Network Working Group J. Slein
Internet Draft Xerox
Expires: July 2003 J. Whitehead
U.C. Santa Cruz
J. Crawford
IBM
J. F. Reschke
greenbytes
January 2003
WebDAV Ordered Collections Protocol
draft-ietf-webdav-ordering-protocol-04
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,
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This Internet-Draft will expire in July 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:orderingtype (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 . . . . . . . 18
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:orderingtype . . . . . . . . 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
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
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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: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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Additional Postconditions:
(DAV:orderdingtype-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
Ordered: <http://example.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://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
collection's ordering. The "before" keyword indicates the new
member is added to the collection's ordering immediately prior to
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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:order element.
<!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)>
PCDATA value: segment, as defined in section 3.3 of [RFC2396].
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DAV:href value: segment part of collection member.
The DAV:orderingtype property is modified according to the
DAV:orderingtype 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:orderingtype could not be modified) or URIs of collection
members to be repositioned (when an invidual 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:orderdingtype-set): if the request body contained a
DAV:orderingtype element, the DAV:orderingtype 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: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: example.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" ?>
<d:order xmlns:d="DAV:">
<d:orderingtype>
<d:href>http://example.org/inorder.ord</d:href>
</d:orderingtype>
<d:ordermember>
<d:href>two.html</d:href>
<d:position>
<d:first/>
</d:position>
</d:ordermember>
<d:ordermember>
<d:href>one.html</d:href>
<d:position>
<d:first/>
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</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://example.org/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:
one.html
two.html
three.html
four.html
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7.2 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>
<d:after>
<d:segment>pangnirtung.img</d:segment>
</d:after>
</d:position>
</d:ordermember>
</d:order>
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>> 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/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: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://example.org/jsprops/">
<D:response>
<D:href>http://example.org/MyColl/</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://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:orderingtype/>
</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:orderingtype/>
</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>
<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://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: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 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:orderingtype
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:orderingtype 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 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.
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, orderedcoll
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
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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><orderingtype/></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" />
<supported-method name="HEAD" />
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<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: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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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] 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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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.
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 ODERPATCH multistatus (it's atomic
anyway).
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Index
C O
Client-Maintained Ordering Ordered Collection
3 3
Ordered header
5.1
ORDERPATCH method
D 7
DAV:collection-must-be-ordered
precondition P
6.1
DAV:custom ordering type
4.1.1 Postconditions
DAV:ordered-collections- DAV:orderingtype-set 5.1,7
supported precondition DAV:position-set 6.1
5.1 DAV:orderingtype-set 5.1,7
DAV:ordering-modified DAV:ordering-modified 7
postcondition
7 Preconditions
DAV:orderingtype property DAV:ordered-collections-
4.1.1 supported 5.1
DAV:orderingtype-set DAV:collection-must-be-
postcondition ordered 6.1
5.1,7 DAV:segment-must-identify-
DAV:position-set postcondition member 6.1
6.1
DAV:segment-must-identify- Protected properties
member precondition DAV:orderingtype 4.1.1
6.1
DAV:unordered ordering type
4.1.1
S
H
Server-Maintained Ordering
3
Headers
Ordered 5.1
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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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