The Triumph of RSS
By Ayesha Khanna

From blogging to audio blogging (popularized as podcasting) to video blogging, the Web has allowed everyone to become publishers, radio DJs and TV personalities to a seemingly infinite audience. The technology underlying the ability of podcasting is RSS or Really Simple Syndication, which allows content producers to describe their content in XML tags and allows users to subscribe to this content. The word podcasting comes originally from the ubiquitous iPod, but it can be downloaded to any computer. As iPods now incorporate videos in them as well, the future of podcasting is full of potential, from downloading streaming audio video content, to live streams the day iPods can be connected to the Web via wireless connections.

SYNDICATION

RSS allows web syndication, but what does that really mean? When Oprah Winfrey got national syndication, she effectively became a multimillionaire. It meant that television stations across the USA bought the license to The Oprah Winfrey Show to allow them to show it in their local constituencies. So syndication is the right and ability to get and display content produced by someone else. In the case of the Web, it means subscribing to a particular part or whole of the content of the Web. Usually, only a headline or summary of the content is syndicated, which means that if the user wants to see more of the content, he or she clicks on the link which takes the reader to the publisher's website. Web syndication has, therefore, usually been free. What started out as news headline syndication moved to blog syndication and now to audio and video syndication, increasing the visibility of each media content. There are many tools you can buy to create and subscribe to these feeds, each relying on RSS as the backbone content capture mechanism.

RSS

RSS allows subscribers to see some or all of the content on a web site, without having to visit that site. For content providers, this not only increases their visibility, but also drives traffic to their site when viewers who are interested in the summary description choose to see more of it. Over the years, it has become the main vehicle for streaming content to different sites.

RSS is from the XML-based format. There are four main concepts to remember for RSS:
1. Each RSS file is known as an RSS channel or feed
2. The RSS channel contains a list of items.
3. Each item contains a title, link and description. The channel itself also has a title, link and description associated with it.

The three elements: title, link and description are mandatory items, i.e. the file will not validate if these three elements are not present. However, RSS 2.0 provides many other optional elements as well, which can be used to add further metadata information to the content..

For mandatory and optional items, look at Harvard University’s blog on RSS. Examples of optional elements under channel include language, copyright and pubDate. Similarly, an item can also contain optional elements such as author and category. Apart from items, sub-elements of channel may also be image and textInput, which can be used to link to images and texts respectively.

Thus, by using simple XML tags, you can effectively describe your channel, and also the content that you want to allow to display on anyone who may use the RSS document.

Note that you can also extend RSS, just as you can extend an XML ontology, by specifying a particular namespace. You will see you this is relevant later when see how iTunes extended RSS to add in its own tags which allow your podcasts to be downloaded by iTunes.

PRODUCING THE FILE

There are three ways to create an RSS file: using a software language such as Java or a scripting language to parse a document and enclose its content appropriately in XML tags, such as Author; using a tool such as Dreamweaver, which automatically creates an RSS XML document everytime you create a Web page; or hosting your site with a service which will automatically create it for you. Most companies that host blogs provide automatic creation of RSS feeds based on metadata that they gather through their content management systems, which separates author, publication date, title, excerpt and description. Movable Type 3.2 is the content management system used by AyeshaKaljuvee.com and it automatically generates the RSS feed for anyone who may want to subscribe to the site’s content.

CONSUMING THE FILE

Consuming a RSS file requires an RSS feed reader. There are two kinds of feed readers: Web-based feed readers, such as Bloglines, and those that can be installed on your computer, such as NewsGator. Bloglines allows you to open an account and then subscribe to any feeds you like by typing in the URL of the the site. That's it! From now, every time you log in, you’ll regularly see updated content from those sites. The feed goes regularly to the sites you’ve chosen to check for updates and updates the content it displays on your reader. Bloglines is specific for blogs, but is essentially the same flavor as a news aggregator. Note that unless you’ve allowed all your content to be fed in the RSS, only the summary will be displayed and then you will have to click on the link to go to the site.

If you want to put another site’s RSS feed on your server, then you will have to install the software on your computer, parse the incoming RSS feed and display it on your site using XSLT.

PUSH vs. PULL

There are two ways to publish and subscribe to feeds: either the RSS feeder that subscribes to your site will ping your site regularly to check for updates, or you as the publisher will ping the subscriber to let him or her know that you’ve updated your site. In other words, the subscriber can either be pushed the data or pull the data.

Some blogs, such as those offered by Six Apart which include Movable Type content management system, are automatically configured to ping sites, such as Technocrati. So when I set up AyeshaKaljuvee.com, I could choose to agree to have updates pinged to Techocrati and everytime I save a new entry, Technocrati is then informed of it.

You can also use sites such as Pingomatic to ping different blog aggregators about your blog. You can check if your blog validates by using a validator such as Feed Validator, which is recommended by Yahoo. Once you ping an aggregator, software on that server comes to your site, picks up the XML RSS file, and parses it to display on the other site.

MOVING BEYOND TEXT FEEDS

News feeds and blog feeds have been around for several years now. 2005 was the year when audio and video feeds began to gain prominence. It all began with the concept of podcasting. The great thing about these feeds is that the infrastructure already existed to publish and subscribe feeds.

There are two obvious ways of getting audio/video feeds:
* A link is sent in the feed, just as a link to the URL of an article is sent. The subscriber then can go that site and play and download the song.
* The audio/video comes automatically as an attachment, just as the text in the description element. In other words, it becomes one of the pieces of content that the publisher is willing to provide directly to subscribers.

The former could be done just using the basic RSS structure, but for the latter, a new element type was added to RSS called Enclosure Types, which allowed RSS to carry an audio or video mp3 as an attachment. This content would download automatically to your computer, and then could be transferred to any mp3 player, including the iPod.

The enclosure tag has three required attributes: url [where the enclosure is located], length [how big it is in bytes], and type [what its type is, a standard MIME type].

<enclosure url="http://www.ayeshakaljuvee.com/mp3s/ayeshakPodcast.mp3" length="14317820" type="audio/mpeg" />

Just like you need a news feed reader, in the same way, you need an audio or video podreader. You can use an online audio aggregator online or install podcatchers such as iTunes and subscribe via these readers. Note that in order to create an RSS feed that can be read by iTunes, you have to use the RSS extensions that have are part of the iTunes specification.

THE NEXT OBVIOUS QUESTION: RANKING & SEARCHING

Enter Google. With Google Video is one of the initiatives of Google Lab, which displays videos, allows searches [by directing users to upload videos to add metatags describing the content], and ranking them by popularity. Traditionally, audio/video content has been very hard to search given that it was obfuscated by tools such as Flash. However, with metatags using RSS and its extensions, it is possible to provide descriptive information about each video, allowing users to search according to their preferences.

CONCLUSION

Clearly as the technology takes off, you don’t need to know any of the plumbing, and you shouldn’t have to. However, this article describes precisely that plumbing for those who are interested, and shows how the key to syndication on the Web has been the RSS specification and the extensibility that it allows.

LINKS

* RSS Specifications
* An introduction to RSS Feeds by James Lewin.

Image courtesy Apple iPod