The RSS (define) syndication format has spread like wildfire through the Internet, permeating most news sites and virtually all blogs. Now there's a new aspect of RSS ready to enjoy the same popularity. Called RSS enclosures, they're the next step in the RSS revolution and hold great potential.

One of the uses of enclosures is "podcasting," a name that is derived from Apple's iPod, though the technology can be utilized on any MP3-capable device. The RSS enclosure feature allows for the syndicated XML (define) feed to not just serve text content, but also to package an enclosure (call it an attachment of some sort), as well. In the podcasting model, the RSS enclosure contains an audio file, which subscribers can listen to on their devices.

There are many tools and services that support podcasting, such as iPodder and BlogMatrix Jaeger, with the number increasing almost daily.

BlogMatrix bills itself as a "'one-panel'" weblog reader and podcast receiver for Windows, Macintosh OS 10.3 and Linux." According to BlogMatrix spokesman David Janes, the application has more than 10,000 downloads, though he admits that he doesn't know how many are actually using the podcast reception features.

"Podcasting is a very young niche: as a gerund, it's less than six months old," Janes told internetnews.com. "The use model is still evolving in much the same way Web browsers changed in the early to mid 90s; lots of ideas will be tried and lots of ideas will be discarded."

Another podcasting conduit is hosted blogging service Blogharbor. According to spokesman John Keegan, there isn't enough statistical information to accurately draw conclusions about the demographic of podcasters.

"Despite the welcome media attention to the podcasting phenomenon, there are probably fewer than a thousand Internet users podcasting at this point in time," Keegan told internetnews.com. "It's probably too early to predict the demographic of the next 10,000 users, though we can safely say they will likely be technically savvy users who are already blogging."

Keegan explained that the enclosure attribute of RSS has actually been around for a while, and was first implemented in RSS 0.92, which was released in December 2000. The iPodder concept is merely the first application based on RSS enclosures to capture the imagination of users and developers.

Indeed, podcasting is only one potential use of RSS enclosures. According to RSS advocate Jeremy Zawodny, anyone using RSS to distribute information can potentially make use of enclosures.

A company using an RSS feed for a newsletter could also include a promotional video clip as an enclosure in the feed. The software industry, he said, could use them as a method to inform and deliver software updates.

"They could ship an application that fetches the latest news via an RSS feed that may contain the updates as an enclosure," Zawodny told internetnews.com. "The benefit is that a traditional RSS reader could also suck in the content, but the real application could perform an automatic upgrade as well."

Blogharbor's Keegan sees a second wave of enclosure-based applications based on sharing and syndicating photos and digital images.

"We expect developers to pick up on this concept and begin creating applications for sharing and aggregating digital images," Keegan said. "That is almost certainly going to be the next set of killer apps based on RSS enclosures."

Podcasting hype aside, RSS enclosures represent another step in the evolution of content syndication.

"To me enclosures are more evolutionary that revolutionary," Zawodny said. "RSS is a reasonably flexible format for distributing content. Enclosures are to RSS what attachments are to e-mail. We have to be careful not to go overboard with either one."