I have just submitted an update to the Atom Notification Protocol
draft that will hopefully be published in a day or so. I have
attached the draft for review.
Summary of changes:
* Rather than POSTing atom:feed elements to indicate an updated
feed, atom:head elements are POSTed.
* Eliminated the NotificationURI location mechanisms.
NotificationURI's will be located in some application specific manner.
It didn't make sense at this point in time to define a common
mechanism.
* Head-In-Entry has been marked as a SHOULD
* Expanded treatment of HTTP response codes and HTTP methods
To reiterate the prior discussion that happened on this, I am not
intending this as a competitor to Atom-XMPP. I think both have their
place and both contribute to the General Good. I would appreciate
folks giving this a look over and offering any comments you may have.
--
- James Snell
http://www.snellspace.com
[EMAIL PROTECTED]
Network Working Group J. Snell
Internet-Draft January 31, 2005
Expires: August 1, 2005
The Atom Notification Protocol
draft-snell-atompub-notification-01
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2005). All Rights Reserved.
Abstract
This memo presents a protocol for posting notifications of new or
updated content using a combination of the Atom Syndication Format
and HTTP POSTs.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Notational Conventions . . . . . . . . . . . . . . . . . . 3
1.2 Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. The Atom Notification Protocol Model . . . . . . . . . . . . . 3
3. Functional Specification . . . . . . . . . . . . . . . . . . . 3
3.1 NotificationURI . . . . . . . . . . . . . . . . . . . . . 3
3.1.1 Locating the NotificationURI . . . . . . . . . . . . . 4
3.1.2 Request . . . . . . . . . . . . . . . . . . . . . . . 4
3.1.3 Response . . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . 7
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1. Introduction
The Atom Notification Protocol is an application-level protocol for
posting notification of new or updated content using HTTP and the
Atom Syndication Format.
1.1 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 [1].
1.2 Terminology
Atom Entry: An Atom Entry is a fragment of a full Atom feed. In this
case, the fragment is a single 'entry' element and all its child
elements. Each Atom Entry describes a single Web resource, providing
metadata and optionally a textual representation of that resource.
Atom Head: atom:head elements are used within the Atom Syndication
Format as children of both the atom:feed and atom:entry elements to
provide information descriptive of the feed.
NotificationURI: A HTTP URI that is used to receive notifications
about new or updated Atom entries.
2. The Atom Notification Protocol Model
The Atom Notification Protocol has been designed to complement the
Atom Publishing Protocol by providing the means of sending
notifications when Atom-based content is modified in some way.
The Atom Notification Protocol works by POSTing atom:entry or
atom:head elements to a NotificationURI using HTTP POST.
As is the case with the Atom Publishing Protocol, this document does
not seek to specify the form of the URIs that are used. This
document does, however, specify the formats of the entities posted to
those URIs.
3. Functional Specification
3.1 NotificationURI
The NotificationURI is used to POST notifications. A notification
consists of a single atom:entry or atom:head element. The
notification is essentially a one-way operation that implies no
operational semantics or action on the part of the receiver.
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3.1.1 Locating the NotificationURI
Because of the broad variety of cases in which the Atom Notification
Protocol may be used and the lack of any single operational semantic
for notifications beyond basic delivery, no single location mechanism
for NotificationURI's will be defined. This means that it is up to
specific application profiles to determine the best way to make the
NotificationURI known within the context of that application.
3.1.2 Request
The request contains a filled-in atom:entry or atom:head element.
A notification request containing an atom:entry is intended to notify
the receiving endpoint that a specific entry has been created or
updated.
A notification request containing an atom:head is intended to notify
the receiving endpoint that a specific feed described by the
atom:head has been created or updated.
atom:entry's POSTed to a NotificationURI SHOULD contain a atom:head
element that identifies the feed to which the entry belongs.
atom:head elements POSTed to a NotificationURI MUST have a version
attribute that identifies the Atom Syndication Format version used.
The version attribute is identical to the version attribute defined
for the atom:feed element in the Atom Syndication Format.
<?xml version="1.0" encoding="utf-8"?>
<head version="draft-ietf-atompub-format-05: do not deploy"
xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-05";>
<title>Example Feed</title>
<link href="http://example.org/"/>
<updated>2003-12-13T18:30:02Z</updated>
<author>
<name>John Doe</name>
</author>
</head>
POST is the only method that SHOULD be supported by the
NotificationURI. Clients MUST NOT submit requests using any other
method to the NotificationURI. If a client submits a request using
any other method than POST, The NotificationURI SHOULD respond with a
405 Method Not Allowed response.
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3.1.3 Response
The response to a notification POST MUST be an empty message. That
is, the message MUST NOT contain any content beyond the HTTP headers.
Clients MUST ignore any content that a NotificationURI implementation
happens to include.
3.1.3.1 2xx Response Codes
A response code of 202 indicates that the notification was
successfully received and accepted. The body of the message SHOULD
be empty.
All other 2xx HTTP status codes SHOULD be treated as if they were 202
responses.
3.1.3.2 3xx Response Codes
A response code of 301 indicates that the NotificationURI has
permanently changed locations and that the client MUST NOT make any
further attempts to send notifications to this location. A new
location SHOULD be provided using the Location HTTP header field.
A response code of 302 indicates that the NotificationURI has
temporarily changed locations and that the client SHOULD reissue
their notification to the new location specified in the Location HTTP
header field but that future notifications should continue to be sent
to this location.
NotificationURI's SHOULD NOT return 300, 303, 304, 306 or 307
response codes. If a NotificationURI's does return any of these
codes, they MUST be ignored.
3.1.3.3 4xx Response Codes
All 4xx response codes are to be interpretted as they are defined in
the HTTP specification. 416 and 417 SHOULD NOT be issued by the
NotificationURI and MUST be ignored if they are.
3.1.3.4 5xx Response Codes
All 5xx response codes are to be interpretted as they are defined in
the HTTP specification.
4. Security Considerations
The decision of whether or not to secure the Atom Notification
Protocol will be made on a case-by-case decision. Some notification
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endpoints may be restricted to known authenticated users while others
will be open for anyone who wishes to post notifications. If a given
NotificationURI is restricted, the same authentication mechanism(s)
used by the Atom Publishing Protocol SHOULD be used.
One particular challenge that implementors of NotificationURI
endpoints will need to be aware of is the potential for denial of
service attacks and notification spamming. This document shall not
deal with potential solutions to such attacks.
5. IANA Considerations
This document has no actions for IANA.
6 References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Gregorio, J., Ed. and R. Sayre, Ed., "The Atom Publishing
Protocol", draft-ietf-atompub-protocol-02 (work in progress),
September 2004.
[3] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom Syndication
Format", draft-ietf-atompub-format-05 (work in progress),
January 2005.
Author's Address
James M Snell
EMail: [EMAIL PROTECTED]
URI: http://www.snellspace.com
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