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Versions: 00 01 02 03 04 05 06 07 08 09 10 RFC 3648

Network Working Group                                           J. Slein
Internet Draft                                                     Xerox
Expires: August 2003                                        J. Whitehead
                                                         U.C. Santa Cruz
                                                             J. Crawford
                                                                     IBM
                                                           J. F. Reschke
                                                              greenbytes
                                                           February 2003


                  WebDAV Ordered Collections Protocol
                 draft-ietf-webdav-ordering-protocol-05



Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026. Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups. Note that other groups may also distribute
   working documents as Internet-Drafts.

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

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

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

   This Internet-Draft will expire in August 2003.


Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.


Abstract

   This specification extends the WebDAV Distributed Authoring Protocol
   to support server-side ordering of collection members. Of particular
   interest are orderings that are not based on property values, and so



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   cannot be achieved using a search protocol's ordering option and
   cannot be maintained automatically by the server. Protocol elements
   are defined to let clients specify the position in the ordering of
   each collection member, as well as the semantics governing the
   ordering.

   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://lists.w3.org/Archives/Public/w3c-dist-auth/.






































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   Table of Contents

      Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . .   1
      Table of Contents  . . . . . . . . . . . . . . . . . . . . . .   3
      1 Notational Conventions . . . . . . . . . . . . . . . . . . .   4
      2 Introduction . . . . . . . . . . . . . . . . . . . . . . . .   5
      3 Terminology  . . . . . . . . . . . . . . . . . . . . . . . .   6
      4 Overview of Ordered Collections  . . . . . . . . . . . . . .   7
        4.1 Additional Collection properties . . . . . . . . . . . .   7
          4.1.1 DAV:ordering-type (protected)  . . . . . . . . . . .   8
      5 Creating an Ordered Collection . . . . . . . . . . . . . . .   9
        5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . .   9
        5.2 Example: Creating an Ordered Collection  . . . . . . . .  10
      6 Setting the Position of a Collection Member  . . . . . . . .  11
        6.1 Overview . . . . . . . . . . . . . . . . . . . . . . . .  11
        6.2 Examples: Setting the Position of a Collection Member  .  12
      7 Changing a Collection Ordering: ORDERPATCH method  . . . . .  14
        7.1 Example: Changing a Collection Ordering  . . . . . . . .  16
        7.2 Example: Failure of an ORDERPATCH Request  . . . . . . .  17
      8 Listing the Members of an Ordered Collection . . . . . . . .  20
        8.1 Example: PROPFIND on an Ordered Collection . . . . . . .  20
      9 Relationship to versioned collections  . . . . . . . . . . .  24
        9.1 Additional semantics for collection version properties .  24
      10 Capability Discovery  . . . . . . . . . . . . . . . . . . .  25
        10.1 Example: Using OPTIONS for the Discovery of Support for
      Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . .  25
        10.2 Example: Using Live Properties for the Discovery of
      Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . .  26
      11 Security Considerations . . . . . . . . . . . . . . . . . .  28
        11.1 Denial of Service and DAV:ordering-type . . . . . . . .  28
      12 Internationalization Considerations . . . . . . . . . . . .  29
      13 IANA Considerations . . . . . . . . . . . . . . . . . . . .  30
      14 Copyright . . . . . . . . . . . . . . . . . . . . . . . . .  31
      15 Intellectual Property . . . . . . . . . . . . . . . . . . .  32
      16 Acknowledgements  . . . . . . . . . . . . . . . . . . . . .  33
      Normative References . . . . . . . . . . . . . . . . . . . . .  34
      Author's Addresses . . . . . . . . . . . . . . . . . . . . . .  34
      A Extensions to the WebDAV Document Type Definition  . . . . .  36
      B Change Log . . . . . . . . . . . . . . . . . . . . . . . . .  37
        B.1 Since draft-ietf-webdav-ordering-protocol dated December
      1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  37
        B.2 Since draft-ietf-webdav-ordering-protocol-02 . . . . . .  37
        B.3 Since draft-ietf-webdav-ordering-protocol-03 . . . . . .  37
        B.4 Since draft-ietf-webdav-ordering-protocol-04 . . . . . .  38
      Index  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  39






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1 Notational Conventions

   Since this document describes a set of extensions to the WebDAV
   Distributed Authoring Protocol [RFC2518], itself an extension to the
   HTTP/1.1 protocol, the augmented BNF used here to describe protocol
   elements is exactly the same as described in Section 2.1 of HTTP
   [RFC2616]. Since this augmented BNF uses the basic production rules
   provided in Section 2.2 of HTTP, 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 [RFC2119].






































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2 Introduction

   This specification builds on the collection infrastructure provided
   by the WebDAV Distributed Authoring Protocol, adding support for the
   server-side ordering of collection members.

   There are many scenarios where it is useful to impose an ordering on
   a collection at the server, such as expressing a recommended access
   order, or a revision history order. The members of a collection might
   represent the pages of a book, which need to be presented in order if
   they are to make sense. Or an instructor might create a collection of
   course readings, which she wants to be displayed in the order they
   are to be read.

   Orderings may be based on property values, but this is not always the
   case. The resources in the collection may not have properties that
   can be used to support the desired ordering. Orderings based on
   properties can be obtained using a search protocol's ordering option,
   but orderings not based on properties cannot. These orderings
   generally need to be maintained by a human user.

   The ordering protocol defined here focuses on support for such human-
   maintained orderings. Its protocol elements allow clients to specify
   the position of each collection member in the collection's ordering,
   as well as the semantics governing the ordering. The protocol is
   designed to allow support to be added in the future for orderings
   that are maintained automatically by the server.

   The remainder of this document is structured as follows: section 3
   defines terminology that will be used throughout the specification.
   Section 4 provides an overview of ordered collections. Section 5
   describes how to create an ordered collection, and section 6
   discusses how to set a member's position in the ordering of a
   collection. Section 7 explains how to change a collection ordering.
   Section 8 discusses listing the members of an ordered collection.
   Section 9 discusses the impact on version-controlled collections (as
   defined in [RFC3253]. Section 10 describes capability discovery.
   Section 11 through section 13 discuss security, internationalization,
   and IANA considerations. The remaining sections provide supporting
   information.











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3 Terminology

   The terminology used here follows that in [RFC2518] and [RFC3253].
   Definitions of the terms resource, Uniform Resource Identifier (URI),
   and Uniform Resource Locator (URL) are provided in [RFC2396].

   Ordered Collection

      A collection for which the results from a PROPFIND request are
      guaranteed to be in the order specified for that collection


   Unordered Collection

      A collection for which the client cannot depend on the
      repeatability of the ordering of results from a PROPFIND request


   Client-Maintained Ordering

      An ordering of collection members that is maintained on the server
      based on client requests specifying the position of each
      collection member in the ordering


   Server-Maintained Ordering

      An ordering of collection members that is maintained automatically
      by the server, based on a client's choice of ordering semantics


   This document uses the terms "precondition" as "postcondition" as
   defined in [RFC3253]. Servers should report pre-/postcondition
   failures as described in section 1.6 of this document.

















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4 Overview of Ordered Collections

   If a collection is unordered, the client cannot depend on the
   repeatability of the ordering of results from a PROPFIND request. By
   specifying an ordering for a collection, a client requires the server
   to follow that ordering whenever it responds to a PROPFIND request on
   that collection.

   Server-side orderings may be client-maintained or server-maintained.
   For client-maintained orderings, a client must specify the ordering
   position of each of the collection's members, either when the member
   is added to the collection (using the Position header) or later
   (using the ORDERPATCH method). For server-maintained orderings, the
   server automatically positions each of the collection's members
   according to the ordering semantics. This specification supports only
   client-maintained orderings, but is designed to allow future
   extension to server-maintained orderings.

   A collection that supports ordering is not required to be ordered.

   If a collection is ordered, each of its internal member URIs MUST be
   in the ordering exactly once, and the ordering MUST NOT include any
   URI that is not an internal member of the collection. The server is
   responsible for enforcing these constraints on orderings. The server
   MUST remove an internal member URI from the ordering when it is
   removed from the collection. The server MUST add an internal member
   URI to the ordering when it is added to the collection.

   Only one ordering can be attached to any collection. Multiple
   orderings of the same resources can be achieved by creating multiple
   collections referencing those resources, and attaching a different
   ordering to each collection.

   An ordering is considered to be part of the state of a collection
   resource. Consequently, the ordering is the same no matter which URI
   is used to access the collection and is protected by locks or access
   control constraints on the collection.


4.1 Additional Collection properties

   A DAV:allprop PROPFIND request SHOULD NOT return any of the
   properties defined in this document.








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4.1.1 DAV:ordering-type (protected)

   Indicates whether the collection is ordered and, if so, uniquely
   identifies the semantics of the ordering being used. May also point
   to an explanation of the semantics in human and / or machine-readable
   form. At a minimum, this allows human users who add members to the
   collection to understand where to position them in the ordering. This
   property cannot be set using PROPPATCH. Its value can only be set by
   including the Ordering-Type header with a MKCOL request or by
   submitting an ORDERPATCH request.

   Ordering types are identified by URIs that uniquely identify the
   semantics of the collection's ordering. Two following two URIs are
   predefined:

   DAV:custom    The value DAV:custom indicates that the collection is
                 ordered, but the semantics governing the ordering are
                 not being advertised.
   DAV:unordered The value DAV:unordered indicates that the collection
                 is not ordered. That is, the client cannot depend on
                 the repeatability of the ordering of results from a
                 PROPFIND request.



   An ordering-aware client interacting with an ordering-unaware server
   (e.g., one that is implemented only according to [RFC2518]) SHOULD
   assume that if a collection does not have the DAV:ordering-type
   property, the collection is unordered.




   <!ELEMENT ordering-type (href) >

















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5 Creating an Ordered Collection


5.1 Overview

   When a collection is created, the client MAY request that it be
   ordered and specify the semantics of the ordering by using the new
   Ordering-Type header (defined below) with a MKCOL request.

   For collections that are ordered, the client SHOULD identify the
   semantics of the ordering with a URI in the Ordering-Type header,
   although the client MAY simply set the header value to DAV:custom to
   indicate that the collection is ordered but the semantics of the
   ordering are not being advertised. Setting the value to a URI that
   identifies the ordering semantics provides the information a human
   user or software package needs to insert new collection members into
   the ordering intelligently. Although the URI in the Ordering-Type
   header MAY point to a resource that contains a definition of the
   semantics of the ordering, clients SHOULD NOT access that resource,
   in order to avoid overburdening its server. A value of DAV:unordered
   in the Ordering-Type header indicates that the client wants the
   collection to be unordered. If the Ordering-Type header is not
   present, the collection will be unordered.

   Additional Marshalling:





         Ordering-Type = "Ordering-Type" ":" absoluteURI
         ; absoluteURI: see RFC2396, section 3




      The URI "DAV:unordered" indicates that the collection is not
      ordered, while "DAV:custom" indicates that the collection is to be
      ordered, but the semantics of the ordering is not being
      advertised. Any other URI value indicates that the collection is
      ordered, and identifies the semantics of the ordering.


   Additional Preconditions:

      (DAV:ordered-collections-supported): the server must support
      ordered collections where the new collection is to be created.




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   Additional Postconditions:

      (DAV:ordering-type-set): the collection was created with the
      specified ordering semantics.



5.2 Example: Creating an Ordered Collection


   >> Request:

   MKCOL /theNorth/ HTTP/1.1
   Host: example.org
   Ordering-Type: http://example.org/orderings/compass.html




   >> Response:

   HTTP/1.1 201 Created



   In this example a new, ordered collection was created. Its
   DAV:ordering-type property has as its value the URI from the
   Ordering-Type header, http://example.org/orderings/compass.html. In
   this case, the URI identifies the semantics governing a client-
   maintained ordering. As new members are added to the collection,
   clients or end users can use the semantics to determine where to
   position the new members in the ordering.



















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6 Setting the Position of a Collection Member


6.1 Overview

   When a new member is added to a collection with a client-maintained
   ordering (for example, with PUT, COPY, or MKCOL), its position in the
   ordering can be set with the new Position header. The Position header
   allows the client to specify that an internal member URI should be
   first in the collection's ordering, last in the collection's
   ordering, immediately before some other internal member URI in the
   collection's ordering, or immediately after some other internal
   member URI in the collection's ordering.

   If the Position request header is not used when adding a member to an
   ordered collection, then:

   o  If the request is replacing an existing resource, the server MUST
      preserve the present ordering.

   o  If the request is adding a new internal member URI to the
      collection, the server MUST append the new member to the end of
      the ordering.

   Additional Marshalling:





         Position = "Position" ":" ("first" | "last" |
                                   (("before" | "after") segment))




      segment is defined in Section 3.3 of [RFC2396].

      The segment is interpreted relative to the collection to which the
      new member is being added.

      The server MUST insert the new member into the ordering at the
      location specified in the Position header, if one is present (and
      if the collection is ordered).

      The "first" keyword indicates the new member is put in the
      beginning position in the collection's ordering, while "last"
      indicates the new member is put in the final position in the



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      collection's ordering. The "before" keyword indicates the new
      member is added to the collection's ordering immediately prior to
      the position of the member identified in the segment. Likewise,
      the "after" keyword indicates the new member is added to the
      collection's ordering immediately following the position of the
      member identified in the segment.

      If the request is replacing an existing resource, and the Position
      header is present, the server MUST remove the internal member URI
      from its previous position, and then insert it at the requested
      position.


   Additional Preconditions:

      (DAV:collection-must-be-ordered): the target collection must be
      ordered.

      (DAV:segment-must-identify-member): the referenced segment must
      identify a resource that exists and is different from the affected
      resource.


   Additional Postconditions:

      (DAV:position-set): the newly created collection member was
      created at the specified position.



6.2 Examples: Setting the Position of a Collection Member


   >> Request:

   COPY /~user/dav/spec08.html HTTP/1.1
   Host: example.org
   Destination: http://example.org/~slein/dav/spec08.html
   Position: after requirements.html




   >> Response:

   HTTP/1.1 201 Created





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   This request resulted in the creation of a new resource at
   example.org/~slein/dav/spec08.html. The Position header in this
   example caused the server to set its position in the ordering of the
   /~slein/dav/ collection immediately after requirements.html.


   >> Request:

   MOVE /i-d/draft-webdav-prot-08.txt HTTP/1.1
   Host: example.org
   Destination: http://example.org/~user/dav/draft-webdav-prot-08.txt
   Position: first




   >> Response:

   HTTP/1.1 409 Conflict
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxxx

   <?xml version="1.0" encoding="utf-8" ?>
   <D:error xmlns:D="DAV:">
     <D:collection-must-be-ordered/>
   </D:error>



   In this case, the server returned a 409 (Conflict) status code
   because the /~user/dav/ collection is an unordered collection.
   Consequently, the server was unable to satisfy the Position header.



















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7 Changing a Collection Ordering: ORDERPATCH method

   The ORDERPATCH method is used to change the ordering semantics of a
   collection or to change the order of the collection's members in the
   ordering or both.

   The server MUST apply the changes in the order they appear in the
   order XML element. The server MUST either apply all the changes or
   apply none of them. If any error occurs during processing, all
   executed changes MUST be undone and a proper error result returned.

   If an ORDERPATCH request changes the ordering semantics, but does not
   completely specify the order of the collection members, the server
   MUST assign a position in the ordering to each collection member for
   which a position was not specified. These server-assigned positions
   MUST all follow the last one specified by the client. The result is
   that all members for which the client specified a position are at the
   beginning of the ordering, followed by any members for which the
   server assigned positions.

   If an ORDERPATCH request does not change the ordering semantics, any
   member positions not specified in the request MUST remain unchanged.

   A request to reposition a collection member at the same place in the
   ordering is not an error.

   Additional Marshalling:

      The request body MUST be DAV:orderpatch element.





         <!ELEMENT orderpatch (ordering-type?, ordermember*) >

         <!ELEMENT ordermember (segment, position) >
         <!ELEMENT position (first | last | before | after)>
         <!ELEMENT segment (#PCDATA)>
         <!ELEMENT first EMPTY >
         <!ELEMENT last EMPTY >
         <!ELEMENT before segment >
         <!ELEMENT after segment >








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      PCDATA value: segment, as defined in section 3.3 of [RFC2396].

      The DAV:ordering-type property is modified according to the
      DAV:ordering-type element.

      The ordering of internal member URIs in the collection identified
      by the Request-URI is changed based on instructions in the
      ordermember XML elements. The ordermember XML elements identify
      the internal member URIs whose positions are to be changed, and
      describe their new positions in the ordering. Each new position
      can be specified as first in the ordering, last in the ordering,
      immediately before some other internal member URI, or immediately
      after some other internal member URI.

      If a response body for a successful request is included, it MUST
      be a DAV:orderpatch-response XML element. Note that this document
      does not define any elements for the ORDERPATCH response body, but
      the DAV:orderpatch-response element is defined to ensure
      interoperability between future extensions that do define elements
      for the ORDERPATCH response body.



         <!ELEMENT orderpatch-response ANY>




      Since multiple changes can be requested in a single ORDERPATCH
      request, if any problems are encountered, the server MUST return a
      207 (Multi-Status) response (defined in [RFC2518]), containing
      DAV:response elements for either the request-URI (when the
      DAV:ordering-type could not be modified) or URIs of collection
      members to be repositioned (when an individual positioning request
      expressed as DAV:ordermember could not be fulfilled).


   Preconditions:

      (DAV:collection-must-be-ordered): see section 6.1.

      (DAV:segment-must-identify-member): see section 6.1.


   Postconditions:

      (DAV:orderding-type-set): if the request body contained a
      DAV:ordering-type element, the DAV:ordering-type property (see



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      section 4.1.1) of the collection identified by the request-URI was
      set accordingly.

      (DAV:orderding-modified): if the request body contained
      DAV:ordermember elements, the ordering of internal member URIs in
      the collection identified by the request-URI has been changed
      based on instructions in the DAV:ordermember elements.



7.1 Example: Changing a Collection Ordering

   Consider a collection /coll-1/ whose DAV:ordering-type is DAV:whim,
   with bindings ordered as follows:




   three.html
   four.html
   one.html
   two.html




   >> Request:

   ORDERPATCH /coll-1/ HTTP/1.1
   Host: example.org
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxx

   <?xml version="1.0" ?>
   <d:orderpatch xmlns:d="DAV:">
      <d:ordering-type>
         <d:href>http://example.org/inorder.ord</d:href>
      </d:ordering-type>
      <d:ordermember>
         <d:segment>two.html</d:segment>
         <d:position><d:first/></d:position>
      </d:ordermember>
      <d:ordermember>
         <d:segment>one.html</d:segment>
         <d:position><d:first/></d:position>
      </d:ordermember>
      <d:ordermember>
         <d:segment>three.html</d:segment>



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         <d:position><d:last/></d:position>
      </d:ordermember>
      <d:ordermember>
         <d:segment>four.html</d:segment>
         <d:position><d:last/></d:position>
      </d:ordermember>
   </d:orderpatch>




   >> Response:

   HTTP/1.1 200 OK



   In this example, after the request has been processed, the
   collection's ordering semantics are identified by the URI
   http://example.org/inorder.ord. The value of the collection's
   DAV:ordering-type property has been set to this URI. The request also
   contains instructions for changing the positions of the collection's
   internal member URIs in the ordering to comply with the new ordering
   semantics. If href elements are relative URIs, as in this example,
   they are interpreted relative to the collection whose ordering is
   being modified. The DAV:ordermember elements are required to be
   processed in the order they appear in the request. Consequently,
   two.html is moved to the beginning of the ordering, and then one.html
   is moved to the beginning of the ordering. Then three.html is moved
   to the end of the ordering, and finally four.html is moved to the end
   of the ordering. After the request has been processed, the
   collection's ordering is as follows:




   one.html
   two.html
   three.html
   four.html




7.2 Example: Failure of an ORDERPATCH Request

   Consider a collection /coll-1/ with members ordered as follows:




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   nunavut.map
   nunavut.img
   baffin.map
   baffin.desc
   baffin.img
   iqaluit.map
   nunavut.desc
   iqaluit.img
   iqaluit.desc




   >> Request:

   ORDERPATCH /coll-1/ HTTP/1.1
   Host: www.nunanet.com
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxx

   <?xml version="1.0" ?>
   <d:orderpatch xmlns:d="DAV:">
      <d:ordermember>
         <d:segment>nunavut.desc</d:segment>
         <d:position>
            <d:after>
               <d:segment>nunavut.map</d:segment>
            </d:after>
         </d:position>
      </d:ordermember>
      <d:ordermember>
         <d:segment>iqaluit.map</d:segment>
         <d:position>
            <d:after>
               <d:segment>pangnirtung.img</d:segment>
            </d:after>
         </d:position>
      </d:ordermember>
   </d:orderpatch>




   >> Response:

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



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   <?xml version="1.0" ?>
   <d:multistatus xmlns:d="DAV:">
     <d:response>
       <d:href>http://www.nunanet.com/coll-1/iqaluit.map</d:href>
       <d:status>HTTP/1.1 403 Forbidden</d:status>
       <d:responsedescription>
         <d:error><d:segment-must-identify-member/></d:error>
         pangnirtung.img is not a collection member.
       </d:responsedescription>
     </d:response>
   </d:multistatus>



   In this example, the client attempted to position iqaluit.map after a
   URI that is not an internal member of the collection /coll-1/. The
   server responded to this client error with a 403 (Forbidden) status
   code, indicating the failed precondition DAV:segment-must-identify-
   member. Because ORDERPATCH is an atomic method, the request to
   reposition nunavut.desc (which would otherwise have succeeded) failed
   as well, but doesn't need to be expressed in the multistatus response
   body.





























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8 Listing the Members of an Ordered Collection

   A PROPFIND request is used to retrieve a listing of the members of an
   ordered collection, just as it is used to retrieve a listing of the
   members of an unordered collection.

   However, when responding to a PROPFIND on an ordered collection, the
   server MUST order the response elements according to the ordering
   defined on the collection. If a collection is unordered, the client
   cannot depend on the repeatability of the ordering of results from a
   PROPFIND request.

   In a response to a PROPFIND with Depth: infinity, members of
   different collections may be interleaved. That is, the server is not
   required to do a breadth-first traversal. The only requirement is
   that the members of any ordered collection appear in the order
   defined for the collection. Thus for the hierarchy illustrated in the
   following figure, where collection A is an ordered collection with
   the ordering B C D,




                       A
                      /|\
                     / | \
                    B  C  D
                   /  /|\
                  E  F G H



   it would be acceptable for the server to return response elements in
   the order A B E C F G H D. In this response, B, C, and D appear in
   the correct order, separated by members of other collections. Clients
   can use a series of Depth: 1 PROPFIND requests to avoid the
   complexity of processing Depth: infinity responses based on depth-
   first traversals.


8.1 Example: PROPFIND on an Ordered Collection

   Suppose a PROPFIND request is submitted to /MyColl/, which has its
   members ordered as follows.







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   /MyColl/
      lakehazen.html
      siorapaluk.html
      iqaluit.html
      newyork.html




   >> Request:

   PROPFIND /MyColl/ HTTP/1.1
   Host: example.org
   Depth: 1
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxxx

   <?xml version="1.0" ?>
   <D:propfind xmlns:D="DAV:">
     <D:prop xmlns:J="http://example.org/jsprops/">
       <D:ordering-type/>
       <D:resourcetype/>
       <J:latitude/>
    </D:prop>
   </D:propfind>




   >> Response:

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

   <?xml version="1.0" ?>
   <D:multistatus xmlns:D="DAV:"
                  xmlns:J="http://example.org/jsprops/">
      <D:response>
         <D:href>http://example.org/MyColl/</D:href>
         <D:propstat>
            <D:prop>
               <D:ordering-type>
                  <D:href>DAV:custom</D:href>
               </D:ordering-type>
               <D:resourcetype><D:collection/></D:resourcetype>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>



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         </D:propstat>
         <D:propstat>
            <D:prop>
               <J:latitude/>
            </D:prop>
            <D:status>HTTP/1.1 404 Not Found</D:status>
         </D:propstat>
      </D:response>
      <D:response>
         <D:href>http://example.org/MyColl/lakehazen.html</D:href>
         <D:propstat>
            <D:prop>
               <D:resourcetype/>
               <J:latitude>82N</J:latitude>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
         <D:propstat>
            <D:prop>
               <D:ordering-type/>
            </D:prop>
            <D:status>HTTP/1.1 404 Not Found</D:status>
         </D:propstat>
      </D:response>
      <D:response>
         <D:href
         >http://example.org/MyColl/siorapaluk.html</D:href>
         <D:propstat>
            <D:prop>
               <D:resourcetype/>
               <J:latitude>78N</J:latitude>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
         <D:propstat>
            <D:prop>
               <D:ordering-type/>
            </D:prop>
            <D:status>HTTP/1.1 404 Not Found</D:status>
         </D:propstat>
      </D:response>
      <D:response>
         <D:href>http://example.org/MyColl/iqaluit.html</D:href>
         <D:propstat>
            <D:prop>
               <D:resourcetype/>
               <J:latitude>62N</J:latitude>
            </D:prop>



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            <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
         <D:propstat>
            <D:prop>
               <D:ordering-type/>
            </D:prop>
            <D:status>HTTP/1.1 404 Not Found</D:status>
         </D:propstat>
      </D:response>
      <D:response>
         <D:href>http://example.org/MyColl/newyork.html</D:href>
         <D:propstat>
            <D:prop>
               <D:resourcetype/>
               <J:latitude>45N</J:latitude>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
         <D:propstat>
            <D:prop>
               <D:ordering-type/>
            </D:prop>
            <D:status>HTTP/1.1 404 Not Found</D:status>
         </D:propstat>
         </D:propstat>
      </D:response>
   </D:multistatus>



   In this example, the server responded with a list of the collection
   members in the order defined for the collection.




















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9 Relationship to versioned collections

   The Versioning Extensions to WebDAV [RFC3253] introduce the concept
   of versioned collections, recording both the dead properties and the
   set of internal version-controlled bindings. This section defines how
   this feature interacts with ordered collections.

   This specification considers both the ordering type (DAV:ordering-
   type property) and the ordering of collection members to be part of
   the state of a collection. Therefore both MUST be recorded upon
   CHECKIN or VERSION-CONTROL, and both MUST be restored upon CHECKOUT,
   UNCHECKOUT or UPDATE (where for compatibility with RFC3253, only the
   ordering of version-controlled members needs to be maintained).


9.1 Additional semantics for collection version properties

   Although this specification defines the property DAV:ordering-type to
   be protected, it MUST be recorded in a collection version.

   The property DAV:version-controlled-binding-set ([RFC3253], section
   14.2.1) records the set of version-controlled bindings in the
   collection. For ordered collections, the DAV:version-controlled-
   binding elements MUST appear in the ordering defined for the checked-
   in ordered collection.


























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10 Capability Discovery

   Sections 9.1 and 15 of [RFC2518] describe the use of compliance
   classes with the DAV header in responses to OPTIONS, to indicate
   which parts of the Web Distributed Authoring protocols the resource
   supports. This specification defines an OPTIONAL extension to
   [RFC2518]. It defines a new compliance class, called ordered-
   collections, for use with the DAV header in responses to OPTIONS
   requests. If a collection resource does support ordering, its
   response to an OPTIONS request may indicate that it does, by listing
   the new ORDERPATCH method as one it supports, and by listing the new
   ordered-collections compliance class in the DAV header.

   When responding to an OPTIONS request, only a collection or a null
   resource can include ordered-collections in the value of the DAV
   header. By including ordered-collections, the resource indicates that
   its internal member URIs can be ordered. It implies nothing about
   whether any collections identified by its internal member URIs can be
   ordered.

   Furthermore, RFC 3253 [RFC3253] introduces the live properties
   DAV:supported-method-set (section 3.1.3) and DAV:supported-live-
   property-set (section 3.1.4). Servers MUST support these properties
   as defined in RFC 3253.


10.1 Example: Using OPTIONS for the Discovery of Support for Ordering


   >> Request:

   OPTIONS /somecollection/ HTTP/1.1
   Host: example.org




   >> Response:

   HTTP/1.1 200 OK
   Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE
   Allow: MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, ORDERPATCH
   DAV: 1, 2, ordered-collections



   The DAV header in the response indicates that the resource
   /somecollection/ is level 1 and level 2 compliant, as defined in



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   [RFC2518]. In addition, /somecollection/ supports ordering. The Allow
   header indicates that ORDERPATCH requests can be submitted to
   /somecollection/.


10.2 Example: Using Live Properties for the Discovery of Ordering


   >> Request:

   PROPFIND /somecollection HTTP/1.1
   Depth: 0
   Content-Type: text/xml; charset="utf-8"
   Content-Length: xxx

   <?xml version="1.0" encoding="UTF-8" ?>
   <propfind xmlns="DAV:">
     <prop>
       <supported-live-property-set/>
       <supported-method-set/>
     </prop>
   </propfind>




   >> Response:

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

   <?xml version="1.0" encoding="utf-8" ?>
   <multistatus xmlns="DAV:">
     <response>
       <href>http://example.org/somecollection</href>
       <propstat>
         <prop>
           <supported-live-property-set>
             <supported-live-property>
               <prop><ordering-type/></prop>
             </supported-live-property>
             <!-- ... other live properties omitted for brevity ... -->
           </supported-live-property-set>
           <supported-method-set>
             <supported-method name="COPY" />
             <supported-method name="DELETE" />
             <supported-method name="GET" />



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             <supported-method name="HEAD" />
             <supported-method name="LOCK" />
             <supported-method name="MKCOL" />
             <supported-method name="MOVE" />
             <supported-method name="OPTIONS" />
             <supported-method name="ORDERPATCH" />
             <supported-method name="POST" />
             <supported-method name="PROPFIND" />
             <supported-method name="PROPPATCH" />
             <supported-method name="PUT" />
             <supported-method name="TRACE" />
             <supported-method name="UNLOCK" />
           </supported-method-set>
         </prop>
         <status>HTTP/1.1 200 OK</status>
       </propstat>
     </response>
   </multistatus>



   Note that actual responses MUST contain a complete list of supported
   live properties.




























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11 Security Considerations

   This section is provided to make WebDAV applications aware of the
   security implications of this protocol.

   All of the security considerations of HTTP/1.1 and the WebDAV
   Distributed Authoring Protocol specification also apply to this
   protocol specification. In addition, ordered collections introduce a
   new security concern. This issue is detailed here.


11.1 Denial of Service and DAV:ordering-type

   There may be some risk of denial of service at sites that are
   advertised in the DAV:ordering-type property of collections. However,
   it is anticipated that widely-deployed applications will use hard-
   coded values for frequently-used ordering semantics rather than
   looking up the semantics at the location specified by DAV:ordering-
   type. This risk will be further reduced if clients observe the
   recommendation of section 5.1 that they not send requests to the URI
   in DAV:ordering-type.






























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12 Internationalization Considerations

   This specification follows the practices of [RFC2518] in encoding all
   human-readable content using [XML] and in the treatment of names.
   Consequently, this specification complies with the IETF Character Set
   Policy [RFC2277].

   WebDAV applications MUST support the character set tagging, character
   set encoding, and the language tagging functionality of the XML
   specification. This constraint ensures that the human-readable
   content of this specification complies with [RFC2277].

   As in [RFC2518], names in 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. The names of XML elements used in
   this specification are English names encoded in UTF-8.

   For error reporting, [RFC2518] follows the convention of HTTP/1.1
   status codes, including with each status code a short, English
   description of the code (e.g., 423 Locked). Internationalized
   applications will ignore this message, and display an appropriate
   message in the user's language and character set.

   This specification introduces no new strings that are displayed to
   users as part of normal, error-free operation of the protocol.

   For rationales for these decisions and advice for application
   implementors, see [RFC2518].





















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13 IANA Considerations

   This document uses the namespaces defined by [RFC2518] for properties
   and XML elements. All other IANA considerations mentioned in
   [RFC2518] also apply to this document.














































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14 Copyright

   To be supplied by the RFC Editor.
















































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15 Intellectual Property

   To be supplied by the RFC Editor.
















































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16 Acknowledgements

   This draft has benefited from thoughtful discussion by Jim Amsden,
   Steve Carter, Tyson Chihaya, Geoff Clemm, Ken Coar, Ellis Cohen,
   Bruce Cragun, Jim Davis, Spencer Dawkins, Mark Day, Rajiv Dulepet,
   David Durand, Chuck Fay, Roy Fielding, Yaron Goland, Fred Hitt, Alex
   Hopmann, Marcus Jager, Chris Kaler, Manoj Kasichainula, Rohit Khare,
   Daniel LaLiberte, Lisa Lippert, Steve Martin, Larry Masinter, Jeff
   McAffer, Surendra Koduru Reddy, Max Rible, Sam Ruby, Bradley
   Sergeant, Nick Shelness, John Stracke, John Tigue, John Turner, Kevin
   Wiggen, and others.








































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Normative References


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

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

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

   [RFC2518]  Goland, Y., Whitehead, E., Faizi, A., Carter, S.R. and
              Jensen, D., "HTTP Extensions for Distributed Authoring --
              WEBDAV", RFC 2518, February 1999.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P. and Berners-Lee, T., "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3253]  Clemm, G., Amsden, J., Ellison, T., Kaler, C. and
              Whitehead, J., "Versioning Extensions to WebDAV", RFC
              3253, March 2002.

   [XML]      Bray, T., Paoli, J., Sperberg-McQueen, C.M. and Maler, E.,
              "Extensible Markup Language (XML) 1.0 (2nd ed)", W3C REC-
              xml, October 2000.


Author's Addresses

   Judith Slein
   Xerox Corporation
   800 Phillips Road, 105-50C
   Webster, NY 14580

   EMail: jslein@crt.xerox.com

   Jim Whitehead
   UC Santa Cruz, Dept. of Computer Science
   1156 High Street
   Santa Cruz, CA 95064
   US

   EMail: ejw@cse.ucsc.edu





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   Jason Crawford
   IBM Research
   P.O. Box 704
   Yorktown Heights, NY 10598

   EMail: ccjason@us.ibm.com

   Julian F. Reschke
   greenbytes GmbH
   Salzmannstrasse 152
   Muenster, NW 48159
   Germany

   Phone: +49 251 2807760
   Fax:   +49 251 2807761
   EMail: julian.reschke@greenbytes.de
   URI:   http://greenbytes.de/tech/webdav/


































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A Extensions to the WebDAV Document Type Definition




   <!ELEMENT orderpatch (ordering-type?, ordermember*) >
   <!ELEMENT ordermember (segment, position) >
   <!ELEMENT ordering-type (href) >
   <!ELEMENT position (first | last | before | after)>
   <!ELEMENT first EMPTY >
   <!ELEMENT last EMPTY >
   <!ELEMENT before segment >
   <!ELEMENT after segment >
   <!ELEMENT segment (#PCDATA)>





































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B Change Log


B.1 Since draft-ietf-webdav-ordering-protocol dated December 1999

   Updated contact information for all previous authors.
   Specify charset when using text/xml media type.
   Made sure artwork fits into 72 columns.
   Removed "Public" header from OPTIONS example.
   Added Julian Reschke to list of authors.
   Fixed broken XML in PROPFIND example and added DAV:orderingtype to
   list of requested properties.
   Added support for DAV:supported-live-property-set and DAV:supported-
   method-set as mandatory features.


B.2 Since draft-ietf-webdav-ordering-protocol-02

   Updated change log to refer to expired draft version as "December
   1999" version.
   Started rewrite marshalling in RFC3253-style and added precondition
   and postcondition definitions.
   On his request, removed Geoff Clemm's name from the author list
   (moved to Acknowledgments).
   Renamed "References" to "Normative References".
   Removed reference to "MKREF" method.


B.3 Since draft-ietf-webdav-ordering-protocol-03

   Added a set of issues regarding marshalling.
   Changed host names to use proper "example" domain names (no change
   tracking). Fixed host/destination header conflicts. Fixed "allow"
   header (multiline). Removed irrelevant response headers. Abbreviated
   some URIs (no change tracking).
   Removed Jim Davis and Chuck Fay from the author list (and added them
   to the Acknowledgements section).
   Updated section on setting the position when adding new members,
   removed old section on Position header.
   Started work on Index section.
   Changed structure for section 7 (no change tracking).
   Removed header and XML elements section (contents moved to other
   sections).
   Started new section on relation to versioned collections as per
   RFC3253.
   Do not return 424's for in ORDERPATCH multistatus (it's atomic
   anyway).




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B.4 Since draft-ietf-webdav-ordering-protocol-04

   Added proper reference to definition of "Coded-URL".
   Closed issue ordering-type-values (content model simplified and XML
   element / DAV property renamed) and updated examples.
   Renamed precondition DAV:orderingtype-set to DAV:ordering-type-set
   (no change tracking).
   Closed issue ordered-header-name (header name changed to "ordering-
   type", contents matches live property).
   Closed issue ordermember-format (now takes segment instead of href).
   Renamed compliance class to "ordered-collections" for consistency
   with newer specs, and to allow detection of compliance to final
   version of spec.
   Updated reference to XML spec to 1.0, 2nd edition.





































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Index






   C


   Client-Maintained Ordering
      3



   D


   DAV:collection-must-be-ordered precondition
      6.1
   DAV:custom ordering type
      4.1.1
   DAV:ordered-collections-supported precondition
      5.1
   DAV:ordering-modified postcondition
      7
   DAV:ordering-type property
      4.1.1
   DAV:ordering-type-set postcondition
      5.1, 7
   DAV:position-set postcondition
      6.1
   DAV:segment-must-identify-member precondition
      6.1
   DAV:unordered ordering type
      4.1.1



   H


   Headers
      Ordering-Type   5.1







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   O


   Ordered Collection
      3
   Ordering-Type header
      5.1
   ORDERPATCH method
      7



   P


   Postconditions
      DAV:ordering-type-set   5.1, 7
      DAV:position-set   6.1
      DAV:ordering-type-set   5.1, 7
      DAV:ordering-modified   7

   Preconditions
      DAV:ordered-collections-supported   5.1
      DAV:collection-must-be-ordered   6.1
      DAV:segment-must-identify-member   6.1

   Protected properties
      DAV:ordering-type   4.1.1




   S


   Server-Maintained Ordering
      3



   U


   Unordered Collection
      3






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   Full Copyright Statement

      Copyright (C) The Internet Society (2003). All Rights Reserved.

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

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

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


   Acknowledgement

      Funding for the RFC editor function is currently provided by the
      Internet Society.


















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