<http://schema.org/interactionType>
"http://schema.org/CommentAction"^^<http://www.w3.org/2001/XMLSchema#string>
<http://thenextweb.com/google/2013/07/31/google-sending-out-invites-to-let-glass-explorers-invite-a-friend-to-join-the-program/googleglassinvite/>