF-8, a transformation format of Unicode
        and ISO 10646." RFC 2279. Alis Technologies. January, 1998.

21.2   Informational References

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

  [RFC1807]   R. Lasher, D. Cohen, "A Format for Bibliographic
        Records," RFC 1807. Stanford, Myricom. 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]   J. A. Slein, F. Vitali, E. J. Whitehead, Jr., D.
        Durand, "Requirements for Distributed Authoring and
        Versioning Protocol for the World Wide Web." RFC 2291. Xerox,
        Univ. of Bologna, U.C. Irvine, Boston Univ. February, 1998.

  [RFC2413]   S. Weibel, J. Kunze, C. Lagoze, M. Wolf, "Dublin Core
        Metadata for Resource Discovery." RFC 2413. OCLC, UCSF,
        Cornell, Reuters. September, 1998.

  [RFC2376]   E. Whitehead, M. Murata, "XML Media Types." RFC 2376.
        U.C. Irvine, Fuji Xerox Info. Systems. July 1998.


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  [RFC3253]   G. Clemm, J. Amsden, T. Ellison, C. Kaler, J. Whitehead,
        "Versioning Extensions to WebDAV (Web Distributed Authoring
        and Versioning)", RFC 3253. Rational Software, IBM,
        Microsoft, UCSC. March 2002.


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22 Authors' Addresses

  Y. Y. Goland
  Microsoft Corporation
  One Microsoft Way
  Redmond, WA 98052-6399
  Email: yarong@microsoft.com

  E. J. Whitehead, Jr.
  Dept. Of Information and Computer Science
  University of California, Irvine
  Irvine, CA 92697-3425
  Email: ejw@ics.uci.edu

  A. Faizi
  Netscape
  685 East Middlefield Road
  Mountain View, CA 94043
  Email: asad@netscape.com

  S. R. Carter
  Novell
  1555 N. Technology Way
  M/S ORM F111
  Orem, UT 84097-2399
  Email: srcarter@novell.com

  D. Jensen
  Novell
  1555 N. Technology Way
  M/S ORM F111
  Orem, UT 84097-2399
  Email: dcjensen@novell.com

  L. Dusseault
  Xythos Software, Inc.
  25 Maiden Lane, 6th floor
  San Francisco
  Email: lisa@xythos.com

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23 Appendices

23.1   Appendix 1 - WebDAV Document Type Definition

  This section provides a document type definition, following the
  rules in [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 ==================-->

  <!-- General-use Elements -->
  <!ELEMENT href (#PCDATA) >
  <!ELEMENT prop ANY >

  <!-- Property Elements for 'lockdiscovery' and 'supportedlock' -->
  <!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+) >

  <!-- Property Elements for 'source' -->
  <!ELEMENT link (src+, dst+) >
  <!ELEMENT dst (#PCDATA) >
  <!ELEMENT src (#PCDATA) >

  <!-- Multi-Status Response Body Elements -->
  <!ELEMENT multistatus (response+, responsedescription?) >
  <!ELEMENT response (href, ((href*, status)|(propstat+)),
  responsedescription?) >
  <!ELEMENT status (#PCDATA) >
  <!ELEMENT propstat (prop, status, responsedescription?) >

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  <!ELEMENT responsedescription (#PCDATA) >

  <!-- PROPPATCH Request Body Elements -->
  <!ELEMENT propertyupdate (remove | set)+ >
  <!ELEMENT remove (prop) >
  <!ELEMENT set (prop) >

  <!-- PROPFIND Request Body Elements -->
  <!ELEMENT propfind (allprop | propname | prop) >
  <!ELEMENT allprop EMPTY >
  <!ELEMENT propname EMPTY >

  <!-- Property Elements for 'resourcetype' -->
  <!ELEMENT collection EMPTY >

  <!--========= Property Name 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)* >
  ]>

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

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  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.

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.


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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).

  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>


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  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/">
     <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.

23.4   Appendix 4: UUID Node Generation

  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, 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:

    - the percent of memory in use

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    - the size of main memory in bytes
    - the amount of free main memory in bytes
    - the size of the paging or swap file in bytes
    - free bytes of paging or swap file
    - the total size of user virtual address space in bytes
    - the total available user address space bytes
    - the size of boot disk drive in bytes
    - the free disk space on boot drive in bytes
    - the current time
    - the amount of time since the system booted
    - the individual sizes of files in various system directories
    - the creation, last read, and modification times of files in
      various system directories
    - the utilization factors of various system resources (heap, etc.)
    - current mouse cursor position
    - current caret position
    - current number of running processes, threads
    - handles or IDs of the desktop window and the active window
    - the value of stack pointer of the caller
    - the process and thread ID of caller
    - 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.

24 Full Copyright Statement

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


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  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.




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