What is RSS?

A lot has happened in the RSS world: Two new specifications have come out, RSS has become one of the most popular XML standards, and tools and feeds are popping up everywhere.

RSS is everywhere!

Today you can find tens of thousands of RSS feeds. Weblog users, news publishers, government agencies, and many personal and commercial Web sites support the format. Developer tools deal with RSS in Java technology, PERL, PHP, Python, and other major programming languages. Many viewers and aggregators work on the Web, on the desktop, even within e-mail clients. RSS has become the de facto standard for syndicating content and metadata over the Internet.

This article will review the current specification, RSS 2.0. I'll skip the discussion of the colorful characters and controversies surrounding the format -- that wouldn't leave room for much else.

Instead, this article will give you a little background, review how the format is being used, and drop the names of some of the more popular tools for working with it. It will review the nuts and bolts of the format, give you examples, and tell you what you need to know to get started. Finally, it will cover some of the new features of RSS 2.0, such as extending RSS using namespaces. At the end of the article, you'll find the mother lode -- a gargantuan annotated list of RSS resources.

What is RSS?

RSS is a format for syndicating content and metadata over the Internet. It is commonly used to share headlines and links to news articles. With news articles, the actual article isn't usually shared, but metadata about the article is; this metadata can include a headline, a URL, or a summary. RSS is an important tool for publishers because feeds can be used to syndicate content, and to integrate third-party content into your site.

RSS is a dialect of XML. All RSS files must conform to the XML 1.0 specification, as published on the World Wide Web Consortium (W3C) Web site.

Here's a typical example of how RSS is used:

A publisher has some content that they want to publicize.
They create an RSS channel for their content.
In this channel, they include items for Web pages they want to promote.
This channel can be read by remote applications, and converted to headlines and links. These links can be incorporated into new Web pages, or read in dedicated readers.
People see the links on various sites, click on them, and go to the original publisher's site.
While headline syndication is the most common use for RSS, it is also used for many other purposes. RSS is a very popular format in the weblog community. It's also used for photo diaries, classified ad listings, recipes, reviews, and for tracking the status of software packages.

RSS feeds are used in the world of e-commerce as a way of delivering information. For example, Amazon provides custom news feeds based on its Web services platform. This lets you track top books in your news reader, or include information on your Web site about related books for sale at Amazon.

RSS has grown tremendously in popularity in the last few years. Syndic8.com maintains an index of RSS channels, and its list of feeds has grown by about 1400% in two years. Yahoo news, the BBC, Slashdot, LockerGnome, Amazon, CNN, Wired, Rolling Stone, and Apple Computer are among the many popular sources of RSS feeds