Earlier this week, there were a flurry  of blog posts about the announcement of the Facebook platform. I've taken a look at the platform and it does seem worthy of the praise that has been heaped on it thus far.  

What Facebook has announced is their own version of a widget platform. However whereas most social networking sites like MySpace, Bebo and Windows Live Spaces treat widgets as second class citizen that exist within some tiny box on the user's profile page, widgets hosted on Facebook are allowed to deeply integrate into the user experience. The page Anatomy of a Facebook Application shows ten integration points for hosted widgets including integration into the left nav, showing up in the users news feed and adding themselves as action links within the user's profile. This is less of a widgts platform and more like the kind of plug-in architecture you see in Visual Studio, Microsoft Office or the Firefox extension infrastructure. This is an unprecedented level of integration into a Web site being offered to third party developers by Facebook. 

Widgets for the Facebook platform have to be written in a proprietary markup language called Facebook Markup Language (FBML). The markup language is a collection of "safe" HTML tags like blockquote and table, and custom Facebook-only tags like fb:create-button, fb:friend-selector and fb:if-is-friends-with-viewer. The most interesting tag I saw was fb:silverlight which is currently undocumented but probably does something similar to fb:swf. Besides restricting HTML to a "safe" set of tags there are a number of other security measures such as disallowing event handlers like onclick, stripping Javascript from CSS style attributes and requesting images referenced in FBML via their proxy server so Web bugs from 3rd party applications can't track their users.

Facebook widgets can access user data by using either the Facebook REST API or Facebook Query Language (FQL) which is a SQL-like query language for making requests from the API for developers who think constructing RESTful requests is too cumbersome.

Color me impressed. It is clear the folks at Facebook are brilliant on several levels. Not only have they built a killer social software application but they've also pulled off one of the best platform plays I've seen on the Web yet. Kudos all around.