Content Syndication with RSS

Name

mod_changedpage

Synopsis

mod_changedpage does for RSS 1.0 what the cloud element does for RSS 0.9x — it introduces a form of Publish and Subscribe. We’ll discuss Publish and Subscribe in detail in Chapter 12, but basically it enables a system in which you can “subscribe” to a feed and be notified when something new is published.

mod_changedpage uses only one element, which points to a changedPage server. Users wishing to be told when the feed has updated send an HTTP POST request of a certain format to this server. Upon updating, this server sends a similar POST request back to the user. The user’s client then knows about the update. Again, Chapter 12 examines this in detail.

Namespace

mod_changedpage takes the namespace prefix cp: and is identified by the URI http://my.theinfo.org/changed/1.0/rss/. Hence, its declaration looks like this:

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
         xmlns="http://purl.org/rss/1.0/"  
         xmlns:cp="http://my.theinfo.org/changed/1.0/rss/">

Element

mod_changedpage takes only one element, a subelement of channel :

<cp:server rdf:resource="URL" />

The URL is the address of the changedPage server.

Example

Example 7-6. mod_changedpage in the channel

<?xml version="1.0" encoding="utf-8"?> 
   
<rdf:RDF  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
        xmlns=http://purl.org/rss/1.0/
          xmlns:cp="http://my.theinfo.org/changed/1.0/rss/" > <channel rdf:about="http://meerkat.oreillynet.com/?_fl=rss1.0"> <title>Meerkat</title> <link>http://meerkat.oreillynet.com</link> ...