Mining Google Web Services: Building Applications with the Google API
A Rich Site Summary (RSS) feed is a kind of publishing service. A Web site that wants to make all or part of its content generally available to the public finds an RSS publisher. Users subscribe to this RSS publisher when they want to receive certain types of information. The information often appears on Web sites as part of a headline news feature. Most vendors use this kind of information publication for news, events, headlines, project updates, discussion group excerpts, and even corporate news.
Google doesn't provide RSS feeds directly, but a number of third party developers do. For example, you can obtain RSS feeds of the latest Google news using the Google News RSS Feeds located at http://googlenews.74d.com/. These feeds are updated every 15 minutes and make you aware of new information on the Google News Service. You could couple such a feed with Google Web Services to provide a full-featured description of the latest events as part of your application. To use the RSS feed all you need to do is load an URL, such as http://googlenews.74d.com/rss/google_world.rss for world news, into an XML document.
Once the document loads into the local document, you can parse it into any form needed for your application. The data adheres to a standard format that includes a description of the RSS feed, as well as individual items that describe the content you'll find in the Google New site. Figure C.1 shows a typical example of the output for the world news site.
The problem with RSS feeds is that it normally requires special software to use or at least an understanding of XML to create your own RSS reader software. You can find a number of RSS readers on the Internet. For example, the intraVnews reader found at http://www.intravnews.com/ integrates with Microsoft Outlook. In fact, you can find a lengthy list of RSS readers at http://directory.google.com/Top/Reference/Libraries/Library_and_Information_Science/Technical_Services/Cataloguing/Metadata/RDF/Applications/RSS/News_Readers/.
Don't get the idea that RSS feeds have to be limited to the Google News Service. For example, the d2r site at http://www.dynamicobjects.com/d2r/archives/002304.html discusses how the author created an RSS feed based on Google Web Services and a query. You can actually use this RSS feed to monitor changes to the query result so you can detect new links as they appear. Another such RSS service is Google.rss at http://rajivraj.europe.webmatrixhosting.net/google/googlerss.html.