<http://schema.org/description>
"Have you ever wondered why you were shown specific apps or why Facebook was recommending you download one? Unless a friend prompted you to check it out (like those incessant Farmville ..."^^<http://www.w3.org/2001/XMLSchema#string>
<http://thenextweb.com/facebook/2012/10/03/facebook-app-center-recommendation-engine-explaine/>