<http://schema.org/description>
"If you've used services like foursquare that let you check-in to a location or leave tips, then you're familiar with the concept of leaving your digital mark on top of a geographic ..."^^<http://www.w3.org/2001/XMLSchema#string>
<http://thenextweb.com/apps/2011/11/21/skychalk-lets-you-leave-notes-on-a-map-anywhere-in-the-world/>