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WEBDAV Working Group                            Y.Y. Goland, Microsoft
INTERNET DRAFT                          E.J. Whitehead, Jr., UC Irvine
<draft-ietf-webdav-protocol-08>                     A. Faizi, Netscape
                                                   S.R. Carter, Novell
                                                     D. Jensen, Novell
Expires September, 1998                                  April 7, 1998


  Extensions for Distributed Authoring on the World Wide Web -- WEBDAV


Status of this Memo

   This document is an Internet-Draft. Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups. Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or made obsolete by other
   documents at any time. It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress".

   To view the entire list of current Internet-Drafts, please check
   the "1id-abstracts.txt" listing contained in the Internet-Drafts
   Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net
   (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au
   (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu
   (US West Coast).

   Distribution of this document is unlimited. Please send comments to
   the Distributed Authoring and Versioning (WEBDAV) working group at
   <w3c-dist-auth@w3.org>, which may be joined by sending a message
   with subject "subscribe" to <w3c-dist-auth-request@w3.org>.

   Discussions of the WEBDAV working group are archived at
   <URL:http://www.w3.org/pub/WWW/Archives/Public/w3c-dist-auth>.

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).













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Contents

STATUS OF THIS MEMO ..................................................1
ABSTRACT .............................................................1
CONTENTS .............................................................2

1 INTRODUCTION .......................................................7

2 NOTATIONAL CONVENTIONS .............................................8

3 DATA MODEL FOR RESOURCE PROPERTIES .................................8
3.1  The Resource Property Model .....................................8
3.2  Existing Metadata Proposals .....................................9
3.3  Properties and HTTP Headers ....................................10
3.4  Property Values ................................................10
3.5  Property Names .................................................10
3.6  Media Independent Links ........................................11

4 COLLECTIONS OF WEB RESOURCES ......................................11
4.1  Collection Resources ...........................................11
4.2  Creation and Retrieval of Collection Resources .................12
4.3  HTTP URL Namespace Model .......................................12
4.4  Source Resources and Output Resources ..........................12

5 LOCKING ...........................................................13
5.1  Exclusive Vs. Shared Locks .....................................14
5.2  Required Support ...............................................15
5.3  Lock Tokens ....................................................15
5.4  opaquelocktoken Lock Token URI Scheme ..........................15
5.5  Lock Capability Discovery ......................................16
5.6  Active Lock Discovery ..........................................16
5.7  Usage Considerations ...........................................16

6 WRITE LOCK ........................................................17
6.1  Methods Restricted by Write Locks ..............................17
6.2  Write Locks and Properties .....................................18
6.3  Write Locks and Null Resources .................................18
6.4  Write Locks and Collections ....................................18
6.5  Write Locks and the If Request Header ..........................19
 6.5.1 Example - Write Lock .........................................19
6.6  Write Locks and COPY/MOVE ......................................20
6.7  Refreshing Write Locks .........................................20

7 HTTP METHODS FOR DISTRIBUTED AUTHORING ............................20
7.1  PROPFIND .......................................................21
 7.1.1 Example - Retrieving Named Properties ........................22
 7.1.2 Example - Using allprop to Retrieve All Properties ...........23
 7.1.3 Example - Using propname to Retrieve all Property Names ......25
7.2  PROPPATCH ......................................................27
 7.2.1 Status Codes for use with Multi-Status .......................27
 7.2.2 Example - PROPPATCH ..........................................28
7.3  MKCOL Method ...................................................29
 7.3.1 Request ......................................................29

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 7.3.2 Response Codes ...............................................30
 7.3.3 Example - MKCOL ..............................................30
7.4  GET, HEAD for Collections ......................................31

7.5  POST for Collections ...........................................31

7.6  DELETE .........................................................31
 7.6.1 DELETE for Non-Collection Resources ..........................31
 7.6.2 DELETE for Collections .......................................31

7.7  PUT ............................................................32
 7.7.1 PUT for Non-Collection Resources .............................32
 7.7.2 PUT for Collections ..........................................33

7.8  COPY Method ....................................................33
 7.8.1 COPY for HTTP/1.1 resources ..................................33
 7.8.2 COPY for Properties ..........................................34
 7.8.3 COPY for Collections .........................................34
 7.8.4 COPY and the Overwrite Header ................................35
 7.8.5 Status Codes .................................................35
 7.8.6 Example - COPY with Overwrite ................................36
 7.8.7 Example - COPY with No Overwrite .............................36
 7.8.8 Example - COPY of a Collection ...............................36

7.9  MOVE Method ....................................................37
 7.9.1 MOVE for Properties ..........................................37
 7.9.2 MOVE for Collections .........................................38
 7.9.3 MOVE and the Overwrite Header ................................38
 7.9.4 Status Codes .................................................39
 7.9.5 Example - MOVE of a Non-Collection ...........................39
 7.9.6 Example - MOVE of a Collection ...............................39

7.10  LOCK Method ...................................................40
 7.10.1 Operation ...................................................40
 7.10.2 The Effect of Locks on Properties and Collections ...........41
 7.10.3 Locking Replicated Resources ................................41
 7.10.4 Depth and Locking ...........................................41
 7.10.5 Interaction with other Methods ..............................42
 7.10.6 Lock Compatibility Table ....................................42
 7.10.7 Status Codes ................................................42
 7.10.8 Example - Simple Lock Request ...............................43
 7.10.9 Example - Refreshing a Write Lock ...........................44
 7.10.10 Example - Multi-Resource Lock Request ......................45

7.11  UNLOCK Method .................................................46
 7.11.1 Example - UNLOCK ............................................46

8 HTTP HEADERS FOR DISTRIBUTED AUTHORING ............................47
8.1  DAV Header .....................................................47
8.2  Depth Header ...................................................47
8.3  Destination Header .............................................48
8.4  If Header ......................................................48
 8.4.1 No-tag-list Production .......................................49

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 8.4.2 Tagged-list Production .......................................49
 8.4.3 not Production ...............................................50
 8.4.4 Matching Function ............................................50
 8.4.5 If Header and Non-DAV Compliant Proxies ......................51
8.5  Lock-Token Request Header ......................................51
8.6  Overwrite Header ...............................................51
8.7  Status-URI Response Header .....................................51
8.8  Timeout Request Header .........................................52

9 STATUS CODE EXTENSIONS TO HTTP/1.1 ................................53
9.1  102 Processing .................................................53
9.2  207 Multi-Status ...............................................53
9.3  422 Unprocessable Entity .......................................53
9.4  423 Locked .....................................................53
9.5  424 Method Failure .............................................53
9.6  425 Insufficient Space on Resource .............................53

10 MULTI-STATUS RESPONSE ............................................54

11 XML ELEMENT DEFINITIONS ..........................................54
11.1  activelock XML Element ........................................54
 11.1.1 depth XML Element ...........................................54
 11.1.2 locktoken XML Element .......................................54
 11.1.3 timeout XML Element .........................................54
11.2  collection XML Element ........................................55
11.3  href XML Element ..............................................55
11.4  link XML Element ..............................................55
 11.4.1 dst XML Element .............................................55
 11.4.2 src XML Element .............................................55
11.5  lockentry XML Element .........................................56
11.6  lockinfo XML Element ..........................................56
11.7  lockscope XML Element .........................................56
 11.7.1 exclusive XML Element .......................................56
 11.7.2 shared XML Element ..........................................56
11.8  locktype XML Element ..........................................56
 11.8.1 write XML Element ...........................................57
11.9  multistatus XML Element .......................................57
 11.9.1 response XML Element ........................................57
 11.9.2 responsedescription XML Element .............................58
11.10  owner XML Element ............................................58
11.11  prop XML element .............................................58
11.12  propertybehavior XML element .................................59
 11.12.1 keepalive XML element ......................................59
 11.12.2 omit XML element ...........................................59
11.13  propertyupdate XML element ...................................60
 11.13.1 remove XML element .........................................60
 11.13.2 set XML element ............................................60
11.14  propfind XML Element .........................................60





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 11.14.1 allprop XML Element ........................................61
 11.14.2 propname XML Element .......................................61

12 DAV PROPERTIES ...................................................61
12.1  creationdate Property .........................................61
12.2  displayname Property ..........................................61
12.3  getcontentlanguage Property ...................................62
12.4  getcontentlength Property .....................................62
12.5  getcontenttype Property .......................................62
12.6  getetag Property ..............................................62
12.7  getlastmodified Property ......................................63
12.8  lockdiscovery Property ........................................63
 12.8.1 Example - Retrieving the lockdiscovery Property .............63
12.9  resourcetype Property .........................................64
12.10  source Property ..............................................65
 12.10.1 Example - A source Property ................................65
12.11  supportedlock Property .......................................66
 12.11.1 Example - Retrieving the supportedlock Property ............66

13 DAV XML PROCESSING INSTRUCTIONS ..................................67

14 DAV COMPLIANCE CLASSES ...........................................67
14.1  Class 1 .......................................................68
14.2  Class 2 .......................................................68

15 INTERNATIONALIZATION CONSIDERATIONS ..............................68

16 SECURITY CONSIDERATIONS ..........................................69
16.1  Authentication of Clients .....................................69
16.2  Denial of Service .............................................70
16.3  Security through Obscurity ....................................70
16.4  Privacy Issues Connected to Locks .............................71
16.5  Privacy Issues Connected to Properties ........................71
16.6  Reduction of Security due to Source Link ......................71

17 IANA CONSIDERATIONS ..............................................71
18 TERMINOLOGY ......................................................72
19 COPYRIGHT ........................................................73
20 INTELLECTUAL PROPERTY ............................................73
21 ACKNOWLEDGEMENTS .................................................74
22 REFERENCES .......................................................75
22.1  Normative References ..........................................75
22.2  Informational References ......................................75
23 AUTHORS' ADDRESSES ...............................................77
24 APPENDICES .......................................................78
24.1  Appendix 1 - WebDAV Document Type Definition ..................78
24.2  Appendix 2 - ISO 8601 Date and Time Profile ...................79
24.3  Appendix 3 - Notes on Processing XML Elements .................80
 24.3.1 Notes on Empty XML Elements .................................80
 24.3.2 Notes on Illegal XML Processing .............................80
24.4  Appendix 4 -- XML Namespaces for WebDAV .......................82


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 24.4.1 Introduction ................................................82
 24.4.2 Namespace Declaration PI ....................................83
 24.4.3 Placing Declarations in Documents ...........................84
 24.4.4 Prolog with Namespace Declarations ..........................84
 24.4.5 Qualified Names .............................................84
 24.4.6 Universal Names .............................................85
 24.4.7 Using Qualified Names .......................................85
 24.4.8 Processing instruction ......................................85
 24.4.9 Scope and Meaning of Qualified Names ........................85











































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1  Introduction

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

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

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

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

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

   Requirements and rationale for these operations are described in a
   companion document, "Requirements for a Distributed Authoring and
   Versioning Protocol for the World Wide Web" [Slein et al., 1998].

   The sections below provide a detailed introduction to resource
   properties (section 3), collections of resources (section 4), and
   locking operations (section 5).  These sections introduce the
   abstractions manipulated by the WebDAV-specific HTTP methods
   described in section 7, "HTTP Methods for Distributed Authoring".

   In HTTP/1.1, method parameter information was exclusively encoded in
   HTTP headers. Unlike HTTP/1.1, WebDAV, encodes method parameter
   information either in an Extensible Markup Language (XML) [Bray,
   Paoli, Sperberg-McQueen, 1998] request entity body, or in an HTTP
   header.  The use of XML to encode method parameters was motivated by
   the ability to add extra XML elements to existing structures,
   providing extensibility, and by XML's ability to encode information
   in ISO 10646 character sets, providing internationalization support.
   As a rule of thumb, parameters are encoded in XML entity bodies when
   they have unbounded length, or when they may be shown to a human
   user and hence require encoding in an ISO 10646 character set.
   Otherwise, parameters are encoded within HTTP headers.  Section 8
   describes the new HTTP headers used with WebDAV methods.

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


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

   XML elements used in this specification are defined in section 11.

   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 9.  Since some WebDAV methods may operate over
   many resources, the Multi-Status response has been introduced to
   return status information for multiple resources.  The Multi-Status
   response is described in section 10.

   WebDAV employs the property mechanism to store information about the
   current state of the resource.  For example, when a lock is taken
   out on a resource, a lock information property describes the current
   state of the lock. Section 12 defines the properties used within the
   WebDAV specification.

   Finishing off the specification are sections on what it means to be
   compliant with this specification (section 14), on
   internationalization support (section 15), and on security (section
   16).

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
   [Fielding et al., 1997].  Since this augmented BNF uses the basic
   production rules provided in section 2.2 of [Fielding et al., 1997],
   these rules apply to this document as well.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [Bradner,
   1997].

3  Data Model for Resource Properties

3.1 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

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   '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. A dead property has its syntax and semantics
   enforced by the client; the server merely records the value of the
   property verbatim.

3.2 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 [Miller et al., 1996], PICS-NG, XML, Web Collections,
   and several proposals on representing relationships within HTML.
   Work on PICS-NG and Web Collections has been subsumed by the
   Resource Definition Framework (RDF) metadata activity of the World
   Wide Web Consortium. RDF consists of a network-based data model and
   an XML representation of that model.

   Some proposals come from a digital library perspective.  These
   include the Dublin Core [Weibel et al., 1995] metadata set and the
   Warwick Framework [Lagoze, 1996], a container architecture for
   different metadata schemas.  The literature includes many examples
   of metadata, including MARC [MARC, 1994], a bibliographic metadata
   format, and RFC 1807 [Lasher, Cohen, 1995], a technical report
   bibliographic format employed by the Dienst system. Additionally,
   the proceedings from the first IEEE Metadata conference describe
   many community-specific metadata sets.

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




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3.3 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.

3.4 Property Values

   The value of a property is, at minimum, well formed XML.

   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.

3.5 Property Names

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

   Because a property's name is universally unique, clients can depend
   upon consistent behavior for a particular property across multiple
   resources, so long as that property is "live" on the resources in
   question.

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

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

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



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3.6 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.  WebDAV provides such links. A WebDAV link is a special type
   of property value, formally defined in section 11.4, that allows
   typed connections to be established between resources of any media
   type.  The property value consists of source and destination Uniform
   Resource Locators (URLs); the property name identifies the link
   type.

4  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.

4.1 Collection Resources

   A collection is a resource whose state consists of at least a list
   of internal members and a set of properties, but which may have
   additional state such as entity bodies returned by GET.  An internal
   member resource MUST have a URI that is immediately relative to the
   base URI of the collection.  That is, the internal member's URI is
   equal to the parent collection's URI plus an additional segment
   where segment is defined in section 3.2.1 of RFC 2068 [Fielding et
   al., 1996].

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

   WebDAV servers MUST treat HTTP URL namespaces as collections,
   regardless of whether they were created with the MKCOL method
   described in section 7.3.

   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 URL ending with the "/".  For example, if a client invokes a
   method on http://foo.bar/blah (no trailing slash), the resource
   http://foo.bar/blah/ (trailing slash) may respond as if the
   operation were invoked on it, and should return a content-location


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   header with http://foo.bar/blah/ in it.  In general clients SHOULD
   use the "/" form of collection names.

4.2 Creation and Retrieval of Collection Resources

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

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

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

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

4.3 HTTP URL Namespace Model

   The HTTP URL Namespace is a hierarchical namespace where the
   hierarchy is delimited with the "/" character.  DAV compliant
   resources MUST maintain the consistency of the HTTP URL namespace.
   For example, if the collection http://www.foo.bar.org/a/ exists, but
   http://www.foo.bar.org/a/b/ does not exist, an attempt to create
   http://www.foo.bar.org/a/b/c must fail.

4.4 Source Resources and Output Resources

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

   However, the server can sometimes process HTML resources before they
   are transmitted as a return entity body.  For example, 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)

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   differs from the persistent state of the resource (HTML plus
   directive).  Typically there is no way to access the HTML resource
   containing the unprocessed directive.

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

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

   On WebDAV compliant servers the URI of the source resource(s) may be
   stored in a link on the output resource with type DAV:source (see
   section 12.10 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.

5  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.


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5.1 Exclusive Vs. Shared Locks

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

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

   With shared locks there are two trust sets that affect a resource.
   The first trust set is created by access permissions.  Principals
   who are trusted, for example, may have permission to write to the
   resource.  Among those who have access permission to write to the
   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.


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5.2 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.

5.3 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.

5.4 opaquelocktoken Lock Token URI Scheme

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

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

   In order to guarantee uniqueness across all resources for all time
   the opaquelocktoken requires the use of the Universally Unique

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   Identifier (UUID, also known as a Globally Unique Identifier, or
   GUID) mechanism, as described in [Leach, Salz, 1998].

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

   OpaqueLockToken-URI = "opaquelocktoken:" UUID [Extension]  ; The
   UUID production is the string form of a UUID, as defined in [Leach,
   Salz, 1998]. Note that white space (LWS) is not allowed between
   elements of this production.

   Extension = path  ; path is defined in section 3.2.1 of RFC 2068
   [Fielding et al., 1996]

5.5 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.

5.6 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.

5.7 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:



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

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

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

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

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

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

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

6  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.

6.1 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 independent of the lock.

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

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6.2 Write Locks and Properties

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

6.3 Write Locks and Null Resources

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

   A write locked null resource, 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 resources 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.

6.4 Write Locks and Collections

   A write lock on a collection prevents the addition or removal of
   members of the collection by non-lock owners.  As a consequence,
   when a principal issues a request to create a new internal member of
   a write locked collection using PUT or POST, or to remove an
   existing internal member of a write locked collection using DELETE,
   this request MUST fail if the principal does not have a write lock
   on the collection.

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

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

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

6.5 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.

6.5.1     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.


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6.6 Write Locks and COPY/MOVE

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

   A MOVE MUST NOT move the write lock with the resource although the
   resource is subject to being added to an existing lock as specified
   in section 6.4. For example, if the MOVE makes the resource a child
   of a collection that is depth locked then the resource will be under
   that collection's lock. Additionally, if a depth locked resource is
   moved to a destination that is within the scope of the same depth
   lock (e.g., within the namespace tree covered by the lock), the
   moved resource will again be a member of the lock. In both these
   examples, as specified in section 6.5, an If header must be
   submitted containing a lock token for both the source and
   destination.

6.7 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.

7  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 [Bray, Paoli, Sperberg-McQueen,
   1998].  All XML used in either requests or responses MUST be, at
   minimum, well formed.  If a server receives ill-formed XML in a
   request it MUST reject the entire request with a 400 Bad Request.
   If a client receives ill-formed XML in a response then it MUST NOT
   assume anything about the outcome of the executed method and SHOULD
   treat the server as malfunctioning.

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7.1 PROPFIND

   The PROPFIND method retrieves properties defined on the Request-URI,
   if the resource does not have any internal members, or on the
   Request-URI and potentially its member resources, if the resource
   does have internal members.  All DAV compliant resources MUST
   support the PROPFIND method and the propfind XML element (section
   11.14) 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 resource with internal members.  DAV
   compliant servers MUST support the "0", "1" and "infinity"
   behaviors. By default, the PROPFIND method without a Depth header
   MUST act as if a "Depth: infinity" header was included.

   A client may submit a propfind XML element in the body of the
   request method describing what information is being requested.  It
   is possible to request particular property values, all property
   values, or a list of the names of the resource's properties.  A
   client may choose not to submit a request body.  An empty 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 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 resource with
   members MUST include a response XML element for each member of the
   resource, to whatever depth was requested. Each response XML element
   MUST contain an href XML element that identifies the resource on
   which the properties in the prop XML element are defined.  Results
   for a PROPFIND on a resource with internal members are returned as a
   flat list whose order of entries is not significant.

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

   The results of this method SHOULD NOT be cached.





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7.1.1     Example - Retrieving Named Properties

   >>Request

   PROPFIND  /file HTTP/1.1
   Host: www.foo.bar
   Content-type: text/xml
   Content-Length: xyz

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <?xml:namespace ns="http://www.foo.bar/boxschema/" prefix="R" ?>
   <D:propfind>
     <D:prop>
          <R:bigbox/>
          <R:author/>
          <R:DingALing/>
          <R:Random/>
     </D:prop>
   </D:propfind>

   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <?xml:namespace ns="http://www.foo.bar/boxschema/" prefix="R" ?>
   <D:multistatus>
     <D:response>
          <D:href>http://www.foo.bar/file</D:href>
          <D:propstat>
               <D:prop>
                    <R:bigbox>
                         <R:BoxType>Box type A</R:BoxType>
                    </R:bigbox>
                    <R:author>
                         <R:Name>J.J. Johnson</R:Name>
                    </R:author>
               </D:prop>
               <D:status>HTTP/1.1 200 OK</D:status>
          </D:propstat>
          <D:propstat>
               <D:prop><R:DingALing/><R:Random/></D:prop>
               <D:status>HTTP/1.1 403 Forbidden</D:status>
               <D:responsedescription> The user does not have access to
   the DingALing property.
               </D:responsedescription>
          </D:propstat>
     </D:response>

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     <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.

7.1.2     Example - Using allprop to Retrieve All Properties

   >>Request

   PROPFIND  /container/ HTTP/1.1
   Host: www.foo.bar
   Depth: 1
   Content-Type: text/xml
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:propfind>
     <D:allprop/>
   </D:propfind>

   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <?xml:namespace ns="http://www.foo.bar/boxschema/" prefix="R" ?>
   <D:multistatus>
     <D:response>
          <D:href>http://www.foo.bar/container/</D:href>
          <D:propstat>
               <D:prop>
                    <R:bigbox>
                         <R:BoxType>Box type A</R:BoxType>
                    </R:bigbox>
                    <R:author>
                         <R:Name>Hadrian</R:Name>
                    </R:author>
                    <D:creationdate>
                         1997-12-01T17:42:21-08:00
                    </D:creationdate>
                    <D:displayname>
                         Example collection

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

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   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 12.
   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.

   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).

7.1.3     Example - Using propname to Retrieve all Property Names

   >>Request

   PROPFIND  /container/ HTTP/1.1
   Host: www.foo.bar
   Content-Type: text/xml
   Content-Length: xxxxx


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   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:propfind>
     <D:propname/>
   </D:propfind>

   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: xxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <?xml:namespace ns="http://www.foo.bar/boxschema/" prefix="R" ?>
   <D:multistatus>
     <D:response>
          <D:href>http://www.foo.bar/container/</D:href>
          <D:propstat>
               <D:prop>
                    <R:bigbox/>
                    <R:author/>
                    <D:creationdate/>
                    <D:displayname/>
                    <D:resourcetype/>
                    <D:supportedlock/>
               </D:prop>
               <D:status>HTTP/1.1 200 OK</D:status>
          </D:propstat>
     </D:response>
     <D:response>
          <D:href>http://www.foo.bar/container/front.html</D:href>
          <D:propstat>
               <D:prop>
                    <R:bigbox/>
                    <D:creationdate/>
                    <D:displayname/>
                    <D:getcontentlength/>
                    <D:getcontenttype/>
                    <D:getetag/>
                    <D:getlastmodified/>
                    <D:resourcetype/>
                    <D:supportedlock/>
               </D:prop>
               <D:status>HTTP/1.1 200 OK</D:status>
          </D:propstat>
     </D:response>
   </D:multistatus>


   In this example, PROPFIND is invoked on the collection resource
   http://www.foo.bar/container/, with a propfind XML element

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   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.

7.2 PROPPATCH

   The PROPPATCH method processes instructions specified in the request
   body to set and/or remove properties defined on the resource
   identified by 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 11.13.

7.2.1     Status Codes for use with Multi-Status

   The following are examples of response codes one would expect to be
   used in a 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 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.

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   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.

   425 Insufficient Space on Resource - The server did not have
   sufficient space to record the property.

7.2.2     Example - PROPPATCH

   >>Request

   PROPPATCH /bar.html HTTP/1.1
   Host: www.foo.com
   Content-Type: text/xml
   Content-Length: xxxx

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















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   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <?xml:namespace ns="http://www.w3.com/standards/z39.50/" prefix="Z"
   ?>
   <D:multistatus>
     <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 Method Failure</D:status>
          </D:propstat>
          <D:propstat>
               <D:prop><Z:Copyright-Owner/></D:prop>
               <D:status>HTTP/1.1 409 Conflict</D:status>
          </D:propstat>
          <D:responsedescription> Copyright Owner can not be deleted or
   altered.</D:responsedescription>
     </D:response>
   </D:multistatus>

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

7.3 MKCOL Method

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

7.3.1     Request

   MKCOL creates a new collection resource at the location specified by
   the Request-URI.  If the resource identified by the Request-URI is
   non-null then the MKCOL MUST fail.  During MKCOL processing, a
   server MUST make the Request-URI a member of its parent collection,
   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.

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   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.

7.3.2     Response Codes

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

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

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

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

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

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

   425 Insufficient Space on Resource - The resource does not have
   sufficient space to record the state of the resource after the
   execution of this method.

7.3.3     Example - 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

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7.4 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" [Fielding et al.,
   1997].  GET when applied to a collection may return the contents of
   an "index.html" resource, a human-readable view of the contents of
   the collection, or something else altogether. Hence it is possible
   that the result of a GET on a collection will bear no correlation to
   the 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.

7.5 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.

7.6 DELETE

7.6.1     DELETE for Non-Collection Resources

   If the DELETE method is issued to a non-collection resource which is
   an internal member of a collection, then during DELETE processing a
   server MUST remove the Request-URI from its parent collection.

7.6.2     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 its internal member resources are to be deleted.

   If any member cannot be deleted then all of the member's ancestors
   MUST NOT be deleted, so as to maintain the namespace.

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

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



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   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 Method Failure 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.

7.6.2.1   Example - DELETE

   >>Request

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

   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="d" ?>
   <d:multistatus>
     <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.

7.7 PUT

7.7.1     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.

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

7.7.2     PUT for Collections

   As defined in the HTTP/1.1 specification [Fielding et al., 1997],
   the "PUT method requests that the enclosed entity be stored under
   the supplied Request-URI."  Since submission of an entity
   representing a collection would implicitly encode creation and
   deletion of resources, this specification intentionally does not
   define a transmission format for creating a collection using PUT.
   Instead, the MKCOL method is defined to create collections.

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

7.8 COPY Method

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

   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.

7.8.1     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.  However, the exact state and behavior of the destination
   resource depend on what information the source resource is able to
   provide and what information the destination resource is able to
   accept.

   Subsequent alterations to the destination resource will not modify
   the source resource.  Subsequent alterations to the source resource
   will not modify the destination resource.




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   All properties on the source resource MUST be duplicated on the
   destination resource, subject to modifying headers and XML elements,
   following the definition for copying properties.

7.8.2     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 11.12.

7.8.3     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 specified in
   the Request-URI is to be copied to the location specified in the
   Destination header, and all its internal member resources are to be
   copied to a location relative to it, recursively through all levels
   of the collection hierarchy.

   A COPY of depth "0" only instructs that the collection and its
   properties but not its internal members, 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 for the
   Request-URI. When applied to members of the collection specified in
   the request-URI the value of Destination is to be modified to
   reflect the current location in the hierarchy.  So, if the request-
   URI is /a/ and the destination is /b/ then when /a/c/d is processed
   it must use a destination of /b/c/d.

   When the COPY method has completed processing it MUST have created a
   consistent namespace at the destination.  However, if an error
   occurs while copying an internal member collection, the server MUST
   NOT copy any members of this collection. After detecting an error,

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   the COPY operation SHOULD try to finish as much of the original copy
   operation as possible.  So, for example, if an infinite depth copy
   operation is performed on collection /a/, which contains collections
   /a/b/ and /a/c/, and an error occurs copying /a/b/, an attempt
   should still be made to copy /a/c/. Similarly, after encountering an
   error copying a non-collection resource as part of an infinite depth
   copy, the server SHOULD try to finish as much of the original copy
   operation as possible.

   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.

   424 Method Failure errors SHOULD NOT be returned in the 207 Multi-
   Status 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 response 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.

7.8.4     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.

7.8.5     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.

   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.

   425 Insufficient Space on Resource - The destination resource does
   not have sufficient space to record the state of the resource after
   the execution of this method.

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



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7.8.6     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

7.8.7     Example - COPY with No Overwrite

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

   >>Request

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

   >>Response

   HTTP/1.1 412 Precondition Failed

7.8.8     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
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="d" ?>
   <d:propertybehavior>
     <d:keepalive>*</d:keepalive>
   </d:propertybehavior>

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   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="d" ?>
   <d:multistatus>
     <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 7.8.3.

7.9 MOVE Method

   The MOVE operation on a non-collection resource is the logical
   equivalent of a copy (COPY) followed by a delete of the source,
   where the actions are performed atomically.  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.

7.9.1     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 7.8.2.


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7.9.2     MOVE for Collections

   A MOVE of depth infinity instructs that the collection specified in
   the Request-URI be moved to the location specified in the
   Destination header, and all its internal member resources are to be
   moved to locations relative to it, recursively through all levels of
   the collection hierarchy.

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

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

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

   When the MOVE method has completed processing it MUST have created a
   consistent namespace on both the source and destination. However, if
   an error occurs while moving an internal member collection, the
   server MUST NOT move any members of the failed collection.. In this
   case, after detecting the error, the move operation SHOULD try to
   finish as much of the original move as possible.  So, for example,
   if an infinite depth move is performed on collection /a/, which
   contains collections /a/b/ and /a/c/, and an error occurs moving
   /a/b/, an attempt should still be made to try moving /a/c/.
   Similarly, after encountering an error moving a non-collection
   resource as part of an infinite depth move, the server SHOULD try to
   finish as much of the original move operation as possible.

   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 Method Failure errors SHOULD NOT be returned as values in the
   207 Multi-Status 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 MOVES.  These
   responses can be safely omitted because they are the default success
   codes.

7.9.3     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.



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7.9.4     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.

   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.

7.9.5     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
   Content-Location: http://www.ics.uci.edu/users/f/fielding/index.html


7.9.6     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

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   Content-Length: xyz

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="d" ?>
   <d:propertybehavior>
     <d:keepalive>*</d:keepalive>
   </d:propertybehavior>

   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: zzz

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="d" ?>
   <d:multistatus>
     <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 7.8.3.  User agent authentication has previously occurred
   via a mechanism outside the scope of the HTTP protocol, in an
   underlying transport layer.

7.10 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.

7.10.1    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

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   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.

7.10.2    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.

7.10.3    Locking Replicated Resources

   Some servers automatically replicate resources across multiple URLs.
   In such a circumstance the server MUST only accept a lock on one of
   the URLs if the server can guarantee that the lock will be honored
   across all the URLs.

7.10.4    Depth and Locking

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

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

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



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

7.10.5    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.

7.10.6    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.

7.10.7    Status Codes

   200 Success - 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.










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7.10.8    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
   Content-Length: xyz
   Authorization: Digest username="ejw",
      realm="ejw@webdav.sb.aol.com", nonce="...",
      uri="/workspace/webdav/proposal.doc",
      response="...", opaque="..."

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:lockinfo>
     <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
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:prop>
     <D:lockdiscovery>
          <D:activelock>
               <D:locktype><D:write/></D:locktype>
               <D:lockscope><D:exclusive/></D:lockscope>
               <D:depth>Infinity</D:depth>
               <D:owner>
                    <D:href>
                         http://www.ics.uci.edu/~ejw/contact.html
                    </D:href>
               </D:owner>
               <D:timeout>Second-604800</D:timeout>
               <D:locktoken>
                    <D:href>
               opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4
                    </D:href>
               </D:locktoken>
          </D:activelock>
     </D:lockdiscovery>
   </D:prop>

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   This 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.

7.10.9    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
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:prop>
     <D:lockdiscovery>
          <D:activelock>
               <D:locktype><D:write/></D:locktype>
               <D:lockscope><D:exclusive/></D:lockscope>
               <D:depth>Infinity</D:depth>
               <D:owner>
                    <D:href>
                    http://www.ics.uci.edu/~ejw/contact.html
                    </D:href>
               </D:owner>
               <D:timeout>Second-604800</D:timeout>
               <D:locktoken>
                    <D:href>
               opaquelocktoken:e71d4fae-5dec-22d6-fea5-00a0c91e6be4
                    </D:href>
               </D:locktoken>
          </D:activelock>
     </D:lockdiscovery>
   </D:prop>

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

7.10.10   Example - Multi-Resource Lock Request

   >>Request

   LOCK /webdav/ HTTP/1.1
   Host: webdav.sb.aol.com
   Timeout: Infinite, Second-4100000000
   Depth: infinity
   Authorization: Digest username="ejw",
      realm="ejw@webdav.sb.aol.com", nonce="...",
      uri="/workspace/webdav/proposal.doc",
      response="...", opaque="..."

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:lockinfo>
     <D:locktype><D:write/></D:locktype>
     <D:lockscope><D:exclusive/></D:lockscope>
     <D:owner>
          <D:href>http://www.ics.uci.edu/~ejw/contact.html</D:href>
     </D:owner>
   </D:lockinfo>

   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:multistatus>
     <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 Method Failure</D:status>
          </D:propstat>
     </D:response>
   </D:multistatus>


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   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.

7.11 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.

7.11.1    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 status code is used instead
   of 200 OK because there is no response entity body.

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

8  HTTP Headers for Distributed Authoring

8.1 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 14 for more details.
   In general, however, support for one compliance class does not
   entail support for any other.

8.2 Depth Header

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

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

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

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

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

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

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

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

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

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

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

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

8.3 Destination Header

   Destination = "Destination" ":" URI

   The Destination header specifies a destination resource for methods
   such as COPY and MOVE, which take two URIs as parameters.

8.4 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 = "<" URI ">"

   The If header is intended to have similar functionality to the If-
   Match header defined in section 14.25 of [Fielding et al., 1997].
   However the If header is intended for use with any URI which
   represents state information, referred to as a state token, about a
   resource as well as e-tags.  A typical example of a state token is a
   lock token, and lock tokens are the only state tokens defined in
   this specification.

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   All DAV compliant resources MUST honor the If header.

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

8.4.1     No-tag-list Production

   The No-tag-list production describes a series of state tokens and e-
   tags.  If multiple No-tag-list productions are used then only one

   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.

8.4.1.1   Example - No-tag-list If Header

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

   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 e-tag" e-tag or in
   the state identified by the second e-tag "I am another e-tag".  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 e-tag"]) (and ["I am another e-tag"])).

8.4.2     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.



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

8.4.2.1   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 e-tag"]) (["strong e-tag"])
   <http://www.bar.bar/random>(["another strong e-tag"])

   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 e-tag"])
   (["strong e-tag"])", 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 e-tag" or it must have a strong entity tag "strong e-tag".

   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.

8.4.3     not Production

   Every state token or e-tag 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 e-tag 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.

8.4.4     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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8.4.5     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.

8.5 Lock-Token Request 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.

8.6 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 409 Conflict status code.

   All DAV compliant resources MUST support the Overwrite header.

8.7 Status-URI Response Header

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

   Status-URI = "Status-URI" ":" *(Status-Code "<" URI ">") ; Status-
   Code is defined in 6.1.1 of [Fielding et al., 1997]

   The URIs listed in the header are source resources which have been
   affected by the outstanding method.  The status code indicates the
   resolution of the method on the identified resource.  So, for
   example, if a MOVE method on a collection is outstanding and a 102
   "Processing" response with a Status-URI response header is returned,

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   the included URIs will indicate resources that have had move
   attempted on them and what the result was.

8.8 Timeout Request Header

   TimeOut = "Timeout" ":" 1#TimeType
   TimeType = ("Second-" DAVTimeOutVal | "Infinite" | Other)
   DAVTimeOutVal = 1*digit
   Other = Extend field-value   ; See section 4.2 of [Fielding et al.,
   1997]

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

   A Timeout request header MUST contain at least one TimeType and may
   contain multiple TimeType entries. The purpose of listing multiple
   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 valuse 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
   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

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   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.

9  Status Code Extensions to HTTP/1.1

   The following status codes are added to those defined in HTTP/1.1
   [Fielding et al., 1997].

9.1 102 Processing

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

   If a method is taking longer than 20 seconds (a reasonable, but
   arbitrary value) to process the server SHOULD return a 102
   "Processing" response.

9.2 207 Multi-Status

   The response provides status for multiple independent operations.

9.3 422 Unprocessable Entity

   The server understands the content type of the request entity, but
   was unable to process the contained instructions.

9.4 423 Locked

   The source or destination resource of a method is locked.

9.5 424 Method Failure

   The method was not executed on a particular resource within its
   scope because some part of the method's execution failed causing the
   entire method to be aborted.  For example, if a command in a
   PROPPATCH method fails then, at minimum, the rest of the commands
   will also fail with 424 Method Failure.

9.6 425 Insufficient Space on Resource

   The resource does not have sufficient space to record the state of
   the resource after the execution of this method.




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10 Multi-Status Response

   The default 207 Multi-Status response body is a text/xml HTTP entity
   that contains a single XML element called multistatus, which
   contains a set of XML elements called response 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.

11 XML Element Definitions

   In the section below, the final line of each section gives the
   element type declaration using the format defined in [Bray, Paoli,
   Sperberg-McQueen, 1998]. The "Value" field, where present, specifies
   futher restrictions on the allowable contents of the XML element
   using BNF (i.e., to further restrict the values of a PCDATA
   element).

11.1 activelock XML Element

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

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

11.1.1    depth XML Element

   Name:       depth
   Namespace:  DAV:
   Purpose:    The value of the depth header used to create a lock.
   Value:      "0" | "infinity"

   <!ELEMENT depth (#PCDATA) >

11.1.2    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 5.4).

   <!ELEMENT locktoken (href+) >

11.1.3    timeout XML Element

   Name:       timeout
   Namespace:  DAV:
   Purpose:    The timeout associated with a lock

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   Value:      TimeType ;Defined in section 8.8

   <!ELEMENT timeout (#PCDATA) >

11.2 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 >

11.3 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 [Fielding et al., 1997]

   <!ELEMENT href (#PCDATA)>

11.4 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+) >

11.4.1    dst XML Element

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

   <!ELEMENT dst (#PCDATA) >

11.4.2    src XML Element

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

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   Value:      URI

   <!ELEMENT src (#PCDATA) >

11.5 lockentry XML Element

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

   <!ELEMENT lockentry (lockscope, locktype) >

11.6 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?) >

11.7 lockscope XML Element

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

   <!ELEMENT lockscope (exclusive | shared) >

11.7.1    exclusive XML Element

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

   <!ELEMENT exclusive EMPTY >

11.7.2    shared XML Element

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

   <!ELEMENT shared EMPTY >

11.8 locktype XML Element

   Name:       locktype
   Namespace:  DAV:


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

   <!ELEMENT locktype (write) >

11.8.1    write XML Element

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

   <!ELEMENT write EMPTY >

11.9 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?) >

11.9.1    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?) >

11.9.1.1  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


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   element MUST only list the names of properties to which the result
   in the status element applies.


   <!ELEMENT propstat (prop, status) >

11.9.1.2  status XML Element

   Name:       status
   Namespace:  DAV:
   Purpose:    Holds a single HTTP status-line
   Value:      status-line   ;status-line defined in [Fielding et al.,
   1997]

   <!ELEMENT status (#PCDATA) >

11.9.2    responsedescription XML Element

   Name:       responsedescription
   Namespace:  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) >

11.10     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>

11.11     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>



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11.12     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) >

11.12.1   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+) >

11.12.2   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 >


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11.13     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)+ >

11.13.1   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) >

11.13.2   set XML element

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

   <!ELEMENT set (prop) >

11.14     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) >





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11.14.1   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 >

11.14.2   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 >

12 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 [Bray, Paoli, Sperberg-
   McQueen, 1998]. The "Value" field, where present, specifies futher
   restrictions on the allowable contents of the XML element using BNF
   (i.e., to further restrict the values of a PCDATA element).

12.1 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) >

12.2 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.


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   <!ELEMENT displayname (#PCDATA) >

12.3 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 [Fielding et al., 1997]

   <!ELEMENT getcontentlanguage (#PCDATA) >

12.4 getcontentlength Property

   Name:       getcontentlength
   Namespace:  DAV:
   Purpose:    Contains the Content-Length header returned by a GET
   without accept headers.
   Description: The getcontentlength property MUST be defined on any
   DAV compliant resource that returns the Content-Length header in
   response to a GET.
   Value:      content-length ; see section 14.14 of [Fielding et al.,
   1997]

   <!ELEMENT getcontentlength (#PCDATA) >

12.5 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 [Fielding et
   al., 1997]

   <!ELEMENT getcontenttype (#PCDATA) >

12.6 getetag Property

   Name:       getetag
   Namespace:  DAV:
   Purpose:    Contains the ETag header returned by a GET without
   accept headers.
   Description: Note that the ETag on a resource may reflect changes in
   any part of the state of the resource, not necessarily just a change

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   to the response to the GET method.  For example, a change to a
   resource's access permissions may cause the ETag to change. The
   getetag property MUST be defined on any DAV compliant resource that
   returns the Etag header in response to a GET.
   Value:      entity-tag  ; defined in section 3.11 of [Fielding et
   al., 1997]

   <!ELEMENT getetag (#PCDATA) >

12.7 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 [Fielding et
   al., 1997]

   <!ELEMENT getlastmodified (#PCDATA) >

12.8 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)* >

12.8.1    Example - Retrieving the lockdiscovery Property

   >>Request

   PROPFIND /container/ HTTP/1.1
   Host: www.foo.bar
   Content-Length: xxxx
   Content-Type: text/xml

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>

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   <D:propfind>
     <D:prop><D:lockdiscovery/></D:prop>
   </D:propfind>

   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:multistatus>
     <D:response>
          <D:href>http://www.foo.bar/container/</D:href>
          <D:propstat>
               <D:prop>
                    <D:lockdiscovery>
                         <D:activelock>
                              <D:locktype><D:write/></D:locktype>
                              <D:lockscope><D:exclusive/></D:lockscope>
                              <D:depth>0</D:depth>
                              <D:owner>Jane Smith</D:owner>
                              <D:timeout>Infinite</D:timeout>
                              <D:locktoken>
                                   <D:href>
               opaquelocktoken:f81de2ad-7f3d-a1b2-4f3c-00a0c91a9d76
                                   </D:href>
                              </D:locktoken>
                         </D:activelock>
                    </D:lockdiscovery>
               </D:prop>
               <D:status>HTTP/1.1 200 OK</D:status>
          </D:propstat>
     </D:response>
   </D:multistatus>

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

   infinite timeout.

12.9 resourcetype Property

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

   <!ELEMENT resourcetype ANY >




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12.10     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)* >

12.10.1   Example - A source Property

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <?xml:namespace ns="http://www.foocorp.com/Project/" prefix="F" ?>
   <D:prop>

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

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

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12.11     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)* >

12.11.1   Example - Retrieving the supportedlock Property

   >>Request

   PROPFIND  /container/ HTTP/1.1
   Host: www.foo.bar
   Content-Length: xxxx
   Content-Type: text/xml

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:propfind>
     <D:prop><D:supportedlock/></D:prop>
   </D:propfind>























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   >>Response

   HTTP/1.1 207 Multi-Status
   Content-Type: text/xml
   Content-Length: xxxxx

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:multistatus>
     <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>


13 DAV XML Processing Instructions

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

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

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

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

14 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


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   executing OPTIONS on the resource, and examining the "DAV" header
   which is returned.

   Since this document describes extensions to the HTTP/1.1 protocol,
   minimally all DAV compliant resources, clients, and proxies MUST be
   compliant with [Fielding et al., 1997].

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

14.1 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.

14.2 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.

15 Internationalization Considerations

   In the realm of internationalization, this specification complies
   with the IETF Character Set Policy [Alvestrand, 1998]. In this
   specification, human-readable fields can be found either in the
   value of a property, or in an error message returned in a response
   entity body.  In both cases, the human-readable content is encoded
   using XML, which has explicit provisions for character set tagging
   and encoding, and requires that XML processors read XML elements
   encoded, at minimum, using the UTF-8 [Yergeau, 1998] encoding of the
   ISO 10646 multilingual plane.

   XML also provides a language tagging capability for specifying the
   language of the contents of a particular XML element.  XML uses
   either IANA registered language tags (see RFC 1766, [Alvestrand,
   1995]) or ISO 639 language tags [ISO-639] in the "xml:lang"
   attribute of an XML element to identify the language of its content
   and attributes.


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   WebDAV applications MUST support the character set tagging,
   character set encoding, and the language tagging functionality of
   the XML specification.

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

   The name of a property defined on a resource is a URI.  Although
   some applications (e.g., a generic property viewer) will display
   property URIs directly to their users, it is expected that the
   typical application will use a fixed set of properties, and will
   provide a mapping from the property name URI to a human-readable
   field when displaying the property name to a user.  It is only in
   the case where the set of properties is not known ahead of time that
   an application need display a property name URI to a user. We
   recommend that applications provide human-readable property names
   wherever feasible.

   For error reporting, we follow the convention of HTTP/1.1 status
   codes, including with each status code a short, English description

   of the code (e.g., 423 Locked).  While the possibility exists that a
   poorly crafted user agent would display this message to a user,
   internationalized applications will ignore this message, and display
   an appropriate message in the user's language and character set.

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

16 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 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.

16.1 Authentication of Clients



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

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

   WebDAV applications MUST support the Digest authentication scheme
   [Franks et al., 1997]. Since Digest authentication verifies that
   both parties to a communication know a shared secret, a password,
   without having to send that secret in the clear, Digest
   authentication avoids the security problems inherent in Basic
   authentication while providing a level of authentication which is
   useful in a wide range of scenarios.

16.2 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.

16.3 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

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   control techniques to prevent unwanted access to resources, rather
   than depending on the relative obscurity of their resource names.

16.4 Privacy Issues Connected to Locks

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

16.5 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.

16.6 Reduction of Security due to Source Link

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

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

   This specification defines a distinguished set of property names and
   XML elements 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
   5.4.

   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.

18 Terminology

   Collection - A resource that contains member resources and meets the
   requirements in section 4 of this specification.

   Member Resource - A resource contained by a collection.

   Internal Member Resource - A member resource of a collection whose
   URI is relative to the URI of the collection.

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

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

   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.



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19 Copyright

   The following copyright notice is copied from RFC 2026 [Bradner,
   1996], section 10.4, and describes the applicable copyright for this
   document.

   Copyright (C) The Internet Society April 5, 1998. All Rights
   Reserved.

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

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

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

20 Intellectual Property

   The following notice is copied from RFC 2026 [Bradner, 1996],
   section 10.4, and describes the position of the IETF concerning
   intellectual property claims made against this document.

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

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   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.

21 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, Henrik
   Nielsen, Kenji Ota, Bob Parker, Glenn Peterson, Jon Radoff, Saveen
   Reddy, Henry Sanders, Christopher Seiwald, Judith Slein, Mike
   Spreitzer, Einar Stefferud, Ralph Swick, Kenji Takahashi, Richard N.
   Taylor, Robert Thau, John Turner, Sankar Virdhagriswaran, Fabio
   Vitali, Gregory Woodhouse, and Lauren Wood.

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

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














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22 References

22.1 Normative References

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

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

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

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

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

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

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

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

   [Leach, Salz, 1998] P. J. Leach, R. Salz, "UUIDs and GUIDs."
   Internet-draft, work-in-progress, February, 1998.
   ftp://ietf.org/internet-drafts/draft-leach-uuids-guids-01.txt

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

22.2 Informational References

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

   [Bray, Hollander, Layman, 1998] T. Bray, D. Hollander, A. Layman,
   "Name Spaces in XML" World Wide Web Consortium Working Draft,
   http://www.w3.org/TR/WD-xml-names.


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

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

   [Miller et al., 1996] J. Miller, T. Krauskopf, P. Resnick, W.
   Treese, "PICS Label Distribution Label Syntax and Communication
   Protocols" Version 1.1, World Wide Web Consortium Recommendation
   REC-PICS-labels-961031. http://www.w3.org/pub/WWW/TR/REC-PICS-
   labels-961031.html.

   [Slein et al., 1998] J. A. Slein, F. Vitali, E. J. Whitehead, Jr.,
   D. Durand, "Requirements for Distributed Authoring and Versioning
   Protocol for the World Wide Web." RFC 2291. Xerox, Univ. of Bologna,
   U.C. Irvine, Boston Univ. February, 1998.

   [Weibel et al., 1995] S. Weibel, J. Godby, E. Miller, R. Daniel,
   "OCLC/NCSA Metadata Workshop Report."
   http://purl.oclc.org/metadata/dublin_core_report.
































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23 Authors' Addresses

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

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

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

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

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




















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24 Appendices

24.1 Appendix 1 - WebDAV Document Type Definition

   This section provides a document type definition, following the
   rules in [Bray, Paoli, Sperberg-McQueen, 1998], for the XML elements
   used in the protocol stream and in the values of properties. It
   collects the element definitions given in sections 11 and 12.

   <!DOCTYPE webdav-1.0 [

   <!--============ XML Elements from Section 11 ==================-->

   <!ELEMENT activelock (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) >
   <!ELEMENT responsedescription (#PCDATA) >

   <!ELEMENT prop ANY >

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

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

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

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

   <!ELEMENT collection EMPTY >

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

   <!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)* >

   ]>

24.2 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
   verbatim from draft-newman-datetime-01.txt (expired).

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

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

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

   partial-time    = time-hour ":" time-minute ":" time-second

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                    [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.

24.3 Appendix 3 - Notes on Processing XML Elements

24.3.1    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
   delcared to be EMPTY, then either form <A></A> or <A/> may be used
   for empty elements.

24.3.2    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.

24.3.2.1  Example - XML Syntax Error


   The following request body for a PROPFIND method is illegal.

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <D:propfind>
     <D:allprop/>
     <D:propname/>
   </D:propfind>

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

   Imagine, however, that a server wanted to be "kind" and decided to
   pick the allprop element as the true element and respond to it.  A
   client running over a bandwidth limited line who intended to execute

   a propname would be in for a big surprise if the server treated the
   command as an allprop.

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

24.3.2.2  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" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <?xml:namespace ns="http://www.foo.bar/standards/props/" prefix="E"
   ?>
   <D:propfind>
     <E:expired-props/>
   </D:propfind>

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

   <?xml version="1.0" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <?xml:namespace ns="http://www.foo.bar/standards/props/" prefix="E"
   ?>
   <D:propfind>
   </D:propfind>

   As the server does not understand the expired-props element, by the
   rules of XML, it must ignore it.  Thus the server sees an empty
   propfind, which by the definition of the propfind element is
   illegal.




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   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" ?>
   <?xml:namespace ns="DAV:" prefix="D" ?>
   <?xml:namespace ns="http://www.foo.bar/standards/props/" prefix="E"
   ?>
   <D:propfind>
     <D:propname/>
     <E:leave-out>*boss*</E:leave-out>
   </D:propfind>

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

24.4 Appendix 4 -- XML Namespaces for WebDAV

24.4.1    Introduction

   To provide a unique space of XML element names which has
   decentralized extensibility, this specification uses a feature of
   XML known as XML "namespaces".  This appendix provides a normative
   reference for XML namespace functionality for implementations of
   this specification.  All DAV compliant systems MUST support the XML
   namespace extension as specified in this appendix.

   The remainder of this appendix is intended to match, as closely as
   needed, the text in WD-xml-names-19980327, "Namespaces in XML",
   edited by Tim Bray, Dave Hollander, and Andrew Layman [Bray,
   Hollander, Layman, 1998].  To meet this goal, the text in this
   appendix is mostly quoted verbatim from that source.  The notational
   conventions and BNF productions in this appendix match those of the
   XML specification [Bray, Paoli, Spreberg-McQueen, 1998]

   XML namespaces are based on the use of qualified names, which
   contain a single colon, separating the name into a namespace prefix
   and the local name.  The prefix, which is mapped to a URI, selects a
   namespace.  The combination of the universally-managed URI namespace
   and the local schema namespace produces names that are guaranteed
   universally unique.

   URIs can contain characters not allowed in names, and so cannot be
   used directly as namespace prefixes.  Therefore, the namespace
   prefix serves as a proxy for a URI.  A special processing
   instruction described below is used to declare the association of
   the namespace prefix with a URI; software which supports this
   namespace proposal must recognize and act on it.


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   A namespace is declared using a reserved processing instruction as
   follows:

24.4.2    Namespace Declaration PI

   [1]  NamespacePI ::=  '<?xml:namespace' (S (PrefixDef | NSDef |
   SrcDef))+ '?>'  [  NSC: Required Parts ]
   [2]  NSDef ::=  'ns' Eq SystemLiteral [  NSC: No Fragments ]
   [3]  SrcDef ::=  'src' Eq SystemLiteral
   [4]  PrefixDef ::=  'prefix' Eq ("'" NCName "'" | '"' NCName '"')
   [5]  NCName ::=  (Letter | '_') (NCNameChar)* /*  An XML Name, minus
   the ":" */
   [6]  NCNameChar ::=  Letter | Digit | '.' | '-' | '_' |
   CombiningChar | Extender

   [Definition:] The SystemLiteral in the NSDef production is a URI
   which functions as a namespace name to identify the namespace.  The
   SystemLiteral in the SrcDef production is an optional URI which may
   be used to retrieve the schema, if one is provided.  Some namespaces
   need no schemas; this specification does not depend on their
   existence, or on the use of any particular machine- or human-
   readable syntax in the schema.

   [Definition:] The NCName in the PrefixDef production gives the
   namespace prefix used to associate names in an XML document with
   this namespace.

   Namespace Constraint: Required Parts

   A namespace declaration must contain exactly one NSDef, exactly one
   PrefixDef and zero or one SrcDef.

   Namespace Constraint: No Fragments

   The SystemLiteral in the NSDef production must contain a URI, not
   including an attached #-separated fragment identifier.

   The namespace name, to serve its intended purpose, should have the
   characteristics of uniqueness and persistence.  It is not a goal
   that it be directly usable for retrieval of a schema (if any
   exists).

24.4.2.1  Examples of namespace declarations:

   <?xml:namespace ns='http://www.microsoft.com/' prefix='ms' ?>
   <?xml:namespace ns='urn:ISBN:0-395-36341-6/' prefix='bk' ?>
   <?xml:namespace ns='urn:uuid:C4ED1820-6207-11d1-A29F-00AA00C14882/'
                   src='http://www.w3.org' prefix='w3c' ?>





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24.4.3    Placing Declarations in Documents

   Namespace declarations must be located in the prolog of an XML
   document, after the XML Declaration (if any) and before the DTD (if
   any).  This effectively makes the scope of namespace prefixes global
   to the whole document, including the DTD.  It also means that should
   a processor wish to insert its own qualified names, it need only
   read the namespace declarations from the prolog to be sure of
   generating a new, unique, namespace prefix.

   In XML documents conforming to this specification, the prolog must
   match the following production:

24.4.4    Prolog with Namespace Declarations

   [7]  prolog ::=  XMLDecl? (NamespacePI | Misc)* (doctypedecl Misc*)?
   [  NSC: Unique Prefix ]

   Note that the namespace declarations are ordinary processing
   instructions which the XML processor will pass to the application as
   it does any other.

   Namespace Constraint: Unique Prefix

   A namespace prefix may not be declared more than once; i.e. there
   may not be two PrefixDefs which contain the same NCName string.

24.4.5    Qualified Names

   [Definition:] In XML documents conforming to this specification,
   some names (constructs corresponding to the nonterminal Name) may be
   given as qualified names, defined as follows:

   Qualified Name

   [8]  QName ::=  (Prefix ':')? LocalPart
   [9]  Prefix ::=  NCName [  NSC: Prefix Declared ]
   [10]  LocalPart ::=  NCName

   The Prefix provides the namespace prefix part of the qualified name,
   and must be associated with defining schema through the URI in the
   applicable namespace declaration.

   [Definition:] The LocalPart provides the local name part of the
   qualified name.

   Namespace Constraint: Prefix Declared

   The namespace prefix, unless it is "xml", must have been declared in
   a namespace declaration.  The namespace prefix xml is reserved and
   considered to have been implicitly declared.  No other prefix


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   beginning with the three-letter sequence x m, l, in any case
   combination, is allowed.

24.4.6    Universal Names

   [Definition:] For each qualified name, there is a corresponding
   universal name, which is an ordered pair containing first, the
   namespace name associated with its prefix, and second, its local
   name.

   A universal name is independent of the prefix in use in any
   particular XML document; thus, universal names provide a basis for
   comparing named objects located in different XML documents.

24.4.7    Using Qualified Names

   In XML documents conforming to this specification, element types are
   given as qualified names, as follows.  In the productions below, the
   nonterminals (STag, ETag, EmptyElement, and Attribute) are taken
   from the XML specification [XML]; the productions in all cases match
   a subset of the strings matched by those of the same name in the XML
   spec.

   Start-tag
   [11]  STag ::=  '<' QName (S Attribute)* S? '>'
   [12]  ETag ::=  '</' QName S? '>'
   [13]  EmptyElement ::=  '<' QName (S Attribute)* S? '/>'

24.4.8    Processing instruction

   Targets are given as qualified names, as follows:

   PI Target

   [15]  PITarget ::=  QName  [  NSC: Declare Before Use ]

   Namespace Constraint: Declare Before Use

   When a PI target, aside from that in a namespace declaration PI, is
   qualified with a prefix, that prefix must be declared at a location
   in the document which precedes its use.

24.4.9    Scope and Meaning of Qualified Names

   [Note to the reader: This section does not appear in [Bray,
   Hollander, Layman, 1998], 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 schema URI of the
   namespace.  The scope of a namespace in a qualified name is limited


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   to a single element tag.  Every start tag, end tag, or empty XML
   element from a namespace MUST include the namespace name in the tag.

   Scope Example

   <?xml:namespace ns="http://www.del.jensen.org/" prefix="del" ?>
   <del:glider>
     <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".  Since
   the scope of a namespace is limited to a single element, each start
   tag, end tag, and empty element tag in the example includes the
   short name of the namespace, "del" as part of the qualified name.

   <?xml:namespace ns="http://www.del.jensen.org/" prefix="bar" ?>
   <bar:glider>
     <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.

   <?xml:namespace ns="http://www.del.jensen.org/glide" prefix="foo" ?>
   <foo:r>
     <foo:rname>
          Johnny Updraft
     </foo:rname>
     <foo:raccidents/>
   </foo:r>

   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.





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