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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-00.txt     A. Faizi, Netscape
   Expires: Aug 2002                                  S. Carter, Novell
                                                      D. Jensen, Novell
                                                   L. Dusseault, Xythos


      HTTP Extensions for Distributed Authoring û 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....................................................7
   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..............................................9
   4.5  Property Names..............................................10
   4.6  Media Independent Links.....................................10
   5  Collections of Web Resources..................................11
   5.1  HTTP URL Namespace Model....................................11
   5.2  Collection Resources........................................11
   5.3  Creation and Retrieval of Collection Resources..............12
   5.4  Source Resources and Output Resources.......................13
   6  Locking.......................................................14
   6.1  Exclusive Vs. Shared Locks..................................14
   6.2  Required Support............................................15
   6.3  Lock Tokens.................................................16
   6.4  opaquelocktoken Lock Token URI Scheme.......................16
   6.4.1 Node Field Generation Without the IEEE 802 Address..........17
   6.5  Lock Capability Discovery...................................18
   6.6  Active Lock Discovery.......................................18
   6.7  Usage Considerations........................................19
   7  Write Lock....................................................19
   7.1  Methods Restricted by Write Locks...........................20
   7.2  Write Locks and Lock Tokens.................................20
   7.3  Write Locks and Properties..................................20
   7.4  Write Locks and Unmapped URLs...............................20
   7.5  Write Locks and Collections.................................21
   7.6  Write Locks and the If Request Header.......................22
   7.6.1 Example - Write Lock........................................22
   7.7  Write Locks and COPY/MOVE...................................23
   7.8  Refreshing Write Locks......................................23
   8  HTTP Methods for Distributed Authoring........................24
   8.1  PROPFIND....................................................24
   8.1.1 Example - Retrieving Named Properties.......................25
   8.1.2 Example - Using propname to Retrieve all Property Names.....27
   8.2  PROPPATCH...................................................28
   8.2.1 Status Codes for use with 207 (Multi-Status)................29
   8.2.2 Example - PROPPATCH.........................................29
   8.3  MKCOL Method................................................30
   8.3.1 Request.....................................................30
   8.3.2 Status Codes................................................31

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   8.3.3 Example - MKCOL.............................................31
   8.4  GET, HEAD for Collections...................................32
   8.5  POST for Collections........................................32
   8.6  DELETE......................................................32
   8.6.1 DELETE for Non-Collection Resources.........................32
   8.6.2 DELETE for Collections......................................33
   8.7  PUT.........................................................34
   8.7.1 PUT for Non-Collection Resources............................34
   8.7.2 PUT for Collections.........................................34
   8.8  COPY Method.................................................34
   8.8.1 COPY for HTTP/1.1 resources.................................35
   8.8.2 COPY for Properties.........................................35
   8.8.3 COPY for Collections........................................35
   8.8.4 COPY and the Overwrite Header...............................36
   8.8.5 Status Codes................................................37
   8.8.6 Example - COPY with Overwrite...............................37
   8.8.7 Example - COPY with No Overwrite............................37
   8.8.8 Example - COPY of a Collection..............................38
   8.9  MOVE Method.................................................39
   8.9.1 MOVE for Properties.........................................39
   8.9.2 MOVE for Collections........................................39
   8.9.3 MOVE and the Overwrite Header...............................40
   8.9.4 Status Codes................................................40
   8.9.5 Example - MOVE of a Non-Collection..........................41
   8.9.6 Example - MOVE of a Collection..............................41
   8.10 LOCK Method.................................................42
   8.10.1 Operation..................................................42
   8.10.2 The Effect of Locks on Properties and Collections..........43
   8.10.3 Locking Replicated Resources...............................43
   8.10.4 Depth and Locking..........................................43
   8.10.5 Interaction with other Methods.............................44
   8.10.6 Lock Compatibility Table...................................44
   8.10.7 Status Codes...............................................44
   8.10.8 Example - Simple Lock Request..............................44
   8.10.9 Example - Refreshing a Write Lock..........................46
   8.10.10 Example - Multi-Resource Lock Request.....................47
   8.11 UNLOCK Method...............................................48
   8.11.1 Example - UNLOCK...........................................48
   9  HTTP Headers for Distributed Authoring........................49
   9.1  DAV Header..................................................49
   9.2  Depth Header................................................49
   9.3  Destination Header..........................................50
   9.4  If Header...................................................50
   9.4.1 No-tag-list Production......................................51
   9.4.2 Tagged-list Production......................................52
   9.4.3 not Production..............................................52
   9.4.4 Matching Function...........................................53

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

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   13.6 getetag Property............................................66
   13.7 getlastmodified Property....................................67
   13.8 lockdiscovery Property......................................67
   13.8.1 Example - Retrieving the lockdiscovery Property............67
   13.9 resourcetype Property.......................................68
   13.10 source Property............................................69
   13.10.1 Example - A source Property...............................69
   13.11 supportedlock Property.....................................70
   13.11.1 Example - Retrieving the supportedlock Property...........70
   14 Instructions for Processing XML in DAV........................71
   15 DAV Compliance Classes........................................71
   15.1 Class 1.....................................................72
   15.2 Class 2.....................................................72
   16 Internationalization Considerations...........................72
   17 Security Considerations.......................................73
   17.1 Authentication of Clients...................................74
   17.2 Denial of Service...........................................74
   17.3 Security through Obscurity..................................75
   17.4 Privacy Issues Connected to Locks...........................75
   17.5 Privacy Issues Connected to Properties......................75
   17.6 Reduction of Security due to Source Link....................75
   17.7 Implications of XML External Entities.......................76
   17.8 Risks Connected with Lock Tokens............................76
   18 IANA Considerations...........................................77
   19 Intellectual Property.........................................77
   20 Acknowledgements..............................................78
   21 References....................................................79
   21.1 Normative References........................................79
   21.2 Informational References....................................80
   22 Authors' Addresses............................................81
   23 Appendices....................................................82
   23.1 Appendix 1 - WebDAV Document Type Definition................82
   23.2 Appendix 2 - ISO 8601 Date and Time Profile.................83
   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
   24 Full Copyright Statement......................................87

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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].

   The sections below provide a detailed introduction to resource
   properties (section 4), collections of resources (section 5), and
   locking operations (section 6).  These sections introduce the
   abstractions manipulated by the WebDAV-specific HTTP methods
   described in section 8, "HTTP Methods for Distributed Authoring".

   In HTTP/1.1, method parameter information was exclusively encoded in
   HTTP headers. Unlike HTTP/1.1, WebDAV encodes method parameter
   information either in an Extensible Markup Language (XML) [REC-XML]
   request entity body, or in an HTTP header.  The use of XML to encode
   method parameters was motivated by the ability to add extra XML
   elements to existing structures, providing extensibility; and by
   XML's ability to encode information in ISO 10646 character sets,
   providing internationalization support. As a rule of thumb,
   parameters are encoded in XML entity bodies when they have unbounded
   length, or when they may be shown to a human user and hence require
   encoding in an ISO 10646 character set.  Otherwise, parameters are
   encoded within HTTP headers.  Section 9 describes the new HTTP
   headers used with WebDAV methods.

   In addition to encoding method parameters, XML is used in WebDAV to
   encode the responses from methods, providing the extensibility and

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   internationalization advantages of XML for method output, as well as
   input.

   XML elements used in this specification are defined in section 12.

   The XML namespace extension is also used in this specification in
   order to allow for new XML elements to be added without fear of
   colliding with other element names.

   While the status codes provided by HTTP/1.1 are sufficient to
   describe most error conditions encountered by WebDAV methods, there
   are some errors that do not fall neatly into the existing
   categories.  New status codes developed for the WebDAV methods are
   defined in section 10.  Since some WebDAV methods may operate over
   many resources, the Multi-Status response has been introduced to
   return status information for multiple resources.  The Multi-Status
   response is described in section 11.

   WebDAV employs the property mechanism to store information about the
   current state of the resource.  For example, when a lock is taken
   out on a resource, a lock information property describes the current
   state of the lock. Section 13 defines the properties used within the
   WebDAV specification.

   Finishing off the specification are sections on what it means to be
   compliant with this specification (section 15), on
   internationalization support (section 16), and on security (section
   17).


2  Notational Conventions

   Since this document describes a set of extensions to the HTTP/1.1
   protocol, the augmented BNF used herein to describe protocol
   elements is exactly the same as described in section 2.1 of
   [RFC2068].  Since this augmented BNF uses the basic production rules
   provided in section 2.2 of [RFC2068], these rules apply to this
   document as well.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in
   this document are to be interpreted as described in RFC 2119
   [RFC2119].


3  Terminology

   URI/URL - A Uniform Resource Identifier and Uniform Resource
   Locator, respectively. These terms (and the distinction between
   them) are defined in [RFC2396].

   Collection - A resource that contains a set of URIs, termed member
   URIs, which identify member resources and meets the requirements in
   section 5 of this specification.

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   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.

   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.

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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
   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-

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   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.

4.5 Property Names

   A property name is a universally unique identifier that is
   associated with a schema that provides information about the syntax
   and semantics of the property.

   Because a property's name is universally unique, clients can depend
   upon consistent behavior for a particular property across multiple
   resources, on the same and across different servers, so long as that
   property is "live" on the resources in question, and the
   implementation of the live property is faithful to its definition.

   The XML namespace mechanism, which is based on URIs [RFC2396], is
   used to name properties because it prevents namespace collisions and
   provides for varying degrees of administrative control.

   The property namespace is flat; that is, no hierarchy of properties
   is explicitly recognized.  Thus, if a property A and a property A/B
   exist on a resource, there is no recognition of any relationship
   between the two properties.  It is expected that a separate
   specification will eventually be produced which will address issues
   relating to hierarchical properties.

   Finally, it is not possible to define the same property twice on a
   single resource, as this would cause a collision in the resource's
   property namespace.

4.6 Media Independent Links

   Although HTML resources support links to other resources, the Web
   needs more general support for links between resources of any media
   type (media types are also known as MIME types, or content types).
   WebDAV provides such links. A WebDAV link is a special type of
   property value, formally defined in section 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.



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5  Collections of Web Resources

   This section provides a description of a new type of Web resource,
   the collection, and discusses its interactions with the HTTP URL
   namespace. The purpose of a collection resource is to model
   collection-like objects (e.g., file system directories) within a
   server's namespace.

   All DAV compliant resources MUST support the HTTP URL namespace
   model specified herein.

5.1 HTTP URL Namespace Model

   The HTTP URL namespace is a hierarchical namespace where the
   hierarchy is delimited with the "/" character.

   An HTTP URL namespace is said to be consistent if it meets the
   following conditions: for every URL in the HTTP hierarchy there
   exists a collection that contains that URL as an internal member.
   The root, or top-level collection of the namespace under
   consideration is exempt from the previous rule.

   Neither HTTP/1.1 nor WebDAV require that the entire HTTP URL
   namespace be consistent.  However, certain WebDAV methods are
   prohibited from producing results that cause namespace
   inconsistencies.

   Although implicit in [RFC2068] and [RFC2396], any resource,
   including collection resources, MAY be identified by more than one
   URI. For example, a resource could be identified by multiple HTTP
   URLs.

5.2 Collection Resources

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

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


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

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

   If a WebDAV compliant resource has no WebDAV compliant children in
   the HTTP URL namespace hierarchy then the WebDAV compliant resource
   is not required to be a collection.

   There is a standing convention that when a collection is referred to
   by its name without a trailing slash, the trailing slash is
   automatically appended.  Due to this, a resource may accept a URI
   without a trailing "/" to point to a collection. In this case it
   SHOULD return a Content-Location header in the response pointing to
   the URI ending with the "/".  For example, if a client invokes a
   method on http://foo.bar/blah (no trailing slash), the resource
   http://foo.bar/blah/ (trailing slash) may respond as if the
   operation were invoked on it, and should return a content-location
   header with http://foo.bar/blah/ in it.  In general clients SHOULD
   use the "/" form of collection names.

   A resource MAY be a collection but not be WebDAV compliant.  That
   is, the resource may comply with all the rules set out in this
   specification regarding how a collection is to behave without
   necessarily supporting all methods that a WebDAV compliant resource
   is required to support.  In such a case the resource may return the
   DAV:resourcetype property with the value DAV:collection but MUST NOT
   return a DAV header containing the value "1" on an OPTIONS response.

   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 Creation and Retrieval of Collection Resources

   This document specifies the MKCOL method to create new collection
   resources, rather than using the existing HTTP/1.1 PUT or POST
   method, for the following reasons:

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   In HTTP/1.1, the PUT method is defined to store the request body at
   the location specified by the Request-URI.  While a description
   format for a collection can readily be constructed for use with PUT,
   the implications of sending such a description to the server are
   undesirable.  For example, if a description of a collection that
   omitted some existing resources were PUT to a server, this might be
   interpreted as a command to remove those members.  This would extend
   PUT to perform DELETE functionality, which is undesirable since it
   changes the semantics of PUT, and makes it difficult to control
   DELETE functionality with an access control scheme based on methods.

   While the POST method is sufficiently open-ended that a "create a
   collection" POST command could be constructed, this is undesirable
   because it would be difficult to separate access control for
   collection creation from other uses of POST.

   The exact definition of the behavior of GET and PUT on collections
   is defined later in this document.

5.4 Source Resources and Output Resources

   For many resources, the entity returned by a GET method exactly
   matches the persistent state of the resource, for example, a GIF
   file stored on a disk.  For this simple case, the URI at which a
   resource is accessed is identical to the URI at which the source
   (the persistent state) of the resource is accessed.  This is also
   the case for HTML source files that are not processed by the server
   prior to transmission.

   However, the server can sometimes process HTML resources before they
   are transmitted as a return entity body.  For example, a server-
   side-include directive within an HTML file might instruct a server
   to replace the directive with another value, such as the current
   date.  In this case, what is returned by GET (HTML plus date)
   differs from the persistent state of the resource (HTML plus
   directive).  Typically there is no way to access the HTML resource
   containing the unprocessed directive.

   Sometimes the entity returned by GET is the output of a data-
   producing process that is described by one or more source resources
   (that may not even have a location in the URI namespace).  A single
   data-producing process may dynamically generate the state of a
   potentially large number of output resources.  An example of this is
   a CGI script that describes a "finger" gateway process that maps
   part of the namespace of a server into finger requests, such as
   http://www.foo.bar.org/finger_gateway/user@host.

   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

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   source resource(s) is desired, the source resource(s) should be
   given a location in the URI namespace.  This source location should
   not be one of the locations at which the generated output is
   retrievable, since in general it is impossible for the server to
   differentiate requests for source resources from requests for
   process output resources.  There is often a many-to-many
   relationship between source resources and output resources.

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

6  Locking

   The ability to lock a resource provides a mechanism for serializing
   access to that resource.  Using a lock, an authoring client can
   provide a reasonable guarantee that another principal will not
   modify a resource while it is being edited.  In this way, a client
   can prevent the "lost update" problem.

   This specification allows locks to vary over two client-specified
   parameters, the number of principals involved (exclusive vs. shared)
   and the type of access to be granted. This document defines locking
   for only one access type, write. However, the syntax is extensible,
   and permits the eventual specification of locking for other access
   types.

6.1 Exclusive Vs. Shared Locks

   The most basic form of lock is an exclusive lock.  This is a lock
   where the access right in question is only granted to a single
   principal.  The need for this arbitration results from a desire to
   avoid having to merge results.

   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

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   who are trusted, for example, may have permission to write to the
   resource.  Among those who have access permission to write to the
   resource, the set of principals who have taken out a shared lock
   also must trust each other, creating a (typically) smaller trust set
   within the access permission write set.

   Starting with every possible principal on the Internet, in most
   situations the vast majority of these principals will not have write
   access to a given resource.  Of the small number who do have write
   access, some principals may decide to guarantee their edits are free
   from overwrite conflicts by using exclusive write locks.  Others may
   decide they trust their collaborators will not overwrite their work
   (the potential set of collaborators being the set of principals who
   have write permission) and use a shared lock, which informs their
   collaborators that a principal may be working on the resource.

   The WebDAV extensions to HTTP do not need to provide all of the
   communications paths necessary for principals to coordinate their
   activities.  When using shared locks, principals may use any out of
   band communication channel to coordinate their work (e.g., face-to-
   face interaction, written notes, post-it notes on the screen,
   telephone conversation, Email, etc.)  The intent of a shared lock is
   to let collaborators know who else may be working on a resource.

   Shared locks are included because experience from web distributed
   authoring systems has indicated that exclusive locks are often too
   rigid.  An exclusive lock is used to enforce a particular editing
   process: take out an exclusive lock, read the resource, perform
   edits, write the resource, release the lock.  This editing process
   has the problem that locks are not always properly released, for
   example when a program crashes, or when a lock owner leaves without
   unlocking a resource.  While both timeouts and administrative action
   can be used to remove an offending lock, neither mechanism may be
   available when needed; the timeout may be long or the administrator
   may not be available.

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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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.


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                         WebDAV û RFC2518 bis            February 2002

   Extension = path  ; path is defined in section 3.2.1 of RFC 2068
   [RFC2068]

6.4.1 Node Field Generation Without the IEEE 802 Address

   UUIDs, as defined in [ISO-11578], contain a "node" field that
   contains one of the IEEE 802 addresses for the server machine.  As
   noted in section 17, 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
     - 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

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       (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.

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.


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

6.7 Usage Considerations

   Although the locking mechanisms specified here provide some help in
   preventing lost updates, they cannot guarantee that updates will
   never be lost.  Consider the following scenario:

   Two clients A and B are interested in editing the resource
   'index.html'.  Client A is an HTTP client rather than a WebDAV
   client, and so does not know how to perform locking.

   Client A doesn't lock the document, but does a GET and begins
   editing.
   Client B does LOCK, performs a GET and begins editing.
   Client B finishes editing, performs a PUT, then an UNLOCK.
   Client A performs a PUT, overwriting and losing all of B's changes.

   There are several reasons why the WebDAV protocol itself cannot
   prevent this situation.  First, it cannot force all clients to use
   locking because it must be compatible with HTTP clients that do not
   comprehend locking.  Second, it cannot require servers to support
   locking because of the variety of repository implementations, some
   of which rely on reservations and merging rather than on locking.
   Finally, being stateless, it cannot enforce a sequence of operations
   like LOCK / GET / PUT / UNLOCK.

   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


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

7.1 Methods Restricted by Write Locks

   A write lock MUST prevent a principal without the lock from
   successfully executing a PUT, POST, PROPPATCH, LOCK, UNLOCK, MOVE,
   DELETE, or MKCOL on the locked resource.  All other current methods,
   GET in particular, function independently of the lock.

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

7.2 Write Locks and Lock Tokens

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

7.3 Write Locks and Properties

   While those without a write lock may not alter a property on a
   resource it is still possible for the values of live properties to
   change, even while locked, due to the requirements of their schemas.
   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.

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   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.
   - 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


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   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

   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


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     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
   resource into a collection that is locked with "Depth: infinity",
   then the resource will be added to the lock.

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

7.8 Refreshing Write Locks

   A client MUST NOT submit the same write lock request twice.  Note
   that a client is always aware it is resubmitting the same lock
   request because it must include the lock token in the If header in
   order to make the request for a resource that is already locked.

   However, a client may submit a LOCK method with an If header but
   without a body.  This form of LOCK MUST only be used to "refresh" a

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   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.

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.


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   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 DeltaV and ACL specifications
   [TODO: ref 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
   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/>

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        <R:author/>
        <R:DingALing/>
        <R:Random/>
      </D:prop>
     </D:propfind>

   >>Response

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

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
      <D:response>
        <D:href>http://www.foo.bar/file</D:href>
        <D:propstat>
          <D:prop xmlns:R="http://www.foo.bar/boxschema/">
            <R:bigbox>
              <R:BoxType>Box type A</R:BoxType>
            </R:bigbox>
            <R:author>
              <R:Name>J.J. Johnson</R:Name>
            </R:author>
          </D:prop>
          <D:status>HTTP/1.1 200 OK</D:status>
        </D:propstat>
        <D:propstat>
          <D:prop><R:DingALing/><R:Random/></D:prop>
          <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.


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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/>
            <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/>

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            <supportedlock/>
          </prop>
          <status>HTTP/1.1 200 OK</status>
        </propstat>
      </response>
     </multistatus>


   In this example, PROPFIND is invoked on the collection resource
   http://www.foo.bar/container/, with a propfind XML element
   containing the propname XML element, meaning the name of all
   properties should be returned.  Since no Depth header is present, it
   assumes its default value of "infinity", meaning the name of the
   properties on the collection and all its progeny should be returned.

   Consistent with the previous example, resource
   http://www.foo.bar/container/ has six properties defined on it,
   http://www.foo.bar/boxschema/bigbox,
   http://www.foo.bar/boxschema/author, DAV:creationdate,
   DAV:displayname, DAV:resourcetype, and DAV:supportedlock.

   The resource http://www.foo.bar/container/index.html, a member of
   the "container" collection, has nine properties defined on it,
   http://www.foo.bar/boxschema/bigbox, DAV:creationdate,
   DAV:displayname, DAV:getcontentlength, DAV:getcontenttype,
   DAV:getetag, DAV:getlastmodified, DAV:resourcetype, and
   DAV:supportedlock.

   This example also demonstrates the use of XML namespace scoping, and
   the default namespace.  Since the "xmlns" attribute does not contain
   an explicit "shorthand name" (prefix) letter, the namespace applies
   by default to all enclosed elements.  Hence, all elements which do
   not explicitly state the namespace to which they belong are members
   of the "DAV:" namespace schema.

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).

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   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.

   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>

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      </D:set>
      <D:remove>
        <D:prop><Z:Copyright-Owner/></D:prop>
      </D:remove>
     </D:propertyupdate>

   >>Response

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

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:"
     xmlns:Z="http://www.w3.com/standards/z39.50">
      <D:response>
        <D:href>http://www.foo.com/bar.html</D:href>
        <D:propstat>
          <D:prop><Z:Authors/></D:prop>
          <D:status>HTTP/1.1 424 Failed Dependency</D:status>
        </D:propstat>
        <D:propstat>
          <D:prop><Z:Copyright-Owner/></D:prop>
          <D:status>HTTP/1.1 409 Conflict</D:status>
        </D:propstat>
        <D:responsedescription> Copyright Owner can not be deleted or
     altered.</D:responsedescription>
      </D:response>
     </D:multistatus>

   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


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   MKCOL creates a new collection resource at the location specified by
   the Request-URI.  If the resource identified by the Request-URI is
   non-null then the MKCOL MUST fail.  During MKCOL processing, a
   server MUST make the Request-URI a member of its parent collection,
   unless the Request-URI is "/".  If no such ancestor exists, the
   method MUST fail.  When the MKCOL operation creates a new collection
   resource, all ancestors MUST already exist, or the method MUST fail
   with a 409 (Conflict) status code.  For example, if a request to
   create collection /a/b/c/d/ is made, and neither /a/b/ nor /a/b/c/
   exists, the request must fail.

   When MKCOL is invoked without a request body, the newly created
   collection SHOULD have no members.

   A MKCOL request message may contain a message body.  The behavior of
   a MKCOL request when the body is present is limited to creating
   collections, members of a collection, bodies of members and
   properties on the collections or members.  If the server receives a
   MKCOL request entity type it does not support or understand it MUST
   respond with a 415 (Unsupported Media Type) status code.  The exact
   behavior of MKCOL for various request media types is undefined in
   this document, and will be specified in separate documents.

8.3.2 Status Codes

   Responses from a MKCOL request MUST NOT be cached as MKCOL has non-
   idempotent semantics.

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

   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


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   This example creates a collection called /webdisc/xfiles/ on the
   server www.server.org.

   >>Request

     MKCOL /webdisc/xfiles/ HTTP/1.1
     Host: www.server.org

   >>Response

     HTTP/1.1 201 Created


8.4 GET, HEAD for Collections

   The semantics of GET are unchanged when applied to a collection,
   since GET is defined as, "retrieve whatever information (in the form
   of an entity) is identified by the Request-URI" [RFC2068].  GET when
   applied to a collection may return the contents of an "index.html"
   resource, a human-readable view of the contents of the collection,
   or something else altogether. Hence it is possible that the result
   of a GET on a collection will bear no correlation to the membership
   of the collection.

   Similarly, since the definition of HEAD is a GET without a response
   message body, the semantics of HEAD are unmodified when applied to
   collection resources.

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.


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8.6.2 DELETE for Collections

   The DELETE method on a collection MUST act as if a "Depth: infinity"
   header was used on it.  A client MUST NOT submit a Depth header with
   a DELETE on a collection with any value but infinity.

   DELETE instructs that the collection specified in the Request-URI
   and all resources identified by its internal member URIs are to be
   deleted.

   If any resource identified by a member URI cannot be deleted then
   all of the member's ancestors MUST NOT be deleted, so as to maintain
   namespace consistency.

   Any headers included with DELETE MUST be applied in processing every
   resource to be deleted.

   When the DELETE method has completed processing it MUST result in a
   consistent namespace.

   If an error occurs with a resource other than the resource
   identified in the Request-URI then the response MUST be a 207
   (Multi-Status).  424 (Failed Dependency) errors SHOULD NOT be in the
   207 (Multi-Status).  They can be safely left out because the client
   will know that the ancestors of a resource could not be deleted when
   the client receives an error for the ancestor's progeny.
   Additionally 204 (No Content) errors SHOULD NOT be returned in the
   207 (Multi-Status).  The reason for this prohibition is that 204 (No
   Content) is the default success code.

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>


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   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).

8.7.2 PUT for Collections

   As defined in the HTTP/1.1 specification [RFC2068], the "PUT method
   requests that the enclosed entity be stored under the supplied
   Request-URI."  Since submission of an entity representing a
   collection would implicitly encode creation and deletion of
   resources, this specification intentionally does not define a
   transmission format for creating a collection using PUT.  Instead,
   the MKCOL method is defined to create collections.

   When the PUT operation creates a new non-collection resource all
   ancestors MUST already exist.  If all ancestors do not exist, the
   method MUST fail with a 409 (Conflict) status code.  For example, if
   resource /a/b/c/d.html is to be created and /a/b/c/ does not exist,
   then the request must fail.

8.8 COPY Method

   The COPY method creates a duplicate of the source resource,
   identified by the Request-URI, in the destination resource,
   identified by the URI in the Destination header.  The Destination
   header MUST be present.  The exact behavior of the COPY method
   depends on the type of the source resource.

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   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
   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.


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   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.

   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.

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8.8.5 Status Codes

   201 (Created) - The source resource was successfully copied.  The
   copy operation resulted in the creation of a new resource.

   204 (No Content) - The source resource was successfully copied to a
   pre-existing destination resource.

   403 (Forbidden) 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.

   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


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   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/
     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.


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8.9 MOVE Method

   The MOVE operation on a non-collection resource is the logical
   equivalent of a copy (COPY), followed by consistency maintenance
   processing, followed by a delete of the source, where all three
   actions are performed atomically.  The consistency maintenance step
   allows the server to perform updates caused by the move, such as
   updating all URIs other than the Request-URI which identify the
   source resource, to point to the new destination resource.
   Consequently, the Destination header MUST be present on all MOVE
   methods and MUST follow all COPY requirements for the COPY part of
   the MOVE method.  All DAV compliant resources MUST support the MOVE
   method.  However, support for the MOVE method does not guarantee the
   ability to move a resource to a particular destination.

   For example, separate programs may actually control different sets
   of resources on the same server.  Therefore, it may not be possible
   to move a resource within a namespace that appears to belong to the
   same server.

   If a resource exists at the destination, the destination resource
   will be DELETEd as a side-effect of the MOVE operation, subject to
   the restrictions of the Overwrite header.

8.9.1 MOVE for Properties

   The behavior of properties on a MOVE 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

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   error occurs while moving an internal collection, the server MUST
   NOT move any resources identified by members of the failed
   collection (i.e., the server must skip the error-causing subtree),
   as this would create an inconsistent namespace. In this case, after
   detecting the error, the move operation SHOULD try to finish as much
   of the original move as possible (i.e., the server should still
   attempt to move other subtrees and the resources identified by their
   members, that are not descendents of an error-causing collection).
   So, for example, if an infinite depth move is performed on
   collection /a/, which contains collections /a/b/ and /a/c/, and an
   error occurs moving /a/b/, an attempt should still be made to try
   moving /a/c/. Similarly, after encountering an error moving a non-
   collection resource as part of an infinite depth move, the server
   SHOULD try to finish as much of the original move operation as
   possible.

   If an error occurs with a resource other than the resource
   identified in the Request-URI then the response MUST be a 207
   (Multi-Status).

   The 424 (Failed Dependency) status code SHOULD NOT be returned in
   the 207 (Multi-Status) response from a MOVE method.  These errors
   can be safely omitted because the client will know that the progeny
   of a resource could not be moved when the client receives an error
   for the parent.  Additionally 201 (Created)/204 (No Content)
   responses SHOULD NOT be returned as values in 207 (Multi-Status)
   responses from a MOVE.  These responses can be safely omitted
   because they are the default success codes.

8.9.3 MOVE and the Overwrite Header

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

8.9.4 Status Codes

   201 (Created) - The source resource was successfully moved, and a
   new resource was created at the destination.

   204 (No Content) - The source resource was successfully moved to a
   pre-existing destination resource.

   403 (Forbidden) 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.

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   423 (Locked) - The source or the destination resource was locked.

   502 (Bad Gateway) - This may occur when the destination is on
   another server and the destination server refuses to accept the
   resource.

8.9.5 Example - MOVE of a Non-Collection

   This example shows resource
   http://www.ics.uci.edu/~fielding/index.html being moved to the
   location http://www.ics.uci.edu/users/f/fielding/index.html. The
   contents of the destination resource would have been overwritten if
   the destination resource had been non-null.  In this case, since
   there was nothing at the destination resource, the response code is
   201 (Created).

   >>Request

     MOVE /~fielding/index.html HTTP/1.1
     Host: www.ics.uci.edu
     Destination: http://www.ics.uci.edu/users/f/fielding/index.html

   >>Response

     HTTP/1.1 201 Created
     Location: http://www.ics.uci.edu/users/f/fielding/index.html


8.9.6 Example - MOVE of a Collection

   >>Request

     MOVE /container/ HTTP/1.1
     Host: www.foo.bar
     Destination: http://www.foo.bar/othercontainer/
     Overwrite: F
     If: (<opaquelocktoken:fe184f2e-6eec-41d0-c765-01adc56e6bb4>)
         (<opaquelocktoken:e454f3f3-acdc-452a-56c7-00a5c91e4b77>)


   >>Response

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

     <?xml version="1.0" encoding="utf-8" ?>

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     <d:multistatus xmlns:d='DAV:'>
      <d:response>
        <d:href>http://www.foo.bar/othercontainer/C2/</d:href>
        <d:status>HTTP/1.1 423 Locked</d:status>
      </d:response>
     </d:multistatus>

   In this example the client has submitted a number of lock tokens
   with the request.  A lock token will need to be submitted for every
   resource, both source and destination, anywhere in the scope of the
   method, that is locked.  In this case the proper lock token was not
   submitted for the destination http://www.foo.bar/othercontainer/C2/.
   This means that the resource /container/C2/ could not be moved.
   Because there was an error copying /container/C2/, none of
   /container/C2's members were copied.  However no errors were listed
   for those members due to the error minimization rules given in
   section 8.8.3.  User agent authentication has previously occurred
   via a mechanism outside the scope of the HTTP protocol, in an
   underlying transport layer.

8.10    LOCK Method

   The following sections describe the LOCK method, which is used to
   take out a lock of any access type.  These sections on the LOCK
   method describe only those semantics that are specific to the LOCK
   method and are independent of the access type of the lock being
   requested.

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

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.


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

8.10.2 The Effect of Locks on Properties and Collections

   The scope of a lock is the entire state of the resource, including
   its body and associated properties.  As a result, a lock on a
   resource MUST also lock the resource's properties.

   For collections, a lock also affects the ability to add or remove
   members.  The nature of the effect depends upon the type of access
   control involved.

8.10.3 Locking Replicated Resources

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

8.10.4 Depth and Locking

   The Depth header may be used with the LOCK method.  Values other
   than 0 or infinity MUST NOT be used with the Depth header on a LOCK
   method.  All resources that support the LOCK method MUST support the
   Depth header.

   A Depth header of value 0 means to just lock the resource specified
   by the Request-URI.

   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.


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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*


   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

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     Host: webdav.sb.aol.com
     Timeout: Infinite, Second-4100000000
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx
     Authorization: Digest username="ejw",
        realm="ejw@webdav.sb.aol.com", nonce="...",
        uri="/workspace/webdav/proposal.doc",
        response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:lockinfo xmlns:D='DAV:'>
      <D:lockscope><D:exclusive/></D:lockscope>
      <D:locktype><D:write/></D:locktype>
      <D:owner>
        <D:href>http://www.ics.uci.edu/~ejw/contact.html</D:href>
      </D:owner>
     </D:lockinfo>

   >>Response

     HTTP/1.1 200 OK
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:prop xmlns:D="DAV:">
      <D:lockdiscovery>
        <D:activelock>
          <D:locktype><D:write/></D:locktype>
          <D:lockscope><D:exclusive/></D:lockscope>
          <D:depth>infinity</D:depth>
          <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

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   http://webdav.sb.aol.com/workspace/webdav/proposal.doc.  The
   resource http://www.ics.uci.edu/~ejw/contact.html contains contact
   information for the owner of the lock.  The server has an activity-
   based timeout policy in place on this resource, which causes the
   lock to automatically be removed after 1 week (604800 seconds).
   Note that the nonce, response, and opaque fields have not been
   calculated in the Authorization request header.

8.10.9 Example - Refreshing a Write Lock

   >>Request

     LOCK /workspace/webdav/proposal.doc HTTP/1.1
     Host: webdav.sb.aol.com
     Timeout: Infinite, Second-4100000000
     If: (<opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4>)
     Authorization: Digest username="ejw",
        realm="ejw@webdav.sb.aol.com", nonce="...",
        uri="/workspace/webdav/proposal.doc",
        response="...", opaque="..."

   >>Response

     HTTP/1.1 200 OK
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:prop xmlns:D="DAV:">
      <D:lockdiscovery>
        <D:activelock>
          <D:locktype><D:write/></D:locktype>
          <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>

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   This request would refresh the lock, resetting any time outs.
   Notice that the client asked for an infinite time out but the server
   choose to ignore the request. In this example, the nonce, response,
   and opaque fields have not been calculated in the Authorization
   request header.

8.10.10 Example - Multi-Resource Lock Request

   >>Request

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

     <?xml version="1.0" encoding="utf-8" ?>
     <D:lockinfo xmlns:D="DAV:">
      <D:locktype><D:write/></D:locktype>
      <D:lockscope><D:exclusive/></D:lockscope>
      <D:owner>
        <D:href>http://www.ics.uci.edu/~ejw/contact.html</D:href>
      </D:owner>
     </D:lockinfo>

   >>Response

     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>

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        </D:propstat>
      </D:response>
     </D:multistatus>

   This example shows a request for an exclusive write lock on a
   collection and all its children.  In this request, the client has
   specified that it desires an infinite length lock, if available,
   otherwise a timeout of 4.1 billion seconds, if available. The
   request entity body contains the contact information for the
   principal taking out the lock, in this case a web page URL.

   The error is a 403 (Forbidden) response on the resource
   http://webdav.sb.aol.com/webdav/secret.  Because this resource could
   not be locked, none of the resources were locked.  Note also that
   the lockdiscovery property for the Request-URI has been included as
   required.  In this example the lockdiscovery property is empty which
   means that there are no outstanding locks on the resource.

   In this example, the nonce, response, and opaque fields have not
   been calculated in the Authorization request header.

8.11    UNLOCK Method

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

   Any DAV compliant resource which supports the LOCK method MUST
   support the UNLOCK method.

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



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   In this example, the lock identified by the lock token
   "opaquelocktoken:a515cfa4-5da4-22e1-f5b5-00a0451e6bf7" is
   successfully removed from the resource
   http://webdav.sb.aol.com/workspace/webdav/info.doc.  If this lock
   included more than just one resource, the lock is removed from all
   resources included in the lock.  The 204 (No Content) status code is
   used instead of 200 (OK) because there is no response entity body.

   In this example, the nonce, response, and opaque fields have not
   been calculated in the Authorization request header.


9  HTTP Headers for Distributed Authoring

9.1 DAV Header

   DAV = "DAV" ":" "1" ["," "2"] ["," 1#extend]

   This header indicates that the resource supports the DAV schema and
   protocol as specified. All DAV compliant resources MUST return the
   DAV header on all OPTIONS responses.

   The value is a list of all compliance classes that the resource
   supports.  Note that above a comma has already been added to the 2.
   This is because a resource can not be level 2 compliant unless it is
   also level 1 compliant. Please refer to section 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

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   example, the MOVE method only supports "Depth: infinity" and if a
   Depth header is not present will act as if a "Depth: infinity"
   header had been applied.

   Clients MUST NOT rely upon methods executing on members of their
   hierarchies in any particular order or on the execution being atomic
   unless the particular method explicitly provides such guarantees.

   Upon execution, a method with a Depth header will perform as much of
   its assigned task as possible and then return a response specifying
   what it was able to accomplish and what it failed to do.

   So, for example, an attempt to COPY a hierarchy may result in some
   of the members being copied and some not.

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

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

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

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

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


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   If = "If" ":" ( 1*No-tag-list | 1*Tagged-list)
   No-tag-list = List
   Tagged-list = Resource 1*List
   Resource = Coded-URL
   List = "(" 1*(["Not"](State-token | "[" entity-tag "]")) ")"
   State-token = Coded-URL
   Coded-URL = "<" absoluteURI ">"

   The If header is intended to have similar functionality to the If-
   Match header defined in section 14.25 of [RFC2068].  However the If
   header is intended for use with any URI which represents state
   information, referred to as a state token, about a resource as well
   as ETags.  A typical example of a state token is a lock token, and
   lock tokens are the only state tokens defined in this specification.

   All DAV compliant resources MUST honor the If header.

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

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

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"])).


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9.4.2 Tagged-list Production

   The tagged-list production scopes a list production.  That is, it
   specifies that the lists following the resource specification only
   apply to the specified resource.  The scope of the resource
   production begins with the list production immediately following the
   resource production and ends with the next resource production, if
   any.

   When the If header is applied to a particular resource, the Tagged-
   list productions MUST be searched to determine if any of the listed
   resources match the operand resource(s) for the current method.  If
   none of the resource productions match the current resource then the
   header MUST be ignored.  If one of the resource productions does
   match the name of the resource under consideration then the list
   productions following the resource production MUST be applied to the
   resource in the manner specified in the previous section.

   The same URI MUST NOT appear more than once in a resource production
   in an If header.

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.

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   The scope of the not production is the state-token or entity-tag
   immediately following it.

     If: (Not <locktoken:write1> <locktoken:write2>)

   When submitted with a request, this If header requires that all
   operand resources must not be locked with locktoken:write1 and must
   be locked with locktoken:write2.

9.4.4 Matching Function

   When performing If header processing, the definition of a matching
   state token or entity tag is as follows.

   Matching entity tag: Where the entity tag matches an entity tag
   associated with that resource.

   Matching state token: Where there is an exact match between the
   state token in the If header and any state token on the resource.

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")


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   The Overwrite header specifies whether the server should overwrite
   the state of a non-null destination resource during a COPY or MOVE.
   A value of "F" states that the server must not perform the COPY or
   MOVE operation if the state of the destination resource is non-null.
   If the overwrite header is not included in a COPY or MOVE request
   then the resource MUST treat the request as if it has an overwrite
   header of value "T". While the Overwrite header appears to duplicate
   the functionality of the If-Match: * header of HTTP/1.1, If-Match
   applies only to the Request-URI, and not to the Destination of a
   COPY or MOVE.

   If a COPY or MOVE is not performed due to the value of the Overwrite
   header, the method MUST fail with a 412 (Precondition Failed) status
   code.

   All DAV compliant resources MUST support the Overwrite header.

9.7 Status-URI Response Header

   The Status-URI response header may be used with the 102 (Processing)
   status code to inform the client as to the status of a method.

   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.

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   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.

   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

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   taking longer than 20 seconds (a reasonable, but arbitrary value) to
   process the server SHOULD return a 102 (Processing) response. The
   server MUST send a final response after the request has been
   completed.

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

10.2    207 Multi-Status

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

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   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.


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

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

   <!ELEMENT locktoken (href+) >

12.1.3 timeout XML Element

   Name:    timeout
   Namespace:   DAV:
   Purpose: The timeout associated with a lock
   Value:   TimeType ;Defined in section 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

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            property containing the link XML element provides the type
            of the link.  Link is a multi-valued element, so multiple
            links may be used together to indicate multiple links with
            the same type.  The values in the href XML elements inside
            the src and dst XML elements of the link XML element MUST
            NOT be rejected if they point to resources which do not
            exist.

   <!ELEMENT link (src+, dst+) >

12.4.1 dst XML Element

   Name:    dst
   Namespace:   DAV:
   Purpose: Indicates the destination of a link
   Value:   URI

   <!ELEMENT dst (#PCDATA) >

12.4.2 src XML Element

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

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   <!ELEMENT lockinfo (lockscope, locktype, owner?) >

12.7    lockscope XML Element

   Name:    lockscope
   Namespace:   DAV:
   Purpose: Specifies whether a lock is an exclusive lock, or a shared
            lock.

   <!ELEMENT lockscope (exclusive | shared) >

12.7.1 exclusive XML Element

   Name:    exclusive
   Namespace:   DAV:
   Purpose: Specifies an exclusive lock

   <!ELEMENT exclusive EMPTY >

12.7.2 shared XML Element

   Name:    shared
   Namespace:   DAV:
   Purpose: Specifies a shared lock

   <!ELEMENT shared EMPTY >

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) >


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12.8.1 write XML Element

   Name:    write
   Namespace:   DAV:
   Purpose: Specifies a write lock.

   <!ELEMENT write EMPTY >

12.9    multistatus XML Element

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

   <!ELEMENT multistatus (response+, responsedescription?) >

12.9.1 response XML Element

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

   <!ELEMENT response (href, ((href*, status)|(propstat+)),
   responsedescription?) >

12.9.1.1        propstat XML Element

   Name:    propstat
   Namespace:   DAV:

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   Purpose: Groups together a prop and status element that is
            associated with a particular href element.
   Description:         The propstat XML element MUST contain one prop
            XML element and one status XML element.  The contents of
            the prop XML element MUST only list the names of properties
            to which the result in the status element applies.

   <!ELEMENT propstat (prop, status, responsedescription?) >

12.9.1.2        status XML Element

   Name:    status
   Namespace:   DAV:
   Purpose: Holds a single HTTP status-line
   Value:   status-line   ;status-line defined in [RFC2068]

   <!ELEMENT status (#PCDATA) >

12.9.2 responsedescription XML Element

   Name:    responsedescription
   Namespace:   DAV:
   Purpose: Contains a message that can be displayed to the user
            explaining the nature of the response.
   Description:         This XML element provides information suitable
            to be presented to a user.

   <!ELEMENT responsedescription (#PCDATA) >

12.10   owner XML Element

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

   <!ELEMENT owner ANY>

12.11   prop XML element

   Name:    prop
   Namespace:   DAV:

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   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)+ >

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

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            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

   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).

   <!ELEMENT creationdate (#PCDATA) >

13.2    displayname Property

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

   <!ELEMENT displayname (#PCDATA) >

13.3    getcontentlanguage Property

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

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   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.
   Value:   content-length ; see section 14.14 of [RFC2068]

   <!ELEMENT getcontentlength (#PCDATA) >

13.5    getcontenttype Property

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

   <!ELEMENT getcontenttype (#PCDATA) >

13.6    getetag Property

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

   <!ELEMENT getetag (#PCDATA) >


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13.7    getlastmodified Property

   Name:    getlastmodified
   Namespace:   DAV:
   Purpose: Contains the Last-Modified header returned by a GET method
            without accept headers.
   Description:         Note that the last-modified date on a resource
            may reflect changes in any part of the state of the
            resource, not necessarily just a change to the response to
            the GET method.  For example, a change in a property may
            cause the last-modified date to change. The getlastmodified
            property MUST be defined on any DAV compliant resource that
            returns the Last-Modified header in response to a GET.
   Value:   HTTP-date  ; defined in section 3.3.1 of [RFC2068]

   <!ELEMENT getlastmodified (#PCDATA) >

13.8    lockdiscovery Property

   Name:    lockdiscovery
   Namespace:   DAV:
   Purpose: Describes the active locks on a resource
   Description:         The lockdiscovery property returns a listing of
            who has a lock, what type of lock he has, the timeout type
            and the time remaining on the timeout, and the associated
            lock token.  The server is free to withhold any or all of
            this information if the requesting principal does not have
            sufficient access rights to see the requested data.

   <!ELEMENT lockdiscovery (activelock)* >

13.8.1 Example - Retrieving the lockdiscovery Property

   >>Request

     PROPFIND /container/ HTTP/1.1
     Host: www.foo.bar
     Content-Length: xxxx
     Content-Type: text/xml; charset="utf-8"

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D='DAV:'>
      <D:prop><D:lockdiscovery/></D:prop>
     </D:propfind>

   >>Response

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

   <!ELEMENT resourcetype ANY >


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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.

   <!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>

   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

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   know about the foocorp elements and be able to present the user with
   additional information about the links.  This example demonstrates
   the power of XML markup, allowing element values to be enhanced
   without breaking older clients.

13.11   supportedlock Property

   Name:    supportedlock
   Namespace:   DAV:
   Purpose: To provide a listing of the lock capabilities supported by
            the resource.
   Description:         The supportedlock property of a resource
            returns a listing of the combinations of scope and access
            types which may be specified in a lock request on the
            resource.  Note that the actual contents are themselves
            controlled by access controls so a server is not required
            to provide information the client is not authorized to see.

   <!ELEMENT supportedlock (lockentry)* >

13.11.1 Example - Retrieving the supportedlock Property

   >>Request

     PROPFIND  /container/ HTTP/1.1
     Host: www.foo.bar
     Content-Length: xxxx
     Content-Type: text/xml; charset="utf-8"

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:">
      <D:prop><D:supportedlock/></D:prop>
     </D:propfind>

   >>Response

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

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
      <D:response>
        <D:href>http://www.foo.bar/container/</D:href>
        <D:propstat>
          <D:prop>
            <D:supportedlock>

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               <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.

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].


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   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
   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.


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   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.


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

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   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.

   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.


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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.

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

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

17.7    Implications of XML External Entities

   XML supports a facility known as "external entities", defined in
   section 4.2.2 of [REC-XML], which instruct an XML processor to
   retrieve and perform an inline include of XML located at a
   particular URI. An external XML entity can be used to append or
   modify the document type declaration (DTD) associated with an XML
   document.  An external XML entity can also be used to include XML
   within the content of an XML document.  For non-validating XML, such
   as the XML used in this specification, including an external XML
   entity is not required by [REC-XML]. However, [REC-XML] does state
   that an XML processor may, at its discretion, include the external
   XML entity.

   External XML entities have no inherent trustworthiness and are
   subject to all the attacks that are endemic to any HTTP GET request.
   Furthermore, it is possible for an external XML entity to modify the
   DTD, and hence affect the final form of an XML document, in the
   worst case significantly modifying its semantics, or exposing the
   XML processor to the security risks discussed in [RFC2376].
   Therefore, implementers must be aware that external XML entities
   should be treated as untrustworthy.

   There is also the scalability risk that would accompany a widely
   deployed application which made use of external XML entities.  In
   this situation, it is possible that there would be significant
   numbers of requests for one external XML entity, potentially
   overloading any server which fields requests for the resource
   containing the external XML entity.

17.8    Risks Connected with Lock Tokens

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

   There are several risks associated with exposure of IEEE 802
   addresses.  Using the IEEE 802 address:

   * It is possible to track the movement of hardware from subnet to
   subnet.


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   * It may be possible to identify the manufacturer of the hardware
   running a WebDAV server.

   * It may be possible to determine the number of each type of
   computer running WebDAV.
   Section 6.4.1 of this specification details an alternate mechanism
   for generating the "node" field of a UUID without using an IEEE 802
   address, which alleviates the risks associated with exposure of IEEE
   802 addresses by using an alternate source of uniqueness.


18 IANA Considerations

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

   URIs are used for both names, for several reasons. Assignment of a
   URI does not require a request to a central naming authority, and
   hence allow WebDAV property names and XML elements to be quickly
   defined by any WebDAV user or application.  URIs also provide a
   unique address space, ensuring that the distributed users of WebDAV
   will not have collisions among the property names and XML elements
   they create.

   This specification defines a distinguished set of property names and
   XML elements that are understood by all WebDAV applications.  The
   property names and XML elements in this specification are all
   derived from the base URI DAV: by adding a suffix to this URI, for
   example, DAV:creationdate for the "creationdate" property.

   This specification also defines a URI scheme for the encoding of
   lock tokens, the opaquelocktoken URI scheme described in section
   6.4.

   To ensure correct interoperation based on this specification, IANA
   must reserve the URI namespaces starting with "DAV:" and with
   "opaquelocktoken:" for use by this specification, its revisions, and
   related WebDAV specifications.

19 Intellectual Property

   The following notice is copied from RFC 2026 [RFC2026], section
   10.4, and describes the position of the IETF concerning intellectual
   property claims made against this document.

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use other technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it

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   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
   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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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 ==================-->

   <!ELEMENT activelock (lockscope, locktype, depth, owner?, timeout?,
   locktoken?) >

   <!ELEMENT lockentry (lockscope, locktype) >
   <!ELEMENT lockinfo (lockscope, locktype, owner?) >

   <!ELEMENT locktype (write) >
   <!ELEMENT write EMPTY >

   <!ELEMENT lockscope (exclusive | shared) >
   <!ELEMENT exclusive EMPTY >
   <!ELEMENT shared EMPTY >

   <!ELEMENT depth (#PCDATA) >

   <!ELEMENT owner ANY >

   <!ELEMENT timeout (#PCDATA) >

   <!ELEMENT locktoken (href+) >

   <!ELEMENT href (#PCDATA) >

   <!ELEMENT link (src+, dst+) >
   <!ELEMENT dst (#PCDATA) >
   <!ELEMENT src (#PCDATA) >

   <!ELEMENT multistatus (response+, responsedescription?) >

   <!ELEMENT response (href, ((href*, status)|(propstat+)),
   responsedescription?) >
   <!ELEMENT status (#PCDATA) >
   <!ELEMENT propstat (prop, status, responsedescription?) >

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   <!ELEMENT responsedescription (#PCDATA) >

   <!ELEMENT prop ANY >

   <!ELEMENT propertyupdate (remove | set)+ >
   <!ELEMENT remove (prop) >
   <!ELEMENT set (prop) >

   <!ELEMENT propfind (allprop | propname | prop) >
   <!ELEMENT allprop EMPTY >
   <!ELEMENT propname EMPTY >

   <!ELEMENT collection EMPTY >

   <!--=========== Property Elements from Section 13 ===============-->
   <!ELEMENT creationdate (#PCDATA) >
   <!ELEMENT displayname (#PCDATA) >
   <!ELEMENT getcontentlanguage (#PCDATA) >
   <!ELEMENT getcontentlength (#PCDATA) >
   <!ELEMENT getcontenttype (#PCDATA) >
   <!ELEMENT getetag (#PCDATA) >
   <!ELEMENT getlastmodified (#PCDATA) >
   <!ELEMENT lockdiscovery (activelock)* >
   <!ELEMENT resourcetype ANY >
   <!ELEMENT source (link)* >
   <!ELEMENT supportedlock (lockentry)* >
   ]>

23.2    Appendix 2 - ISO 8601 Date and Time Profile

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

   date-time       = full-date "T" full-time

   full-date       = date-fullyear "-" date-month "-" date-mday
   full-time       = partial-time time-offset

   date-fullyear   = 4DIGIT
   date-month      = 2DIGIT  ; 01-12
   date-mday       = 2DIGIT  ; 01-28, 01-29, 01-30, 01-31 based on
   month/year
   time-hour       = 2DIGIT  ; 00-23
   time-minute     = 2DIGIT  ; 00-59

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   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.


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23.3    Appendix 3 - Notes on Processing XML Elements

23.3.1 Notes on Empty XML Elements

   XML supports two mechanisms for indicating that an XML element does
   not have any content.  The first is to declare an XML element of the
   form <A></A>.  The second is to declare an XML element of the form
   <A/>.  The two XML elements are semantically identical.

   It is a violation of the XML specification to use the <A></A> form if
   the associated DTD declares the element to be EMPTY (e.g., <!ELEMENT A
   EMPTY>).  If such a statement is included, then the empty element
   format, <A/> must be used.  If the element is not declared to be
   EMPTY, then either form <A></A> or <A/> may be used for empty elements.

23.3.2 Notes on Illegal XML Processing

   XML is a flexible data format that makes it easy to submit data that
   appears legal but in fact is not.  The philosophy of "Be flexible in
   what you accept and strict in what you send" still applies, but it
   must not be applied inappropriately.  XML is extremely flexible in
   dealing with issues of white space, element ordering, inserting new
   elements, etc.  This flexibility does not require extension,
   especially not in the area of the meaning of elements.

   There is no kindness in accepting illegal combinations of XML
   elements.  At best it will cause an unwanted result and at worst it
   can cause real damage.

23.3.2.1        Example - XML Syntax Error

   The following request body for a PROPFIND method is illegal.

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:">
      <D:allprop/>
      <D:propname/>
     </D:propfind>

   The definition of the propfind element only allows for the allprop
   or the propname element, not both.  Thus the above is an error and
   must be responded to with a 400 (Bad Request).

   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.


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   Additionally, if a server were lenient and decided to reply to this
   request, the results would vary randomly from server to server, with
   some servers executing the allprop directive, and others executing
   the propname directive. This reduces interoperability rather than
   increasing it.

23.3.2.2        Example - Unknown XML Element

   The previous example was illegal because it contained two elements
   that were explicitly banned from appearing together in the propfind
   element.  However, XML is an extensible language, so one can imagine
   new elements being defined for use with propfind.  Below is the
   request body of a PROPFIND and, like the previous example, must be
   rejected with a 400 (Bad Request) by a server that does not
   understand the expired-props element.

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:"
     xmlns:E="http://www.foo.bar/standards/props/">
      <E:expired-props/>
     </D:propfind>

   To understand why a 400 (Bad Request) is returned let us look at the
   request body as the server unfamiliar with expired-props sees it.

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:"
                 xmlns:E="http://www.foo.bar/standards/props/">
     </D:propfind>

   As the server does not understand the expired-props element,
   according to the WebDAV-specific XML processing rules specified in
   section 14, it must ignore it.  Thus the server sees an empty
   propfind, which by the definition of the propfind element is
   illegal.

   Please note that had the extension been additive it would not
   necessarily have resulted in a 400 (Bad Request).  For example,
   imagine the following request body for a PROPFIND:

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:"
                 xmlns:E="http://www.foo.bar/standards/props/">
      <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

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   server unfamiliar with leave-out, the only result would be that the
   leave-out element would be ignored and a propname would be executed.


24 Full Copyright Statement

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

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.




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