On Friday, June 24, 2005, Microsoft announced that it was adding deep platform support for a technology called RSS to Longhorn. RSS, or Real Simple Syndication, is an XML data format that's used to publish Web content to which people can subscribe. RSS solves a problem that Microsoft and Netscape tried to solve a decade ago with so-called "push" technologies: Rather than force people to manually navigate to Web sites to see when content has been updated, they should be able to subscribe to that content and receive notifications when updates are made.

RSS today

Today, RSS is a niche technology used largely by blogs (such as at my personal blog, Internet Nexus). However, mainstream media is starting to realize the potential of RSS as well. This site now sports an RSS feed and media outlets such as The New York Times, CNN, and the BBC all feature RSS capabilities as well. As an XML data format, RSS itself isn't terribly interesting to human beings. But because it's an open standard and has been adopted worldwide, content that's distributed with RSS is increasingly valuable. And once the norms get their hands on it, RSS will be indispensable, though invisible, kind of like electricity.

Today, most people subscribe to RSS feeds with something called a news aggregator. There are three basic types of news aggregators: Standalone news aggregator clients, email plug-ins, and Web browser plug-ins.

Some People like news aggregators that work from within email clients because RSS lends itself well to the email metaphor, where you have articles (email messages) with titles (subject lines). The best news aggregator of this type is called Greg Reinacker's NewsGator, which is a distributed as a plug-in for Microsoft Office.

Others believe that RSS should be consumed inside a Web browser, because that's where users already read Web content. Those people are probably correct. As nice as NewsGator is, it seems to me that the future of Web content will remain inside the Web browser. Today, the best implementation of a Web browser-based RSS client is the version of Safari (Figure) that Apple includes with Mac OS X 10.4 "Tiger" (see my review). Safari RSS is, in my opinion, the single best RSS client available anywhere.

Microsoft takes the plunge

Microsoft, like Apple, will extend its Web browser--in this case, Internet Explorer (IE)--to be an RSS client. More specifically, Microsoft will be adding RSS subscription features to IE 7, which is due in beta form this summer for Windows XP users, and will ship as part of Longhorn in late 2006. "Like Web searching, RSS is an additive, not a replacement, for Web browsing," Gary Schare, the director of product management for the Windows group at Microsoft told me during a pre-announcement briefing last week." Web searching doesn't replace browsing, and neither does [RSS] subscribing. But it will develop into a key way for people to use the Web."

In Longhorn, and in Windows XP with IE 7, users will have an easy way to discover, view, and subscribe to RSS feeds. These features will all be available thanks to IE 7's RSS capabilities.

However, Microsoft's support of RSS is going far deeper than a Web browser. In Longhorn, Microsoft will integrate RSS directly into the operating system via a set of APIs (application programming interfaces). "We're going to provide developers with the ability to incorporate the rich capabilities of RSS into their applications," Schare told me. "Those applications will go well beyond applications that do RSS today, like news aggregators and media players. With this API support, any application will be able to integrate with RSS. Developers won't need to know how [the details of making it work]. Windows [Longhorn] will do that for them."

Additionally, Microsoft is publishing a new and open set of extensions to RSS called Simple List Extensions that will enable RSS content providers--that is, Web sites and the like--to create RSS-based lists, a capability that was previously impossible under the existing RSS specification. Amazingly, Microsoft is licensing Simple List Extensions for free via the same Creative Commons license by which RSS is licensed.

OK, let's take a look at each of these developments in a bit more depth.

RSS support in IE 7

The notion of RSS support in IE 7 is pretty well understood, but what does this all look like? In IE 7, users will discover RSS feeds when an icon in the toolbar lights up, indicating that a syndicated version of the current site is available. When you click on that icon, you will be provided with a pretty view of the feed, a la Safari. You can then subscribe to the feed. Subscribed RSS feeds appear in IE 7's Favorites menu, which is the way other browsers--including Safari and Mozilla Firefox--handle it.

Here's what the IE 7 Subscribe toolbar button will look like:

RSS support in Longhorn

Longhorn's support of RSS is deep and broad. In addition to the APIs mentioned above, that operating system will include the following RSS-related technologies:

Common RSS Feed List. This "core" feature of Windows will maintain a system-wide list of the user's RSS subscriptions. This list will be accessible via any RSS-aware application. That means that, regardless of how you subscribe to an RSS feed, it will be available via any application or service that supports RSS.

Common RSS Data Store. The data store is a database that contains the content from subscribed RSS feeds. Any application that accesses Longhorn's RSS APIs will be able to access this content, which can include text, pictures, audio, calendar events, documents and just about anything else, according to Microsoft. Users can utilize the built-in features in IE 7 to view RSS content, or find a richer experience in a third party application if they'd like.

RSS Platform Sync Engine. The sync engine is a service that runs in the background and automatically downloads RSS content on predefined schedules. The sync engine will efficiently use idle network bandwidth whenever possible, Microsoft says, limiting the performance impact. Naturally, any application that takes advantage of Longhorn's RSS support won't have to deal with the implementation details of scheduling and downloading RSS content.

Microsoft's RSS extensions

If you've ever spent any time with MSN Spaces (see my review), Microsoft's blog solution, you're familiar with lists. Many Web sites need to maintain lists, for such things as Top 10 lists, retailer wish lists, and the like. The problem is that RSS isn't designed to handle that kind of content. Instead, RSS uses more of a first-in, first-out type of system where only the newest content (and not the highest rated, or whatever) is automatically bubbled to the top. In short, RSS is time-based.

Microsoft's Simple List Extensions seek to solve this problem. An open set of enhancements to RSS, the Simple List Extensions provide two basic improvements. First, they allow RSS to capture information that is stored in a list. So, for example, when an item in a list changes position or is removed, the list can be updated. Second, Simple List Extensions allow RSS content providers to include information about each item in a list with that item. So a Top 10 song list might include such additional information as artist name, date of release, album name, and so on. The lists can then be sort by this additional information.

Given Microsoft's reputation, you may be surprised to discover that Simple List Extensions have been positively received across the board. Major online retailers like Amazon intend to support the extensions in its Amazon Web Services. And Microsoft has even received praise from former critics, such as Lawrence Lessig, the copyright expert who founded the Creative Commons under which RSS (and Simple List Extensions) are licensed. "We salute Microsoft's decision to license its Simple List Extensions via Creative Commons, which offers creators a way to both protect their work and to encourage broad uses of them," Lessig said. "Microsoft?s flexibility with its intellectual property will positively impact a wide range of content publishers and the RSS community as a whole."

How and when

One of the most obvious questions about all this is, when will end users and developers be able to take a look at this technology? This summer, Microsoft will ship a Beta 1 release of IE 7, and that release will include the RSS discover, view, and subscribe functionality. Longhorn Beta 1, due in July, will not include any RSS functionality, however. For access to the RSS APIs and other features, developers will need to wait for the PDC 2005 build, which is due in September.