    Network Working Group                                        Y. Goland
    Request for Comments: 2518                                   Microsoft
    Category: Standards Track                                 E. Whitehead
                                                                 UC Irvine
                                                                  A. Faizi
                                                                  Netscape
                                                                 S. Carter
                                                                    Novell
                                                                 D. Jensen
                                                                    Novell
                                                             February 1999

              HTTP Extensions for Distributed Authoring -- WEBDAV

    Status of this Memo

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

    Copyright Notice

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

    Abstract

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

    Table of Contents

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

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

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

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

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

    1  Introduction

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

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

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

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

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

       Requirements and rationale for these operations are described in a
       companion document, "Requirements for a Distributed Authoring and
       Versioning Protocol for the World Wide Web" [RFC2291].

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

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

       In addition to encoding method parameters, XML is used in WebDAV to
       encode the responses from methods, providing the extensibility and
       internationalization advantages of XML for method output, as well as
       input.

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

       The XML namespace extension (Appendix 4) is also used in this
       specification in order to allow for new XML elements to be added
       without fear of colliding with other element names.

       While the status codes provided by HTTP/1.1 are sufficient to
       describe most error conditions encountered by WebDAV methods, there
       are some errors that do not fall neatly into the existing categories.
       New status codes developed for the WebDAV methods are defined in
       section 10.  Since some WebDAV methods may operate over many

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       resources, the Multi-Status response has been introduced to return
       status information for multiple resources.  The Multi-Status response
       is described in section 11.

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

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

    2  Notational Conventions

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

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

    3  Terminology

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

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

       Member URI - A URI which is a member of the set of URIs contained by
       a collection.

       Internal Member URI - A Member URI that is immediately relative to
       the URI of the collection (the definition of immediately relative is
       given in section 5.2).

       Property - A name/value pair that contains descriptive information
       about a resource.

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       Live Property - A property whose semantics and syntax are enforced by
       the server.  For example, the live "getcontentlength" property has
       its value, the length of the entity returned by a GET request,
       automatically calculated by the server.

       Dead Property - A property whose semantics and syntax are not
       enforced by the server.  The server only records the value of a dead
       property; the client is responsible for maintaining the consistency
       of the syntax and semantics of a dead property.

       Null Resource - A resource which responds with a 404 (Not Found) to
       any HTTP/1.1 or DAV method except for PUT, MKCOL, OPTIONS and LOCK.
       A NULL resource MUST NOT appear as a member of its parent collection.

    4  Data Model for Resource Properties

    4.1 The Resource Property Model

       Properties are pieces of data that describe the state of a resource.
       Properties are data about data.

       Properties are used in distributed authoring environments to provide
       for efficient discovery and management of resources.  For example, a
       'subject' property might allow for the indexing of all resources by
       their subject, and an 'author' property might allow for the discovery
       of what authors have written which documents.

       The DAV property model consists of name/value pairs.  The name of a
       property identifies the property's syntax and semantics, and provides
       an address by which to refer to its syntax and semantics.

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

    4.2 Existing Metadata Proposals

       Properties have long played an essential role in the maintenance of
       large document repositories, and many current proposals contain some
       notion of a property, or discuss web metadata more generally.  These
       include PICS [REC-PICS], PICS-NG, XML, Web Collections, and several
       proposals on representing relationships within HTML. Work on PICS-NG

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       and Web Collections has been subsumed by the Resource Description
       Framework (RDF) metadata activity of the World Wide Web Consortium.
       RDF consists of a network-based data model and an XML representation
       of that model.

       Some proposals come from a digital library perspective.  These
       include the Dublin Core [RFC2413] metadata set and the Warwick
       Framework [WF], a container architecture for different metadata
       schemas.  The literature includes many examples of metadata,
       including MARC [USMARC], a bibliographic metadata format, and a
       technical report bibliographic format employed by the Dienst system
       [RFC1807]. Additionally, the proceedings from the first IEEE Metadata
       conference describe many community-specific metadata sets.

       Participants of the 1996 Metadata II Workshop in Warwick, UK [WF],
       noted that "new metadata sets will develop as the networked
       infrastructure matures" and "different communities will propose,
       design, and be responsible for different types of metadata." These
       observations can be corroborated by noting that many community-
       specific sets of metadata already exist, and there is significant
       motivation for the development of new forms of metadata as many
       communities increasingly make their data available in digital form,
       requiring a metadata format to assist data location and cataloging.

    4.3 Properties and HTTP Headers

       Properties already exist, in a limited sense, in HTTP message
       headers.  However, in distributed authoring environments a relatively
       large number of properties are needed to describe the state of a
       resource, and setting/returning them all through HTTP headers is
       inefficient.  Thus a mechanism is needed which allows a principal to
       identify a set of properties in which the principal is interested and
       to set or retrieve just those properties.

    4.4 Property Values

       The value of a property when expressed in XML MUST be well formed.

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

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

    4.5 Property Names

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

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

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

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

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

    4.6 Media Independent Links

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

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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.

    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.

    Goland, et al.              Standards Track                    [Page 13]

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       In the absence of distributed authoring capabilities, it is
       acceptable to have no mapping of source resource(s) to the URI
       namespace. In fact, preventing access to the source resource(s) has
       desirable security benefits.  However, if remote editing of the
       source resource(s) is desired, the source resource(s) should be given
       a location in the URI namespace.  This source location should not be
       one of the locations at which the generated output is retrievable,
       since in general it is impossible for the server to differentiate
       requests for source resources from requests for process output
       resources.  There is often a many-to-many relationship between source
       resources and output resources.

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

    6  Locking

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

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

    6.1 Exclusive Vs. Shared Locks

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

    Goland, et al.              Standards Track                    [Page 14]

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       However, there are times when the goal of a lock is not to exclude
       others from exercising an access right but rather to provide a
       mechanism for principals to indicate that they intend to exercise
       their access rights.  Shared locks are provided for this case.  A
       shared lock allows multiple principals to receive a lock.  Hence any
       principal with appropriate access can get the lock.

       With shared locks there are two trust sets that affect a resource.
       The first trust set is created by access permissions.  Principals who
       are trusted, for example, may have permission to write to the
       resource.  Among those who have access permission to write to the
       resource, the set of principals who have taken out a shared lock also
       must trust each other, creating a (typically) smaller trust set
       within the access permission write set.

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

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

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

    Goland, et al.              Standards Track                    [Page 15]

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    6.2 Required Support

       A WebDAV compliant server is not required to support locking in any
       form.  If the server does support locking it may choose to support
       any combination of exclusive and shared locks for any access types.

       The reason for this flexibility is that locking policy strikes to the
       very heart of the resource management and versioning systems employed
       by various storage repositories.  These repositories require control
       over what sort of locking will be made available.  For example, some
       repositories only support shared write locks while others only
       provide support for exclusive write locks while yet others use no
       locking at all.  As each system is sufficiently different to merit
       exclusion of certain locking features, this specification leaves
       locking as the sole axis of negotiation within WebDAV.

    6.3 Lock Tokens

       A lock token is a type of state token, represented as a URI, which
       identifies a particular lock.  A lock token is returned by every
       successful LOCK operation in the lockdiscovery property in the
       response body, and can also be found through lock discovery on a
       resource.

       Lock token URIs MUST be unique across all resources for all time.
       This uniqueness constraint allows lock tokens to be submitted across
       resources and servers without fear of confusion.

       This specification provides a lock token URI scheme called
       opaquelocktoken that meets the uniqueness requirements.  However
       resources are free to return any URI scheme so long as it meets the
       uniqueness requirements.

       Having a lock token provides no special access rights. Anyone can
       find out anyone else's lock token by performing lock discovery.
       Locks MUST be enforced based upon whatever authentication mechanism
       is used by the server, not based on the secrecy of the token values.

    6.4 opaquelocktoken Lock Token URI Scheme

       The opaquelocktoken URI scheme is designed to be unique across all
       resources for all time.  Due to this uniqueness quality, a client may
       submit an opaque lock token in an If header on a resource other than
       the one that returned it.

       All resources MUST recognize the opaquelocktoken scheme and, at
       minimum, recognize that the lock token does not refer to an
       outstanding lock on the resource.

    Goland, et al.              Standards Track                    [Page 16]

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

       Opaquelocktoken generators, however, have a choice of how they create
       these tokens.  They can either generate a new UUID for every lock
       token they create or they can create a single UUID  and then add
       extension characters.  If the second method is selected then the
       program generating the extensions MUST guarantee that the same
       extension will never be used twice with the associated UUID.

       OpaqueLockToken-URI = "opaquelocktoken:" UUID [Extension]  ; The UUID
       production is the string representation of a UUID, as defined in
       [ISO-11578]. Note that white space (LWS) is not allowed between
       elements of this production.

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

    6.4.1 Node Field Generation Without the IEEE 802 Address

       UUIDs, as defined in [ISO-11578], contain a "node" field that
       contains one of the IEEE 802 addresses for the server machine.  As
       noted in section 17.8, there are several security risks associated
       with exposing a machine's IEEE 802 address. This section provides an
       alternate mechanism for generating the "node" field of a UUID which
       does not employ an IEEE 802 address.  WebDAV servers MAY use this
       algorithm for creating the node field when generating UUIDs.  The
       text in this section is originally from an Internet-Draft by Paul
       Leach and Rich Salz, who are noted here to properly attribute their
       work.

       The ideal solution is to obtain a 47 bit cryptographic quality random
       number, and use it as the low 47 bits of the node ID, with the most
       significant bit of the first octet of the node ID set to 1.  This bit
       is the unicast/multicast bit, which will never be set in IEEE 802
       addresses obtained from network cards; hence, there can never be a
       conflict between UUIDs generated by machines with and without network
       cards.

       If a system does not have a primitive to generate cryptographic
       quality random numbers, then in most systems there are usually a
       fairly large number of sources of randomness available from which one
       can be generated. Such sources are system specific, but often
       include:

    Goland, et al.              Standards Track                    [Page 17]

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         - 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
           (instructions executed, cache misses, TLB misses)

       (Note that it is precisely the above kinds of sources of randomness
       that are used to seed cryptographic quality random number generators
       on systems without special hardware for their construction.)

       In addition, items such as the computer's name and the name of the
       operating system, while not strictly speaking random, will help
       differentiate the results from those obtained by other systems.

       The exact algorithm to generate a node ID using these data is system
       specific, because both the data available and the functions to obtain
       them are often very system specific. However, assuming that one can
       concatenate all the values from the randomness sources into a buffer,
       and that a cryptographic hash function such as MD5 is available, then
       any 6 bytes of the MD5 hash of the buffer, with the multicast bit
       (the high bit of the first byte) set will be an appropriately random
       node ID.

       Other hash functions, such as SHA-1, can also be used. The only
       requirement is that the result be suitably random _ in the sense that
       the outputs from a set uniformly distributed inputs are themselves
       uniformly distributed, and that a single bit change in the input can
       be expected to cause half of the output bits to change.

    Goland, et al.              Standards Track                    [Page 18]

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    6.5 Lock Capability Discovery

       Since server lock support is optional, a client trying to lock a
       resource on a server can either try the lock and hope for the best,
       or perform some form of discovery to determine what lock capabilities
       the server supports.  This is known as lock capability discovery.
       Lock capability discovery differs from discovery of supported access
       control types, since there may be access control types without
       corresponding lock types.  A client can determine what lock types the
       server supports by retrieving the supportedlock property.

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

    6.6 Active Lock Discovery

       If another principal locks a resource that a principal wishes to
       access, it is useful for the second principal to be able to find out
       who the first principal is.  For this purpose the lockdiscovery
       property is provided.  This property lists all outstanding locks,
       describes their type, and where available, provides their lock token.

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

    6.7 Usage Considerations

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

       Two clients A and B are interested in editing the resource '
       index.html'.  Client A is an HTTP client rather than a WebDAV client,
       and so does not know how to perform locking.
       Client A doesn't lock the document, but does a GET and begins
       editing.
       Client B does LOCK, performs a GET and begins editing.
       Client B finishes editing, performs a PUT, then an UNLOCK.
       Client A performs a PUT, overwriting and losing all of B's changes.

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

    Goland, et al.              Standards Track                    [Page 19]

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

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

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

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

    7  Write Lock

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

    7.1 Methods Restricted by Write Locks

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

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

    7.2 Write Locks and Lock Tokens

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

    7.3 Write Locks and Properties

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

    Goland, et al.              Standards Track                    [Page 20]

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

    7.4 Write Locks and Null Resources

       It is possible to assert a write lock on a null resource in order to
       lock the name.

       A write locked null resource, referred to as a lock-null resource,
       MUST respond with a 404 (Not Found) or 405 (Method Not Allowed) to
       any HTTP/1.1 or DAV methods except for PUT, MKCOL, OPTIONS, PROPFIND,
       LOCK, and UNLOCK.  A lock-null resource MUST appear as a member of
       its parent collection.  Additionally the lock-null resource MUST have
       defined on it all mandatory DAV properties.  Most of these
       properties, such as all the get* properties, will have no value as a
       lock-null resource does not support the GET method.  Lock-Null
       resources MUST have defined values for lockdiscovery and
       supportedlock properties.

       Until a method such as PUT or MKCOL is successfully executed on the
       lock-null resource the resource MUST stay in the lock-null state.
       However, once a PUT or MKCOL is successfully executed on a lock-null
       resource the resource ceases to be in the lock-null state.

       If the resource is unlocked, for any reason, without a PUT, MKCOL, or
       similar method having been successfully executed upon it then the
       resource MUST return to the null state.

    7.5 Write Locks and Collections

       A write lock on a collection, whether created by a "Depth: 0" or
       "Depth: infinity" lock request, prevents the addition or removal of
       member URIs of the collection by non-lock owners.  As a consequence,
       when a principal issues a PUT or POST request to create a new
       resource under a URI which needs to be an internal member of a write
       locked collection to maintain HTTP namespace consistency, or issues a
       DELETE to remove a resource which has a URI which is an existing
       internal member URI of a write locked collection, this request MUST
       fail if the principal does not have a write lock on the collection.

       However, if a write lock request is issued to a collection containing
       member URIs identifying resources that are currently locked in a
       manner which conflicts with the write lock, the request MUST fail
       with a 423 (Locked) status code.

       If a lock owner causes the URI of a resource to be added as an
       internal member URI of a locked collection then the new resource MUST
       be automatically added to the lock.  This is the only mechanism that

    Goland, et al.              Standards Track                    [Page 21]

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

    7.6 Write Locks and the If Request Header

       If a user agent is not required to have knowledge about a lock when
       requesting an operation on a locked resource, the following scenario
       might occur.  Program A, run by User A, takes out a write lock on a
       resource.  Program B, also run by User A, has no knowledge of the
       lock taken out by Program A, yet performs a PUT to the locked
       resource.  In this scenario, the PUT succeeds because locks are
       associated with a principal, not a program, and thus program B,
       because it is acting with principal A's credential, is allowed to
       perform the PUT.  However, had program B known about the lock, it
       would not have overwritten the resource, preferring instead to
       present a dialog box describing the conflict to the user.  Due to
       this scenario, a mechanism is needed to prevent different programs
       from accidentally ignoring locks taken out by other programs with the
       same authorization.

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

    7.6.1 Example - Write Lock

       >>Request

       COPY /~fielding/index.html HTTP/1.1
       Host: www.ics.uci.edu
       Destination: http://www.ics.uci.edu/users/f/fielding/index.html
       If: <http://www.ics.uci.edu/users/f/fielding/index.html>
           (<opaquelocktoken:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>)

       >>Response

       HTTP/1.1 204 No Content

       In this example, even though both the source and destination are
       locked, only one lock token must be submitted, for the lock on the
       destination.  This is because the source resource is not modified by
       a COPY, and hence unaffected by the write lock. In this example, user
       agent authentication has previously occurred via a mechanism outside
       the scope of the HTTP protocol, in the underlying transport layer.

    Goland, et al.              Standards Track                    [Page 22]

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    7.7 Write Locks and COPY/MOVE

       A COPY method invocation MUST NOT duplicate any write locks active on
       the source.  However, as previously noted, if the COPY copies the
       resource into a collection that is locked with "Depth: infinity",
       then the resource will be added to the lock.

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

    7.8 Refreshing Write Locks

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

       However, a client may submit a LOCK method with an If header but
       without a body.  This form of LOCK MUST only be used to "refresh" a
       lock.  Meaning, at minimum, that any timers associated with the lock
       MUST be re-set.

       A server may return a Timeout header with a lock refresh that is
       different than the Timeout header returned when the lock was
       originally requested.  Additionally clients may submit Timeout
       headers of arbitrary value with their lock refresh requests.
       Servers, as always, may ignore Timeout headers submitted by the
       client.

       If an error is received in response to a refresh LOCK request the
       client SHOULD assume that the lock was not refreshed.

    8  HTTP Methods for Distributed Authoring

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

    Goland, et al.              Standards Track                    [Page 23]

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

    8.1 PROPFIND

       The PROPFIND method retrieves properties defined on the resource
       identified by the Request-URI, if the resource does not have any
       internal members, or on the resource identified by the Request-URI
       and potentially its member resources, if the resource is a collection
       that has internal member URIs.  All DAV compliant resources MUST
       support the PROPFIND method and the propfind XML element (section
       12.14) along with all XML elements defined for use with that element.

       A client may submit a Depth header with a value of "0", "1", or
       "infinity" with a PROPFIND on a collection resource with internal
       member URIs.  DAV compliant servers MUST support the "0", "1" and
       "infinity" behaviors. By default, the PROPFIND method without a Depth
       header MUST act as if a "Depth: infinity" header was included.

       A client may submit a propfind XML element in the body of the request
       method describing what information is being requested.  It is
       possible to request particular property values, all property values,
       or a list of the names of the resource's properties.  A client may
       choose not to submit a request body.  An empty PROPFIND request body
       MUST be treated as a request for the names and values of all
       properties.

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

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

       Consequently, the multistatus XML element for a collection resource
       with member URIs MUST include a response XML element for each member
       URI of the collection, to whatever depth was requested. Each response
       XML element MUST contain an href XML element that gives the URI of
       the resource on which the properties in the prop XML element are
       defined.  Results for a PROPFIND on a collection resource with
       internal member URIs are returned as a flat list whose order of
       entries is not significant.

    Goland, et al.              Standards Track                    [Page 24]

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

       The results of this method SHOULD NOT be cached.

    8.1.1 Example - Retrieving Named Properties

       >>Request

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

       <?xml version="1.0" encoding="utf-8" ?>
       <D:propfind xmlns:D="DAV:">
         <D:prop xmlns:R="http://www.foo.bar/boxschema/">
              <R:bigbox/>
              <R:author/>
              <R:DingALing/>
              <R:Random/>
         </D:prop>
       </D:propfind>

       >>Response

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

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

    Goland, et al.              Standards Track                    [Page 25]

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

       In this example, PROPFIND is executed on a non-collection resource
       http://www.foo.bar/file.  The propfind XML element specifies the name
       of four properties whose values are being requested. In this case
       only two properties were returned, since the principal issuing the
       request did not have sufficient access rights to see the third and
       fourth properties.

    8.1.2 Example - Using allprop to Retrieve All Properties

       >>Request

       PROPFIND  /container/ HTTP/1.1
       Host: www.foo.bar
       Depth: 1
       Content-Type: text/xml; charset="utf-8"
       Content-Length: xxxx

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

       >>Response

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

       <?xml version="1.0" encoding="utf-8" ?>
       <D:multistatus xmlns:D="DAV:">
         <D:response>
              <D:href>http://www.foo.bar/container/</D:href>
              <D:propstat>
                   <D:prop xmlns:R="http://www.foo.bar/boxschema/">
                        <R:bigbox>
                             <R:BoxType>Box type A</R:BoxType>
                        </R:bigbox>
                        <R:author>

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

    Goland, et al.              Standards Track                    [Page 27]

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                        <D:resourcetype/>
                        <D:supportedlock>
                             <D:lockentry>
                                  <D:lockscope><D:exclusive/></D:lockscope>
                                  <D:locktype><D:write/></D:locktype>
                             </D:lockentry>
                             <D:lockentry>
                                  <D:lockscope><D:shared/></D:lockscope>
                                  <D:locktype><D:write/></D:locktype>
                             </D:lockentry>
                        </D:supportedlock>
                   </D:prop>
                   <D:status>HTTP/1.1 200 OK</D:status>
              </D:propstat>
         </D:response>
       </D:multistatus>

       In this example, PROPFIND was invoked on the resource
       http://www.foo.bar/container/ with a Depth header of 1, meaning the
       request applies to the resource and its children, and a propfind XML
       element containing the allprop XML element, meaning the request
       should return the name and value of all properties defined on each
       resource.

       The resource http://www.foo.bar/container/ has six properties defined
       on it:

       http://www.foo.bar/boxschema/bigbox,
       http://www.foo.bar/boxschema/author, DAV:creationdate,
       DAV:displayname, DAV:resourcetype, and DAV:supportedlock.

       The last four properties are WebDAV-specific, defined in section 13.
       Since GET is not supported on this resource, the get* properties
       (e.g., getcontentlength) are not defined on this resource. The DAV-
       specific properties assert that "container" was created on December
       1, 1997, at 5:42:21PM, in a time zone 8 hours west of GMT
       (creationdate), has a name of "Example collection" (displayname), a
       collection resource type (resourcetype), and supports exclusive write
       and shared write locks (supportedlock).

       The resource http://www.foo.bar/container/front.html has nine
       properties defined on it:

       http://www.foo.bar/boxschema/bigbox (another instance of the "bigbox"
       property type), DAV:creationdate, DAV:displayname,
       DAV:getcontentlength, DAV:getcontenttype, DAV:getetag,
       DAV:getlastmodified, DAV:resourcetype, and DAV:supportedlock.

    Goland, et al.              Standards Track                    [Page 28]

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       The DAV-specific properties assert that "front.html" was created on
       December 1, 1997, at 6:27:21PM, in a time zone 8 hours west of GMT
       (creationdate), has a name of "Example HTML resource" (displayname),
       a content length of 4525 bytes (getcontentlength), a MIME type of
       "text/html" (getcontenttype), an entity tag of "zzyzx" (getetag), was
       last modified on Monday, January 12, 1998, at 09:25:56 GMT
       (getlastmodified), has an empty resource type, meaning that it is not
       a collection (resourcetype), and supports both exclusive write and
       shared write locks (supportedlock).

    8.1.3 Example - Using propname to Retrieve all Property Names

       >>Request

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

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

       >>Response

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

       <?xml version="1.0" encoding="utf-8" ?>
       <multistatus xmlns="DAV:">
         <response>
              <href>http://www.foo.bar/container/</href>
              <propstat>
                   <prop xmlns:R="http://www.foo.bar/boxschema/">
                        <R:bigbox/>
                        <R:author/>
                        <creationdate/>
                        <displayname/>
                        <resourcetype/>
                        <supportedlock/>
                   </prop>
                   <status>HTTP/1.1 200 OK</status>
              </propstat>
         </response>
         <response>
              <href>http://www.foo.bar/container/front.html</href>

    Goland, et al.              Standards Track                    [Page 29]

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              <propstat>
                   <prop xmlns:R="http://www.foo.bar/boxschema/">
                        <R:bigbox/>
                        <creationdate/>
                        <displayname/>
                        <getcontentlength/>
                        <getcontenttype/>
                        <getetag/>
                        <getlastmodified/>
                        <resourcetype/>
                        <supportedlock/>
                   </prop>
                   <status>HTTP/1.1 200 OK</status>
              </propstat>
         </response>
       </multistatus>

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

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

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

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

    Goland, et al.              Standards Track                    [Page 30]

    RFC 2518                         WEBDAV                    February 1999

    8.2 PROPPATCH

       The PROPPATCH method processes instructions specified in the request
       body to set and/or remove properties defined on the resource
       identified by the Request-URI.

       All DAV compliant resources MUST support the PROPPATCH method and
       MUST process instructions that are specified using the
       propertyupdate, set, and remove XML elements of the DAV schema.
       Execution of the directives in this method is, of course, subject to
       access control constraints.  DAV compliant resources SHOULD support
       the setting of arbitrary dead properties.

       The request message body of a PROPPATCH method MUST contain the
       propertyupdate XML element.  Instruction processing MUST occur in the
       order instructions are received (i.e., from top to bottom).
       Instructions MUST either all be executed or none executed. Thus if
       any error occurs during processing all executed instructions MUST be
       undone and a proper error result returned. Instruction processing
       details can be found in the definition of the set and remove
       instructions in section 12.13.

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

       The following are examples of response codes one would expect to be
       used in a 207 (Multi-Status) response for this method.  Note,
       however, that unless explicitly prohibited any 2/3/4/5xx series
       response code may be used in a 207 (Multi-Status) response.

       200 (OK) - The command succeeded.  As there can be a mixture of sets
       and removes in a body, a 201 (Created) seems inappropriate.

       403 (Forbidden) - The client, for reasons the server chooses not to
       specify, cannot alter one of the properties.

       409 (Conflict) - The client has provided a value whose semantics are
       not appropriate for the property.  This includes trying to set read-
       only properties.

       423 (Locked) - The specified resource is locked and the client either
       is not a lock owner or the lock type requires a lock token to be
       submitted and the client did not submit it.

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

    Goland, et al.              Standards Track                    [Page 31]

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    8.2.2 Example - PROPPATCH

       >>Request

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

       <?xml version="1.0" encoding="utf-8" ?>
       <D:propertyupdate xmlns:D="DAV:"
       xmlns:Z="http://www.w3.com/standards/z39.50/">
         <D:set>
              <D:prop>
                   <Z:authors>
                        <Z:Author>Jim Whitehead</Z:Author>
                        <Z:Author>Roy Fielding</Z:Author>
                   </Z:authors>
              </D:prop>
         </D:set>
         <D:remove>
              <D:prop><Z:Copyright-Owner/></D:prop>
         </D:remove>
       </D:propertyupdate>

       >>Response

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

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

    Goland, et al.              Standards Track                    [Page 32]

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

    8.3 MKCOL Method

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

    8.3.1 Request

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

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

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

    8.3.2 Status Codes

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

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

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    RFC 2518                         WEBDAV                    February 1999

       403 (Forbidden) - This indicates at least one of two conditions: 1)
       the server does not allow the creation of collections at the given
       location in its namespace, or 2) the parent collection of the
       Request-URI exists but cannot accept members.

       405 (Method Not Allowed) - MKCOL can only be executed on a
       deleted/non-existent resource.

       409 (Conflict) - A collection cannot be made at the Request-URI until
       one or more intermediate collections have been created.

       415 (Unsupported Media Type)- The server does not support the request
       type of the body.

       507 (Insufficient Storage) - The resource does not have sufficient
       space to record the state of the resource after the execution of this
       method.

    8.3.3 Example - MKCOL

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

       >>Request

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

       >>Response

       HTTP/1.1 201 Created

    8.4 GET, HEAD for Collections

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

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

    Goland, et al.              Standards Track                    [Page 34]

    RFC 2518                         WEBDAV                    February 1999

    8.5 POST for Collections

       Since by definition the actual function performed by POST is
       determined by the server and often depends on the particular
       resource, the behavior of POST when applied to collections cannot be
       meaningfully modified because it is largely undefined.  Thus the
       semantics of POST are unmodified when applied to a collection.

    8.6 DELETE

       8.6.1 DELETE for Non-Collection Resources

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

    8.6.2 DELETE for Collections

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

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

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

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

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

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

    Goland, et al.              Standards Track                    [Page 35]

    RFC 2518                         WEBDAV                    February 1999

    8.6.2.1 Example - DELETE

       >>Request

       DELETE  /container/ HTTP/1.1
       Host: www.foo.bar

       >>Response

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

       <?xml version="1.0" encoding="utf-8" ?>
       <d:multistatus xmlns:d="DAV:">
         <d:response>
              <d:href>http://www.foo.bar/container/resource3</d:href>
              <d:status>HTTP/1.1 423 Locked</d:status>
         </d:response>
       </d:multistatus>

       In this example the attempt to delete
       http://www.foo.bar/container/resource3 failed because it is locked,
       and no lock token was submitted with the request. Consequently, the
       attempt to delete http://www.foo.bar/container/ also failed. Thus the
       client knows that the attempt to delete http://www.foo.bar/container/
       must have also failed since the parent can not be deleted unless its
       child has also been deleted.  Even though a Depth header has not been
       included, a depth of infinity is assumed because the method is on a
       collection.

    8.7 PUT

    8.7.1 PUT for Non-Collection Resources

       A PUT performed on an existing resource replaces the GET response
       entity of the resource.  Properties defined on the resource may be
       recomputed during PUT processing but are not otherwise affected.  For
       example, if a server recognizes the content type of the request body,
       it may be able to automatically extract information that could be
       profitably exposed as properties.

       A PUT that would result in the creation of a resource without an
       appropriately scoped parent collection MUST fail with a 409
       (Conflict).

    Goland, et al.              Standards Track                    [Page 36]

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    8.7.2 PUT for Collections

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

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

    8.8 COPY Method

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

       All WebDAV compliant resources MUST support the COPY method.
       However, support for the COPY method does not guarantee the ability
       to copy a resource. For example, separate programs may control
       resources on the same server.  As a result, it may not be possible to
       copy a resource to a location that appears to be on the same server.

    8.8.1 COPY for HTTP/1.1 resources

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

    Goland, et al.              Standards Track                    [Page 37]

    RFC 2518                         WEBDAV                    February 1999

    8.8.2. COPY for Properties

       The following section defines how properties on a resource are
       handled during a COPY operation.

       Live properties SHOULD be duplicated as identically behaving live
       properties at the destination resource.  If a property cannot be
       copied live, then its value MUST be duplicated, octet-for-octet, in
       an identically named, dead property on the destination resource
       subject to the effects of the propertybehavior XML element.

       The propertybehavior XML element can specify that properties are
       copied on best effort, that all live properties must be successfully
       copied or the method must fail, or that a specified list of live
       properties must be successfully copied or the method must fail. The
       propertybehavior XML element is defined in section 12.12.

    8.8.3 COPY for Collections

       The COPY method on a collection without a Depth header MUST act as if
       a Depth header with value "infinity" was included.  A client may
       submit a Depth header on a COPY on a collection with a value of "0"
       or "infinity".  DAV compliant servers MUST support the "0" and
       "infinity" Depth header behaviors.

       A COPY of depth infinity instructs that the collection resource
       identified by the Request-URI is to be copied to the location
       identified by the URI in the Destination header, and all its internal
       member resources are to be copied to a location relative to it,
       recursively through all levels of the collection hierarchy.

       A COPY of "Depth: 0" only instructs that the collection and its
       properties but not resources identified by its internal member URIs,
       are to be copied.

       Any headers included with a COPY MUST be applied in processing every
       resource to be copied with the exception of the Destination header.

       The Destination header only specifies the destination URI for the
       Request-URI. When applied to members of the collection identified by
       the Request-URI the value of Destination is to be modified to reflect
       the current location in the hierarchy.  So, if the Request- URI is
       /a/ with Host header value http://fun.com/ and the Destination is
       http://fun.com/b/ then when http://fun.com/a/c/d is processed it must
       use a Destination of http://fun.com/b/c/d.

    Goland, et al.              Standards Track                    [Page 38]

    RFC 2518                         WEBDAV                    February 1999

       When the COPY method has completed processing it MUST have created a
       consistent namespace at the destination (see section 5.1 for the
       definition of namespace consistency).  However, if an error occurs
       while copying an internal collection, the server MUST NOT copy any
       resources identified by members of this collection (i.e., the server
       must skip this subtree), as this would create an inconsistent
       namespace. After detecting an error, the COPY operation SHOULD try to
       finish as much of the original copy operation as possible (i.e., the
       server should still attempt to copy other subtrees and their members,
       that are not descendents of an error-causing collection).  So, for
       example, if an infinite depth copy operation is performed on
       collection /a/, which contains collections /a/b/ and /a/c/, and an
       error occurs copying /a/b/, an attempt should still be made to copy
       /a/c/. Similarly, after encountering an error copying a non-
       collection resource as part of an infinite depth copy, the server
       SHOULD try to finish as much of the original copy operation as
       possible.

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

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

    8.8.4 COPY and the Overwrite Header

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

    8.8.5 Status Codes

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

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

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

    Goland, et al.              Standards Track                    [Page 39]

    RFC 2518                         WEBDAV                    February 1999

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

       412 (Precondition Failed) - The server was unable to maintain the
       liveness of the properties listed in the propertybehavior XML element
       or the Overwrite header is "F" and the state of the destination
       resource is non-null.

       423 (Locked) - The destination resource was locked.

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

       507 (Insufficient Storage) - The destination resource does not have
       sufficient space to record the state of the resource after the
       execution of this method.

    8.8.6 Example - COPY with Overwrite

       This example shows resource
       http://www.ics.uci.edu/~fielding/index.html being copied to the
       location http://www.ics.uci.edu/users/f/fielding/index.html.  The 204
       (No Content) status code indicates the existing resource at the
       destination was overwritten.

       >>Request

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

       >>Response

       HTTP/1.1 204 No Content

    8.8.7 Example - COPY with No Overwrite

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

       >>Request

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

    Goland, et al.              Standards Track                    [Page 40]

    RFC 2518                         WEBDAV                    February 1999

       >>Response

       HTTP/1.1 412 Precondition Failed

    8.8.8 Example - COPY of a Collection

          >>Request

          COPY /container/ HTTP/1.1
          Host: www.foo.bar
          Destination: http://www.foo.bar/othercontainer/
          Depth: infinity
          Content-Type: text/xml; charset="utf-8"
          Content-Length: xxxx

          <?xml version="1.0" encoding="utf-8" ?>
          <d:propertybehavior xmlns:d="DAV:">
            <d:keepalive>*</d:keepalive>
          </d:propertybehavior>

          >>Response

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

          <?xml version="1.0" encoding="utf-8" ?>
          <d:multistatus xmlns:d="DAV:">
            <d:response>
                 <d:href>http://www.foo.bar/othercontainer/R2/</d:href>
                 <d:status>HTTP/1.1 412 Precondition Failed</d:status>
            </d:response>
          </d:multistatus>

       The Depth header is unnecessary as the default behavior of COPY on a
       collection is to act as if a "Depth: infinity" header had been
       submitted.  In this example most of the resources, along with the
       collection, were copied successfully. However the collection R2
       failed, most likely due to a problem with maintaining the liveness of
       properties (this is specified by the propertybehavior XML element).
       Because there was an error copying R2, none of R2's members were
       copied.  However no errors were listed for those members due to the
       error minimization rules given in section 8.8.3.

    Goland, et al.              Standards Track                    [Page 41]

    RFC 2518                         WEBDAV                    February 1999

    8.9 MOVE Method

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

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

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

    8.9.1 MOVE for Properties

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

    8.9.2 MOVE for Collections

       A MOVE with "Depth: infinity" instructs that the collection
       identified by the Request-URI be moved to the URI specified in the
       Destination header, and all resources identified by its internal
       member URIs are to be moved to locations relative to it, recursively
       through all levels of the collection hierarchy.

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

       Any headers included with MOVE MUST be applied in processing every
       resource to be moved with the exception of the Destination header.

       The behavior of the Destination header is the same as given for COPY
       on collections.

    Goland, et al.              Standards Track                    [Page 42]

    RFC 2518                         WEBDAV                    February 1999

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

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

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

    8.9.3 MOVE and the Overwrite Header

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

    8.9.4 Status Codes

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

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

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

    Goland, et al.              Standards Track                    [Page 43]

    RFC 2518                         WEBDAV                    February 1999

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

       412 (Precondition Failed) - The server was unable to maintain the
       liveness of the properties listed in the propertybehavior XML element
       or the Overwrite header is "F" and the state of the destination
       resource is non-null.

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

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

    8.9.5 Example - MOVE of a Non-Collection

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

       >>Request

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

       >>Response

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

    8.9.6 Example - MOVE of a Collection

       >>Request

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

    Goland, et al.              Standards Track                    [Page 44]

    RFC 2518                         WEBDAV                    February 1999

       <?xml version="1.0" encoding="utf-8" ?>
       <d:propertybehavior xmlns:d='DAV:'>
         <d:keepalive>*</d:keepalive>
       </d:propertybehavior>

       >>Response

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

       <?xml version="1.0" encoding="utf-8" ?>
       <d:multistatus xmlns:d='DAV:'>
         <d:response>
              <d:href>http://www.foo.bar/othercontainer/C2/</d:href>
              <d:status>HTTP/1.1 423 Locked</d:status>
         </d:response>
       </d:multistatus>

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

    8.10 LOCK Method

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

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

    Goland, et al.              Standards Track                    [Page 45]

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    8.10.1 Operation

       A LOCK method invocation creates the lock specified by the lockinfo
       XML element on the Request-URI.  Lock method requests SHOULD have a
       XML request body which contains an owner XML element for this lock
       request, unless this is a refresh request. The LOCK request may have
       a Timeout header.

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

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

    8.10.2 The Effect of Locks on Properties and Collections

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

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

    8.10.3 Locking Replicated Resources

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

    8.10.4 Depth and Locking

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

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

    Goland, et al.              Standards Track                    [Page 46]

    RFC 2518                         WEBDAV                    February 1999

       If the Depth header is set to infinity then the resource specified in
       the Request-URI along with all its internal members, all the way down
       the hierarchy, are to be locked.  A successful result MUST return a
       single lock token which represents all the resources that have been
       locked.  If an UNLOCK is successfully executed on this token, all
       associated resources are unlocked.  If the lock cannot be granted to
       all resources, a 409 (Conflict) status code MUST be returned with a
       response entity body containing a multistatus XML element describing
       which resource(s) prevented the lock from being granted.  Hence,
       partial success is not an option.  Either the entire hierarchy is
       locked or no resources are locked.

       If no Depth header is submitted on a LOCK request then the request
       MUST act as if a "Depth:infinity" had been submitted.

    8.10.5 Interaction with other Methods

       The interaction of a LOCK with various methods is dependent upon the
       lock type.  However, independent of lock type, a successful DELETE of
       a resource MUST cause all of its locks to be removed.

    8.10.6 Lock Compatibility Table

       The table below describes the behavior that occurs when a lock
       request is made on a resource.

       Current lock state/  |   Shared Lock   |   Exclusive
       Lock request         |                 |   Lock
       =====================+=================+==============
       None                 |   True          |   True
       ---------------------+-----------------+--------------
       Shared Lock          |   True          |   False
       ---------------------+-----------------+--------------
       Exclusive Lock       |   False         |   False*
       ------------------------------------------------------

       Legend: True = lock may be granted.  False = lock MUST NOT be
       granted. *=It is illegal for a principal to request the same lock
       twice.

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

    Goland, et al.              Standards Track                    [Page 47]

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    8.10.7 Status Codes

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

       412 (Precondition Failed) - The included lock token was not
       enforceable on this resource or the server could not satisfy the
       request in the lockinfo XML element.

       423 (Locked) - The resource is locked, so the method has been
       rejected.

    8.10.8 Example - Simple Lock Request

       >>Request

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

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

       >>Response

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

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

    Goland, et al.              Standards Track                    [Page 48]

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                   <D:owner>
                        <D:href>
                             http://www.ics.uci.edu/~ejw/contact.html
                        </D:href>
                   </D:owner>
                   <D:timeout>Second-604800</D:timeout>
                   <D:locktoken>
                        <D:href>
                   opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4
                        </D:href>
                   </D:locktoken>
              </D:activelock>
         </D:lockdiscovery>
       </D:prop>

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

    8.10.9 Example - Refreshing a Write Lock

       >>Request

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

       >>Response

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

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

    Goland, et al.              Standards Track                    [Page 49]

    RFC 2518                         WEBDAV                    February 1999

                   <D:lockscope><D:exclusive/></D:lockscope>
                   <D:depth>Infinity</D:depth>
                   <D:owner>
                        <D:href>
                        http://www.ics.uci.edu/~ejw/contact.html
                        </D:href>
                   </D:owner>
                   <D:timeout>Second-604800</D:timeout>
                   <D:locktoken>
                        <D:href>
                   opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4
                        </D:href>
                   </D:locktoken>
              </D:activelock>
         </D:lockdiscovery>
       </D:prop>

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

    8.10.10 Example - Multi-Resource Lock Request

       >>Request

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

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

       >>Response

    Goland, et al.              Standards Track                    [Page 50]

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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://webdav.sb.aol.com/webdav/secret</D:href>
              <D:status>HTTP/1.1 403 Forbidden</D:status>
         </D:response>
         <D:response>
              <D:href>http://webdav.sb.aol.com/webdav/</D:href>
              <D:propstat>
                   <D:prop><D:lockdiscovery/></D:prop>
                   <D:status>HTTP/1.1 424 Failed Dependency</D:status>
              </D:propstat>
         </D:response>
       </D:multistatus>

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

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

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

    8.11 UNLOCK Method

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

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

    Goland, et al.              Standards Track                    [Page 51]

    RFC 2518                         WEBDAV                    February 1999

    8.11.1 Example - UNLOCK

       >>Request

       UNLOCK /workspace/webdav/info.doc HTTP/1.1
       Host: webdav.sb.aol.com
       Lock-Token: <opaquelocktoken:a515cfa4-5da4-22e1-f5b5-00a0451e6bf7>
       Authorization: Digest username="ejw",
          realm="ejw@webdav.sb.aol.com", nonce="...",
          uri="/workspace/webdav/proposal.doc",
          response="...", opaque="..."

       >>Response

       HTTP/1.1 204 No Content

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

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

    9  HTTP Headers for Distributed Authoring

    9.1 DAV Header

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

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

       The value is a list of all compliance classes that the resource
       supports.  Note that above a comma has already been added to the 2.
       This is because a resource can not be level 2 compliant unless it is
       also level 1 compliant. Please refer to section 15 for more details.
       In general, however, support for one compliance class does not entail
       support for any other.

    9.2 Depth Header

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

    Goland, et al.              Standards Track                    [Page 52]

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       The Depth header is used with methods executed on resources which
       could potentially have internal members to indicate whether the
       method is to be applied only to the resource ("Depth: 0"), to the
       resource and its immediate children, ("Depth: 1"), or the resource
       and all its progeny ("Depth: infinity").

       The Depth header is only supported if a method's definition
       explicitly provides for such support.

       The following rules are the default behavior for any method that
       supports the Depth header. A method may override these defaults by
       defining different behavior in its definition.

       Methods which support the Depth header may choose not to support all
       of the header's values and may define, on a case by case basis, the
       behavior of the method if a Depth header is not present. For example,
       the MOVE method only supports "Depth: infinity" and if a Depth header
       is not present will act as if a "Depth: infinity" header had been
       applied.

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

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

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

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

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

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

    Goland, et al.              Standards Track                    [Page 53]

    RFC 2518                         WEBDAV                    February 1999

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

    9.3 Destination Header

       Destination = "Destination" ":" absoluteURI

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

    9.4 If Header

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

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

       All DAV compliant resources MUST honor the If header.

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

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

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    9.4.1 No-tag-list Production

       The No-tag-list production describes a series of state tokens and
       ETags.  If multiple No-tag-list productions are used then one only
       needs to match the state of the resource for the method to be allowed
       to continue.

       If a method, due to the presence of a Depth or Destination header, is
       applied to multiple resources then the No-tag-list production MUST be
       applied to each resource the method is applied to.

    9.4.1.1 Example - No-tag-list If Header

       If: (<locktoken:a-write-lock-token> ["I am an ETag"]) (["I am another
       ETag"])

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

    9.4.2 Tagged-list Production

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

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

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

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    9.4.2.1 Example - Tagged List If header

       COPY /resource1 HTTP/1.1
       Host: www.foo.bar
       Destination: http://www.foo.bar/resource2
       If: <http://www.foo.bar/resource1> (<locktoken:a-write-lock-token>
       [W/"A weak ETag"]) (["strong ETag"])
       <http://www.bar.bar/random>(["another strong ETag"])

       In this example http://www.foo.bar/resource1 is being copied to
       http://www.foo.bar/resource2.  When the method is first applied to
       http://www.foo.bar/resource1, resource1 must be in the state
       specified by "(<locktoken:a-write-lock-token> [W/"A weak ETag"])
       (["strong ETag"])", that is, it either must be locked with a lock
       token of "locktoken:a-write-lock-token" and have a weak entity tag
       W/"A weak ETag" or it must have a strong entity tag "strong ETag".

       That is the only success condition since the resource
       http://www.bar.bar/random never has the method applied to it (the
       only other resource listed in the If header) and
       http://www.foo.bar/resource2 is not listed in the If header.

    9.4.3 not Production

       Every state token or ETag is either current, and hence describes the
       state of a resource, or is not current, and does not describe the
       state of a resource. The boolean operation of matching a state token
       or ETag to the current state of a resource thus resolves to a true or
       false value.  The not production is used to reverse that value.  The
       scope of the not production is the state-token or entity-tag
       immediately following it.

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

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

    9.4.4 Matching Function

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

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

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

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    9.4.5 If Header and Non-DAV Compliant Proxies

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

    9.5 Lock-Token Header

       Lock-Token = "Lock-Token" ":" Coded-URL

       The Lock-Token request header is used with the UNLOCK method to
       identify the lock to be removed.  The lock token in the Lock-Token
       request header MUST identify a lock that contains the resource
       identified by Request-URI as a member.

       The Lock-Token response header is used with the LOCK method to
       indicate the lock token created as a result of a successful LOCK
       request to create a new lock.

    9.6 Overwrite Header

       Overwrite = "Overwrite" ":" ("T" | "F")

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

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

       All DAV compliant resources MUST support the Overwrite header.

    9.7 Status-URI Response Header

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

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

       The URIs listed in the header are source resources which have been
       affected by the outstanding method.  The status code indicates the
       resolution of the method on the identified resource.  So, for
       example, if a MOVE method on a collection is outstanding and a 102
       (Processing) response with a Status-URI response header is returned,
       the included URIs will indicate resources that have had move
       attempted on them and what the result was.

    9.8 Timeout Request Header

       TimeOut = "Timeout" ":" 1#TimeType
       TimeType = ("Second-" DAVTimeOutVal | "Infinite" | Other)
       DAVTimeOutVal = 1*digit
       Other = "Extend" field-value   ; See section 4.2 of [RFC2068]

       Clients may include Timeout headers in their LOCK requests.  However,
       the server is not required to honor or even consider these requests.
       Clients MUST NOT submit a Timeout request header with any method
       other than a LOCK method.

       A Timeout request header MUST contain at least one TimeType and may
       contain multiple TimeType entries. The purpose of listing multiple
       TimeType entries is to indicate multiple different values and value
       types that are acceptable to the client.  The client lists the
       TimeType entries in order of preference.

       Timeout response values MUST use a Second value, Infinite, or a
       TimeType the client has indicated familiarity with.  The server may
       assume a client is familiar with any TimeType submitted in a Timeout
       header.

       The "Second" TimeType specifies the number of seconds that will
       elapse between granting of the lock at the server, and the automatic
       removal of the lock.  The timeout value for TimeType "Second" MUST
       NOT be greater than 2^32-1.

       The timeout counter SHOULD be restarted any time an owner of the lock
       sends a method to any member of the lock, including unsupported
       methods, or methods which are unsuccessful.  However the lock MUST be
       refreshed if a refresh LOCK method is successfully received.

       If the timeout expires then the lock may be lost.  Specifically, if
       the server wishes to harvest the lock upon time-out, the server
       SHOULD act as if an UNLOCK method was executed by the server on the
       resource using the lock token of the timed-out lock, performed with

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       its override authority. Thus logs should be updated with the
       disposition of the lock, notifications should be sent, etc., just as
       they would be for an UNLOCK request.

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

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

    10 Status Code Extensions to HTTP/1.1

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

    10.1 102 Processing

       The 102 (Processing) status code is an interim response used to
       inform the client that the server has accepted the complete request,
       but has not yet completed it.  This status code SHOULD only be sent
       when the server has a reasonable expectation that the request will
       take significant time to complete. As guidance, if a method is taking
       longer than 20 seconds (a reasonable, but arbitrary value) to process
       the server SHOULD return a 102 (Processing) response. The server MUST
       send a final response after the request has been completed.

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

    10.2 207 Multi-Status

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

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    10.3 422 Unprocessable Entity

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

    10.4 423 Locked

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

    10.5 424 Failed Dependency

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

    10.6 507 Insufficient Storage

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

    11 Multi-Status Response

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

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    12 XML Element Definitions

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

    12.1 activelock XML Element

       Name:       activelock
       Namespace:  DAV:
       Purpose:    Describes a lock on a resource.

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

    12.1.1 depth XML Element

       Name:       depth
       Namespace:  DAV:
       Purpose:    The value of the Depth header.
       Value:      "0" | "1" | "infinity"

       <!ELEMENT depth (#PCDATA) >

    12.1.2 locktoken XML Element

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

       <!ELEMENT locktoken (href+) >

    12.1.3 timeout XML Element

       Name:       timeout
       Namespace:  DAV:
       Purpose:    The timeout associated with a lock
       Value:      TimeType ;Defined in section 9.8

       <!ELEMENT timeout (#PCDATA) >

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    12.2 collection XML Element

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

       <!ELEMENT collection EMPTY >

    12.3 href XML Element

       Name:       href
       Namespace:  DAV:
       Purpose:    Identifies the content of the element as a URI.
       Value:      URI ; See section 3.2.1 of [RFC2068]

       <!ELEMENT href (#PCDATA)>

    12.4 link XML Element

       Name:       link
       Namespace:  DAV:
       Purpose:    Identifies the property as a link and contains the source
       and destination of that link.
       Description: The link XML element is used to provide the sources and
       destinations of a link.  The name of the property containing the link
       XML element provides the type of the link.  Link is a multi-valued
       element, so multiple links may be used together to indicate multiple
       links with the same type.  The values in the href XML elements inside
       the src and dst XML elements of the link XML element MUST NOT be
       rejected if they point to resources which do not exist.

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

    12.4.1 dst XML Element

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

       <!ELEMENT dst (#PCDATA) >

    12.4.2 src XML Element

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

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       Value:      URI

       <!ELEMENT src (#PCDATA) >

    12.5 lockentry XML Element

       Name:       lockentry
       Namespace:  DAV:
       Purpose:    Defines the types of locks that can be used with the
       resource.

       <!ELEMENT lockentry (lockscope, locktype) >

    12.6 lockinfo XML Element

       Name:       lockinfo
       Namespace:  DAV:
       Purpose:    The lockinfo XML element is used with a LOCK method to
       specify the type of lock the client wishes to have created.

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

    12.7 lockscope XML Element

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

       <!ELEMENT lockscope (exclusive | shared) >

    12.7.1 exclusive XML Element

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

       <!ELEMENT exclusive EMPTY >

    12.7.2 shared XML Element

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

       <!ELEMENT shared EMPTY >

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    12.8 locktype XML Element

       Name:       locktype
       Namespace:  DAV:
       Purpose:    Specifies the access type of a lock.  At present, this
       specification only defines one lock type, the write lock.

       <!ELEMENT locktype (write) >

    12.8.1 write XML Element

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

       <!ELEMENT write EMPTY >

    12.9 multistatus XML Element

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

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

    12.9.1 response XML Element

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

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

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    12.9.1.1  propstat XML Element

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

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

    12.9.1.2  status XML Element

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

       <!ELEMENT status (#PCDATA) >

    12.9.2 responsedescription XML Element

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

       <!ELEMENT responsedescription (#PCDATA) >

    12.10 owner XML Element

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

       <!ELEMENT owner ANY>

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    12.11 prop XML element

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

       <!ELEMENT prop ANY>

    12.12 propertybehavior XML element

       Name:       propertybehavior Namespace:  DAV:  Purpose:    Specifies
       how properties are handled during a COPY or MOVE.
       Description: The propertybehavior XML element specifies how
       properties are handled during a COPY or MOVE.  If this XML element is
       not included in the request body then the server is expected to act
       as defined by the default property handling behavior of the
       associated method.  All WebDAV compliant resources MUST support the
       propertybehavior XML element.

       <!ELEMENT propertybehavior (omit | keepalive) >

    12.12.1 keepalive XML element

       Name:       keepalive
       Namespace:  DAV:
       Purpose:    Specifies requirements for the copying/moving of live
       properties.
       Description: If a list of URIs is included as the value of keepalive
       then the named properties MUST be "live" after they are copied
       (moved) to the destination resource of a COPY (or MOVE).  If the
       value "*" is given for the keepalive XML element, this designates
       that all live properties on the source resource MUST be live on the
       destination.  If the requirements specified by the keepalive element
       can not be honored then the method MUST fail with a 412 (Precondition
       Failed).  All DAV compliant resources MUST support the keepalive XML
       element for use with the COPY and MOVE methods.
       Value:      "*" ; #PCDATA value can only be "*"

       <!ELEMENT keepalive (#PCDATA | href+) >

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    12.12.2 omit XML element

       Name:       omit
       Namespace:  DAV:
       Purpose:    The omit XML element instructs the server that it should
       use best effort to copy properties but a failure to copy a property
       MUST NOT cause the method to fail.  Description: The default behavior
       for a COPY or MOVE is to copy/move all properties or fail the method.
       In certain circumstances, such as when a server copies a resource
       over another protocol such as FTP, it may not be possible to
       copy/move the properties associated with the resource. Thus any
       attempt to copy/move over FTP would always have to fail because
       properties could not be moved over, even as dead properties.  All DAV
       compliant resources MUST support the omit XML element on COPY/MOVE
       methods.

       <!ELEMENT omit EMPTY >

    12.13 propertyupdate XML element

       Name:       propertyupdate
       Namespace:  DAV:
       Purpose:    Contains a request to alter the properties on a
       resource.
       Description: This XML element is a container for the information
       required to modify the properties on the resource.  This XML element
       is multi-valued.

       <!ELEMENT propertyupdate (remove | set)+ >

    12.13.1 remove XML element

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

       <!ELEMENT remove (prop) >

    12.13.2 set XML element

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

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

       <!ELEMENT set (prop) >

    12.14 propfind XML Element

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

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

    12.14.1 allprop XML Element

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

       <!ELEMENT allprop EMPTY >

    12.14.2 propname XML Element

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

       <!ELEMENT propname EMPTY >

    13 DAV Properties

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

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    13.1 creationdate Property

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

       <!ELEMENT creationdate (#PCDATA) >

    13.2 displayname Property

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

       <!ELEMENT displayname (#PCDATA) >

    13.3 getcontentlanguage Property

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

       <!ELEMENT getcontentlanguage (#PCDATA) >

    13.4 getcontentlength Property

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

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

       <!ELEMENT getcontentlength (#PCDATA) >

    13.5 getcontenttype Property

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

       <!ELEMENT getcontenttype (#PCDATA) >

    13.6 getetag Property

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

       <!ELEMENT getetag (#PCDATA) >

    13.7 getlastmodified Property

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

       <!ELEMENT getlastmodified (#PCDATA) >

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    13.8 lockdiscovery Property

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

       <!ELEMENT lockdiscovery (activelock)* >

    13.8.1 Example - Retrieving the lockdiscovery Property

       >>Request

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

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

       >>Response

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

       <?xml version="1.0" encoding="utf-8" ?>
       <D:multistatus xmlns:D='DAV:'>
         <D:response>
              <D:href>http://www.foo.bar/container/</D:href>
              <D:propstat>
                   <D:prop>
                        <D:lockdiscovery>
                             <D:activelock>
                                  <D:locktype><D:write/></D:locktype>
                                  <D:lockscope><D:exclusive/></D:lockscope>
                                  <D:depth>0</D:depth>
                                  <D:owner>Jane Smith</D:owner>
                                  <D:timeout>Infinite</D:timeout>
                                  <D:locktoken>

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                                       <D:href>
                   opaquelocktoken:f81de2ad-7f3d-a1b2-4f3c-00a0c91a9d76
                                       </D:href>
                                  </D:locktoken>
                             </D:activelock>
                        </D:lockdiscovery>
                   </D:prop>
                   <D:status>HTTP/1.1 200 OK</D:status>
              </D:propstat>
         </D:response>
       </D:multistatus>

       This resource has a single exclusive write lock on it, with an
       infinite timeout.

    13.9 resourcetype Property

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

       <!ELEMENT resourcetype ANY >

    13.10 source Property

       Name:       source
       Namespace:  DAV:
       Purpose:    The destination of the source link identifies the
       resource that contains the unprocessed source of the link's source.
       Description: The source of the link (src) is typically the URI of the
       output resource on which the link is defined, and there is typically
       only one destination (dst) of the link, which is the URI where the
       unprocessed source of the resource may be accessed.  When more than
       one link destination exists, this specification asserts no policy on
       ordering.

       <!ELEMENT source (link)* >

    13.10.1 Example - A source Property

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

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                   <D:dst>http://foo.bar/src/main.c</D:dst>
              </D:link>
              <D:link>
                   <F:projfiles>Library</F:projfiles>
                   <D:src>http://foo.bar/program</D:src>
                   <D:dst>http://foo.bar/src/main.lib</D:dst>
              </D:link>
              <D:link>
                   <F:projfiles>Makefile</F:projfiles>
                   <D:src>http://foo.bar/program</D:src>
                   <D:dst>http://foo.bar/src/makefile</D:dst>
              </D:link>
         </D:source>
       </D:prop>

       In this example the resource http://foo.bar/program has a source
       property that contains three links.  Each link contains three
       elements, two of which, src and dst, are part of the DAV schema
       defined in this document, and one which is defined by the schema
       http://www.foocorp.com/project/ (Source, Library, and Makefile).  A
       client which only implements the elements in the DAV spec will not
       understand the foocorp elements and will ignore them, thus seeing the
       expected source and destination links.  An enhanced client may know
       about the foocorp elements and be able to present the user with
       additional information about the links.  This example demonstrates
       the power of XML markup, allowing element values to be enhanced
       without breaking older clients.

    13.11 supportedlock Property

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

       <!ELEMENT supportedlock (lockentry)* >

    13.11.1 Example - Retrieving the supportedlock Property

       >>Request

       PROPFIND  /container/ HTTP/1.1

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

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

       >>Response

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

       <?xml version="1.0" encoding="utf-8" ?>
       <D:multistatus xmlns:D="DAV:">
         <D:response>
              <D:href>http://www.foo.bar/container/</D:href>
              <D:propstat>
                   <D:prop>
                        <D:supportedlock>
                             <D:lockentry>
                                  <D:lockscope><D:exclusive/></D:lockscope>
                                  <D:locktype><D:write/></D:locktype>
                             </D:lockentry>
                             <D:lockentry>
                                  <D:lockscope><D:shared/></D:lockscope>
                                  <D:locktype><D:write/></D:locktype>
                             </D:lockentry>
                        </D:supportedlock>
                   </D:prop>
                   <D:status>HTTP/1.1 200 OK</D:status>
              </D:propstat>
         </D:response>
       </D:multistatus>

    14 Instructions for Processing XML in DAV

       All DAV compliant resources MUST ignore any unknown XML element and
       all its children encountered while processing a DAV method that uses
       XML as its command language.

       This restriction also applies to the processing, by clients, of DAV
       property values where unknown XML elements SHOULD be ignored unless
       the property's schema declares otherwise.

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       This restriction does not apply to setting dead DAV properties on the
       server where the server MUST record unknown XML elements.

       Additionally, this restriction does not apply to the use of XML where
       XML happens to be the content type of the entity body, for example,
       when used as the body of a PUT.

       Since XML can be transported as text/xml or application/xml, a DAV
       server MUST accept DAV method requests with XML parameters
       transported as either text/xml or application/xml, and DAV client
       MUST accept XML responses using either text/xml or application/xml.

    15 DAV Compliance Classes

       A DAV compliant resource can choose from two classes of compliance.
       A client can discover the compliance classes of a resource by
       executing OPTIONS on the resource, and examining the "DAV" header
       which is returned.

       Since this document describes extensions to the HTTP/1.1 protocol,
       minimally all DAV compliant resources, clients, and proxies MUST be
       compliant with [RFC2068].

       Compliance classes are not necessarily sequential. A resource that is
       class 2 compliant must also be class 1 compliant; but if additional
       compliance classes are defined later, a resource that is class 1, 2,
       and 4 compliant might not be class 3 compliant.  Also note that
       identifiers other than numbers may be used as compliance class
       identifiers.

    15.1 Class 1

       A class 1 compliant resource MUST meet all "MUST" requirements in all
       sections of this document.

       Class 1 compliant resources MUST return, at minimum, the value "1" in
       the DAV header on all responses to the OPTIONS method.

    15.2 Class 2

       A class 2 compliant resource MUST meet all class 1 requirements and
       support the LOCK method, the supportedlock property, the
       lockdiscovery property, the Time-Out response header and the Lock-
       Token request header.  A class "2" compliant resource SHOULD also
       support the Time-Out request header and the owner XML element.

       Class 2 compliant resources MUST return, at minimum, the values "1"
       and "2" in the DAV header on all responses to the OPTIONS method.

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    16 Internationalization Considerations

       In the realm of internationalization, this specification complies
       with the IETF Character Set Policy [RFC2277]. In this specification,
       human-readable fields can be found either in the value of a property,
       or in an error message returned in a response entity body.  In both
       cases, the human-readable content is encoded using XML, which has
       explicit provisions for character set tagging and encoding, and
       requires that XML processors read XML elements encoded, at minimum,
       using the UTF-8 [UTF-8] encoding of the ISO 10646 multilingual plane.
       XML examples in this specification demonstrate use of the charset
       parameter of the Content-Type header, as defined in [RFC2376], as
       well as the XML "encoding" attribute, which together provide charset
       identification information for MIME and XML processors.

       XML also provides a language tagging capability for specifying the
       language of the contents of a particular XML element.  XML uses
       either IANA registered language tags (see [RFC1766]) or ISO 639
       language tags [ISO-639] in the "xml:lang" attribute of an XML element
       to identify the language of its content and attributes.

       WebDAV applications MUST support the character set tagging, character
       set encoding, and the language tagging functionality of the XML
       specification.  Implementors of WebDAV applications are strongly
       encouraged to read "XML Media Types" [RFC2376] for instruction on
       which MIME media type to use for XML transport, and on use of the
       charset parameter of the Content-Type header.

       Names used within this specification fall into three categories:
       names of protocol elements such as methods and headers, names of XML
       elements, and names of properties.  Naming of protocol elements
       follows the precedent of HTTP, using English names encoded in USASCII
       for methods and headers.  Since these protocol elements are not
       visible to users, and are in fact simply long token identifiers, they
       do not need to support encoding in multiple character sets.
       Similarly, though the names of XML elements used in this
       specification are English names encoded in UTF-8, these names are not
       visible to the user, and hence do not need to support multiple
       character set encodings.

       The name of a property defined on a resource is a URI.  Although some
       applications (e.g., a generic property viewer) will display property
       URIs directly to their users, it is expected that the typical
       application will use a fixed set of properties, and will provide a
       mapping from the property name URI to a human-readable field when
       displaying the property name to a user.  It is only in the case where

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       the set of properties is not known ahead of time that an application
       need display a property name URI to a user. We recommend that
       applications provide human-readable property names wherever feasible.

       For error reporting, we follow the convention of HTTP/1.1 status
       codes, including with each status code a short, English description
       of the code (e.g., 423 (Locked)).  While the possibility exists that
       a poorly crafted user agent would display this message to a user,
       internationalized applications will ignore this message, and display
       an appropriate message in the user's language and character set.

       Since interoperation of clients and servers does not require locale
       information, this specification does not specify any mechanism for
       transmission of this information.

    17 Security Considerations

       This section is provided to detail issues concerning security
       implications of which WebDAV applications need to be aware.

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

    17.1 Authentication of Clients

       Due to their emphasis on authoring, WebDAV servers need to use
       authentication technology to protect not just access to a network
       resource, but the integrity of the resource as well.  Furthermore,
       the introduction of locking functionality requires support for
       authentication.

       A password sent in the clear over an insecure channel is an
       inadequate means for protecting the accessibility and integrity of a
       resource as the password may be intercepted.  Since Basic
       authentication for HTTP/1.1 performs essentially clear text
       transmission of a password, Basic authentication MUST NOT be used to
       authenticate a WebDAV client to a server unless the connection is
       secure. Furthermore, a WebDAV server MUST NOT send Basic
       authentication credentials in a WWW-Authenticate header unless the
       connection is secure.  Examples of secure connections include a
       Transport Layer Security (TLS) connection employing a strong cipher
       suite with mutual authentication of client and server, or a
       connection over a network which is physically secure, for example, an
       isolated network in a building with restricted access.

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       WebDAV applications MUST support the Digest authentication scheme
       [RFC2069]. Since Digest authentication verifies that both parties to
       a communication know a shared secret, a password, without having to
       send that secret in the clear, Digest authentication avoids the
       security problems inherent in Basic authentication while providing a
       level of authentication which is useful in a wide range of scenarios.

    17.2 Denial of Service

       Denial of service attacks are of special concern to WebDAV servers.
       WebDAV plus HTTP enables denial of service attacks on every part of a
       system's resources.

       The underlying storage can be attacked by PUTting extremely large
       files.

       Asking for recursive operations on large collections can attack
       processing time.

       Making multiple pipelined requests on multiple connections can attack
       network connections.

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

    17.3 Security through Obscurity

       WebDAV provides, through the PROPFIND method, a mechanism for listing
       the member resources of a collection.  This greatly diminishes the
       effectiveness of security or privacy techniques that rely only on the
       difficulty of discovering the names of network resources.  Users of
       WebDAV servers are encouraged to use access control techniques to
       prevent unwanted access to resources, rather than depending on the
       relative obscurity of their resource names.

    17.4 Privacy Issues Connected to Locks

       When submitting a lock request a user agent may also submit an owner
       XML field giving contact information for the person taking out the
       lock (for those cases where a person, rather than a robot, is taking
       out the lock). This contact information is stored in a lockdiscovery
       property on the resource, and can be used by other collaborators to
       begin negotiation over access to the resource.  However, in many
       cases this contact information can be very private, and should not be
       widely disseminated.  Servers SHOULD limit read access to the
       lockdiscovery property as appropriate.  Furthermore, user agents

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

    17.5 Privacy Issues Connected to Properties

       Since property values are typically used to hold information such as
       the author of a document, there is the possibility that privacy
       concerns could arise stemming from widespread access to a resource's
       property data.  To reduce the risk of inadvertent release of private
       information via properties, servers are encouraged to develop access
       control mechanisms that separate read access to the resource body and
       read access to the resource's properties.  This allows a user to
       control the dissemination of their property data without overly
       restricting access to the resource's contents.

    17.6 Reduction of Security due to Source Link

       HTTP/1.1 warns against providing read access to script code because
       it may contain sensitive information.  Yet WebDAV, via its source
       link facility, can potentially provide a URI for script resources so
       they may be authored.  For HTTP/1.1, a server could reasonably
       prevent access to source resources due to the predominance of read-
       only access.  WebDAV, with its emphasis on authoring, encourages read
       and write access to source resources, and provides the source link
       facility to identify the source.  This reduces the security benefits
       of eliminating access to source resources.  Users and administrators
       of WebDAV servers should be very cautious when allowing remote
       authoring of scripts, limiting read and write access to the source
       resources to authorized principals.

    17.7 Implications of XML External Entities

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

       External XML entities have no inherent trustworthiness and are
       subject to all the attacks that are endemic to any HTTP GET request.
       Furthermore, it is possible for an external XML entity to modify the
       DTD, and hence affect the final form of an XML document, in the worst

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       case significantly modifying its semantics, or exposing the XML
       processor to the security risks discussed in [RFC2376].  Therefore,
       implementers must be aware that external XML entities should be
       treated as untrustworthy.

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

    17.8 Risks Connected with Lock Tokens

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

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

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

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

       * It may be possible to determine the number of each type of computer
       running WebDAV.

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

    18 IANA Considerations

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

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

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

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

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

    19 Intellectual Property

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

       The IETF takes no position regarding the validity or scope of any
       intellectual property or other rights that might be claimed to
       pertain to the implementation or use other technology described in
       this document or the extent to which any license under such rights
       might or might not be available; neither does it represent that it
       has made any effort to identify any such rights.  Information on the
       IETF's procedures with respect to rights in standards-track and
       standards-related documentation can be found in BCP-11.  Copies of
       claims of rights made available for publication and any assurances of
       licenses to be made available, or the result of an attempt made to
       obtain a general license or permission for the use of such
       proprietary rights by implementors or users of this specification can
       be obtained from the IETF Secretariat.

       The IETF invites any interested party to bring to its attention any
       copyrights, patents or patent applications, or other proprietary
       rights which may cover technology that may be required to practice
       this standard.  Please address the information to the IETF Executive
       Director.

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    20 Acknowledgements

       A specification such as this thrives on piercing critical review and
       withers from apathetic neglect.  The authors gratefully acknowledge
       the contributions of the following people, whose insights were so
       valuable at every stage of our work.

       Terry Allen, Harald Alvestrand, Jim Amsden, Becky Anderson, Alan
       Babich, Sanford Barr, Dylan Barrell, Bernard Chester, Tim Berners-
       Lee, Dan Connolly, Jim Cunningham, Ron Daniel, Jr., Jim Davis, Keith
       Dawson, Mark Day, Brian Deen, Martin Duerst, David Durand, Lee
       Farrell, Chuck Fay, Wesley Felter, Roy Fielding, Mark Fisher, Alan
       Freier, George Florentine, Jim Gettys, Phill Hallam-Baker, Dennis
       Hamilton, Steve Henning, Mead Himelstein, Alex Hopmann, Andre van der
       Hoek, Ben Laurie, Paul Leach, Ora Lassila, Karen MacArthur, Steven
       Martin, Larry Masinter, Michael Mealling, Keith Moore, Thomas Narten,
       Henrik Nielsen, Kenji Ota, Bob Parker, Glenn Peterson, Jon Radoff,
       Saveen Reddy, Henry Sanders, Christopher Seiwald, Judith Slein, Mike
       Spreitzer, Einar Stefferud, Greg Stein, Ralph Swick, Kenji Takahashi,
       Richard N. Taylor, Robert Thau, John Turner, Sankar Virdhagriswaran,
       Fabio Vitali, Gregory Woodhouse, and Lauren Wood.

       Two from this list deserve special mention.  The contributions by
       Larry Masinter have been invaluable, both in helping the formation of
       the working group and in patiently coaching the authors along the
       way.  In so many ways he has set high standards we have toiled to
       meet. The contributions of Judith Slein in clarifying the
       requirements, and in patiently reviewing draft after draft, both
       improved this specification and expanded our minds on document
       management.

       We would also like to thank John Turner for developing the XML DTD.

    21 References

    21.1 Normative References

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

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

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

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    RFC 2518                         WEBDAV                    February 1999

       [RFC2396]       Berners-Lee, T., Fielding, R. and L. Masinter,
                       "Uniform Resource Identifiers (URI): Generic Syntax",
                       RFC 2396, August 1998.

       [REC-XML]       T. Bray, J. Paoli, C. M. Sperberg-McQueen,
                       "Extensible Markup Language (XML)." World Wide Web
                       Consortium Recommendation REC-xml-19980210.
                       http://www.w3.org/TR/1998/REC-xml-19980210.

       [REC-XML-NAMES] T. Bray, D. Hollander, A. Layman, "Namespaces in
                       XML". World Wide Web Consortium Recommendation REC-
                       xml-names-19990114.  http://www.w3.org/TR/1999/REC-
                       xml-names-19990114/

       [RFC2069]       Franks, J., Hallam-Baker, P., Hostetler, J., Leach,
                       P, Luotonen, A., Sink, E. and L. Stewart, "An
                       Extension to HTTP :  Digest Access Authentication",
                       RFC 2069, January 1997.

       [RFC2068]       Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and
                       T. Berners-Lee, "Hypertext Transfer Protocol --
                       HTTP/1.1", RFC 2068, January 1997.

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

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

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

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

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

    21.2 Informational References

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

    Goland, et al.              Standards Track                    [Page 83]

    RFC 2518                         WEBDAV                    February 1999

       [RFC1807]  Lasher, R. and D. Cohen, "A Format for Bibliographic
                  Records", RFC 1807, June 1995.

       [WF]       C. Lagoze, "The Warwick Framework: A Container
                  Architecture for Diverse Sets of Metadata", D-Lib
                  Magazine, July/August 1996.
                  http://www.dlib.org/dlib/july96/lagoze/07lagoze.html

       [USMARC]   Network Development and MARC Standards, Office, ed. 1994.
                  "USMARC Format for Bibliographic Data", 1994. Washington,
                  DC: Cataloging Distribution Service, Library of Congress.

       [REC-PICS] J. Miller, T. Krauskopf, P. Resnick, W. Treese, "PICS
                  Label Distribution Label Syntax and Communication
                  Protocols" Version 1.1, World Wide Web Consortium
                  Recommendation REC-PICS-labels-961031.
                  http://www.w3.org/pub/WWW/TR/REC-PICS-labels-961031.html.

       [RFC2291]  Slein, J., Vitali, F., Whitehead, E. and D. Durand,
                  "Requirements for Distributed Authoring and Versioning
                  Protocol for the World Wide Web", RFC 2291, February 1998.

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

       [RFC2376]  Whitehead, E. and M. Murata, "XML Media Types", RFC 2376,
                  July 1998.

    22 Authors' Addresses

       Y. Y. Goland
       Microsoft Corporation
       One Microsoft Way
       Redmond, WA 98052-6399

       EMail: yarong@microsoft.com

       E. J. Whitehead, Jr.
       Dept. Of Information and Computer Science
       University of California, Irvine
       Irvine, CA 92697-3425

       EMail: ejw@ics.uci.edu

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       A. Faizi
       Netscape
       685 East Middlefield Road
       Mountain View, CA 94043

       EMail: asad@netscape.com

       S. R. Carter
       Novell
       1555 N. Technology Way
       M/S ORM F111
       Orem, UT 84097-2399

       EMail: srcarter@novell.com

       D. Jensen
       Novell
       1555 N. Technology Way
       M/S ORM F111
       Orem, UT 84097-2399

       EMail: dcjensen@novell.com

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    23 Appendices

    23.1 Appendix 1 - WebDAV Document Type Definition

       This section provides a document type definition, following the rules
       in [REC-XML], for the XML elements used in the protocol stream and in
       the values of properties. It collects the element definitions given
       in sections 12 and 13.

       <!DOCTYPE webdav-1.0 [

       <!--============ XML Elements from Section 12 ==================-->

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

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

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

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

       <!ELEMENT depth (#PCDATA) >

       <!ELEMENT owner ANY >

       <!ELEMENT timeout (#PCDATA) >

       <!ELEMENT locktoken (href+) >

       <!ELEMENT href (#PCDATA) >

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

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

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

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       <!ELEMENT prop ANY >

       <!ELEMENT propertybehavior (omit | keepalive) >
       <!ELEMENT omit EMPTY >

       <!ELEMENT keepalive (#PCDATA | href+) >

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

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

       <!ELEMENT collection EMPTY >

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

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    23.2 Appendix 2 - ISO 8601 Date and Time Profile

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

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

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

       date-fullyear   = 4DIGIT
       date-month      = 2DIGIT  ; 01-12
       date-mday       = 2DIGIT  ; 01-28, 01-29, 01-30, 01-31 based on
       month/year
       time-hour       = 2DIGIT  ; 00-23
       time-minute     = 2DIGIT  ; 00-59
       time-second     = 2DIGIT  ; 00-59, 00-60 based on leap second rules
       time-secfrac    = "." 1*DIGIT
       time-numoffset  = ("+" / "-") time-hour ":" time-minute
       time-offset     = "Z" / time-numoffset

       partial-time    = time-hour ":" time-minute ":" time-second
                        [time-secfrac]

       Numeric offsets are calculated as local time minus UTC (Coordinated
       Universal Time).  So the equivalent time in UTC can be determined by
       subtracting the offset from the local time.  For example, 18:50:00-
       04:00 is the same time as 22:58:00Z.

       If the time in UTC is known, but the offset to local time is unknown,
       this can be represented with an offset of "-00:00".  This differs
       from an offset of "Z" which implies that UTC is the preferred
       reference point for the specified time.

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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).

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       Imagine, however, that a server wanted to be "kind" and decided to
       pick the allprop element as the true element and respond to it.  A
       client running over a bandwidth limited line who intended to execute
       a propname would be in for a big surprise if the server treated the
       command as an allprop.

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

    23.3.2.2  Example - Unknown XML Element

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

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

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

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

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

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

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

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    RFC 2518                         WEBDAV                    February 1999

         <D:propname/>
         <E:leave-out>*boss*</E:leave-out>
       </D:propfind>

       The previous example contains the fictitious element leave-out. Its
       purpose is to prevent the return of any property whose name matches
       the submitted pattern.  If the previous example were submitted to a
       server unfamiliar with leave-out, the only result would be that the
       leave-out element would be ignored and a propname would be executed.

    Goland, et al.              Standards Track                    [Page 91]

    RFC 2518                         WEBDAV                    February 1999

    23.4 Appendix 4 -- XML Namespaces for WebDAV

    23.4.1 Introduction

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

    23.4.2 Meaning of Qualified Names

       [Note to the reader: This section does not appear in [REC-XML-NAMES],
       but is necessary to avoid ambiguity for WebDAV XML processors.]

       WebDAV compliant XML processors MUST interpret a qualified name as a
       URI constructed by appending the LocalPart to the namespace name URI.

       Example

       <del:glider xmlns:del="http://www.del.jensen.org/">
         <del:glidername>
              Johnny Updraft
         </del:glidername>
         <del:glideraccidents/>
       </del:glider>

       In this example, the qualified element name "del:glider" is
       interpreted as the URL "http://www.del.jensen.org/glider".

       <bar:glider xmlns:del="http://www.del.jensen.org/">
         <bar:glidername>
              Johnny Updraft
         </bar:glidername>
         <bar:glideraccidents/>
       </bar:glider>

       Even though this example is syntactically different from the previous
       example, it is semantically identical.  Each instance of the
       namespace name "bar" is replaced with "http://www.del.jensen.org/"
       and then appended to the local name for each element tag.  The
       resulting tag names in this example are exactly the same as for the
       previous example.

       <foo:r xmlns:foo="http://www.del.jensen.org/glide">
         <foo:rname>
              Johnny Updraft
         </foo:rname>
         <foo:raccidents/>
       </foo:r>

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

    Goland, et al.              Standards Track                    [Page 93]

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    24.  Full Copyright Statement

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

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

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

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

    Goland, et al.              Standards Track                    [Page 94]