NOTES TO book "RSS und Atom"
title: RSS und Atom - kurz & gut
author: Jörg Kantel
kind: topic explanation
pages: 90
chapters: 5
language: German
publisher: O'Reilly
published in: 2007 (1. edition)
ISBN: 978-3-89721-527-6
comment: Nice introduction to topic. But nothing special.
summary: RSS specifications, purposes, Apple-Technology, Readers & Writers, Web 2.0

Software, XML and RSS
=====================

Software for PHP:
- packages in XML-Manipulation (http://de.php.net/manual/en/refs.xml.php)

Software for Perl:
- XML::RSS (http://perl-rss.sourceforge.net/)

Software for Python:
- PyRSS2Gen
- RSS libs @ Python Wiki (http://wiki.python.org/moin/RssLibraries)




(P)CDATA
--------

in general no HTML, except when CDATA.

CDATA
  Character Data

PCDATA
  Parsable Character Data




WTH is Enclosure?
-----------------

enclosure
  angehängte Datei bei einem Feed. Mit den Eigenschaften url 
  (selbsterklärend), length (in bytes) und type (MIME). Zitat 
  aus dem Chaosradio-Feed :-)

<enclosure type="audio/mpeg" url="http://chaosradio.ccc.de/archive/chaosradio_149.mp3" length="84114540"/>



WTH means guid
--------------

guid
  Globally Unique Identifier


  
  
Example files
=============

Metainformation in examples
---------------------------

Lukas' Weblog
  title of weblog
A Weblog about my life and everything else
  subtitle of weblog
http://lukas-prokop.at/blog/
  URL to weblog
Ed Itor
  main editor, writer, author
ed@it.org
  the author's emailaddress
Geek Hacker
  the technical master of the weblog
geek@hacker.org
  the emailadress of the technical master


RSS 2.0
-------

+----------------------------+---------------+
| XPath to element           | maximal chars |
|                            | characters or |
|                            | RFC-standard  |
+============================+===============+
| /rss/channel/title         | 100           |
| /rss/channel/link          | 500           |
| /rss/channel/description   | 500           |
| /rss/channel/language      | RFC 1766      |
| //pubDate                  | RFC 2822      |
| /rss/channel/lastBuildDate | RFC 2822      |
| //image/width              | 144           |
| //image/height             | 400           |
| /rss/channel/rating        | 500           |
| //textInput/title          | 100           |
| //textInput/description    | 500           |
| //textInput/name           | 20            |
| //textInput/link           | 500           |
+----------------------------+---------------+

+----------------------------+-------------+
| XPath to element           | appearance  |
+============================+=============+
| //image/url                | required    |
| //image/title              | required    |
| //image/link               | required    |
| //image/width              | required    |
| //image/height             | required    |
| //image/description        | required    |
+----------------------------+-------------+

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0">
	<channel>
		<title>Lukas' Weblog</title>
		<link>http://lukas-prokop.at/blog/</link>
		<description>A Weblog about my life and everything else</description>
		<language>de-de</language>
		<copyright>Copyleft 1991-2009 by Ed Itor</copyright>
		<managingEditor>ed@it.org (Ed Itor)</managingEditor>
		<webMaster>geek@hacker.org (Geek Hacker)</webMaster>
		<pubDate>Mon, 03 Aug 2009 20:38:30 +0000 $ date of publication, if greater than now, ignore it</pubDate>
		<lastBuildDate>Mon, 03 Aug 2009 20:38:30 +0000 $ date of generation; cannot be greater than now</lastBuildDate>
		<category>Weblog/Private $ path-similar structure to integrate the weblog globally; unspecified</category>
		<generator>PyRSS2Gen $ generator of RSS-document</generator>
		<docs>http://cyber.law.harvard.edu/rss/rss.html $ URL to RSS-specification</docs>
		<!-- see [*]_ -->
		<cloud domain="rpc.sys.com" port="80" path="/RPC2" registerProcedure="myCloud.rssPleaseNotify" protocol="xml-rpc" />
		<ttl>86400 $ seconds after the aggregator should parse the feed again</ttl>
		<!--
			image element:
				* RSS2   : optional
				* RSS0.92: required
		-->
		<image>
			<url>http://lukas-prokop.at/blog/titlepic.jpg $ URL to image</url>
			<title>a nice avatar $ Beschreibung der Graphik; wie alt="" in HTML</title>
			<link>http://lukas-prokop.at/blog/feed.rss $ URL zum Feed</link>
			<width>88 $ default 88</width>
			<height>31 $ default 31</height>
			<description>Avatar $ wie title="" in HTML</description>
		</image>
		<rating>?? $ PICS-rating; see http://w3.org/PICS/ </rating>
		<textInput>
			<title>Newsletter abbestellen</title>
			<description>Bitte ihre ID eingeben und ihnen wird dieser Newsletter nicht mehr geliefert</description>
			<name>newsletter $ name of object</name>
			<link>http://lukas-prokop.at/no-newsletter.cgi</link>
		</textInput>

		<item> <!-- RSS0.92: max 15 items; RSS2: infinity; all sub elements are optional!!! -->
			<title><![CDATA[Ein Title]]></title>
			<link>http://lukas-prokop.at/blog/2009/08/why-php-sucks.html</link>
			<description><![CDATA[<p>I explain why PHP sucks</p>]]></description>
			<author>lukas@prokop.at (Lukas Prokop)</author>
			<category domain="lukas-prokop.at">/articles/article/technology/php $ wieder unstandardisiert</category>
			<comments>http://lukas-prokop.at/blog/2009/08/why-php-sucks.html#add-comment</comments>
			<!-- attached media file -->
			<enclosure url="http://lukas-prokop.at/blog/media/chaosradio102.ogg" length="6234593" type="audio/ogg"></enclosure>
			<guid isPermalink="true">http://lukas-prokop.at/blog/2009/08/why-php-sucks.html</guid>
			<pubDate>Mon, 03 Aug 2009 21:43:30 +0000</pubDate>
			<source url="http://www.php.org/">PHP official Homepage</source>
		</item>
	</channel>
</rss>


.. [*] It specifies a web service that supports the rssCloud interface which can 
     be implemented in HTTP-POST, XML-RPC or SOAP 1.1. Its purpose is to allow 
	 processes to register with a cloud to be notified of updates to the channel, 
	 implementing a lightweight publish-subscribe protocol for RSS feeds.
	 
	 In this example, to request notification on the channel it appears in, 
	 you would send an XML-RPC message to rpc.sys.com on port 80, with a path 
	 of /RPC2. The procedure to call is myCloud.rssPleaseNotify.

iTunes Extension
----------------

<rss xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd" version="2.0">
<itunes:author>Harald Schmidt $ iTunes "Interpret"</itunes:author>
<itunes:block>yes $ shall the element item or channel be ignored?; "yes" or "no"</itunes:block> 
 <!-- see http://apple.com/de/itunes/store/podcaststechspecs.html -->
<itunes:category text="Technology">
	<itunes:category text="Websites">
	<itunes:category text="RSS">
</itunes:category>
<itunes:duration>5:40:33 $ 5 hours, 40 minutes, 33 seconds, values require only one number; "SS:MM:ss", "MM:SS" or "SS"</itunes:duration>
<itunes:explicit>yes $ censorship-tag, yes=show warning in title bar, clean=no "adult only"-content, 
	no=ignore content; yes no clean</itunes:explicit>
<!-- Albumcover, if it's missing, the RSS2-image-element will be used -->
<itunes:image href="http://google.at/logo.jpg"></itunes:image>
<itunes:keywords>Tech, Websitedevelopment, W3C</itunes:keywords>
<!-- max. twelve items -->
<itunes:new-feed-url>http://example.org/ $ only use it at channel-layer</itunes:new-feed-url>
<itunes:owner>
    <!-- only for Apple Inc., will not be published, subelement name required and email optional -->
	<itunes:name>Foobar Barfoo</itunes:name>
	<itunes:email>foobar@bar.org</itunes:email>
</itunes:owner>
<itunes:subtitle>Beschreibung $ short!, iTunes "Description"</itunes:subtitle>
<!--- if element summary is missing, iTunes uses the RSS2-description-item -->
<itunes:summary>A small description $ max 4000 chars, iTunes "Information"</itunes:summary>
<!-- important: pubDate in RSS2 must be in RFC 2822; especially when using iTunes -->

RSS 1.0 RDF
-----------

+-----------------------------------+---------------+
| XPath to element                  | maximal chars |
|                                   | characters or |
|                                   | RFC-standard  |
+===================================+===============+
| /rdf/channel/description          | 500           |
| /rdf/channel/item/description     | 500           |
| /rdf/channel/item/image/title     | 40            |
| /rdf/channel/item/                |               |
|   textinput/description           | 100           |
| /rdf/channel/item/textinput/name  | 500           |
| /rdf/channel/item/title           | 100           |
+-----------------------------------+---------------+

+----------------------------------+-------------+
| XPath to element                 | appearance  |
+==================================+=============+
| //[@rdf:*]                       | required    |
| /rdf/channel/item/description    | optional    |
| /rdf/channel/item/image          | optional    |
| /rdf/channel/item/textinput      | optional    |
+----------------------------------+-------------+

<rdf:RDF
	xmlns="http://purl.org/rss/1.0/" 
	xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns\#" 
	xmlns:dc="http://purl.org/dc/elements/1.1/"
	xmlns:sy="http://purl.org/rss1.0/modules/syndication/"
	xmlns:content="http://purl.org/rss/1.0/modules/content">
<!--
	Modules:
		* RDF (rdf)
		* Dublin Core (dc) (see http://dublincore.org/documents/1999/09/02/dces/)
		* Syndication (sy)
		* Textinput (ti)
		* Company (content)
	
	You can add any other modules to support better integration of 
	audio, video and podcasting files (and other things).
-->
<!--  is required; there are more than 30 optional sub-elements -->
<channel rdf:about="http://lukas-prokop.at/blog/feed.rss">
	<title>Lukas' Weblog</title>
	<description>A Weblog about my life and everything else</description>
	<!-- without any subelements -->
	<image rdf:resource="http://lukas-prokop.at/blog/me.jpg" />
	<!-- like RSS2's textinput, but is deprecated because robots should also be able to handle such stuff -->
	<textinput rdf:resource="http://lukas-prokop.at/blog/subscription.cgi" />
	<!-- begin syndication -->
	<sy:updatePeriod>hourly $ "daily", "weekly", "monthly" and "yearly"</sy:updatePeriod>
	<!-- number of updates per period -->
	<sy:updateFrequency>2</sy:updateFrequency>
	<!-- base date for calculating next update -->
	<sy:updateBase>1901-01-01T00:00+00:00</sy:updateBase>
	<!-- end syndication -->
	<!-- begin content -->
	<content:encoded rdf:resource="http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" />
	<!-- end content -->
	<items>
		<rdf:Seq>
			<!-- a permalink for each item -->
			<rdf:li resource="http://lukas-prokop.at/blog/why-php-sucks.html" />
			<rdf:li resource="http://lukas-prokop.at/blog/why-html-sucks.html" />
		</rdf:Seq>
	</items>
	<item rdf:about="http://lukas-prokop.at/blog/why-php-sucks.html">
		<title>Why PHP sucks</title>
		<link>http://lukas-prokop.at/blog/why-php-sucks.html $ like rdf:about</link>
		<description>article or a summary of the article (no HTML!)</description>
		<!-- DublinCore as example for more meta information -->
		<!-- begin Dublin Core -->
		<dc:subject>Copyleft 2009 by Lukas Prokop</dc:subject>
		<dc:creator>Lukas Prokop</dc:creator>
		<dc:date>2009-09-15T11:05:00+02:00</dc:date>
		<!-- end Dublin Core -->
		<image rdf:resource="http://lukas-prokop.at/blog/why-php-sucks.jpg">
			<title>Title Image $ like html's alt=""</title>
			<url>http://lukas-prokop.at/blog/why-php-sucks.jpg $ like rdf:resource</url>
			<link>http://lukas-prokop.at/blog/ $ link behind image</link>
		</image>
		<textinput rdf:resource="http://lukas-prokop.at/blog/subscription.cgi?p=why-php-sucks">
			<title>Subscribe $ title of submit button</title>
			<description>You like my article "Why PHP sucks"? Subscribe to my weblog $ What the submit button does</description>
			<name>A name to identify CGI Script</name>
			<link>http://lukas-prokop.at/blog/subscription.cgi $ like rdf:resource</link>
		</textinput>
	<item rdf:about="http://lukas-prokop.at/blog/why-html-sucks.html">
		<title>Why HTML sucks</title>
		<link>http://lukas-prokop.at/blog/why-html-sucks.html</link>
	</item>	
</channel>
</rdf>

Atom (RFC 4287)
---------------

<!--
	Publish atom-feeds with application/atom+xml
-->

+-----------------------------------+---------------+
| XPath to element                  | maximal chars |
|                                   | characters or |
|                                   | RFC-standard  |
+===================================+===============+
| /feed/entry/updated               | RFC 3339      |
+-----------------------------------+---------------+

+----------------------------------+-------------+------------------------+
| XPath to element                 | appearance  | condition              |
+==================================+=============+========================+
| /feed[@xmlns]                    | required    |                        |
| /feed/post                       | optional    |                        |
| /feed/author                     | optional    | each item-element      |
|                                  |             | contains an author     |
| /feed/author/email               | optional    |                        |
| /feed/author/uri                 | optional    |                        |
| /feed/contributor                | optional    | author is set          |
| /feed/contributor/email          | optional    |                        |
| /feed/contributor/uri            | optional    |                        |
| /feed/category                   | optional    |                        |
| /feed/category[@term]            | required    |                        |
| /feed/category[@^term]           | optional    |                        |
| /feed/generator[@version]        | optional    |                        |
| /feed/entry/title                | required    |                        |
| /feed/entry/summary              | required    | no content is set or   |
|                                  |             | content contains no    |
|                                  |             | Text, XML or HTML      |
| /feed/entry/summary[@url]        | optional    |                        |
| /feed/entry/summary[@url]        | required    | content must be empty  |
|                                  |             | summary is required    |
| /feed/entry/content[@type]       | optional    |                        |
+----------------------------------+-------------+------------------------+

<!-- attr version is not used any longer, but xmlns is part of Atom now -->
<feed xmlns="http://www.w3.org/2005/Atom">
	<title>Lukas' Weblog</title>
	<!-- the linked site must have a link back to the feed -->
	<link rel="alternate" type="text/html" href="http://lukas-prokop.at/blog/" />
	<!-- xml-file unspecified; introspection-tag one time or never -->
	<introspection href="http://lukas-prokop.at/blog/introspection.xml" />
	<!-- link to add entries to feed; not used with pure syndication formats -->
	<post href="http://lukas-prokop.at/" />
	<!-- the main author -->
	<author>
		<name>Lukas Prokop</name>
		<email>luk@example.org</email>
		<uri>http://lukas-prokop.at/</uri>
	</author>
	<contributor>
		<name>Toja</name>
	</contributor>
	<contributor>
		<name>foobar</name>
	</contributor>
	<category term="technology/php" scheme="http://lukas-prokop.at/cat/php" label="PHP" />
	<tagline>A weblog about my life and everything else</tagline>
	<id>http://lukas-prokop.at/blog/atom.xml</id>
	<generator uri="http://wordpress.org/" version="2.5">Wordpress</generator>
	<!-- Not for robots -->
	<copyright>Copyleft 2009 by Lukas Prokop</copyright>
	<!-- Not for robots -->
	<info>
		Der Feed bringt regemäßige Update von meinem Weblog.
		Nutze ihn um aktuelle Informationen zu bekommen.
	</info>
	<updated>2009-09-15T12:18:00+02:00 $ last update, RFC 3339</updated>
	
	<entry>
		<title>Why PHP sucks</title>
		<link rel="alternate" type="text/html" href="http://lukas-prokop.at/blog/permalink?q=why-php-sucks">
		<!-- <edit> is not useful for weblog-feeds -->
		<!-- other than the main author -->
		<author>FooBar</author>
		<!-- IP address of author; only for wikis -->
		<host>127.0.0.1</host>
		<contributor>BarBaz</contributor>
		<id>http://lukas-prokop.at/blog/permalink?q=why-php-sucks</id>
		<published>2009-09-15T12:48:26+02:00 $ datetime of publication; RFC 3339</published>
		<!-- overwrite <copyright> from <feed> -->
		<copyright>Copyleft 2009 BarBaz</copyright>
		<!--
			use attr url to add files (videos, audio, binary data, etc.)
				then content must be empty and summary is required
				do not link files with MIME-type: text/*+xml and include them directly in entry
		-->
		<summary>The reason why PHP sucks and not sucks</summary>
		<!--
			use attr type to set the MIME-type (per default: text/plain)
			entities in content:
				escape = > transform to &gt;
				according to spec, you have to escape all entities
				if attr mode="escaped": you do not have to escape entities (not spec-conform)
		-->
		<content type="text/html" mode="escaped">
		<![CDATA[
			<p>
			  Some might think that it is your personal point of view to support or rant PHP, 
			  but there are good reason for / against <b>PHP</b>.
			</p>
		]]>
		</content>
	</entry>
</feed>

Example files
-------------

Chaosradio_ and LukasWeblog_.

.. _Chaosradio: http://chaosradio.ccc.de/chaosradio-latest.rss
.. _LukasWeblog: http://lukas-prokop.at/blog/feed/