Facebook took a step today to increase the cross-pollination between the more than 40,000 social apps built on top of its platform. Those apps are written in Facebook Markup Language (FBML, it is Facebook’s version of HTML). FBML has something called “tags” which call up Facebook content inside each app. Now app developers can add “custom tags” to expose their own content to other app developers, and thus spread it programmatically. Some examples include adding playlists from iLike to other apps, a badge from Causes, or a list of the most popular books from Visual Bookshelf.
The Facebook Blog has more details:
If you’ve built an application with a lot of rich content, and you want to extend its reach and share that content with other Platform applications, create some custom tags and share this content with the community. Custom tags are easy to use and are a great way for you to extend your application’s distribution.
There is no need for app developers to reinvent the wheel if other apps have already gathered great content and data that can be used in an existing app. For instance, if music isn’t central to an app, why not just add it from iLike? It might make iLike more popular, but it also lets other developers piggyback on all the work that iLike’s has already done. And by presenting iLike’s playlists in a new context, maybe mixed and matched with elements from other apps, in the end you have a whole new app.