Network Working Group J. Gregorio, Ed.
Internet-Draft BitWorking, Inc
Expires: July 5, 2006 B. de hOra, Ed.
Propylon Ltd.
January 01, 2006
The Atom Publishing Protocol
draft-ietf-atompub-protocol-07.txt
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
The Atom Publishing Protocol (APP) is an application-level protocol
for publishing and editing Web resources. The protocol is based on
HTTP transport of Atom-formatted representations. The Atom format is
documented in the Atom Syndication Format (RFC4287).
Editorial Note
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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 . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . 7
5. Protocol Operations . . . . . . . . . . . . . . . . . . . . 8
5.1 Retrieving an Introspection Document . . . . . . . . . . . 8
5.2 Creating a Resource . . . . . . . . . . . . . . . . . . . 8
5.3 Editing a Resource . . . . . . . . . . . . . . . . . . . . 8
5.3.1 Retrieving a Resource . . . . . . . . . . . . . . . . 9
5.3.2 Updating a Resource . . . . . . . . . . . . . . . . . 9
5.3.3 Deleting a Resource . . . . . . . . . . . . . . . . . 9
5.4 Listing Collection Members . . . . . . . . . . . . . . . . 10
5.5 Use of HTTP Response codes . . . . . . . . . . . . . . . . 10
6. XML-related Conventions . . . . . . . . . . . . . . . . . . 11
6.1 Referring to Information Items . . . . . . . . . . . . . . 11
6.2 XML Namespace Usage . . . . . . . . . . . . . . . . . . . 11
6.3 Use of xml:base and xml:lang . . . . . . . . . . . . . . . 11
6.4 RELAX NG Schema . . . . . . . . . . . . . . . . . . . . . 12
7. Introspection Documents . . . . . . . . . . . . . . . . . . 13
7.1 Example . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.2 Element Definitions . . . . . . . . . . . . . . . . . . . 14
7.2.1 The "app:service" Element . . . . . . . . . . . . . . 14
7.2.2 The "app:workspace" Element . . . . . . . . . . . . . 14
7.2.3 The "app:collection" Element . . . . . . . . . . . . . 15
7.2.4 The "app:member-type" Element . . . . . . . . . . . . 15
8. Collections . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1 Creating resources with POST . . . . . . . . . . . . . . . 17
8.1.1 Example . . . . . . . . . . . . . . . . . . . . . . . 17
8.1.2 Title: Header . . . . . . . . . . . . . . . . . . . . 17
8.2 Entry Collections . . . . . . . . . . . . . . . . . . . . 18
8.3 Media Collections . . . . . . . . . . . . . . . . . . . . 18
8.3.1 Editing Media Resources . . . . . . . . . . . . . . . 18
9. Listing Collections . . . . . . . . . . . . . . . . . . . . 19
9.1 Collection Paging . . . . . . . . . . . . . . . . . . . . 19
10. Atom Format Link Relation Extensions . . . . . . . . . . . . 21
10.1 The "edit" Link Relation . . . . . . . . . . . . . . . . 21
11. Atom Publishing Control Extensions . . . . . . . . . . . . . 22
11.1 The Atom Publishing Control Namespace . . . . . . . . . 22
11.2 The "pub:control" Element . . . . . . . . . . . . . . . 22
11.2.1 The "pub:draft" Element . . . . . . . . . . . . . . 22
12. Atom Publishing Protocol Example . . . . . . . . . . . . . . 23
13. Securing the Atom Protocol . . . . . . . . . . . . . . . . . 25
14. Security Considerations . . . . . . . . . . . . . . . . . . 26
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15. IANA Considerations . . . . . . . . . . . . . . . . . . . . 27
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
16.1 Normative References . . . . . . . . . . . . . . . . . . 29
16.2 Informative References . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 31
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 32
B. RELAX NG Compact Schema . . . . . . . . . . . . . . . . . . 33
C. Revision History . . . . . . . . . . . . . . . . . . . . . . 36
Intellectual Property and Copyright Statements . . . . . . . 39
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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]. The protocol supports the creation of
arbitrary web resources and provides facilities for:
o Collections: Sets of resources, which may be retrieved in whole or
in part.
o Introspection: Discovering and describing collections.
o Editing: Creating, updating and deleting resources.
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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].
Note: The Introspection Document allows the use of IRIs [RFC3987], as
well as URIs [RFC3986]. Every URI is an IRI, so any URI can be used
where an IRI is needed. How to map an IRI to a URI is specified in
Section 3.1 of Internationalized Resource Identifiers (IRIs)
[RFC3987].
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3. Terminology
For convenience, this protocol may be referred to as the "Atom
Protocol" or "APP".
URI/IRI - A Uniform Resource Identifier and Internationalized
Resource Identifier. These terms and the distinction between them
are defined in [RFC3986] and [RFC3987].
Resource - A network-accessible data object or service identified by
an IRI, as defined in [RFC2616]. See [W3C.REC-webarch-20041215] for
further discussion on resources.
The phrase "the IRI of a document" in this specification is shorthand
for "an IRI which, when dereferenced, is expected to produce that
document as a representation".
Representation - An entity included with a request or response as
defined in [RFC2616].
Collection - A resource that contains a set of member IRIs. See
Section 8.
Member - A resource whose IRI is listed in a Collection.
Introspection Document - A document that describes the location and
capabilities of one or more Collections. See Section 7.
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4. Protocol Model
The Atom Publishing Protocol uses HTTP to edit and author web
resources. The Atom Protocol uses the following HTTP methods:
o GET is used to retrieve a representation of a resource or perform
a 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.
Along with operations on resources, the Atom Protocol provides list-
based structures, called Collections, for managing and organising
resources, called Members. Collections contain the IRIs of, and
metadata about, their Member resources. For authoring and editing of
resources to commence, an Atom Protocol client can examine server-
defined groups of Collections, called Introspection Documents.
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5. Protocol Operations
5.1 Retrieving an Introspection Document
Client Server
| |
| 1.) GET to IRI of Introspection Document |
|------------------------------------------>|
| |
| 2.) Introspection Document |
|<------------------------------------------|
| |
1. The client sends a GET request to the IRI of the Introspection
Document.
2. The server responds with the document which enumerates the IRIs
of all the Collections and the capabilities of those Collections
supported by the server. The content of this document can vary
based on aspects of the client request, including, but not
limited to, authentication credentials.
5.2 Creating a Resource
Client Server
| |
| 1.) POST to IRI of Collection |
|------------------------------------------>|
| |
| 2.) 201 Created |
|<------------------------------------------|
| |
1. The client POSTs a representation of the Member to the IRI of the
collection.
2. If the Member resource was created successfully, the server
responds with a status code of 201 and a Location: header that
contains the IRI of the newly created resource.
5.3 Editing a Resource
Once a resource has been created and its IRI is known, that IRI may
be used to retrieve, update, and delete the resource.
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5.3.1 Retrieving a Resource
Client Server
| |
| 1.) GET to Member IRI |
|------------------------------------------>|
| |
| 2.) Member Representation |
|<------------------------------------------|
| |
1. The client sends a GET request to the Member's IRI to retrieve
its representation.
2. The server responds with the representation of the resource.
5.3.2 Updating a Resource
Client Server
| |
| 1.) PUT to Member IRI |
|------------------------------------------>|
| |
| 2.) 200 OK |
|<------------------------------------------|
1. The client PUTs an updated representation to the Member's IRI.
2. Upon a successful update of the resource the server responds with
a status code of 200.
5.3.3 Deleting a Resource
Client Server
| |
| 1.) DELETE to Member Resource IRI |
|------------------------------------------>|
| |
| 2.) 200 Ok |
|<------------------------------------------|
| |
1. The client sends a DELETE request to the Member's IRI.
2. Upon the successful deletion of the resource the server responds
with a status code of 200.
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5.4 Listing Collection Members
To list the members of a Collection the client sends a GET request to
the Collection's IRI. An Atom Feed Document is returned containing
one Atom Entry for each member resource. See Section 9 and
Section 10 for a description of the feed contents.
Client Server
| |
| 1.) GET to List IRI |
|------------------------------->|
| |
| 2.) 200 OK, Atom Feed Doc |
|<-------------------------------|
| |
1. The client sends a GET request to the Collection's IRI.
2. The server responds with an Atom Feed Document containing the
IRIs of all the collection members that match the selection
criteria.
5.5 Use of HTTP Response codes
The Atom Protocol uses the response status codes defined in HTTP to
indicate the success or failure of an operation. Consult the HTTP
specification [RFC2616] for detailed definitions of each status code.
It is strongly recommended that entities contained within HTTP 4xx
and 5xx responses include a human readable, natural language
explanation of the error.
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6. XML-related Conventions
The data format in this specification is specified in terms of the
XML Information Set, serialised as XML 1.0 [W3C.REC-xml-20040204].
Atom Publishing Protocol Documents MUST be well-formed XML. This
specification does not define any DTDs for Atom Protocol, and hence
does not require them to be "valid" in the sense used by XML.
6.1 Referring to Information Items
This specification uses a shorthand for two common terms: the phrase
"Information Item" is omitted when discussing Element Information
Items and Attribute Information Items. Therefore, when this
specification uses the term "element," it is referring to an Element
Information Item in Infoset terms. Likewise, when it uses the term
"attribute," it is referring to an Attribute Information Item.
6.2 XML Namespace Usage
The namespace name [W3C.REC-xml-names-19990114] for the XML format
described in this specification is:
http://purl.org/atom/app#
This specification uses the prefix "app:" for the namespace name.
The choice of namespace prefix is not semantically significant.
This specification also uses the prefix "atom:" for
"http://www.w3.org/2005/Atom", the namespace name of the Atom
Publishing Format [RFC4287].
6.3 Use of xml:base and xml:lang
XML elements defined by this specification MAY have an xml:base
attribute [W3C.REC-xmlbase-20010627]. When xml:base is used, it
serves the function described in section 5.1.1 of [RFC3986],
establishing the base URI (or IRI) for resolving any relative
references found within the effective scope of the xml:base
attribute.
Any element defined by this specification MAY have an xml:lang
attribute, whose content indicates the natural language for the
element and its descendents. The language context is only
significant for elements and attributes declared to be "Language-
Sensitive" by this specification. Requirements regarding the content
and interpretation of xml:lang are specified in Section 2.12 of XML
1.0 [W3C.REC-xml-20040204].
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appCommonAttributes =
attribute xml:base { atomUri }?,
attribute xml:lang { atomLanguageTag }?,
undefinedAttribute*
6.4 RELAX NG Schema
Some sections of this specification are illustrated with fragments of
a non-normative RELAX NG Compact schema [RNC]. A complete schema
appears in Appendix B. However, the text of this specification
provides the definition of conformance.
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7. Introspection Documents
For authoring to commence, a client needs to first discover the
capabilities and locations of collections offered. This is done
using Introspection Documents. An Introspection Document describes
workspaces, which are server-defined groupings of collections.
Introspection documents are identified with the "application/
atomserv+xml" media type (see Section 15).
While an introspection document allows multiple workspaces, there is
no requirement that a service support multiple workspaces. In
addition, a collection MAY appear in more than one workspace.
7.1 Example
<?xml version="1.0" encoding='utf-8'?>
<service xmlns="http://purl.org/atom/app#">
<workspace title="Main Site" >
<collection
title="My Blog Entries"
href="http://example.org/reilly/main" >
<member-type>entry</member-type>
<list-template>http://example.org/{index}</list-template>
</collection>
<collection
title="Pictures"
href="http://example.org/reilly/pic" >
<member-type>media</member-type>
<list-template>http://example.org/p/{index}</list-template>
</collection>
</workspace>
<workspace title="Side Bar Blog">
<collection title="Remaindered Links"
href="http://example.org/reilly/list" >
<member-type>entry</member-type>
<list-template>http://example.org/l/{index}</list-template>
</collection>
</workspace>
</service>
This Introspection Document describes two workspaces. The first,
called "Main Site", has two collections called "My Blog Entries" and
"Pictures" whose IRIs are "http://example.org/reilly/main" and
"http://example.org/reilly/pic" respectively. "My Blog Entries" is
an Entry collection and "Pictures" is a Media collection. Entry and
Media collections are discussed in Section 7.2.4.
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The second workspace is called "Side Bar Blog" and has a single
collection called "Remaindered Links" whose collection IRI is
"http://example.org/reilly/list". "Remaindered Links" is an Entry
collection.
7.2 Element Definitions
7.2.1 The "app:service" Element
The root of an introspection document is the "app:service" element.
namespace app = "http://purl.org/atom/app#"
start = appService
The "app:service" element is the container for introspection
information associated with one or more workspaces. An app:service
element MUST contain one or more app:workspace elements.
appService =
element app:service {
appCommonAttributes,
( appWorkspace+
& extensionElement* )
}
7.2.2 The "app:workspace" Element
The "app:workspace" element contains information elements about the
collections of resources available for editing. The app:workspace
element MUST contain one or more app:collection elements.
appWorkspace =
element app:workspace {
appCommonAttributes,
attribute title { text },
( appCollection+
& extensionElement* )
}
In an app:workspace element, the first app:collection element SHOULD
refer to the preferred or primary collection. In the following
example, the "Entries" collection would be considered the "preferred"
or "primary" collection of the workspace:
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<service>
<workspace title="My Blog">
<collection title="Entries" ... >
<collection title="Photos" ... >
</workspace>
</service>
7.2.2.1 The "title" Attribute
The app:workspace element MUST contain a "title" attribute, which
gives a human-readable name for the workspace. This attribute is
Language-Sensitive.
7.2.3 The "app:collection" Element
The "app:collection" describes a collection. This specification
defines one child element: app:member-type.
appCollection =
element app:collection {
appCommonAttributes,
attribute title { text },
attribute href { text },
( appMemberType
& appListTemplate
& extensionElement* )
}
7.2.3.1 The "title" Attribute
The app:collection element MUST contain a "title" attribute, whose
value gives a human-readable name for the collection. This attribute
is Language-Sensitive.
7.2.3.2 The "href" Attribute
The app:collection element MUST contain a "href" attribute, whose
value gives the IRI of the collection.
7.2.4 The "app:member-type" Element
The app:collection element MUST contain one "app:member-type"
element. The app:member-type element value specifies the types of
members that can appear in the collection.
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appMemberType =
element app:member-type {
appCommonAttributes,
( appTypeValue )
}
appTypeValue = "entry" | "media"
An Entry POSTed to a collection MUST meet the constraints of the app:
member-type element.
This specification defines two values for the app:member-type
element:
o "entry" - The collection contains only member resources whose
representation MUST be an Atom Entry. Further constraints on the
representations of members in a collection of type "entry" are
listed in Section 8.2.
o "media" - The collection contains member resources whose
representation can be of any media type. Additional constraints
are listed in Section 8.3.
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8. Collections
8.1 Creating resources with POST
To add members to a collection, clients send POST requests to the
collection's URI. Collections MAY impose constraints on the media-
types that are created in a collection and MAY generate a response
with a status code of 415 ("Unsupported Media Type"). On successful
creation, the response to the POST request MUST return a Location:
header with the URI of the newly created resource.
8.1.1 Example
Below, the client requests to create a resource with an Atom Entry
representation in a collection:
POST /edit HTTP/1.1
Host: example.org
User-Agent: Thingio/1.0
Content-Type: application/atom+xml
Content-Length: nnn
<entry xmlns="http://www.w3.org/2005/Atom">
<title>Atom-Powered Robots Run Amok</title>
<link href="http://example.org/2003/12/13/atom03"/>
<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
<updated>2003-12-13T18:30:02Z</updated>
<summary>Some text.</summary>
</entry>
The resource is created by sending an Atom Entry as the entity body.
Successful creation is indicated by a 201 created response and
includes a Location: header:
HTTP/1.1 201 Created
Date: Fri, 7 Oct 2005 17:17:11 GMT
Content-Length: 0
Location: http://example.org/edit/first-post.atom
8.1.2 Title: Header
A POST to a collection creating a resource MAY contain a Title:
header that indicates the client's suggested title for the resource.
The Title header is primarily for use with Media collections and is
RECOMMENDED for use with such collections. The server MAY ignore the
content of the Title: header or modify the suggested title.
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Title = "Title" ":" [text]
The syntax of this header MUST conform to the augmented BNF grammar
in section 2.1 of the HTTP/1.1 specification [RFC2616].
8.2 Entry Collections
Entry Collections are collections that restrict their membership to
Atom Entries. They are identified by having an app:member-type of
"entry". Every member representation MUST contain an atom:link
element with a link relation of "edit" that contains the IRI of the
member resource. Member representations MAY contain an app:control
element (Section 11).
8.3 Media Collections
Media Collections are collections whose member representations are
not constrained. They are identified by having an app:member-type of
"media".
8.3.1 Editing Media Resources
When a membership list resource returns an Atom Feed enumerating the
contents of a Media Collection, all the Entries MUST have an atom:
content element with a "src" attribute. When creating a public,
read-only reference to the member resource, a client SHOULD use the
"atom:content/@src" attribute value.
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9. Listing Collections
Collections, as identified in an Introspection Document, are
resources that MUST provide representations in the form of Atom Feed
documents when dereferencing the collection IRI. The entries in the
returned Feed MUST be ordered by their 'atom:updated' property, with
the most recently updated entries coming first in the document order.
Every entry in the Feed Document MUST have an atom:link element with
a relation of "edit" (See Section 10.1). Clients MUST NOT assume
that an Atom Entry returned in the Feed is a full representation of a
member resource. The value of atom:updated is only changed when the
change to a member resource is considered significant. Insignificant
changes do not result in changes to the atom:updated value and thus
do not change the position of the corresponding entry in a membership
list. Clients SHOULD be constructed with this in mind and SHOULD
perform a GET on the member resource before editing.
Collections can contain large numbers of resources. A naive client
such as a web spider or web browser could be overwhelmed if the
response to a GET contained every entry in the collection, and the
server would waste large amounts of bandwidth and processing time on
clients unable to handle the response. For this reason, servers MAY
return a partial listing containing the most recently updated member
resources. Such partial feed documents MUST have an atom:link with a
"next" relation whose "href" value is the IRI of the next partial
listing of the collection (the least recently updated member
resources) where it exists. This is called "collection paging".
9.1 Collection Paging
Atom Protocol servers MUST provide representations of collections as
Atom feed documents whose entries represent the collection's members.
The returned Atom feed MAY NOT contain entries for all the
collection's members. Instead, the Atom feed document MAY contain
link elements with "rel" attribute values of "next", "previous",
"start" and "end" that can be used to navigate through the complete
set of matching entries.
For instance, suppose the client is supplied this IRI
http://example.org/entries/go
Supposing the collection contains member entries and the server as a
matter of policy wishes to avoid generating feed documents with more
than 10 entries, then the resulting Atom feed document represents the
first page in a linked set of 10 feed documents. Within each feed
document served, "next" and "prev" link elements reference the
preceding and subsequent feed documents in the set. The "start" link
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element references the first feed document in the set. The "end"
link element references the final feed document in the set.
<feed xmlns="http://www.w3.org/2005/Atom">
...
<link rel="start"
href="http://example.org/entries/go" />
<link rel="next"
href="http://example.org/entries/2" />
<link rel="last"
href="http://example.org/entries/10" />
</feed>
The 'next' and 'prev' link elements for the feed located at
http://example.org/entries/2 would look like this:
<feed xmlns="http://www.w3.org/2005/Atom">
...
<link rel="start"
href="http://example.org/entries/go" />
<link rel="previous"
href="http://example.org/entries/go" />
<link rel="next"
href="http://example.org/entries/3" />
<link rel="last"
href="http://example.org/entries/10" />
</feed>
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10. Atom Format Link Relation Extensions
10.1 The "edit" Link Relation
The Atom Protocol adds the value "edit" to the Atom Registry of Link
Relations (see section 7.1 of [RFC4287]). The value of "edit"
specifies that the IRI in the value of the href attribute is the IRI
of the member resource, and is intended to be used to update and
delete resources as described in this specification. This link
relation MAY appear in both membership lists and in member
representations.
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11. Atom Publishing Control Extensions
11.1 The Atom Publishing Control Namespace
This specification defines an Atom Format extension for publishing
control called Atom Publishing Control. The namespace name for the
Atom Publishing Control's XML vocabulary is
"http://example.net/appns/". This specification uses "pub:" for the
namespace prefix. The choice of namespace prefix is not semantically
significant.
11.2 The "pub:control" Element
namespace pub = "http://example.net/appns/"
pubControl =
element pub:control {
atomCommonAttributes,
pubDraft?
& extensionElement
}
pubDraft =
element pub:draft { "yes" | "no" }
The "pub:control" element MAY appear as a child of an "atom:entry"
which is being created or updated via the Atom Publishing Protocol.
The "pub:control" element, if it does appear in an entry, MUST only
appear at most one time. The "pub:control" element is considered
foreign markup as defined in Section 6 of [RFC4287].
The "pub:control" element and its child elements MAY be included in
Atom Feed or Entry Documents.
The "pub:control" element MAY contain exactly one "pub:draft" element
as defined here, and MAY contain zero or more extension elements as
outlined in Section 6 of [RFC4287]. Both clients and servers MUST
ignore foreign markup present in the pub:control element.
11.2.1 The "pub:draft" Element
The number of "pub:draft" elements in "pub:control" MUST be zero or
one. Its value MUST be one of "yes" or "no". A value of "no" means
that the entry may be made publicly visible. If the "pub:draft"
element is missing then the value is understood to be "no". If "pub:
control" and/or the "pub:draft" elements are missing from an entry
then the entry is not considered a draft and can be made publicly
visible.
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12. Atom Publishing Protocol Example
This is an example of a client creating a new entry with an image.
The client has an image to publish and an entry that includes an HTML
"img" element that uses that image. In this scenario we consider a
client that has IRIs of two collections, an entry collection and a
media collection, both of which were discovered through an
introspection document. The IRI of the entry collection is:
http://example.net/blog/edit/
The IRI of the media collection is:
http://example.net/binary/edit
First the client creates a new image resource by POSTing the image to
the IRI of the media collection.
POST /binary/edit/ HTTP/1.1
Host: example.net
User-Agent: Thingio/1.0
Content-Type: image/png
Content-Length: nnnn
Title: A picture of the beach
...binary data...
The member resource is created and an HTTP status code of 201 is
returned.
HTTP/1.1 201 Created
Date: Fri, 25 Mar 2005 17:17:11 GMT
Content-Length: nnnn
Content-Type: application/atom+xml
Location: http://example.net/binary/edit/b/129.png
<?xml version="1.0" encoding="utf-8"?>
<entry xmlns="http://www.w3.org/2005/Atom">
<title>A picture of the beach.</title>
<link rel="edit"
href="http://example.net/binary/edit/b/129.png"/>
<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-568596895695</id>
<updated>2005-09-02T10:30:00Z</updated>
<summary>Waves</summary>
<content type="image/png"
src="http://example.net/binary/readonly/129.png"/>
</entry>
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The client then POSTs the Atom Entry that refers to the newly created
image resource. Note that the client takes the IRI
http://example.net/binary/readonly/129.png and uses it in the 'img'
element in the Entry content:
POST /blog/edit/ HTTP/1.1
Host: example.net
User-Agent: Thingio/1.0
Content-Type: application/atom+xml
Content-Length: nnnn
<?xml version="1.0" encoding="utf-8"?>
<entry xmlns="http://www.w3.org/2005/Atom">
<title>What I did on my summer vacation</title>
<link href="http://example.org/atom05"/>
<id>urn:uuid:1225c695-ffb8-4ebb-aaaa-80da354efa6a</id>
<updated>2005-09-02T10:30:00Z</updated>
<summary>Beach!</summary>
<content type="xhtml" xml:lang="en">
<div xmlns="http://www.w3.org/1999/xhtml">
<p>We went to the beach for summer vacation.
Here is a picture of the waves rolling in:
<img
src="http://example.net/binary/readonly/129.png"
alt="A picture of the beach."
/>
</p>
</div>
</content>
</entry>
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13. Securing the Atom Protocol
All instances of publishing Atom Format entries SHOULD be protected
by authentication to prevent posting or editing by unknown sources.
Atom Protocol servers and clients MUST support one of the following
authentication mechanisms, and SHOULD support both.
o HTTP Digest Authentication [RFC2617]
o CGI Authentication
Atom Protocol servers and clients MAY support encryption of the
session using TLS (see [RFC2246]).
There are cases where an authentication mechanism is not be required,
such as a publicly editable Wiki, or when using POST to send comments
to a site that does not require authentication from a commenter.
13.1 CGI Authentication
[[anchor26: This section is incomplete; cgi-authentication is
described but is unspecified.]] This authentication method is
included as part of the protocol to allow Atom Protocol 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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14. Security Considerations
The security of the Atom Protocol is based on HTTP Digest
Authentication and/or CGI Authentication [[anchor28: refers to
incomplete section]]. Any weaknesses in either of these
authentication schemes will affect the security of the Atom
Publishing Protocol.
Both HTTP Digest Authentication and CGI Authentication [[anchor29:
refers to incomplete section]] 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 [RFC2617] for the description of the security properties of HTTP
Digest Authentication.
[[anchor30: expand on HTTP basic and digest authentication, or
refer.]]
[[anchor31: talk here about denial of service attacks using large XML
files, or the billion laughs DTD attack.]]
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15. IANA Considerations
An Atom Publishing Protocol 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.
[[anchor32: 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. [[anchor33: 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: .atomsrv
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: This specification's author(s). [[anchor34:
update upon publication]]
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16. References
16.1 Normative References
[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.
[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.
[RFC4287] Nottingham, M. and R. Sayre, "The Atom Syndication
Format", RFC 4287, December 2005.
[W3C.REC-xml-20040204]
Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T.,
and E. Maler, "Extensible Markup Language (XML) 1.0 (Third
Edition)", W3C REC REC-xml-20040204, February 2004.
[W3C.REC-xml-names-19990114]
Hollander, D., Bray, T., and A. Layman, "Namespaces in
XML", W3C REC REC-xml-names-19990114, January 1999.
[W3C.REC-xmlbase-20010627]
Marsh, J., "XML Base", W3C REC W3C.REC-xmlbase-20010627,
June 2001.
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16.2 Informative References
[RNC] Clark, J., "RELAX NG Compact Syntax", December 2001.
[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/
Bill de hOra (editor)
Propylon Ltd.
45 Blackbourne Square, Rathfarnham Gate
Dublin, Dublin D14
IE
Phone: +353-1-4927444
Email: bill.dehora@propylon.com
URI: http://www.propylon.com/
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Appendix A. Contributors
The content and concepts within are a product of the Atom community
and the Atompub Working Group.
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Appendix B. RELAX NG Compact Schema
This appendix is informative.
The Relax NG schema explicitly excludes elements in the Atom Protocol
namespace which are not defined in this revision of the
specification. Requirements for Atom Protocol processors
encountering such markup are given in Section 6.2 and Section 6.3 of
[RFC4287].
# -*- rnc -*-
# RELAX NG Compact Syntax Grammar for the Atom Protocol
namespace app = "http://purl.org/atom/app#"
namespace local = ""
start = appService
# common:attrs
appCommonAttributes =
attribute xml:base { atomUri }?,
attribute xml:lang { atomLanguageTag }?,
undefinedAttribute*
undefinedAttribute =
attribute * - (xml:base | xml:lang | local:*) { text }
atomUri = text
atomLanguageTag = xsd:string {
pattern = "[A-Za-z]{1,8}(-[A-Za-z0-9]{1,8})*"
}
# app:service
appService =
element app:service {
appCommonAttributes,
( appWorkspace+
& extensionElement* )
}
# app:workspace
appWorkspace =
element app:workspace {
appCommonAttributes,
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attribute title { text },
( appCollection+
& extensionElement* )
}
# app:collection
appCollection =
element app:collection {
appCommonAttributes,
attribute title { text },
attribute href { text },
( appMemberType
& appListTemplate
& extensionElement* )
}
# app:member
appMemberType =
element app:member-type {
appCommonAttributes,
( appTypeValue )
}
appTypeValue = "entry" | "media"
# app:list-template
appListTemplate =
element app:list-template {
appCommonAttributes,
( appUriTemplate )
}
# Whatever an IRI template is, it contains at least {index}
appUriTemplate = xsd:string { pattern = ".+\{index\}.*" }
# Simple Extension
simpleExtensionElement =
element * - app:* {
text
}
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# Structured Extension
structuredExtensionElement =
element * - app:* {
(attribute * { text }+,
(text|anyElement)*)
| (attribute * { text }*,
(text?, anyElement+, (text|anyElement)*))
}
# Other Extensibility
extensionElement =
simpleExtensionElement | structuredExtensionElement
# Extensions
anyElement =
element * {
(attribute * { text }
| text
| anyElement)*
}
# EOF
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Appendix C. Revision History
draft-ietf-atompub-protocol-07: updated Atom refs to RFC4287;
incorporated PaceBetterHttpResponseCode;
PaceClarifyCollectionAndDeleteMethodByWritingLessInsteadOfMore;
PaceRemoveAcceptPostText; PaceRemoveListTemplate2;
PaceRemoveRegistry; PaceRemoveWhoWritesWhat;
PaceSimplifyClarifyBetterfyRemoveBogusValidityText;
PaceCollectionOrderSignificance; PaceFixLostIntrospectionText;
PaceListPaging; PaceCollectionControl; element typo in Listing
collections para3 (was app:member-type, not app:list-template);
changed post atom entry example to be valid. Dropped inline use of
'APP'. Removed nested diagram from section 4. Added ed notes in the
security section.
draft-ietf-atompub-protocol-06 - Removed: Robert Sayre from the
contributors section per his request. Added in
PaceCollectionControl. Fixed all the {daterange} verbage and
examples so they all use a dash. Added full rnc schema. Collapsed
Introspection and Collection documents into a single document.
Removed {dateRange} queries. Renamed search to list. Moved
discussion of media and entry collection until later in the document
and tied the discussion to the Introspection element app:member-type.
draft-ietf-atompub-protocol-05 - Added: Contributors section. Added:
de hOra to editors. Fixed: typos. Added diagrams and description to
model section. Incorporates PaceAppDocuments, PaceAppDocuments2,
PaceSimplifyCollections2 (large-sized chunks of it anyhow: the
notions of Entry and Generic resources, the section 4 language on the
Protocol Model, 4.1 through 4.5.2, the notion of a Collection
document, as in Section 5 through 5.3, Section 7 "Collection
resources", Selection resources (modified from pace which talked
about search); results in major mods to Collection Documents, Section
9.2 "Title: Header" and brokeout para to section 9.1 Editing Generic
Resources). Added XML namespace and language section. Some cleanup
of front matter. Added Language Sensitivity to some attributes.
Removed resource descriptions from terminology. Some juggling of
sections. See:
http://www.imc.org/atom-protocol/mail-archive/msg01812.html.
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.
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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 its 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.
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 its own section. Changed the HTTP status code
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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 its own section. Added
the Revision History section. Added more to the warning that the
example URIs are not normative.
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Copyright Statement
Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
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Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Gregorio & de hOra Expires July 5, 2006 [Page 40]
