Network Working Group J. Gregorio, Ed.
Internet-Draft BitWorking, Inc
Expires: November 10, 2005 R. Sayre, Ed.
May 9, 2005
The Atom Publishing Protocol
draft-ietf-atompub-protocol-04.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This memo presents a protocol for using XML (Extensible Markup
Language) and HTTP (HyperText Transport Protocol) to edit content.
The Atom Publishing Protocol is an application-level protocol for
publishing and editing Web resources belonging to periodically
updated websites. The protocol at its core is the HTTP transport of
Atom-formatted representations. The Atom format is documented in the
Atom Syndication Format (draft-ietf-atompub-format-06.txt).
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Editorial Note
To provide feedback on this Internet-Draft, join the atom-protocol
mailing list (http://www.imc.org/atom-protocol/index.html) [1].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. The Atom Publishing Protocol Model . . . . . . . . . . . . . . 6
4.1 Collections . . . . . . . . . . . . . . . . . . . . . . . 6
4.2 Discovery . . . . . . . . . . . . . . . . . . . . . . . . 6
4.3 Listing . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.4 Authoring . . . . . . . . . . . . . . . . . . . . . . . . 7
4.4.1 Create . . . . . . . . . . . . . . . . . . . . . . . . 7
4.4.2 Read . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.4.3 Update . . . . . . . . . . . . . . . . . . . . . . . . 8
4.4.4 Delete . . . . . . . . . . . . . . . . . . . . . . . . 8
4.5 Success and Failure . . . . . . . . . . . . . . . . . . . 9
5. Collections . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 Collection Documents . . . . . . . . . . . . . . . . . . . 10
5.1.1 Element Definitions . . . . . . . . . . . . . . . . . 10
5.2 Collection Resource . . . . . . . . . . . . . . . . . . . 12
5.2.2 POST . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.2.3 Usage Scenarios . . . . . . . . . . . . . . . . . . . 15
5.2.4 Range: Header . . . . . . . . . . . . . . . . . . . . 16
5.2.5 Accept-Ranges: Header . . . . . . . . . . . . . . . . 16
5.2.6 Name: Header . . . . . . . . . . . . . . . . . . . . . 17
6. Entry Collection . . . . . . . . . . . . . . . . . . . . . . . 18
6.1 Editing Entry Resources . . . . . . . . . . . . . . . . . 18
6.2 Role of Atom Entry Elements During Editing . . . . . . . . 18
7. Generic Collection . . . . . . . . . . . . . . . . . . . . . . 20
7.1 Editing Generic Resources . . . . . . . . . . . . . . . . 20
8. Introspection . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1 Introspection Document . . . . . . . . . . . . . . . . . . 21
8.1.1 Element Definitions . . . . . . . . . . . . . . . . . 21
8.2 Introspection Resource . . . . . . . . . . . . . . . . . . 23
8.2.1 Discovery . . . . . . . . . . . . . . . . . . . . . . 24
9. Securing the Atom Protocol . . . . . . . . . . . . . . . . . . 25
10. Security Considerations . . . . . . . . . . . . . . . . . . 26
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . 27
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
12.1 Normative References . . . . . . . . . . . . . . . . . . . 30
12.2 Informative References . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 32
A. Revision History . . . . . . . . . . . . . . . . . . . . . . . 33
Intellectual Property and Copyright Statements . . . . . . . . 35
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1. Introduction
The Atom Publishing Protocol is an application-level protocol for
publishing and editing Web resources using HTTP [RFC2616] and XML 1.0
[W3C.REC-xml-20040204].
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2. Notational Conventions
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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3. Terminology
URI/IRI - A Uniform Resource Identifier and Internationalized
Resource Identifier, respectively. These terms (and the distinction
between them) are defined in [RFC3986] and [RFC3987].
Resource - an item identified by a URI [W3C.REC-webarch-20041215].
Collection Resource - A resource that contains a listing of Member
Resources and meets the requirements in Section 5 of this
specification.
Member Resource - A resource whose URI is listed by a Collection
Resource.
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4. The Atom Publishing Protocol Model
The Atom Publishing Protocol operates on collections of Web
resources. All collections support the same basic interactions, as
do the resources within the collections. The patterns of interaction
are based on the common HTTP verbs.
o GET is used to retrieve a representation of a resource or perform
a read-only query.
o POST is used to create a new, dynamically-named resource.
o PUT is used to update a known resource.
o DELETE is used to remove a resource.
4.1 Collections
The APP groups resources into "Collections", which are analogous to
the "folders" or "directories" found in many file systems.
4.2 Discovery
To discover the location of the collections exposed by an APP
service, the client must locate and request an Introspection Document
(Section 8).
Client Server
| |
| 1.) GET Introspection |
|------------------------------->|
| |
| 2.) Introspection Doc |
|<-------------------------------|
| |
1. The client sends a GET request to the Service Description
Resource.
2. The server responds with an Introspection Document containing the
locations of collections provided by the service. The content of
this document can vary based on aspects of the client request,
including, but not limited to, authentication credentials.
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4.3 Listing
Once the client has discovered the location of a collection, it can
request a listing of the collection's membership. However,
collections might be extremely large, so servers are likely to list a
small subset of the collection by default.
Client Server
| |
| 1.) GET to Collection URI |
|------------------------------->|
| |
| 2.) 200 OK, Atom Feed Doc |
|<-------------------------------|
| |
1. The client sends a GET request to the Collection's URI.
2. The server responds with an Atom Feed Document containing a full
or partial listing of the collection's membership.
4.4 Authoring
After locating a collection, a client can add entries by sending a
request to the collection; other changes are accomplished by sending
HTTP requests to its member resources.
4.4.1 Create
Client Server
| |
| 1.) POST to Collection URI |
|------------------------------->|
| |
| 2.) 201 Created @ Location |
|<-------------------------------|
| |
1. The client sends a representation of a member to the server via
HTTP POST. The Request URI is that of the Collection.
2. The server responds with a response of "201 Created" and a
"Location" header containing the URI of the newly-created
resource.
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4.4.2 Read
Client Server
| |
| 1.) GET or HEAD to Member URI |
|------------------------------->|
| |
| 2.) 200 OK |
|<-------------------------------|
| |
1. The client sends a GET (or HEAD) request to the member's URI.
2. The server responds with an appropriate representation.
4.4.3 Update
Client Server
| |
| 1.) PUT to Member URI |
|------------------------------->|
| |
| 2.) 200 OK |
|<-------------------------------|
1. The client PUTs an updated representation to the member's URI.
2. The server responds with a representation of the member's new
state.
4.4.4 Delete
Client Server
| |
| 1.) DELETE to Member URI |
|------------------------------->|
| |
| 2.) 204 No Content |
|<-------------------------------|
| |
1. The client sends a DELETE request to the member's URI.
2. The server responds with successful status code.
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4.5 Success and Failure
HTTP defines classes of response. HTTP status codes of the form 2xx
signal that a request was successful. HTTP status codes of the form
4xx or 5xx signal that an error has occurred, and the request has
failed. Consult the HTTP specification for more detailed definitions
of each status code.
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5. Collections
An Atom Collection is a set of related resources. All members of a
collection have an "updated" property, and the collection is
considered to be ordered by this property.
5.1 Collection Documents
An example Collection Document.
<?xml version="1.0" encoding='utf-8'?>
<collection xmlns="http://purl.org/atom/app#">
<member href="http://example.org/1"
hrefreadonly="http://example.com/1/bar"
title="Sample 1"
updated="2003-12-13T18:30:02Z" />
<member href="http://example.org/2"
hrefreadonly="http://example.com/2/bar"
title="Sample 2"
updated="2003-12-13T18:30:02Z" />
<member href="http://example.org/3"
hrefreadonly="http://example.com/3/bar"
title="Sample 3"
updated="2003-12-13T18:30:02Z" />
<member href="http://example.org/4"
title="Sample 4"
updated="2003-12-13T18:30:02Z" />
</collection>
Atom Collection Documents have the media-type 'application/
atomcoll+xml', see Section 11.
5.1.1 Element Definitions
5.1.1.1 The 'app:collection' Element
The 'app:collection' element represents an Atom Collection. A
collection document does not necessarily list every member of the
collection.
appCollection element app:collection {
attribute next { text } ?,
appMember*
}
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o 'app:collection' elements MAY contain any number of 'app:member'
elements.
o 'app:collection' elements MAY contain a 'next' attribute which
identifies a collection document containing member elements
updated earlier in time.
The members listed in a collection document MUST constitute a
consecutive sequence of the collection's members, ordered by their
"updated" properties. That is, a collection document MUST contain a
contiguous subset of the members of the collection ordered by their
'updated' property.
5.1.1.2 The 'app:member' Element
The 'app:member' represents a single member resource.
appMember element app:member {
attribute title { text },
attribute href { text },
attribute hrefreadonly { text } ?,
attribute updated { text }
}
o 'app:member' elements MUST include an 'href' attribute, whose
value conveys the URI used to edit the member source
o 'app:member' elements MAY include an "hrefreadonly
(Section 5.1.1.3)" attribute.
o 'app:member' elements MUST include a 'title' attribute, whose
value is a human-readable name or description for the item.
o 'app:member' elements MUST include an 'updated' attribute, whose
value is the 'updated' property of the collection member. Its
format MUST conform to the date-time production in [RFC3339].
5.1.1.3 The 'hrefreadonly' Attribute
This optional attribute identifies a URI which, on a GET request,
responds equivalently to how the "href" URI would respond to the same
request. Clients SHOULD NOT apply to this URI any HTTP methods that
would be expected to modify the state of the resource (e.g. PUT,
POST or DELETE). A PUT or POST request to this URI MAY NOT affect
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the underlying resource. If the "hrefreadonly" attribute is not
given, its value defaults to the "href" value. If the "hrefreadonly"
attribute is present, and its value is an empty string, then there is
no URI that can be treated in the way such a value would be treated.
Clients SHOULD use the "href" value to manipulate the resource within
the context of the APP itself. Clients SHOULD prefer the
"hrefreadonly" value in any other context. For example, if the
resource is an image, a client may replace the image data using a PUT
on the "href" value, and may even display a preview of the image by
fetching the "href" URI. But when creating a public, read-only
reference to the same image resource, the client should use the
"hrefreadonly" value. If the "hrefreadonly" value is an empty
string, the client SHOULD NOT make public reference to the "href"
value.
[[anchor10: Define extensibility for Collection Documents.]]
5.2 Collection Resource
This specification defines two HTTP methods for use with collection
resources: GET and POST.
5.2.1 GET
Collections can contain extremely large numbers of resources. A
naive client such as a web spider or web browser would be overwhelmed
if the response to a GET reflected the full membership of the
collection, and the server would waste large amounts of bandwidth and
processing time on clients unable to handle the response. As a
result, responses to a simple GET request represent a server-
determined subset of the collection's membership.
In addition, the client MAY send a 'Range' header with a range type
of 'udpated', indicating the subset of the collection to be returned.
The 'Range' header is described in Section 5.2.4.
This specification defines two serializations for Atom Collections.
Servers MUST provide both, but MAY also provide additional
serializations.
1. Atom Collection Documents (application/atomcoll+xml),
Section 5.1.
2. Atom Collection Documents wrapped by a SOAP envelope
(application/soap+xml), .
Clients use the HTTP 'Accept' request header to indicate their
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preference.
Example Request, with Accept header
GET /collection HTTP/1.1
Host: example.org
User-Agent: Agent/1.0
Accept: application/atomcoll+xml
Here, the server could return any subset of the collection as an Atom
Collection Document.
Example Response, Atom Collection Document
HTTP/1.1 200 OK
Date: Fri, 25 Mar 2005 17:15:33 GMT
Last-Modified: Mon, 04 Oct 2004 18:31:45 GMT
ETag: "2b3f6-a4-5b572640"
Accept-Ranges: updated
Content-Length: nnnn
Content-Type: application/atomcoll+xml; charset="utf-8"
<?xml version="1.0" encoding="utf-8"?>
<collection xmlns="http://purl.org/atom/app#">
...
<member href="http://example.org/1"
hrefreadonly="http://example.com/1/bar"
title="Example 1"
updated="2003-12-13T18:30:02Z" />
...
</collection>
Example Request, with SOAP Accept header
GET /collection HTTP/1.1
Host: example.org
User-Agent: Cosimo/1.0
Accept: application/soap+xml
Here, the server could return any subset of the collection as an Atom
Feed Document wrapped by a SOAP envelope.
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Example Response, Atom Feed Document wrapped by a SOAP envelope
HTTP/1.1 200 OK
Date: Fri, 25 Mar 2005 17:15:33 GMT
Last-Modified: Mon, 04 Oct 2004 18:31:45 GMT
ETag: "2b3f6-a4-5b572640-89"
Accept-Ranges: bytes
Content-Length: nnnn
Content-Type: application/soap+xml; charset="utf-8"
<?xml version="1.0" encoding="utf-8"?>
<env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope">
<env:Header />
<env:Body>
<collection xmlns="http://purl.org/atom/app#">
...
<member href="http://example.org/1"
hrefreadonly="http://example.com/1/bar"
title="Example 1"
updated="2003-12-13T18:30:02Z" />
...
</collection>
</env:Body>
</env:Envelope>
5.2.2 POST
In addition to GET, a Collection Resource also accepts POST requests.
The client POSTs a representation of the desired resource to the
Collection Resource. Note that some collections only allow members
of a specific media-type and a POST MAY generate a response with a
status code of 415 ("Unsupported Media Type").
In the case of a successful creation, the status code MUST be 201
("Created").
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Example Request, Create a resource in a collection.
POST /collection HTTP/1.1
Host: example.org
User-Agent: Cosimo/1.0
Accept: application/atomcoll+xml
Content-Type: image/png
Content-Length: nnnn
Name: trip-to-beach.png
...binary data...
Here, the client is adding a new image resource to a collection. The
Name: header indicates the client's desired name for the resource,
see Section 5.2.6.
Example Response, resource created successfully.
HTTP/1.1 201 Created
Date: Fri, 25 Mar 2005 17:17:11 GMT
Content-Length: nnnn
Content-Type: application/atomcoll+xml; charset="utf-8"
Location: http://example.org/images/trip-to-the-beach-01.png
<?xml version="1.0" encoding="UTF-8"?>
<collection xmlns="http://purl.org/atom/app#">
<member href="http://example.org/images/trip-to-beach.png"
hrefreadonly="http://example.com/ed/im/trip-01.png"
title="trip-to-beach.png"
updated="2005-03-25T17:17:09Z" />
</collection>
5.2.3 Usage Scenarios
These scenarios illustrate common idioms for interactin with
Collections.
The Atom Collection can be used by clients in two ways. In the first
case the client encounters a Collection for the first time and is
doing an initial syncronization, that is, retrieving a list of all
the members of the collections and possibly retrieving all the
members of the collection also. The client can perform a non-partial
GET on the collection resource and it will receive a collection
document that either contains all the members of the collection, or
the collection document root element 'collection' will contain a
'next' attribute pointing to the next collection document. By
repeatedly following the 'next' attribute from document to document
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the client can find all the members of the collection.
In the second case the client has already done an initial sync, and
now needs to re-sync, because the client was just restarted, or some
time has passed since a re-sync, etc. The client does a partial GET
on the collection document, supplying a Range header that begins from
the last time the client sync'd to the current time. The collection
document returned will contain only those members of the collection
that have changed since the last time the client syncronized.
5.2.4 Range: Header
HTTP/1.1 allows a client to request that only part (a range of) the
collection to be included within the response. HTTP/1.1 uses range
units in the Range header field. A collection can be broken down
into subranges according to the members 'updated' property. If a
Range: header is present in the request, its value explictly
identifies the a time interval interval in which all the members
'updated' property must fall to be included in the response.
Range = "Range" ":" ranges-specifier
The value of the Range: header should be a pair of ISO 8601 dates,
separated by a slash character; either date may be optionally
omitted, in which case the range is understood as stretching to
infinity on that end.
ranges-specifier = updated-ranges-specifier
updated-ranges-specifier = updated-unit "=" updated-range
updated-unit = "updated"
updated-range = [iso-date] "/" [iso-date]
The response to a collection request MUST be a collection document,
all of whose 'member' elements fall within the requested range. The
request range is considered a closed set, that is, if a 'member'
element matches one end of the range exactly it MUST be included in
the response. If no members fall in the requested range, the server
MUST respond with a collection document containing no 'member'
elements.
The inclusion of the Range: header in a request changes the request
to a "partial GET" [RFC2616].
5.2.5 Accept-Ranges: Header
The response to a non-partial GET request MUST include an Accept-
Ranges header that indicates that the server accepts 'updated' range
requests.
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Accept-Ranges = "Accept-Ranges" ":" acceptable-ranges
acceptable-ranges = updated-unit ( 1#range-unit )
5.2.6 Name: Header
[[anchor13: this is new...]]
The POST to a Collection Resource MAY contain a Name: header that
indicates the clients suggested name for the resource. The server
MAY ignore the Name: header or modify the requested name to suit
local conventions.
Name = "Name" ":" relative-part
The relative-part production is defined in [RFC3986].
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6. Entry Collection
Entry Collections are Collections that restrict their membership to
Atom entries. This specification defines two serializations for Atom
entries. Servers MUST provide both serializations.
1. Atom Entry Documents (application/atom+xml), [AtomFormat].
2. Atom Entry Documents wrapped by a SOAP envelope (application/
soap+xml), .
Clients use the HTTP 'Accept' request header to indicate their
preference [RFC2616]. If no 'Accept' header is present in the
request, the server is free to choose any serialization. When an
HTTP request contains a body, clients MUST include a 'Content-Type'
header, and servers MUST accept both application/atom+xml and
application/soap+xml message bodies.
6.1 Editing Entry Resources
Atom entries are edited by sending HTTP requests to an individual
entry's URI. Servers can determine the processing necessary to
interpret a request by examining the request's HTTP method and
'Content-Type' header.
If the request method is POST and the 'Content-Type' is application/
soap+xml, the SOAP document MUST contain a Web-Method property .
This specifcation defines two values for that property, PUT and
DELETE.
Processing Client Requests
+----------------------------------+------+--------+--------+--------+
| | GET | PUT | DELETE | POST |
+----------------------------------+------+--------+--------+--------+
| No Body | Read | x | Delete | x |
| | | | | |
| Atom Body | x | Update | x | x |
| | | | | |
| SOAP Body with Web-Method PUT | x | x | x | Update |
| | | | | |
| SOAP Body with Web-Method DELETE | x | x | x | Delete |
+----------------------------------+------+--------+--------+--------+
6.2 Role of Atom Entry Elements During Editing
The elements of an Atom Entry Document are either a 'Writable
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Element' or a 'Round Trip Element'.
Writable Element - An element of an Atom Entry whose value is
editable by the client and not enforced by the server.
Round Trip Element - An element of an Atom Entry whose value is
enforced by the server and not editable by the client.
That categorization will determine the elements' disposition during
editing.
+--------------------+------------+
| Atom Entry Element | Property |
+--------------------+------------+
| atom:author | Writable |
| | |
| atom:category | Writable |
| | |
| atom:content | Writable |
| | |
| atom:contributor | Writable |
| | |
| atom:id | Round Trip |
| | |
| atom:link | Writable |
| | |
| atom:published | Writable |
| | |
| atom:source | Writable |
| | |
| atom:summary | Writable |
| | |
| atom:title | Writable |
| | |
| atom:updated | Round Trip |
+--------------------+------------+
Table 2
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7. Generic Collection
Generic Collections are Collections that do not have uniform
restrictions on the representations of the member resources.
7.1 Editing Generic Resources
Member resources are edited by sending HTTP requests to an individual
resource's URI. Servers can determine the processing necessary to
interpret a request by examining the request's HTTP method and
'Content-Type' header.
Processing Client Requests
+----------+------+--------+--------+------+
| | GET | PUT | DELETE | POST |
+----------+------+--------+--------+------+
| No Body | Read | x | Delete | x |
| | | | | |
| Any Body | x | Update | x | x |
+----------+------+--------+--------+------+
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8. Introspection
In order for authoring to commence, a client must first discover the
capabilities and locations of collections offered.
8.1 Introspection Document
The Introspection Document describes "workspaces", which are server-
defined groupings of collections. There is no requirement that
servers support multiple workspaces, and a collection may appear in
more than one workspace.
The Introspection Document has the media-type 'application/
atomserv+xml', see Section 11
<?xml version="1.0" encoding='utf-8'?>
<service xmlns="http://purl.org/atom/app#">
<workspace title="Main Site" >
<collection contents="entries" title="My Blog Entries"
href="http://example.org/reilly/feed" />
<collection contents="generic" title="Documents"
href="http://example.org/reilly/pic" />
</workspace>
<workspace title="Side Bar Blog">
<collection contents="entries" title="Entries"
href="http://example.org/reilly/feed" />
<collection contents="http://example.net/booklist" title="Books"
href="http://example.org/reilly/books" />
</workspace>
</service>
8.1.1 Element Definitions
8.1.1.1 The 'app:service' Element
The "service" element is the document element of a Service Document,
acting as a container for service data associated with one or more
workspaces.
appService element app:service {
( appWorkspace*
& anyElement* )
}
The following child elements are defined by this specification:
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o app:service elements MAY contain any number of app:workspace
elements.
8.1.1.2 The 'app:workspace' Element
The 'workspace' element element contains information elements about
the collections of resources available for editing.
appWorkspace element app:workspace {
attribute title { text },
( appCollection*
& anyElement* )
}
The following attributes and child elements are defined by this
specification:
o app:workspace elements MUST contain a 'title' attribute, which
conveys a human-readable name for the workspace
o app:workspace elements MAY contain any number of app:collection
elements.
8.1.1.3 The 'app:collection' Element
The 'app:collection' element describes collections and their member
resources.
[[anchor19: We have a collection element that's different than the
root element of the collection document. Messy. --R. Sayre]]
appCollection element app:collection {
attribute title { text },
attribute contents { text },
attribute href { text },
anyElement*
}
The following attributes are defined by this specification:
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o app:collection elements MUST contain a 'title' attribute, whose
value conveys a human-readable name for the workspace
o app:collection elements MAY contain a 'contents' attribute
(Section 8.1.1.3.1). If it is not present, it's value is
considered to be 'generic'.
o app:collection elements MUST contain an 'href' attribute, whose
value conveys the URI of the collection.
8.1.1.3.1 The 'contents' Attribute
The 'contents' attribute conveys the nature of a collection's member
resources. This specification defines two initial values for the
'contents' attribute:
o entry
o generic
Extensibility for 'content' values is handled [[anchor20: Same as
atom:link]].
8.1.1.3.1.1 entry
A value of 'entry' for the contents attribute indicates that the
Collection is an Entry Collection (Section 6).
8.1.1.3.1.2 generic
A value of 'generic' for the contents attribute indicates that the
Collection is a Generic Collection (Section 7).
8.2 Introspection Resource
To retrieve an Introspection Document, the client sends a GET request
to its URI.
GET /service-desc HTTP/1.1
Host: example.org
User-Agent: Cosimo/1.0
Accept: application/atomserv+xml
The server responds to a GET request by returning an Introspection
Document in the message body.
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HTTP/1.1 200 OK
Date: Mon, 21 Mar 2005 19:20:19 GMT
Server: CountBasic/2.0
Last-Modified: Mon, 21 Mar 2005 19:17:26 GMT
ETag: "4c083-268-423f1dc6"
Content-Length: nnnn
Content-Type: application/atomserv+xml
<?xml version="1.0" encoding='utf-8'?>
<service xmlns="http://purl.org/atom/app#">
...
</service>
8.2.1 Discovery
[[anchor24: Add in desc of an HTML link element that points to the
Introspection Resource, or add it to the autodisco draft]]
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9. Securing the Atom Protocol
All instances of publishing Atom entries SHOULD be protected by
authentication to prevent posting or editing by unknown sources.
Atom servers and clients MUST support one of the following
authentication mechanisms, and SHOULD support both.
o HTTP Digest Authentication [RFC2617]
o [@@TBD@@ CGI Authentication ref]
Atom servers and clients MAY support encryption of the Atom session
using TLS [RFC2246].
There are cases where an authentication mechanism may not be
required, such as a publicly editable Wiki, or when using the PostURI
to post comments to a site that does not require authentication to
create comments.
9.1 [@@TBD@@ CGI Authentication]
This authentication method is included as part of the protocol to
allow Atom servers and clients that cannot use HTTP Digest
Authentication but where the user can both insert its own HTTP
headers and create a CGI program to authenticate entries to the
server. This scenario is common in environments where the user
cannot control what services the server employs, but the user can
write their own HTTP services.
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10. Security Considerations
Because Atom is a publishing protocol, it is important that only
authorized users can create and edit entries.
The security of Atom is based on HTTP Digest Authentication and/or
[@@TBD@@ CGI Authentication]. Any weaknesses in either of these
authentication schemes will obviously affect the security of the Atom
Publishing Protocol.
Both HTTP Digest Authentication and [@@TBD@@ CGI Authentication] are
susceptible to dictionary-based attacks on the shared secret. If the
shared secret is a password (instead of a random string with
sufficient entropy), an attacker can determine the secret by
exhaustively comparing the authenticating string with hashed results
of the public string and dictionary entries.
See RFC 2617 for more detailed description of the security properties
of HTTP Digest Authentication.
@@TBD@@ Talk here about using HTTP basic and digest authentication.
@@TBD@@ Talk here about denial of service attacks using large XML
files, or the billion laughs DTD attack.
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11. IANA Considerations
A Atom Collection Document, when serialized as XML 1.0, can be
identified with the following media type:
MIME media type name: application
MIME subtype name: atomcoll+xml
Mandatory parameters: None.
Optional parameters:
"charset": This parameter has identical semantics to the charset
parameter of the "application/xml" media type as specified in
[RFC3023].
Encoding considerations: Identical to those of "application/xml" as
described in [RFC3023], section 3.2.
Security considerations: As defined in this specification.
[[anchor28: update upon publication]]
In addition, as this media type uses the "+xml" convention, it
shares the same security considerations as described in [RFC3023],
section 10.
Interoperability considerations: There are no known interoperability
issues.
Published specification: This specification. [[anchor29: update upon
publication]]
Applications that use this media type: No known applications
currently use this media type.
Additional information:
Magic number(s): As specified for "application/xml" in [RFC3023],
section 3.2.
File extension: .atomcoll
Fragment identifiers: As specified for "application/xml" in
[RFC3023], section 5.
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Base URI: As specified in [RFC3023], section 6.
Macintosh File Type code: TEXT
Person and email address to contact for further information: Joe
Gregorio <joe@bitworking.org>
Intended usage: COMMON
Author/Change controller: IESG
An Atom Introspection Document, when serialized as XML 1.0, can be
identified with the following media type:
MIME media type name: application
MIME subtype name: atomserv+xml
Mandatory parameters: None.
Optional parameters:
"charset": This parameter has identical semantics to the charset
parameter of the "application/xml" media type as specified in
[RFC3023].
Encoding considerations: Identical to those of "application/xml" as
described in [RFC3023], section 3.2.
Security considerations: As defined in this specification.
[[anchor30: update upon publication]]
In addition, as this media type uses the "+xml" convention, it
shares the same security considerations as described in [RFC3023],
section 10.
Interoperability considerations: There are no known interoperability
issues.
Published specification: This specification. [[anchor31: update upon
publication]]
Applications that use this media type: No known applications
currently use this media type.
Additional information:
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Magic number(s): As specified for "application/xml" in [RFC3023],
section 3.2.
File extension: .atomsrv
Fragment identifiers: As specified for "application/xml" in
[RFC3023], section 5.
Base URI: As specified in [RFC3023], section 6.
Macintosh File Type code: TEXT
Person and email address to contact for further information: Joe
Gregorio <joe@bitworking.org>
Intended usage: COMMON
Author/Change controller: This specification's author(s). [[anchor32:
update upon publication]]
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12. References
12.1 Normative References
[AtomFormat]
Nottingham, M. and R. Sayre, "The Atom Syndication
Format", work-in-progress, April 2005.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, July 2002.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
[W3C.REC-soap12-part1-20030624]
Nielsen, H., Mendelsohn, N., Gudgin, M., Hadley, M., and
J. Moreau, "SOAP Version 1.2 Part 1: Messaging Framework",
W3C REC REC-soap12-part1-20030624, June 2003.
[W3C.REC-soap12-part2-20030624]
Nielsen, H., Hadley, M., Moreau, J., Mendelsohn, N., and
M. Gudgin, "SOAP Version 1.2 Part 2: Adjuncts", W3C
REC REC-soap12-part2-20030624, June 2003.
[W3C.REC-xml-20040204]
Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T.,
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and E. Maler, "Extensible Markup Language (XML) 1.0 (Third
Edition)", W3C REC REC-xml-20040204, February 2004.
12.2 Informative References
[W3C.REC-webarch-20041215]
Walsh, N. and I. Jacobs, "Architecture of the World Wide
Web, Volume One", W3C REC REC-webarch-20041215,
December 2004.
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URIs
[1] <http://www.imc.org/atom-protocol/index.html>
Authors' Addresses
Joe Gregorio (editor)
BitWorking, Inc
1002 Heathwood Dairy Rd.
Apex, NC 27502
US
Phone: +1 919 272 3764
Email: joe@bitworking.com
URI: http://bitworking.com/
Robert Sayre (editor)
Email: rfsayre@boswijck.com
URI: http://boswijck.com
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Appendix A. Revision History
draft-ietf-atompub-protocol-04 - Add ladder diagrams, reorganize, add
SOAP interactions
draft-ietf-atompub-protocol-03 - Incorporates PaceSliceAndDice3 and
PaceIntrospection.
draft-ietf-atompub-protocol-02 - Incorporates Pace409Response,
PacePostLocationMust, and PaceSimpleResourcePosting.
draft-ietf-atompub-protocol-01 - Added in sections on Responses for
the EditURI. Allow 2xx for response to EditURI PUTs. Elided all
mentions of WSSE. Started adding in some normative references.
Added the section "Securing the Atom Protocol". Clarified that it is
possible that the PostURI and FeedURI could be the same URI. Cleaned
up descriptions for Response codes 400 and 500.
Rev draft-ietf-atompub-protocol-00 - 5Jul2004 - Renamed the file and
re-titled the document to conform to IETF submission guidelines.
Changed MIME type to match the one selected for the Atom format.
Numerous typographical fixes. We used to have two 'Introduction'
sections. One of them was moved into the Abstract the other absorbed
the Scope section. IPR and copyright notifications were added.
Rev 09 - 10Dec2003 - Added the section on SOAP enabled clients and
servers.
Rev 08 - 01Dec2003 - Refactored the specification, merging the
Introspection file into the feed format. Also dropped the
distinction between the type of URI used to create new entries and
the kind used to create comments. Dropped user preferences.
Rev 07 - 06Aug2003 - Removed the use of the RSD file for auto-
discovery. Changed copyright until a final standards body is chosen.
Changed query parameters for the search facet to all begin with atom-
to avoid name collisions. Updated all the Entries to follow the 0.2
version. Changed the format of the search results and template file
to a pure element based syntax.
Rev 06 - 24Jul2003 - Moved to PUT for updating Entries. Changed all
the mime-types to application/x.atom+xml. Added template editing.
Changed 'edit-entry' to 'create-entry' in the Introspection file to
more accurately reflect it's purpose.
Rev 05 - 17Jul2003 - Renamed everything Echo into Atom. Added
version numbers in the Revision history. Changed all the mime-types
to application/atom+xml.
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Rev 04 - 15Jul2003 - Updated the RSD version used from 0.7 to 1.0.
Change the method of deleting an Entry from POSTing <delete/> to
using the HTTP DELETE verb. Also changed the query interface to GET
instead of POST. Moved Introspection Discovery to be up under
Introspection. Introduced the term 'facet' for the services listed
in the Introspection file.
Rev 03 - 10Jul2003 - Added a link to the Wiki near the front of the
document. Added a section on finding an Entry. Retrieving an Entry
now broken out into it's own section. Changed the HTTP status code
for a successful editing of an Entry to 205.
Rev 02 - 7Jul2003 - Entries are no longer returned from POSTs,
instead they are retrieved via GET. Cleaned up figure titles, as
they are rendered poorly in HTML. All content-types have been
changed to application/atom+xml.
Rev 01 - 5Jul2003 - Renamed from EchoAPI.html to follow the more
commonly used format: draft-gregorio-NN.html. Renamed all references
to URL to URI. Broke out introspection into it's own section. Added
the Revision History section. Added more to the warning that the
example URIs are not normative.
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Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Gregorio & Sayre Expires November 10, 2005 [Page 36]
