RSS also plays a part in podcasting. The term podcasting originally came from a combination of Apple's iPod and broadcasting, but it has since come into its own, no iPod needed. Podcasts are recorded MP3 audio files usually disseminated over the Internet, and can be played on your computer or downloaded into an MP3 player.
Podcasts are based on RSS, and starting with RSS version 0.92, RSS can include enclosures. An enclosure for a podcast is simply the URL of a resource on the Internet. That resource doesn't have to be textit can be an audio recording or a video recording, for example.
That's how podcasts workan RSS file includes an enclosure, which points to an audio file or a video file. Both the RSS file and the audio/video podcast file must be online. To read podcasts, you can use special podcast software, like the Juice podcast receiver (Figure 1.6).
Figure 1.6. The Juice podcast receiver lets you read podcasts.
Podcast software reads the RSS feed file and determines from the enclosure where the podcast is located. Some podcast receiver programs automatically download a podcast, some wait until you request the download, and some let you choose when and how the download will occur.
In fact, more and more standard RSS readers support podcasts. In some RSS readers, for example, you'll see a small link to an enclosure at the end of an RSS item's text. Clicking that link will play the podcast. And a new development is the online podcast receiver, which lets you play podcasts as if you had downloaded podcast software to your computer.
For a look at how to create your own podcasts and then listen to them in podcast programs, turn to Chapter 7, "Podcasting: Adding Multimedia to Your Feeds."
A Brief History of RSS
Where did RSS come from? How long has it been around? RSS has had quite a history, some of which is shrouded in folklore, so I can't guarantee that my understanding of RSS history is 100 percent flawless. In fact, even what RSS stands for has changed over the years! There are three meanings for RSS and the version in which they were introduced:
Today, the most common meaning is Really Simple Syndication.
So where did the idea of syndicationsubscribing to a site's contentcome from? Long before RSS, there were various other formats (you couldn't quite call them languages) that supported syndications. You might recall Microsoft's Channel Definition Format (CDF), which worked with the Active Channel feature of Microsoft's Internet Explorer. Using CDF, you could subscribe to various online publication sites. Internet Explorer would check those publishers regularly and download new data as it became available. CDF was introduced in 1997, and in the same year, a developer at Userland.com, Dave Winer, introduced his own XML-based format for syndication in his Scripting News Web log. Userland.com, which first appeared in 1997, specializes in Web publishing software, and figures heavily in the history of RSS.
The first true version of RSS was created by Dan Libby of Netscape. Created in March 1999, it became known as version 0.90 (and was designed to be used with the My Netscape portal). In July 1999, version 0.90 was modified, and version 0.91, the first popular version, appeared. At that time, RSS stood for Rich Site Summary. Version 0.91 adopted parts of Dave Winer's Scripting News format and has become one of the major versions of RSS.
However, Netscape abandoned RSS not long after that, so although RSS was in some use, no one was in charge of it. Chaos resulted, as you might expect. Here's what happened: A mailing list named RSS-DEV appeared and became popular. At the same time, Dave Winer created a modified version of RSS 0.91, which was already being used in Userland's software.
Eventually, the approaches to RSS from the RSS-DEV group and Dave Winer diverged, creating what became known as the RSS fork. The RSS-DEV group created RSS 1.0 in December 2000. This version of RSS was quite a departure from the earlier versions, and was strongly based on the XML-based language Resource Description Format, or RDF (www.w3.org/TR/rdf-primer/), especially the RDF extension Dublin Core (http://dublincore.org/). Thus RSS 1.0 was named RDF Site Summary.
Only about three weeks after RSS 1.0 was announced, Dave Winer released RSS version 0.92. RSS 1.0 was also a major RSS version, but its syntax is so different from that of the other RSS fork people were used to, that many found it hard to use.
Then things got a little turbulent. In April 2001, Dave Winer came out with RSS 0.93, which was similar to version 0.92. A draft of version 0.94 appeared in August 2001, which removed the changes made in version 0.93 and made a few minor changes.
Finally, in September 2002, Dave Winer released a successor to version 0.92, which he called version 2.0, because the version 1.0 name was already taken. At this time, RSS started being known as Really Simple Syndication. (In fact, things were pretty turbulent then too, because a few versions of RSS 2.0 appeared; but things have now settled down.) RSS 2.0 extended RSS 0.92, adding ways for people to extend RSS on their own. RSS 2.0 has since become a major versionthe major versionof RSS.
In July 2003, Dave Winer passed ownership of RSS 2.0 to Harvard Law School's Berkman Center for Internet & Society (http://cyber.law.harvard.edu/home/), where he was working at the time. That move calmed things down quite a bit, and RSS 2.0 has been stable ever since.
Things are still happening with RSS. In January 2005, Sean B. Palmer and Christopher Schmidt released a draft of RSS 1.1, which simplifies the language somewhat. However, as of this writing, RSS 1.1 has not taken off. In November 2005, Microsoft proposed some extensions to RSS, informally named Real Simple Synchronization.
About five years ago, a number of developers, including Sam Ruby, offered a new format named Atom (first called Echo, then Pie, and then Atom) as a replacement for RSS. Atom is based on XML, but is quite a bit more difficult to learn and is more complex than RSS. Atom improves RSS by adding internationalization, standardizing the syntax, and allowing people to add their own features. Atom has yet to catch on in a really big way, however, compared with RSS.
So as you can see, RSS development is still going on, but the situation has stabilized. Today, versions 0.91, 1.0, and 2.0, as well as Atom, are in widespread use. These are the formats you'll see in this book.