Have you observed websites lately? There is a new link with an orange rectangle optionally with the letters XML or RSS . These rectangles lead you to a new world of information, where you are always updated.

RSS is the abbreviation of these words Rich Site Summary, RDF Site Summary (RDF stands for Resource Description Framework), and Really Simple Syndication which are often interchangeably used. But in fat, RSS is an XML-based format for sharing and distributing web content, such as news headlines. Using an RSS reader, you can view data feeds from various news sources, such as Reuters, CNN, BBC and Jang including headlines, summaries, and links to full stories. But it's not just for news. Pretty much anything that can be broken down into discrete items can be syndicated via RSS, for instance, an update in a webpage, a change log of CVS checkins, or even the revision history of a book. Once information about each item is in RSS format, an RSS-aware program can check the feed for changes and react to the changes in an appropriate way. The technology of RSS allows internet users to subscribe to websites that have provided RSS feeds; these are typically the sites that change or add contents regularly. To use this technology, site owners create or obtain specialized software (such as a content management system) which, in the machine-readable XML format (called an RSS feed, webfeed, RSS stream, or RSS channel) presents new articles in a list, giving a line or two of each article and a link to the full article or post. Unlike subscriptions to many printed newspapers and magazines, most RSS subscriptions are free. In addition to facilitating syndication, RSS allows a website's frequent readers to track updates on the site using an aggregator.

RSS-aware programs are called news aggregators or feed reader. A news aggregator can help you keep up to date with all your favorite weblogs by checking their RSS feeds and displaying new items from each of them. It checks RSS-enabled web pages on behalf of a user and display any updated articles that it finds. It is now common to find RSS feeds on major web sites, as well as many smaller ones. Recent browsers have a built-in support of this aggregator software. But the current version of Internet Explorer does not support RSS. Microsoft is planning to integrate this into IE7 which is expected to hit market with Windows Vista in late 2006. The biggest rival of IE, Mozilla FireFox has this feature in its latest version i.e. FireFox 1.5.

What is the RSS history?

RSS is not a new idea. Before RSS several similar formats already existed for syndication, but none achieved widespread popularity. For example, in 1997 Microsoft created Channel Definition Format for the Active Channel feature of Internet Explorer 4.0, which became mildly popular. Dave Winer also designed his own XML syndication format for use on his Scripting News weblog, which was also introduced in 1997.

RDF Site Summary, the first version of RSS, was created by Dan Libby of Netscape in March 1999 for use on the My Netscape portal. This version became known as RSS 0.9. In July 1999, responding to comments and suggestions, Libby produced a prototype tentatively named RSS 0.91 (RSS now standing for Rich Site Summary), that simplified the format and incorporated parts of Winer's Scripting News format. And then with the passage of time, different people and different organization introduced enhancements and newer versions of RSS like RSS 1.0 and RSS 2.0.

What does RSS look like?

Imagine you want to write a program that reads RSS feeds, so that you can publish headlines on your site, build your own portal or homegrown news aggregator, or whatever. What does an RSS feed look like? That depends on which version of RSS you're talking about. Here's a very simple RSS 0.91 feed:

<rss version="0.91">
<channel>
<title>XML.com</title>
<link>http://www.xml.com/</link>
<description>XML.com features a rich mix of information and services for the XML community.</description>
<language>en-us</language>
<item>
<title>Normalizing XML, Part 2</title>
<link>http://www.xml.com/pub/a/2002/12/04/normalizing.html</link>
<description>In this second and final look at applying relational normalization techniques to W3C XML Schema data modeling, Will Provost discusses when not to normalize, the scope of uniqueness and the fourth and fifth normal forms.</description>
</item>
</channel>
</rss>

A feed comprises a channel, which has a title, link, description, and (optional) language, followed by a series of items, each of which will have a title, link, and description. Keep it in your mind that there would be a difference between RSS 0.91, RSS 1.0 and RSS 2.0 feed. We can simply treat all as XML and write a single function to extract information out of either an RSS feed. However, there are some significant differences that our coder will need to be aware of.

The writer is a pedagogue, evangelist and IT professional. He holds M.S. degree from Sweden. He has worked on variety of software at positions ranging from project manager to software engineer. He has taught at various universities of Pakistan as well. Right now he is working in the COMSATS Institute of Information Technology, Islamabad.

He can be reached at atif_mashkoor@comsats.edu.pk.