Network Working Group J. Gregorio, Ed.
Internet-Draft BitWorking, Inc
Expires: April 30, 2006 B. de hOra, Ed.
Propylon Ltd.
October 27, 2005
The Atom Publishing Protocol
draft-ietf-atompub-protocol-06.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
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
(draft-ietf-atompub-format-11.txt).
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 Collections . . . . . . . . . . . . . . . . . . . 10
5.5 Success and Failure . . . . . . . . . . . . . . . . . . . 10
6. XML-related Conventions . . . . . . . . . . . . . . . . . . 11
6.1 Referring to Information Items . . . . . . . . . . . . . . 11
6.2 XML Namespace Usage . . . . . . . . . . . . . . . . . . . 11
6.3 RELAX NG Schema . . . . . . . . . . . . . . . . . . . . . 11
6.4 Use of xml:base and xml:lang . . . . . . . . . . . . . . . 11
7. Introspection Documents . . . . . . . . . . . . . . . . . . 13
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 13
7.2 Example . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.3 Element Definitions . . . . . . . . . . . . . . . . . . . 14
7.3.1 The 'app:service' Element . . . . . . . . . . . . . . 14
7.3.2 The 'app:workspace' Element . . . . . . . . . . . . . 14
7.3.3 The 'app:collection' Element . . . . . . . . . . . . . 15
7.3.4 The 'app:member-type' Element . . . . . . . . . . . . 15
7.3.5 The 'app:list-template' Element . . . . . . . . . . . 16
8. Collections . . . . . . . . . . . . . . . . . . . . . . . . 18
8.1 Creating resources with POST . . . . . . . . . . . . . . . 18
8.1.1 Title: Header . . . . . . . . . . . . . . . . . . . . 18
8.2 Entry Collections . . . . . . . . . . . . . . . . . . . . 19
8.2.1 Role of Atom Entry Elements During Editing . . . . . . 19
8.3 Media Collections . . . . . . . . . . . . . . . . . . . . 20
8.3.1 Editing Media Resources . . . . . . . . . . . . . . . 20
9. Listing Collections . . . . . . . . . . . . . . . . . . . . 21
10. Atom Entry Extensions . . . . . . . . . . . . . . . . . . . 23
10.1 The 'edit' Link Relation . . . . . . . . . . . . . . . . 23
10.2 Publishing Control . . . . . . . . . . . . . . . . . . . 23
10.2.1 The app:draft Element . . . . . . . . . . . . . . . 24
11. Example . . . . . . . . . . . . . . . . . . . . . . . . . . 25
12. Securing the Atom Protocol . . . . . . . . . . . . . . . . . 27
13. Security Considerations . . . . . . . . . . . . . . . . . . 28
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . 29
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15. References . . . . . . . . . . . . . . . . . . . . . . . . . 31
15.1 Normative References . . . . . . . . . . . . . . . . . . 31
15.2 Informative References . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 33
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 34
B. RELAX NG Compact Schema . . . . . . . . . . . . . . . . . . 35
C. Revision History . . . . . . . . . . . . . . . . . . . . . . 38
Intellectual Property and Copyright Statements . . . . . . . 40
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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 "Atom Protocol"
or "APP".
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".
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 - A network data object or service that can be identified
by a IRI, as defined in [RFC2616]. See [W3C.REC-webarch-20041215]
for further discussion on resources.
representation - An entity included with a request or response as
defined in [RFC2616].
collection - A resource that contains a set of member IRIs, as
described in Section 8 of this specification.
member - A resource whose IRI is listed in a collection.
IRI template - A parameterized string that becomes a IRI when the
parameters are filled in. See Section 9.
introspection document - A document that describes the location and
capabilities of one or more collections. See Section 7
client writable element - An element of an Atom Entry whose value is
editable by the client and not enforced by the server.
server-controlled element - An element of an Atom Entry whose value
is enforced by the server and not editable by the client.
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4. Protocol Model
The Atom Publishing Protocol uses HTTP to edit resources on the web.
It provides a list based mechanism for managing collections of
editable resources called member resources. Collections contain the
IRIs and metadata describing member resources. The APP uses these
HTTP verbs:
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.
This diagram shows the APP model:
+---------------+
| Introspection | +------------+
| |-->| Collection |
+---------------+ | |
| | +--------+
| |-->| Member |
| | +--------+
| |
| | .
| | .
| | .
| |
| | +--------+
| |-->| Member |
| | +--------+
| |
+------------+
The introspection document contains the IRIs of one or more
collections. A collection contains IRIs and metadata describing
member resources. The protocol allows editing of resources with
representations of any media-type. Some types of collections are
specialized and restrict the resource representations of their
members.
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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 introspection document which
enumerates the IRIs of all the collections, and the capabilities
of those collections, that the service supports.
5.2 Creating a Resource
Client Server
| |
| 1.) POST to IRI of Collection |
|------------------------------------------>|
| |
| 2.) 201 Created |
|<------------------------------------------|
| |
1. The client POSTs a representation 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 member 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 it.
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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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Note: deleting a member also removes it from all the collections to
which it belongs.
5.4 Listing Collections
To enumerate the members of a collection the client sends a GET to
its IRI. This IRI is constructed from information in the
introspection document. An Atom Feed Document is returned with one
Atom Entry for each member resource that matches the selection
criteria in the IRI. 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 membership list 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 Success and Failure
The Atom Protocol uses HTTP status codes to signal the results of
protocol operations. 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. Consult the HTTP specification
[RFC2616] for the definitions of HTTP status codes.
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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 naming 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 URI [W3C.REC-xml-names-19990114] for the data format
described in this specification is:
http://purl.org/atom/app#
This specification uses the prefix "app:" for the Namespace URI. The
choice of namespace prefix is not semantically significant.
This specification also uses the prefix "atom:" for the Namespace URI
identified in [AtomFormat].
6.3 RELAX NG Schema
Some sections of this specification are illustrated with fragments of
a non-normative RELAX NG Compact schema [RNC]. However, the text of
this specification provides the definition of conformance. A
complete schema appears in Appendix B.
6.4 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
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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], .
appCommonAttributes =
attribute xml:base { atomUri }?,
attribute xml:lang { atomLanguageTag }?,
undefinedAttribute*
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7. Introspection Documents
7.1 Introduction
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.
7.2 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 7.3.4.
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.
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Introspection documents are identified with the "application/
atomserv+xml" media type (see Section 14).
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.
7.3 Element Definitions
7.3.1 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* )
}
7.3.2 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* )
}
7.3.2.1 The 'title' Attribute
The app:workspace element MUST contain a 'title' attribute, which
conveys a human-readable name for the workspace. This attribute is
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Language-Sensitive.
7.3.3 The 'app:collection' Element
The app:collection contains information elements that describe the
location and capabilities of a collection.
appCollection =
element app:collection {
appCommonAttributes,
attribute title { text },
attribute href { text },
( appMemberType
& appListTemplate
& extensionElement* )
}
7.3.3.1 The 'title' Attribute
The app:collection element MUST contain a 'title' attribute, whose
value conveys a human-readable name for the collection. This
attribute is Language-Sensitive.
7.3.3.2 The 'href' Attribute
The app:collection element MUST contain an 'href' attribute, whose
value conveys the IRI of the collection.
This specification defines two child elements for app:collection:
o app:member-type: a single element that contains the type of
members that the collection can contain.
o app:list-template: a single element that contains a IRI template
of a membership list. (See Section 9).
7.3.4 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 initial values for the app:member-type
IANA registry:
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.
In general the value of app:member-type MUST be a string that is non-
empty, and matches either the "isegment-nz-nc" or the "IRI"
production in [RFC3987]. Note that use of a relative reference other
than a simple name is not allowed. If a name is given,
implementations MUST consider the link relation type to be equivalent
to the same name registered within the IANA Registry of Link
Relations Section 14, and thus the IRI that would be obtained by
appending the value of the rel attribute to the string
"http://www.iana.org/assignments/member-type/".
7.3.5 The 'app:list-template' Element
The app:collection element MUST contain one 'app:list-template'
elements. The element content of app:list-template is an IRI
template (Section 9) for a collection.
appListTemplate =
element app:list-template {
appCommonAttributes,
( appUriTemplate )
}
appUriTemplate = xsd:string { pattern = ".+\{.+\}.*" }
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8. Collections
8.1 Creating resources with POST
Every collection accepts POST requests to create resources - the
client POSTs a representation of the desired resource to the IRI of
the collection. 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").
The status code returned for a successful creation POST MUST be 201
("Created").
A successful creation POST MUST return a Location: header with the
URI of the newly created resource.
Clients MAY POST invalid Atom for initial resource creation -
specifically the id and link elements MAY be omitted.
Below, the client requests to create a resource 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>
<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
8.1.1 Title: Header
The POST to a collection MAY contain a Title: header that indicates
the client's suggested title for the resource. The server MAY ignore
the Title: header or modify the requested 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 relation of rel="edit" that contains the IRI of the
member resource. Member representations MAY contain an app:control
element (Section 10.2).
8.2.1 Role of Atom Entry Elements During Editing
The elements of an Atom Entry Document are either a client writable
or server controlled.
Client Writable - An element of an Atom Entry whose value is editable
by the client. Servers MAY modify the content of client writable
elements. Some reasons that a server may change client writable
content include length limits, obscenity filters or the addition of
boilerplate text.
Server Controlled - An element of an Atom Entry whose value is
enforced by the server and not editable by the client. Clients
SHOULD NOT change the value of server controlled elements. Servers
MUST NOT rely on clients preserving the values of server controlled
elements.
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+--------------------+--------------------+
| Atom Entry Element | Property |
+--------------------+--------------------+
| atom:author | Client Writable |
| | |
| atom:category | Client Writable |
| | |
| atom:content | Client Writable |
| | |
| atom:contributor | Client Writable |
| | |
| atom:id | Server Controlled |
| | |
| atom:link | Client Writable |
| | |
| atom:published | Client Writable |
| | |
| atom:source | Client Writable |
| | |
| atom:summary | Client Writable |
| | |
| atom:title | Client Writable |
| | |
| atom:updated | Server Controlled |
| | |
| app:control | Client Writable |
+--------------------+--------------------+
Table 1
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. 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 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 contained every entry in the feed, and the
server would waste large amounts of bandwidth and processing time on
clients unable to handle the response.
For this reason, Introspection documents refer to collections not
with IRIs but with IRI Templates, contained in the "app:member-type"
child of "app:collection". An IRI Template is a string containing
the embedded token "{index}".
To produce an IRI that can be used to retrieve part or all of the
collection, software replaces the "{index}" with a pair of positive
integer indices separated by a dash character. An IRI template MUST,
after such substitution has been performed, constitute a
syntactically valid IRI.
One or other index MAY be omitted, in which case the range is
understood as stretching to 0 or infinity. The index values are 0
based and select members from the collection based on the member's
index, with all of the members ordered by their 'atom:updated'
property. The response to the selection request MUST be an Atom Feed
where all the entries fall within the requested criteria. The
request range is considered a closed set - if an entry 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 an
Atom Feed containing no entries. If a membership list is returned
with a number of entries that is less than the number of entries
requested than the client MAY assume that it has made a request that
exceeds the last index of the members.
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For example, suppose the client is supplied this IRI template:
http://example.org/blog/edit/{index}
If the client wants the first 15 entries in the collection it would
substitute the brace-delimited parameter {index}, with the value
0-14, giving:
http://example.org/blog/edit/0-14
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10. Atom Entry Extensions
This specification adds one new value to the Registry of Link
Relations and also adds a new element to Atom Entries called "app:
control" for controlling publishing. These new links and app:
control elements MAY appear in both membership lists and in member
representations.
10.1 The 'edit' Link Relation
This specification adds the value "edit" to the Registry of Link
Relations. The value of "edit" signifies 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.
10.2 Publishing Control
This specification also adds a new element to Atom Entries for
controlling publishing.
pubControl =
element app:control {
atomCommonAttributes,
pubDraft?
& extensionElement
}
pubDraft =
element app:draft { "yes" | "no" }
The "app:control" element MAY appear as a child of an "atom:entry"
which is being created or updated via the Atom Publishing Protocol.
The "app:control" element, if it does appear in an entry, MUST only
appear at most one time.
The "app:control" element and its children elements MAY be included
in Atom Feed or Entry Documents. The "app:control" element is
considered "foreign markup" as defined in Section 6 of the Atom
Syndication Format.
The "app:control" element MAY contain exactly one app:draft element
and MAY contain zero or more extension elements as outlined in the
Atom Syndication Format, Section 6. Both clients and servers MUST
ignore foreign markup present in the app:control element that they do
not know.
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10.2.1 The app:draft Element
This specification defines only one child element for "app:control",
"app:draft".
The number of "app:draft" elements in "app:control" MUST be zero or
one. Its content MUST be one of the values "yes" or "no". A value
of "no" means that the entry MAY be made publicly visible. If the
"app:draft" element is missing then the value is understood to be
"no". That is, if "app:control" and/or the "app:draft" elements are
missing from an entry then the entry is considered not a draft and
can be made publicly visible. Clients MUST understand "app:draft"
elements and MUST NOT drop them from Atom Entries during editing.
Clients MUST NOT operate on the expectation that a server will honor
the value of an "app:draft" element. Servers MAY ignore "app:draft"
elements and drop them from Atom Entries.
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11. 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>
<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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12. 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 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.
12.1 [@@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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13. Security Considerations
The security of Atom is based on HTTP Digest Authentication and/or
[@@TBD@@ CGI Authentication]. Any weaknesses in either of these
authentication schemes will 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 [RFC2617] for the 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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14. IANA Considerations
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.
[[anchor22: 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. [[anchor23: 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). [[anchor24:
update upon publication]]
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15. References
15.1 Normative References
[AtomFormat]
Nottingham, M. and R. Sayre, "The Atom Syndication
Format", 1.0, July 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.
[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-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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15.2 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 APP namespace
which are not defined in this revision of the specification.
Requirements for APP Processors encountering such markup are given in
Section 6.2 and Section 6.3 of [AtomFormat].
# -*- 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,
attribute title { text },
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( 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
}
# Structured Extension
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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-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.
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
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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
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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The IETF invites any interested party to bring to its attention any
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Copyright Statement
Copyright (C) The Internet Society (2005). 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 April 30, 2006 [Page 41]
