Network Working Group J. Slein
Internet Draft Xerox
Expires: March 2003 J. Whitehead
U.C. Santa Cruz
J. Davis
Intelligent Markets
C. Fay
FileNet
J. Crawford
IBM
J. F. Reschke
greenbytes
September 2002
WebDAV Ordered Collections Protocol
draft-ietf-webdav-ordering-protocol-03
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
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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 March 2003.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
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Internet Draft WebDAV Ordered Collections Protocol September 2002
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
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . 3
1 Notational Conventions . . . . . . . . . . . . . . . . . . . . 5
2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4 Overview of Ordered Collections . . . . . . . . . . . . . . . . 8
4.1 Additional Collection properties . . . . . . . . . . . . . 8
4.1.1 DAV:orderingtype (protected) . . . . . . . . . . . . . 9
5 Creating an Ordered Collection . . . . . . . . . . . . . . . . 10
5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.2 Example: Creating an Ordered Collection . . . . . . . . . . 11
6 Setting the Position of a Collection Member . . . . . . . . . . 12
6.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.2 Status Codes . . . . . . . . . . . . . . . . . . . . . . . 12
6.3 Examples: Setting the Position of a Collection Member . . . 12
7 Changing a Collection Ordering . . . . . . . . . . . . . . . . 14
7.1 ORDERPATCH Method . . . . . . . . . . . . . . . . . . . . . 14
7.1.1 Status Codes . . . . . . . . . . . . . . . . . . . . . 14
7.1.2 Example: Changing a Collection Ordering . . . . . . . . 15
7.1.3 Example: Failure of an ORDERPATCH Request . . . . . . . 17
8 Listing the Members of an Ordered Collection . . . . . . . . . 19
8.1 Example: PROPFIND on an Ordered Collection . . . . . . . . 19
9 Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
9.1 Position Request Header . . . . . . . . . . . . . . . . . . 23
10 XML Elements . . . . . . . . . . . . . . . . . . . . . . . . . 24
10.1 order XML Element . . . . . . . . . . . . . . . . . . . . 24
10.2 ordermember XML Element . . . . . . . . . . . . . . . . . 24
10.3 position XML Element . . . . . . . . . . . . . . . . . . . 25
10.4 first XML Element . . . . . . . . . . . . . . . . . . . . 25
10.5 last XML Element . . . . . . . . . . . . . . . . . . . . . 25
10.6 before XML Element . . . . . . . . . . . . . . . . . . . . 26
10.7 after XML Element . . . . . . . . . . . . . . . . . . . . 26
10.8 segment XML Element . . . . . . . . . . . . . . . . . . . 27
11 Capability Discovery . . . . . . . . . . . . . . . . . . . . . 28
11.1 Example: Using OPTIONS for the Discovery of Support for
Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
11.2 Example: Using Live Properties for the Discovery of
Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
12 Security Considerations . . . . . . . . . . . . . . . . . . . 31
12.1 Denial of Service and DAV:orderingtype . . . . . . . . . . 31
13 Internationalization Considerations . . . . . . . . . . . . . 32
14 IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33
15 Copyright . . . . . . . . . . . . . . . . . . . . . . . . . . 34
16 Intellectual Property . . . . . . . . . . . . . . . . . . . . 35
17 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 36
Normative References . . . . . . . . . . . . . . . . . . . . . . 37
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Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
A Extensions to the WebDAV Document Type Definition . . . . . . . 39
B Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 40
B.1 Since draft-ietf-webdav-ordering-protocol dated December
1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
B.2 Since draft-ietf-webdav-ordering-protocol-02 . . . . . . . 40
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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 through Section 10 define the headers, properties, and XML
elements needed to support ordered collections. Section 11 describes
capability discovery. Section 12 through Section 14 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 the [RFC2518]. 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. It
is up to the client to decide whether a given collection is ordered
and, if so, to specify the semantics to be used for ordering its
members.
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 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
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4.1.1 DAV:orderingtype (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 Ordered header with a MKCOL request or by submitting an
ORDERPATCH request.
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.
The value DAV:custom indicates that the collection is ordered, but
the semantics governing the ordering are not being advertised.
If the value is a DAV:href element, it contains a URI that uniquely
identifies the semantics of the collection's ordering.
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:orderingtype
property, the collection is unordered.
<!ELEMENT orderingtype (unordered | custom | href) >
<!ELEMENT custom EMPTY >
<!ELEMENT unordered EMPTY >
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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
Ordered 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 Ordered 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 Ordered 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
header indicates that the client wants the collection to be
unordered. If the Ordered header is not present, the collection will
be unordered.
Additional Marshalling:
Ordered = "Ordered" ":" ("DAV:unordered" | "DAV:custom" | Coded-url)
A value of "DAV:unordered" indicates that the collection is not
ordered. A value of "DAV:custom" indicates that the collection is
to be ordered, but the semantics of the ordering is not being
advertised. Any other Coded-url 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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5.2 Example: Creating an Ordered Collection
>> Request:
MKCOL /theNorth/ HTTP/1.1
Host: www.server.org
Ordered: <http://www.server.org/orderings/compass.html>
>> Response:
HTTP/1.1 201 Created
In this example a new, ordered collection was created. Its
DAV:orderingtype property has as its value the URI from the Ordered
header, http://www.server.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 (defined in Section
9.1). 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.
6.2 Status Codes
409 (Conflict): Several conditions may cause this response. The
request may specify a position that is before or after a URI that is
not an internal member URI of the collection, or before or after
itself. The request may attempt to specify the new member's position
in an unordered collection.
6.3 Examples: Setting the Position of a Collection Member
>> Request:
COPY /~whitehead/dav/spec08.html HTTP/1.1
Host: www.ics.uci.edu
Destination: http://www.xerox.com/~slein/dav/spec08.html
Position: after requirements.html
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>> Response:
HTTP/1.1 201 Created
This request resulted in the creation of a new resource at
www.xerox.com/~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-protocol-08.txt HTTP/1.1
Host: www.ics.uci.edu
Destination: http://www.ics.uci.edu/~whitehead/dav/draft-webdav-
protocol-08.txt
Position: first
>> Response:
HTTP/1.1 409 Conflict
In this case, the server returned a 409 (Conflict) status code
because the /~whitehead/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
7.1 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 ORDERPATCH method changes the ordering semantics of the
collection identified by the Request-URI, based on the value of
DAV:orderingtype submitted in the request entity body.
The ORDERPATCH method alters the ordering of internal member URIs in
the collection identified by the Request-URI, based on instructions
in the ordermember XML elements in the request entity body. 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.
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.
7.1.1 Status Codes
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, as defined in [RFC2518].
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The following are examples of response codes one would expect to be
used in a 207 (Multi-Status) response for this method:
200 (OK): The change in ordering was successfully made.
409 (Conflict): Several conditions may cause this response. The
request may specify a position that is before or after a URI that is
not an internal member URI of the collection, or before or after
itself. The request may attempt to set the positions of members of an
unordered collection.
A request to reposition a collection member at the same place in the
ordering is not an error.
7.1.2 Example: Changing a Collection Ordering
Consider a collection /coll-1/ whose DAV:orderingtype is DAV:whim,
with bindings ordered as follows:
three.html
four.html
one.html
two.html
>> Request:
ORDERPATCH /coll-1/ HTTP/1.1
Host: www.myserver.com
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" ?>
<d:order xmlns:d="DAV:">
<d:orderingtype>
<d:href>http://www.myserver.com/inorder.ord</d:href>
</d:orderingtype>
<d:ordermember>
<d:href>two.html</d:href>
<d:position>
<d:first/>
</d:position>
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</d:ordermember>
<d:ordermember>
<d:href>one.html</d:href>
<d:position>
<d:first/>
</d:position>
</d:ordermember>
<d:ordermember>
<d:href>three.html</d:href>
<d:position>
<d:last/>
</d:position>
</d:ordermember>
<d:ordermember>
<d:href>four.html</d:href>
<d:position>
<d:last/>
</d:position>
</d:ordermember>
</d:order>
>> 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://www.myserver.com/inorder.ord. The value of the collection's
DAV:orderingtype 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:
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one.html
two.html
three.html
four.html
7.1.3 Example: Failure of an ORDERPATCH Request
Consider a collection /coll-1/ with members ordered as follows:
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:order xmlns:d="DAV:">
<d:ordermember>
<d:href>nunavut.desc</d:href>
<d:position>
<d:after>
<d:segment>nunavut.map</d:segment>
</d:after>
</d:position>
</d:ordermember>
<d:ordermember>
<d:href>iqaluit.map</d:href>
<d:position>
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<d:after>
<d:segment>pangnirtung.img</d:segment>
</d:after>
</d:position>
</d:ordermember>
</d:order>
>> Response:
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" ?>
<d:multistatus xmlns:d="DAV:">
<d:response>
<d:href>http://www.nunanet.com/coll-1/nunavut.desc</d:href>
<d:status>HTTP/1.1 424 Failed Dependency</d:status>
</d:response>
<d:response>
<d:href>http://www.nunanet.com/coll-1/iqaluit.map</d:href>
<d:status>HTTP/1.1 409 Conflict</d:status>
<d:responsedescription>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 409 (Conflict) status
code. Because ORDERPATCH is an atomic method, the request to
reposition nunavut.desc (which would otherwise have succeeded) failed
with a 424 (Failed Dependency) status code.
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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 /MyCollection/, which has
its members ordered as follows.
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/MyCollection/
lakehazen.html
siorapaluk.html
iqaluit.html
newyork.html
>> Request:
PROPFIND /MyCollection/ HTTP/1.1
Host: www.svr.com
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://www.svr.com/jsprops/">
<D:orderingtype/>
<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:www.svr.com/jsprops/">
<D:response>
<D:href>http://www.svr.com/MyCollection/</D:href>
<D:propstat>
<D:prop>
<D:orderingtype><D:custom/></D:orderingtype>
<D:resourcetype><D:collection/></D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
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<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://www.svr.com/MyCollection/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:orderingtype/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href
>http://www.svr.com/MyCollection/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:orderingtype/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://www.svr.com/MyCollection/iqaluit.html</D:href>
<D:propstat>
<D:prop>
<D:resourcetype/>
<J:latitude>62N</J:latitude>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
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<D:propstat>
<D:prop>
<D:orderingtype/>
</D:prop>
<D:status>HTTP/1.1 404 Not Found</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://www.svr.com/MyCollection/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:orderingtype/>
</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 Headers
9.1 Position Request Header
Position = "Position" ":" ("first" | "last" |
(("before" | "after") segment))
segment is defined in Section 3.3 of [RFC2396].
The Position header may be used with any method that adds a member to
an ordered collection, to tell the server where in the collection
ordering to position the new member being added to the collection.
Examples of methods that add members to collections are BIND, PUT,
COPY, MOVE, etc.
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 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.
If an attempt is made to use the Position header on a collection that
is unordered, the server MUST fail the request with a 409 (Conflict)
status code.
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10 XML Elements
10.1 order XML Element
Name: order
Namespace: DAV:
Purpose: For use with the new ORDERPATCH method. Describes a change
to be made in a collection's ordering semantics or in the
positions of its members in the ordering or both.
Value: An optional identifier of an ordering semantics for the
collection, followed by a list of changes to be made in
the positions of the members in the collection's ordering.
<!ELEMENT order (orderingtype?, ordermember*) >
10.2 ordermember XML Element
Name: ordermember
Namespace: DAV:
Purpose: Occurs in the order XML element, and describes the new
position of a single internal member URI in the
collection's ordering.
Value: An href containing a member's path segment, and a
description of its new position in the ordering. The href
XML element is defined in [RFC2518], Section 11.3.
<!ELEMENT ordermember (href, position) >
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10.3 position XML Element
Name: position
Namespace: DAV:
Purpose: Occurs in the ordermember XML element. Describes the new
position in a collection's ordering of one of the members
it contains.
Value: The new position can be described as first in the
collection's ordering, last in the collection's ordering,
immediately before some other collection member, or
immediately after some other collection member.
<!ELEMENT position (first | last | before | after)>
10.4 first XML Element
Name: first
Namespace: DAV:
Purpose: Occurs in the position XML element. Specifies that the
member should be placed first in the collection's
ordering.
<!ELEMENT first EMPTY >
10.5 last XML Element
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Name: last
Namespace: DAV:
Purpose: Occurs in the position XML element. Specifies that the
member should be placed last in the collection's ordering.
<!ELEMENT last EMPTY >
10.6 before XML Element
Name: before
Namespace: DAV:
Purpose: Occurs in the position XML element. Specifies that the
member should be placed immediately before the member in
the enclosed segment XML element in the collection's
ordering.
Value: URI (relative to the parent collection) of the member it
precedes in the ordering
<!ELEMENT before segment >
10.7 after XML Element
Name: after
Namespace: DAV:
Purpose: Occurs in the position XML element. Specifies that the
member should be placed immediately after the member in
the enclosed segment XML element in the collection's
ordering.
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Value: URI (relative to the parent collection) of the member it
follows in the ordering
<!ELEMENT after segment >
10.8 segment XML Element
Name: segment
Namespace: DAV:
Purpose: Identifies a member of a collection, used in the
DAV:before and DAV:after elements, to define one member's
position in a collection ordering relative to another
member of the collection.
Value: segment ; as defined in section 3.3 of [RFC2396].
<!ELEMENT segment (#PCDATA)>
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11 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 orderedcoll, 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 orderedcoll
compliance class in the DAV header.
When responding to an OPTIONS request, only a collection or a null
resource can include orderedcoll in the value of the DAV header. By
including orderedcoll, 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.
11.1 Example: Using OPTIONS for the Discovery of Support for Ordering
>> Request:
OPTIONS /somecollection/ HTTP/1.1
HOST: somehost.org
>> Response:
HTTP/1.1 200 OK
Date: Tue, 20 Jan 1998 20:52:29 GMT
Connection: close
Accept-Ranges: none
Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE,
MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, ORDERPATCH
DAV: 1, 2, orderedcoll
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The DAV header in the response indicates that the resource
/somecollection/ is level 1 and level 2 compliant, as defined in
[RFC2518]. In addition, /somecollection/ supports ordering. The Allow
header indicates that ORDERPATCH requests can be submitted to
/somecollection/.
11.2 Example: Using Live Properties for the Discovery of Ordering
>> Request:
PROPFIND /somecollection HTTP/1.1
Host: somehost.org
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://somehost.org/somecollection</href>
<propstat>
<prop>
<supported-live-property-set>
<supported-live-property>
<prop><orderingtype/></prop>
</supported-live-property>
... other live properties omitted for brevity ...
</supported-live-property-set>
<supported-method-set>
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<supported-method name="COPY" />
<supported-method name="DELETE" />
<supported-method name="GET" />
<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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12 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.
12.1 Denial of Service and DAV:orderingtype
There may be some risk of denial of service at sites that are
advertised in the DAV:orderingtype 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:orderingtype. 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:orderingtype.
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13 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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14 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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15 Copyright
To be supplied by the RFC Editor.
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16 Intellectual Property
To be supplied by the RFC Editor.
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17 Acknowledgements
This draft has benefited from thoughtful discussion by Jim Amsden,
Steve Carter, Tyson Chihaya, Geoff Clemm, Ken Coar, Ellis Cohen,
Bruce Cragun, Spencer Dawkins, Mark Day, Rajiv Dulepet, David Durand,
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] World Wide Web Consortium, "Extensible Markup Language
(XML) 1.0", W3C XML, February 1998.
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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Jim Davis
Intelligent Markets
410 Jessie Street 6th floor
San Francisco, CA 94103
EMail: jrd3@alum.mit.edu
Chuck Fay
FileNet Corporation
3565 Harbor Boulevard
Costa Mesa, CA 92626-1420
EMail: cfay@filenet.com
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
<!--============= XML Elements from Section 11 ================-->
<!ELEMENT unordered EMPTY >
<!ELEMENT custom EMPTY >
<!ELEMENT order (orderingtype?, ordermember*) >
<!ELEMENT ordermember (href, position) >
<!ELEMENT position (first | last | before | after)>
<!ELEMENT first EMPTY >
<!ELEMENT last EMPTY >
<!ELEMENT before segment >
<!ELEMENT after segment >
<!ELEMENT segment (#PCDATA)>
<!--============= Property Elements from Section 10 =============-->
<!ELEMENT orderingtype (unordered | custom | href) >
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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.
Full Copyright Statement
Copyright (C) The Internet Society (2002). 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.
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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.
Slein, et al. Expires March 2003 [Page 41]
